Biological Membranes, 2.5

Question 1

What is a partially permeable membrane?

Answer 1

Separates the cell and regulates substances moving in an out.

Question 2

What is the role of the plasma membrane?

Answer 2

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

Question 3

What is the phospholipid bilayer?

Answer 3

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

Question 4

What proteins would you find in the plasma membrane?

Answer 4

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

Question 5

How thick is plasma membrane?

Answer 5

5 - 10 nm

Question 6

What is glycolax?

Answer 6

Formed from carbohydrates attached to lipids or proteins.

Question 7

What is the role of glycolipids?

Answer 7

On external surfaces. Cell to cell recognition.

Question 8

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

Answer 8

Steroids. Regulates fluidity.

Question 9

Define diffusion

Answer 9

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

Question 10

What can pass through the plasma membrane by diffusion?

Answer 10

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

Question 11

What can’t pass through the plasma membrane?

Answer 11

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

Question 12

What effects diffusion?

Answer 12

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

Question 13

What molecules will use facilitated diffusion?

Answer 13

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

Question 14

How does a channel protein work?

Answer 14

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

Question 15

How does a carrier protein work?

Answer 15

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

Question 16

Define osmosis

Answer 16

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.

Question 17

What is water potential?

Answer 17

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

Question 18

What is ‘free’ water?

Answer 18

Water thats not bound to any substance.

Question 19

What has the highest water potential/

Answer 19

Pure water

Question 20

What is a solute?

Answer 20

Substance that can be dissolved

Question 21

What is a solvent?

Answer 21

Liquid that solutes dissolve in

Question 22

What is a solution?

Answer 22

Solute dissolved in a solvent

Question 23

Is osmosis passive or active?

Answer 23

Passive

Question 24

What factors effect osmosis?

Answer 24

Temperature. Water potential difference. Pressure. Concentration gradient.

Question 25

What can be dissolved in cells?

Answer 25

Sugars and salts

Question 26

What happens when a plant cell has lots of water?

Answer 26

It is turgid. Cell wall prevents it from bursting.

Question 27

What happens when a plant cell loses water?

Answer 27

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

Question 28

What happens when animal cells are full of water?

Answer 28

Cell will swell and burst - cytolysis

Question 29

What happens when animal cells lose water?

Answer 29

Shrivels - crenated

Question 30

What is active transport?

Answer 30

Movement of substances against their concentration gradient with ATP

Question 31

How is a carrier protein involved in active transport?

Answer 31

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

Question 32

What is bulk transport?

Answer 32

Transport large substances through the membrane using ATP

Question 33

What is endocytosis?

Answer 33

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

Question 34

What is exocytosis?

Answer 34

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

Question 35

How does temperature affect the membrane?

Answer 35

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

Question 36

Effect of decreasing the temperature on the membrane?

Answer 36

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

Question 37

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

Answer 37

Damage it. Dissolve the lipids.