explain what is meant by a reflex action
an involuntary response to a stimulus
explain the type of receptor involved in pulling the hand away from a hot surface
describe the pathway taken by the nerve impulse from receptor to effector
sensory neurone to intermediate to motor
why is blood leaving the heart through the aorta at a higher pressure than blood leaving the pulmonary artery?
thicker muscle means stronger contraction of left ventricle
which nerve would scientists stimulate to cause a fall in cardiac output?
why does stimulation of the parasympathetic cause a fall in cardiac output?
sinoatrial node sends fewer impulses, so the heart beats less often ( CO = HR x stroke volume)
what event in the heart causes a pulse?
why is counting 20 seconds and multiplying by 3 less accurate than counting for 60 seconds?
any error is multiplied by 3
what causes vision in the fovea?
the prescence of cones to detect colour, each receptor connects to a different neurone
group b had the root tip removed and continued to grow horizontally - what conclusion can we draw from this?
IAA is produced in the root tip
group c had the upper half of the root tip removed, and grew downwards but less steeply - what conclusion can we draw from this?
less IAA is produced so there is less inhibition of growth in the lower side
explain the effect of temperature on the rate at which NAA is taken up by the lower surface of the leaf
increasing the temperature increases the kinetic energy, increasing the rate of diffusion
there are differences in the properties of the cuticle on the upper and lower surfaces of the leaves. Suggest how these differances might explain the difference in uptake rate.
upper layer has thicker cuticle - slowing rate of diffusion
explain why it takes time for the rod cells to recover their sensitivity to light after moving into darkness?
the rhodopsin has been bleached by the light, time is required for resynthesis of rhodopsin
one reason that the reaction time is slower when body temperature falls is because nerve impulse conduction is slower. Explain how a lower temperature leads to a slower nerve impulse conduction
slows rate of diffusion of K+ amd Na+
other than temperature, give 2 factors that affect the rate of nerve impulse conduction
myelination, diameter of axon
why is the genetic code described as being universal? (1)
in all organisms, the same triplet codes for the same amino acid
The genetic code uses four different bases, what is the maximum number of different DNA triplets that can be made using these four bases?
What is epigenetic inheritance? (2)
Changes to inherited gene function without altering the DNA base sequence, caused by an environmental factor.
BMI = mass in kg/ (height in metres)*2 calculate the BMI of a boy weighing 70kg and 170cm tall
what is a tumour?
a collection of cells growing out of control
what is cancer?
when cells from a tumour have spread/ metastasis has happened
what is the genome of an organism?
all genes present in a haploid set of chromosomes
Explain how methylation of a tumour suppressor gene can lead to cancer (3)
the methyl group attaches to a cytosine base and stops transcription protein that prevents cell division not produced no control of mitosis ----> cancer
Deletion changes the nature of the protein (in diagram) but substitution does not. Suggest why (3)
deletion causes frame shift code is degenerate so amino acid not altered
Give 2 factors (other than cost) that should be considered when selecting an antibiotic to treat a bacterial disease (2)
side affects, interaction with other drugs, allergies, conditions
A mutation in a tumour suppressor gene can result in the formation of a tumour. explain how (2)
tumour suppressor gene inactivated increasing rate of cell division
some cancer cells have a receptor protein in their cell surface membrane that binds to a hormone called a growth factor, This stimulates cancer cells to divide. this can be prevented using monoclonal antibodies, suggest how (3)
Antibody has a specific tertiary structure complementary to the receptor protein preventing the growth factor from binding
If the DNA of the cell is damaged, a protein called p53 stops the cell cycle. Mutation in the gene for p53 could cause cancer to develop. Explain how (3)
p53 is non functional or not coded for the cell cycle continues in the damaged cell (no apoptosis) resulting in uncontrolled cell division
Name 2 enzymes involved in semi conservative DNA replication (2)
DNA polymerase DNA helicase