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PAST PAPER FLASHCSRD > PAST PAPER FLASHCARDS > Flashcards

PAST PAPER FLASHCARDS

1
Q

Biological molecules

A

Amino acid - is a monomer in an enzymes active site
Beta glucose- is a monomer in cellulose
ATP- is produced during photosynthesis and respiration
Amino acid-forms a polymer that gives a positive result with a buried test

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2
Q

Explain the arrangement of phospholipids in a cell surface membrane

A

Bilayer
Hydrophobic fatty acid tails point inwards repelling water
Hydrophilic phosphate heads point outwards towards aqueous water

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3
Q

State and explain the property of water that helps prevent temperature increase in a cell

A

Property: high specific heat capacity
Explanation: buffers changes in temperature

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4
Q

What is the role of the disulphide bridge in forming the quaternary structure of an antibody

A

Joins 2 different polypeptides

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5
Q

Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells

A

DNA- in nucleus code for protein
RER-produce protein
MITOCHONDRIA-produce ATP for protein synthesis
RER- produces proteins
GOLGI- modifies and packages proteins ready for transport on vesicles
VESICLES-transport proteins
VESICLES- vesicles fuse with cell surface membrane

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6
Q

Suggests why a nucleus is not visible

A

Nucleus not stained

Thin slice of the cell so the nucleus is in another part of the cell

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7
Q

Describe how a phagocyte destroys a pathogen present in the blood

A

Phagocyte engulfs pathogen
Forming phagosome and fuses with lysosome
Lysosomes Enzymes digest the pathogen

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8
Q

Give two types of cell other than pathogens, that can stimulate an immune response

A

Cancer cells
Cells from other organisms/transplants
Abnormal tumour cells
Cells infected by virus

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9
Q

Describe and explain the mechanism that causes the lungs to fill with air

A 
Diaphragm contracts 
External intercostal muscles contract 
Volume increases 
Pressure decreases in thoracic cavity 
Air enters from a higher atmospheric pressure
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10
Q

Haemotoxylin solution stains dna a blue colour
Iodine solution stains starch a blue colour
The scientist used haemotoxylin solution and not iodine solution to stain the lung tissue

A

Lung tissue does not contain starch

Nucleus contains DNA, so haematoxylin makes the nucleus visible

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11
Q

Describe how mRNA is produced from an exposed template strand of DNA

A

Free nucleotides attach and form complementary base pairs A-T and G-C
Through condensation reaction forming phosphodiester bonds
By action of RNA polymerase

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12
Q

Define the term exon

A

Triplet sequence coding for DNA

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13
Q

A scientist determined the growth rate of a b.subtilis cell by measuring its mass for 5 minutes
Suggest and explain how 2 environmental variables could be changed to increase the growth rate of these cells

A

Increased concentration of glucose-increased respiration
Increased concentration of oxygen- increased respiration
Increased temperature-increased enzyme activity
Increased concentration of phosphate-increased ATP/DNA/RNA
Increased concentration of nucleotides-increased DNA synthesis

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14
Q

Explain how the proteome of a cell from a genetically modified tobacco plant differs from that of a cell from an unmodified control of tobacco plant

A

Expression of a gene from different species

So more new proteins

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15
Q

Give 2 pieces of evidence that this cell was undergoing mitosis. Explain your answers

A

1 The individual chromosomes are visible because they have condensed
2 each chromosomes is made up of two chromatids because DNA has replicated
3 the chromosomes are not arranged in homologous pairs which they would be if it was meiosis

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16
Q

When preparing the cells for observation the scientist placed them in a solution that had slightly higher (less negative) water potential than the cytoplasm. This did not cause the cells to burst but moved the chromosomes further apart in order to reduce the overlapping of the chromosomes when observed with an optical microscope
Suggest how this procedure moved the chromosomes apart

A

Water moves into the cells by osmosis

Cells/cytoplasm gets bigger

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17
Q

Suggest one way the structure of the chromosome could differ along its length to result in the stain binding more in some areas

A

Differences in base sequences
Difference in histones/interaction with histones
Differences in condensation

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18
Q

What is a homologous pair of chromosomes

A

2 chromosomes that carry the same genes

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19
Q

Describe the method of potato cubes, also consider variables he should have controlled

