Transport In And Out Of Cells

Question 1

What is the definition for diffusion ?

Answer 1

Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration until they are evenly spread out. This happens because the particles move randomly and spread

Question 2

What are some examples of diffusion in living organisms ?

Answer 2

1.Oxygen and carbon dioxide diffuse during gas exchange in lungs, gills and plant leaves
2. Urea diffuses from cells into the blood plasma for exertion by kidney
3. Digested food molecules from the small intestine diffuse into the blood

Question 3

What are some of the factors affecting diffusion ?

Answer 3

1. Difference in concentration, known as concentration gradient
2. The temperature
3. The surface area of the membrane

Question 4

Explain a single celled organism and explain how it allows molecules to diffuse?

Answer 4

A single celled organism has a large surface area to volume ratio.
This allows enough molecules to diffuse into and out of the cell to meet the needs of the organism

Question 5

Explain multicellular organisms ?

Answer 5

Multicellular organisms have larger cells, with a smaller surface area to volume ratio

Question 6

Important molecules have to be moved via what?

Answer 6

Important molecules have to be moved via transport systems with specialised exchange surfaces

Question 7

How are small intestines and lungs in mammals, gills in fish, and the roots and leaves in plants well adapted for exchanging materials ?

Answer 7

1. Large surface area
2. The surface is thin so that molecules only have to diffuse a short distance
3. Surfaces are only usually kept moist so that substances can dissolve and diffuse across cells membranes faster
4. In animals, an efficient blood supply maintains a high concentration gradient
5. In animals, ventilation occurs to maximise gaseous exchange

Question 8

How can water move across cell membranes ?

Answer 8

By osmosis

Question 9

What is meant by the term Osmosis ?

Answer 9

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

Question 10

What is meant by active transport?

Answer 10

Active transport moves substances against a concentration gradient, from an area of low concentration to high concentration. The energy for this comes from respiration

Question 11

What does active transport allow ?

Answer 11

Active transport allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil. Active transport also allows sugar molecules to be absorbed from lower concentrations in the gut into the blood, which has a higher concentration