Chapter 6 - Movement In & Out Of Cells

Question 1

What is diffusion?

Answer 1

The random movement of atoms, molecules or ions from a region of high concentration to a region of low concentration down a concentration gradient until an equilibrium is achieved.

Question 2

Explain the process of diffusion.

Answer 2

Molecules have kinetic energy, move randomly and collide with each other. There are more collisions in a region of high concentration than in a region of low concentration. Random collisions of molecules spread the molecules out down the concentration gradient.

Question 3

Does diffusion require energy?

Answer 3

No, but there is a small amount of kinetic energy involved.

Question 4

Explain surface area as a factor that influence diffusion rate.

Answer 4

The larger the surface area, the quicker the rate of diffusion.

Question 5

Explain temperature as a factor that influence diffusion rate.

Answer 5

The rate of the diffusion is quicker with an increase in temperature.
As temperature increases, the kinetic E of particles also increase, which leads to an increase velocity. The higher the velocity, means greater chance of collisions between particles resulting in an increased rate of diffusion.

Question 6

Explain concentration gradient as a factor that influence diffusion rate.

Answer 6

The greater the difference in concentration, the quicker the rate of diffusion.

Question 7

Explain diffusion distance as a factor that influence diffusion rate.

Answer 7

Smaller or shorter distances results in faster diffusion rate and larger distances result in slower diffusion rate.

Question 8

Explain the importance of diffusion in gaseous diffusion for photosynthesis.

Answer 8

• CO2 used by plants for photosynthesis siddufe from the air into the leaves through the stomata, because there is a lower concentration of CO2 inside the leaf than outside the leaf as the cells are using it.

Question 9

Explain the role of diffusion in flowering plants.

Answer 9

• Flowering plants use diffusion to attract pollinators by their fragrance, which diffuse from a high concentration in the petals into the air.

Question 10

X plain the importance of diffusion in humans.

Answer 10

Diffusion occurs across the alveolar membrane of the lung, which separates CO2-rich blood from the O2-rich air.
O2 diffuses across the membrane and becomes dissolved in the blood.
CO2 diffuse across the membrane into the air.
The capillaries around the alveoli have a high concentration of CO2 and a low concentration of O2.

Question 11

Explain the importance of diffusion in solute diffusion.

Answer 11

Some products of digestion are absorbed from the ileum of mammals by diffusion.
Solutes like glucose and amino acids can diffuse from the ileum where there is a high concentration into the bloodstream where there is a low concentration.

Question 12

What is osmosis?

Answer 12

Thee movement of water molecules from a high water potential to a low water potential through a selectively permeable membrane down a water potential gradient.

Question 13

What is the difference between a solution, solute and a solvent?

Answer 13

Solution - two or more substances mixed together
Solute - the substance to be dissolved
Solvent - the substance doing the dissolving

Question 14

Explain the difference between hypotonic, isotonic and hypertonic solutions.

Answer 14

Hypotonic - contains less solutes and more water
Isotonic - 2 solutions have the same water potential
Hypertonic - contains more solutes and less water

Question 15

What is turgor pressure?

Answer 15

Pressure exerted by water inside the cell against the cell wall - caused by cytoplasm pressing against cell wall and pushing cell membrane against the cell wall.

Question 16

How does plants wilt?

Answer 16

Plants lose so much water that the turgor pressure falls to zero, cells become plasmolysed and flaccid and the cell membrane is not pressed tightly against the cell wall anymore.

Question 17

What happens to animal cells in a hypotonic solution?

Answer 17

Water moves into the cells by endosmosis. The cells start to swell up and will eventually burst as the cells can’t become turgid, and there is no cell wall to prevent it from bursting.

Question 18

What happens to plant cells in a hypotonic solution?

Answer 18

Water moves into the cells by endosmosis.distilled water has a high water potential and the cytoplasm has a low water potential. The plant cell expands and vacuole swells, as the cell becomes turgid. Rigid cell wall only expands slightly, which prevent the cell from bursting.

Question 19

What happens to animal cells in hypertonic solutions?

Answer 19

Water moves out of the cells due to exosmosis. The cells will shrink

Question 20

What happens to plant cells in hypertonic solutions?

Answer 20

Water moves out of the cells by exosmosis. Salt water has a lower water potential and the cytoplasm has a higher water potential. The cytoplasm and vacuoles shrink and the cells become flaccid as water moves out of it. The cell membrane tears away from the cell wall and the cells will undergo plasmolysis.

Question 21

Explain the importance of water potential and osmosis. (5)

Answer 21

• Osmosis facilitates the movement of water across the cell membrane, so it causes the migrating of water into and out of cells and maintaining the water balance.
• It is the control by which organisms maintain just the right amount of water, as water is important for many biological processes and it regulates the water potential of cells.
• Plants gain water through osmosis in their roots from the soil which is used in photosynthesis.
• many nutrients and essential molecules that animals need are dissolved in water.
• metabolic waste products are dissolved in water which is then transported to the kidneys to be excreted.

Question 22

What is active transport?

Answer 22

The movement of particles through a cell membrane, from a region of low concentration to a region of high concentration against a concentration gradient, using energy from respiration.

Question 23

Explain the importance of active transport in the uptake of mineral ions by root hairs.

Answer 23

Mineral ions move from a region of low concentration in the soil to a region of high concentration in the root hair cell against a concentration gradient.
Active transport requires energy as ATP to drive these ions uphill
A large number of root hairs, give a large surface area to the root so man mitochondria are present to provide energy.

Question 24

Explain the importance of active transport in the uptake of glucose by epithelial cells of villi.

Answer 24

Glucose is required to move against a concentration gradient from a region of low concentration to a region of a high concentration, using energy released during respiration.
The active transport is carried out by carrier proteins in the membrane, which bind to the solute molecules, change the shape and carry the molecule across the membrane.

Question 25

Explain the importance of active transport in the uptake of glucose by epithelial cells of kidney tubules.

Answer 25

Re-absorption of glucose by the kidney tubules entails transport from the lumen of the tubule, into the epithelial.
Glucose is required to move against a concentration gradient from a region of low concentration to a region of a high concentration, using energy released during respiration.

Question 26

What is the role of protein molecules in active transport?

Answer 26

Protein molecules move particles across a membrane during active transport by binding to the solute, changing its shape and carrying the molecule across the membrane.