A

1 method to ensure that all cut surfaces of the eight cubes are all exposed to the sucrose solution
2 method of controlling temperature
3 method of drying cubes before measuring
4 measure mass of cubes at stated time intervals

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20
Q

What is meant by the term species richness

A

A measure of the number of different species in a community

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21
Q

Suggest one consideration the scientists had taken into account to make sure the method was

A

Ethical: must not harm the Bees

Allow them to identify accurately the species to which each belonged: must allow close examination

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22
Q

Suggest and explain two ways in which the scientists could have improved the method used for data collection in this investigation

A

Collect at more times of the year so more points on graph and better line of best fit on graph
Counted number of individuals in each species so that they could calculate index of diversity
Collected from more sites /more years to increase accuracy of mean data

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23
Q

Lyxose binds to the enzyme

Suggest a reason for the difference in the results shown in the results with and without lyxose

A

Binding alters the tertiary structure of the enzyme
This causes Active site to change shape
So more successful enzyme substrate complexes form per minute

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24
Q

Explain directional selection

A

The scientists selected used for breeding plants that produced 2n gametes
So these plants passed on their alleles for production in of 2n gametes to the next generation
The frequency of alleles for production of 2n gametes increased in the population

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25
Q

Explain how the treatment with anti venom works and why it is essential to use passive immunity rather than active immunity

A

Antivenom antibodies bind to the antigen/venom and causes its destruction
Active immunity would be too slow/slower

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26
Q

A mixture of venoms from several snakes of the same species is used
Suggest why

A

May be different form of antigen/toxin within one species

Different antibodies are needed in the antivenom

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27
Q

Animals Are undergoing observation by a vet suggest one reason why

A

So the Animal does not suffer anaemia

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28
Q

Humoral response with the use of vaccines

A

Small volume given initially, as the B cells specific to the venom reproduce by mitosis
B cells produce plasma and memory cells
The second dose produces antibodies in the secondary immune response in high concentrations and quickly

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29
Q

The scientists concluded that the heat treatment damaged the phloem how

A

The radioactively labelled carbon is converted into sugar/organic substances during photosynthesis
Mass flow/translocation in the phloem throughout the plant only in plants that were untreated

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30
Q

The scientists concluded that this heat treatment does not affect the xylem
Explain how the results support

A

Water Content not different as because the means +-2 SD overlap
Water is still therefore being transported in the xylem

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31
Q

Compare and contrast the structure and properties of triglycerides and phospholipids

A

Both contain ester bonds between glycerol and fatty acid
Both contain glycerol
Fatty acids on both may be Saturated or unsaturated
Both are insoluble in water
Both contain C , H ,O but phospholipids also contain phosphate
Triglyceride has 3fatty acids and phospholipids have hydrophilic and hydrophobic region
Phospholipids form mono layer on the surface but triglycerides do not

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32
Q

Describe how lactose is formed and where in the cell it would be attached to a polypeptide to form a glycoprotein

A

Glucose and galactose
Joined by a condensation reaction
Joined by a glycosidic bond
Added to polypeptide in Golgi apparatus

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33
Q

Statements

A

Chloroplast has stacked membranes arranged in a parallel and contains DNA
Cell wall is made of polysaccharide
Golgi apparatus is an organelle and is not surrounded by two membranes

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34
Q

Human breast milk is produced and secreted by gland cells. These gland cells have adaptations that include many mitochondria and many Golgi vesicles. The milk contains a high concentration of protein
Explain the role of these cell adaptations in the production and secretion of breast milk

A

Many mitochondria release energy in the form of atp for movement of vesicles
,any Golgi vesicles transport protein milk to cell membrane out of cell

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35
Q

Two proteins have the same number and type of amino acid but different tertiary structures explain why

A

Different sequence of amino acids
Forms ionic disulphide and hydrogen bonds
In different places

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36
Q

Suggest one or facial reason of measuring the masses of frog eggs, tadpoles and adults compared with measuring their volume

A

Less error in measuring mass

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37
Q

Give 2 similarities In the movement of substances by diffusion and osmosis

A

Both move from an area of high concentration to low concentration DOWN a concentration gradient
Passive and not active process
Does not use energy from respiration
Use energy from the solution

