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Cells
By: Breanna Oquendo, Kitty Katrina I. Timbers,
Anna Huffman, and Kaylon Kennedy
*Word will be defined again in a later chapter
Vocab
• Light microscope (LM)-an optical instrument with lenses that
refract (bend) visible light to magnify images of specimens
• Electron microscope (EM)-a microscope that uses magnets to
focus an electron beam on or through a specimen, resulting in
resolving power a thousandfold greater than that of a light
microscope (2 types: scanning and transmission)
• Scanning electron microscope (SEM)-a microscope that uses an
electron beam to scan the surface of a sample to study details of its
topography; used to study the fine details of cell surfaces
• Transmission electron microscope (TEM)-a microscope that
passes an electron beam through very thin sections and is used to study
the internal ultrastructure of cells
• Cell fractionation-the disruption of a cell and separation of its parts
by centrifugation
• Organelle-any of several membrane-enclosed structures with
specialized functions, suspended in the cytosol of eukaryotic cells
• Cytosol-the semifluid portion of the cytoplasm
• Cytoplasm-the contents of the cell, exclusive of the nucleus and
bounded by the plasma membrane
• Plasma membrane-the membrane at the boundary of every cell that
acts as a selective barrier, regulating the cell’s chemical composition
• Ribosomes-a complex of rRNA and protein molecules that
functions as a site of protein synthesis in the cytoplasm; consists of a
large and a small subunit. (In eukaryotic cells, each subunit is
assembled in the nucleolus)
• Nucleoid-a dense region of DNA in a prokaryotic cell
• Nucleus-the chromosome-containing organelle of a eukaryotic cell
• Nuclear envelope-the double membrane in a eukaryotic cell that
encloses the nucleus, separating it from the cytoplasm
• Nuclear lamina-a netlike array of protein filaments lining the inner
surface of the nuclear envelope; it helps maintain the shape of the
nucleus
• Nucleolus-a specialized structure in the nucleus, consisting of
chromatin regions containing ribosomal RNA genes along with
ribosomal proteins imported from the cytoplasmic site of rRNA
synthesis and subunit assembly
• Endoplasmic reticulum (ER)-an extensive membranous network in
eukaryotic cells, continuous with the outer nuclear membrane and
composed of ribosome-studded (rough) and ribosome-free (smooth)
regions
• Smooth ER-that portion of the endoplasmic reticulum that is free of
ribosomes
• Rough ER-that portion of the endoplasmic reticulum studded with
ribosomes
• *Glycoproteins-a protein with one or more carbohydrates
covalently attached to it
• Vesicles-sacs made of membrane in the cytoplasm
• Transport vesicle-a tiny membranous sac in a cell’s cytoplasm
carrying molecules produced by the cell
• Food vacuoles-membranous sacs formed by phagocytosis of
microorganisms or particles to be used as food by the cell
• Contractile vacuole-a membranous sac that helps move excess
water out of certain freshwater protists
• Central vacuole-a membranous sac in a mature plant cell with
diverse roles in reproduction, growth, and development
• Endomembrane system-the collection of membranes inside and
around a eukaryotic cell, related either through direct physical contact
or by the transfer of membranous vesicles; includes the smooth and
rough endoplasmic reticulum, the Golgi apparatus, lysosomes, and
vacuoles
• Eukaryotic cell-a type of cell with a membrane-enclosed nucleus
and membrane-enclosed organelles. Organisms with eukaryotic cells
(protists, plants fungi and animals) are called eukaryotes.
• Prokaryotic cell-a type of cell lacking a membrane-enclosed
nucleus and membrane-enclosed organelles. Organisms with
prokaryotic cells (bacteria and archaea) are called prokaryotes
• *Chromosomes- a cellular structure carrying genetic material,
found in the nucleus of eukaryotic cells; consists of one very long DNA
molecule and associated proteins (A bacterial chromosome consists of a
single circular DNA molecule and associated proteins and is found in
the nucleoid region)
• *Chromatin-the complex of DNA and protein that makes
up a eukaryotic chromosome (dispersed form, which occurs
when the cell is not dividing, is a mass of very long, thin fibers
that are not visible with a light microscope)
• Golgi apparatus-an organelle in eukaryotic cells consisting
of stacks of flat membranous sacs that modify, store, and route
products of the endoplasmic reticulum and synthesize some
products, notably non-cellulose carbohydrates
• Lysosome-a membrane-enclosed sac of hydrolytic enzymes
found in the cytoplasm of animal cells and some protists
• *Phagocytosis- a type of endocytosis in which large
particulate substances are taken up by a cell. It is carried out
by some protists and by certain immune cells of animals
• Mitochondrion-an organelle in eukaryotic cells that serves as thee
site of cellular respiration
• Chloroplast-an organelle found in plants and photosynthetic protists
that absorbs sunlight and uses it to drive the synthesis of organic
compounds from carbon dioxide and water
• Peroxisome-an organelle containing enzymes that transfer hydrogen
from various substrates to oxygen, producing and then degrading
hydrogen peroxide
• Crista-an infolding of the inner membrane of a mitochondrion that
houses electron transport chains and molecules of the enzyme
catalyzing the synthesis of ATP (ATP synthase)
• Mitochondrial matrix-the compartment of the mitochondrion
enclosed by the inner membrane and containing enzymes and
substances for the citric acid cycle
• Plastids-one of a family of closely related organelles that includes
chloroplasts, chromoplasts, and amyloplasts (leucoplasts) (found in
cells of photosynthetic organisms)
• Thylakoids-flattened membranous sacs inside a chloroplast that
exist in an interconnected system (contain the molecular “machinery”
used to convert light energy to chemical energy)
• Granum-a stack of membrane-bound thylakoids in the chloroplasts
that function in the light reactions of photosynthesis
• Stroma-within the chloroplast, the dense fluid of the chloroplast
surrounding the thylakoid membrane; involved in the synthesis of
organic molecules from carbon dioxide and water
• Cytoskeleton-a network of microtubules, microfilaments, and
intermediate filaments that branch throughout the cytoplasm and serve
a variety of mechanical, transport, and signaling functions
• Motor proteins-proteins that interact with cytoskeletal elements and
other cell components, producing movement of the whole cell or parts
of the cell
• Microtubules-hollow rods composed of tubulin proteins that make
up part of the cytoskeleton in all eukaryotic cells and are found in cilia
and flagella
• *Centrosome-structure made of two centrioles present in the
cytoplasm of animal cells, important during cell division; functions as a
microtubule-organizing center
• Centriole-a structure in the centrosome of an animal cell composed
of a cylinder of microtubule triplets arranged in a 9 + 0 pattern
• Flagellum-a long cellular appendage specialized for locomotion.
