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Biology mod 2 Foundations in biology > 2.1.5 Biological membranes > Flashcards

2.1.5 Biological membranes Flashcards

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1
Q

Function of cell surface membrane

A

Regulates the movement of substances into and out of the cell. It also has receptor molecules on it, which allow it to respond to chemicals like hormones.

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2
Q

What is the structure of the cell surface membrane?

A

Phospholipid bilayer

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3
Q

Phospholipid bilayer made up of:

A

Phospholipids
Cholesterol
Glycoproteins and glycolipids
Transport proteins

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4
Q

How do phospholipids form a bilayer?

A

Hydrophilic heads attract water and have hydrophobic trails which repel water. This means the molecules automatically arrange themselves into a bilayer

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5
Q

Function of cholesterol in cell surface membrane.

A

Increases fluidity of membrane at low temps and increases stability at high temps

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6
Q

How does cholesterol stop the membrane from being too rigid?

A

Stops phospholipid tails binding too closely together

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7
Q

How does cholesterol stop the membrane from being too fluid at high temperatures?

A

Binds to the tails.

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8
Q

What molecule makes up the chains attached to the surface of glycolipids and glycoproteins?

A

Carbohydrate.

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9
Q

What is the function of the carbohydrate chains attached to glycolipids and glycoproteins?

A

Allows them to act as receptor molecules.

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10
Q

Two types of transport proteins.

A

Channel and carrier proteins.

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11
Q

What is the permeability of cell membrane affected by?

A

Temperature and solvent concentration.

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12
Q

How does temperature impact the permeability of the cell membrane?

A

As temperature increases, lipids become more fluid and so it reduces the effectiveness of the membrane as a barrier.

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13
Q

How do very high temperatures impact the permeability of the cell membrane?

A

At very high temps proteins will denature which disrupts the membranes structure and so molecules can freely pass into the membrane. This is irreversible.

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14
Q

How does solvent concentration affect the permeability of the cell membrane?

A

Organic solvents can increase cell membrane permeability as they dissolve the lipids in the membrane.

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15
Q

Define diffusion

A

The net movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient.

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16
Q

Factors affecting diffusion

A

Steepness of concentration gradient.

Temperature

Surface area

Size of molecules

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17
Q

How does the steepness of the concentration gradient affect the rate of diffusion?

A

The greater the concentration of gradient, the faster the rate of diffusion. If there are more molecules on one side of the membrane than the other,molecules will move across the membrane from that side

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18
Q

How does temperature affect the rate of diffusion?

A

The higher the temperature, the faster the rate of diffusion. This is because the particles have more kinetic energy so they move around faster.

19
Q

How does surface area affect diffusion?

A

The greater the surface area, the greater the rate of diffusion. This is because more molecules and ions can cross it.

20
Q

How does the size of molecules affect the rate of diffusion?

A

Large molecules will diffuse more slowly as they require more energy to move.

21
Q

What are channel proteins?

A

Transport proteins that have a hydrophilic channel that certain molecules/ions use as a tunnel through the membrane.

22
Q

What are carrier proteins?

A

transport proteins that bind to molecules and change shape to shuttle them across the membrane.

23
Q

Define osmosis

A

The net movement of water molecules through a partially permeable membrane from a region of a high water potential to a region of a low water potential.

24
Q

What is water potential?

A

The tendency of water to move out of a soloution.

25
Q

What is the water potential of pure water?

A

0kPa

26
Q

Any solution that has solutes in it will have a higher or lower water potential than pure water?

A

Lower

27
Q

If an animal cell is placed in a solution with a lower water potential than the cell then what will happen?

A

Water will leave through its membrane and the cell will shrink and shrivel up.

28
Q

What is crenation?

A

animal cell shrivels up

29
Q

What is a hypertonic environment?

A

when concentration of solutes outside the cell is higher than inside the cell.

30
Q

If an animal cell is placed in pure water what will happen?

A

Water will enter through the membrane by osmosis. The cell will continue to gain water until it bursts.

31
Q

What is cytolysis?

A

The bursting of a cell

32
Q

What is an isotonic environment?

A

when there is the same concetration of solutes inside and outside the cell. There will be no transport of water.

33
Q

Is the effect of water potential more severe in plant or animal cells? Why?

A

More severe in animal cells as they do not have a cell wall.

34
Q

What happens if a plant is placed in a solution withs lower water potential than the plant cell?

A

Water will leave the plant cell so the protoplast shrinks and no longer exerts pressure on the cell wall. The plant cell has plasmolysed.

35
Q

What is the bulk transport into cells called?

A

endocytosis

36
Q

What is the bulk transport out of cells called?

A

exocytosis

37
Q

Do endocytosis and exocytosis require energy?

A

Yes, both require ATP

38
Q

Two types of endocytosis

A

phagocytosis and pinocytosis

39
Q

What is phagocytosis?

A

The bulk intake of solid material.

40
Q

What is pinocytosis?

A

The bulk intake of liquid.

41
Q

What is exocytosis?

A

Process by which materials are transported out of cells in secretory vesicles.

42
Q

Define active transport?

A

The movement of molecules and ions across a cell membrane from a region of a lower concentration to a region of higher concentration using energy from respiration.

43
Q

what is diffusion involving transport proteins called?

A

Facilitated diffusion

44
Q

Name some molecules that can cross plasma membranes?

A

Water
CO2
Oxygen

Biology mod 2 Foundations in biology (6 decks)

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