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Biology AS > Biological Membranes, 2.5 > Flashcards

Biological Membranes, 2.5 Flashcards

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1
Q

What is a partially permeable membrane?

A

Separates the cell and regulates substances moving in an out.

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2
Q

What is the role of the plasma membrane?

A

Regulate molecules. Separate. Contains enzymes. Antigens. Release chemicals. Contains receptors.

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3
Q

What is the phospholipid bilayer?

A

Consists of two layers of phospholipids. Hydrophilic heads in contact with water. Hydrophobic tails point inwards.

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4
Q

What proteins would you find in the plasma membrane?

A
  1. Channel proteins - allow ions through
  2. Carrier proteins - specific, change shape
  3. Receptors - recognise and bind to molecules
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5
Q

How thick is plasma membrane?

A

5 - 10 nm

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6
Q

What is glycolax?

A

Formed from carbohydrates attached to lipids or proteins.

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7
Q

What is the role of glycolipids?

A

On external surfaces. Cell to cell recognition.

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8
Q

What is cholesterol and why is it in the plasma membrane?

A

Steroids. Regulates fluidity.

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9
Q

Define diffusion

A

Molecules moved from an area of high concentration to an area of low concentration down a concentration gradient. No energy required.

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10
Q

What can pass through the plasma membrane by diffusion?

A

Oxygen, carbon dioxide, small substances - fat soluble can dissolve through

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11
Q

What can’t pass through the plasma membrane?

A

Water - polar and insoluble. Have to use water channel proteins. Molecules with charges and large molecules

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12
Q

What effects diffusion?

A

Temperature - more kinetic energy. Distance. Surface area. Size of molecules.. Concentration gradient.

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13
Q

What molecules will use facilitated diffusion?

A

Molecules with charges (ions) - use channel proteins. Larger molecules (glucose) - use carrier proteins.

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14
Q

How does a channel protein work?

A

Pores in the membrane. On type of molecule. Water filled.

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15
Q

How does a carrier protein work?

A

Molecule binds to transmembrane carrier protein. Protein changes shape so molecules can pass through. Specific.

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16
Q

Define osmosis

A

Movement of water molecules from a region of higher water potential to an area of lower water potential. Down a water potential gradient. Across a partially permeable membrane.

17
Q

What is water potential?

A

Measure of the tendency of water molecules to diffuse from one region to another.

18
Q

What is ‘free’ water?

A

Water thats not bound to any substance.

19
Q

What has the highest water potential/

A

Pure water

20
Q

What is a solute?

A

Substance that can be dissolved

21
Q

What is a solvent?

A

Liquid that solutes dissolve in

22
Q

What is a solution?

A

Solute dissolved in a solvent

23
Q

Is osmosis passive or active?

A

Passive

24
Q

What factors effect osmosis?

A

Temperature. Water potential difference. Pressure. Concentration gradient.

25
Q

What can be dissolved in cells?

A

Sugars and salts

26
Q

What happens when a plant cell has lots of water?

A

It is turgid. Cell wall prevents it from bursting.

27
Q

What happens when a plant cell loses water?

A

Cytoplasm shrinks and membrane pulls away from the cell wall. Described as plasmapheresis or flaccid.

28
Q

What happens when animal cells are full of water?

A

Cell will swell and burst - cytolysis

29
Q

What happens when animal cells lose water?

A

Shrivels - crenated

30
Q

What is active transport?

A

Movement of substances against their concentration gradient with ATP

31
Q

How is a carrier protein involved in active transport?

A

Specific regions to allow molecules through. Has regions that bind to ATP to release energy.

32
Q

What is bulk transport?

A

Transport large substances through the membrane using ATP

33
Q

What is endocytosis?

A

Large molecule into the cell. Segment of membrane encloses a particl bringing it into a vesicles.. ATP is needed

34
Q

What is exocytosis?

A

Large molecules out of the cell. Vesicles fusses with plasma membrane

35
Q

How does temperature affect the membrane?

A

Molecule gain energy - fluidity increase. Permeability increases. Effects function of embedded proteins. Change the ability of cells to signals

36
Q

Effect of decreasing the temperature on the membrane?

A

Fatty acids are compressed. Unsaturated fats push phospholipids away with their tails maintaining fluidity. Cholesterol prevents phospholipids from packing to closely together.

37
Q

What will organic solvents such as acetone and ethanol do to the membrane?

A

Damage it. Dissolve the lipids.

Biology AS (12 decks)

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