Cell Structures and Transport

Question 1

Define passive transport

Answer 1

The movement of substances from a high to low concentration

Question 2

Define diffusion

Answer 2

A type of passive transport where substances move from a high to low concentration

Question 3

What type of substances move by diffusion?

Answer 3

Gases - oxygen and carbon dioxide

Question 4

Define osmosis

Answer 4

A type of passive transport. The movement of water across a selectively permeable membrane from a high to low water concentration

Question 5

How do we lower the concentration of water?

Answer 5

Increase the concentration of dissolves solutes e.g. sugar, salt

Question 6

Define facilitated diffusion

Answer 6

A type of passive transport. The movement of larger molecules across a selectively permeable membrane from a high lo low concentration

Question 7

What type of molecules move by facilitated diffusion?

Answer 7

Large molecules e.g. glucose

Question 8

Define active transport

Answer 8

The movement of molecules from a low to high concentration

Question 9

Describe two ways passive and active transport are different

Answer 9

Passive is from high to low concentration and active is from low to high
Active requires energy in the form of ATP but passive does not

Question 10

A cell/plasma membrane has two main parts - what are they?

Answer 10

Lipid bi-layer and protein pores/channels

Question 11

How does carbon dioxide and oxygen move through a cell/plasma membrane?

Answer 11

By diffusion through the lipids bi-layer because they are small molecules and can fit through the small gaps in the lipid bilayer

Question 12

How does water move across a cell/plasma membrane?

Answer 12

By osmosis through the lipid bi-layer because it is small enough

Question 13

How does glucose move across a cell/plasma membrane?

Answer 13

By facilitated diffusion. Carrier proteins transport the glucose through protein channels/pores in the cell/plasma membrane

Question 14

In photosynthesis, what substances move into a cell , how and why?

Answer 14

Carbon dioxide moves into the cell through the lipid bi-layer by diffusion. Because carbon dioxide is used up in photosynthesis in the chloroplast, it is always in a lower concentration inside the cell compared to outside the cell
Water moves in the cell across the lipid bi-layer by osmosis. Same reason as above

Question 15

In photosynthesis, what substances move out of a palisade cell, how and why?

Answer 15

Glucose moves out of the cell by facilitated diffusion through the protein pores/channels. Glucose is made in photosynthesis inside the chloroplast so it is always in a higher concentration inside the cell compared to outside.
Oxygen moves out of the cell through the lipid bi-layer by diffusion. Same reason as above

Question 16

How do root cells take up ions from the soil?

Answer 16

Initially by diffusion as the concentration of those ions is higher in the soil than inside the cell. Once the concentrations are the same, the cell has to take up more ions by active transport against the concentration gradient. this requires energy in the form of ATP

Question 17

Describe similarities between osmosis and diffusion

Answer 17

Both types of passive transport

• both involve molecules moving from high to low to low concentration
• both do not require energy in the form of ATP

Question 18

Describe differences between osmosis and diffusion

Answer 18

Osmosis is the movement of water whereas diffusion is the movement of general substances
Osmosis is the movement across a selectively permeable membrane whereas diffusion could be across a membrane or within a cell for example (doesn’t need to involve a membrane)

Question 19

Describe similarities between osmosis and facilitated diffusion

Answer 19

Both involve substances moving from high to low concentration
Both don’t require energy in the form of ATP
Both involve movement across a selectively permeable membrane

Question 20

Describe differences between osmosis and facilitated diffusion

Answer 20

Facilitated diffusion is the movement of large molecules e.g. glucose whereas osmosis is specifically the movement of water
Facilitated diffusion requires carrier proteins and they move through the protein channels/pores of the cell membrane whereas water moving by osmosis goes through the lipid bilayer and doesn’t need carrier proteins

Question 21

Describe similarities between active transport and passive transport

Answer 21

Both involve the movement of molecules

Question 22

Describe differences between active transport and osmosis

Answer 22

Osmosis is the movement of water whereas active transport tends to be ions and larger substances
Osmosis is the movement from high to low but active transport is low to high concentration
Osmosis doesn’t require energy in the form of ATP but active transport does