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CHAPTER 7
A TOUR OF THE CELL
Fluorescent stain of cell
Cell Biology
1. The fundamental life processes of plants and animals depend on a variety of
chemical reactions that occur in specialized areas of the organism’s cells. As a
basis for understanding this concept, Students know:
a. cells are enclosed within semipermeable membranes that regulate their interaction with
their surroundings.
b. enzymes are proteins that catalyze biochemical reactions without altering the reaction
equilibrium and the activities of enzymes depend on the temperature, ionic conditions,
and the pH of the surroundings.
c. how prokaryotic cells, eukaryotic cells (including those from plants and animals), and
viruses differ in complexity and general structure.
d. the central dogma of molecular biology outlines the flow of information from transcription of
ribonucleic acid (RNA) in the nucleus to translation of proteins on ribosomes in the cytoplasm.
e. the role of the endoplasmic reticulum and Golgi apparatus in the secretion of proteins.
f. usable energy is captured from sunlight by chloroplasts and is stored through the
synthesis of sugar from carbon dioxide.
g. the role of the mitochondria in making stored chemical-bond energy available to cells by
completing the breakdown of glucose to carbon dioxide.
h. Students know most macromolecules (polysaccharides, nucleic acids, proteins, lipids) in
cells and organisms are synthesized from a small collection of simple precursors.
i.* how chemiosmotic gradients in the mitochondria and chloroplast store energy for ATP
production.
j* Students know how eukaryotic cells are given shape and internal organization by a
cytoskeleton or cell wall or both.
Organisms must exchange matter with the environment to
grow, reproduce and maintain organization.
Growth, reproduction and maintenance of the organization of
living systems require free energy and matter.
Molecules and atoms
from the environment
are necessary to
build new molecules.
• 1. Carbon moves from the
environment to organisms where
it is used to build carbohydrates,
proteins, lipids or nucleic acids.
Carbon is used in storage
compounds and cell formation in
all organisms.
• 2. Nitrogen moves from the
environment to organisms where
it is used in building proteins and
nucleic acids.
• 3.
Phosphorus moves from
the environment to organisms
where it is used in nucleic acids
and certain lipids.
why are cells
microscopic in size?
• http://www.youtub
e.com/watch?v=x
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Geometric relationships explain why most cells are microscopic
The smaller the object, the greater
Its ratio of surface area to volume.
Metabolic requirements depend on
passage of oxygen, nutrients and
Carbon dioxide & other metabolic
Waste through the plasma
membrane.
why are cells
microscopic in size?
• Cell size is limited by the
surface to volume ratio.
• As cells get larger the
volume increases at a
greater rate compared to
surface area.
• Large cells can not get
enough materials inside to
stay alive.
b. Surface area-to-volume ratios affect a
biological system’s ability to obtain necessary
resources or eliminate waste products.
• 1. As cells increase in volume, the relative surface area
decreases and demand for material resources increases;
more cellular structures are necessary to adequately
exchange materials and energy with the environment.
These limitations restrict cell size.
– Ex. root hairs, cells of the alveoli, cells of the villi
2. The surface area of the plasma membrane must be
large enough to adequately exchange materials; smaller
cells have a more favorable surface area-to-volume ratio
for exchange of materials with the environment.
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villi cells within the small intestine
root hair cells of plants
cells of the alveoli within lungs
All shaped and arranged in ways
that increase surface area to volume
ratio and maximize diffusion.
what types of microscopes are
used to view cells?
• Light (2,000x)
• Transmission
Electron TEM
(2,000,000x)
• Scanning Electron
SEM (3-D)
Rabbit trachea (windpipe) cell
Transmission electron microscope
(SEM)
(TEM)
Scanning electron microscope
creates 3-D image of the surface
of the same cell.
1665 1st Microscope
Robert Hooke discovered cells-cork
1950’s Electron Microscope
Revealed the geography of the cell
ORGANELLES
• Subcellular structures specialized
for various specific functions.
• “tiny organ”
• compartments or “rooms”
• each contains specific enzymes
The plasma membrane
What is the difference
between prokaryotic and
eukaryotic cells?
THINGS IN COMMON
DIFFERENCES
Overview of a prokaryotic cell
Overview of an eukaryotic animal cell
Overview of a plant cell
Prokaryotic Vs. Eukaryotic
Both have:
1) Plasma membrane
2) Cytosol- semifluid
substance in which
organelles are found.
3) Chromosomes/genes
4) Ribosomes (tiny
organelles that make
proteins according to
instructions from the
genes)
Only eukaryotic cells:
1) Have chromosomes
inside a membrane bound
organelle- the nucleus.
