Download Chapter 6-7 - Sarah Mahajan Study Guides

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Chapter 6
Levels of Organization
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Biosphere
Biome
Ecosystem
Community
Population
Organisms
Organ systems
Organs
Tissues
 Cell- basic unit of life
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Organelles
Molecules
Atoms (basic unit of matter)
5 Kingdoms of Life
1)
2)
3)
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Animals
Plants
Protists
Fungi
Bacteria
Prokaryotes vs. Eukaryotes
All cells are bounded by a plasma membrane which encloses a semifliud medium called cytosol. All cells
contain chromosomes and ribosomes.
Prokaryotes
Eukaryotes
-Bacteria
*No membrane bound nucleus
-Nucleoid: the DNA of prokaryotic cells is
concentrated in this region – in single loops
*No organelles
-Protist
-Fungi
-Animal
-Plant
*Has a membrane-bound nucleus
*Has organelles
Cell Theory
1) The cell is a basic unit of life.
2) Cells come from preexisting cells.
3) All living things are made of cells.
-Robert Hooke = main contributor to the cell theory
-Rudolf Virchow, Matthew Schleiden, Theodore Schawnn, Robert Brown = scientists in the early
1800s whose ideas all contributed to Cell Theory
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Spontaneous generation/abiogenesis is the idea that life comes from nonliving things. This idea existed
until Louis Pasteur discovered that there are microbes in the environment that causes things to spoil.
The idea that exists today is biogenesis, the idea that life comes from living things.
Cytosol is the watery basis in which organelles are suspended in; it’s also the interior of a prokaryote cell
Cytoplasm is cytosol + organelles
The plasma membrane surrounding every cell must provide sufficient surface area for exchange of
oxygen, nutrients, and wastes relative to the volume of the cell
-Small cell size is due to geometry and the requirements of metabolism
-The smaller the cell, the bigger the surface area to volume ratio
-Smaller cells are more beneficial:
1) More efficient diffusion of nutrients
2) More reproduction and healthier cells
3) Better chances of survival
The Structure of the Cell
Organelle and Function
Cell type
Location
Nucleus – contains instructions for making proteins
Eukaryote
Within cytosol,
usually centrally
located
Nuclear envelope- double membrane of phospholipids
and proteins surrounding the nucleus
Nuclear pores- small pores in the nuclear envelope that
regulate the exchange of materials between the
cytoplasm and the nucleus (DNA stays; RNA leaves)
Chromosomes- contain and carry genetic information in Eukaryote and
the form of DNA; it’s chemistry is DNA
prokaryote
Chromatin- material consisting of DNA and proteins
used for wrapping and packaging the DNA.
Chromosomes are wrapped around histone proteins.
Individual chromosomes are only visible in a dividing
cell.
In an eukaryote
cell: in the nucleus
in single strands
In a prokaryote
cell: in the
nucleoid in a
single loop
DNA- the nucleic acid that makes up chromosomes
Gene- more specific bits of genetic information
Nucleoid- a region where the cell’s genes are located
Prokaryote
on a single loop chromosome; same chemistry of DNA,
but not a membrane-bound nucleus like eukaryotic cells
In the cytosol
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Nucleolus- contains RNA that is used to make
ribosomes; not membrane bound so it will disperse and
“disappear” during meiosis and then recollect
Eukaryote
In the nucleus
Ribosomes- manufacture proteins; made of rRNA and
proteins; made of 2 parts= large subunit and small
subunit
Eukaryote and
prokaryote
Free in the cytosol
or bound to the
rough ER and
nuclear
membrane
Eukaryote
Continuous with
the nuclear
membrane
Eukaryote
Continuous with
nuclear
membrane; in
cytosol
-Free ribosomes = make proteins that are used inside of
the cell; float free in the cytosol
-Bound ribosomes= make proteins that are included
within membranes, packaged into organelles, or
secreted and used outside of the cell, like hormones
and antibodies; bound to rough ER or nuclear envelope
*Where the primary structure of proteins is made
Rough Endoplasmic Reticulum- modifies polypeptides
by folding and coiling them into their normal shape
(secondary shape); has ribosomes
-Attaches carbohydrate chains (glycoprotein) which act
as markers or signals telling the protein where to go
-The packaged proteins leave the ER through vesicles
(and go to the Golgi Apparatus)
-It also manufactures membranes for the cell. Enzymes
built into the membrane assemble phospholipids, and
membrane proteins formed by bound ribosomes are
inserted into the ER membrane. Transport vesicles
transfer ER membrane to other parts of the cell.
