Transport across the cell membrane

Question 1

What is the cell membrane made of?

Answer 1

Phospholipids (fats) and proteins

Question 2

How can the cell membrane be described and why?

Answer 2

Fluid because the double layer of phospholipids is constantly moving

Question 3

How is the membrane structure referred to?

Answer 3

Fluid Mosaic Model

Question 4

Where are the proteins located?

Answer 4

Within the phospholipid bilayer

Question 5

What are the functions of the proteins?

Answer 5

• receptors for chemicals such as hormones or antibodies
• Carrier proteins for active transport
• Create pores in the membrane for passive transport

Question 6

Why is the membrane selectively permeable?

Answer 6

It allows small molecules like water and oxygen to freely move about, slightly larger ones like amino acids to move slowly through it and large molecules like proteins and starch are unable to pass through

Question 7

What are examples of passive methods of transport across the cell membrane?

Answer 7

Diffusion and Osmosis

Question 8

What is diffusion?

Answer 8

Diffusion is the movement of molecules or ions from a region of higher concentration to a region of lower concentration, through a selectively permeable membrane. Down a concentration gradient

Question 9

What is the purpose of diffusion?

Answer 9

It allows substances to move within a cell from one area to another, as well as allowing molecules to enter and leave a cell

Question 10

When does diffusion stop?

Answer 10

Diffusion continues until the concentration is even throughout

Question 11

Why is diffusion important for organism?

Answer 11

Oxygen and Glucose enter cells by diffusion for aerobic respiration

Question 12

What is osmosis?

Answer 12

Osmosis is the movement of water molecules from a region of high water concentration to a region of lower water concentration through a selectively a permeable membrane. Down a concentration gradient

Question 13

What is active transport?

Answer 13

The movement of molecules or ions across a cell membrane against a concentration gradient

Question 14

How are the molecules or ions moved in active transport?

Answer 14

By carrier proteins

Question 15

What provides the energy needed by active transport?

Answer 15

ATP

Question 16

If aerobic respiration is limited, how will that affect active transport?

Answer 16

It will limit the rate of active transport

Question 17

What happens if a plant cell is placed in a solution with a greater concentration than within the cell?

Answer 17

Water passes into the cell causing the vacuole to swell, Because the call wall is fairly frigid and strong enough to resist the pressure, the cell does not burst and is described as turgid

Question 18

What happens if a plant cell is placed in a solution with equal concentration to the within the cell?

Answer 18

No net gain or lost of water. The cell will remain unchanged

Question 19

What happens if a plant cell is placed in a solution with a lower concentration than within the cell?

Answer 19

Water passes out the cell to it’s surrounding, causing the vacuole to shrink and pulls the cytoplasm inwards. A gap develops between the membrane and the cell wall. The cell is described as being plasmolysed

Question 20

Why does osmosis effect plant and animal cells differently?

Answer 20

Plant cells have cell wall and a vacuole. Animal cells do not.

Question 21

What happens if an animal cell is placed in a solution with equal concentration to the within the cell?

Answer 21

No net gain or lost. The cell will remain unchanged

Question 22

What happens if an animal cell is placed in a solution with a higher water concentration than within the cell?

Answer 22

Water passes into the cell from it’s surrounding, causing the cell to swell up. As there is no cell wall it will eventually burst

Question 23

What happens if an animal cell is placed in a solution with a lower water concentration than within the cell?

Answer 23

Water passes out the cell to it’s surroundings, causing the cell to shrink and shrivel up