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Wrong Past paper questions > Biology > Flashcards

Biology Flashcards

1
Q

Explain why the human heart is divided into a left side and a right side.

A
  • deoxygenated and oxygenated blood needs to be separate
  • this allows the conc gradient to remain steep
  • there needs to be different pressures on either side of the heart.
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2
Q

Explain why a gene mutation affects gas exchange in a person with cystic fibrosis.
(4)

A
  • gene mutation affects CFTR protein, which is defective
  • therefore Cl- ions cannot move out of the cell.
  • therefore water moves out of the mucus and into the cells, creating thick mucus
  • this reduces rate of gas exchange
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3
Q
  • what 2 monosaccharides combine to make sucrose?
A
  • alpha glucose
  • fructose
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4
Q

Another line could be drawn on this graph to show the pressure changes in the right ventricle compared to the left ventricle
Describe the shape and position of this line.
Give reasons for your answer.

A
  • line will be similar
  • as both ventricles contract simultaneously
  • peaks will be lower as right side of the heart needs lower pressure - as it only pumps to the lungs and back
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5
Q

Describe the structure of a nucleotide pair.

A
  • contains a deoxyribose sugar
  • bases are joined by hydrogen bonds
  • and bases are complimentary to each other, eg G and C
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6
Q

In human cells, S phase lasts about 10 hours.
Suggest why each DNA molecule is replicated using many replication bubbles.

A
  • to speed up the process
  • so that the S phase is shorter
  • so that cell division is also faster.
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7
Q

Population carrier screening (PCS) is one type of genetic screening.
This involves screening people who want a child to see if they are carriers of
genetic disorders.
In one country, the number of babies born with cystic fibrosis went down
following the introduction of PCS.
Suggest why the number of babies born with cystic fibrosis went down.

A
  • can allow for carriers to be identified
  • therefore couples can make better informed decisions about having children - eg not having children or adoption
  • thus a lower amount of homozygous babies will be born.
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8
Q

Describe the structure of collagen.

A
  • fibrous protein
  • made of 3 polypeptide chains in a helix structure
  • Hydrogen bonding between layers
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9
Q

Osmosis can be defined as the movement of free water molecules through a
partially permeable membrane, down a water potential gradient.
Explain this definition.

(3)

A
  • movement of free water molecules because some water molecules are restricted from moving
  • partially permeable membrane because it allows only some substances to pass
  • down a water potential gradient because water molecules will be moving from an area of low solute conc to high solute conc
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10
Q

Explain why a person might have to take several types of drugs to reduce the risk of CVD.

A
  • because several factors cause CVD
  • and different drugs treat different conditions
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11
Q

Some studies do not assess the nutritional quality of the diet of the participants. Explain why the results of these studies have to be treated with caution.

(3)

A
  • because the studies will be invalid
  • because diet is a factor, among many that can affect CVD
  • eg High salt diet may increase blood pressure
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12
Q

The amino acid Glu is hydrophilic (polar) and the amino acid Val is hydrophobic (non‐polar).
Suggest why this mutation causes haemoglobin molecules to stick together.

A
  • the R groups may interact differently in terms of bonding
  • as Glu could interact with other hydrophilic groups or water
  • and Val could interact with other hydrophobic groups
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13
Q

Sickle cell disease can result in death.
Explain why the changes in the structure of haemoglobin and the shape of
the red blood cells could result in death in a person with sickle cell disease.
(3)

A
  • change in structure of hemoglobin means that it will have less bonding affinity to oxygen
  • change in shape of RBCs means that less oxygen will diffuse in because of the lower SA
  • means that less oxygen available to cells for aerobic respiration
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14
Q

Explain why this speed needs to be slower than the speeds that the impulse
travels between other parts of the heart.

(2)

A
  • so that the atria can finish emptying
  • and so the AV valves can close.
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15
Q

Explain how taking this anticoagulant can reduce the risk of
cardiovascular disease (CVD).

A
  • reduces risk of blood clots
  • therefore coronary arteries can’t be blocked
  • thus reduces risk of MIs, and the heart muscle cells will continue to respire
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16
Q

A second study compared this result with people given a combination of
warfarin and aspirin.
Describe how this study should be carried out to produce a valid comparison.
(4)

A
  • select group who have previously had a heart attack
  • choose people who have similar lifestyle as those in warfarin group
  • give the same dosage of warfarin to this group
  • measure result for the same amount of time
  • making sure its double blind study.
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17
Q

Compare and contrast the structure of glucose with the structure of glycogen.
(3)

A
  • both made of alpha glucose
  • glucose is monosaccharide whereas glycogen is polysaccharide
  • glycogen has 1,4 glycosidic bonds whereas glucose does not.
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18
Q

Explain the role of these bases in the structure of DNA.

