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Biology Topic by Topic > Topic 2 cells and control > Flashcards

Topic 2 cells and control Flashcards

1
Q

what do most cells in your body have

A

a nucleus that contains your genetic material in the form of chromosomes

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2
Q

what are chromosomes

A

coiled up lengths of DNA molecules

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3
Q

what happens when a cell divides by mitosis

A

it makes two diploid genetically identical daughter cells and the nucleus of each contains the same amount as the original cell

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4
Q

body cells in what organisms divide by mitosis

A

multicellular

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5
Q

what do multicellular organisms use mitosis for

A

to grow or replace cells that have been damaged

reproduce (asexual reproduction)

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6
Q

what is interphase

A
  • In a cell that’s not dividing the DNA is all spread out into long strings
  • before it divides the cell has to grow and to increase the amount of subcellular structures
  • It then duplicates its DNA so there’s one copy for each new cell
  • the DNA is copied and forms X shaped chromosomes and each arm of the chromosome is an exact duplicate of the each other
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7
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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8
Q

what happens in metaphase

A
  • the chromosomes line up in the middle of the cell
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9
Q

what happens in anaphase

A

cell fibres pull the chromosomes apart and the two arms of each chromosome go to opposite ends of the cell

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10
Q

what happens in 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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11
Q

what happens in cytokinesis

A
  • the cytoplasm and cell membrane divide to form two separate cells
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12
Q

how can you calculate the number of cells a certain amount of cell divisions

A

2 the power of n

for example after 5 cell divisions there will be 32 cells because 2 to the power of 5 is 32

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13
Q

how do plants grow

A

differentiation, division , elongation

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14
Q

what is 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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15
Q

what is cell division

A

mitosis

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16
Q

what is cell elongation

A

where a plant cell expands making the cell bigger and so the plant grow

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17
Q

discuss growth in animals

A
  • happens by cell division
  • animals tend to grow while they’re young and then they reach full growth and stop growing
  • so when you are young cells divide at a fast rate but once your an adult most cell division is for repair
  • the cells divide to replace old or damaged cells
  • this also means in animals cell differentiation is lost at an early stage
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18
Q

discuss growth in plants

A
  • growth in height mainly due to cell elongation
  • cell division usually just happens in the tips of the roots and shoots in areas called meristems
  • but plants often grow continuously (even really old trees will keep putting out new branches)
  • so plants continue to differentiate to develop new parts like leaves and roots
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19
Q

discuss cancer in relation to cell division and growth

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

why do we use percentile charts

A

to assess a child’s growth over time so that an overall pattern in development can be seen and any problems highlighted (e.g obesity, malnutrition, dwarfism)
for example a baby growth is regularly monitored after birth to make sure its growing normally
- length
- mass
- head circumference

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21
Q

what are undifferentiated cells

A

stem cells

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22
Q

where are adult stem cells found

A

bone marrow

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23
Q

why do embryonic stem cells need to be able to differentiate into any type of cell

A

because all the body’s cells develop from the one embryo

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24
Q

what is the problem with adult stem cells

A

only found in certain places like bone marrow

they only make certain types of cell

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25
Q

discuss meristems

A
  • in plants the only cells that divide by mitosis are found in plant tissues called meristems
  • meristem tissue is found in the areas of a plant that are growing e.g the tips of roots and shoots
  • meristems produce unspecialised cells that are able to divide and from any cell type in the plant (they act like embryonic stem cells)
  • unlike human stem cells these cells can divide and differentiate to generate any type of cell for as long as the plant lives
  • these unspecialised cells go on to form specialised tissues like xylem and phloem
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26
Q

how can stem cells be used in medicine

A
  • doctors use adult stem cells to cure some diseases like sickle cell anaemia can sometimes be cured with a bone marrow transplant (contain adult stem cells which produce new blood cells)
  • 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
  • It might be possible to use stem cells to create specialised cells to replace those which have been damaged by disease and injury
    e. g new cardiac muscle cells could be transplanted into someone with heart disease
27
Q

why is there a large scientific interest in stem cells

A

the potential for new cures

28
Q

what potential risk are associated with the use of stem cells

A

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

disease transmission - viruses live inside cells and if donor cells are infected with a virus and this isn’t picked up the virus could be passed onto the recipient and make them sicker

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. The patient can take drugs to supress this response but this makes them susceptible to disease.

29
Q

what is the problem with using embryonic stem cells

A

it raises ethical issues because some people argue that they shouldn’t be used because they are a potential human life

30
Q

what is the CNS

A

brain and spinal cord

31
Q

discuss the spine

A

the spinal cord is a long column of neurones (nerve cells) that run from the base of the brain down the spine
at several places down the cord, neurones branch off and connect with other parts of the body
the spinal cord relays information between the brain and the rest of the body

32
Q

what is the brain made up of

A

billions of interconnected neurones

33
Q

what is the function of the cerebrum (cerebral cortex)

