AQA BIO Flashcards
1
Q
USES OF MOLECULES
A
Amino Acid- is a monomer in an enzymes active site, forms a polymer that gives a positive result with a Biuret test
ATP- is produced during photosynthesis and respiration
Beta Glucose- is a monomer in glucose
Alpha Glucose- is a monomer in starch and glucose
2
Q
Test for Non Reducing Sugars
A
- Add HCl to the sample solution and heat in a water bath at 95C for five minutes.
- Remove sample from water bath and add Sodium Hydrogencarbonate to neutralise the HCl. Test the solution is slightly alkaline using red litmus paper which should turn blue.
- Add 2cm3 Benedict’s Reagent, solution should be blue, and heat in water bath at 95C for five minutes.If solution changes colour from blue to brick red reducing sugars are present.
3
Q
Arrangement of Phospholipids in a cell surface membrane
A
Phospholipid molecules are arranged in a bilayer where the hydrophobic tails point away from water and the hydrophilic heads point to water
4
Q
How is an ester bond is formed in a phospholipid molecule?
A
Condensation reaction between glycerol and fatty acid
5
Q
Property of Water that helps prevent temp increase in a cell
A
Water has a high specific heat capacity which means a lot of thermal energy is required to increase or decrease it’s temperature
6
Q
How does a work phagocyte destroy a pathogen present in the blood?
A
Phagocyte engulfs pathogens present in the blood forming a phagosome and fuses with lysosome. Enzymes in the lysosome hydrolyse the break down of the pathogen.
7
Q
Cells that trigger an Immune Response
A
- Cancer/ Tumour Cells
- Cells infected by a virus
- Cells from other organisms ie. from transplants
8
Q
Role of the disulphide bridge in forming the quaternary structure of an antibody
A
Joins together two different polypeptides
9
Q
The role of organelles in the production, transport and release of all proteins from Eukaryotic cells
A
DNA nucleus codes for proteins. Ribosomes on the surface of the Rough Endosplasmic Reticulum are the site of protein synthesis. They produce proteins which are then transported by Golgi Vessicles to the Golgi Apparatus which modifies and packages proteins. Golgi vesicles transport modified proteins to where they are needed in the cell. Proteins are then pinched off at the ends of the cisternae of the vesicles or vesicles fuse with the cell membrane and released via exocytosis.
10
Q
Why can the nucleus not be seen in the transmission electron micrograph?
A
Nucleus was not stained or is not in this section so is found in another part of the cell
11
Q
Advantages of using a TEM over a SEM to view a biological specimen
A
TEM has a higher resolution and you can see the internal structure of cellular organelles
12
Q
Calculation
A
70.65/ [150 x 10^8] = 4.71x10^7
13
Q
Mechanism that causes lungs to fill with air
A
Intercoastal muscles contract moving rib cage up and out, increasing area for lungs to expand into, and the diaphragm also contracts/ flattens. This causes the volume of air to increase which means the pressure decreases. Air moves down a pressure gradient from a higher to lower atmospheric pressure.
14
Q
Haematoxylin solution stains DNA a blue colour, why is this used to stain lung tissue?
A
Animal tissue does not contain starch and the nucleus contains DNA so it will make the nucleus visible.
15
Q
Evaluate this conclusion that these results concluded that all three risk factors are linked with asthma
A
The results support the conclusion as the the risk with living with a cat or dog is significant and the link with obesity is the most significant. However the risk with asthma and burned wood is not statistically significant.
16
Q
How is mRNA produced from an exposed template strand of DNA
A
Free activated RNA nucleotides are attracted to the exposed bases by complementary base pairing. RNA Polymerase catalyses a condensation reaction which causes phosphodiester bonds to form between new adjacent nucleotides joining them together. The resulting pre-mRNA molecule is then spliced to remove introns and form mature mRNA which can only then be used for translation into a protein molecule.
17
Q
What is an EXON
A
Nucleotide sequence that codes for a polypeptide chain.
