Cells And Control

Question 1

What is mitosis?

Answer 1

Mitosis is a type of cell division which produces two genetically identical daughter diploid cells.

Question 2

Describe the stage of interphase

Answer 2

The cell grows and subcellular structures like mitochondria and ribosomes multiply. The chromosomes copy itself to get ready to undergo mitosis.

Question 3

Describe the stages of mitosis

Answer 3

Prophase - DNA condenses, chromosomes become visible and nuclear membrane breaks down.
Metaphase - Chromosomes line up along the equator of the cell.
Anaphase - Spindle fibres attach to the chromosomes. Chromosomes are pulled to opposite ends of the cell.
Telophase - Nucleus divides and a new membrane forms around each chromosome.
Cytokinesis - The cell’s cytoplasm and membrane divides and produces two genetically identical diploid daughter cells.

Question 4

What is mitosis important for? (3)

Answer 4

Growth, To repair damaged cells, Asexual reproduction

Question 5

How does a cell become cancerous?

Answer 5

This is when a cell divides uncontrollably, leading to the formation of a tumour.

Question 6

How does growth occur in animals?

Answer 6

Growth occurs via mitosis and cell differentiation.

Question 7

Describe growth in plants

Answer 7

Growth occurs through cell division, cell differentiation and cell elongation, controlled by auxins.

Question 8

What are percentile charts used for?

Answer 8

To monitor growth, by using measurements like head circumference and length.
They help doctors determine if growth is normal, slower, faster or irregular.

Question 9

What is a stem cell?

Answer 9

A stem cell is an undifferentiated cell capable of dividing to produce more similar cells.

Question 10

What are embryonic stem cells?

Answer 10

They form when an egg and sperm fuse together to form a zygote.
They can differentiate into any type of cell in the body.

Question 11

What are adult stem cells?

Answer 11

Found in bone marrow and can form various types of cells, including blood cells.

Question 12

What are meristems in plants?

Answer 12

Found in root and shoot tips, capable of differentiating into any type of plant cell throughout the plants life.

Question 13

What is therapeutic cloning?

Answer 13

Therapeutic cloning involves producing an embryo with the same genes as the patient.

Question 14

What are the benefits of stem cell research?(3)

Answer 14

1. Can be used to replace damaged or diseased body parts.
2. Unwanted embryos from fertility clinics could be used as they would otherwise be discarded.
3. Research into the process of differentiation

Question 15

What are the problems of stem cell research? (3)

Answer 15

1. We do not completely understand the process of differentiation, so it is hard to control stem cells to form the cells we desire.
2. People may have religious or ethical objection as it is seen as interference with the natural process of reproduction.
3. If the growing stem cells are contaminated with a virus, an infection can be transferred to the individual.

Question 16

What is the CNS?

Answer 16

The CNS consists of the brain and spinal cord.

Question 17

What is the Cerebrum responsible for?

Answer 17

Responsible for consciousness, memory, intelligence and visual and sensory processing.

Question 18

What is the Cerebellum responsible for?

Answer 18

Responsible for controlling muscle movements and coordination.

Question 19

What is the Medulla oblongata responsible for?

Answer 19

Responsible for breathing, digestion, swallowing and sneezing.

Question 20

How do CT scans and PET scans differ in imaging the brain?

Answer 20

CT scans use x-ray radiation from multiple angles to create 3D image, useful for examining bleeding and damage.
PET scans use a radioactive tracer to highlight areas of increased blood flow, helpful in identifying cancerous tumours.

Question 21

Why is investigating the brain’s functions and treating brain damage challenging? (3)

Answer 21

1. It is complex, delicate and can easily be damaged.
2. Drugs given to treat diseases cannot always reach the brain because of the membranes that surround it.
3. It is not fully understood which part of the brain does what.

Question 22

Describe the pathway of the nervous system

Answer 22

The receptors convert the stimulus into electrical impulses, which travel along sensory neurones to the CNS. The CNS coordinates a response, sending impulses along motor neurones to effectors, resulting in a response (contracting a muscle or glands secreting hormones).

Question 23

How does the reflex arc differ from the nervous system pathway?

Answer 23

An involuntary response, does not involve the brain used to keep the body out of danger.
1. The receptors convert the stimulus into electrical impulses, which travel along sensory neurones to the CNS. 2. In the CNS, the impulses travel to the relay neurones. 3. Impulses are then sent along a motor neuron, resulting in a response (contracting a muscle or glands secreting hormones).

Question 24

What are synapses and how do they function?

Answer 24

Synapses are the gaps between two neurones.
When the impulse reaches the end of the first neuron, a chemical called neurotransmitters is released into the synapse. This neurotransmitter diffuses across the synapse. When the neurotransmitter reaches the second neurone, it triggers the impulse to begin again in the next neurone.

Question 25

What is the function of the myelin sheath?

Answer 25

Myelin sheaths are insulating layers around the axon which causes the electrical impulses to travel faster.

Question 26

Describe the structure and function of the Retina

Answer 26

Contains rod and cone cells.
Rod cells - responsible for light intensity
Cone cells - responsible for colour vision

Question 27

Explain the functions of the cornea, iris and lens

Answer 27

The cornea allows light into the eye, iris controls the pupil size and the lens focuses light onto the retina.

Question 28

What are some common eye defects and how are they treated? (4)

Answer 28

Short sightedness - treated with concave lens
Long sightedness - treated with convex lens
Cataracts - treated with lens replacement surgery
Colour blindness - usually genetic and untreatable