*Where the secondary structure of proteins is made
Smooth Endoplasmic Reticulum- has 4 major functions:
1) Synthesis of lipids (phospholipids and steroids)
2) Metabolism of carbohydrates in the liver
3) Detoxification of drugs and poisons, like
alcohol, aspirin, and antibiotics (Drugs increase
the liver’s production of smooth ER, leading to an
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increased tolerance of these and other drugs)
4) Stores calcium ions in muscle cells (which is
called the sarcoplasmic reticulum)
Transport vesicles- membrane-bound sacs that pinch
off the Golgi apparatus and transport substances
outside of the cell; ID tell the vesicles where to go
Eukaryote
Pinch off
membranes
Eukaryote
In cytosol, further
away from
nucleus
-Vesicles also pinch off from the ER and integrate into
the cis face of the Golgi apparatus, transporting
secretory proteins or ones for the membrane
Golgi apparatus- products of the ER are further
modified, stored, and shipped to other destinations
1) Carbohydrate chains are removed or
substituted
cis face- “receiving”
side where vesicles
from the ER join
2) Secretes specific polysaccharides in plant cells
(like pectin)
trans face3) Products are sorted by adding phosphate
groups as ID tags
“shipping side”
where vesicles
pinch off and leave
*Where the tertiary and quaternary structure is made
Lyosomes – membrane-enclosed sacs containing
hydrolytic enzymes which speed up hydrolysis
(breaking down and digesting macromolecules);
Lysosomes provide an acidic pH for these enzymes.
Eukaryote- only
in animal cells
In cytosol
-Can be involved in:
1. Autodigestion- cells digest themselves
2. Apoptosis- programmed cell death (Example:
tadpoles are broken down and used to form
new cells in the form of frogs )
3. Phagocytosis- white blood cell engulfs food
into a food vacuole which fuses with lyosomes
and breaks it down
4. Autophagy- engulfs its own damaged
organelles
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Contractile vacuole- pump out excess water from
freshwater protists so they don’t lyse (=burst)
Eukaryoteprotists, plants,
fungi
Central vacuole with tonoplast (water vacuole)–
surrounded by a vacuolar membrane (=tonoplast);
stores organic compounds and inorganic ions; holds
water and dissolves materials until it’s full of water  it
exerts turgor pressure, pushing the membrane against
the cell wall and increasing the cell size
Eukaryotes –
plants, fungi,
some protists
In cytosol
*Turgor pressure causes plants to become turgid, rigid,
and expanded
Mitochondria- carry out cellular respiration and
produces ATP; has a folded double membrane, with
DNA and ribosomes that direct the synthesis of proteins
C6H12O6 + O2  H2O + CO2 + ATP (energy)
Choloroplasts- carry out photosynthesis and produce
glucose; has a stacked double membrane; contain
chlorophyll
6H2O + 6CO2  C6H12O6 + 6O2
Eukaryotes
In cytosol
(prokaryotes carry
out cellular
respiration, but
don’t use
mitochondria)
Eukaryotes –
plants, algae,
and some
protists
In cytosol
Prokaryotes and
Eukaryotes
(plants, fungi,
and some
protists)
Outer layer of the
cell (outside the
cell membrane)
Eukaryotes
Extends
throughout the
cytoplasm
*Allows organisms to manufacture their own food
Cell wall- provides structure and support; maintains cell
shape and protects the cell from mechanical damage;
made of cellulose, other polysaccharides, and proteins
Plant cell walls = cellulose
Fungi = chitin
Bacteria = peptidoglycan (sticky material made of protein
and sugar)
Cytoskeleton – network of protein fibers that consist of
different sizes
Functions:
1) Reinforces the cell’s shape lk;kaf;lksjfla;sldkfja;slda;s
2) Transmits signals from the cell’s surface to its interior
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3) Organizes cell’s structures and activities and helps to
move organelles within cells by interacting with motor
proteins
*Cytoplasmic streaming is when the cytoskeleton
directs the movement of the cytoplasm by providing
the tracts. It’s more efficient in smaller cells
Microtubules – larger protein fibers that make up the
cytoskeleton; example = centrioles in animal cells
Eukaryotes
In the
cytoskeleton
Microfilaments – smaller protein fibers that make up
the cytoskeleton
Eukaryotes
In the
cytoskeleton
Extracellular matrix- made of protein fibers and
carbohydrates; is the “glue” that holds cells together
Eukaryotes
Outside of the cell
(between cells)
Plasmodesmata- channels within plant cells that allow
connections between adjacent cells (water, small solutes,
Eukaryotes –
Between cells
*plasmodesmata (they all help hold
are only in
cells together)
plants
*Actin and Myosin are important microfilaments in
muscle proteins
and proteins and RNA can move throughout these channels)
Tight junction- where cell membranes are tightly
pressed together; creates a continuous seal that
prevents leakage
Desmosomes (anchoring junctions)- fastens cells
together in strong sheets
*the 3 junctions
are only in
animal cells
Gap junctions (communicating junctions)- provides
cytoplasmic channels and allows communication
between cells
Cilia – shorter; numerous
Flagella – long; usually single
Eukaryotes and
prokaryotes
Outside cell,
found in
reproductive cells
Cell’s job = to make proteins
-Plasma membrane- controls transport of materials in/out of the cell
-Endomembrane system- consists of the nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles,
and the plasma membrane.
