Topic 2 - Cells And Control Flashcards
cell cycle
a series of events that takes place in a cell as it grows and divides
diploid cell
contains two copies of each chromosome
haploid cell
contains only one copy of each type of chromosome
what happens in interphase (first phase)
first the cell makes extra sub-cellular cell parts (e.g. mitochondria) and then it makes copies of all the chromosomes (DNA replication)
what is mitosis and what does it produce
the cell splits to form two new genetically identical diploid daughter cells
what is asexual reproduction and what does it produce
only needs one parent to reproduce, produces offspring that are genetically identical diploid meaning the cells have the same chromosomes as the parent
how are tumours produced
due to rapid cell division it produces growing lumps of cancerous cells
what are the stages of mitosis
I interphase
Then:
P prophase
M metaphase
A anaphase
T telophase
C cytokinesis
what happens in the prophase
The chromosomes condense, getting shorter and fatter. The membrane around the nucleus breaks down and the chromosomes lie in the cytoplasm.
what happens in the metaphase
the chromosomes lineup at the centre of the cell
what happens in the anaphase
spindle fibres pull the chromosomes apart; then the chromosome copies are pulled to either end of the cell
what happens in the telophase
Membrane form around each of the set of chromosomes. These become the nuclear of the two new cells - the nucleus has divided
percentile chart
a chart used to monitor growth and can be compared to other at the same age
what do the numbers mean on a percentile growth chart e.g. if a baby’s mass is on the 75th percentile curve what does that mean?
it means 25% of baby’s are heavier and 75% of baby’s are lighter - a quarter above average
differentiation
the process where a cell develops new sub-cellular structures (become specialised) to perform a specific function
meriSTEM cell and where is it
found near the end of the shoot/root in a plant and is a type of plant tissue that is made up of a group of stem cells that allow plants to continue growing
growth
an increase in size as result of an increase in number of cells
how to work out a percentage change for growth
final value - start value x100
starting value
stem cell
a cell that hasn’t differentiated yet; they are unspecialised, and can go onto become a number of different types of cells
adult stem cells
cells found living within specific differentiated tissues in our bodies that can differentiate into a few types of cells and they can renew themselves or generate new cells that can replenish dead or damaged tissue
embryonic stem cells
stem cells that are found in embryos and can differentiate into almost every type of cell in the body
risks of stem cells used in medicine
- tumour development - stem cells continue to divide inside the body after they have replaced damaged cells and start to create a lump
- rejection - stem cells from one person are often killed by the immune system or other people that they are put into
function of neurones
nerve cells that send messages all over your body to process information and control the body
tell me about the cerebral cortex (cerebrum)
- makes up 80% of the brain
- used for most of our senses, language, memory, behaviour and consciousness
- split into left and right hemisphere
—> each hemisphere has different functions and communicates with the opposite side of the body
function of cerebellum
base of the brain and responsible for muscle coordination and balance and posture
function of medulla oblongata
controls unconscious activities - your heart rate and your breathing and is also responsible for reflexes such as vomiting, sneezing and swallowing
what is a CT scan and what happens during it
CT scan shows the shapes of structures in the brain
- an x-ray beam moves in a circle around the head and detectors measure the absorption of the x-rays
what’s a PET scan and what happens during it
PET scan shows brain activity
- the patient is injected with radioactive glucose
- more active cells take more glucose than less active ones
- the radioactive atoms cause gamma rays which the scanner detects
more gamma rays come from parts containing more activecells
what happens when you have spinal cord damage
damage to the spinal cord reduces the flow of information between the brain and parts of the body
how can spinal cord damage be treated?
Wires can be used to electrically stimulate nerves and muscles below the damage however patients do not regain full movement or feeling
two ways to help treat brain tumours
radiotherapy - cells can be killed using high energy x-ray beams
chemotherapy - cells can be killed by injecting drugs that kill actively dividing cells
how can a tumour damage the brain?