A
  • bases hold the polynucleotide strands together
  • Because of a smaller base being complimentary to a bigger base (eg A to T and G to C)
  • so this determines the number of H bonds that can form between them to form parallel strands.
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19
Q

Thromboplastin is stored inside platelets.
Explain the advantages of storing thromboplastin inside platelets.
(3)

A
  • to keep prothrombin separate.
  • this prevents prothrombin from being converted to thrombin
  • thus this prevents the blood clotting process taking place when it is not necessary
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20
Q

Explain why the velocity of blood flow in the large arteries is slower than the
velocity of blood flow in the aorta.
(3)

A
  • Aorta is under higher pressure
  • aorta branches out into more blood vessels - so velocity is faster in aorta
  • friction between endothelial lining and blood may slow velocity in large arteries.
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21
Q

Explain why the total surface area of the capillaries needs to be so high. (2)

A
  • to increase rate of diffusion
  • by decreasing diffusion distance at more points of contact.
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22
Q

Describe the secondary structure of a polypeptide.

(2)

A
  • alpha helixes/beta sheets
  • with H bonds in between.
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23
Q

The effect of two different temperatures on the lengths of the primary structure
and secondary structure of a polypeptide was investigated.
The table shows the results of this investigation.

Structure of
polypeptide

Length of structure/nm
at 25° 55°C
primary 505 505
secondary 48 70

explain the results of this investigation.

A
  • initially primary structure is same for both temp
  • because peptide bonds are unaffected by temperature
  • secondary structure is shorter than primary because it is folded.
  • but longer for higher temperature due to hydrogen bonds breaking.
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24
Q

(iii) Explain why it is important that a person’s perception of a risk is close to the actual risk.
(3)

A
  • if they are familiar with the risk, lifestyle mods can be made
  • they can get blood tests to determine risk and any precautions - eg starting medications.
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25
Q

Compare and contrast the structure of an mRNA molecule with that of a
tRNA molecule.

A
  • both have a ribose sugar
  • both have RNA bases, including U
  • However t-RNA has anticodons whereas mRNA has the codon
  • m-RNA is linear and t-RNA is folded shape.
26
Q

Describe stages of the cardiac cycle and what valves are open during what stage.

A
  • Atrial systole - AV valves open, SV valves closed
  • Ventricular systole, AV valves closed SV open
  • Cardiac diastole - AV valves open and SV valves closed.
27
Q

A hydra is an organism with tentacles that has a hollow body that is made up of two layers of cells.
Explain how a hydra is adapted for gas exchange.

A
  • hollow body allows for large SA for faster rate of diffusion
  • tentacles allow for movement of water - maintaining deep concentration gradient
  • 2 cell thick wall allows for short diffusion distance.
28
Q

Explain why dietary antioxidants are important.

A
  • they stabilise free radicals
  • thus reducing oxidative stress
  • thus the risk of forming an atheroma is reduced because of a high amount of free radicals
  • this therefore reduces the risk of CVD.
29
Q

The calculators work out the risk of a person developing CVD in the next 10 years.
(i) Explain why the information entered by a person may lead to an
underestimate of their 10-year risk of developing CVD.
(2)

A
  • a person may estimate their cholesterol levels or any other factor on the calculator
  • some risk factors might not be included on the calculator
30
Q

Suggest why these two risk calculators may not be suitable for everybody
to use.

(2)

A
  • they may not have access to technology
  • they may have family history of CVD that’s not taken into account by the calc.
31
Q

Suggest why these risk calculators estimate the 10-year risk of
developing CVD.

A
  • CVD takes a while to develop .
32
Q

Explain the advantages for osmoconformers of having cells with solute

concentrations similar to that of the sea water they live in.

A
  • little water will move out through osmosis
  • thus the cell will not become dehydrated
  • also no risk of cells bursting due to osmosis
33
Q

Inheritance of different versions of these two genes shows genetic linkage.
Explain how the phenotypes of an individual can show genetic linkage in the
inheritance of two genes.
(2)

A
  • the alleles for both genes are on the same loci
  • therefore they are inherited together as a unit
34
Q

One gene can give rise to more than one type of protein through
post-transcriptional changes to the mRNA.
One of these changes is the removal of introns.
Explain how different proteins can be synthesised from this mRNA that has had
introns removed.
(3)

A
  • exons are cut out
  • exons are then spliced together to make different orders of exons
  • this is then translated to form a sequence of amino acids
  • this amino acid chain is then folded into its tertiary structure
35
Q

Describe the structure of a blastocyst.
(2)

A
  • outer cell layer
  • with pluripotent stem cells in the centre.
36
Q

Histone modification and DNA methylation are processes that occur when
totipotent stem cells develop into pluripotent stem cells.
Explain how these two processes alter the activation of genes in the cells.
(5)

A
  • histone mod may cause a a DNA strand to be more tightly wrapped around a histone protein
  • DNA methylation is when a methyl group is added a cytosine base
  • this means that RNA polymerase cannot bind to gene, and thus the gene cannot be transcribed or translated, and thus will not be expressed.
37
Q

Compare and contrast the structure and function of lysosomes
and acrosomes.
(3)

A
  • both are surrounded by a singular membrane
  • both contain enzymes
  • lysosomes are involved releasing enzymes for destruction of microbes whereas the acrosome is involved in breaking down the zona pellucida
38
Q

Explain how meiosis causes this genetic variation

A
  • due to independant assortment and crossing over
  • crossing over results in different combination of alleles
  • independent assortment results in different allele combinations in gametes
39
Q

Give two differences in the arrangement of the DNA in a cell at the beginning
of interphase and at the end of prophase I.