Like motile cilia, eukaryotic flagella have a core with nine outer
doublet microtubules and two inner single microtubules ensheathed in
an extension of the plasma membrane. Prokaryotic flagella have a
different structure.
• Cilium-a short cellular appendage containing microtubules.
~motile cilium-specialized for locomotion and is formed from
a core of nine outer doublet microtubules and two inner single
microtubules (the “9+2” arrangement) ensheathed in an extension of
the plasma membrane
~primary cilium-nonmotile; plays a sensory and signaling role;
it lacks the two inner microtubules (the “9+0” arrangement)
• Basal body-a eukaryotic cell structure consisting of a 9 + 0
arrangement of microtubule triplets. The basal body may organize the
microtubule assembly of a cilium or flagellum and is structurally very
similar to a centriole.
• Dyneins-in cilia and flagella, a large contractile protein extending
from one microtubule doublet to the adjacent doublet. ATP hydrolysis
drives changes in dynein shape that lead to bending of cilia and flagella
• Microfilament (actin filament)-a cable composed of actin
proteins in the cytoplasm of almost every eukaryotic cell,
making up part of the cytoskeleton and acting alone or with
myosin to cause cell contraction
• Actin-a globular protein that links into chains, two of which
twist helically about each other, forming microfilaments (actin
filaments) in muscle and other kinds of cells
• Cortex-the outer region of cytoplasm in a eukaryotic cell,
lying just under the plasma membrane, that has a more gel-like
consistency than the inner regions, due to the presence of
multiple microfilaments
• Myosin-a type of protein filament that acts as a motor
protein with actin filaments to cause cell contraction
• Pseudopodium-a cellular extension of amoeboid cells used in
moving and feeding
• Cytoplasmic streaming-a circular flow of cytoplasm, involving
myosin and actin filaments, that speeds the distribution of materials
with in cells
• Intermediate filament-a component of the cytoskeleton that
includes filaments intermediate in size between microtubules and
microfilaments
• Cell wall-a protective layer external to the plasma membrane in the
cells of plants, prokaryotes, fungi, and some protists (polysaccharides
such as cellulose, chitin, and peptidoglycan are an important structural
component of cell walls)
• Primary cell wall-in plants, a relatively thin and flexible layer first
secreted by a young cell
• Middle lamella-in plants, a thin layer of adhesive extracellular
material, primarily pectins, found between the primary walls of
adjacent young cells
• Secondary cell wall-in plants, a strong and durable matrix often
deposited in several laminated layers for cell protection and support
• Extracellular matrix (ECM)-the substance in which animal cells
are embedded, consisting of protein and polysaccharides synthesized
and secreted by cells
• Collagen-a glycoprotein in the extracellular matrix of animal cells
that forms strong fibers, found extensively in connective tissue and
bone; the most abundant protein in the animal kingdom
• Proteoglycan-a glycoprotein consisting of a small core protein with
many carbohydrate chains attached, found in the extracellular matrix of
animal cells (may consist of up to 95% carbohydrate)
• Fibronectin-a glycoprotein that helps animal cells attach to the
extracellular matrix
• Integrins-in animal cells, a transmembrane receptor protein that
interconnects the extracellular matrix and the cytoskeleton
• Plasmodesma-an open channel in the cell wall of a plant through
which strands of cytosol connect from an adjacent cell
• Tight junction-a type of intercellular junction in animal cells that
prevents the leakage of material between cells
• Desmosomes-a type of intercellular junction in animal cells that
functions as a rivet
• Gap junctions-a type of intercellular junction in animals that allows
the passage of materials between cells
1) Cells Are Studied Under
Microscopes
• Cells are the most basic unit of life
• Too small to be seen with the naked eye, so
we use microscopes
Light Microscope
•
•
•
•
.2 um
200 nm
Magnifies up to 1000x
Uses light and needs contrast
Scanning Electron Microscope
• .2 um and smaller
• Beams of electron
• Used for details of surface of specimen
Transmission Electron
• Study internal ultrastructure of cells
• Organelle slides can be made by using cell
fractionation
• Separates parts of cell
2) Cells Complex Structures/Function
• Nucleus-houses chromosomes(DNA), contains
nucleoli
• Ribosome-makes proteins
• ER
1. Smooth- makes lipids, metabolizes carbs, Ca
2+ storage, detoxifies
2. Rough- helps make proteins, produces new
membrane
• Golgi- modifies proteins, makes
polysaccharides, packaging/shipping
• Lysosome- breaks down “food” and damaged
organelles
• Vacuole- digestion, storage, waste disposal,
water balance, cell growth, and protection
(plants only)
• Cytosol- contains organelles
• Plasma membrane- controls cell intake and
output
• Mitochondrion-cellular respiration
• Chloroplast-photosynthesis
• Peroxisome- produces hydrogen peroxide and
converts it to water
• Cytoskeleton- structural support, mobility, and
signal transmission
3) Prokaryotic vs. Eukaryotic
Prokaryotic
Eukaryotic
• DNA in nucleoid
• DNA found in nucleus
• Has hard capsule and cell wall
• Only cell wall in plant; no capsule
• Only free ribosomes
• Ribosomes are free and on the ER
4) Extracellular and Intracellular
Components
• Cell Wall- 3 layers to add strength and
structure
• ECM- complex network outside cell
membrane that helps regulate cell behavior
• Plasmodesmata- channels in cell wall that
connects plants cells
• Gap Junctions- in animal cells
• Tight Junctions and Desmosomes- keep cells
together and protect from leakage
This chart shows the various parts and functions of the cell. It includes the
nucleus, cell membrane, cytoplasm, ribosomes, endoplasmic reticulum,
mitochondria, golgi bodies, lysosomes, vacuoles, cell wall, and
chloroplasts. The nucleus is made up of chromatin and contains nucleoli
which is where ribosomal subunits are made. The cell membrane forms
the boundary for the cell and selectively permits the passage of materials
into and out of the cell. The cytoplasm is a jelly-like substance that helps
keep the organelles inside the cell. The ribosomes can be found in the
cytoplasm or on the rough ER and are sites of protein synthesis. The ER can
be rough or smooth. The smooth ER synthesizes lipids, metabolizes carbs,
and detoxifies drugs and poisons while the rough ER transports aids in
synthesis of secretory and other proteins from bound ribosomes .
