Ap Bio End Of Chap 6 And Chap 7

Front 1

• Components of cell wall

Back 1

o Primary cell wall→ young plant cells grow this first- its thin and flexible
o Middle lamella→ between primary walls of adjacent cells- rich in pectins (a sugar)- holds cells together
o Secondary cell wall→ between plasma membrane and primary wall
• Wood has lots of secondary cell walls
o Plasmodesmata (holes that connect plant cells together)

Front 2

• Extracellular matrix of animal cells

Back 2

mostly made of collagen which is a glycoprotein (protein covalently bonded to a carb)

o ECM connects animal cells together

o Proteoglycans→ form a network that holds the collagen fibers

o Collagen and Fibronectin→ glycoproteins that attach cells to the ECM

Front 3

o Integrins

Back 3

→ anchor collagen and fibronectin ECM fibers to the cell- found in the cell’s plasma membrane- attaches cell to the ECM
• Help the cell communicate with other cells

Front 4

Functions of ECM

Back 4

• ECM regulates cell behavior by helping cells communicate with each other

structure- holds animal cells together and improves structural stability in each cell

Front 5

• Intercellular junctions

Back 5

points of direct physical contact in cells

Plasmodesmata→ in plants
• Channels in the cell wall that connect plant cells to each other
• Cytosol passes through the plasmodesmata and connects neighboring cells


o In animal cells…
• Tight Junctions
• Membranes of neighboring cells are tightly pressed against each other
• Forms seals around cells- prevents cell leakage

• Desmosomes
• Functions like rivets- lock cells together

• Gap Junctions
• Like plasmodesmata
• Provide cytoplasmic channels from one cell to another
• Helps with intercellular communication

Front 6

• Selective permeability

Back 6

cell membrane controls what goes in and out

Front 7

what makes up cell membrane

Back 7

• Lipids and proteins make up membranes- and sometimes carbs
o Phospholipids= main type of lipid
• Phospholipids and many membrane proteins are Amphipathic molecules→ both hydrophilic and phobic
• Double layer of phospholipids make up membranes

Front 8

• Fluid mosaic model

Back 8

the membrane is a fluid structure with a mosaic of various proteins embedded in/attached to it

Front 9

Davson and Danielli

Back 9

1935

membranes are coated on both sides with hydrophilic proteins- phospholipid bilayer and two layers of proteins

Front 10

Singer and Nicolson

Back 10

1972

membrane proteins are dispersed and individually inserted into the bilayer with their hydrophilic regions pointing outwards
o Membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids

Front 11

• Freeze Fracture

Back 11

method of preparing cells for electron microscopy
o Demonstrated that proteins are embedded in the phospholipid bilayer
o Splits a membrane along the middle of the bilayer and views the embedded proteins

Front 12

Fluidity of Membranes

Back 12

• Lipids move left to right and sometimes (rarely) jump across to the other side of the bilayer


• Unsaturated phospholipids are more fluid because they don’t pack together as well b/c they’re not straight

Front 13

• Cholesterol

Back 13

lipids embedded in the membrane

serves as temperature buffer- at warm temps it restrains lipid movement and at cold temps it prevents membrane solidification

Front 14

How do plants survive in the winter?

Back 14

some plants increase number of unsaturated phospholipids in the membrane during the winter to keep the membrane from solidifying

Front 15

• Things in the membrane

Back 15

o Extracellular matrix fibers, glycoproteins, glycolipids, integral proteins, cholesterol, cytoskeleton (attaches to membrane)

Front 16

• Integral proteins

Back 16

o Penetrate the hydrophobic core of the bilayer
o Hydrophobic regions of the protein have nonpolar amino acids
o Most integral proteins are transmembrane proteins
• N terminus is on the outside of the cell
• C terminus is in the inside of the cell
• Hydrophobic region is in the alpha helix secondary structure

Front 17

• Peripheral proteins

Back 17

o Not embedded in the bilayer
o Loosely bound to the surface of the membrane

Front 18

• Six functions of proteins in membrane

Back 18

o Transport
o Enzymatic activity
o Signal transduction
o Cell to cell recognition
o Intercellular joining
o Attachment to the cytoskeleton/extracellular matrix

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o Transport

Back 19

• Provide hydrophilic channels across the membrane that are selectively permeable to particular molecules → no energy required (passive transportation?)
• Others provide transport by changing shape (they get the energy to do that through ATP)→ active transportation (energy required)

Front 20

o Enzymatic activity

Back 20

• Enzymes are embedded in the membrane
• Sometimes enzymes are arranged in a membrane in sequential order to form a metabolic pathway

Front 21

o Signal transduction

Back 21

• Helps cell communicate and interact with the outside environment
• The protein binds to certain outside molecules (like hormones for example) and sends a signal to the inside of the cell in response

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o Cell to cell recognition

Back 22

• Glycoproteins serve as identification tags that are specifically recognized by other cells

• Cell to cell recognition→ ability for a cell to distinguish one type of cell from another