-The ER encloses a network of interconnected tubules or sacs called cisternae.
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-As membranes move from the ER to the Golgi and then to other organelles, their compositions,
functions, and contents are modified
*These membranes are all related through direct contact or by the transfer of membrane
segments by the membrane-bound sacs called vesicles
-Mitochondria = makes ATP
-Chloroplasts = makes glucose in plants
Endosymbiant Hypothesis
-Eukaryotes came about from bacteria that have ingested other bacteria, where the ingested bacteria
became mitochondria and chloroplasts
-Both mitochondria and chloroplasts have double membranes and their own DNA
-mDNA = mitochondrial DNA that always comes from maternal DNA
Animal cells vs. Plant cells
Animal cells:
Plant cells:
-Lysosomes (suicide sacs)
-Centrioles (move chromosomes)
-Flagella (in some plant sperm)
-Chloroplasts (make glucose  can make their
own food)
-Central vacuole and tonoplast (get rid of excess
water)
-Cell wall (provide structure and support)
-Plasmodesmata (hold plant cells together)
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Chapter 7
 The plasma membrane is selectively permeable, allowing some materials to cross it more easily
than others and enabling the cell to maintain a unique internal environment
Cell Membranes are fluid mosaics of lipids and proteins
-According to the fluid mosaic model, the structure of membranes consists of various proteins
embedded in a phospholipid bilayer
-The structure of all membranes is similar
Cell Fluidity
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Membranes are held together primarily by weak hydrophobic interactions that allow the lipids and
some of the proteins to drift laterally
-Some membrane proteins seem to be held rigid by attachments to the cytoskeleton; others
appear to be directed in their movements by cytoskeletal fibers
Phospholipids with unsaturated hydrocarbon tails maintain membrane fluidity at lower
temperatures
-The double bonds in the unsaturated fatty acid chains create a kink in the molecule, so it’s fluid,
not fixed
The steroid cholesterol can be embedded in the membrane which also adds fluidity to the cell
-It prevents the close packing of lipids and enhances fluidity at lower temperatures
-Cholesterol is common in plasma membranes of only animals
-However, at WARMER TEMPERATURES, it restricts movement of phospholipids and reduces
fluidity
Transport Proteins
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Integral proteins extend throughout the entire membrane
-Also called transmembrane proteins
-Have 2 hydrophilic ends and a hydrophobic midsection that consists of one or more alpha
helical stretches of hydrophobic amino acids
Peripheral proteins attached to the surface of the membrane, often to integral proteins
-Attachments of these membrane proteins to the cytoskeleton or extracellular matrix provide a
supportive framework for the plasma membrane
Membrane Carbohydrates
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Act as cell markers and cell receptors and help cells distinguish other cells
The glycolipids and glycoproteins attached to the outside of plasmamembranes vary from cell to cell
-Glycoproteins are proteins with a glucose chain attached to it
-Glycolipids consist of a glucose chain attached to a lipid
Synthesis and Sidedness of Membranes
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Membranes have distinct inner and outer faces, related to the composition of the lipid layers, the
directional orientation of their proteins, and their attachment of carbohydrates to the extracellular
surface
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Carbohydrates are attached to membrane proteins as they are synthesized in the ER and are
modified in the Golgi. Carbohydrates are also attached to lipids in the Golgi.
