A-level paper 2 mistakes Flashcards
What bond is formed when two amino acids combine in a condensation reaction?
How does it form?
peptide CONH
COOH group loses its OH and this combines with one of the H atoms from NH2 to form a water molecule.
Describe the structure of collagen.
three polypeptide chains
Helicies joined together
Held together by hydrogen bonds
Describe the events that lead to the release of acetylcholine at a synapse.
An action potential arrives at a pre-synaptic knob.
Calcium channels open so calcium ions diffuse into pre-synaptic neurone.
Vesicles move to membrane.
Vesicles fuse with the pre-synaptic membrane and release acetylcholine.
Explain the differences in the efficiency of energy transfer between trophic levels in a food chain.
Lots of energy is not passed onto primary consumers from producers as they have inedible parts.
Primary producers have a higher respiration rate than producers
More energy is lost from movement by primary consumers
Primary consumers lose more energy as excretion than producers.
Explain how auxins and cytokinins control the growth of lateral buds.
Auxin is released from the terminal bud.
It diffuses down the stem to inhibit lateral bud growth.
Cytokinin stimulates lateral bud growth.
Is produced from the base of the shoot
auxins can act in the same way as oestrogen does in human cells.
Explain how auxins affect the synthesis of enzymes.
Auxin binds with receptor in cytoplasm.
Transcription factor becomes activated.
Transcription factor binds to DNA.
Causes the production of mRNA
Explain one function of lysosomes.
digest pathogens because they contain enzymes.
Which region of the brain controls heart rate?
Medulla oblongata.
Explain the role of rhodopsin in the generation of a nerve impulse in the bipolar neurone when light falls on retina.
rhodopsin breaks down into opsin and trans retinal.
This causes sodium ion channels to become blocked.
Leading to hyper polarisation in rod cell.
So less inhibitory transmitter is released.
Does the filtrate in the loop of hence contain any glucose?
NO
Explain how tissue fluid is returned to the capillaries.
More protein in plasma than tissue fluid.
Plasma proteins are too large to pass out of capillary.
Oncotic pressure generated by plasma proteins.
Fluid moves in as oncotic pressure is greater than hydrostatic pressure.
Myoglobin is a protein made from one subunit.
Explain how the dissociation curve shows myoglobin is different to haemoglobin.
Myoglobin does not have an S shaped curve.
The affinity for oxygen does not alter.
Myoglobin has no cooperative binding.
Myoglobin binds to one oxygen molecule.
Why is the index of diversity a better measure of biodiversity than counting the number of different species.
Index of diversity considers the abundance of each species.
Describe the limitations of CITES in the conservation of organisms such as elephants.
Can be expensive to monitor.
Many species migrate, have very large ranges.
Furosemides reduce the active transport of sodium ions by the loop of Henle.
Explain how furosemides cause an increase in urine production.
Sodium ions are not removed from the ascending limb of loop of Henle.
So water potential of medullary fluid is higher.
Therefore less water removed from descending limb of loop of Henle.
And less water removed from DCT and collecting duct.
A higher volume of dilute urine is produced.
Is the genetic code in eukaryotes:
a) overlapping?
b) Degenerate?
c) contains introns?
a) no
b) yes
c) yes
If a genetic code is degenerate, what does that mean?
Multiple codons can code for the same amino acid.
Describe how exercise leads to the stimulation of the cardiac centre in the medulla oblongata.
Increased respiration increases carbon dioxide concentration in the blood.
This decreases the pH of the blood.
Detected by chemoreceptors which are found in carotid arteries.
Baroreceptors detect changes in blood pressure.
Impulses are sent to cardiac centre.
Explain how the structure of the cell membrane controls the transport of polar molecules.
Polar molecules are hydrophliic.
Phosphate head is hydrophilic.
Phosphate head is on outer side.
Polar molecules can pass through carrier proteins.
State what is meant by biodiversity.
All of the different alleles in a gene pool.
What is meant by NPP?
Gross primary productivity - respiration
How does NPP increase and decrease?
Increases because photosynthesis is greater than respiration.
Decreases because respiration is greater than photosynthesis.
