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Edexcel GCSE Biology Higher > Topic 2 - Cells And Control > Flashcards

Topic 2 - Cells And Control Flashcards

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1
Q

Interphase:

A
  • The DNA is all spread out in long strings.
  • The cell has to grow and increase the amount of sub-cellular structures such as mitochondria and ribosomes.
  • It then duplicates its DNA - so there’s one copy for each new cell. The DNA is copied and forms x-shaped chromosomes. Each ‘arm’ of the chromosome is an exact duplicate of the other.
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2
Q

Prophase:

A
  • The chromosomes condense, getting shorter and fatter.
  • The membrane around the nucleus breaks down and the chromosomes lie free in the cytoplasm.
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3
Q

Metaphase:

A
  • The chromosomes line up at the centre of the cell.
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4
Q

Anaphase:

A
  • Spindle fibres pull the chromosomes apart.
  • Then, the chromatids are pulled to opposite ends of the cell.
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5
Q

Telophase -

A
  • Membranes form around each of the sets of chromosomes.
  • These become the nuclei of the two new cells - the nucleus has divided.
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6
Q

Cytokinesis -

A
  • The cytoplasm and cell membrane divide to form two separate cells.
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7
Q

Outcome of mitosis

A
  • Two new genetically identical diploid daughter cells.
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8
Q

Cell Differentiation Definition -

A
  • The process by which a cell changes to become specialised for its job.
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9
Q

How does a cell divide? -

A
  • By Mitosis.
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10
Q

Cell Elongation:

A
  • Where a plant cell expands, making the cell bigger and so making the plant grow.
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11
Q

Stem Cell Definition:

A
  • Undifferentiated cells that can divide by mitosis to become new cells, which then differentiate.
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12
Q

Stem Cells in Embryos:

A
  • Have the potential to divide and produce any kind of cell at all.
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13
Q

What are stem cells important for generally?

A
  • The growth and development of organisms.
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14
Q

Stem Cells in Adults:

A
  • Only found in certain places e.g bone marrow.
  • Not as versatile as embryonic stem cells (can’t produce any cell type at all, only certain ones).
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15
Q

What are stem cells used for in adults?

A
  • Replace damaged cells e.g make new skin or blood cells.
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16
Q

Meristems:

A
  • Found in areas of a plant that grow e.g tips of roots, shoots.
  • Produce unspecialised cells
  • These go on to form specialised tissues like xylem and phloem.
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17
Q

Advantages of Stem Cells:

A

1) - Adult stem cells used to cure diseases. e.g sickle cell anaemia can be cured with a bone marrow transplant.

2) - Scientists have experimented with extracting stem cells from very early human embryos and growing them. Under certain conditions, the stem cells can be stimulated to differentiate into specialised cells.

3) - Can use stem cells to create specialised cells to replace those which have been damaged by disease or injury e.g new cardiac muscle cells could be transplanted into someone with heart disease.

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18
Q

Disadvantages of Stem Cells -

A

1) - Rejection: Patient’s body may recognise the cells as foreign and trigger an immune response to try and get rid of them. The patient can take drugs to suppress this response, but this makes them susceptible to diseases.

2) - Stem cells divide very quickly. These cells may form a tumour.

3) - Viruses live inside cells. If donor stem cells 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.

4) - Ethical issues including that human embryos shouldn’t be used for experiments because each one is a potential human life. Others think that the aim of curing patients who are suffering should be more important than the potential life of the embryos.

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19
Q

Definition of Sensory Receptors -

A

Groups of cells that can detect a change in your environment

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20
Q

Definition of a stimulus -

A

A change in the environment

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21
Q

What happens when a stimulus is detected?

A

1) - It is detected by receptors
2) - And the information is converted to a nervous (electrical) impulse
3) - These are sent along sensory neurones to then CNS (brain + spinal cord).
4) - The CNS sends information to an effector (muscle or gland) along a motor neurone.
5) - The effector then responds accordingly e.g muscle contracts or gland secretes hormone.

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22
Q

What is the CNS

A

Central Nervous System - Brain and Spinal Cord

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23
Q

What is an effector?

A

A muscle or gland

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24
Q

What do dendrites and dendrons do?

A
  • Carry nerve impulses towards the body
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25
Q

What do axons do?

A
  • Axons carry nerve impulses away from the body.
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26
Q

What does a myelin sheath do?

A
  • Acts as an electrical insulator, speeding up the electrical impulse.
27
Q

What is the effect of having long neurones?

A
  • Speeds up electrical impulse
28
Q

Structure of a sensory neurone:

A
  • Receptor cells > dendron > axon
  • Direction of Impulse >
29
Q

Function of Sensory Neurones -

A
  • 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.
30
Q

Structure of Motor Neurones

A
  • Dendrites > Myelin Sheath > Axon > Effector Cells
  • Direction Of Impulse >
31
Q

Function of Motor Neurones

A

1) - Many short dendrites carry nerve impulses from the CNS to the cell body.

2) - One long axon carries nerve impulses from the cell body to effector cells.

32
Q

Structure of Relay Neurone:

A
  • Dendrites > Cell Body > Axon
  • Direction of Impulse >
33
Q

Function of Relay Neurone:

A

1) - Many short dendrites carry nerve impulses from sensory neurones to the cell body.

2) - An axon carries nerve impulses from the cell body to motor neurones.

34
Q

Synapse Definition -

A

The gap between two neurones.

35
Q

How is the nerve signal transferred?

