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GCSE Edexcel Biology > B2 - Cells and Control > Flashcards

B2 - Cells and Control Flashcards

1
Q

Define

chromosone.

A

a coiled up length of DNA molecules

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2
Q

What is a

diploid cell?

A

a cell which has two copies of each chromosone

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3
Q

What is

mitosis

used for? (2)

A
  • growth in multicellular organisms
  • replacing cells that have been damaged in multicellular organisms
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4
Q

Define

asexual reproduction.

A

the use of mitosis to reproduce

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5
Q

What are the

main stages of the cell cycle?

(6 stages)

A

International - Interphase
Propaganda - Prophase
Makes - Metaphase
Animals - Anaphase
Telecommunicate - Telophase
Cylently - Cytokinesis

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6
Q

What occurs during

interphase?

(2 things)

A
  • the cell grows and increases the amount of subcellular structures (e.g. mitochondria and ribosomes)
  • the DNA is duplicated and forms X-shaped chromosones

each ‘arm’ (chromatid) of the chromosone is an exact duplicate of the other

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7
Q

What are the

four stages of mitosis?

A
  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase
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8
Q

What occurs during

prophase?

(2 things)

A
  • the chromosones condense, getting shorter and fatter
  • the membrane around the nucleus breaks down and the chromosones lie free in the cytoplasm
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9
Q

What occurs during

metaphase?

(1 thing)

A

the chromosones line up at the centre of the cell

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10
Q

What occurs during

anaphase?

(2 things)

A
  • spindle fibres pull the chromosones apart
  • the chromatids are pulled to opposite ends of the cell
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11
Q

What occurs during

telophase?

(2 things)

A
  • membranes form around each of the sets of chromosones
  • cytokinesis occurs

these become the nuclei of the two new cells - the nucleus has divided

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12
Q

What occurs during

cytokinesis?

A

the cytoplasm and cell membrane divide to form two separate cells

(this is part of telophase)

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13
Q

What is produced at the end of

mitosis?

A

two genetically identical diploid daughter cells which are genetically identical to the parent cell

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14
Q

What equation allows you to calculate

number of cells after multiple divisions of a cell by mitosis?

A

number of cells = 2^number of divisions

N = 2^n

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15
Q

Define

growth.

A

an increase in size or mass

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16
Q

Define

cell differentiation.

A

the process by which a cell changes to become specialised for its job

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17
Q

What are the benefits of

specialised cells?

A

they allow multicellular organisms to work more efficiently

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18
Q

Define

cell elongation.

A

the expansion of a plant cell, making the cell bigger and so making the plant grow

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19
Q

How does

cancer occur?

(4 steps)

A
  1. The rate at which cells divide by mitosis is controlled by the chemical instructions (genes) in an organism’s DNA.
  2. If there’s a change in one of the genes that controls cell division, the cell may start dividing uncontrollably.
  3. This can result in a mass of abnormal cells called a tumour.
  4. If the tumour invades and destroys surrounding tissue it is called cancer.
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20
Q

When might a doctor choose to investigate a baby’s size?

(4)

A
  • if they are above the top percentile line
  • if they are below the bottom percentile line
  • if their size increases or decreases by two or more percentile lines over time
  • if there’s an inconsistent pattern
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21
Q

Define

stem cell.

A

an undifferentiated cell

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22
Q

Where are

stem cells found in adults?

A

bone marrow

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23
Q

What are the differences between

adult stem cells and embryonic stem cells?

(and why?)

A

adult stem cells aren’t as versatile, they can only produce certain cell types

this is because in adults, the stem cells are used to replaced damaged cells (e.g. to make new skin cells or blood cells)

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24
Q

Where are

meristems found in plants?

and why?

A

in the areas of the plant that are growing ( tips of the roots and shoots)

(this is because they are the only cells that divide by mitosis)

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25
Q

What are the differences between

adult stem cells and meristems?

A

unlike human stem cells, the meristems produce unspecialised cells that can divide and differentiate into any type of cell for as long as the plant lives

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26
Q

What are the

three main risks of stem cells in medicine?

A
  • tumour development
  • disease transmission
  • rejection
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27
Q

Describe the risk that

tumour development

from stem cells poses.

A

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.

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28
Q

Describe the risk that

disease transmission

from stem cells poses.

A

Viruses live inside cells. If donor stem cells are infected with a virus and isn’t picked up, the virus could be passed on to the recipient and so make them sicker.

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29
Q

Describe the risk that

rejection

from stem cells poses.

A

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.

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30
Q

What are the

ethical issues surrounding embryonic stem cell research?

and what is the counter argument to this?

A

Some people argue that human embryo’s 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.

31
Q

What is the

spinal cord?

A

a long column of neurones (nerve cells) that run from the base of the brain down the spine.

32
Q

What does the

spinal cord

do?

A

it relays information between the brain and the rest of the body

33
Q

What are the

three main parts of the brain?

(that you need to know about)

A
  • cerebrum
  • cerebellum
  • medulla oblongata
34
Q

What are some key points about the

cerebrum?

(4 points)

A
  • it is the largest part of the brain
  • it is divided into two halves called cerebral hemispheres
  • the right hemisphere controls muscles on the left side of the body (and vice versa)
  • different parts of the cerebrum are responsible for different things
35
Q

What are some examples of things that the

cerebrum

is responsible for?

(5)

A
  • movement
  • intelligence
  • memory
  • language
  • vision
36
Q

What are some examples of things that the

cerebellum

is responsible for?

(2)

A
  • muscle coordination
  • balance
37
Q

What are some examples of things that the

medulla oblongata

is responsible for?