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38
Q

Use your knowledge of transport across membranes to explain the shape of the curve (normal curve) for uptake of monosaccharides betweeen concentrations

A

Movement through carrier protein
Rate of uptake proportional to external concentration
Protein carriers are in use

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39
Q

Figure one is evidence for monoglycerides being lipid soluble molecules, suggest how? Graph looks like this /

A

Rate of uptake is proportional so Diffusion is occurring

Lipid soluble molecules diffuse and are soluble in phospholipid bilayer

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40
Q

The cell is in anaphase, suggest how the chemical stops,the root growing

A

Stops anaphase
By stopping spindle fibres from forming
Preventing the separation of sister chromatids
So No new cells are added to root tip

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41
Q

What is digestion

A

Hydrolysis of large insoluble substances to smaller soluble substances

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42
Q

Endocellulase amd Exocellulase act at different places on cellulose molecules suggest why

A

Active sites are different shapes

So different enzyme substrate complexes are formed

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43
Q

The scientists used the same concentration of endocellulase and exocelleulase in the mixtures. The rate of digestion of cellulose is greatest when both enzymes are present why

A

Endocellulase create more ends and increase SA

For exocellulase to act on/hydrolyse

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44
Q

Equation for percentage loss in mass

A

Initial mass-final mass
——————————- x100
Initial mass

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45
Q

Describe how a 1 in 10 dilution is made and how this can be used to create a 1 in 1000 dilution of the original liquid culture of bacteria

A

Add 1 part of bacteria culture to 9 parts sterile liquid
Mix well
Repeat using 9 parts fresh sterile liquid and 1 part of 10-1 and 10-2 dilution to make 10-3 dilution

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46
Q

The student looked at the cells in the 1 in 10 dilution. He decided not to use this dilution to determine the number of cells in the undiluted liquid culture
Suggest an explanation for the students decision

A

Count unlikely to be accurate And repeatable
Because too many cells
Because cells overlapping

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47
Q

Compare and contrast the dna in eukaryotic cells and dna in prokaryotic cells

A

Eukaryotic first
Associated with histones p not associated with histones
Linear p is circular
Longer p is shorter
Enclosed in a nucleus p is free to move around in the cytoplasm
Contains introns p does not contain introns
Comparisons
Nucleotide structured is identical
Nucleotides joined by phosphodiester bonds
Deoxyribose joined to phosphate in sugar phosphate backbone

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48
Q

Difference in the primary structure of haemoglobin molecules can provide evidence of phylogenetic relationships between species
Explain how

A

1 mutations change base
2 causing change in amino acid sequence
3 mutations build up over time
4 more mutations more differences in amino acid
5 Distantly related species have earlier common ancestor

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49
Q

Not all mutations in the nucleotide occur sequence of a gene cause a change in the structure of a polypeptide give 2 reasons why

A

Occurs in introns

Triplets code for the same amino acid

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50
Q

Give one example of using monoclonal antibodies in a medical treatment

A

Carries medicine to specific cells

Blocks antigen on cells

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51
Q

Describe the role of antibodies in producing a positive test result in an Elisa test

A

1st antibody is complementary to antigen
Second antibody with enzyme attached is added
Second antibody attaches to antigen
Substrate/solution added, colour changes

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52
Q

A student Carried out a Benedict’s test suggest a method other than using a colorimeter that this student could use to measure the quantity of reducing sugar in a solution

A

Filter

Dry out precipitate

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53
Q

Using a colorimeter in this investigation would improve the repeatability of the students results give one reason why

A

Quantitative
Colour change is subjective
Standardise the method

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54
Q

Explain why it is more useful to calculate an index of diversity than to record the species richness

A

Index of diversity also measures the population size of each species
So it’s useful because there may be many of some species

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55
Q

Suggest how a student measures the rate of water flow in the river

A

Digital device
Time taken to fill container of known volume
Use of data logging device

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56
Q

Give one way in which a sampling procedure could be standardised

A

Same size of area sampled
Same size net
same sampling
Samples taken at the same time of day

