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AP Biology > Cell Membrane > Flashcards

Cell Membrane Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

The cell membrane can be described as a _____ _______ model”

A

fluid mosaic

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2
Q

Why is the cell membrane called a fluid mosaic model?

A

it has fluid with a mosaic of proteins

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3
Q

Describe the phospholipid bilayer

A

phosphate head, lipid tail

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4
Q

Define amphipathic

A

a molecule that’s hydrophobic and hydrophilic

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5
Q

Define semi-permeable

A

allows only some materials through

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6
Q

_____ __________ _______ can dissolve in the lipid bilayer

A

Small nonpolar molecules

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7
Q

Give an example of small nonpolar molecules

A

hydrocarbons

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8
Q

_____ ______ _________ do not

cross the membrane easily

A

large polar molecules

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9
Q

Give an example of large polar molecules

A

sugars

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10
Q

What is a freeze-fracture?

A

a specialized preparation technique that splits a membrane along the middle of the phospholipid bilayer

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11
Q

How does the cell membrane maintain fluidity?

A

The phospholipids constantly trade places from side to side. Every once in a while they will trade with a phospholipid from the other layer.

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12
Q

High temperatures cause ____ movement, lower temperatures cause ____.

A

more; less

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13
Q

Describe cholesterol

A

a steroid hormone found in membranes to help maintain fluidity

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14
Q

Where are integral proteins located?

A

they go through the whole membrane

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15
Q

Where are peripheral proteins located?

A

they sit on the outside of the membrane (inside of the cell).

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16
Q

Cell membrane proteins do what six main things?

A
  1. Transport materials in and out
  2. Act as Enzymes
  3. Pass signals
  4. Identify other cells
  5. connect to other cells
  6. attach the cytoskeleton to the ECM fibers
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17
Q

How to carbohydrates aide cell recognition

A

Carbohydrates can bond to the lipids (glycolipids) or more often proteins (glycoproteins) in the membrane by protruding from the membrane.

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18
Q

Define passive transport

A

requires no energy

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19
Q

Define simple diffusion

A

molecules move from an area of higher concentration to lower concentration

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20
Q

In simple diffusion, molecules move ____ their concentration gradient

A

down

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21
Q

Simple diffusion occurs until occurs until what happens?

A

equilibrium is reached

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22
Q

Define osmosis

A

diffusion of water molecules thru a selectively permeable membrane

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23
Q

Osmosis moves molecules from ____ to ____ water concentration

A

high; low

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24
Q

the force exerted by osmosis is called _______ _________

A

osmotic pressure

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25
Q

Define hypertonic solution

A

more dissolved material in solution than in the cell

26
Q

What happens into a cell in a hypertonic solution?

A

water flows out of the cell and the cell shrivels up

27
Q

Define hypotonic solution

A

more dissolved material in the cell than in the solution

28
Q

What happens to a cell in a hypotonic solution?

A

water flows into the cell and increases osmotic pressure. the cell may burst

29
Q

Define isotonic solution

A

same amount of dissolved material in the solution and cell

30
Q

What happens to a cell in a isotonic solution?

A

equilibrium is reached

31
Q

Animal cels prefer which type of solution?

A

isotonic

32
Q

Plant cells prefer which type of solution?

A

hypotonic

33
Q

Define osmoregulation

A

control of water balance

34
Q

Why don’t cells burst?

A 
-cells in organisms don’t 
usually come into contact 
with pure water 
-plant cells have cell walls 
that keep the cell from 
expanding
-some cells use pumps
35
Q

Describe facilitated diffusion

A

diffusion with the assistance of integral transport proteins (Still Passive transport)

36
Q

What do channel proteins do?

A

allow certain materials to flow in and out (down their concentration gradient.)

37
Q

What is a aquaporin?

A

channel protein that only lets water in

38
Q

What are ion channels

A

also called gated channels, open and close in response to a chemical or electrical stimulus

39
Q

What do carrier porteins do?

A

change shape to escort certain material in and out of the cell

40
Q

Define active transport

A

Proteins act as pumps to move material from low to high concentration

41
Q

The proteins that act as pumps in active transport are called what?

A

electrogenic pumps

42
Q

Active transport requires _______

A

energy

43
Q

What does the Sodium-Potassium pump do?

A

pumps sodium out and potassium in. (low to high concentration)

44
Q

What does a electrochemical gradient do?

A

moves the ions across the membrane like an electric current to do work

45
Q

How does a electrochemical gradient work?

A

Pumps create a build up of ions on either side of the membrane, which creates an electric charge. The charge causes an electrochemical gradient

46
Q

Define cotransport

A

electrochemical gradient used to move other molecules across the membrane

47
Q

Define endocytosis

A

a vesicle formed to take materials into the cell

48
Q

Define exocytosis

A

a vesicle putting materials out of the cell

49
Q

What are the 3 types of endocytosis?

A
  1. Phagocytosis
  2. Pinocytosis
  3. Receptor mediated endocytosis
50
Q

Describe phagocytosis

A

engulfing solid particles

51
Q

Describe pinocytosis

A

engulfing liquid substances (extracellular fluid)

52
Q

Describe receptor mediated endocytosis

A

particles called ligands bind to receptors, which signals the engulfing of the particles.

53
Q

What is the difference between channel proteins and carrier proteins?

A

Solutes diffuse through the pore of channel proteins, whereas carrier proteins bind solutes on one side of membrane and release it on the other side. Also, carrier proteins have very slow transport rates.

54
Q

How is membrane fluidity influenced by membrane composition?

A

Membranes must be fluid to work properly. Saturated fats (ex: butter) make it “stiff” because they are solid at room temperature. Unsaturated fats (oil) helps it “bend” which helps the cell work better - liquid at room temperature

55
Q

How does cholesterol resist changes in membrane fluidity with temperature change?

A

Cholesterol at moderate temperature reduces membrane fluidity by reducing phospholipid movement, but at low temperatures, it hinders solidification by disrupting the regular packing of phospholipids.

56
Q

Define tonicity

A

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

57
Q

Define turgid

A

buildup of water in a cell that makes the cell swollen.

58
Q

If a plant cell is flaccid, it is in a __ environment

A

isotonic

59
Q

If a plant cell is turgid, it is in a __ environment

A

hyptonic

60
Q

What can speed up the process of osmosis?

A

the presence of aquaporin.

61
Q

Active transport uses energy to move solutes __ their gradients

A

against

62
Q

Explain how large molecules are transported across a cell membrane.

A

Through a process called endocytosis, in which molecules enter cells within vesicles that pinch inward from the plasma membrane.

AP Biology (38 decks)

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