-When transport vesicles fuse wit the plasma membrane, these interior glycoproteins and
glycolipids become located on the extracellular face of the membrane
Membrane structure results in selective permeability
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The plasma membrane permits a regular exchange of nutrients, waste products, oxygen, and
inorganic ions.
Biological membranes are selectively permeable; the ease and rate at which small molecules pass
through them differ
The Permeability of the Lipid Bilayer
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Hydrophobic, nonpolar molecules, such as hydrocarbons, CO2, and O2, can dissolve in and cross a
membrane
Transport Proteins
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Ions and polar molecules may move across the plasma membrane with the aid of transport proteins
Functions of membrane proteins:
o Transport
-moving materials across the membrane
-can be either passive or active
o Enzymatic activity
-something binds to a protein outside and causes a change inside the cell
o Signal transduction
-something binds to a protein outside and causes a series of changes inside cell
o Cell-cell recognition
-some glycoproteins serve as ID tags that are recognized by other cells
o Intercellular joining
-membrane proteins of adjacent cells make attach in various kinds of junctions
o Attachment to the cytoskeleton and ECM
-Proteins attached to cytoskeleton = maintain internal support
-Proteins attached to the ECM = coordinate extracellular changes
 2 types of transport proteins:
1. Channel proteins – have a hydrophilic channel that certain molecules can enter and use
as a tunnel
a. Aquaporins = channel proteins that facilitate the passage of water
2. Carrier proteins- physically binds and transports a specific molecule and can change
shape
-It’s a more specific type of transport across the membrane
What determines how a molecule moves through the membrane?
Passive transport:
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High concentration to low concentration
With the concentration gradient
No cellular energy
Uses the kinetic energy of molecules
3 types of passive transport:
1) Diffusion- the movement of a substance down its concentration gradient due to random
thermal motion
-The diffusion of one solute is unaffected by the concentration gradients of other
solutes
-The cell doesn’t expand energy when substances diffuse across membranes
-small, hydrophobic molecules like N2, O2, CO2, CO move through the membrane
by diffusion
-small uncharged molecules like glycerol, ethanol, and ether move through the
membrane by diffusion
2) Osmosis- the diffusion of water across a selectively permeable membrane
-water diffuses down its own concentration gradient, which is affected by the solute
concentration
-When there is more solute particles, more water molecules bind to them. This
lowers of water that’s free to cross the membrane
-water diffuses through the membrane by osmosis, with the help of aquaporins
3) Facilitated diffusion- diffusion across the membrane with the help of transport proteins,
either channel or carrier proteins
-Many ion channels are gated channels, which open or close in response to
electrical or chemical stimuli
-small polar molecules like glucose, amino acids, and nucleotides diffuse through
the membrane with the help of proteins
Small hydrophobic molecules
Small uncharged molecules
Passive
Transport
Water (through aquaporins)
Small polar molecules
Channel protein
Small, highly charged particles (ions)
Carrier protein
(aka protein pump)
Active
Transport
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Active transport:
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Low concentration to high concentration
Against the concentration gradient
Requires ATP
Uses transmembrane proteins
4 types of active transport:
1) Proton pump
-moves H+ ions across the membrane through carrier proteins
-An H+ ion is a proton
-transport within an organelle, like cellular respiration
2) Cotransport
-Transporting 2 solutes across the membrane when the active transport of a 2nd solute is
indirectly driven by the ATP-powered pump that drives the transport of the 1st
-For example:
-H+ ions move out of the cell through a protein.
-This changes the pH, making the extracellular fluid more acidic, and creates an
electrochemical gradient. A change in pH can change protein shape.
-H+ ions then diffuse back in, but now sucrose molecules can move in as well,
through proteins that changed shape.
3) Sodium-potassium pump
-Exchanges Na+ (sodium ion) for K+ (potassium ion) across the plasma membrane of
animal cells
-This transport involves ATP and special proteins that can change shape
-This is how it works:
-Na+ ions move through a protein  When ATP binds to the protein in order to
help the Na+ ions go through, the protein changes shape (the shape that
matches K+ ions)
-Now K+ ions can go through the membrane.  When ATP binds to the protein
in order to help the K+ ions go through, the protein changes shape again (the
shape that matches Na+ ions)
-Now Na+ ions can go through the membrane again.