Mitochondria is where cellular respiration occurs and most of the ATP is
generated. The Golgi Apparatus is active in synthesis, modification, sorting,
and secretion of cell products. Lysosomes are digestive organelles where
macromolecules are hydrolyzed. Vacuoles function as a storage, hydrolyze
macromolecules, and break down waste products in plant cells. The cell
wall provides a shape in plant cells. The chloroplasts convert the energy of
the sunlight into chemical energy stored in sugar molecules.
Comparison of a Plant and Animal Cell
Animal Cell
Plant Cell
These two pictures show the difference between a plant and animal
cell. Animal cells have lysosomes, centrosomes, and flagella (some are
present in plant sperm) while plant cells do not. The centrosome is an
area where the cell’s microtubules are initiated and they contain a pair
of centrioles. The function is unknown. Flagella is made up of a cluster
of microtubules within an extension of the plasma membrane and
allows the animal cell to move. Plant cells have chloroplasts, central
vacuoles, cell wall, and plasmodesmata while animal cells do not. The
plasmodesmata connect the cytoplasm of adjacent cells and allow the
passage of some molecules from cell to cell.
Question 1
All organisms are made out of
A.
B.
C.
D.
Tissue
Cells
Bones
Blood
Question 2
An organelle present in a prokaryotic cell is
A.
B.
C.
D.
ER
Nuclear envelope
Ribosomes
Chloroplast
Question 3
The surface to volume ration is used to
measure cell
A.
B.
C.
D.
Size
Shape
Size and shape
None of the above
Question 4
Active transport happens in the
A.
B.
C.
D.
Outside of the cell
The cell
The cell wall
Your dog
Question 5
Microscopy includes the use of
A.
B.
C.
D.
Light microscopes
Electron microscopes
Scanning/Transmission microscopes
All of the above
**Word has been previously defined
Vocab
• Selective permeability-a property of biological membranes
that allows them to regulate the passage of substances
• Amphipathic-having both a hydrophilic region and a
hydrophobic region
• Fluid mosaic model-the currently accepted model of cell
membrane structure, which envisions the membrane as a
mosaic of protein molecules drifting laterally in a fluid bilayer
of phospholipids
• Integral proteins-typically a transmembrane protein with
hydrophobic regions that extend into and often completely
span the hydrophobic interior of the membrane and with
hydrophilic regions in contact with the aqueous solution on
either side of the membrane (or lining the channel in the case
of a channel protein)
• Peripheral proteins-a protein loosely bound to the surface
of a membrane or to part of an integral protein and not
embedded in the lipid bilayer
• Glycolipids-a lipid with covalently attached
carbohydrate(s)
• **Glycoproteins- a protein with one or more carbohydrates
covalently attached to it
• Transport protein-a transmembrane protein that helps a
certain substance or class of closely related substances to cross
the membrane
• Aquaporin-a channel protein in the plasma membrane of a
plant, animal, or microorganism cell that specifically
facilitates osmosis, the diffusion of water across the membrane
• Diffusion-the spontaneous movement of a substance down
its concentration gradient, from a region where it is more
concentrated to a region where it is less concentrated
• Concentration gradient-a region along which the density
of a chemical substance increases or decreases
• Passive transport-the diffusion of a substance across a
biological membrane with no expenditure of energy
• Osmosis-the diffusion of water across a selectively
permeable membrane
• Tonicity-the ability of a solution surrounding a cell to cause
that cell to gain or lose water
• Isotonic-referring to a solution that, when surrounding a
cell, has no effect on the passage of water into or out of the
cell
• Hypertonic-referring to a solution that, when surrounding a
cell, will cause the cell to lose water
• Hypotonic-referring to a solution that, when surrounding a
cell, will cause the cell to take up water
• Osmoregulation-regulation of solute concentrations and
water balance by a cell or organism
• Turgid-swollen or distended (a walled cell becomes turgid
if it has a greater solute concentration than its surroundings,
resulting in entry of water)
• Flaccid-limp; lacking in stiffness or firmness
• Plasmolysis-a phenomenom in walled cells in which the
cytoplasm shrivels and the plasma membrane pulls away from
the cell wall; occurs when the cell loses water to a hypertonic
environment
• Facilitated diffusion-the spontaneous passage of molecules or ions
across a biological membrane with the assistance of specific
transmembrane transport proteins
• Ion channels-a transmembrane protein channel that allows a
specific ion to flow across the membrane down its concentration
gradient
• Gated channels-a transmembrane protein channel that opens or
closes in response to a particular stimulus
• Active transport-the movement of a substance across a cell
membrane, with an expenditure of energy, against its concentration or
electrochemical gradient; mediated by specific transport proteins
• Sodium-potassium pump-a transport protein in the plasma
membrane of animal cells that actively transports sodium out of the cell
and potassium into the cell
• Membrane potential-the difference in electrical charge (voltage)
across a cell’s plasma membrane, due to the differential distribution of
ions; this affects the activity of excitable cells and the transmembrane
movement of all charged substances
• Electrochemical gradient-the diffusion gradient of an ion, which is
affected by both the concentration difference of the ion across a
membrane (a chemical force) and the ion’s tendency to move relative to
the membrane potential (an electrical force)
• Electrogenic pump-an ion transport protein that generates voltage
across a membrane
• Proton pump-an active transport protein in a cell membrane that
uses ATP to transport hydrogen ions out of a cell against their
concentration gradient, generating a membrane potential in the process
• Cotransport-the coupling of the “downhill” diffusion
of one substance to the “uphill” transport of another
against its own concentration gradient
• Exocytosis-the cellular secretion of biological
molecules by the fusion of vesicles containing them with
the plasma membrane
• Endocytosis-cellular uptake of biological molecules
and particulate matter via formation of new vesicles from
the plasma membrane
