2 - Cells and Control

Question 1

In human body cells, are chromosomes normally found in pairs or triplets?

Answer 1

In pairs

Question 2

Which of the following do chromosomes contain?

A. Mitochondria B. Cytoplasm C. Genes D. Amino Acids

Answer 2

C. Genes

Question 3

What is mitosis? What is it used for?

Answer 3

Mitosis is the stage of the cell cycle when the cell divides. Organisms use mitosis to grow or replace cells that have been damaged.

Question 4

A normal human body cell contains 23 pairs of chromosomes. How many chromosomes would be in each new human cell formed by mitosis?

Answer 4

Each cell will have 46 chromosomes (23 pairs)

Question 5

What is a stem cell?

Answer 5

An undifferentiated cell which has the ability to become one of many different types of cell or more stem cells

Question 6

Where can stem cells be found in an adult human? What do they do?

Answer 6

Bone marrow. They turn into specific cells, such as blood cells.

Question 7

What type of plant tissue contains stem cells?

Answer 7

Meristem tissue

Question 8

Describe a potential risk of stem cell therapy?

Answer 8

E.g. if stem cells are contaminated with a virus, the virus could be passed on to the patient.

Question 9

Josie has been warned that a plant disease could start to spread to the crops on her farm in the near future. How could Josie use stem cells to ensure her crop yield is not affected by the disease?

Answer 9

Josie could use stem cells to grow crops of identical plants with disease resistance. The plants would then be more likely to survive if the disease reaches her farm.

Question 10

Heart attacks are caused by the blockage of coronary arteries that carry oxygen to the heart. This can result in damage or death of heart muscle. Suggest how embryonic stem cells could potentially be used to treat a patient after a heart attack.

Answer 10

Embryonic stem cells would be made to develop into heart muscle cells. These could repair the damaged tissue or replace the damaged cells after a heart attack.

Question 11

Briefly outline the ethical arguments for and against embryonic stem cell therapy.

Answer 11

Some people think it’s wrong to take stem cells from embryos as they’re a human life. Others disagree and think it is unethical to let patients suffer when there is something we could potentially do to help.

Question 12

True or false? Muscles and glands are examples of receptors.

Answer 12

False

They are effectors

Question 13

In humans, what does the central nervous system (CNS) consist of?

Answer 13

The brain and spinal cord

Question 14

Which type of neurone carries impulses from the CNS to the effectors?

Answer 14

Motor neurone

Question 15

Why is the nervous system important to humans?

Answer 15

The nervous system means that humans can react to their surroundings and coordinate their behaviour

Question 16

A rabbit is eating some grass. It sees a fox and hops away from it. What is the stimulus? Where are the receptors that detect the stimulus?

Answer 16

The stimulus is the fox (the threat of predation). The receptors are in the rabbit’s eyes

Question 17

How is the stimulus transmitted from receptors to the CNS?

Answer 17

Sensory neurones carry the information from the receptors to the CNS

Question 18

True or false? Reaction time is the time it takes to detect a stimulus.

Answer 18

False

Reaction time is the time it takes to respond to a stimulus

Question 19

How are nerve signals transferred across a synapse?

Answer 19

Chemicals diffuse across the synapse and set off a new electrical impulse in the next neurone.

Question 20

What is a reflex arc?

Answer 20

The passage of information in a reflex (from receptor to effector)

Question 21

Reflexes do not involve conscious parts of the brain? Why is this advantageous?

Answer 21

It reduces the chance of an injury, as it means that reflexes can be rapid and automatic.

Question 22

Alcohol is a depressant, which means it reduces the effectiveness of neurone signalling. Suggest what effect this would have on a person’s reaction time.

Answer 22

Reaction time will be slower because the nerve signals take longer to transmit around the body, so the response will take longer

Question 23

A gardener is pulling up weeds when she gets stung by a nettle. A reflex action causes her to immediately move her hand away from the nettle. What is the effector in this reflex action?

Answer 23

The muscles in her hand