“eu” = true
“karyon” = kernel
2) Are “large” -10x bigger
than bacteria.
3) Have other membranebound organelles.
FYI: CELL FRACTIONATION
Technique used to determine the function of organelles.
ORGANELLES are sub cellular structures that perform specific
sets of chemical reactions for the cell within Eukaryotic Cells.
Eukaryotic cells maintain internal membranes that
partition the cell into specialized regions.
• a. Internal membranes facilitate cellular processes by
minimizing competing interactions and by increasing
surface area where reactions can occur.
• b. Membranes and membrane-bound organelles in
eukaryotic cells localize (compartmentalize)
intracellular metabolic processes and specific
enzymatic reactions.
For example:
• Endoplasmic Reticulum
• Chloroplasts / Mitochondrion
• Golgi
• Nuclear envelope
CHARACTERISTICS
OF THE NUCLEUS:
1) Contains most of the genes*
2) Most conspicuous (big)
part of the cell
STRUCTURES of
THE NUCLEUS (out to in):
1) Nuclear envelope (double
membrane system- 2plbls)
2) Pores (protein tunnels)
3) Lamina (protein fiber
scaffolding- network)
4) Chromatin (DNA & protein)
5) Nucleolus (makes ribosomes)
*Chloroplasts and Mitochondria have their own DNA
Chromosomes are thick
coiled chromatin fibers that
condense when the cell is
ready to divide.
• Nucleosome =
subunit of a
chromosome…
• DNA wrapped
around 8 histone
proteins.
Nuclei and F-actin in BPAEC cells
Big Idea 4: Biological systems interact, and
these systems and their interactions
possess complex properties.
The structure and function of subcellular
components, and their interactions,
provide essential cellular processes.
Figure 7.10 Ribosomes
RIBOSOMES are small universal structures (proks & euks)
- made of ribosomal RNA (rRNA) and protein
- carry out protein synthesis in 2 areas
1) free- suspended in the cytosol
2) bound- attached to the outside of the endoplasmic
reticulum or nuclear envelope.
Ex. PANCREAS CELLS have a few million ribosomes
(synthesize: pancreatic juices, insulin, glucagon)
The Endoplasmic Reticulum
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“within the cytoplasm” “little net”
Labyrinth of membrane tubes and sacs
> 1/2 the total membrane of the cell
Connected to the nucleus
FUNCTIONS:
Occurs in 2 forms: rough & smooth
rough ER provides site-specific protein
synthesis with membrane-bound
ribosomes
• plays a role in intracellular transport =
endomembrane system.
• smooth ER synthesizes lipids.
Smooth ER vs. Rough ER
Smooth ER
• Lacks ribosomes
• Functions:
1) Synthesis of lipids
sex hormones, oils,
phospholipids
2) Metabolism of carbohydrates
3) Detoxification of drugs/poisons
• LIVER CELLS
• MUSCLE CELLS (store Ca+)
Rough ER
• Ribosomes attached to
the cytoplasmic surface
• Functions:
1) Protein synthesis on
ribosomes, protein enters
cisternal space to fold
into native conformation.
2) Secretory Glycoproteins
3) Phospholipid membrane
production (factory)
✘ Specific functions of smooth ER in specialized cells are
beyond the scope of the course and the AP Exam.
Golgi Complex
• STRUCTURE membranebound, consists of a series AKA: golgi apparatus, golgi bodies
of flattened membrane
sacs (cisternae).
• Looks like a smaller
version of the ER but totally
separate from nucleus)
• FUNCTIONS include
synthesis and packaging
of materials (small
molecules) for transport &
production of lysosomes.
• Receives & ships via
transport vesicles- bags
of membrane.
Golgi sorts, modifies, and exports
cis
“receiving”
trans
“shipping”
The formation and functions of lysosomes
Lysosomes are membraneenclosed sacs that contain
hydrolytic enzymes, which
are important in
1.intracellular digestion
2.The recycling of a cell’s
organic materials and
3.programmed cell death
(apoptosis)
lysosomes
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Made by rough ER, finished in the Golgi
Contain hydrolytic enzymes that function at low pH
Pumps hydrogen ions from cytosol into lysosome to maintain acidic pH
Targets of primary lysosomes are:
1) food vacuoles (formed via phagocytosis)
ex. Amoeba (protist) & Macrophages (white blood cells)
2) organelles or cytosol (autophagy- recycle materials)
3) Apoptosis = programmed destruction of cells
ex. tadpole tail, human hand development- webbing
• EX. Tay-Sachs genetic disorder is caused by missing/inactive lipid
digesting enzyme which results in lipid accumulation in brain cells.
