1.3 Transport in cell membranes

Question 1

What are the principle components of the plasma membrane?

Answer 1

• Intracellular and extra cellular proteins.
• Glycoproteins.
• Phospolipids
• Chloresterol

Question 2

What is the fluid-mosaic model?

Answer 2

A model that describes membrane structure as a ‘sea’ of mobile phospolipids studded with various proteins.

Question 3

What are intrinsic proteins?

Answer 3

Proteins found within the phospolipid bilayer.
Included channel and carrier proteins.

Question 4

Outline the functions of intrinsic proteins.

Answer 4

• Structural support.
• Carry water-soluble molecules accross the phospolipid bilayer.
• Form ion channels to enbale active transport.

Question 5

What are extrinsic proteins?

Answer 5

Proteins found at the edges of the phospolipid bilyer.

Question 6

Outline the functions of extrinsic proteins.

Answer 6

• receptors
• Act as antigens, enabling cell recognition.
• Helps cells to adhere to eachother.

Question 7

What is the glyocaxyl?

Answer 7

A glycoprotein and glycolipid coating surrounding the cell membrane of some cells.

Question 8

Name the factors affecting the permability of the plasma membrane

Answer 8

• Temperature
• pH
• Organic solvenents.

Question 9

How does temperature effect the permability of the plasma membrane?

Answer 9

• As temperature increases,the phospolipids have more kinetic energy and move more, increasing the fluidity and permeability of the plasma membrane.

Question 10

What happens to the plasma membrane if the temperature becomes too high?

Answer 10

• Channel and carrier proteins will become denatured, affecting membrane permability.
• The cell will eventually break down completely.

Question 11

How do organic solvents affect the permability of plasma membranes?

Answer 11

• Organic solvents dissolve membranes, disrupting cells. This increases fluidity and permability of the plasma membrane.

Question 12

Define diffusion

Answer 12

The passive movement of small non-polar lipid-soluble molecules from an area of high concentration to an area of low concentration.

Question 13

State the factors that effect the rate of diffusion.

Answer 13

• Temperature
• Steepness of the concentration gradient,
• Size of molecule
• Diffusion distance
• Surface Area

Question 14

Define osmosis

Answer 14

The passive diffusion of molecules from a region of high water potential to a region of lower water potential down a water potential gradeint accross a selectively permeable membrane.

Question 15

What is water potential?

Answer 15

A measure of tendancy of water molecules to move from one area to another.

Question 16

What is incipient plasmolysis?

Answer 16

• The effect produced by placing plant cells in a isotonic solution.
• Causes the cell membrane to pull away from the cell wall in some areas
• The cell is neither turgid or plasmolysed.

Question 17

Define facilliated diffusion

Answer 17

The net movement of substances from a high concentration to a low concentration down their concentration gradient, through transport proteins with the use of energy.

Question 18

Give an example of facilliated diffusion

Answer 18

Co-transport.

Question 19

Define active transport

Answer 19

The movement of substances from a low concentration to a higher concentration against the concentration gradient, hrough carrier proteins, with the use of energy in the form of ATP.

Question 20

How does cyanide affect active transport?

Answer 20

Cyanide inhibts cytochrome oxidase, stopping the production of ATP. This prevents active transport.

Question 21

What are the 2 mechanisms of bulk-transport?

Answer 21

• Endocytosis
• Exocytosis

Question 22

Define endocytosis

Answer 22

The bulk uptake of substances into a cell by invagination of the cell membrane to form a vesicle. Uses energy in the form of ATP.

Question 23

State the 2 types of endocytosis.

Answer 23

• Pinocytosis
• Phagocytosis

Question 24

What is pinocytosis?

Answer 24

• The bulk uptake of liquids into the cell using energy in the form of ATP.

Question 25

Whatis phagocytosis?

Answer 25

• The bulk uptake of solids into the cell usning energy in the form of ATP

Question 26

Define exocytosis

Answer 26

The bulk uptake of substances out of a cell via a vesicle, taht fuses with the plasma membrane. Uses enrgy in the form of ATP