Topic 2 - Cells And Control

Question 1

What benefits are there of use of stem cells in medicine? (2)

Answer 1

• Possible to use stem cells to create specialised cells to replace those which have been damaged by disease and injury.
• Possible to find new cures for diseases

Question 2

Describe growth in plants. (8)

Answer 2

Plants produced by sexual reproduction begin life as a a single cell, a fertilised egg or zygotes. These cells must divide by mitosis to produce a multicellular organism. Mitosis only happens in specific regions of plants. These are called meristems and are found in the tips of roots and shoots. Here new cells are formed. Plant cells are also able to become longer as they grow. This is called cell elongation and occurs throughout the plant. The cells of multicellular plants must also differentiate, so that its cells develop features that enable them to fulfil specific roles. Cells that have differentiated have specialised. Without this specialisation, complex multicellular plantsq wouldn’t exist.

Question 3

What does the relay neurone do?

Answer 3

Relay neurones carry messages from one part of the CNS (brain and spinal cord) to another.

Question 4

Describe the medulla oblongata.

Answer 4

Controls unconscious activities such as heart rate and breathing rate.

Question 5

Describe the importance of mitosis in: Repair

Answer 5

Organisms can repair some of their tissues, using mitosis to regenerate new cells.

Question 6

What do rod cells do?

Answer 6

They work well in dim light.

Question 7

Describe the Cerebellum.

Answer 7

This part of the brain is responsible for muscle coordination and balance.

Question 8

How can cataracts be treated?

Answer 8

Cataracts can be treated by removing the lens and replacing with a plastic lens.

Question 9

What does the cornea do?

Answer 9

Refracts light - bends it as it enters the eye

Question 10

Risks of brain surgery (7)

Answer 10

• allergic reaction to anesthesia
• bleeding in the brain
• a blood clot
• brain swelling
• coma
• impaired speech, vision, coordination, or balance
• infection in the brain or at the wound site

Question 11

Describe the stage of mitosis: Telophase

Answer 11

A new cell membrane forms around the two sets of DNA so the cell has two nuclei in it. A cleavage furrow forms.

Question 12

Describe the function of embryonic stem cells.

Answer 12

These embryonic stem cells have the potential to divide and produce any kind of cell at all. This makes sense all the different types of cell found in a human have to come from those few cells in the early embryo. This means stem cells are really important for the growth and development of organisms.

Question 13

Describe the importance of mitosis in: Growth

Answer 13

When a multi cellular organism grows, it makes more cells through mitosis which allows the organism to grow and successfully live.

Question 14

What does the iris do?

Answer 14

Controls how much light enters the pupil

Question 15

What does the synapses do?

Answer 15

Where two neurones meet, there is a tiny gap called a synapse. Signals cross this gap using chemicals released by a neurone. The chemical diffuses across the gap makes the next neurone transmit an electrical signal.

Question 16

Describe the cerebral hemispheres. (4)

Answer 16

The cerebrum’s outer layer, it is split into two hemispheres and is highly folded. These two hemispheres make up the cerebral cortex. This controls most of our senses, intelligence, personality, conscious thought and high-level functions, such as language and verbal memory.

Question 17

What are receptors?

Answer 17

Receptors are groups of specialised cells. They detect a change in the environment and stimulate electrical impulses in response. Sense organs contain groups of receptors that respond to specific stimuli.

Question 18

What does uncontrolled cell division lead to?

Answer 18

Sometimes the cells in part of a multicellular organism divide uncontrollably. The result is a large mass of cells called a tumour. If tumour cells successfully invade other tissues in the body the result is cancer

Question 19

What is mitosis?

Answer 19

A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth

Question 20

Describe the stage of mitosis: Metaphase

Answer 20

Chromosomes line up at the cell’s equator (across the middle), there is double amount of DNA in the cell. Fibres start to form.

Question 21

What are cataracts?

Answer 21

A cataract is a cloudiness in the lens, caused by a build up of protein inside the lens.

Question 22

How can long-sightedness be corrected?

Answer 22

It can be corrected by using glasses that have convex lenses.

Question 23

Describe the stage of mitosis: Cytokinesis

Answer 23

The cell spilts into two genetically identical cells.

Question 24

Describe the function of stem cells in animals.

Answer 24

In animals, adult stem cells are used to replacing damaged cells. E.g. to make new skin or blood cells.

Question 25

What is a neurone?