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57
Q

A lot of detail cannot be seen using an optical microscope why

A

Light has longer wavelength

So lower resolution

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58
Q

What happens as the depth of water increase

A

Further down the depth of water the oxygen concentration increases

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59
Q

How do fish adapt to lower oxygen concentration

A

The lower the oxygen concentration
The larger the SA to body mass
Supplies enough oxygen for respiration

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60
Q

Explain how the active site of an enzyme causes a high rate of reaction

A

Lowers activation energy
Induced fit causes active site of enzyme to change shape
So ESC causes bonds to break

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61
Q

Suggest a change that the student can make to his procedure so that 10cm3 of oxygen would be produced in less than 6 seconds

A

Use bigger chips
Increase temp
Change ph

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62
Q

Describe two ways in which dipeptides are similar and one way in which they may differ

A 
Similarities 
Amine group at the end 
Carboxyll group at the end 
2 R groups 
All contain C H O and N

Differences
Variable R

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63
Q

Explain what the positions of amino acids show

A

1 move to negative electrode as they are positively charged
2 amino acids move different distances as they have different charges
3 one spot has two amino acids this is because both amino acids have the same charge

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64
Q

Suggest why preventing formation of spindle fibres prevented cell cycle

A

Chromosomes cannot attach to spindle
So no metaphase
Chromosomes cannot separate on spindle so no anaphase

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65
Q

Suggest why a drug is still sued for cancer even tho it affects some healthy cells

A

Cancer cells divide more rapidly and uncontrollably

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66
Q

Give two molecules in which a ribosome is made

A

RNA
Nucleotide
Amino acids
Ribosomal protein

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67
Q

Describe the role of a ribosome in the production of a polypeptide do not include transcription

A

mRNA binds to ribosome
tRNA with anticodon binds
Catalyses the formation of a peptide bond between amino acids
Moves along the mRNA to the next codon

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68
Q

In a eukaryotic cell the base sequence of the mRNA might be different from the sequence of pre mRNA

A

Introns removed

Introns removed from pre mRNA thru splicing

69
Q

Describe the structure of glycogen

A

Polysaccharide of alpha glucose

Joined by glycosidic bonds

70
Q

Suggest and explain two ways the cell surface membrane of the cells lining the uterus may be adapted to allow rapid transport of nutrients

A

Membrane folded so increase SA
Large number of protein channels for FD
Large number of protein channels for active transport/co transport

71
Q

NHE3 actively transports one sodium ion into the cell in exchange for one proton out of the cell
Use your knowledge of transport across membranes to suggest how NHE3 does this

A

Co transport
Uses the hydrolysis of ATP
Sodium ion and proton bind to the protein
Protein changes shape to move sodium ion and proton across the membrane

72
Q

High salt absorption can result in a higher than normal concentration of salt in the blood plasma entering capillaries. This can lead to build up of tissue fluid explain how

A

Higher salt results in higher blood pressure

So more fluid is pushed out at the arteriole end of the capillary

73
Q

Explain the shapes of the curve at 50 degrees and 60 degrees

A

Both enzymes denatured by high temperatures
Denaturation is faster at 60 degrees due to more kinetic energy
Breaks the H bonds between amino acids
Results in the change in the shape of the active site so no longer complementary, so fewer esc formed

74
Q

Suggest an advantage of a bacterium secreting extra cellular proteases in its natural environment

A

To digest protein
So they can absorb amino acids for growth
Or destroy a toxic substance

75
Q

Describe the action of MEMBRANE BOUND dipetidases and explain their importance

A

Amino acids can cross cell membrane
Dipeptides can’t cross the cell membrane
Maintains concentration gradient of amino acids for absorption

76
Q

Reaction catalysed by ATP synthase

A

ADP + pi ——> ATP + H2O

77
Q

Suggest why human ATP synthase is not inhibited and bacterial synthase is inhibited

A

Human ATP synthase has a different 3 structure to bacterial ATP synthase

78
Q

Scientists suggested to use both current and new antibiotic why

A

New antibiotic doesn’t completely cure all the bladder infection
Resistant bacteria will reproduce to produce more resistant bacteria
Use of both antibiotics would kill bacteria resistant to other antibiotics

