Topic 2 - cells and control

Question 1

What happens during interphase?

Answer 1

Before mitosis, cell grows and increases subcelullar structures. It duplicates its DNA and DNA is copied and forms X-shaped chromosomes

Question 2

What happens during prophase?

Answer 2

chromosomes condense, getting shorter and fatter. the membrane around the nucleus breaks down and the chromosomes lie free in the cytoplasm

Question 3

What happens during metaphase?

Answer 3

The chromosomes line up at the centre of the cell

Question 4

What happens during anaphase?

Answer 4

Cell fibres pull the chromosomes apart. The two arms of each chromosome go to opposite ends of the cell

Question 5

What happens during telophase?

Answer 5

Membranes form around each of the sets of chromosomes. Those become the nuclei of the 2 new cells - The nucleus has divided

Question 6

What happens during cytokinesis?

Answer 6

Before telophase ends, the cytoplasm and cell membrane divide to form 2 separate cells

Question 7

How is mitosis useful in growth and repair?

Answer 7

Multicellular organisms use mitosis to grow or to replace damaged cells

Question 8

How is mitosis useful in asexual reproduction?

Answer 8

Some organisms use mitosis to reproduce e.g. strawberries

Question 9

What is produced at the end of mitosis?

Answer 9

The cell has produced 2 new daughter cells. each daughter cell contain the same set of chromosomes in its nucleus as the other daughter cell. They’re genetically identical diploid cells. They’re also genetically identical to the parent cell

Question 10

What causes cancer?

Answer 10

1. The rate at which cells divide is controlled by an organisms genes
2. if theres a change in a gene that controls cell division, the cell may start dividing uncontrollably
3. This can lead to a mass of abnormal cells (tumour)
4. If the tumour invades and destroys surrounding tissue, it is cancer

Question 11

Describe cell division in animals

Answer 11

when animals are young, cells divide at a fast rate as they need to grow. When they reach adulthood, cells mostly divide to replace damaged cells. Cell differentiation is lost at an early stage

Question 12

What is cell differentiation?

Answer 12

the process in which a cell changes to become specialised for its job. This allows multicellular organisms to work more efficiently

Question 13

Describe cell elongation, cell division and cell differentiation in plants

Answer 13

1. growth in height in plants is due to cell elongation
2. cell division only happens in the roots and shoots
3. plants grow continuously, so they will always differentiate to develop new parts

Question 14

What is the function of embryonic stem cells?

Answer 14

These are cells found in early human embryos and they can divide and produce and kind of cell at all. This means they are important for the growth and development of organisms

Question 15

What is the function of adult cells in animals?

Answer 15

These are found in bone marrow and aren’t as versatile as embryonic stem cells. They can be used to repair damaged cells.

Question 16

What is the function of meristems?

Answer 16

Meristems are like embryonic stem cells but the cells in meristems can differentiate for as long as the plant lives.

Question 17

What are the benefits of using stem cells in medicine?

Answer 17

1. They may cure diseases e.g. sickle cell anaemia
2. they can differentiate into any cell under certain conditions
3. It can be used to replace cells that had been damaged due to injury

Question 18

What are the risks of using stem cells in medicine?

Answer 18

1. Tumour development - stem cells divide rapidly, this can cause a tumour if not controlled
2. Disease transmission - is stem cells are infected with a virus., it could infect a patient and make them sicker
3. Rejection - If foreign stem cells were used, the body may not recognise it and trigger an immune response. Drugs could be taken but this would make them more susceptible to diseases
4. Ethical issues - each cell could be a potential human life (others say it is better to cure those suffering first)

Question 19

What does the cerebrum do?

Answer 19

• the right hemisphere controls muscles on the left and vice versa
• Different parts of the cerebrum are responsible for different things i.e. movement, intelligence, language, memory and vision

Question 20

What does the cerebellum do?

Answer 20

It is responsible for muscle coordination and balance

Question 21

What does the medulla oblongata do?

Answer 21

It controls unconscious activities like breathing and your heart rate

Question 22

What is CT scanning?