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o Intercellular joining

Back 23

• Membrane proteins in adjacent cells can hook together in gap junctions or tight junctions

Front 24

o Attachment to the cytoskeleton/extracellular matrix

Back 24

• Proteins in membrane bind to cytoskeleton and ECM which helps stabilize the cell’s structure
• Also stabilizes the location of cell membrane proteins
• Proteins that adhere to the ECM coordinate extracellular and intercellular changes (communication)

Front 25

o Glycoproteins/glycolipids

Back 25

• Glycoproteins and glycolipids serve as identification tags on cells
o Glycoproteins→ carbs bonded to proteins
o Glycolipids→ carbs bonded to lipids


ex: blood type ABO reflects variations on blood cell surface proteins

Front 26

• How membrane gets built

Back 26

o 1) glycoproteins and lipids are formed in the ER
o 2) proteins/lipids are secreted in a vesicle and go to the Golgi where they undergo carbohydrate modification- glycolipids are formed in the Golgi
o 3) Transmembrane proteins, membrane glycolipids, and secretory proteins are transported in vesicles to the plasma membrane
o 4) vesicles fuse with the membrane and release secretory proteins outside of the cell- also position glycoproteins/glycolipids in the membrane


o ER and Golgi build the membrane

Front 27

what crosses easily through the membrane

Back 27

• Hydrophobic molecules like hydrocarbons, CO2, and O2 dissolve in the lipid bilayer and cross easily without the aid of membrane proteins

Front 28

what has a hard time crossing through the membrane

Back 28

• Hydrophobic core of the bilayer impedes passage of ions and polar molecules (hydrophilic things)
o Polar molecules like sugars and water do not cross rapidly
o Charged molecules have more difficulty passing through the membrane

Front 29

• Channel proteins

Back 29

o Have a hydrophilic channel that certain polar molecules and ions can pass through
o Aquaporins→ channel proteins that move water through the membrane

Front 30

• Carrier proteins

Back 30

o Hold onto the molecules that pass through and change shape in a way that shuttles the molecule through the membrane (requires energy)→ active transport

Front 31

what determines whether or not something can cross through the membrane?

Back 31

• Selective permeability of a membrane depends on whether the molecule can pass through the bilayer (which rejects polar and charged things) and/or whether the molecule can pass through a transport proteins

Front 32

• Diffusion

Back 32

tendency for molecules to spread out evenly into the available space

o Molecules diffuse across the cell membrane until the concentration inside and outside the cell is equal (reaches dynamic equilibrium)

In the absence of other forces a substance will diffuse from where it is more concentrated to where it is less concentrated

requires no work or energy- its spontaneous

Front 33

o Concentration gradient

Back 33

substances diffuse down its own concentration gradient without regard to the concentration of other substances

Front 34

• Passive transport

Back 34

diffusion of a substance across a membrane without any energy
o Concentration gradient represents potential energy that drives diffusion

Front 35

• Osmosis

Back 35

diffusion of water across a selectively permeable membrane

• Water diffuses across a membrane from the region of low solute concentration to high solute concentration

Front 36

• Tonicity

Back 36

ability of a solution to cause a cell to gain or lose water

o Solute concentration and membrane permeability influence tonicity
o Tonicity of a solution depends on its concentration of solutes that cannot cross the membrane relative to that in the cell itself
o If there are more nonpenetrating solutes in the surrounding solution the cell will lose water

Front 37

• Isotonic

Back 37

environment that’s the same as the cell’s
o Volume of an animal cell is stable in an isotonic environment b/c its at a dynamic equilibrium

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• Hypertonic

Back 38

more non penetrable solutes on the outside of the cell
o Cell loses water and will probably die
o This is why an increase in water salinity can kill fish

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• Hypotonic

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less non penetrable solute in the surrounding environment
o Cell will gain water and might swell and burst

Front 40

• Osmoregulation

Back 40

methods for helping a cell control water balance
o Animals that live in hypo or hyper tonic environments need a method of osmoregulation
o Ex: paramecium live in hypotonic environments and have a membrane that’s less permeable to water- also have contractile vacuoles that hold water and expel water when full

Front 41

Water balance in cells with Walls

Back 41

• When in hypotonic solutions the cell wall helps maintain the cell’s water balance
o The cell wall prevents the membrane from expanding too much and forces the membrane to contract when it expands too much


• When in a hypertonic solution the cell wall doesn’t help
o The plant cell will still lose water like an animal cell would and shrink and shrivel

o Plasmolysis→ when the plant cell shrivels and its plasma membrane pulls away from the wall- causes the plant to wilt and die

Front 42

• Turgid

Back 42

when the membrane is expanded so much that its pushing on the cell wall- this isn’t good for plants
o Plants with no wood rely on their cells to be turgid so they can stay upright
o If the plant is in an isotonic environment there is no net tendency for water to enter and the cell becomes Flaccid (limp)

Front 43

• Facilitated diffusion

Back 43

passive diffusion with the help of proteins
o Many transport proteins are specific to a single type of molecule