79
Q

Suggest reason for temperature remaining constant and disks being shaken

A

Temp- so that rate of diffusion of ions out of cell remains constant
Shaken- all surfaces of the leaf were exposed to the water

80
Q

Describe how phagocytosis of a virus leads to presentation of its antigens

A

Phagosome fuses with lysosome
Virus destroyed by lysosomes
Antigen from virus are displayed on the cell membrane

81
Q

Describe how presentation of a virus antigen leads to the secretion of an antibody against this virus antigen

A

Helper T cell stimulates specific B cells
B cell clones
Forms plasma cells that release antibodies

82
Q

State 3 comparisons of genetic diversity that the scientists can use

A

The base sequence of dna
The base sequence of mRNA
The amino acid sequence of proteins

83
Q

Explain how the presence of gills adapts a damselfly to its way of life

A

Damesfly larvae have higher metabolic/respiratory rate

So uses more oxygen

84
Q

Describe how scientist should collect and process data from these seeds to investigate whether there is a difference in seed size between two populations of trees

A

Use a random sample of seeds from each population
Use a large enough sample so it can be representative of whole population
Indication of what size was measured
Calculate a mean and SD for each population
Use students t test
Analyse whether there is a significant difference between the means of the 2 populations

85
Q

Describe the 2 differences between structure of cellulose molecule and glycogen molecule

A

Cellulose molecule has a straight chain whereas glycogen is branched
Cellulose molecule has straight chain and glycogen is coiled
Glycogen has 1-4 and 1-6 glycosidic bonds and cellulose has 1-4 glycosidic bonds

86
Q

The student controlled the volume of water in each tube why
If too much water the conc of pigment in solution will be lower
So solution will appear lighter , less light passes through than expected

A
87
Q

Suggest how the increase in temp of water caused the release of the pigment

A

Damage to cell surface membrane
Membrane protein denatures
Increased fluidity/damage to the phospholipid bilayer

88
Q

Multiple copies of AMY1 gene is an adaptation to high starch suggest how this evolved through natural selection

A

Mutation produces extra copies of AMY1 gene
Those with copies of the gene will survive and reproduce
And pass on these multiple copies to offspring

89
Q

Suggests how scientists could obtain data to produce a calibration curve and how they would use this calibration curve to find the concentration of protein in a sample of blood plasma

A

Produce a calibration of known concentrations of protein
Measure absorbance of each concentration
Plot a graph of absorbance on y axis against conc on x axis and draw a curve
Use absorbance of sample to find protein concentration from curve

90
Q

Older people are more likely to suffer from infectious disease due to a decrease in mean conc of protein in the blood as people get older

A

Lower plasma protein concentration

Suggests fewer antibodies

91
Q

Explain how the changes in the shape of haemoglobin result in the s shaped oxyhemoglobin dissociation curve for hbA

A

First oxygen binds to haemoglobin causing a change in the shape
Shape change allows more o2 to bind easily

92
Q

At birth 98% of haemoglobin in Hbf by 6 months the hbf has usually complete,y disappeared fro, the baby’s blood and been replaced by the hbA
Why is this an advantage

A

HbA has a lower affinity for oxygen at lot pO2

Easier unloading of o2 for aerobic respiration

93
Q

Describe how the student could use an eyepiece graticule to determine the mean number diameter of stomata

A

1 measure each stoma using an eyepiece graticule
2 calibrate eye piece graticule against stage micrometer
3 take a number of measurements to calculate a mean

94
Q

Ava is a substance that some plant species produce when little water is available explain why producing these may help plants living in dry environments to survive in dry conditions

A

Causes less stomatal opening so less transpiration

So more water available for photosynthesis so less water needed from the dry soil

95
Q

Describe how pathogens cause disease

A

Release toxins

Kill cells

96
Q

Putting homey on a cut kills bacteria. Honey contains a high concentration of sugar, use your knowledge of water potential to suggest how putting homey on a cut kills bacteria

A

Water potential in bacterial cell higher than in homey
Water leaves bacteria by osmosis
Loss of water stops metabolic reactions such as respiration
So cell dies

97
Q

Describe how tissue fluid is formed

A

Overall outward pressure

Forces small molecules out of the capillary

98
Q

High blood pressure leads to an accumulation of tissue fluid explain how

A

High Blood pressure = high hydrostatic pressure
Increases outward pressure from arterial end of capillary
So more tissues fluid is formed and less is absorbed

