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BIOLOGY > SB2: cells and control > Flashcards

SB2: cells and control Flashcards

1
Q

where does DNA exist?

A

in the nucleus as thin strands

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2
Q

how are chromosomes formed?

A

-DNA condenses and coils together -each chromosome is made from a single molecule of DNA
-DNA contains a code for the production of a gene

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3
Q

how many chromosomes do humans have?

A

46 (23 pairs)
-each chromosome in a pair carries the same type of genes

-23rd pair = sex chromosome
(XX in females, XY in males)

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4
Q

when does mitosis occur?

A

when an organism grows, an organism becomes damaged & needs to produce new cells

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5
Q

which type of ways do organisms reproduce?

A

asexually and sexually

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6
Q

cell cycle

A

series of events that cells go through as they grow and divide

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7
Q

steps of cell cycle

A
  1. cell growth
  2. DNA synthesis
  3. more growth, DNA is checked for errors
  4. mitosis, cytoplasm separates & 2 cells are tormed
  5. cell stops dividing
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8
Q

mitosis

A

cell division in which 2 genetically identical diploid daughter cells are formed

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9
Q

stages of mitosis in order:

A
  1. interphase
  2. prophase
  3. metaphase
  4. anaphase
  5. telophase
  6. cytokines
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10
Q

interphase

A

-the cell spends most of its life in this phase (90%)
-DNA in chromosomes copies itself ready for mitosis

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11
Q

prophase

A

spindle fibres form, nuclear membrane disappears

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12
Q

metaphase

A

chromosomes line up in the middle of the cell

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13
Q

anaphase

A

chromosomes are pulled apart by spindles to different ends of the cell

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14
Q

telophase

A

new membranes form around the chromosomes at each end of the cell

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15
Q

cytokines

A

cytoplasm separates, 2 daughter cells are formed

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16
Q

length of time in phase

A

observed number of cells at that stage/ total number of cells observed × total length of time of cell cycle

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17
Q

cancer cell facts

A

-divide uncontrollably
-undifferentiated & don’t carry out their usual function

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18
Q

what is a tumour?

A

a group of cancerous cells

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19
Q

benign tumour

A

-grows slowly
-grows within membrane
-doesn’t invade other parts of the body
-easily removed

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20
Q

malignant tumour

A

-grows fast
-invades neighbouring tissue
-as the tumour grows, cancer cells detach and form secondary tumours in other parts of the body (metastasis

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21
Q

metastatis steps

A
  1. a tumour secretes chemicals
  2. the chemicals stimulate blood vessel growth and blood vessels grow around the tumour
  3. cancer cells detach from the tumour and are transported in the blood
  4. the cell squeezes through a blood capillary wall & the cell divides, a secondary tumour starts to grow
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22
Q

causes of cancer

A

-genetic factors
-carcinogens, which cause mutations (chemicals or other agents) many are needed for this so cancer risk increases with age
-(lifestyle factors) viruses linked with cancer (eg: HPV), carcinogens in cigs, UV (ionising) leads to skin cancer, diet (fat & salt intake)

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23
Q

zygote differentiation

A

animals and plants produced by sex start life as a zygote, this needs to divide by mitosis to produce a multicellular organism

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24
Q

where does mitosis happen in different organisms?

A

-all throughout animal bodies
-meristem of plants (roots & shoots) plants elongate as they grow

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25
Q

examples of differentiation in animal cells

A

-(circulatory system cells) defend body, regulate temperature
-(muscular system cells) bring about movement

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26
Q

examples of differentiation in plant cells

A

(palisade mesophyll) carry out photosynthesis
(meristems) produce new cells as they divide

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27
Q

monitoring growth

A

-baby growth is measured in mass, length and head circumference
-it’s measured with percentile growth charts
-drastic changes in percentile cause alarm

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28
Q

meaning of percentile

A

-if baby is in 50th percentile for height, in every 100 babies 50 will be shorter & 50 taller
-if baby is in 10th percentile for weight, in every 100 babies, 10 will be lighter & 90 will be heavier

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29
Q

stem cells

A

undifferentiated cells

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30
Q

what is an embryo in early stages?