• **Phagocytosis-a type of endocytosis in which large
particulate substances are taken up by a cell. It is carried
out by some protists and by certain immune cells of
animals
• Pinocytosis-a type of endocytosis in which the
cell ingests extracellular fluid and its dissolved
solutes
• Receptor-mediated endocytosis-the movement
of specific molecules into a cell by the inward
budding of membranous vesicles containing
proteins with receptor sites specific to the molecules
being taken in; enables a cell to acquire bulk
quantities of specific substances
• Ligand-a molecule that binds specifically to
another molecule, usually a larger one
5) Membrane Structure
• Selective permeability- allows some substances
to cross it more easily than others
• Amphipathic- has both hydrophilic and
hydrophobic
• Fluid Mosaic Model- proteins dispersed in or
attached to a bilayer of phospholipids
• Phospholipids can move laterally or flip-flop
• Kinks of unsaturated phospholipids cause fluidity
• Cholesterol reduces membrane fluidity
6) Osmosis and Diffusion
• Concentration gradient (causes osmosis and
diffusion)- substances move to less
concentrated areas
Diffusion- movement of a substance goes
down the concentration gradient
Osmosis- movement of water down the
concentration gradient
• Isotonic
– Cell and outside fluid have equal concentration
– No effect(flaccid, limp in plants)
• Hypotonic
–
–
–
–
Less solute outside
Water goes in cell
Cell lyses
Normal in plant
• Hypertonic
–
–
–
–
More solute outside
Water leaves cell
Cell shrivels
Plasmolyzed in plants
7) Passive vs. Active Transport
Passive
Active
• Diffusion/osmosis
• Energy required (ATP)
• No energy needed
• Sodium-Potassium pump
• Aquaporins (water channels)
• Electrogenic pump- generates voltage
across membrane
• Facilitated Diffusion- aid of proteins
(includes channel proteins, carrier
proteins, ion channels, and gated
channels)
• Co-transport- ATP powered pump
transports a solute that indirectly
causes active transport of another
substance
• Moves down the concentration
gradient
• Moves up the concentration gradient
• Proton pump
8) Exocytosis and Endocytosis
• Exocytosis- vesicles from Golgi carry waste out of
cell
• Endocytosis- molecules taken in by pinching off
part of plasma membrane
• Phagocytosis- arm-like pseudopodium engulfs
food
• Pinocytosis- cell “gulps” extracellular fluid and
the molecules in it
• Receptor mediated endocytosis-attachment of
ligand to receptors on cell membrane causes
endocytosis
Animal Cell’s Plasma Membrane
The plasma membrane is selectively permeable (allows some substances to
cross it more easily than others) and is made of phospholipids. The proteins
held together by weak interactions cause the membrane to be fluid. Some
organic molecules found on the membrane are phospholipids, integral
proteins, peripheral proteins, and carbohydrates. Phospholipids provide a
hydrophobic barrier that separates the cell from its liquid environment.
Hydrophilic molecules cannot easily enter the cell, but hydrophobic molecules
can enter easily. Integral proteins are embedded in the membrane and
peripheral proteins are loosely bound to the membrane’s surface.
Carbohydrates are needed in cell-cell recognition and help develop organisms.
Cell surface carbohydrates are different from species to species and are the
reason that blood transfusions must be type-specific.
Exocytosis and Endocytosis
Large molecules are moved across the cell membrane through exocytosis
and endocytosis. In exocytosis, vesicles from the cell’s interior fuse with the
cell membrane. In endocytosis, the cell forms new vesicles from the plasma
membrane. There are three types of endocytosis: phagocytosis, pinocytosis,
and receptor-mediated endocytosis. In phagocytosis, the cell wraps
pseudopodia around a solid particle and brings it into the cell. In
pinocytosis, the cell takes in small droplets of extracellular fluid within small
vesicles. In receptor-mediated endocytosis, certain substances bind to
specific receptors on the cell’s surface and this causes a vesicle to form
around the substance and then to pinch off into the cytoplasm.
Question 6
Which process includes all others
A.
B.
C.
D.
Osmosis
Diffusion across a membrane
Passive transport
Facilitated diffusion
Question 7
Isotonic, hypotonic, and hypertonic are
A.
B.
C.
D.
Forms of osmosis
Forms of diffusion
Forms of meiosis
Forms of mitosis
Question 8
Exocytosis is
A. The transport of lyses
B. When transport vesicles migrate to the plasma
membrane
C. A totally new way to do osmosis
D. None of the above
Question 9
The fluid mosaic model says that cells have
A.
B.
C.
D.
Water pores
Protein pores
Phosphate bilayer
Amphipathic proteins
Question 10
Passive transport
A.
B.
C.
D.
Uses energy
Does not use energy
Is considered facilitated diffusion
All of the above
**Word has been previously defined
Vocab
• Signal transduction pathway-a series of steps linking a mechanical
or chemical stimulus to a specific cellular response
• Mating type a-cells that secrete a factor which binds to α cells’
specific protein receptors
• Mating type α-cells that secrete α factor which binds to a cells’
specific protein receptors
• Local regulator-a secreted molecule that influences cells near
where it is secreted
• Hormones-in multicellular organisms, one of the many types of
secreted chemicals that are formed in specialized cells, travel in body
fluids, and act on specific target cells in other parts of the body to
change their functioning
• Reception-the target cell’s detection of a signaling molecule coming
from outside the cell
• Transduction-the conversion of a signal from outside the cell to a
form that can bring about a specific cellular response
• Response-the change in a specific cellular activity
brought about by a transduced signal from outside the cell
• **Ligand- a molecule that binds specifically to another
molecule, usually a larger one
• G protein-coupled receptor (G protein-linked
receptor)-a signal receptor protein in the plasma
membrane that responds to the binding of a signaling
molecule by activating a G protein
• G protein-a GTP-binding protein that relays signals
from a plasma membrane signal receptor, known as a G
protein-coupled receptor, to other signal transduction
proteins inside the cell
• Receptor tyrosine kinase-a receptor protein in the plasma
membrane, the cytoplasmic (intracellular) part of which can
catalyze the transfer of a phosphate group from ATP to a