99
Q

The water potential of the blood plasma is more negative at the venule end of the capillary than at the arteriol end of the capillary explain why

A

Water has left the capillary
Proteins in blood too large to leave capillary
Giving higher concentration of blood proteins and therefor water potential

100
Q

How would you measure percentage of lipid in plasma membrane by mass

A

Divide mass of each lipid with total mass of all lipids

X100

101
Q

Ecology has no cholesterol but maintains a constant shape how

A

Cell unable to change shape
Because cell has cell wall
Cell wall made of Murein

102
Q

Define processed data

A

Calculations made from raw data

103
Q

Describe how you would use a student’s table to to find water potential in potato tissue

A

Plot a graph with concentration on x-axis and %change on y axis
Find conc where curve crosses the x axis-where percentage change is 0
Use another resource to find water potential of sucrose concentration where curve crosses x-axis

104
Q

Stomata close when light is turned off explain advantage

A

As water is lost through the stomata
Closure prevents the water loss
This maintains water content of cells

105
Q

Uptake of co2 falls to 0 when light is turned off why

A

No use of carbon dioxide in photosynthesis in the dark

No diffusion gradient maintained for co2 into leaf

106
Q

ABA Is a substance that some plant selfies reduce when little water is available
Explain why producing ABA may help these species survive in dry conditions

A

Causes less stomatal opening so less transpiration

So more water available for photosynthesis so less water needed from the dry soil

107
Q

Many species of plants can be infected by powdery mildew which is spread by microscopic spores in the air
Suggest how treatment protect plants against powdery mildew

A

Close the stomata so less spores enter the leaf

108
Q

Describe how the change in chromosome number in patau syndrome was produced

A

Homologous chromosomes do not separate in meiosis

109
Q

Explain why all the cells of the body will have this mutation

A

All cells derived from zygote by mitosis

Mitosis produces genetically identical cells

110
Q

Suggest how a flow of blood between the aorta and the pulmonary artery could cause children to die in the first 12 months

A

Some of the oxygenated blood from the aorta flows into the pulmonary artery
So less o2 delivered to cell for aerobic respiration
Tissues and organs do not develop properly causing death

111
Q

Describe the cohesion tension theory of water transport in the xylem

A

1 water lost from the leaf because of transpiration
2 this lowers the water potential of the mesophyll cells
3 water pulled up the xylem creates tension
4 water molecules stick together by hydrogen bonds
5 forming a continuous column of water
6 adhesion of water molecules up walls of xylem

112
Q

Contrast the structures of ATP and a nucleotide found in DNA to give 2 differences

A

ATP base always adenine but in DNA it can vary
ATP contains 3 phosphate groups but DNA contains 1 phosphate group
ATP contains Ribose whereas DNA contains deoxyribose

113
Q

Explain purpose of boiling agar

A

To kill all bacteria so no contamination

114
Q

Why do we transfer the same volume of liquid culture onto each agar plate

A

So same number of bacteria transferred

To allow comparison

115
Q

A student concluded we need 15 units of propanol

Describe how you would obtain a more accurate estimate of the minimum concentration of propanol

A

Several values between 10 and 15 units

Repetitions of each

116
Q

Name the process by which fatty acids and glycerol enter the intestinal epithelial cell

A

Diffusion

117
Q

Explain the advantage of lipid droplet and Micelle formation

A

Droplet increase SA for lipase enzyme action
So faster hydrolysis of triglycerides
Micelles carry fatty acids and glycerol through membrane to intestinal epithelial cell

118
Q

Explain how the Golgi is involved in the absorption of lipids

A

Modifies triglycerides
Combines triglycerides with proteins
And forms vesicles

119
Q

Order of valve opening

A

Av valve closes
Sl valve opens
Sl valve closes
Av valve opens

Coco

120
Q

Explain the role of the heart in formation of tissue fluid

A

Contraction of ventricles
Produces high hydrostatic pressure
This forces water and some dissolved substances out of blood capillaries