A
  • By chemicals called neurotransmitters.
  • These diffuse across the synapse (gap).
36
Q

What do neurotransmitters do?

A

1) - Transfer nerve signals
2) - These diffuse across the gap (synapse).
3) - They then set off a new electrical signal at the next neurone.

37
Q

Speed of transmission of a nervous impulse:

A
  • Very fast
  • But, it is slowed down at the synapse because the diffusion of neurotransmitters across the gap takes time.
38
Q

Definition of a reflex:

A
  • Automatic, rapid responses to a stimuli which reduce the chances of being injured.
39
Q

Definition of a reflex arc -

A
  • The passage of information in a reflex (from receptor to effector).
40
Q

Where do the neurones in reflex arcs go through?

A
  • The spinal cord
  • Or an unconscious part of the brain.
41
Q

What happens when a stimulus is detected by receptors? Example with a bee

A

1) - Impulses are sent along a sensory neurone to a relay neurone in the CNS.

2) - When the impulses reach a synapse between the sensory and relay neurone, they trigger neurotransmitters to be released. These cause impulses to be sent along the relay neurone.

3) - When the impulses reach a synapse between the relay neurone and a motor neurone, neurotransmitters are released and cause impulses to be sent along the motor neurone.

4) - The impulses than travel along the motor neurone to the muscle. The muscle (effector) then contracts and moves your hand away from the bee.

42
Q

How do reflexes help to protect the eye?

A

1) - Very bright light can damage the eye so you have a reflex to protect it.

2) - Light receptors in the eye detect very bright light and send a message along a sensory neurone to the brain.

3) - The message then travels along a relay neurone to a motor neurone, which tells circular muscles in the iris to contract, making the pupil smaller.

43
Q

Definition of the spinal cord -

A
  • A long column of neurones (nerve cells) that run from the base of the brain down the spine.
44
Q

Function of the spinal cord -

A
  • Relays information between the brain and the rest of the body.
45
Q

Function of the Cerebrum:

A

1) - Right Hemisphere controls muscles on the left side of the body.
2) - Left Hemisphere controls muscles on the right side of the body.
3) - Movement, intelligence, memory, language and vision.

46
Q

Function of the Cerebellum:

A
  • Muscle co-ordination and balance.
47
Q

Function of the medulla oblongata:

A
  • Controls unconscious activities such as breathing and heart rate.
48
Q

CT Scanning: What does it do?

A
  • Uses x-rays to produce an image of the brain.
  • It shows the main structures of the brain, but it doesn’t show the functions of them.
  • However, if a CT scan shows a diseased/damaged brain structure and the patient has lost some function, the function of that part of the brain can be worked out e.g if a patient cannot see then that area is involved in vision.
49
Q

What do PET scanners do?

A
  • use radioactive chemicals to show which parts of the brain are active.
  • Very detailed, can investigate the structure and function of the brain in real time.
  • Can show if areas in brain are unusually active/inactive, so they are useful for studying disorders that change the brain’s activity e.g reduction in brain activity with Alzheimer’s.
50
Q

Why can treating problems in the CNS be tricky?

A

1) - Hard to repair damage to the nervous system as neurones in the CNS don’t readily repair themselves.

2) - Parts of the nervous systems e.g certain parts of the brain are difficult to access.

3) - Can lead to permanent damage. E.g surgery on the spine could lead to permanent spine damage.

51
Q

Cornea -

A
  • Refracts (bends) light into the eye.
52
Q

Iris -

A
  • Controls how much light enters the pupil (the hole in the middle).
53
Q

Lens -

A
  • Refracts light, focusing it onto the retina.
54
Q

Retina -

A
  • The light-sensitive part
  • Covered in receptor cells called rods and cones, which detect light.
55
Q

Rods -

A
  • Detect light
  • More sensitive in dim light
  • Cannot sense colour.
56
Q

Cones -

A
  • Detect light
  • Sensitive to different colours
  • Not as good in dim light
57
Q

How is information from light converted in the eye?

A
  • Into electrical impulses.
  • The optic nerve carries these impulses from the receptors to the brain.
58
Q

Colour-Blindness

A
  • These people cannot tell the difference between certain colours.
  • The most common form is red-green colour blindness (red/green cones in retina don’t work properly).
  • No cure as cone cells cannot be replaced.
59
Q

Cataracts -

A
  • A cloudy patch on the lens, which stops light from being able to enter the eye normally.
  • Colours look less vivid
  • Difficulty seeing bright light.
  • Treat it by replacing the faulty lens with an artificial one.
60
Q

How do we look at close objects?

A
  • The ciliary muscle contracts, which slackens the suspensory ligaments.
  • The lens becomes a more rounded shaped, so light is refracted more.
61
Q

How do we look at distant objects?

A

1) - The ciliary muscle relaxes, which allows the suspensory ligaments to pull tight.

2) - This pulls the lens into a less rounded shape so light is refracted less.

62
Q

Long-sightedness:

A
  • Lens is the wrong shape and doesn’t bend light enough or when the eyeball is too short.
  • Light from near objects is brought into focus behind the retina.
  • Use glasses or contact lenses with a convex lens to correct it.
63
Q

Short-sightedness:

A

1) - When the lens is the wrong shape and bends light too much, or when the eyeball is too long.

2) - Light from distant objects is brought into focus in front of the retina.

3) - Use glasses or contact lenses with a concave lens to correct it.

64
Q

What does having specialised cells allow?

A
  • Having specialised cells allows multi cellular organisms to work more efficiently.

Edexcel GCSE Biology Higher (11 decks)

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