Past Paper Question Errors Flashcards
(21 cards)
When setting up a simple respometer to investigate rate of respiration of yeast
Suggest one reason why it is important that the student left the apparatus for an hour after yeast culture reaches a constant temperature
(1 mark)
To allow oxygen to be respired
Explain why a log scale might be used to record the number of cells
(1 mark)
Large range/ difference/ increase in number
If a graph decreases then plateaus at 1000 years
Use the evidence from this graph, what can you conclude about the net primary productivity in sand dunes older than 1000 years
(2 marks)
1) NPP remains constant
2) GPP/ photosynthesis and respiration remain constant
OR
3) NPP low/decreases
4) less light so less photosynthesis/GPP
Furosemide inhibits the absorption of sodium and chloride ions from the filtrate produced in the nephrons
Explain how flurosemide causes an increase in volume of urine produced
(3 marks)
1) water potential of filtrate/ tubule decreases
2) less water (reabsorbed) by osmosis ( from filtrate/tubule)
3) collecting duct (is where osmosis occurs)
Suggest two features of the structure of different proteins that enable them to be separate by gel electrophoresis
(2 marks)
1) mass/ number of amino acids/ polypeptides
2) charge
3) R groups differ
Lactase persistence (LP) is caused by mutation in DNA. This mutation does not occur in the gene coding for lactase
Suggest and explain how this mutation causes LP
(2 marks)
1) mutation in promoter for transcription factors or promoter regions for the gene
2) lactase gene continues to be transcribed
Achromatopsia is a form of colour blindness when only rod cells and no functional cone cells in the eye. People with complete achromatopsia have difficulty in seeing detail
Explain why
(3 marks)
1) no functional cones/ only rod cells
2) cones are connected to a single neurone/ several rods connected to a single neurone
3) cones separate impulses to brain/ rods single impulse to brain
Red-green colourblindness= sex-linked recessive allele. They have green sensitive cones but the photoreceptive pigment they contain does not function
People with red- green colour blindness are unable to distinguish between red and green and also between other colours. Explain why
(3 marks)
1) green sensitive pigments/ cones are non-functional
2) three different types of pigment/cones
3) different colours due to stimulation of more than one pigment/cones
The scientists observed the chloroplast from sample of leaves using electron microscope. Suggest why iron deficient plants have a reduced growth rate if a thinner thylakoid membrane was observed
(3 marks)
With less thylakoid membrane
1) smaller surface area/ less chlorophyll
2) so reduced light absorption
3) slower rates of photosynthesis
If drug trial test have been done on mice
Suggest and explain two further investigations that should be done before this ADC is tested on human breast cancer patients
(2 marks)
- test on other mammals to check for side effects
- test on healthy humans to check side effects
- see if repeat doses stop tumours regrowing
Succession occurs in natural ecosystems. Describe and explain how succession occurs
( 4 marks)
1) pioneer species developed
2) changes the environmental factors to become less hostile so other species can develop
3) other species better adapted so out complete pioneer species
4) increase in biodiversity
5) until climax community reached
Explain how a single base substitution causes a change in the structure of this polpeptide.
Do Not include details of transcription and translation in your answer.
(3 mark)
1) change in sequence of amino acid/primary structure
2) change in hydrogen/ionic/disulfate bonds
3) Alters tertiary structures
Explain why the lids were kept on the Petri dishes when growing sample of shoot
(2 marks:
1) prevent/ reduce evaporation
2) which alters concentration of IAA solution
Another group of scientists suggested that a decrease in the force of muscle concentration is caused by an increase in concentration of inorganic phosphate, in muscle tissue.
Their hypothesis is that an increase in the conc of Pi prevents the release of Ca ions in muscle tissue.
Explain how a decrease in the conc of Ca2+ in muscle tissue could decrease the force of muscle contraction
(3 marks)
1) shape of tropomyosin not changed so binding site not exposed
2) fewer cross bridges formed
3) myosin head doesn’t move/ myosin does not pull actin
In muscles, Pyruvate is converted to lactate during prolonged exercise.
Explain why converting Pyruvate to lactate allows the continued production of ATP by anaerobic respiration
( 2 marks)
Pyruvate oxides by reduced NAD producing NAD+
So glycolysis can continue
Explain how inhibiting adenylate cyclase may help to lower the blood glucose concentration
(3 marks)
1) less/no ATP is converted to cyclic AMP/ cAMP
2) less/no kinase is activated
3) less/no glycogen is converted to glucose (glycogenolysis)
Describe what happens during photoionisation in the light dependent reaction
1) chrolophyll absorbs light energy
2) causing electrons to be lost
Describe the methods the student used to separate the pigments after the solution of pigments has been applied to the origin
(2 marks)
1) water added just below the origin line
2) remove the paper before solvent reaches the top
3) draw pencil line where solvent reached and allow to dry
Describe how the DNA is broken down into smaller fragments
( 2 marks)
1) restriction enzymes/endonuclease
2) cuts DNA at specific base sequences
Suggest and explain how digesting insects helps the sundew to grow in soil with very low concentrations of some nutrients
(2 marks)
1) break down proteins
2) provides amino acids
OR
3) digestion of DNA
4) provides nucleotides for growth
Explain how damage to the myelin sheath of neurones can cause muscular paralysis
( 3 marks)
1) saltatory conduction or impulses pass to other neurones
2) nerve impulse slowed
3) refer to neuromuscular junctions then not receiving impulse
