Chapter 3

Question 1

diffusion

Answer 1

the net movement of particles from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement

Question 2

Describe the importance of diffusion of gases and solutes

Answer 2

it is important for gas exchange in organisms for processes like respiration and removal of waste gases. It is also useful for the uptake of solutes for plants

Question 3

Where does the energy for diffusion come from?

Answer 3

the kinetic energy of random movement of molecules and ions

Question 4

how do substances move in and out of a cell?

Answer 4

by diffusion through the cell membrane

Question 5

Investigate how surface area influences diffusion

Answer 5

A larger surface area increases the rate of diffusion.

1

Question 6

Investigate how temperature influences diffusion

Answer 6

An increase in temperature increases the rate of diffusion.

2.

Question 7

Investigate how concentration gradients influences diffusion

Answer 7

An increase in concentration gradients increases the rate of diffusion
3.

Question 8

Investigate how distance influences diffusion

Answer 8

An increase in distance decreases the rate of diffusion

4.

Question 9

How does water diffuse through a partially permeable membrane?

Answer 9

by osmosis

Question 10

osmosis

Answer 10

the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane

Question 11

Investigate the effects on plant tissues of immersing them in solutions of different concentrations

Answer 11

1. Cut 9 cores of a potato with the same width and height.
2. measure the lengths so they are the same
3. put three in 3 different solution of distilled water A, dilute sugar solution B and concentrated sugar solution C.
4. Leave them there for 30 minutes
5. remove the cores and measure their new lengths. They should be longer and firmer for A, same length and firmness of B and shorter and bendier in C

Question 12

How are plants supported?

Answer 12

by the pressure of water inside the cells pressing outwards on the cell wall. The water creates turgor pressure which pushes the cell membrane against the inelastic cell wall, making it stand up more firm.

Question 13

describe the effects on plant tissues of immersing them in solutions of different concentrations

Answer 13

Due to osmosis, substances submerged in distilled water would gain more water due to the low water potential and they would increase in size and become more turgid. If they are submerged in a solvent with a similar water potential, there would be no difference as it is in equilibrium. If submerged in a solvent with low water potential (ie. higher concentration of sucrose) they lose water to the solvent as it goes from an area of high water potential to an area of low water potential.

Question 14

Explain the importance of water potential and osmosis in the uptake of water by plants

Answer 14

Plants always move water out of the roots upwards to allow a low water potential in the roots. This causes osmosis to occur which moves the surrounding area of water to move inside the root and continue upwards. This water can be transported to the leaves so that photosynthesis can take place **

Question 15

Explain the importance of water potential and osmosis on animal cells and tissues

Answer 15

• for both, in order to transport water to the rest of the cells
• to prevent the red blood cells from bursting or shrivelling.

Question 16

active transport

Answer 16

the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration

Question 17

Discuss the importance of active transport

Answer 17

it allows ion uptake by root hairs in plants and uptake of glucose by epithelial cells of villi and kidney tubules in humans. For plants, they are only able to keep their minerals inside the roots via active transport, which prevents normal diffusion from moving the ions outwards. For humans, they can only absorb glucose in the villi and kidney tubules if the cells have a high respiration rate.

Question 18

Explain how protein molecules move particles across a membrane during active transport

Answer 18

The cell membrane contains carrier proteins. They span the cell membrane and provide ways for ions and molecules to enter or leave the cell via active transport. The ion or molecule first bond with the carrier protein to change its shape. Then, it is able to carry the substance inside the membrane. The molecule/ion is then released inside the cell and revert back to their normal shape and go outside again to repeat the process.