18
Q
Binary Fission in Bacteria
A
Circular DNA is replicated and plasmids are replicated as well. Cytoplasm is divided to produce daughter cells
19
Q
Environmental variables that could be changed to increase growth rate of bacterial cells
A
- Increased concentration of Oxygen which means increased respiration
- Increased concentration of glucose which means increased respiration
- Increased temperature which means increased enzyme activity so faster rate
20
Q
Explain how the proteome of a cell from a genetically modified tobacco plant
(lines 5-7) differs from that of a cell from an unmodified control tobacco plant.
A
Expression of genes from a different species means one more protein in the range of proteins in the proteome.
21
Q
Explain how an increase in the rate of transcription of the PIP1b gene (lines 6-7) will affect the permeability of tobacco plant cell membranes to water.
A
Increased number of aquaporin made which will result in increased water permiability
22
Q
Suggest and explain one advantage and one disadvantage of increased stomatal
density on the growth of leaves
A
An advantage is that there will be a higher carbon dioxide uptake so more photosynthesis will occur leading to faster growth.
A disadvantage is that more water will also be lost through transpiration which means less photosynthesis so slower growth
23
Q
Littorina littorea is a species of snail found on rocky sea shores.
A student investigated variation in snail shell height in two populations of snails.
Give two ways in which the student could ensure his samples would provide a reliable measure of the variation between individuals in each population.
A
- Use a large sample size of over 100 snails
2. Select snails randomly to avoid unconscious bias
24
Q
The student could determine the median, mode and range from his measurement of shell heights in these populations.
Give two other statistical values the student could calculate from his measurement of shell heights in these populations.
A
- Interquartile Range
- Mean
- Standard Deviation
25
Name the taxon in the hierarchy of classification represented by:
1. Genus
| 2. Species
26
The student noticed there was a difference in shell height between these populations of snails. He wanted to investigate if the difference was significant.
Give a suitable null hypothesis to use in his investigation and name the statistical test to use with these data.
Null Hypothesis: There is no difference in the shell height between these two species
Statistical Test:
T- test
27
Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule.
A phosphodiester bond is formed by a condensation reaction between phosphate and deoxyribose which is catalysed by DNA Polymerase
28
Name the protein associated with DNA in a chromosome
Histone protein
29
In the process of semi-conservative DNA replication, the two strands within a DNA
molecule are separated. Each then acts as a template for the formation of a new
complementary strand.
Describe how the separation of strands occurs.
DNA helicase unwinds the DNA molecule by breaking the hydrogen bonds between complementary base pairs in the DNA molecule
30
Explain how an arteriole can reduce the blood flow into capillaries.
The arteriolar contracts which reduces the size of the lumen of the arteriole so less blood can flow into the capillaries
31
A student investigated the effect of ethanol, hydrochloric acid and temperature on the
loss of red pigment from beetroot cells.
During the procedure, the student:
• added 10 cm' water into one test tube
added 10 cm' ethanol into a second test tube
• added 10 cm' hydrochloric acid into a third test tube
• put the three tubes into a 25 °C water bath
• cut four cylinders of tissue from a beetroot
• put a cylinder into each tube and fitted bungs
• added 10 cm' water into a fourth test tube and put this tube into a
70 °C water bath
• placed the fourth cylinder into this tube and fitted a bung
• later removed the cylinders from the tubes
estimated the intensity of red pigment in each solution by eyesight.
Give one way in which the student could ensure the first three beetroot cylinders were kept at 25 °C throughout her experiment.
Use a thermometer to measure the temperature at intervals and if the temperature has fluctuated use appropriate corrective measure.
32
Give two variables that the student did not control in her procedure.
She did not control the length and diameter of the potato cylinders.
She did not control the length of time the cylinders were left in the individual solutions
33
What is the uncertainty of taking a reading of 10 cm with this measuring cylinder?
Suggest how you could reduce the uncertainty calculated.
Uncertainty: 2/2= 1
| Use an instrument with small intervals
34
Using Figure 3, what can you conclude about the damage caused to beetroot cells by water, ethanol, hydrochloric acid and different temperatures?
Provide explanations for your conclusions
The water at 25C caused no damage to the cell surface membrane so no pigment was released in tube E. Whereas ethanol and HCl at 25C caused similar damage to the membrane with the intensity of red pigment seen in F and G being similar. The water at 70C caused the most damage to the beetroot cells as temperature increases the particles in the membrane gain energy so move around more which increases the permeability of the membrane so more pigment is released seen by the highest intensity of red pigment.