Review: relationships among organelles of the endomembrane system
Endomembrane System
Organelles that share membrane
Components with each other.
Nuclear Envelope, ER, Golgi,
Lysosome, Vacuoles, and
Plasma Membrane
How?
Transport Vesicles- little bag of
Membrane.
Endomembrane System
Rough ER
vesicle
Golgi Apparatus
vesicle
Plasma
Membrane
The Golgi apparatus… stack of pita bread… insides = cisternae
lysosome formation
VACUOLES
• Larger than vesicles
• Food vacuoles (formed by phagocytosis)
• Contractile vacuoles- pump excess water out of
the cell (freshwater protists)
• Central vacuole- large vacuole in mature plant
cells (membrane = tonoplast)
- contains reserves of important compounds
ie. pigments (petals), metabolic by-products
(waste), poisons (repel predators), water,
proteins and lipids (seeds)
The plant cell vacuole
Which cells have the larger vacuoles- animal or plant?
plant cells
Mitochondrion / mitochondria (pl)
• Energy conversion organelle
• Site of cellular respiration
(x,y,z-->ATP)
• Mitochondrial membrane proteins
made by free ribosomes in the
cytosol
• Contain ribosomes and own DNA
• Double membrane system
- outer membrane smooth
- inner membrane convoluted
(cristae=folds) w/ proteins…
increases surface area for rxns.
• Two spaces:
1) mitochondrial matrix
(inner most area)
2) inter membrane spacebetween the two membranes.
PLASTIDS
• Family of closely related plant organelles.
• Four kinds:
1. Chromoplasts- contain pigments that give fruits
and vegetables their orange and yellow hues.
2. Leukoplasts- store starch, protein, oil
3. Amyloplasts- store starch (amylose) in roots and
tubers.
4. Chloroplasts- contain green pigment chlorophyll
& enzymes related to photosynthesis.
CHLOROPLAST
STRUCTURE
• Double membrane system
• Pancakes in a “to-go” box
• Thylakoids= flattened sacs
(inside called “thylakoid
space”
• Grana= stacks of
thylakoids
• Stroma= area outside
thylakoids and outer
membrane… contains
ribosomes, enzymes, and
chloroplast DNA.
The chloroplast, site of photosynthesis
* note: chloroplasts are larger than mitochondria.
PEROXISOMES
• Specialized, one membrane,
metabolic compartment that
detoxifies substances.
• Transfers hydrogen from
substrates to oxygen- makes
H2O2
• ie. detoxify alcohol or
• use oxygen to break fatty
acids into small molecules to
be used as fuel for the
mitochondria.
• Contains catalase to convert
H2O2 to water and Oxygen.
• Liver cells have many.
The process of evolution drives the
diversity and unity of life.
Organisms are linked by lines of descent from common
ancestry. Organisms share many conserved core
processes and features that evolved and are widely
distributed among organisms today.
Structural evidence supports the relatedness of all eukaryotes.
• Cytoskeleton (a network of structural proteins that facilitate
cell movement, morphological integrity and organelle
transport)
• Membrane-bound organelles (mitochondria and/or
chloroplasts)
• Linear chromosomes
• Endomembrane systems, including the nuclear envelope
THE CYTOSKELETON
plays a major
role in organizing
the structures and
activities of the cell
made of:
1.microtubules
2.microfilaments
3.intermediate
filaments
Table 7.2 The structure and function of the cytoskeleton
• structrure:
• hollow fibers of tubulin =
protein that makes
microtubules
- 2 types: alpha & beta
(tubulin)
• functions:
1) shape & support cellcompression resisting
2) tracks to move organelles
equipped w/motor
molecules.
3) assist in cell division
(moving chromosomes)
ex. Spindle fibers
4) motion for the cellcilia/flagella
microtubules
Figure 7.21 Motor molecules and the cytoskeleton
MICROTUBUELES
grow out of : a centrosome (plant cells)
2 centrioles w/in the centrosome in (animal cells)
centriole structure = 9 microtubule triplets in a ring
cilia & flagella:
specialized microtubular structures
• basal bodies (same structure as
centrioles) anchor cilia and flagella to
the cell membrane
• flagella = long tails (few) 10-200
micrometers
• cilia = short hairs (many) 2-20
micrometers (10-6)
• structure of both… nine pairs of
tubules arranged around 2 central
tubules (“9 + 2” pattern in Euks)
• Dynein = motor molecule (protein)
attached to tubules, uses energy
from ATP to move cilia.