brain tumour may squash parts of the brain stop them from working
Central Nervous System (CNS)
controls your body and is made up of the brain and spinal cord
stimulus
any change in the environment to which the body needs to respond
receptor cell
a cell that detects stimulus and converts it into an electrical impulse to be sent to the sensory neurone
a response
an action that occurs due to a stimulus
neurotransmission
travelling or transmission of impulses that happened in neurones (nerve cells)
pathway of a nerve impulse
stimulus (e.g smelling food) —> impulse starts at receptor (e.g. nose) —> impulse past along sensory neurone —> impulse travels to CNS —> impulse passed along relay neurone —> impulse passed along motor neurone —> effector (muscle) receives impulse to react —> response (e.g walk to shops)
what happens in a sensory neurone
- one long dendron carries nerve impulses from receptor cells to the cell body, which is located in the middle of the neurone
- one axon carries nerve impulses from the cell body to the CNS
what happens in a motor neurone
- many short dendrites curry nerve impulses from the CNS to the cell body
- one axon carries nerve impulses from the cell body to the effector cells
what happens in a relay neurone
- many dendrites carry nerve impulses from censoring neurons to the cell body
- an axon carries nerve impulses from the cell body to motor neurons
retina
the light-sensitive part and is covered in receptor cells called rods and cones which detect light
rods
receptor cells that detect differences in light intensity, but can’t sense colour
cones
receptor cells that are sensitive to the different colours of light
iris
controls how much light enters the pupil which can constrict the pupil (make it smaller) or dilate it (make it bigger)
pupil
the dark area in the middle of the eye and is where light enters
cornea
bends (refracts) light rays to bring them together to focus an image
lens
a glass with curved sides that refracts light to bright the rays together to focus an image
ciliary muscles
changes the shape of the lens when your eyes focus on a near object
what happens to your eye when you look at distant objects
- the ciliary muscle relaxes which allows the suspensory ligaments to pull tight
- this pull the lens into a less rounded shape so light is refracted less
what happens to your eye when you look at close object
- the ciliary muscle contracts which slackens the suspensory ligaments
- the lens becomes a more rounded shape, so light is refracted more
cataract
is a cloudy area in the lens of your eye
what is ‘short sighted’ vision and what causes this
when distant objects seem blurred and this is because rays of light are focused INFRONT of the retina due to either the eyeball being too long or the cornea curves too much
what is ‘long-sighted’ vision and what causes this
when close objects seem blurred and this is because rays of light are focused BEHIND the retina due to either the eyeball being too short or the cornea is not sufficiently curved
name eye problems:
- short sighted
- long sighted
- cataract
- colour blindness
colour blindness
people have cones that do not work properly and so have difficulty seeing some colours
effectors
muscles and glands that carry out an action
motor neurone
carry impulses to effectors
relay neurone
link the motor and sensory neurones
sensory neurone
carries information to the central nervous system
synapse
a connection between two neurones
The transmission of a nervous impulse is very fast, but it is slowed down a bit at the synapse because of diffusion of neurotransmitters across the gap takes time
what happens in a synapse
- the nerve signal is transferred by chemicals called neurotransmitters, which diffuse (move) across the gap
- the neurotransmitters then set off a new electrical signal in the next neurone
reflex
an action performed without conscious thought in response to a particular stimulas
reflex arc
a neurone pathway that controls a reflex action
what happens in the cytokinesis phase
the cytoplasm and cell membrane divide to form two separate cells
stages of plant growth
- cell division
- cell elongation
- cell differentiation
receptor cell
molecule that receives and responds to a neurotransmitter
what happens to the muscles in your eye when you look at close objects
they contract
what happens to the muscles in your eye when you look at far away objects
they relax
what’s the adaptation of a specialised human cell: red blood cell
it has no nucleus allowing more space for red haemoglobin molecules (which carry oxygen) it also has a large surface area (allowing oxygen to diffuse in an out more quickly)
what is the function of a specialised cell: nerve cells (neurones)
They have a long fibre that carries electrical impulses around the body and many connections to other neurones
The function of the specialised human cell: muscle cell
they contain special contractor proteins that can shorten the cell
myelin sheath
fatty layer surrounding dendron and axons
function of myelin sheath
Electrically insulates a neurone from neighbouring neurons, stopping the signal losing energy also makes an impulse jump along the cell between the gaps in the myelin and so speed up neurontransmission
how can shorten sightedness be corrected using glasses
using a diverging lens to spread out rays before they reach the eye
how can long sightedness be corrected using glasses?
by using a converging lens to bend rays before they reach the
which only terminal are neurotransmissions released from
axon
why is the reflex arc quicker than usual
because they are automatic and don’t bypass the parts of the brain that involve processing information and so are quicker than responses that need processing
why are synapses used
- they also allow many fresh impulses to be generated in many neurons connected to one neuron - the original impulse does not need to be split and lose strength
what part of the brain contains the occipital lobe?
cerebral hemisphere
how can a student prepare a microscope slide to show mitosis in the growing roots of a plant
- soften the root tip/meristem with heat
- crush the root tip onto the slide
- stain the root
- add a drop of water to the slide
- add a cover slip
how is a cataract formed and fixed
formed: build up of protein in the lens
fixed: surgery to replace lens
why some people are opposed to the isolation of human embryonic stem cells
have potential to develop into a baby
benefits of using a patients OWN stem cells to treat the patient
- can differentiate into any type of cell
- less likely to get reject from the body as it’s their own cells (match tissue type of the patient)
- replace damage cells
- no donor needed
How can temperature be controlled in an experiment with the activity of enzymes at different pH levels
use a water bath