• Examples are channel proteins, aquaporins, ion channels

passive transport because the solute is moving with its concentration gradient (even though its being helped by a protein)

Front 44

• Ion channels

Back 44

channels that move ions across the membrane


o Gated channels→ stimulus causes the ion channel to open or close (like ATP Synthase)
• Many ion channels are gated channels
• If it’s a chemical stimulus it’s a chemical other than the one being transported
• Nerve cells have gated channels that respond to signals that tell the cell to let sodium ions move across the membrane

Front 45

Active transport

Back 45

uses energy to move solutes against their gradients

• Active transport moves the solute against its concentration gradient (energy needed)

• Carrier proteins carry out active transport


• Active transport lets the cell maintain internal concentrations of small molecules that differ from concentrations in its environment
• Ex: animal cells have more potassium than their surroundings and less sodium than their surroundings

Front 46

Sodium potassium pump

Back 46

example of active transport (ATP needed)

o Actively transports three Na+ ions out and two K+ ions in
o There is a net transfer of one positive charge from the cytoplasm to the outside for every “crank” of the pump
• This stores energy in the form of voltage
3:2 ratio
creates the gradient (potential energy) by pumping positive ions out of the cell

1) 3 Na+ bind to protein on inside of cell
2) ATP adds phosphate group
3) Protein releases 3 Na+ to outside of cell
4) 2 K+ bind to protein
5) Protein empties 2 K+ to inside of cell
6) Net 1 positive charge OUT

Front 47

Voltage

Back 47

• All cells have Voltage across their plasma membranes→ electrical potential energy (separation of opposite charges)
o Cytoplasm is negative because of an unequal distribution of anions and cations on opposite sides of the membrane

• Voltage across a membrane= membrane potential

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• Voltage across a membrane= membrane potential

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o Membrane potential favors the passive transport of cations into the cell and anions out of the cell

Front 49

Electrochemical gradient

Back 49

o Two forces drive ion diffusion across membrane= Electrochemical gradient
• Chemical force (ion’s concentration gradient)
• Electrical force (effect of membrane potential on ion’s movement)
o Ions diffuse down their electrochemical gradient

Front 50

• Electrogenic pump

Back 50

transport protein that generates voltage across a membrane

o Sodium potassium pump→main electrogenic pump in animals
o Proton pump→ actively transports hydrogen protons out of the cell- major electrogenic pump in plants fungi and bacteria
o Electrogenic pumps generate voltage across membranes and store energy for cellular work

Front 51

• Cotransport

Back 51

→ active transport drive by a concentration gradient

• Cotransport proteins use the energy from the natural concentration gradient of one substance to drive the active transport of another substance

Ex: plant cells use the gradient of H ions generated by its proton pumps to drive the active transport of amino acids sugars etc.

Front 52

• Exocytosis

Back 52

o Vesicles fuse with the plasma membrane and empty its contents outside of the cell
o Vesicle then becomes part of the plasma membrane

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• Endocytosis

Back 53

o Cell wraps the macromolecule in a vesicle formed by the plasma membrane
o Reverse of exocytosis

phagocytosis, pinocytosis, receptor mediated endocytosis

Front 54

o Phagocytosis

Back 54

"cell eating"

• Cell engulfs a particle by wrapping pseudopodia around it and packaging it in a vacuole- particle then gets digested by lysosomes

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o Pinocytosis

Back 55

“cell drinking”
• Cell wraps extracellular fluid in tiny vesicles
• It is not the fluid itself that the cell needs- it’s the stuff dissolved in the fluid

Front 56

o Receptor-mediated endocytosis

Back 56

• 1) Ligand (any molecule that binds specifically to a receptor site of another molecule) bind to receptor proteins in the membrane
• 2) Coated pit (area in the membrane with a fuzzy layer of coat proteins facing the inside of the cell) forms a vesicle which envelops the ligand molecules
• 3) vesicle empties the contents inside the cell and the vesicle and its proteins go back to the membrane
• Enables the cell to acquire bulk quantities of specific substances

Front 57

Crenate

Back 57

shriveling that occurs in an animal cell in a hypertonic solution

Front 58

three forces that give a group of ions potential energy (like in an ion gradient)

Back 58

positive to positive forces

positive to negative attractive forces

gradient forces

Front 59

two types of cotransport

Back 59

Countertransport- antiport protein uses the natural gradient of one ion into the cell to power the passage of another ion against its gradient (ions are moving in opposite directions)

Cotransport- Symport protein uses the natural gradient of one ion into the cell to power the passage of a molecule that otherwise can't fit through the membrane (like Glucose)--> molecules are moving the same way

Front 60

Chemiosmosis

Back 60

aka electrochemical gradient

like ATP synthase

using a gradient to harness energy

Front 61

Proton pump

Back 61

H+ ion pump

some proton pumps pump H+ ions out (with the use of ATP)

other proton pumps pump H+ ions in and use that to make ATP

other pumps use the energy from jumping electrons to power proton pumps so you net ATP instead of lose it