Luteinising hormone (LH) ...
stimulates the unfertilised ovum to develop into the corpus luteum
matures the eggs
causes a follicle to leave the ovary
causes egg to move down fallopian tube
works with FSH to release the follicle from its casing, allowing it to bond with the uterus lining
stimulates evolution
When LH breaks down it forms a corpis luteum
Testosterone feedback loop
This feedback loop ensures that less testosterone is produced by the kidneys
Inhibition of these hormones causes chemical reactions to be slower and fewer
Therefore there is less activity in the testes
This causes the hypothalamus to reduce the stimulus to the pituitary gland which stops release of testosterone
The body then turns off the organelle that produces testosterone
This results in a decrease in secretion of LH and FSH to the testes
This will cause the hypothalamus to stop releasing testosterone
Therefore the testes are inhibited
If the concentration of testosterone rises too high it will be inhibited by the pituitary gland
If testosterone is not used to make sperm cells it enters the blood stream
LH and FSH stimulate the testes to produce either sperm cells or testosterone
Too much testosterone causes inhibition which is a message directed towards the pituitary gland
FSH is reduced so follicles are not stimulated
Possible male contraceptive pill
It inhibits the release of FSH and LH into the testes
How a mutated tumour suppressor gene can result in a tumour
There is now a mutated gene with tumour-coding bases
The tumour suppressor gene will divide uncontrollably
Explain why not all mutations result in a change to the amino acid sequence of the encoded polypeptide
The last allele of a triplet does not affect the coding of an amino acid
Amino acids are degenerate
Amino acids can be coded for by multiple codons
This is due to the degenerate codon
The amino acid sequence could still code for the same gene
Different amino acids can still code for the same polypeptide
How DNA methylation can prevent gene expression
The gene is not a functional protein and is not expressed
How a Pacinian corpuscle produces a generator potential when stimulated
A pacinian corpuscle has a general negative on the outside ... when pressure is applied it pushes the negative ions inside
When the impulse hits it it will bounce off and rapidly travel
Reason why damage to myelin sheath can lead to muscle contraction problems
Myelin sheaths are electrical conductors
This could cause the action potential to travel along the entire length of the neurone instead of along the nodes of Ranvier
Shorter distance for impulses to jump means slower impulse
Myelin sheath can't act as an impulse and cannot limit impulses
Why do cannabinoids (hydrophobic molecules) easily pass into neurones?
Because there is no water in neurones
How cannabinoids could prevent muscle contraction
Synaptic vesicles cannot bind to acetylcholine
Vesicles are taken into the synaptic cleft
The vacuoles may not fuse with pre-synaptic membrane
Vesicles containing neurotransmitter will not be able to bind to receptors on the post-synaptic membrane
Similarity between a taxis and a tropism:
Both are responses to a positive or negative stimulus
They both involve a directional change in the behaviour of an organism
If the stimulus is favourable both responses will cause the organism to get closer to the stimulus
An example is in animals like worms which would move towards light to get above ground
Both require a stimulus such as environment
Difference between a taxis and a tropism:
effect is immediate with taxis whereas tropism takes a longer time
taxis is full, tropism is partial movement
Why scientists used the same restriction endonuclease enzymes on each DNA sample
So they allow themselves to cut DNA at equal lengths
So the same bases are cut
Why scientists used cells that were in mitosis:
When DNA is dividing you can clearly see the alleles as you can see chromosomes
Other cells have loose DNA that is not arranged in chromosomes
As they contain two copies of the alleles which may be seen on the microscope
These cells would be stretched out into 'chromosome shapes' rather than the DNA being all mixed together
The DNA probe is radioactively marked, and this makes it more visible under the microscope
Chromosomes become visible under the microscope, which would allow the scientists to attach a DNA probe
Scientific inaccuracy
A homologous pair is when a chromosome has the same gene but different alleles
Respiration rats also increase in animals
Plants have negative phototropism and positive geotropism in their roots
This impulse tells the brain that the external temperature is too high and pushes the body to make changes to itself in order to oppose the change
This increased heart rate allows more oxygen to be carried around the body than carbon dioxide
We control our glucose concentration in the blood by the use of certain humans
A reflex arc uses a sensory neurone, intermediate neurone and motor neurone to move something like an arm away from something like fire
The reflex arch is the simplest response tool
Plant roots stretch towards the soil in the direction of gravy
The body needs to be in homeostasis in order for it to work properly.
When insulin binds to receptors glucose is broken down to glycogen
The plant moves towards the sun by the axons in the stem of the plants.
This causes the heart to beat faster so that CO2 can dissolve out of the blood more rapidly
In the cold the blood will leave the arms and legs
Increasing heart rate flushes out the high pH
Genes respond to their environment by producing proteins
Responses to cold weather: hairs moving up on skin
When an organism moves away from or towards a stimulus it is called a tactical response (taxis)
Tropism is when plants grow directional to compete for light and nutrients
Body fluid (lymph) is forced out under hydrostatic pressure and reabsorbed into the lympathetic system
The process of taxis is where an organism has a directional response to a positive or negative stimuli
Taxis are responses to stimuli in the environment
Arterioles widen to press the blood against the capillaries
Animals will migrate north to follow the plants
Plants can for example open and close their leaves
If a male/female touches a hot pan, a reflex arc is involved
During photosynthesis, when light is available, the photoreceptors in the chlorophyll in the leaf is stimulated
This (vasodilation) allows blood to be presented to the skin's surface for evaporation.
Humans reproduce by meiosis and is very important as the genetics from the parents is different to the child.
The child is not a clone. The child gets random genetics from both parents.
The variation in reproduction means we have a large genetic diversity and therefore we are less likely to all be susceptible to the same disease.
Home