35
A student investigated starch hydrolysis using the enzyme amylase.
During the procedure, the student:
• treated the starch to make it soluble
• prepared 10 cm' of different concentrations (mg dm-3) of starch solution
added an identical concentration of amylase to each starch solution
• measured the time in minutes to completely hydrolyse starch.
He repeated the procedure and calculated the mean time to completely hydrolyse
starch in each concentration of starch solution.
Draw a table the student could use to record all of his results.
You only need to show completed column headings.
Describe the results you would expect the student to obtain.
As starch concentration increases, time to digest starch will also increases.
36
A competitive inhibitor decreases the rate of an enzyme-controlled reaction.
Explain how
A competitive inhibitor is similar in shape to the substrate which is complementary to the specific enzyme so it will complementary to the enzyme active site. It would induce the active site to change shape and bind to form an enzyme- inhibitor complex, this means there are fewer enzyme active sites available for the substrate to be able to bind to. Less enzyme substrate complexes would be formed and as a result less reactions will be catalysed which will decrease the rate of reaction
37
When bread becomes stale, the structure of some of the starch is changed. This changed starch is called retrograded starch.
Scientists have suggested retrograded starch is a competitive inhibitor of amylase in the small intestine.
Assuming the scientists are correct, suggest how eating stale bread could help to reduce weight gain.
Less hydrolysis of starch to maltose and other disaccharides means less absorption of glucose and other monosaccharides (more starch is egested)
38
Give one reason why trout eggs produced by fielosis are genetically different.
1. Crossing over of genes
| 2. Independent segregation
39
A trout body cell contains 80 chromosomes.
Farmed female trout are treated so that they produce diploid egg cells.
The offspring produced from farmed trout are sterile. Suggest and explain why.
Extra set of chromosomes means that homologous chromosomes do not separate evenly so no meiosis occurs
40
Explain how HIV affects the production of antibodies when AIDS develops in a person.
This means less antibodies produces because HIV destroys helper T cells so few B cells undergo mitosis and form plasma cells.
41
A scientist measured the effect of a drug on the number of T cells and the numb
HIV particles in blood taken from a person with AIDS. The results are shown in Figure 5.
Symptoms of AIDS occur when the number of T cells is below 200 cells mm-3
Use all of this information to evaluate the effectiveness of the drug in treating AIDS…
The drug is not effective in treating AIDS because the number of T cells <200 at 4 months so drug is not effective so it does not remove all HIV particles. Furthermore the graph only shows results over 16 months and the sample size is only one person, side effects of the drug have not been recorded and no control group has been used to compare results.
On the other hand it is effective in treating AIDS because the number of T cells >200 after five months so drug can be effective as AIDS symptoms removed.
42
The mass flow hypothesis is used to explain the movement of substances through
phloem.
Use your understanding of the mass flow hypothesis to explain how pressure is generated inside this phloem tube.
Sucrose is actively transported into the phloem which reduces the water potential so water moves into the phloem by osmosis
43
Describe the relationship between phloem pressure and the rate of water movement in xylem in this plant.
The phloem pressure falls as rate of water movement in xylem increases
44
Phloem pressure is reduced during the hottest part of the day.
Use information inFigure 6 along with your understanding of transpiration and mass flow to explain why.
High temperatures means high rate of transpiration and evaporation through the stomata, this causes less water movement from xylem to phloem
45
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels
Micelles are formed when bile salts envelope the longer chain fatty acids and monoglycerides. Micelles carry the fatty acids and monoglycerides to the surface of the epithelial lining of the ileum and the fatty acids and monoglycerides diffuse out of the micelles and diffuse into the villi. In the villi the longer chain fatty acids and monoglycerides are recombined and packaged by the Golgi Apparatus and triglycerides are reformed. The triglycerides aggregate into a globule with cholesterol and other phospholipids and are coated in proteins to form chylomicrons. The chylomicrons move to the cell membrane and exit the villi via exocytosis and are absorbed into the lymp vessels and enter the lymphatic system.
