A1 Cell Membranes And Transport

Question 1

What do phospholipids consist of?

Answer 1

Two hydrophobic fatty acid chains and a phosphate group which is hydrophilic joined together by a glycerol.

Question 2

What can phospholipids form?

Answer 2

A phospholipid bilayer, cell membranes are made up of this

Question 3

What do cell membranes consist of?

Answer 3

Hydrophilic heads, hydrophobic tail, cholesterol, intrinsic protein, extrinsic protein, glycolipid, glycoprotein

Question 4

Membranes are… P… P…

Answer 4

Partially permeable

Question 5

What does the fluid mosaic model describe?

Answer 5

The arrangement and movement of the molecules that make up a cell membrane.

Question 6

What does fluid describe in the fluid mosaic model?

Answer 6

Fluid- phospholipids (and proteins) are free to move sideways

Question 7

What does mosaic describe in the fluid mosaic model?

Answer 7

Proteins have a scattered arrangement within the bilayer

Question 8

What is a phospholipid?

Answer 8

A lipid molecule that has a polar, hydrophilic head and a non polar, hydrophobic tail. They form the main component of cell membranes.

Question 9

What is the role of cholesterol in a cell membrane?

Answer 9

Fluidity and stability

Question 10

What are glycolipids?

Answer 10

Phospholipids with carbohydrates attached

Question 11

What is the role of glycolipids?

Answer 11

Cell signaling and direction

Question 12

What is the role of intrinsic proteins in the cell membrane?

Answer 12

Some act as carriers to transport water- soluble molecules across the membrane. Others act as enzymes.

Question 13

What is the role of extrinsic proteins in the cell membrane?

Answer 13

Cell signalling, cell recognition, enzymes receptors

Question 14

What is the role of membranes within cells?

Answer 14

Compartementalisation:
1. separate organelles content from cell cytoplasm 2. provides large surface area for aerobic respiration 3. contains digestive enzymes 4. where some reactions take place

Question 15

What is the role of membranes on the surface of cells?

Answer 15

1. separate cells components from external environment 2. transport of materials 3. contain enzymes for reactions 4. has antigens to recognise cells as their own 5. receptors for chemical signals

Question 16

Describe the cell signalling process

Answer 16

1. one cells releases a messenger molecule e.g a hormone 2. this molecule travels to another target cell e.g in the blood
2. the messenger molecule is detected by the cell because it binds to the receptor on the target cell’s cell membrane 4. the cell then responds to the messenger molecule by a change in activity

Question 17

Describe diffusion

Answer 17

The passive movement of molecules from an area of high concentration to an area of low concentration across a partially permeable membrane through a phospholipid bilayer

Question 18

Factors that can affect the rate of diffusion?

Answer 18

Temperature, concentration gradient, surface area, thickness of exchange area

Question 19

What is the type of molecule that can diffuse through the bilayer?

Answer 19

Lipid soluble ones, small and non polar molecules e.g oxygen, very small polar molecules e.g water

Question 20

Describe facilitated diffusion

Answer 20

The passive net movement of substances from an area of high concentration to an area of low concentration down a concentration gradient across the membrane via carrier or channel proteins

Question 21

What are channel proteins?

Answer 21

Proteins that provides corridors that allows a specific molecule or ion to cross the membrane

Question 22

What are carrier proteins?

Answer 22

A protein that transports substances across a cell membrane

Question 23

Factors affecting the rate of facilitated diffusion

Answer 23

The concentration gradient, temperature, the number of channel or carrier proteins

Question 24

What is exocytosis?

Answer 24

The process by which a substance is released from the cell through a vesicle that transports the substance to membrane to let the substance out

Question 25

What is osmosis?

Answer 25

The movement of water from an area of higher water potential to an area of lower water potential, down a water potential gradient across the phospholipid bilayer

Question 26

What is active transport?

Answer 26

The active movement of ions or polar molecules from a lower concentration to a higher concentration using a carrier protein. This movement against the concentration gradient requires energy from ATP.

Question 27

What are the types of molecules that are actively transported by carrier proteins?

Answer 27

Large, polar molecules, ions

Question 28

What could inhibit active transport?

Answer 28

Anything that inhibits respiration and therefore ATP production e.g cyanide

Question 29

Describe endocytosis

Answer 29

A process in which a cell takes material into the cell by infolding of the cell membrane

Question 30

What is phagocytosis?

Answer 30

A type of endocytosis and is how white blood cells called phagocytes engulf and digest bacteria.