• Dynein “walking” = like a cat
climbing a tree.
Figure 7.23 A comparison of the beating of flagella and cilia
cilia in action (paramecium)
microfilaments
• = threads of protein
• actin = helix shape
• twisted double chain of actin
subunits
• present in all Eukaryotic cells
• bear tension… used for
structure & movement.
• myosin = involved in
movement when interacting
with actin.
• “MA!” myosin pulls actin
muscles use actin and
myosin for contraction
myosin “pulls” actin…
myosin acts as the motor
molecule by extending
“arms”
that walk along actin.
Cell division
uses
microfilaments to
pull the cell
membrane apart
contracting band
of microfilaments
=
cleavage furrow
amoeboid movement via
pseudopodia
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pseudopod = “false foot”
cytoplasmic extensions
localized contraction of actin &
myosin move the cell membrane
reversible actin subunit
assembly
“squeezing toothpaste tube”
ex. Amoeba & white blood cells
cytoplasmic streaming
in plant cells occurs
similarly to the
movement of
pseudopods.
microfilament recap
intermediate filaments
(named for intermediate diameter)
Built from a family of proteins
called keratins
Form: permanent cellular
lattice(framework)
& cell to cell junctions
Figure 7.x4 Actin and keratin
THE CELL WALL
1) of PLANT CELLS = made of: cellulose
a)
b)
Primary wall = 1st wall to form
Middle lamella = space between two plant cells
pectin is a polysaccharide that fills the middle lamella. As fruit ripens,
pectin dissolves, cells loosen and fruit ripens
c)
Secondary wall = develops in woody plants
lignin is a molecule that strengthens the secondary wall.
2) of FUNGI = made of: chitin
3) of BACTERIA = made of organic molecules (polysaccharides &
protein)
THE CELL WALL
1) of PLANT CELLS = made of: cellulose
a) Primary wall = 1st wall to form
b) Middle lamella = space between two plant cells
pectin is a polysaccharide that fills the middle lamella.
As fruit ripens, pectin dissolves, cells loosen and fruit ripens
c) Secondary wall = develops in woody plants
lignin is a molecule that strengthens the secondary wall.
2) of FUNGI = made of: chitin
3) of BACTERIA = made of organic molecules
(polysaccharides & protein)
Figure 7.28 Plant cell walls
CELL
COATING
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Animal cell membranes have short chains of carbohydrates
bound to:
proteins (glycoproteins/proteoglycans)
ie. collagen, fibronectins, integrins
or lipids (glycolipids)
Called glycocalyx or extracellular matrix (ECM)
FUNCTIONS OF THE glycocalyx / ECM:
1. recognition sites (cell to cell for tissue formation)
2. identification markers (ie. A or B on blood cell)
3. communication (hormone messenger receptors)
cell coating/ extracellular matrix
Collagen
Proteoglycan
Polysaccharide
microfilaments
how are cells connected?
1. Intercellular matrix
2. Cell junctions
CELL TO CELL ADHESION
1) Intercellular matrix (ECMs of adjacent cells)
a) Collagen- the most abundant glycoprotein, protein fibers
that bind cells together
b) Elastin- also protein fiber that binds cells together
2) Cell junctions (permanent connections)
a) desmosomes = anchoring junctions (plaques & fibers)
“rivets”, fasten cells together in strong sheets (keratinintermediate filament)
b) tight junctions = proteins that tie cells together, leaving no
space between the cells- cells fused (ie. intestines)
c) communication junctions (2 kinds) allow flow of salt
ions, sugars, amino acids- cytoplasmic channels between
adjacent cells. (ie. heart muscle cells, cells of embryo)
1)
2)
gap junction (animal cells) membrane channels that allow
passage of material between cells.
Plasmodesmata (plant cells) openings in the cell wall where
adjacent membranes contact each other.
desmosome (anchoring junction)
(plaques & fibers)
“rivets”
fasten cells
together in
strong sheets.
keratinintermediate
filament.
tight junction
tight junctions =
proteins that tie
cells together,
leaving no space
between the
cells- cells fused
(ie. intestines)
Gap (communicating junction)
communication junctions
(2 kinds)
allow flow of salt ions, sugars, amino
acids- cytoplasmic channels
between adjacent cells.
ie. heart muscle cells, cells of embryo
1)
2)
gap junction (animal cells)
membrane channels that allow
passage of material between
cells.
Plasmodesmata (plant cells)
openings in the cell wall where
adjacent membranes contact
each other.
Figure 7.30 Intercellular junctions in animal tissues
The End