46
Describe how the structure of a protein depends on the amino acids it contains.
The structure is determined by the relative position of amino acids. Primary structure is the sequence of amino acids to form a polypeptide chain. Secondary structure formed by hydrogen bonds and the folding of the chain. Tertiary structure is the 3D structure which is formed by hydrogen and ionic bonds and disulphide bridges, this also creates the active site in enzymes. Quaternary structure contains more than one polypeptide chain folded and bonded together by hydrogen, ionic bonds and disulphide bridges.
47
Type of bond between:
1. Complementary base pairs
2. Adjacent Nucleotides in a DNA Strand
1. Hydrogen
| 2. Phosphodiester bonds
48
Describe two differences between the structure of a tRNA molecule and the
structure of an mRNA molecule.
1. tRNA has anticodons whereas mRNA has codons
2. tRNA is a clover leaf shape whereas mRNA is linear
3. tRNA has hydrogen bonding, mRNA does not
4. tRNA has an amino acid bonding site whereas mRNA does not
49
In a eukaryotic cell, the structure of the mRNA used in translation is different from the structure of the pre-mRNA produced by transcription.
Describe and explain a difference in the structure of these mRNA molecules.
Pre-mRNA contains exons and introns which are non coding regions DNA which are spliced out of pre-mRNA and only exons which are coding regions of DNA remain in mature mRNA and used in translation
50
HIV STRUCTURE
Lipid envelope with embedded glycoproteins which surrounds a capsid (protein structure) which contains two strands of RNA and some enzymes including Reverse Transcriptase
51
Describe how HIV is replicated.
Attachment proteins attach to receptors on lymphocyte and the RNA renters the cell. Reverse Transcriptase converts RNA to DNA and viral protein and enzymes are produced. The virus is then assembled and releases from the cell.
52
Explain why it is not possible to determine the identity of the structures
labelled X using an optical microscope.
The resolution of an optical light microscope is too low because the wavelength of light is too long and the maximum magnification is also too low to see the structures of intracellular organelles.
53
U. marinum cells ingest bacteria and digest them in the cytoplasm
Describe the role of one named organelle in digesting these bacteria.
Lysosomes which are found in the cytoplasm of DNA fuse with the vesicle and release hydrolytic enzymes which hydrolyse the bacteria and digest them.
54
In large cells of U. marinum, most mitochondria are found close to the
cell-surface membrane. In smaller cells, the mitochondria are distributed evenly
throughout the cytoplasm. Mitochondria use oxygen during aerobic respiration.
Use this information and your knowledge of surface area to volume ratios to suggest an explanation for the position of mitochondria in large U. marinum cells.
Larger cells have a smaller surface are to volume ratio so takes longer for the oxygen to diffuse to mitochondria so less aerobic respiration
55
Figure 4 shows the arrangement of the genetic material in a cell during prophase.
Describe and explain the arrangement of the genetic material shown in Figure 4.
Chromosomes are condensing and becoming distinct. They are also arranged at random and not lined up since they are not attached to any spindle fibres.
56
Name the fixed position occupied by a gene on a DNA molecule.
Locus or Loci
57
Describe how a gene is a code for the production of a polypeptide. Do not include information about transcription or translation in your answer.
The nucleotide sequence is in codons/ triplets which determines the sequence of amino acids in a polypeptide.
58
Describe how the structure of glycogen is related to its function.
Glycogen is insoluble which means it does not affect water potential and does not leave the cell. It is coiled to form alpha helix so it is compact so only takes up a small amount of space when stored. It is branched so there are more ends for faster hydrolysis by enzymes. It is a polymer of glucose so it is easily hydrolysed into glucose for respiration.
59
The student wanted to use the data from plot 1 to estimate the total number of the beetle species in the meadow.The student wanted to use the data from plot 1 to estimate the total number of the beetle species in the meadow.
Suggest how the student should use the data from plot 1 and other information
provided to estimate the total number of the beetle species in the meadow.
The student should calculate the area of plot 1 and then the area of the whole meadow. Then divide the area of the meadow by the area of plot 1 before multiplying this number by 41 which is the number of beetles in plot 1.
60
Suggest one improvement to the design of Table 2 and one improvement to the
she presented the data contained in Table 2.
