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GCSE Biology > Topic 2 - Cells And Control > Flashcards

Topic 2 - Cells And Control Flashcards

1
Q

What does the nucleus contain?

A

It contains your genetic material in the form of chromosomes.

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2
Q

What are chromosomes?

A

They’re coiled up lengths of DNA molecules.

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3
Q

How many copies of each chromosome do body cells normally have?

A

2.

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4
Q

What is the name for something having two copies of chromosomes?

A

Diploid.

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5
Q

When a cell divides by mitosis, describe the cells produced.

A

It makes two cells identical to the original cell - the nucleus of each new cell contains the same number of chromosomes as the original cell.

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6
Q

Why do multicellular organisms use mitosis?

A

To grow or replace cells that have been damaged.

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7
Q

What’s asexual reproduction?

A

When organisms use mitosis to reproduce.

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8
Q

What happens in interphase?

A

In a cell that’s not dividing, the DNA is all spread out in long strings. Before it divides, the cell has to grow and to 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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9
Q

What are the four stages of mitosis is order?

A

Prophase, metaphase, anaphase and telophase.

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10
Q

What happens in 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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11
Q

What happens in metaphase?

A

The chromosomes line up in the centre of the cell.

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12
Q

What happens in anaphase?

A

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

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13
Q

What happens in telophase?

A

Membranes form around each of the set of chromosomes. These become the nuclei of the two new cells. The nucleus has divided.

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14
Q

What happens in cytokinesis?

A

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

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15
Q

What is produced at the end of mitosis?

A

The cell has produced two new daughter cells. Each daughter cell contains exactly 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.

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16
Q

What is growth?

A

An increase in size and mass.

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17
Q

What’s cell differentiation?

A

The process by which a cell changes to become specialised for its job. Having specialised cells allows multicellular organisms to work more efficiently.

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18
Q

What’s cell division?

A

A cell dividing by mitosis.

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19
Q

What is cell elongation?

A

Where a plant cell expands, making the cell bigger so making the plant grow.

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20
Q

When you’re younger, what is most cell division for.

A

Growth, when you’re younger cells divide at a faster rate until you’re an adult.

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21
Q

When you’re fully grown, what is most cell division for?

A

Repair.

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22
Q

Where does growth usually occur in plants?

A

In the tips of roots and shoots.

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23
Q

How is the rate of cell division controlled?

A

By genes in an organisms DNA.

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24
Q

What is a tumour and how is it caused?

A

If there’s a change in one of the genes that controls cell division, the cell might start dividing uncontrollably. This can result in a tumour which is a mass of abnormal cells.