(2)

A
  • breathing
  • heart rate

(unconscious activities)

38
Q

How does a

CT scan

work?

A

it uses x-rays to produce an image of the brain

39
Q

What does a

CT scan show?

(and what does it not show?)

A

it shows the main structures in the brain

it doesn’t show the functions of them

40
Q

How does a

PET scan

work?

A

it uses radioactive chemicals to show which parts of the brain are active when the person is inside the scanner

41
Q

What does a

PET scan

show?

A

it shows both the structure and the function of the brain in real time

this is very detailed

it can also show if areas of the brain are unusually inactive or active, so they are useful for studying disorders that change the brain’s activity

42
Q

What are the difficulties of

treating problems in the CNS?

(3)

A
  • it is hard to repair damage to the nervous system
  • if a problem occurs in a part of the nervous system that’s not easy to access, it can be hard to treat
  • treatment for problems in the nervous system may lead to permanent damage
43
Q

What are

sensory receptors?

A

groups of cells that can detect a change in your environment

44
Q

Define

stimulus.

A

a change in the environment

45
Q

Define

reaction time.

A

the time it takes you to respond to a stimulus

46
Q

Describe how the

CNS coordinates a response.

(to a stimulus) (5 steps)

A
  1. A stimulus is detected by receptors.
  2. This information is converted to a nervous (electrical) impulse and sent along sensory neurones to the CNS.
  3. The CNS coordinates the response (impulses travel through the CNS along relay neurones).
  4. The CNS send information to an effector (muscle or gland) along a motor neurone.
  5. The effector then responds accordingly.
47
Q

What are some features of

all neurones?

(2)

A
  • a cell body with a nucleus (plus cytoplasm and other subcellular structures)
  • the cell body has extensions that connect to other neurones
48
Q

What is the

structure of a sensory neurone?

(and each part’s purpose)

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

receptor cells > dendron —-> cell body –> axon

49
Q

What is the

structure of a motor neurone?

(and each part’s purpose)

A
  • 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

dendrites > cell body -> axon —-> effector cells

the axon is surrounded by a myelin sheath

50
Q

What is the purpose of a

myelin sheath?

A

it acts as an electrical insulator, speeding up the electrical impulse

51
Q

What is the

structure of a relay neurone?

(and each part’s purpose)

A
  • 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

dendrites —> cell body —-> axon

52
Q

Define

synapse.

A

the connection between two neurones

53
Q

What occurs at a

synapse?

A
  1. The nerve impulse reaches the end of the neurone.
  2. The nerve signal is transferred by chemicals called neurotransmitters, which diffuse across the gap.
  3. The neurotransmitters then set off a new electrical signal in the next neurone,

The transmission of a nervous impulse is very fast, but it is slowed down a bit at the synapse because the diffusion of neurotransmitters across the gap takes time.

54
Q

Define

reflex.

and state why it is helpful.

A

an automatic, rapid response to stimuli

it can reduce the chances of being injured

55
Q

Define

reflex arc.

A

the passage of information in a reflex

(from a receptor to effector)

56
Q

How does a

reflex work?

(4 steps)

A
  1. A stimulus is detected by receptors.
  2. Impulses are sent along a sensory neurone to a relay neurone in the CNS.
  3. The impulses then travel along the motor neurone to the effector.
  4. The effector then causes the muscle or gland to respond.
57
Q

How does a

reflex protect the eye from bright light?

(2 steps) and why?

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

this is because very bright light can damage the eye

58
Q

What is the purpose of the

cornea?

A

to refract light into the eye

59
Q

What is the purpose of the

iris?

A

to control how much light enters the pupil

60
Q

What is the purpose of the

lens?

A

refract light, focusing it onto the retins

61
Q

What is the

retina?

A

the light sensitive part of the eye that is covered in receptor cells called rods and cones, which detect light

62
Q

What are

rods?

A

receptor cells that are more sensitive in dim light but can’t sense colour

63
Q

What are

cones?

A

receptor cells that are sensitive to different colours but are not so good in dim light

64
Q

How does the information from the light get to the

brain?

A

The information from light is converted into electrical impulses. The optic nerve carries these impulses from the receptors to the brain.

65
Q

How does the eye focus light onto the retina to look at

distant objects?

(2 steps)

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.
66
Q

How does the eye focus light onto the retina to look at

close objects?

(2 steps)

A
  1. The ciliary muscle contracts, which slackens the suspensory ligaments.
  2. The lens becomes a more rounded shape so light is refracted more.
67
Q

What is

long-sightedness?

and why does this occur?

A

when people are unable to focus on near objects

This occurs when 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.

68
Q

What type of lens fixes

long-sightedness?

A

a convex lens

69
Q

What is

short-sightedness?

and why does this occur?

A

when people are unable to focus on distant objects

This occurs when the lens is the wrong shape and bends the light too much or the eyeball is too long.
Light from distant objects is brought into focus in front of the retina.

70
Q

What type of lens fixes

short-sightedness?

A

a concave lens

71
Q

What is

colour blindness?

A

When people can’t tell the difference between certain colours.

The most common form of this is red-green colour blindness.
This occurs when red or green cones in the retina are not working properly.
There’s no cure for colour blindness at the moment because the cone cells can’t be replaced.

72
Q

What is a

cataract?

A

a cloudy patch on the lens, which stops light from being able to enter the eye normally

73
Q

What are the consequences of a

cataract?

and how can this be treated?

A

the person might experience colours looking less vivid and have difficulty seeing in bright light

replacing the faulty lens with an artificial one

GCSE Edexcel Biology (10 decks)

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