The independent variable should be on the first column on the left. The number of decimals places in the final column should be the same change 1.29 to 1.3.
61
Suggest and explain an advantage of carrying out this investigation at 30 °C rather than at 20 °C
At 30C the water has more kinetic energy so more osmosis will occur in the time available
62
The student concluded from the information in Table 2 that the water potential of the
solution inside the egg is higher than the water potential of the vinegar.
Is the student's conclusion correct? Justify your answer.
The student is incorrect as the final mass of the egg was higher than the initial mass. This means water has moved into the egg via osmosis so the egg water potential is lower than the vinegar water potential
63
The student wanted to determine the water potential of chicken eggs. She:
• produced a dilution series of sugar solution
• followed the procedure described on page 20.
She calculated the final mass to initial mass ratio of the egg covered in each sugar solution.
How would you advise the student to use her calculated ratios to determine the water potential of the eggs?
In your answer state the independent variable in the student's investigation.
The independent variable is the concentration of the sugar solutions in which the egg is placed in. She should plot a graph of her calculated ratios against the concentration of of sugar solution and draw a calibration curve. The point at which the line of best fit crosses the x-axis (where the net change is mass is zero) is the concentration of the solution within the egg. Use a graph to change the concentration into water potential.
64
Read the following passage.
Kidney cells produce a glycoprotein hormone called erythropoietin (EPO). An
EPO molecule contains 165 amino acids and approximately 50% of its mass is
carbohydrate.
EPO is transported in the blood and stimulates the bone marrow to produce
red blood cells. In this way, enough red blood cells are produced to maintain
the blood's oxygen-carrying capacity.
Some athletes choose to increase their blood EPO concentration by injecting
synthetic EPO. This practice is called blood boosting and is banned in sport as
a form of drug abuse. Athletics' authorities use a programme of drug testing to detect athletes who have injected EPO. In this programme, an ELISA test is performed on urine samples to measure the concentration of EPO in the athlete.
Two types of monoclonal antibody are used in this ELISA test:
anti-human EPO antibody, prepared by injecting human EPO into mice
• anti-mouse antibody, prepared by injecting anti-human EPO antibody into
goats. An enzyme is attached to the anti-mouse antibody.
Use the information in the passage and your own knowledge to answer the following questions.
1. Kidney cells produce a glycoprotein called erythropoietin (EPO) (line 1).
Identify two organelles in kidney cells that enable the production of EPO.
1. Organelles involved in protein synthesis are: Ribosomes and Golgi Apparatus
65
Explain the biological advantage to athletes of injecting synthetic EPO (lines 7-8).
More red blood cells means more transport of oxygen to muscles and tissues around the body. So more aerobic respiration can take place so moe ATP is produced so athletes can exercise for longer/ harder.
66
The general structure of a fatty acid is RCOOH.
| Name the group represented by COOH
Carboxyl
67
Figure 1 shows the structure of a fatty acid R group.
Name the type of R group shown in Figure 1
Explain your answer.
Alkene/ unsaturated hydrocarbon
| It contains a carbon carbon double bond.
68
Describe how you would test for the presence of a lipid in a liquid sample of food.
Add ethanol to the crushed sample and mix with a glass rod, then add water, if a milky white emulsion is formed then a lipid is present.
69
In 1935, scientists suggested a model for the chemical structure of a cell-surface
membrane. Figure 2 shows the membrane structure the scientists suggested.
Give one similarity and two differences between the membrane structure shown in Figure 2 and the fluid-mosaic model of membrane structure.
1. Similarity is both have a phospholipid bilayer
2. Difference is that fluid mosaic has channel and carrier proteins in the bilayer whereas figure 2 does not.
Difference is cholesterol is not present whereas in figure 2 but is present in the fluid mosaic model
70
Describe and explain one feature of the alveolar epithelium that makes the epithelium well adapted as a surface for gas exchange.
Do not refer to surface area or moisture
in your answer.
The epithelial layer has a one cell thickness which reduces diffusion pathway.
71
Tidal volume is the volume of air inhaled and exhaled during a single breath when a person is resting. The tidal volume in a person with emphysema is reduced compared with the tidal volume in a healthy person.