Answer 25

Nerve cells are called neurones. They are adapted to carry electrical impulses from one place to another. A bundle of neurones is called a nerve.

Question 26

Describe the function of meristems in plants.

Answer 26

Meristems produce unspecialised cells that are able to divide and form an cell type in the plant they act like embryonic stem cells. But unlike human stem cells, these cells can divide and differentiate to generate any type of cell for as long as the plant lives. The unspecialised cells go on to form specialised tissues like xylem and phloem

Question 27

What do the three main types of neurones have in common? (3)

Answer 27

• A long fibre (axon) which is insulated by a fatty (myelin) sheath. - - They are long so they can carry messages up and down the body.
• Tiny branches (dendrons) which branch further as dendrites at each end. These receive incoming impulses from other neurones.

Question 28

Describe the stage of mitosis: Interphase

Answer 28

This is when the cell does what it is doing what it usually does. It is not a part of mitosis. But by the end of this phase the cell’s DNA will have replicated.

Question 29

Describe the importance of mitosis in: Asexual reproduction

Answer 29

Mitosis is important in asexual reproduction as there is only one parent and mitosis divide the one cell into two. The offspring is identical to the parent.

Question 30

What risks are there of use of stem cells in medicine? (3)

Answer 30

• Tumour development - stem cells divide very quickly. If scientists are unable to control the rate at which the transplanted cells divide inside a patient, a tumour may develop.
• Disease transmission viruses live inside cells. If donor stem cells are infected with a virus and this isn’t picked up, the virus could be passed on to the recipient and so make them sicker.
• Rejection if the transplanted cells aren’t grown using the patient’s own stem cells, the patient’s body may recognise the cells as foreign and trigger an immune response to try to get rid of them The patient can take drugs to suppress this response, but this makes them susceptible to diseases.

Question 31

What is long-sightedness? (3)

Answer 31

Someone who is long-sighted can see distant objects clearly, but they cannot focus properly on near objects.

Long-sightedness is caused by one of the following:

• the eyeball being too short - so the distance between the lens and retina is too small.
• a loss of elasticity in the lens - meaning it cannot become thick enough to focus (which is often age-related).

Question 32

Describe the stage of mitosis: Prophase

Answer 32

The DNA has condensed into chromosomes. Nucleus has disappeared so the DNA is free to move in the cytoplasm.

Question 33

What does the motor neurone do?

Answer 33

Motor neurones carry signals from the CNS to effectors (e.g. muscles, glands) .

Question 34

Why is CT scanning and PET scanning useful for accessing brain tissue?

Answer 34

We can’t always look inside the brain without performing some form of surgery so we can use CT and PET scans to look at the brain. This is much less invasive for the patient. Also, these scans are much useful for looking for soft tissue than x-rays.

Question 35

What does the sensory neurone do?

Answer 35

Sensory neurones carry signals from receptors to the CNS (spinal cord and brain).

Question 36

What are the three main types of neurone?

Answer 36

• Sensory
• Motor
• Relay

Question 37

What does the lens do?

Answer 37

Further refracts light to focus it onto the retina

Question 38

Describe growth in animals. (7)

Answer 38

Animals produced by sexual reproduction begin life as a a single cell, a fertilised egg or zygotes. These cells must divide by mitosis to produce a multicellular organism. Mitosis happens throughout the bodies of animals. Cell elongation doesn’t happen in animals. The cells of multicellular animals must also differentiate, so that its cells develop features that enable them to fulfil specific roles. Cells that have differentiated have specialised. Without this specialisation, complex multicellular animals wouldn’t exist.

Question 39

How can shortsightedness be corrected?

Answer 39

It can be corrected by using glasses that have concave lenses.

Question 40

What is shortsightedness? (3)

Answer 40

Someone who is short-sighted can see near objects clearly, but cannot focus properly on distant objects.

Short sight is caused by one of the following:

• the eyeball being elongated - so that the distance between the lens and the retina is too great.
• the lens being too thick and curved - so that light is focused in front of the retina.

Question 41

Describe the stage of mitosis: Anaphase

Answer 41

Spindle fibres pull the chromosomes apart so half the DNA is at one of the cell and the other half is at the other.

Question 42

What is the myelin sheath?

Answer 42

The axon is surrounded by a fatty layer known as the myelin sheath. This helps to protect the neurone and allow impulses to travel faster.

Question 43

What do cone cells do?

Answer 43

They are responsible for colour vision and work well in bright light.