cell biology- part 2

Question 1

Describe the function of stem cells in embryos, in adult animals and in the meristems in plants.

Answer 1

Stem cells from human embryos can be cloned and made to
differentiate into most different types of human cells.
Stem cells from adult bone marrow can form many types of cells
including blood cells.
Meristem tissue in plants can differentiate into any type of plant cell, throughout the life of the plant.
Treatment with stem cells may be able to help conditions such as diabetes and paralysis.

Question 2

Describe therapeutic cloning

Answer 2

In therapeutic cloning an embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient’s body so they may be used for medical treatment.
The use of stem cells has potential risks such as transfer of viral
infection, and some people have ethical or religious objections.

Question 3

What are the three main stages of the cell cycle?

Answer 3

• Replication of DNA
• Mitosis
• division of cells

Question 4

Why is mitosis important?

Answer 4

• Produces identical cells which all have the same genetic information
• produces additional cells for growth and repair.

Question 5

Describe the cell cycle

Answer 5

Stage 1: Cells grow and increase in mass and replicate dna and synthesise more organelles.
Stage 2: Each chromosome in a pair is pulled to opposite sides, nucleus divides.
Stage 3: The cytoplasm and cell membrane divides, two identical daughter cells are produced.

Question 6

What is diffusion?

Answer 6

When particles move down a concentration gradient, moving from areas of high concentration to areas of low concentration.

Question 7

What three main factors affect the rate of diffusion?

Answer 7

• temperature
• surface area
• larger gradient, faster diffusion (concentration gradient)

Question 8

Give examples of diffusion in lungs and kidneys.

Answer 8

Lungs diffuse oxygen into the blood and carbon dioxide diffuses into the lungs.
kidney- urea diffuses from cells into blood plasma so it can be excreted through urine.

Question 9

How are single-celled organisms adapted for diffusion?

Answer 9

They have a large surface area to volume ratio so maximises rate

Question 10

What four factors affect the effectiveness of a gas exchange surface?

Answer 10

• large surface area
• thin membrane
• efficient blood supply (animals)
• ventilation (animals)

Question 11

What is osmosis?

Answer 11

when water moves through a partially permeable membrane from an area of high concentration to an area of low concentration.

Question 12

What is meant when a solution is isotonic to a cell?

Answer 12

the concentrations of the external and internal solutions are the same.

Question 13

How do plants leaves and stems stay rigid?

Answer 13

Turgor pressure- water moves in by osmosic causing the vacuole to shrivel and the cytoplasm to be squashed against the cell wall

Question 14

what is active transport?

Answer 14

the movement of molecules from a more dilute solution to a more concentrated solution against a concentration gradient, using energy from respiration.

Question 15

How do plant root hair cells use active transport?

Answer 15

to take up minerals from a more dilute solution in soils. (ions such as magnesiums and nitrates)

Question 16

How is active transport used used to absorb the products of digestion?

Answer 16

by transporting glucose from a lower concentration in the gut to a higher concentration in the blood. glucose then transported to tissues.