Module 2.5

Question 1

Role of membranes within cells

Answer 1

partially permeable membrane between organelles and the cytoplasm
sites of chemical reactions

Question 2

Role of membranes at the surface of cells

Answer 2

Partially permeable membrane between the cell and its environment
Sites of chemical reaction
Site of cell communication/signalling
Regulates transport of materials in and out of the cell
Has antigens so the cell is recognised as self

Question 3

What is the fluid mosaic model

Answer 3

phospholipid molecules make up the main part of the membrane
They are fluid as the can move in any way they want as long as the hydrophobic tails are not exposed
Has other molecules(mainly proteins) as well making up the mosaic

Question 4

Types of molecules in the plasma membrane

Answer 4

Phospholipids, cholesterol, glycoproteins, channel proteins, carrier proteins and glycolipids

Question 5

Role of glycoproteins

Answer 5

Used in cell signalling
Act as antigens

Question 6

Role of glycolipids

Answer 6

cell to cell communication
Receptors

Question 7

Role of cholesterol

Answer 7

Regulates the fluidity of the membrane
mechanical stability
Flexibility

Question 8

Role of carrier proteins

Answer 8

Used in active transport
Molecule goes in the top of the protein it then ATP is used to create a conformational change in shape to transport molecules into and out of the cell

Question 9

Role of channel proteins

Answer 9

Used in facilitated diffusion
Create water filled channels in the membrane for small ions to pass through the membrane

Question 10

Effect of temperature on membrane permeability

Answer 10

Increasing temperature increases permeability as the molecules are moving around more
Denature proteins in the membrane
In lower temperature unsaturated fatty acids and cholesterol prevent a reduction in fluidity

Question 11

Effect of solvents on membrane permeability

Answer 11

Break the membrane down increasing permeability by creating holes or fully dissolving it

Question 12

What is diffusion

Answer 12

The movement of molecules from an area of high concentration to an area of low concentration
Passive process

Question 13

What is facilitated diffusion

Answer 13

Channel proteins create a channel in which small ions can move through the membrane
Passive process

Question 14

What is active transport

Answer 14

The movement of molecules from an area of low concentration to an area of high concentration
Requires ATP as an immediate source of energy
Active process

Question 15

What is endocytosis

Answer 15

The movement of large molecules into a cell
The plasma membrane is extended to surround the molecule it then fuses around the molecule creating a vesicle containing the molecule
Active process (requires ATP to move the plasma membrane and vesicle)

Question 16

What is exocytosis

Answer 16

The releasing of a molecule from a cell
A vesicle travels to the plasma membrane, fuses with it to open the vesicle releasing the molecule into the environment
Active process (requires ATP to move the plasma membrane and vesicle)

Question 17

What is osmosis

Answer 17

The movement of water across a partially permeable membrane from an area of high water potential to an area of low water potential

Question 18

Effect of high water potential solution around plant and animal cells

Answer 18

water moves into the cell
animal cells - cell swells and becomes lysed if too much water moves in as there is no cell wall
Plant cells - cells become turgid as the cell wall prevents bursting

Question 19

Effect of low water potential solution around plant and animal cells

Answer 19

Water moves out of the cells
Animal cells - cell becomes crenated
Plant cells - Plasma membrane pulls away from cell wall cell is plasmolysed