Transport in Cells (1.3) (M)

Question 1

What is diffusion?

Answer 1

The spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration (across a cell membrane)

Question 2

2 examples

What are some examples of diffusion?

Answer 2

• oxygen and carbon dioxide in gas exchange
• the waste product urea from cells into the blood plasma for excretion in the kidney

Question 3

3 factors needed

What are factors which affect the rate of diffusion?

Answer 3

• the difference in concentrations (concentration gradient)
• the temperature
• the surface area of the membrane.

Question 4

What is the surface area:volume ratio of a single-celled organism like?

Answer 4

A single-celled organism has a relatively large surface area to volume ratio.

This allows sufficient transport of molecules into and out of the cell to meet the needs of the organism.

Question 5

Why is exchanging materials with the environment more difficult in multi-cellular organisms than in single-celled organisms?

What do they have in response to this?

Answer 5

due to their smaller surface area:volume ratio

so multi-cellular organisms have specialised organ systems for exchanges and transport systems to carry materials around the body

Question 6

Why do multicellular organisms have specialised surfaces and organ systems for exchanging materials?

Answer 6

to allow sufficient molecules to be transported into and out of cells for the organism’s needs

Question 7

4 ways

Which factors increase the effectiveness of an exchange surface?

Answer 7

• having a large surface area
• a membrane that is thin, to provide a short diffusion path
• (in animals) having an efficient blood supply
• (in animals, for gaseous exchange) being ventilated.

Question 8

What is osmosis?

Answer 8

Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.

Question 9

What is active transport?

Answer 9

the movement of substances from an area of low concentration to an area of high concentration (against a concentration gradient). This requires energy from respiration.

Question 10

What is an example of active transport in plants? Why is this useful?

Answer 10

Active transport allows the absorption of mineral ions into plant root hairs from very low concentrations in the soil.

Plants require ions for healthy growth.

Question 11

What is an example of active transport in the body? Why is this useful?

Answer 11

It allows sugar molecules to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration.

Sugar molecules are used for cell respiration

Question 12

5 points

How are the small intestines adapted for efficient absorption?

Answer 12

Villi (projectiles) provide a large surface area

villi are one cell thick for shorter absorption/diffusion distance

small intestine is very long, increasing time for absorption

good/efficient blood supply to maintain concentration gradient

cells have many mitochondria for energy release for (aerobic) respiration for active transport

Question 13

4 points

Explain why a species of sea creature may die in water with a low concentration of oxygen

Answer 13

concentration gradient less steep

so less oxygen diffuses into the blood

so less (aerobic) respiration occurs so less energy is released

so less metabolism

Question 14

2 marker

Explain why having only one ventricle makes the circulatory system less efficient than having two ventricles?

Answer 14

oxygenated and deoxygenated blood mix

so less oxygen reaches cells