Answer 22

A CT scanner uses X rays to produce an image of the brain and it only shows the main structures of the brain but if a patient shows a diseases or damaged brain structure and lost some function, the function of the brain can be worked out

Question 23

What is PET scanning?

Answer 23

These use radioactive chemicals to show which parts of the brain are active. They show both structure and functions of the brain. they can be used to study disorders e.g. alzheimers

Question 24

What are the risks of treating damages in the brain and CNS?

Answer 24

1. its hard to repair damage to the nervous system as neurones in the CNS dont readily prepare themselves
2. Some parts of the CNS are hard to access (parts of the brain)
3. Treatments may lead to permanent damage (paralysis)

Question 25

How does the CNS coordinate a response?

Answer 25

``` 1 - Stimulus 2- Receptors 3. sensory neurones (synapse) 4. CNS (relay neurones) (synapse) 5. Motor neurones 6. Effector 7. Response ```

Question 26

What is the role of the myelin sheath?

Answer 26

The myelin sheath acts as an electrical insulator. This allows for the impulses to travel faster

Question 27

What do all neurones have?

Answer 27

They all have a nucleus and a cell body

Question 28

Describe the function and structure of a sensory neurone?

Answer 28

- One long dendron carries nerve impulses from receptor cells to the cell body, which is located in the middle of the neurone - One short axon carries nerve impulses from the cell body to the CNS

Question 29

Describe the function and structure of a motor neurone?

Answer 29

- Many short dendrites carry nerve impulses from the CNS to the cell body - One long axon carries nerve impulses from the cell body to effector cells

Question 30

Describe the function and structure of a relay neurone ?

Answer 30

- Many short dendrites carry nerve impulses from sensory neurones to the cell body - an axon carries nerve impulses from the cell body to motor neurones

Question 31

What is a synapse?

Answer 31

a synapse is the connection between 2 neurones

Question 32

What are neurotransmitters?

Answer 32

These are chemicals that transfer nerve signals across a synapse. They diffuse across the gap. electrical impulses are slowed down as the diffusion of neurotransmitters takes time

Question 33

What is the role of the cornea?

Answer 33

The cornea refracts light into the eye

Question 34

What is the role of the iris?

Answer 34

The iris controls how much light enters the pupil

Question 35

What is the role of the lens?

Answer 35

The lens also refracts light, focussing it on the retina

Question 36

What is the retina?

Answer 36

The light sensitive part which contain receptor cells called rods and cones

Question 37

Describe rods

Answer 37

rods are more sensitive in dim light but cant see colour

Question 38

Describe cones

Answer 38

Cones are sensitive to different colours but are not good in dim light

Question 39

What is the information from light converted into?

Answer 39

The impulses from light are converted to electrical impulses and the optic nerve carries these impulses from the receptors to the brain

Question 40

How does long-sightedness happen?

Answer 40

This happens when the lens is in the wrong shape and doesnt bend the light enough or the eyeball is too short - Light from near objects is brought into focus behind the retina - You can use a convex lens to correct them

Question 41

How does short-sightedness happen?

Answer 41

This happens when the lens is in the wrong shape or the eyeball is too long - light from far objects is brought into focus in front of the retina - you can use concave lenses to correct it

Question 42

What causes colour blindness?

Answer 42

It's caused when e.g. red or green cones in the retina aren't working properly. There's no cure as the cone cells cannot be replaced

Question 43

What are cataracts?

Answer 43

Cataracts are cloudy patches on the eye which dont let light enter the eye properly. It can cause blurred vision and make colours look less vivid and having difficulty seeing bright light. It can be treated by replacing a faulty lens

Question 44

How does changing the shape of the lens allow us to look at distant objects?

Answer 44

1) the ciliary muscle relaxes, which allows the suspensory ligaments to pull tight 2) This pulls the lens into a less rounded shape

Question 45

How does changing the shape of the lens allow us to look at close objects?

Answer 45

1) The ciliary muscle contracts, which allows the suspensory ligaments to relax 2) The lens becomes a more rounded shape, so light is refracted more