A
  • in interphase, DNA is still surrounded by a nuclear membrane but at the end of prophase 1 the nuclear membrane is broken down
  • in interphase, DNA is unwinded but at the end of prophase 1 it is condensed.
40
Q

What do do to get from cm—> micro meters

A

divide by 1000.

41
Q

Describe the function of pits in the xylem vessel.

A
  • movement of water between adjacent cells and tissues
42
Q

Name the 3 domains

A
  • bacteria, eukaryota and archea.
43
Q

What is calcium needed for in a plant

A
  • to form cell walls
  • to form calcium pectate
44
Q

An individual organism that can produce both egg cells and sperm cells is said to
be a hermaphrodite.
Each individual can produce both egg cells and sperm cells for sexual
reproduction with another blue dragon.
Their sperm cells cannot fertilise their own egg cells.
Suggest reasons why it may be advantageous for blue dragons to
be hermaphrodites.

A
  • can reproduce with any other blue dragon
  • sexual reproduction, so increases genetic diversity
  • so low risk of extinction
45
Q

describe the tertiary structure of an enzyme

A
  • has an active site
  • has disulfide bridges
  • has ionic bonds
  • is globular
46
Q

In a beetroot practical, In the first student’s experiment at 5 °C, the fluid was pale pink but the fluid
in the second student’s experiment was colourless.
Suggest an explanation for this difference.

A
  • solution was pale pink due to dye released by beetroot
  • the first student may have not rinsed this off.
47
Q

name one social or ethical issue with prenatal testing

A
  • risk of false positive
  • which could lead to termination of a healthy fetus.
48
Q

Explain why gene therapy has the potential to treat some genetic disorders.
(2)

A
  • genetic disorders have faulty alleles
  • but gene therapy uses normal functioning alleles which if implanted, can produce the normal functioning protein.
49
Q

Describe 4 risks of using statins to treating CVD

A
  • kidney failure
  • liver failure
  • headaches
  • joint pains
50
Q

Describe the structure of alpha glucose

A
  • ## OH on C1 pointing down
51
Q

what is the source of oxygen for synthesis of glucose in photosynthesis

A
  • CO2
52
Q

Describe how glucose is converted to sucrose after the calvin cycle

A
  • some glucose rearranged to fructose
  • fructose and glucose then joined together via a condensation reaction forming a 1,4 glycosidic bond.
53
Q

Below are some facts about baobab trees and Madagascar:
Ɣ there are nine species of baobab trees
Ɣ six of the species are found only in Madagascar
Ɣ two species are found in mainland Africa
Ɣ one of the species found in mainland Africa is also found in Madagascar
Ɣ one species is found in Australia
Ɣ all baobab trees are found in dry areas
Ɣ baobab trees can store thousands of litres of water
Ɣ baobab trees shed their leaves in the dry season
Ɣ baobab trees produce large, heavy seeds
Ɣ tortoises eat these seeds
Ɣ some species of tortoises have become extinct in Madagascar.

Explain how climate change could affect the populations of baobab trees.

A
  • conditions could become hotter
  • if tortoise population decreases, then there would be less seed dispersers
  • if becomes too hot, enzyme activity might be affected, too high for some enzymes to function.
54
Q

Suggest two reasons, other than climate change, for baobab trees becoming
endangered.

A
  • decrease in tortoise population
  • deforestation
55
Q

Recently, scientists claimed that they had inserted some genes from a woolly
mammoth into skin cells from an elephant.
Some scientists are concerned that this procedure could reduce conservation
efforts to protect elephants and other organisms found in their habitat.
Suggest why some scientists are concerned that this procedure could reduce
the number of elephants and other organisms found in these habitats.

A
  • could increase competition between elephants, and elephants and other species.
  • new features like a wool coat could increase poaching of these new elephants.
56
Q

Explain how GALP is used to produce lipids

A
  • GALP converted to glucose
  • glucose used to make glycerol and fatty acid chains
  • glycerol and fatty acid chains joined by ester bonds
  • through condensation reaction
57
Q

Explain why viruses contain only a few genes.

A
  • not complex structure
  • they use host cell proteins to make their own - eg reverse transcriptase.
58
Q

Describe the role of tRNA in protein synthesis.

A
  • brings a specific amino acid
  • to the m-RNA strand in translation
  • t-RNA binds to mRNA. (anticodon binds to t-RNA)
59
Q

describe the structure of collagen (4)

A
  • primary structure is sequence of amino acids.
  • consists of 3 polypeptide chains with cross links between chains
  • chains are coiled around each other
60
Q

Suggest the problems doctors face in prescribing antibiotics for ulcers.

A
  • prescribing the wrong antibiotic could increase chances of resistance
  • may not know which antibiotic has caused the ulcer, so one they prescribe might not be effective

Wrong Past paper questions (6 decks)

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