A

stem cells

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31
Q

where are stem cells located in the human body?

A

nose, brain, eyes, blood

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32
Q

what can adult vs embryonic cells differentiate into?

A

adult = related cell types only
embryonic = all cells

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33
Q

meristems in plants

A

can differentiate into any plant cell type throughout the life of the plant. new cells are continuously produced near the top, as the cells get older further away from the top they become differentiated, enlarge & develop vacuole

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34
Q

using human stem cells

A

-stem cells can be transported into patients to treat medical conditions & disease/replace damaged or destroyed cells

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35
Q

examples of using stem cells

A

(adult stem cells) bone marrow transplants are used in blood cell cancer and they differentiate into different type of blood cells

36
Q

benefits & risks of stem cells

A

benefits
-can treat patients with cUrrently untreatable conditions
-growing organs for transplants
-medical research

risks
- (clinical issues) no guarantee of success
-difficult to find suitable stem cell donors -
-mutations have been observed in stem cells
-some have been seen to behave like cancer cells
-cultures stem cells could be contaminated with viruses & transferred to a patient

-(ethical issues) source of stem cells is unused embryos produces by IVF, embryos could start to be seen as if they can’t develop into a person

-(social issues) patients could be exploited by paying for expensive treatments that may not work

37
Q

all control systems include:

A

-receptors (detect stimuli, something that sets off a reaction in the nervous system

-the coordination centre (brain, spinal
cord) which receives & processes info from receptors around the body

-effectors (muscles & glands) bring about responses, restore optimum levels (temp, blood glucose levels)

38
Q

nerve cells

A

-bundle of neurones which carry electrical impulses from one place to another

39
Q

what are the different types of neurones?

A

sensory, relay and motor

40
Q

what features do neurones have in common?

A

-axon: (long fibre) insulated by a myelin sheath, axons are long so that they can carry messages up and down the body

-dendrons: (tiny branches) branch further as dendrites at each end, receive incoming impulses from other neurones

41
Q

what happens when two neurones meet?

A

-there’s a synapse (small gap), here the electrical signal must be converted into a chemical one & then converted back into an electrical one on the other side of the synapse where the next neurone starts

42
Q

steps when two neurones meet

A
  1. an electric impulse travels along the first axon
  2. this triggers the nerve-ending of a neurone to release chemical messengers (neurotransmitters)
  3. these chemicals diffuse across the synapse & bind with receptor molecules on the membrane of the second neurone
  4. the receptor molecules on the second neurone only bind to the specific neurotransmitters from the first neurone
  5. this stimulates the second neurone to transmit an electrical impulse
43
Q

receptors -> effectors

A

-receptor cells detect a change in the environment (a stimulus) and then start electrical signals along the neurones
-these signals move towards the CNS
-messages are then sent back along the different neurones to muscles which contract or relax & glands that secret hormones (effectors)

44
Q

how actions are formed

A

stimulus -> receptor -> (sensory neurone) -> coordinator (relay neurones) -> (motor neurone) -> effector -> response

45
Q

sense organs

A

a group of receptor cells responding to specific stimuli

46
Q

sense organs & their stimuli

A

skin (touch, temp)
tongue (chemicals in food & drink)
nose (chemicals in air)
eye (light)
ear (sound)

47
Q

what does a reflex arc do?

A

-provides an automatic & rapid response to a stimulus & minimises any damage to a body

48
Q

how does a reflex arc work?

A

it follows an overall sequence through the nervous system by not including the conscious part of the brain and making reactions quicker

49
Q

reflex arc steps

A

-receptor in the skin detects a stimulus
-sensory neurone sends electrical impulses to relay neurone, which are located in the spinal cord
-they connect sensory neurones to motor neurones.
-motor neurone sends electrical impulses to an effector
-effector produces a response

50
Q

what does the brain do?

A

controls body functions

51
Q

what is the brain made up of?