121
Q

Suggest how a blockage in the lymphatic system could cause lymphoedema

A

Excess fluid builds up

122
Q

Explain how chromosome number is halved during meiosis

A

Homologous chromosomes pair up

One of each pair goes to each daughter cell

123
Q

Describe the process of crossing over and how it increases genetic diversity

A

Homologous pairs of chromosomes associate
And form bivalent
Chiasmata form
Equal lengths of non sister chromatids are exchanged
Producing a new combination of alleles

124
Q

Describe how you would use cell fractionation techniques to obtain a sample of chloroplasts from leaf tissue

A

Use homogeniser to break open leaf contents filter out any debri
Centrifuge
At different increasing speeds
Until chloroplast fraction obtained

125
Q

Define species

A

Organisms that are able to reproduce to produce fertile offspring

126
Q

Define species richness

A

The number of different species in a community

127
Q

Suggest and explain why AZT does not destroy hiv in the body but stops or slows development of aids

A

Person infected with hiv still has hiv dna in their dna
New hiv particles are still made
AZT inhibits reverse transcriptase
AZT stops these new hiv particles from forming new hiv dna
Stops the destruction of more newly infected T cells
So immune system continues to work

128
Q

Suggest how a rabbit eating its own caecal droppings helps a rabbits digestion and absorption of dietary protein

A

More undigested protein broken down
So more amino acids are absorbed
Because protein/food passes again through stomach

129
Q

What is the role of single stranded dna in semi conservative replication

A

Acts as a template

Determines order of nucleotides

130
Q

Describe and explain the role of antibodies In stimulating phagocytosis

A

Antibodies bind to antigen

Antibodies cause agglutination

131
Q

Scientists hypothesised that memory B cells had formed in the mice 180 days after 3rd injection how can they test this

A

Symptoms do not develop
Add enzyme attached to antibody against memory cell
Colour change shows memory cell is present

132
Q

Student measured the time taken for water movement

Give two other measurements he made to calculate the rate of water movement

A

Initial mass and final mass of beaker and all contents

Number of groups of xylem vessels

133
Q

Give reason for adding a layer of oil to water in the beaker

A

Prevent evaporation

134
Q

How are 2 genetically identical daughter cells made during interphase in mitosis

A

Dna replicated
Involving specific accurate base pairing
2 identical sister chromatids
Each chromatid is moved to opposite poles of cells

135
Q

Why do optical microscopes require a thin specimen

A

Allows more light through

Allows single layer of cells to be viewed

136
Q

What precautions need to be made to ensure mean number of capillaries are reliable

A 
Field of view randomly chosen
Several fields of view 
Same species of animal 
Same muscle or organ used
Use at least 8 animals
137
Q

Describe how a high pressure is produced in the leaves

A

Water potential becomes lower
Water enters phloem by osmosis
Increased volume of water causes increased pressure

138
Q

During experiment scientists ensures that the rate of photosynthesis of their plants remained constant explain why this was important

A

Rate of photosynthesis related to rate of sucrose production

Rate of translocation higher when sucrose concentration is higher

139
Q

Describe the mass flow hypothesis for the mechanism of translocation in plants

A

In source, leaf sugars are actively transported in phloem
By companion cells
Lowers the water potential of seive cell so water enters by osmosis
Increase in pressure causes mass movement towards sink
Sugars are used

140
Q

Name the process that produced the co2 released from the trunk

A

Respiration

141
Q

What other info is required in order to calculate the mean rate of movement of the C down the trunk

A

Length of trunk

142
Q

Properties of triglycerides

A

1 Acts as an energy storage- large ratio of energy storing carbon hydrogen bonds compared to the number of carbon atoms, a lot of energy is stored in the molecule
2 metabolic water source due to high ratio of hydrogen to oxygen atoms
3 release water If oxidised this is essential for animals in the dessert such as camels
4 triglyceride do not affect water potential and osmosis as they are large and hydrophobic making them insoluble in water
5 lipids have a low mass- a lot can be stored without increasing mass and preventing movement

143
Q

Suggest three reasons why it’s more efficient to attach lactase to the beads

A

No need to remove milk
Beads used again
Allows continuous process
The enzymes more stable

144
Q

The lactose feee milk made after hydrolysis with lactase tastes sweeter than the cows milk containing lactose. Suggest why

