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AS Biology > Cell membranes > Flashcards

Cell membranes Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What does water soluble mean?

A

Something that can dissolve in water

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2
Q

Define diffusion.

A

Movement of particles from an area of concentration to an area of low concentration.

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3
Q

What type of process is diffusion?

A

Passive

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4
Q

Define facilitated diffusion.

A

Passive transfer of molecules or ions down a concentration gradient, across a membrane, by protein carrier molecules in the membrane.

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5
Q

What is the job of the cell membrane?

A

To control what goes in and out of a cell

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6
Q

Give 4 things the rate of diffusion is affected by.

A

Concentration gradient
Thickness of the exchange surface
Size of the diffusing molecule
Nature of the diffusing molecules

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7
Q

Describe how channel proteins move molecules across a membrane.

A

The channel opens to allow the molecules to move through and into a cell. When a state of equilibrium is reached, the channel protein gate will close up, allowing no more molecules or ions through.

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8
Q

Where does the process active transport get its energy from?

A

ATP

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9
Q

Anything that affects……..will affect active transport. Why?

A

Respiration, because ATP (the fuel for active transport) is produced through the process of respiration.

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10
Q

What one thing is the rate of active transport limited by?

A

The number and availability of carrier proteins

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11
Q

What is the highest value that water potential can have?

A

0

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12
Q

What is endocytosis?

A

The process where material outside the cell is engulfed and brought into the cell in a vesicle

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13
Q

What are the two types of endocytosis?

A

Phagocytosis

Pinocytosis

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14
Q

What is exocytosis?

A

Substances leaving the cell after being transported through the cytoplasm in a vesicle.

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15
Q

What does hydrophilic mean?

A

When something is attracted to water molecules

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16
Q

What does hydrophobic mean?

A

Something that does not mix with water and is attracted to lipids

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17
Q

What is created when phospholipids are mixed with water?

A

A phospholipid bilayer

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18
Q

Why is the phospholipid bilayer a suitable arrangement?

A

Because the hydrophilic heads will be in contact with the water and the hydrophobic tails won’t be

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19
Q

What is an extrinsic protein?

A

One that is only found on the inner or outer layer of the phospholipid bilayer

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20
Q

What is an intrinsic protein?

A

One that spans the whole of the phospholipid bilayer

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21
Q

What molecules can pass easily through the membrane? Why?

A

Lipid soluble substances, because the phospholipid bilayer is hydrophobic so lipid soluble molecules move through more easily than water soluble molecules.

22
Q

How do water molecules pass through the membrane?

A

They pass through intrinsic molecules, which form water filled channels across the membrane

23
Q

Which transportation processes do not require energy from the cell?

A

Diffusion

Facilitated diffusion

24
Q

How do you work out the rate of diffusion?

A

Surface area X difference in concentration / length of the diffusion path

25
Q

Does facilitated diffusion occur up or down s concentration gradient?

A

Down

26
Q

What are the two types of transport proteins?

A

Channel proteins

Carrier proteins

27
Q

Describe channel proteins and how they work?

A

The channels are hydrophilic. Channels open and close according to needs of the cell.

28
Q

Describe carrier proteins and how they work.

A

Allow diffusion of larger molecules. A molecule attaches to its binding site, carrier protein changes shape and releases the molecule on the other side of the membrane.

29
Q

How may temperature affect the permeability of a membrane?

A

Higher temps disrupt the phospholipid membrane
Proteins forming specific channels denature
Things can then diffuse across the damaged membrane and out of the cell

30
Q

Define active transport.

A

The movement of molecules or ions across a membrane against a concentration gradient, using energy from the hydrolysis of ATP made by the cell in respiration.

31
Q

Describe co-transport.

A

A type of facilitated diffusion and active transport. One carrier protein can carry two different molecules. The molecules have to move at the same time but can move in different directions.

32
Q

What type of process is co-transport?

A

Both active and passive

33
Q

What type of process is active transport?

A

Active

34
Q

What does solute potential measure?

A

How easily water molecules move out of a solution

35
Q

What is the water potential of pure water?

A

0

36
Q

State some effects of osmosis on a cell.

A

Builds up outward pressure on cell wall through the vacuole filling up
Entry of more water resisted
Cell becomes turgid

37
Q

How do you work out the water potential of a cell?

A

By adding the pressure potential and the solute potential

38
Q

What does hypotonic mean?

A

When the water potential outside the cell is less negative (higher) than inside the cell. Water flows into the cell.

39
Q

What does hypertonic mean?

A

When the water potential outside the cell more negative (lower) than inside the cell. Water flows out of the cell.

40
Q

What does isotonic mean?

A

If the cell has the same water potential as the surrounding solution, the external solution and cell are isotonic and there will be no net water movement.

41
Q

Describe plasmolysis.

A

When a cell loses water by osmosis, the vacuole shrinks and the cytoplasm draws away from the cell wall. When the process is complete, the cell is flaccid.

42
Q

What does flaccid mean?

A

Floppy

43
Q

What happens to a plant when it’s’ cells are flaccid? Why?

A

The plant wilts because the cells cannot provide any support for the plant

44
Q

Why is turgid mess important to plants?

A

Because it provides support, maintains their shape and holds them upright.

45
Q

Is the pressure potential value positive or negative?

A

Positive

46
Q

What is phagocytosis?

A

When a cell takes in a solid material that is too large to move in by diffusion or active transport.

47
Q

How does phagocytosis work?

A

A lysosome fuses with the vesicle carrying the material and enzymes in the lysosome digest the solid material. The products are then absorbed into the cytoplasm.

48
Q

What is pinocytosis?

A

The entry of smaller materials, such as liquids, into the cell by the same mechanism as phagocytosis.

49
Q

Give an example of something that may need to leave the cell through exocytosis.

A

Proteins made by the cell

50
Q

What does the fluid mosaic model show?

A

The way in which phospholipids and proteins are arranged

51
Q

Give two reasons why the fluid mosaic model has the name it does.

A

Individual phospholipid molecules can move within the bilayer. The proteins embedded in the bilayer vary in shape, size and pattern.

AS Biology (7 decks)

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