A

billions of interconnected neurones

52
Q

cerebral hemispheres

A

-the right and left halves of the cerebrum
-right controls left half of body, left controls right half of body
-controls senses, intelligence, personality, conscious thought, language & verbal memory

53
Q

cerebellum

A

balance & coordination

54
Q

medulla

A

(unconscious activities) controls heartbeat and breathing

55
Q

hypothalamus

A

regulates body temperature

56
Q

investigating the brain

A

-neuroscientists have mapped different regions of the brain to particular functions by studying those with brain damage

57
Q

phineas gage (1848)

A

-iron rod went through his skull
-he survived & could still walk & talk but his personality changed due to damage in parts of the brain the rod went through
-scientists used this to see the effect of injuries on brain activity

58
Q

EEG

A

-a recording of the waves of electrical activity that sweep across the brain’s surface
-these waves are measured by electrodes placed on the scalp

59
Q

electrical stimulation

A

-stimulate different parts of the brain with weak electrical current & ask patients to describe what they experienced

60
Q

MRI

A

-strong magnetic fields & radio waves to show the details of brain structure & function
-patients asked to perform different tasks & scientists look at the scan to see which parts of the brain are active

61
Q

CT

A

-patient lies in a bed and passes through a ring of equipment
-ring takes a series of x-rays from different angles these are processed by a computer
-this lets doctors see inside the brain & other parts of the body

62
Q

PET

A

-detect gamma rays that radiate from a tracer
-detect high levels of metabolic reactions in a person
-person consumes tracer before scan
-tracer travels to high levels of metabolic reactions (often tumours)
-detect cancer

63
Q

what is brain damage?

A

loss of cells in the brain

64
Q

what are some causes of brain damage?

A

-strokes, excessive alcohol consumption, brain tumours

65
Q

long term symptoms of brain damage

A

-speech/movement problems, memory loss, personality changes

66
Q

what can impacts to the skull result in?

A

brain swelling as excess fluid is produced

67
Q

brain surgery facts

A

-may be needed to remove a tumour or excess fluid
-treating brain disorders can be difficult as the brain is complex & delicate
-surgery may create more damage/ side effects
-brain surgery can affect a patients quality of life

68
Q

retina

A

-the light-sensitive inner surface of the eye
-contains light receptors
-cone cell = colour, rod cell = black &
white, more sensitive, better for dim life

69
Q

iris (coloured part)

A

-controls how much light enters the pupil

70
Q

lens

A

-changes shape to focus light onto the retina

71
Q

cornea

A

-refracts light, bends it as it enters the eye

72
Q

optic nerve

A

carries neural impulses from the eye to the brain

73
Q

sclera

A

-tough white outer layer of eye, helps protect eye from injury

74
Q

the pupil reflex

A

-light entering the eye is controlled by the reflex action

75
Q

what happens to the pupil in dim light?

A

-pupils dilate
-radial muscles of iris contract, circular relax

76
Q

what happens to the pupil in bright light?

A

-pupils contract
-radial muscles of iris relax, circular contract

77
Q

how the eye works

A

accommodation (changing the shape of the lens to focus on near or distant objects

78
Q

near object

A
  • lens becomes thicker & allows light rays to refract stronger
    -ciliary muscles contract
    -suspensory ligaments loosen
    -muscle tension on lens is low
79
Q

distant object

A
  • lens is pulled thin
    -ciliary muscles relax
    -suspensory ligaments tighten
    -muscle tension on lens is high
80
Q

short sight (myopia)

A

-can see near objects clearly, can’t focus on distant objects
-eyeball is elongated/lens is too thick & curved
-concave lens

81
Q

long sight

A

-can see distant objects clearly, can’t focus near
-eyeball is too short or lens isn’t thick enough
-convex lens used

82
Q

laser surgery (eye correction)

A

-reshapes cornea surgically

83
Q

replacement lens (eye correction)

A

-artificial lens placed in front of original lens through a small cut in the cornea to correct defects

84
Q

contact lenses (eye corrections)

A

-are in contact with eye
-float on cornea & for use
-refract the light

85
Q

cataract

A

-cloudiness due to built up protein
-fixed by removing the lens & replacing it with a plastic lens

BIOLOGY (9 decks)

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