-It creates a higher concentration of potassium ions and a lower concentration of sodium
ions within the cell.
-It creates membrane potential, a voltage difference across a membrane due to
unequal distribution of positive and negative ions.
-An ion diffuses down its electrochemical gradient, which is created by charged
particles moving across the membrane.
4) Receptor-mediated endocytosis
-A specific type of endocytosis: brings in specific macromolecules that have to bind with
receptors on the inside of the membrane in order to be transported
-Doesn’t use proteins, but does use ATP
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Bulk transport across the plasma membrane occurs by exocytosis and
endocytosis
Bulk transport requires ATP to transport larger biological molecules, packaged in vesicles, across the
membrane. But it doesn’t use proteins.
Exocytosis
-In exocytosis, the cell brings out and secretes large molecules by the fusion of vesicles with the
plasma membrane
Endocytosis
-Endocytosis is when the cell takes in molecules by forming vesicles from the plasma membrane
-A region of the plasma membrane sinks inward and pinches off to form a vesicle that
contains materials that had been outside the cell
-3 types of endocytosis:
1) Phagocytosis = cellular eating (bringing in solids)
-The vesicle then fuses with lysosomes containing hydrolytic enzymes in order
to be digested
2) Pinocytosis = cellular drinking (bringing in liquids)
3) Receptor mediated endocytosis (see above)
Hypertonic and Hypotonic
Hypertonic solution: high solute, low water
Hypotonic solution: low solute, high water
Isotonic solution: the same amount of solute
-Protists like paramecium are often hypertonic to their environment. (This means that they have less
water and more solute compared to their environment)
-The direction of water movement is from high to low, so water diffuses from the outside to the
inside of the cell.
-However, Paramecium will not burst because they have contractile vacuoles that can pump out
excess water
Onion Cell:
Cell wall
Cell membrane
Water vacuole
Nucleus
96% water
Hypertonic
Environment: distilled
water ( 100%) = Hypotonic
Water flows in
An onion cell placed in a hypotonic environment is hypertonic relative to
its environment  water flows in
-The cell membrane is pressed against the cell wall
*It was high turgor pressure, so the cells are turgid and rigid.
-Only cells with cell walls can have turgor pressure
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96% water
Hypotonic
Environment: 15% solute
(85% water) = Hypertonic
Water flows out
An onion cell placed in a hypertonic environment (higher solute, lower water) is hypotonic
(lower solute, higher water) relative to its environment.  water flows out
-The cell membrane shrivels and shrinks
-The cell loses turgor pressure
**This is called plasmolysis: the loss of cytoplasm and water from the cell
 Can cause plants to wilt and die
Red blood cell:
If placed in distilled water:
-The red blood cell would be hypertonic relative to its environment which would be hypotonic
(It would have more solute and less water than distilled water.)
-So water would flow INTO the cell.
-Red blood cells are animal cells, so they do not have a cell wall.  If too much water flows in,
the red blood cell would lyse, or burst and explode.
If placed in 15% solute:
-The red blood cell would be hypotonic relative to its environment which would be hypertonic
(It would have less solute and more water than its environment.)
-So water would flow OUT of the cell.
-If too much water flows out, the red blood cell would shrivel up and die.
Tonicity
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Tonicity is the tendency of a cell to gain or lose water and is affected by the relative concentrations
of solutes that cannot cross the membrane in the solution and in the cell
Isotonic solution:
-An animal or a plant cell will neither gain nor lose water in an isotonic environment
-A plant cell in an isotonic environment is flaccid.
Hypertonic solution:
-An animal cell will gain lose water and shrivel.
-A plant cell undergoes plasmolysis, the pulling away of the plasma membrane from the cell wall
as water leaves and the cell shrivels.
Hypotonic solution:
-An animal cell will gain water, swell, and possibly lyse (burst).
-A plant cell will gain water, swell against its cell wall, and become turgid.
-Turgid cells provide mechanical support for nonwoody plants
Cells without rigid walls must either live in an isotonic environment, such as salt water or isotonic
body fluids, or have adaptations for osmoregulation, the control of water balance.
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