tyrosine on another protein. It responds to the binding of a
signaling molecule by dimerizing and then phosphorylating a
tyrosine on the cytoplasmic portion of the other receptor in the
dimer; the phosphorylated tyrosines on the receptors then
activate other signal transduction proteins within the cell
• Ligand-gated ion channel-a protein pore in cellular
membranes that opens or closes in response to a signaling
chemical (its ligand), allowing or blocking the flow of specific
ions
• Protein kinase-an enzyme that transfers phosphate groups
from ATP to a protein, thus phosphorylating the protein
• Protein phosphatases-an enzyme that removes
phosphate groups from (dephosphorylates) proteins, often
functioning to reverse the effect of a protein kinase
• Second messenger-a small, nonprotein, water-soluble
molecule or ion that relays a signal to a cell’s interior in
response to a signaling molecule bound by a signal
receptor protein
• Cyclic AMP (cAMP)-cyclic adenosine
monophosphate, a ring-shaped molecule made from ATP
that is a common intracellular signaling molecule (second
messenger) in eukaryotic cells; also a regulator of some
bacterial operons
• Adenylyl cyclase-an enzyme that converts ATP to cyclic AMP in
response to a signal
• Inositol trisphosphate (IP3)-a second messenger that functions as
an intermediate between certain nonsteroid hormones and a third
messenger, a rise in cytoplasmic concentraion of calcium ions
• Diacylglycerol (DAG)-a second messenger produced by the
cleavage of a certain kind of phospholipid in the plasma membrane
• Scaffolding protein-a type of large relay protein to which several
other relay proteins are simultaneously attached, increasing the
efficiency of signal transduction
• Apoptosis-a program of controlled cell suicide, which is brought
about by signals that trigger the activation of a cascade of suicide
proteins in the cell destined to die
9) Cell Signaling: Reception,
Transduction, and Response
• Cells communicate using a signal transduction
pathway
1. Reception- cell detection of signaling molecule
– G protein-coupled receptor-attachment of ligand, GTP
replaces FDP, it activates an enzyme and the signal is
sent
– Receptor tyrosine kinase- ligand binds, dimer formed
and phosphorylated, activates relay proteins, cellular
response sent
– Ligand-gated ion channel- ligand opens gate, ions
come into cell, cellular response sent
2. Transduction- signal transduced through a
pathway, with many forms, proteins, and
includes phosphorylation cascades (which
enzyme phosphotase removes)
-second messengers help broadcast signals
quickly
3) Response- pathways can activate
transcription factors (regulate genes) or can
regulate enzyme activity
-scaffolding proteins increase signal
transduction efficiency
-unbinding of ligand turns off signal
10) Apoptosis
• Programmed cell death
• Orderly and cause no damage to cells around
it
• Signals can originate in or outside the cell
• Occurs during embryonic development to
form fingers, toes, etc.
Cell Signaling
There are three steps to cell signaling: reception, transduction,
and response. Reception is the target cell’s detection of a
signaling molecule coming from outside the cell. A chemical
signal is detected when the signaling molecule binds to a
receptor protein located at the cell’s surface or inside the cell.
Transduction begins when the binding of the signaling molecule
changes the receptor protein. The transduction stage converts
the signal to a form that can bring about a specific cellular
response. During response the transduced signal finally triggers
a specific cellular response. The response may be almost any
imaginable cellular activity.
A G-protein-coupled receptor is a membrane receptor that works with the help
of a G protein. The ligand or signaling molecule will bind to the G-proteincoupled receptor. This causes a change in the receptor so that it may now bind
to an inactive F protein, causing a GTP to displace the GDP. This activates the F
protein. The F protein binds to a specific enzyme and activates it. When the
enzyme is activated, it can trigger the next step in a pathway leading to a cellular
response. All the molecular shape changes are temporary.
Question 11
The three stages of cell signaling are reception,
transduction, and response
a.True
b.False
Question 12
Apoptosis is scheduled cell birth
a.True
b.False
Question 13
At each step in the signaling process, the signal
is transduced
a.True
b.False
Question 14
The activation of receptor tyrosine kinases is
characterized by GTP hydrolysis
a.True
b.False
Question 15
Apoptosis involves the activation of cellular
enzymes
a.True
b.False
*Word will be defined again in a later chapter
**Word has been previously defined
Vocab
• Cell division-the reproduction of cells
• Cell cycle-an ordered sequence of events in the
life of a cell, from its origin in the division of a
parent cell until its own division into two; the
eukaryotic cell cycle is composed of interphase
(including G1, S, and G2 subphases) and M phase
(including mitosis and cytokinesis)
• Genome-the genetic material of an organism or
virus; the complete complement of an organism’s or
virus’s genes along with its noncoding nucleic acid
sequences
• **Chromosome-a cellular structure carrying genetic
material, found in the nucleus of eukaryotic cells; consists of
one very long DNA molecule and associated proteins (A
bacterial chromosome consists of a single circular DNA
molecule and associated proteins and is found in the nucleoid
region)
• *Somatic sells-any cell in a multicellular organism except a
sperm or egg
• *Gametes-a haploid reproductive cell. Gametes unite
during sexual reproduction to produce a diploid zygote
• **Chromatin- the complex of DNA and protein that makes
up a eukaryotic chromosome (dispersed form, which occurs
when the cell is not dividing, is a mass of very long, thin fibers
that are not visible with a light microscope)
• Sister chromatid-either of two copies of a duplicated
chromosome attached to each other by proteins at the
centromere and, sometimes, along the arms (two joined
sister chromatids make up a chromosome; chromatids are
eventually separated during mitosis or meiosis II)
• Centromere-the specialized region of the chromosome
where two sister chromatids are most closely attached
• Mitosis-a process of nuclear division in eukaryotic
cells conventionally divided into five stages: prophase,
prometaphase, metaphase, anaphase, and telophase.