A

Lactose hydrolysed to galactose and glucose

So more sugars are produced therefore sweeter

145
Q

What reducing sugars or sugar would you expect to be produced during chewing give a reason

A

Maltose

Salivary amylase breaks down starch

146
Q

What other enzymes are required to break down starch

A

Maltase

147
Q

In the control experiments cooked wheat was chopped up to copy the effects of chewing suggest a more appropriate Control experiment

A

Add boiled saliva

Everything same as experiment but salivary amylase denatured

148
Q

Explain why Maltase only breaks down maltose and allows this reaction to take place at normal body temp

A

Tertiary structure of the Maltase enzyme means
Active site is complementary to maltose
Active site and substrate fit together
Enzyme is a catalyst so lowers activation energy required for this reaction
By forming ESC

149
Q

A sports drink may provide an energy boost as

A

Drink contains carbohydrates so raises blood glucose conc quickly
Contains salt so glucose more rapidly absorbed
Increases glucose to muscles for respiration
More faster respiration so more faster energy release

150
Q

Suggest one advantage of the different percentage of cholesterol in red blood cells compared with Cells lining the ileum

A

Red blood cells are free in the blood

So cholesterol helps to maintain the shape

151
Q

E.coli has no cholesterol in its cell surface membrane. Despite this the cell maintains a constant shape explain why

A

Cell unable to change shape
Because cell has a cell wall
Cell wall made of Murein

152
Q

Explain why monitoring the ph of the mixture could show whether the cats milk contained lipase

A

Hydrolysis of lipids produces fatty acids

Which lower ph of mixture

153
Q

2 ways in which fatty acids are important in the formation of new cells

A

Fatty acids respired to release energy
More triglycerides more energy released
Energy used for cell production

154
Q

Use your knowledge of enzyme actions to explain why the arrows point in opposite directions

A

DNA has antiparallel strands
Shape of nucleotide is different
Enzymes have active sites with specific shape
Only 3’ can bind with active site of enzyme

155
Q

Suggest why the plasmids were injected into the eggs of silkworms rather than INTO the silkworms

A

If injected into egg, gene gets into most of the cells of the silkworms so gets into cells that make silk

156
Q

The scientists ensured the spider gene was expressed only in cells within the silk glands what would have the scientists inserted into the plasmid along with the spider genes to ensure that the spider gene was only expressed in the silk glands of silk worms

A

Promotor region

157
Q

What is the function of coronary arteries

A

Carry oxygen to heart muscles

158
Q

Other than slow blood flow give one advantage of capillaries being narrow

A

Shower distance between blood and outside of capillary
Large surface area of blood in contact with walls of capillaries
Fast diffusion

159
Q

Explain the import’s of maintaining a constant blood ph

A

Haemoglobin affected by change in ph
Results in the change of shape of haemoglobin tertiary structure
So less o2 binds to with haemoglobin

160
Q

Describe how an asthma attach caused the drop in the mean FEV shown in figure below. FEV is forced expiration volume per second

A

1 muscle walls of bronchi contract
2 Walls of bronchi secrete more mucus
3 diameter of airways reduced
4 therefore flow of air reduced

161
Q

Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs

A 
Trachea and bronchi and bronchioles 
Down pressure gradient 
Down diffusion gradient
Across alveolar epithelium
Across capillary endothelium
162
Q

How are phloem cells adapted for their function

A

Few organelles

So easier flow

163
Q

The ecologists captured insects from a number of sites on the island Suggest how they decided where to take their samples

A

Draw grid over map of area

Select coordinates at random

164
Q

Give two assumptions made when using the mark release recapture method

A 
No immigration 
No losses to predation
Marking does not affect survival 
Birth rate and death rate equal 
In this case, all belong to one population
165
Q

Suggest how the student would obtain data to give a more precise value for the index diversity of this habitat

A

Take more samples and find mean use a random sample (random coordinates)

166
Q

Suggest why there was such great variation in the height of traps

A

Trees vary in height

167
Q

Calculate no.of … after release of marked

A

N= M x C
———
R

168
Q

What 2 measurements are needed to calculate an index of diversity

A

Number of individuals of each species

Total number of individual

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