B2 - Cells and Control Flashcards
Define
chromosone.
a coiled up length of DNA molecules
What is a
diploid cell?
a cell which has two copies of each chromosone
What is
mitosis
used for? (2)
- growth in multicellular organisms
- replacing cells that have been damaged in multicellular organisms
Define
asexual reproduction.
the use of mitosis to reproduce
What are the
main stages of the cell cycle?
(6 stages)
International - Interphase
Propaganda - Prophase
Makes - Metaphase
Animals - Anaphase
Telecommunicate - Telophase
Cylently - Cytokinesis
What occurs during
interphase?
(2 things)
- 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
What are the
four stages of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
What occurs during
prophase?
(2 things)
- the chromosones condense, getting shorter and fatter
- the membrane around the nucleus breaks down and the chromosones lie free in the cytoplasm
What occurs during
metaphase?
(1 thing)
the chromosones line up at the centre of the cell
What occurs during
anaphase?
(2 things)
- spindle fibres pull the chromosones apart
- the chromatids are pulled to opposite ends of the cell
What occurs during
telophase?
(2 things)
- membranes form around each of the sets of chromosones
- cytokinesis occurs
these become the nuclei of the two new cells - the nucleus has divided
What occurs during
cytokinesis?
the cytoplasm and cell membrane divide to form two separate cells
(this is part of telophase)
What is produced at the end of
mitosis?
two genetically identical diploid daughter cells which are genetically identical to the parent cell
What equation allows you to calculate
number of cells after multiple divisions of a cell by mitosis?
number of cells = 2^number of divisions
N = 2^n
Define
growth.
an increase in size or mass
Define
cell differentiation.
the process by which a cell changes to become specialised for its job
What are the benefits of
specialised cells?
they allow multicellular organisms to work more efficiently
Define
cell elongation.
the expansion of a plant cell, making the cell bigger and so making the plant grow
How does
cancer occur?
(4 steps)
- The rate at which cells divide by mitosis is controlled by the chemical instructions (genes) in an organism’s 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.
When might a doctor choose to investigate a baby’s size?
(4)
- 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
Define
stem cell.
an undifferentiated cell
Where are
stem cells found in adults?
bone marrow
What are the differences between
adult stem cells and embryonic stem cells?
(and why?)
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)
Where are
meristems found in plants?
and why?
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)
What are the differences between
adult stem cells and meristems?
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
What are the
three main risks of stem cells in medicine?
- tumour development
- disease transmission
- rejection
Describe the risk that
tumour development
from stem cells poses.
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.
Describe the risk that
disease transmission
from stem cells poses.
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.
Describe the risk that
rejection
from stem cells poses.
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.
What are the
ethical issues surrounding embryonic stem cell research?
and what is the counter argument to this?
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.
What is the
spinal cord?
a long column of neurones (nerve cells) that run from the base of the brain down the spine.
What does the
spinal cord
do?
it relays information between the brain and the rest of the body
What are the
three main parts of the brain?
(that you need to know about)
- cerebrum
- cerebellum
- medulla oblongata
What are some key points about the
cerebrum?
(4 points)
- 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
What are some examples of things that the
cerebrum
is responsible for?
(5)
- movement
- intelligence
- memory
- language
- vision
What are some examples of things that the
cerebellum
is responsible for?
(2)
- muscle coordination
- balance
What are some examples of things that the
medulla oblongata
is responsible for?
(2)
- breathing
- heart rate
(unconscious activities)
How does a
CT scan
work?
it uses x-rays to produce an image of the brain
What does a
CT scan show?
(and what does it not show?)
it shows the main structures in the brain
it doesn’t show the functions of them
How does a
PET scan
work?
it uses radioactive chemicals to show which parts of the brain are active when the person is inside the scanner
What does a
PET scan
show?
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
What are the difficulties of
treating problems in the CNS?
(3)
- 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
What are
sensory receptors?
groups of cells that can detect a change in your environment
Define
stimulus.
a change in the environment
Define
reaction time.
the time it takes you to respond to a stimulus
Describe how the
CNS coordinates a response.
(to a stimulus) (5 steps)
- A stimulus is detected by receptors.
- This information is converted to a nervous (electrical) impulse and sent along sensory neurones to the CNS.
- The CNS coordinates the response (impulses travel through the CNS along relay neurones).
- The CNS send information to an effector (muscle or gland) along a motor neurone.
- The effector then responds accordingly.
What are some features of
all neurones?
(2)
- a cell body with a nucleus (plus cytoplasm and other subcellular structures)
- the cell body has extensions that connect to other neurones
What is the
structure of a sensory neurone?
(and each part’s purpose)
- 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
What is the
structure of a motor neurone?
(and each part’s purpose)
- 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
What is the purpose of a
myelin sheath?
it acts as an electrical insulator, speeding up the electrical impulse
What is the
structure of a relay neurone?
(and each part’s purpose)
- 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
Define
synapse.
the connection between two neurones
What occurs at a
synapse?
- The nerve impulse reaches the end of the neurone.
- 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 it is slowed down a bit at the synapse because the diffusion of neurotransmitters across the gap takes time.
Define
reflex.
and state why it is helpful.
an automatic, rapid response to stimuli
it can reduce the chances of being injured
Define
reflex arc.
the passage of information in a reflex
(from a receptor to effector)
How does a
reflex work?
(4 steps)
- A stimulus is detected by receptors.
- Impulses are sent along a sensory neurone to a relay neurone in the CNS.
- The impulses then travel along the motor neurone to the effector.
- The effector then causes the muscle or gland to respond.
How does a
reflex protect the eye from bright light?
(2 steps) and why?
- Light receptors in the eye detect a 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.
this is because very bright light can damage the eye
What is the purpose of the
cornea?
to refract light into the eye
What is the purpose of the
iris?
to control how much light enters the pupil
What is the purpose of the
lens?
refract light, focusing it onto the retins
What is the
retina?
the light sensitive part of the eye that is covered in receptor cells called rods and cones, which detect light
What are
rods?
receptor cells that are more sensitive in dim light but can’t sense colour
What are
cones?
receptor cells that are sensitive to different colours but are not so good in dim light
How does the information from the light get to the
brain?
The information from light is converted into electrical impulses. The optic nerve carries these impulses from the receptors to the brain.
How does the eye focus light onto the retina to look at
distant objects?
(2 steps)
- The ciliary muscle relaxes, which allows the suspensory ligaments to pull tight.
- This pulls the lens into a less rounded shape so light is refracted less.
How does the eye focus light onto the retina to look at
close objects?
(2 steps)
- The ciliary muscle contracts, which slackens the suspensory ligaments.
- The lens becomes a more rounded shape so light is refracted more.
What is
long-sightedness?
and why does this occur?
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.
What type of lens fixes
long-sightedness?
a convex lens
What is
short-sightedness?
and why does this occur?
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.
What type of lens fixes
short-sightedness?
a concave lens
What is
colour blindness?
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.
What is a
cataract?
a cloudy patch on the lens, which stops light from being able to enter the eye normally
What are the consequences of a
cataract?
and how can this be treated?
the person might experience colours looking less vivid and have difficulty seeing in bright light
replacing the faulty lens with an artificial one