Mitosis conserves chromosome number by allocating
replicated chromosomes equally to each of the daughter
nuclei
• Cytokinesis-the division of the cytoplasm to form two separate
daughter cells immediately after mitosis, meiosis I, or meiosis II
• *Meiosis- a modified type of cell division in sexually reproducing
organisms consisting of two rounds of cell division but only one round
of DNA replication: resulting in cells with half the number of
chromosome sets as the original cell
• Mitotic (M) phase-the phase of the cell cycle that includes mitosis
and cytokinesis
• Interphase-the period in the cell cycle when the cell is not dividing;
the cellular metabolic activity is high, chromosomes and organelles are
duplicated, and cell size may increase (accounts for 90% of the cell
cycle)
• G1 phase-the first gap, or growth phase, of the cell cycle, consisting
of the portion of interphase before DNA synthesis occurs
• S phase-the synthesis phase of the cell cycle; the portion of
interphase during which DNA is replicated
• G2 phase-the second gap, or growth phase, of the cell
cycle, consisting of the portion of interphase after DNA
synthesis occurs
• Prophase-the first stage of mitosis, in which the chromatin
condenses, the mitotic spindle begins to form, and the
nucleolus disappears, but the nucleus remains intact
• Prometaphase-the second stage of mitosis, in which
discrete chromosomes consisting of identical sister chromatids
appear, the nuclear envelope fragments, and the spindle
microtubules attach to the kinetochores of the chromosomes
• Metaphase-the third stage of mitosis, in which the
spindle is complete and the chromosomes, attached to
microtubules at their kinetochores, are all aligned at the
metaphase plate
• Anaphase-the fourth stage of mitosis, in which the
chromatids of each chromosome have separated and the
daughter chromosomes are moving to the poles of the cell
• Telophase-the fifth and final stage of mitosis, in which
daughter nuclei are forming and cytokinesis has typically
begun
• Mitotic spindle-an assemblage of microtubules and
associated proteins that is involved in the movements of
chromosomes during mitosis
• **Centrosome- structure made of two centrioles present in
the cytoplasm of animal cells, important during cell division;
functions as a microtubule-organizing center
• Aster-a radial array of short microtubules that extends from
each centrosome toward the plasma membrane in an animal
cell undergoing mitosis
• Kinetochore-a structure of proteins attached to the
centromere that links each sister chromatid to the mitotic
spindle
• Metaphase plate-an imaginary plane midway between the
two poles of a cell in metaphase on which the centromeres of
all the duplicated chromosomes are located
• Cleavage-the process of cytokinesis in animal cells,
characterized by pinching of the plasma membrane
• Cleavage furrow-the first sign of cleavage in an
animal cell; a shallow groove in the cell surface near the
old metaphase plate
• Cell plate-a double membrane across the midline of a
dividing plant cell, between which the new cell wall forms
during cytokinesis
• Binary fission-a method of asexual reproduction by
“division in half.” In prokaryotes, binary fission does not
involve mitosis; but in single-celled eukaryotes that
undergo binary fission, mitosis is part of the process.
• Origin of replication-site where the replication of a
DNA molecule begins, consisting of a specific sequence
of nucleotides
• Cell cycle control system-a cyclically operating set of
molecules in the eukaryotic cell both triggers and
coordinates key events in the cell cycle
• Checkpoint-a control point in the cell cycle where stop
and go-ahead signals can regulate the cycle
• G0 phase-a nondividing state occupied by cells that
have left the cell cycle
• Cyclin-a cellular protein that occurs in a cyclicallyfluctuating concentration and that plays an important role
in regulating the cell cycle
• Cyclin-dependent kinase (Cdk)-a protein kinase that
is active only when attached to a particular cyclin
• MPF (Maturation-promoting factor/M-phasepromoting factor)-a protein complex required for a
cell to progress from late interphase to mitosis. The
active form consists of cyclin and a protein kinase
• Growth factor-a protein released by certain cells
that stimulates other cells to divide
• Density-dependent inhibition-the phenomenon
observed in normal animal cells that causes them to
stop dividing when they come into contact with one
another
• Anchorage dependence-the requirement that a
cell must be attached to a substratum in order to
divide
• Transformation-the conversion of a normal
animal cell to a cancerous cell
• Benign tumor-a mass of abnormal cells that
remains at the site of its origin
• Malignant tumor-a cancerous tumor that is
invasive enough to impair the functions of one or
more organs
• Metastasis-the spread of cancer cells to locations
distant from their original site
11) Cell Cycle
1. Interphase contains G1, S, and G2, which
takes up 90% of the cell cycle, cell grows and
organelles and chromosomes duplicate.
2. Mitosis takes up the other 10%
3. Cycle is controlled by checkpoints- cell either
receives the go-ahead or stop signal
4. If stopped, cell goes into the G0 phase (nondividing state)
5. Loss of cell cycle controls can lead to cancer
12) Mitosis Steps
1. Prophase-condensing of chromatin, nucleoli gone, sister
chromatid cohesion, mitotic spindle form, centrosomes
separate
2. Prometaphase- nuclear envelope fragments, chromosomes
condensed, kinetochore microtubules formed
3. Metaphase- centrosomes at opposite poles, chromosomes
line up at metaphase plate
4. Anaphase- daughter chromosomes separate and more to
towards opposite ends of the cell.
5. Telophase/Cytokinesis- organelles and cytoplasm split, 2
cells form and split (genetically identical)
Interphase can be divided into sub-phases: the G1 phase, the S
phase, and the G2 phase. In the G1 phase the cell grows while
carrying out cell functions unique to its cell type. In the S phase the
cell continues to carry out its unique functions and duplicates its
chromosomes. This means it makes a copy of the DNA that makes
up the cell’s chromosomes. The G2 phase is the gap after the
chromosomes have been duplicated and just before mitosis. The
cell prepares to divide. The circle graph also shows the M
phase(usually the shortest part of the cycle and includes mitosis
and cytokinesis). In the M phase, mitosis divides the nucleus and
distributes its chromosomes to the daughter nuclei, and cytokinesis
divides the cytoplasm, producing two daughter cells.
Interphase:
1. A nuclear envelope bounds the nucleus.
2. Two centrosomes have formed by replication of a single centrosome.
Prophase:
1. The chromatin becomes more tightly coiled into discrete chromosomes.
2. The nucleoli disappear.
3. The mitotic spindle begins to form in the cytoplasm.
Metaphase:
1. The microtubules move the chromosomes to the metaphase plate at the equator of
the cell.
2. The centrioles have migrated to opposite poles in the cell.
Anaphase:
1. Sister chromatids begin to separate, pulled apart by motor molecules interacting
with kinetochore microtubules.
2. The cell elongates with the help of motor molecules.
3. The opposite ends of the cell both contain complete and equal sets of
chromosomes.
Telophase:
1. The nuclear envelope re-form around the sets of chromosomes located at opposite
ends of the cell.
2. The chromatin fiver of the chromosomes becomes less condensed.
3. Cytokinesis begins, during which the cytoplasm of the cell is divided. In animal cells,
a cleavage furrow forms that divides the cytoplasm; in plant cells, a cell plate forms
that divides the cytoplasm.
