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Cells > Cell Membranes > Flashcards

Cell Membranes Flashcards

1
Q

Name the current model of the membrane.

A

Fluid mosaic.

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1
Q

Why is the cell membrane described as fluid?

A

The membrane moves as a result of individual phospholipid molecules that move relative to each other, therefore it is flexible.

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2
Q

Why is the membrane described like a mosaic?

A

Due to the components such as proteins embedded in it, it makes it look like a mosaic.

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3
Q

Name 3 ways substances can cross the cell membrane.

A

Diffusion
Osmosis
Active transport

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4
Q

Describe the structure of a phospholipid.
Name the bonds in a phospholipid.

A

Polar phosphate head attached to a glycerol which is bonded to 2 non polar fatty acids. The bond is called an ester bond.

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5
Q

How do phospholipids act in the presence of water?

A

The polar phosphate head is hydrophillic so it attracts to water.
The non polar fatty acid tails is hydrophobic so it repels water.

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6
Q

Describe how the cell membrane is arranged.

A

Arranged into a phospholipid bilayer where hydrophilic heads point outwards and hydrophobic tails point inwards.

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7
Q

Why can water diffuse through the cell membrane despite being polar?

A

It is very small.

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8
Q

Why is oxygen and carbon dioxide able to diffuse through the cell membrane?

A

They are small and uncharged.

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9
Q
A
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9
Q

Describe the solubility of phospholipids in water.

A

Phosphate head is soluble.
Fatty acid tails are insoluble.

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10
Q

How do phospholipids arrange when mixed/shaken in water?

A

They form micelles which are small lipid droplets where the hydrophilic heads point outwards and hydrophobic tails point inwards.

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11
Q

What is an intrinsic protein?

A

A protein embedded in the membrane.

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12
Q

What is an extrinsic protein?

A

A protein that is found on the inner or outer surface of the cell membrane.

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13
Q

What is a carrier protein?

A

A protein that spans across the membrane. The molecule binds to the protein which changes shape to push it across the membrane.

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14
Q

Active transport relies on which protein?

A

Carrier proteins.

15
Q

Why do carrier proteins require ATP?

A

The ATP is needed to change the shape of the carrier protein.

16
Q

Name 2 molecules that use carrier proteins.

A

Glucose
Amino acids.

17
Q

What are channel proteins?

A

Proteins that span the whole membrane that create ‘channels’ for water soluble ions to move across.

17
Q

What are channel proteins filled with?

A

Water.

18
Q

Why are channel proteins selective to specific ions?

A

Due to their highly complex tertiary structure.

19
Q

Facilitated diffusion relies on which 2 types of protein?

A

Carrier proteins
Channel proteins

20
Q

How can channel proteins control how much of substance diffuses at a time?

A

The ends of the channel can open and close.

21
Q

What do ions do to the channel protein before they can diffuse across the membrane?

A

They bind to the end of the channel protein.

22
Q

What is a glycoprotein?

A

A protein molecule with a carbohydrate chain attached

23
Q

Why are glycoproteins important for cell recognition?

A

Prevents our own cells from being attacked.

24
Q

Describe how glycoproteins are involved with hormones and neurotransmitters.

A

Glycoproteins act as receptor sites.

25
Q

How do glycoproteins allow tissues to be formed?

A

They help cells to attach to eachother.

26
Q

What are glycolipids?

A

Lipids with a carbohydrate chain attached.

27
Q

The carbohydrate on a glycolipid extends out into where?

A

The watery environment outside the cell.

28
Q

How do glycolipids allow tissues to be formed?

A

They help cells to attach.

29
Q

How are glycolipids similar to glycoproteins in terms of their function? (3 ways)

A

They act as recognition sites
They help cells to attach and form tissues.
They act as receptor sites for hormones and neurotransmitters.

30
Q

Describe hydrophilic/hydrophobia in cholesterol.

A

Hydrophobic tails, hydrophilic heads.

31
Q

Which type of organism are cholesterol molecules absent in?

A

Prokaryotes

32
Q

How does cholesterol reduce the fluidity of the cell membrane?

A

They pull fatty acid tails of neighbouring phospholipids closer together which limits their movement.

33
Q

How does cholesterol benefit the cell membrane at higher temperatures?

A

It reduces the rigidity of the membrane which stops it losing its structure.

34
Q

Give 4 uses of cell membranes.

A

Keeps organelles inside the cell.
Site for biochemical reactions.
Allows the cytoplasm to split into compartments.
Allows cells to change shape.

Cells (15 decks)

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