A
  • memory, language, behaviour, senses and consciousness
  • largest part of the brain
  • conscious activity
  • divided into two cerebral hemispheres and each side controls the other
34
Q

what is the function of the cerebellum

A
  • fine muscle control, balance and posture
35
Q

what is the function of the medulla oblongata

A
  • breathing, heart rate, reflexes

- unconscious activities

36
Q

how can the brain be investigated without surgery

A

using PET scanners and CT scanners

37
Q

discuss how CT scanners work

A
  • A CT scanner uses X-rays to produce an image of the brain
  • A CT scan shows the main structures in the brain but it doesn’t show the functions of them
  • However if the CT scan 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
  • for example if an area of the brain is damaged and the patient can’t see then that area is involved in vision
38
Q

discuss PET scanning

A
  • PET scanners use radioactive chemicals to show which parts of the brain are active when the person is inside the scanner
  • PET scanners are very detailed and can be used to investigate both the structure and the function of the brain in real time
  • PET scans can show if areas in the brain are usually inactive or active so they are useful for studying disorders that change the brain’s activity
  • for example in Alzheimer’s disease activity in certain areas of the brain is reduced - PET scans can show this reduction when compared to a normal brain
39
Q

why can treating problems in the CNS be tricky

A
  • injuries to the brain, spinal cord, tumours or disease can be tricky to treat because:
  • it’s hard to repair damage to the nervous system. Neurones in the CNS don’t readily repair themselves and as of yet scientists haven’t developed a way to repair nervous tissue in the CNS
  • If a problem occurs in a part of the nervous system that’s not easy to access it can be hard to treat e.g its not possible to surgically remove tumours growing in certain parts of the brain
  • Treatment for problems in the nervous system may lead to permanent damage. For example a person who has injured their spinal cord may need surgery on their spine near to the injury and there is a risk that the spinal cord could be damaged further during the operation leading to permanent damage
40
Q

what do receptors do

A

detect a change in the environment

41
Q

discuss the nervous system reflex arc

A

when a stimulus is detected by receptors, the information is converted to a nervous (electrical) impulse and sent along a sensory neurone to the brain and spinal cord (CNS)
The CNS coordinates a response and impulses travel through the CNS along relay neurones.
the CNS sends information to an effector along a motor neurone then the effector responds accordingly e.g a muscle may contract or a gland may secrete a hormone

42
Q

what is your reaction time

A

how long it takes you to respond to a stimuli

43
Q

discuss the general adaptations and structure of any neurone

A
  • a cell body with a nucleus and other subcellular structures
  • the cell body has extensions that connect to other neurones
  • dendrites and dendrons carry nerve impulses towards the cell body and axons carry nerve impulses away from the cell body
  • some axons are surrounded by a myelin sheath which acts as an electrical insulator to speed up neurotransmission
  • neurones can be very long which also speeds up the impulse (connecting with another neurone slows the impulse down so it is quicker to have one long one then lots of short ones joined together)
44
Q

describe 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
45
Q

describe motor neurones

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
46
Q

describe relay neurones

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
47
Q

discuss synapses

A
  • the connection between two neurones is called a synapse
  • the nerve signal is transferred by chemicals called neurotransmitters which diffuse across the gap
  • the neurotransmitters then set off a new electrical signal in the next neurone
  • the transmission of a nervous impulse is very fast but is slowed down a bit at the synapse because the diffusion of neurotransmitters across the gap takes time
48
Q

what are reflexes

A
  • automatic rapid response to stimuli
  • they can reduce the chances of being injured
  • the passage of information in a reflex (from receptor to effector) is called a reflex arc
  • the neurones in reflex arcs go through the spinal cord or through an unconscious part of the brain
49
Q

discuss the reflex arc to prevent injury

A

when a stimulus is detected like a bee sting by receptor, impulses are sent along a sensory neurone to a relay neurone in the CNS
When the impulse reaches a synapse they trigger neurotransmitters to be released and these cause impulses to be sent along the relay neurone
When the impulse reaches a synapse between the relay and motor neurone the same thing happens
the impulses then travel along the motor neurone to the effector (in this example its a muscle but it could be a gland)
the muscle then contracts and moves your hand away from the bee
- because you don’t have to spend time thinking about the response its quicker than normal responses

50
Q

how does a reflex arc help to protect the eye

A
  • very bright light can damage the eye so the reflex protects it
  • light receptors in the eye detect very bright light and send a message along a sensory neurone to the brain
  • 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
51
Q

what is the function of the cornea

A

refracts light into the eye

52
Q

what does the iris do

A

controls how much light enter the pupil

53
Q

what is the function of the lens

A

to refract light into the eye and focus it on the retina

54
Q

what is the function of the retina

A

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

55
Q

what do rods do

A

detect light in dim light but cant see colour

56
Q

what do cones do

A

detect colour but can’t see in dim light

57
Q

what does the optic nerve do

A

information from light is converted to electrical impulses and the optic nerve carries these impulses from receptors to the brain

58
Q

how does light get focused onto the retina

A

the lens is elastic so can change shape to focus light onto the retina

59
Q

what does the eye do to look at distant objects

A
  • the ciliary muscles relaxes which allows the suspensory ligaments to pull tight
  • this pulls the lens into a less rounded shape so light is refracted less
60
Q

what does the eye do to look at close objects

A
  • the ciliary muscles contracts which allows the suspensory ligaments to relax
  • the lens becomes more rounded and so light is refracted more
61
Q

discuss long sighted people

A
  • unable to focus on near objects
  • this occurs when the lens is the wrong shape and doesn’t bend the light enough
  • the eyeball is too short
  • light from near objects is brought into focus behind the retina
  • you can use glasses with a convex lens to fix it
62
Q

discuss short sighted people

A
  • unable to focus on distant objects
  • the lens is the wrong shape and bends the light to much
  • the eyeball is too long
  • light from distant objects brought into focus in front of the retina
  • you can use glasses with a concave lens to correct it
63
Q

discuss colour-blindness

A
  • most common is red-green
  • caused when red or green cones in the retina are not working properly
  • there’s no cure because the cone cells can’t be replaced
64
Q

discuss catarcats

A
  • a cloudy patch on the lens which stops light from being able to enter the eye normally
  • people with cataracts likely to have blurred vision
  • experience colours looking less vivid and have difficultly seeing in bright light
  • a cataract can be treated by replacing the faulty lens with an artificial one

Biology Topic by Topic (5 decks)

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