Question 16
The cell is most likely in
a.G1
b.G2
c. Anaphase
d.Prophase
Question 17
Which of the following doesn’t occur during
mitosis
a.Replication of DNA
b.Spindle formation
c. Separation of sister chromatids
d.Formation of spindle poles
Question 18
How many different phases can a cell be in
a.3
b.8
c. 6
d.10
Question 19
Cell division results in genetically identical
daughter cells
a.True
b.False
Question 20
The mitotic phase does not alternate with
interphase in the cell cycle
a.True
b.False
**Word has been previously defined
Vocab
• Heredity-the transmission of traits from one generation
to the next
• Variation-differences between members of the same
species
• Genetics-the scientific study of heredity and hereditary
variation
• Gene-a discrete unit of hereditary information
consisting of a specific nucleotide sequence in DNA (or
RNA, in some viruses)
• **Gametes- a haploid reproductive cell. Gametes unite
during sexual reproduction to produce a diploid zygote
• Locus-a specific place along the length of a
chromosome where a given gene is located
• Asexual reproduction-the generation of offspring from
a single parent that occurs without the fusion of gametes
(by budding, division of a single cell, or division of the
entire organism into two or more parts). In most cases, the
offspring are genetically identical to the parent
• Clone-a lineage of genetically identical individuals or
cells
• Sexual reproduction-a type of reproduction in which
two parents give rise to offspring that have unique
combinations of genes inherited from the gametes of the
parents
• Life cycle-the generation-to-generation sequence of
stages in the reproductive history of an organism
• **Somatic cell- any cell in a multicellular organism except
a sperm or egg
• Karyotype-a display of the chromosome pairs of a cell
arranged by size and shape
• Homologous chromosomes (homologs/homologous pair)a pair of chromosomes of the same length, centromere
position, and staining pattern that possess genes for the same
characteristic at corresponding loci. One homologous
chromosome is inherited from the father and the other from the
mother.
• Sex chromosomes-chromosomes responsible for
determining the sex of an individual
• Autosomes-a chromosome that is not directly involved in
determining sex; not a sex chromosome
• Diploid cell-a cell containing two sets of chromosomes
(2n), one set inherited from each parent
• Haploid cells-a cell containing only one set of
chromosomes (n)
• Fertilization-the union of haploid gametes to produce a
diploid zygote
• Zygote-the diploid product of the union of the haploid
gametes during fertilization; a fertilized egg
• **Meiosis-a modified type of cell division in sexually
reproducing organisms consisting of two rounds of cell
division but only one round of DNA replication: resulting
in cells with half the number of chromosome sets as the
original cell
• Alternation of generations-a life cycle in which
there is both a multicellular diploid form, the
sporophyte, and a multicellular haploid form, the
gametophyte; characteristic of plants and some
algae
• Sporophyte-in organisms (plants and some algae)
that have alternation of generations, the
multicellular diploid form that results from the
union of gametes.
• Spore-in the cell cycle of a plant or alga
undergoing alternation of generations, a haploid cell
produced in the sporophyte by meiosis.
• Gametophyte-in organisms (plants and some
algae) that have alternation of generations, the
multicellular haploid form that produces haploid
gametes by mitosis.
• Meiosis I-the first division of a two-stage process
of cell division in sexually reproducing organisms
that results in cells with half the number of
chromosome sets as the original cell
• Meiosis II- the second division of a two-stage
process of cell division in sexually reproducing
organisms that results in cells with half the number
of chromosome sets as the original cell
• Synapsis-the pairing and physical connection of replicated
homologous chromosomes during prophase I of meiosis
• Crossing over-the reciprocal exchange of genetic material
between nonsister chromatids during prophase I of meiosis
• Chiasma-the X-shaped, microscopically visible region
where homologous nonsister chromatids have exchanged
genetic material through crossing over during meiosis, the two
homologs remaining associated due to sister chromatid
cohesion
• Recombinant chromosome-a chromosome created when
crossing over combines the DNA from two parents into a
single chromosome
13) Chromosomal Information
• Maternal and paternal DNA involved in meiosis
• Homologous chromosomes- mom and dad set of the
same chromosome
• Meiosis forms gametes/sex cells (haploid) whereas
mitosis forms somatic cells (diploid)
• Synapsis-connection between homologous
chromosomes
• Crossing over- genetic rearrangement between
nonsister chromatids
• Chiasma- physical manifestation of crossing over
14) Meiosis Steps
1. Prophase I- crossing over occurs, chromosomes separate
2. Metaphase I- homologous chromosomes line up at
metaphase plate
3. Anaphase I- homologous chromosomes separate (now sister
chromatids)
4. Telophase I/Cytokinesis- cell splits
5. Prophase II- Mitotic Spindle forms
6. Metaphase II- sister chromatids line up at metaphase plate
7. Anaphase II- sister chromatids separate
8. Telophase II/Cytokinesis- 4 haploid genetically different cells
form
Genetic Variation
• Caused by 3 things:
1. Independent assortment- each homologous pair
is positioned independently of the others
2. Crossing Over- switching of genes on a
chromosome between maternal and paternal
chromosomes causes the daughter chromosome
to be genetically individual
3. Random Fertilization- the egg fertilized by the
sperm is entirely random
Interphase: Each of the chromosomes makes a copy of itself. The centrosome
divides.
Prophase I: The chromosomes condense, resulting in two sister chromatids
attached at their centromeres. Synapsis and crossing over occurs. Crossing
over is when the DNA from one homologue is cut and exchanged with an
exact portion of DNA from the other homologue. After crossing over, the
centrioles move away from each other, the nuclear envelope disintegrates,
and spindle microtubules attach to the kinetochores forming on the
chromosomes that begin to move to the to the metaphase plate of the cell.
Metaphase I: The homologous pairs of chromosomes are lined up at the
metaphase plate, and microtubules from each pole attach to each member of
the homologous pairs in preparation for pulling them to opposite ends of the
cell.
Anaphase I: The spindle apparatus helps to move the chromosomes toward
opposite ends of the cell; sister chromatids stay connected and move together
toward the poles.
Telophase I: The homologous chromosomes move until they reach the
opposite poles. Cytokinesis occurs during telophase. A cleavage furrow occurs
in animal cells and cell plates occur in plant cells. This produces two haploid
cells.
Prophase II: A spindle apparatus forms, and sister chromatids move
toward the metaphase plate.
Metaphase II: The chromosomes are lined p on the metaphase plate,
and the kinetochores of each sister chromatid prepare to move to
the opposite poles.
Anaphase II: The centromeres of the sister chromatids separate, and
individual chromosomes move to opposite ends of the cell.
