transport across cell membranes 1.2

Question 1

what are the 2 main components of a cell membrane

Answer 1

cell membranes are made up of 2 main types of molecule
- Phospholipids
- Proteins

Question 2

Define the phrase “selectively permeable membrane”

Answer 2

A selectively-permeable membrane is a membrane that allows only some substances and molecules to pass into or leave the cell.

Question 3

Give examples of the functions of proteins in membranes

Answer 3

Enzymes- To speed up chemical reactions inside cells
Hormone receptors- To receive and respond to specific hormone messages
Channel-forming proteins- Structural parts of a membrane that allow molecules to move across membranes
Carrier proteins- Structural parts of a membrane that are involved in the active transport of molecules across membranes

Question 4

Definition of passive transport

Answer 4

Passive transport is the movement of a substance down a concentration gradient (from an area of high concentration to low concentration) this does NOT require energy

Question 5

What does concentration gradient mean

Answer 5

A concentration gradient exists when there are 2 areas of different concentrations. The gradient refers to the difference in the 2 concentrations. the greater the difference the steeper the concentration gradient

Question 6

What are 2 names examples of passive transport process

Answer 6

• Diffusion
• Osmosis

Question 7

diffusion definition

Answer 7

Diffusion is the movement of molecules down a concentration gradient from a higher to a lower concentration

Question 8

Give examples of substances that can enter ir leave cells by diffusion

Answer 8

• Oxygen
• Carbon dioxide
• Glucose

Question 9

Explain the importance of diffusion to organisms

Answer 9

Glucose and oxygen will diffuse into cells as these are the raw materials needed for aerobic respiration

Carbon Dioxide will diffuse out of cells as this is a waste product of respiration

Question 10

what is osmosis

Answer 10

Osmosis is the movement of water molecules from a higher water concentration to a lower water concentration through a selectivley permeable membrane

Question 11

State the effects of osmosis of animal cells in diffrenet soloutions

Answer 11

• Animal cells can shrink due to osmosis
• If animal cells are placed in a solution with a higher water concentration than the content of the cells then they will gain water by osmosis and eventually burst when the cell membrsne is streached so far it ruptures
• If the animal cell is placed in a solution that has a lower water concentration than the cells then the water will move out of the cells by osmosis and the cells will shrink/crenate

Question 12

State the effects of osmosis on plant cells in different solutions

Answer 12

• Plant cells can become turgid or plasmolysed
• If the plant cells are placed in a solution with a higher water concentration than the content of the cells, then they will gain water by osmosis and the cells will swell and become turgid
• If the plant cells are placed in a solution that has a lower water concentration than the cells, then the water will move out of the cells by osmosis and the cells will become plasmolysed

Question 13

Explain the different effects of osmosis on animal cells compared to plant cells

Answer 13

• Animal cells burst when placed in a solution with a higher water concentration, but plant cells will not because of the plant cell wall prevents the cell membrane from stretching too far and bursting
  -When an animal cell loses water it shrivels yo but when a plant cell loses water its overall cell shape will not change although the cells contents will shrink and internally pull away from the cell wall as it becomes plasmolysed

Question 14

State the definition of active transport

Answer 14

Active transport is the movement of molecules and irons across the cell membrane against the concentration gradient using membrane proteins and energy

Question 15

State the role of membrane proteins in the movement of molecules/ions by active transport

Answer 15

Membrane proteins operate as carriers that pick up and transport molecules/ions from one side of the membrane where they are in low concentration and move them to the other side of the membrane where they are released into a high concentration

Question 16

Give examples of substances which move into or out of cells by active transport

Answer 16

Ions such as sodium (Na+), Potassium (k+), Chloride (cl-) Magnesium (Mg2+) move by active transport

Question 17

Compare active and passive transport in term of energy requirements

Answer 17

Active transport requires energy
Passive transport does not require energy