Transport in cells

Question 1

What is diffusion?

Answer 1

Process by which particles of gas or liquid spread out from an area of high concentration to a lower concentration. It therefore can be described as the net movement of particles

Question 2

What is a concentration gradient?

Answer 2

The measurement of concentration from high to low.

Question 3

Explain diffusion of oxygen in the lungs

Answer 3

1. The alveoli has a thin layer of flattened cells in their wall and the capillary walls are only 1 cell thick as well.
2. The concentration of o2 in the alveoli is higher than in the blood.
3. Therefore there is a concentration gradient and the o2 diffuses from the alveoli into the blood.
4. The blood carries the o2 to the working muscles.
5. The muscles have a lower concentration of o2 than the blood.
6. There there is a concentration gradient and the o2 diffuses from the blood to the muscles.

Question 4

Explain diffusion of carbon dioxide in the lungs

Answer 4

1. There is a high concentration of CO2 in the muscles as a result of tissue respiration.
2. The blood has a lower concentration of CO2 than the muscles.
3. Therefore there is a concentration gradient.
4. Therefore the CO2 will diffuse from the muscles into the blood.
5. The blood is circulated to the lungs.
6. There is a higher concentration of CO2 in the blood than the lungs
7. Therefore there is a concentration gradient
8. Therefore the CO2 will diffuse from the blood into the lungs to be exhaled

Question 5

Describe adaptations of the lungs to allow gaseous exchange.

Answer 5

1. Have a large surface area to allow more o2 and co2 to diffuse.
2. Have moist memebranes to allow faster diffusion of gases.
3. Have linings 1 cell thick to allow gases to diffuse easily
4. Has a large network of capillaries to allow nore diffusion to take place.
5. Ventillation or breathing moves air with more o2 into the lings and the air with more co2 out of the lungs.

Question 6

Describe diffusion of oxygen in insects

Answer 6

1. insects do not have lungs
2. O2 diffuses into their cells through small tubes over their body.
3. there is a concentration gradient from the tubes- high to the cells low.
4. The size of insects is limited because they can only take in oxygen over a small area.

Question 7

How does the surface area to volume ratio change as objects or organisms get bigger?

Answer 7

The ratio gets smaller

Question 8

How does the surface area to volume ratio help a small organism?

Answer 8

It has a big ratio therefore it is easier for gases to diffuse into it.

Question 9

How do bigger organisms adapt when taking in oxygen because of their low surface to volume ratio?

Answer 9

They have specialist organs to help them to breathe.

Question 10

Explain the factors which affect diffusion?

Answer 10

1. Concentration gradient- the bigger the diffrence between the high and low areas the more likely the particles are to diffuse down the gradient.
2. Temperature- particles at a higher temperature have more kinetic energy and so move more quickly therefore diffuse more quickly.
3. Surface area- the larger the surface area of a membrane the more particles can diffuse.

Question 11

What is osmosis?

Answer 11

It is the net diffusion of water from an area of high concentration of water (dilute solution) to one of low concentration of water (concentrated solution) across a semi permeable membrane

Question 12

Explain how plants use osmosis to get water from the soil

Answer 12

1. Plants pull water upwards from the roots to the leaves where it is lost through transpiration.
2. This means that the roots almost always have a lower concentration of water than the soil.
3. Water therefore diffuses across the membrane of the root cell by osmosis.

Question 13

What does the term isotonic mean?

Answer 13

That two solutions have the same concentration and therefore there is no concentration gradient and water will move in both directions through a semi permeable membrane

Question 14

What does the term hypertonic mean?

Answer 14

If a solution is more concentrated than another one it is called hypertonic, it has a lower water concentration than the other. This means that water will pass into it from the solution which is more dilute and has a higher concentration of water through a semi permeable membrane.

Question 15

What does the term hypotonic mean?

Answer 15

It is the opposite of hypertonic, the name for a less concentrated solution, the solution with a higher water concentration. It will lose water by osmosis.

Question 16

What is active transport in plants?

Answer 16

Active transport is the name used to describe how minerals are moved from areas of lower concentration in the soil into the roots of plants. It goes against the diffusion gradient and so needs energy from the plant to make it happen.

Question 17

Give an example of active transport in humans

Answer 17

When the blood sugars drop the body uses active transport to increase the concentration by using energy to move sugars from lower concentration is the gut into the blood.