Telophase II and Cytokinesis: The chromatids have moved all the way
to opposite ends of the cell, nuclei reappear, and cytokinesis occurs.
Each of the four daughter cells has the haploid number of
chromosomes and is genetically different from the other daughter
cells and from the parent cell.
Question 21
A haploid and diploid cell have a combined
____ chromosomes
a.12
b.69
c. 22
d.68
Question 22
At which phase of meiosis II does the separation
of sister chromatids occur?
a.Metaphase II
b.Anaphase I
c. Prophase II
d.Anaphase II
Question 23
What life cycle stage is found in plants but not
animals?
a.Gamete
b.Multicellular haploid
c. zygotes
d.unicellular diploid
Question 24
Reproductive gametes are called somatic cells.
a.True
b.False
Question 25
A human cell containing 22 autosomes and a Y
chromosome is a ____.
a.somatic cell of a female
b.somatic cell of a male
c. a sperm
d.an egg
Lab 1: Osmosis and Diffusion
Overview: This lab was used to investigate the processes of
diffusion and osmosis in a model membrane system. It was also
used to discuss water potential in relation to living plant tissues.
Objectives: After doing this lab, you should be able to:
 Measure the water potential of a solution in a controlled
experiment
 Determine the osmotic concentration of living tissue or an
unknown solution from experimental data
 Describe the effects of water gain or loss in plant and animal
cells
 Relate osmotic potential to solute concentration and water
potential
Lab 3:Mitosis and Meiosis
• Lab 3 was used to further our understanding
of mitosis, meiosis, and the cell cycle. We
looked at onion root tip cells and counted the
number of cells at each phase to determine
how much time each phase takes in the cell
cycle. We found that interphase takes up the
most time while mitosis and meiosis take up
much less.
Free Response # 1
All cells come from other cells. New cells are formed from
cell division which involves the division of the nucleus and the
cytoplasm. There are two main types of nuclear division: mitosis and
meiosis. The processes of these are alike yet differ.
A) Explain the process of mitosis.
B) Explain the process of meiosis.
C) Contrast mitosis and meiosis. You may compose a diagram/chart.
Example Answer Part A
There are five phases in mitosis: prophase, prometaphase,
metaphase, anaphase, and telophase. In prophase the chromatin becomes
more tightly coiled into discrete chromosomes. The nucleoli disappear and
the mitotic spindle begins to form in the cytoplasm. In prometaphase the
nuclear envelope begins to fragment, allowing the microtubules to attach to
the chromosomes. The two chromatids of each chromosome are held
together by protein kinetochores in the centromere region. The microtubules
will attach to the kinetochores. In metaphase the microtubules move the
chromosomes to the metaphase plate at the equator of the cell. The
centrioles have migrated to opposite poles in the cell, riding along the
developing spindle. In anaphase the sister chromatids being to separate,
pulled apart by motor molecules interacting with kinetochore microtubules.
The cell elongates with the help of motor molecules. In telophase the nuclear
envelopes re-form around the sets of chromosomes located at opposite ends
of the cell. The chromatin fiver of the chromosomes becomes less condensed.
Cytokinesis beings and the cytoplasm of the cell is divided. In animal cells, a
cleavage furrow forms and in plant cells, a cell plate forms that divides the
cytoplasm.
Example Answer Part B
The process of meiosis follows the same basic
stages as mitosis except meiosis repeats the stages. The
first stage of meiosis is prophase I. Just as in mitosis,
the chromosomes condense, centrosomes move, the
nuclear envelope breaks down, and spindles form.
However, events called synapsis and crossing over
occur that are unique to meiosis. Chromosomes
become attached in synapsis and exchange segments
during crossing over. The homologs are held together
by chiasmata—the result of crossing over—and sister
chromatid cohesion.
During metaphase I, homologs arrange on
the metaphase plate, just as in mitosis. A
kinetochore microtubule is attached to each pair
of chromatids. The homologs are then pulled
apart to opposite poles by the microtubules
during anaphase I. Unlike mitosis, the
chromatids stay attached during separation.
The first set of stages is brought to an end
by telophase I and cytokinesis. The cell splits
into two haploid cells with replicated
chromosomes. Since the chromosomes are
replicated, there is no need for duplication
during prophase II. Just the spindle apparatus
forms during prophase II.
The chromosomes position themselves on the
metaphase plate in metaphase II. Microtubules extending
from opposite poles attach themselves to the kinetochores
of sister chromatids. In anaphase II, the chromatids are
separated and moved toward opposite poles by the
microtubules. The process of meiosis ends completely by
the formation of four distinct, haploid daughter cells. This,
along with the formation of the nuclei and the
decondensation of chromosomes, occurs in telophase II and
cytokinesis, the final stages of meiosis.
Example Answer Part C
MITOSIS
• One division
• Two daughter cells (diploid)
• Produces somatic cells
• Genetically identical to the parent cell
MEIOSIS
• Two divisions
• Four daughter cells (haploid)
• Produces gametes
• Reduces number of chromosomes by
half
• Synapsis of homologs and crossing
over between non-sister chromatids
during prophase I
• Chiasmata
Free Response # 2
A)
B)
C)
D)
Define osmosis.
Define diffusion.
Compare/contrast the two.
Explain hypotonic, hypertonic, and isotonic
solutions using: osmosis/diffusion, semipermeable membrane, flaccid, turgid,
plasmolysis, and lysed.
Example Answer Part A, B, and C
A) Osmosis is the moving of water through a semipermeable membrane down its concentration
gradient (against the solute concentration gradient)
B) Diffusion is the movement of a solvent down its
concentration gradient (high concentration to low
concentration) through a semi-permeable
membrane.
C) Osmosis is the movement of water while
diffusion usually refers to movement of a solute.
They both have to do with movement down a
concentration gradient.
Example Answer Part D
D) When a cell is put in a hypotonic solution, there is less
solute on the outside than the inside, so water moves
into the cell through the semi-permeable membrane by
osmosis. This makes plant cells turgid and animal cells
swell and they can even lyse (break). When a cell is put
into a hypertonic solution, more solute is outside the cell,
so water moves out of the cell (osmosis). Because of this,
animal cells shrivel and plant cells are plasmolyzed (cell
does not touch walls). In an isotonic solution, no osmosis
occurs because the concentration is equal. Animal cells
stay the same while plant cells become flaccid (or limp).