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25
What is cancer?
If the tumour invades and destroys surrounding tissue its called cancer.
26
What are undifferentiated cells called?
Stem cells.
27
Where are stem cells found?
In human embryos or adult bone marrow.
28
What's the difference between stem cells in the embryo and in the adult bone marrow?
Embryonic stem cells have the potential to divide and produce any type of cell at all, whereas bone marrow stem cells aren't as versatile as embryonic stem cells as they can only produce certain cell types.
29
What are found in meristems?
The only cells in plants that divide by mitosis.
30
Where is meristem tissue found?
They're found in the areas of plant that are growing e.g. the tips of the roots and shoots.
31
What do meristems produce?
Unspecialised cells that are able to divide and form any cell type in the plant.
32
What are the risks of stem cells in medicine?
Tumour development, disease transmission and rejection.
33
How can stem cells cause 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.
34
How can stem cells effect 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.
35
How can stem cells effect rejection?
If the transplanted cells aren't grown using the patients own stem cells, the patients body may recognise the cells as foreign and trigger an immune response to try and get rid of them.
36
What is the spinal chord?
A long column of neurones (nerve cells) that run from the base of the brain down to the spine.
37
What does the spinal chord do?
Relay information between the brain and the rest of the body.
38
What is the brain made up of?
Billions of interconnected neurones.
39
Describe the cerebrum.
The cerebrum is the largest part of the brain and is divided into two halves called the cerebral hemispheres.
40
What does each cerebral hemisphere control?
The right hemisphere controls the muscles on the left side of the body and the left hemisphere controls the muscles on the right side of the body.
41
What is the cerebrum responsible for?
Different parts of the cerebrum are responsible for different things, including movement, intelligence, memory, language and vision.
42
What is the cerebellum responsible for?
Muscle coordination and balance.
43
What does the medulla oblongata control?
Controls unconscious activities like breathing and you heart rate.
44
How does a CT scanner work?
It uses X-rays to produce an image of the brain.
45
What does a CT scanner do?
It shows the main structure of the brain but doesn't show the functions of them. It shows a diseased or damaged brain structure and the patient has lost some function, the function of that part of the brain can be worked out.
46
How do PET scanners work?
They use radioactive chemicals to show which parts of the brain are active when the person is inside the scanner.
47
How are PET scanners better then CT scanners?
PET scanners are very detailed and can be used to investigate both the structure and function of the brain in real time.
48
What does a PET scanner do?
PET scans can show if areas in the brain are unusually inactive or active, so they're useful for studying disorders that change the brain's activity.
49
What is the nervous system made up of?
Neurones that go to all parts of the body.
50
What are receptors?
Groups of cells that can detect change in your environment.
51
Whats the name for a change in the environment?
A stimulus.
52
What happens when a stimulus is detected by a receptor?
The information is converted to a nervous (electrical) impulse and sent along sensory neurones to the CNS.
53
What does the CNS do when it receives a nervous impulse?
The CNS coordinates a response and impulses travel through the CNS along relay neurones.
54
How does the CNS coordinate a response?
The CNS sends information to an effector along a motor neurone. The effector then responds accordingly.
55
Whats the order of the detection of a stimulus and the CNS' response?
Stimulus→Receptor→Sensory neurone→CNS→Motor neurone→Effector→Response.
56
What is a reaction time?
The time it takes you to respond to a stimulus.
57
What do dendrons and dendrites do?
Carry nerve impulses towards the cell body (of the neurone).
58
What do axons do?
Carry nerve impulses away from the cell body.
59
What are some axons surrounded by?
A myelin sheath.
60
What does a myelin sheath do?
It acts as an electrical insulator, speeding up the electrical impulse.
61
Why is an impulse carried quicker on a longer neurone then a shorter neurone?
Shorter neurones would require more neurones connected and connecting neurones together slows the impulse down.
62
What is the structure and function of a sensory neurone?
It has one long dendron that carries nerve impulses from receptor cells to the cell body, which is located in the middle of the neurone. it also has on short axon that carries nerve impulses from the cell body to the CNS.
63
What is the structure and function of the motor neurone?
It has many short dendrites that carry nerve impulses from the CNS to the cell body. It also has one long axon that carries nerve impulses from the cell body to the effector cells.
64
What is the structure and function of the relay neurone?
It has many short dendrites to carry nerve impulses from sensory neurones to the cell body. It also has an axon that carries nerve impulses from the cell body to motor neurones.
65
What is a synapse?
The connection between two neurones.
66
What is a neurotransmitter?
A chemical that transfers nerve signals by diffusing across the synapse.
67
Once the neurotransmitter has diffused across the synapse, what happens?
The neurotransmitters then set off a new electrical signal in the next neurone.
68
What are reflexes?
Automatic, rapid responses to stimuli.
69
What's the reflex arc?
The passage of information in a reflex (from receptor to effector).
70
What is the difference between a reflex and a normal response?
The impulses don't go the the brain, instead they go straight to the effector, therefore making the response quicker.
71
What does the cornea do?
Refracts light into the eye.
72
What does the iris do?
Controls how much light enters the pupil.
73
What does the lens do?
Refracts light, focusing it on the retina.
74
What is the retina?
It's the light sensitive part and it's covered in rods and cones, which detect light.
75
Describe rods.
Rods are more sensitive in dim light but can't sense colour.
76
Describe cones.
Cones are sensitive to different colours but are not so good in dim light.
77
What does the optic nerve do?
the information from light is converted int electrical impulses and the optic nerve carries these impulses from the receptors to the brain.
78
What benefit is there to the lens being elastic?
It allows the eye to focus light onto the retina by changing the shape of the lens.
79
How does your eye look at distant objects?
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.
80
How does your eyes look at near objects?
1) The ciliary muscle contracts, which slackens the suspensory ligaments. 2) The lens becomes a more rounded shape, so light is refracted more.
81
What are long-sighted people unable to do?
Focus on near objects.
82
What happens to make someone long-sighted?
The lens is the wrong shape and doesn't bend the light enough or the eyeball is too short. Light from near objects is brought into focus behind the retina.
83
How can long-sightedness be fixed?
Glasses or contact lenses with convex lenses.
84
What are short-sighted people unable to do?
Focus on distant objects.
85
What happens to make someone short-sighted?
The lens is the wrong shape and bends light too much or the eyeball is too long. Light from distant objects is brought into focus in front of the retina.
86
How can short-sightedness be fixed?
Glasses or contact lenses with a concave lens.
87
What causes red-green colourblindness?
When red or green cones in the retina are not working properly.
88
What is a cataract?
It's a cloudy patch on the lens, which stops light from being able to enter the eye normally.
89
What are the effects of having a cataract?
People with cataracts are likely to have blurred vision. They may also experience colours looking less vivid.
90
How can a cataract be treated?
Replacing the faulty lens with an artificial one.

GCSE Biology (9 decks)

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