B4 Cell Transport Mechanisms

Question 1

What 4 things does the cell membrane consist of?

Answer 1

Proteins, glycoproteins, phospholipids, carbohydrates.

Question 2

Explain why the model for membrane structure is known as the fluid mosaic model.

Answer 2

(Fluid) The phospholipds move freely. (Mosaic) The proteins are distributed unevenly throughout the membrane. (Model) The agreed structure is based on experimental/chemical evidence.

Question 3

Which part of a phospholipid is hydrophobic?

Answer 3

The fatty acid chains that make up the tail.

Question 4

What does cholesterol do in the cell membrane?

Answer 4

Decreases permeability and increases the stability of the membrane.

Question 4

Which part of a phospholipid is hydrophilic?

Answer 4

The head.

Question 5

What are glycoproteins made up of?

Answer 5

Carbohydrate and protein.

Question 5

What is the name of the special types of channel proteins that are specific to water?

Answer 5

Aquaporins

Question 6

Name part A

Answer 6

Intrinsic protein (eg channel protein)

Question 7

Name part B

Answer 7

Phospholipid

Question 8

Name part C

Answer 8

Glycoprotein

Question 9

Name part D

Answer 9

(Hydrophilic) Polar head

Question 10

Name part E

Answer 10

Extrinsic protein

Question 11

Name part F

Answer 11

Phospholipid bilayer

Question 12

Name part G

Answer 12

Glycolipid

Question 13

Name part H

Answer 13

Carbohydrate chain

Question 14

Name part I

Answer 14

Cholesterol

Question 15

Define “Diffusion”

Answer 15

The net movement of molecules from an area of higher concentration to a lower concentration.

Question 16

How does increasing the temperature affect the rate of diffusion?

Answer 16

A higher temperature gives the molecules more kinetic energy, therefore a faster rate of diffusion.

Question 17

How does increasing the surface area affect the rate of diffusion?

Answer 17

A larger surface area provides more “space” for the molecules to pass through, therefore it is faster.

Question 18

How does increasing the concentration gradient affect the rate of diffusion?

Answer 18

As the concentration gradient increases, the rate of diffusion increases.

Question 19

Define “Osmosis”

Answer 19

Osmosis is the net movement of water molecules from a region of low solute (higher water concentration) to a region of high solute (lower water concentration) across a partially permeable membrane.

Question 20

Define “Active transport”

Answer 20

Movement of molecules from an area of lower concentration to an area of higher concentration. This requires energy/ATP.

Question 21

Name the cell transport mechanisms that are “active”

Answer 21

Active transport. Bulk transport (exocyctosis and endocytosis)

Question 22

Name the cell transport mechanisms that are “passive”

Answer 22

Simple diffusion, facilitated diffusion, osmosis.

Question 23

How does glucose move into cells? Why is it this mechanism?

Answer 23

Facilitated diffusion. Glucose is a large, polar molecule.

Question 24

How does oxygen move into cells? Why is it this mechanism?

Answer 24

Simple diffusion. Oxygen is a small, non-polar molecule that can dissolve in the bilayer.

Question 25

How do lipid soluble molecules move into cells? Why is it this mechanism?

Answer 25

Simple diffusion. The molecule dissolves in the fatty acid tails.

Question 26

How do potassium ions move into cells? Why is it this mechanism?

Answer 26

Facilitated diffusion. It’s a small, charged ion.

Question 27

As an organism increases in size, what happens to the surface area to volume ratio?

Answer 27

The surface area to volume ratio decreases.

Question 28

Calculate the surface area to volume ratio of a cube that has a side length of 5cm.

Answer 28

1.2:1

Question 29

Explain why the cell membrane is selectively/partially permeable.

Answer 29

The carrier proteins are specific to a substance.

Question 30

Define “Facilitated diffusion”.

Answer 30

Facilitated diffusion is a passive process where molecules move down a concentration gradient (from a higher to lower concentration) using a carrier/channel protein.

Question 31

What happens to an animal cell if it is placed in a solution with a lower solute concentration?

Answer 31

Water moves into the animal cell, causing it to swell. The cell could burst (lysis) and its contents would be lost.

Question 32

What happens to an animal cell if it is placed in a solution with a higher solute concentration?

Answer 32

Water moves out of the cell, resulting in the cell shrivelling. Mass would be lost.

Question 33

What happens to an animal cell if it is placed in an isotonic solution?

Answer 33

The is no net movement of water into or out of the cell. There would be no change in mass.

Question 34

What happens to a plant cell if it is placed in a solution with a lower solute concentration?

Answer 34

Water will move into the cell, and it would swell. The cellulose cell wall prevents lysis.

Question 35

What happens to a plant cell if it is placed in a solution with a higher solute concentration?

Answer 35

Water would move out of the cell. The plant cell membrane would pull away from the cell wall (plasmolysed)

Question 36

How are exchange surfaces in animal adapted to maximise effectiveness?

Answer 36

Thin membrane - so a short diffusion distance. Large surface area - so a lot of a substance can diffuse at once. Good blood supply - to maintain the concentration gradient (by moving materials in and out of the blood quickly)

Question 37

During exocytosis a cell moves large quantities of molecules ………. the cell.

Answer 37

out of

Question 38

During endocytosis a cell moves large quantities of molecules ………. the cell.

Answer 38

into