Suggest and explain how a reduced tidal volume affects the exchange of carbon
dioxide between the blood and the alveoli.
Less carbon dioxide will be exhaled out of the lungs so the concentration gradient will be reduced between the blood and the alveoli so a there will be a slower removal of carbon dioxide out of the blood
72
Give two structures found in all prokaryotic cells and in all eukaryotic cells.
1. Ribosomes
| 2. Cell membrane
73
Scientists have found that the rate of plasmid replication is faster in cells growing in a culture with a high concentration of amino acids than in a culture with a lower concentration of amino acids.
Suggest one explanation for the faster rate of plasmid replication in cells growing in a culture with a high amino acid concentration.
Amino acids are used in protein synthesis so more enzymes for plasmid replication.
74
What can you conclude from Figure 6 about a structural difference between the plasmids and the circular DNA? Explain your answer.
Plasmids are less dense than circular DNA molecules as they are higher up the centrifuge tube in figure 6
75
What can you conclude from Figure 6 about the effect of antibiotic X on plasmid replication and on circular DNA replication? Explain your answer.
Antibiotic X does not increase the replication circular DNA as the bands in both tubes are identical but causes the replication of plasmids to increase as the thickness of the band of plasmids in tube B is thicker than in tube A
76
Explain the appearance of the agar in the clear area surrounding well D.
The amylase in the solution added to well D has broken down the starch which the agar plate is made of.
77
What can you conclude about the activity of amylase from the appearance of the agar surrounding well E and well F in Figure 7?
Amylase is needed to break down the starch no the agar plate as there was no difference when just water was added. Amylase does not work after being exposed to high temperatures as the enzyme has been denatured
78
The fruit fly is a species of small insect.
The fruit fly has a gene that codes for an enzyme called alcohol dehydrogenase (AD).
AD catalyses the breakdown of alcohol when alcohol is in the insects' food.
The gene coding for AD has two alleles, ADF and ADS
The enzyme encoded by the ADF allele catalyses the breakdown of alcohol faster than the enzyme encoded by the ADS allele. Suggest why
The enzymes have a different primary structure so will have a different tertiary structure so the active site of the enzyme will be different. Therefore enzyme substrate complexes more likely with enzyme from ADF allele.
79
Alcohol is toxic to fruit flies. Suggest and explain why the frequency of the ADF allele changed during the 45 generations.
Flies with the ADF allele have a selective advantage so insects with the ADF allele are more likely to survive and reproduce, passing on the ADF allele so the allele frequency increases in the whole population
80
Describe how an ATP molecule is formed from its component molecules.
ATP is made of three main components which is Adenine, Pentose, and Three Phosphates which are joined together by a condensation reaction which is catalysed by ATP synthase
81
Using Figure 8 and the information provided, what can you conclude about amino acid uptake by G cells and by H cells?
Amino acid uptake is by active transport and cyanide reduces active transport. Enzymes do not work on the cell surface but enzymes are still active in the cytoplasm.
82
Explain five properties that make water important for organisms
Water is a metabolite in condensation / hydrolysis/ respiration/ photosynthesis. It has a specific heat capacity which means a lot of energy is required to change its temperature, so it resists changes in temperature. Water has a high latent heat of vaporisation so it can provided a cooling effect through evaporation. Water is a universal solvent so many ions and polar substances can be dissolved in it and can be transported efficiently as well as allowing many reactions to occur within cells. Water has a high cohesion due to its strong hydrogen bonding so it supports columns of water in plants and also produces surface tension supporting small organisms. Water is transparent so allows light to penetrate for photosynthesis if the surface freezes over.
83
Describe the process of semi-conservative replication of DNA.
DNA Helicase unwinds the strands of DNA in a DNA molecule by breaking the hydrogen bonds between complementary base pairs forming two template strands. Free activated nucleotides are attracted to the exposed bases by complementary base pairing. DNA Polymerase catalysed a condensation reaction forming phosphodiester bonds between the new adjacent nucleotides forming a new polynucleotide chain. Hydrogen bonds reform between complementary base pairs forming a new DNA molecule. This is known as semi conservative replication because each of the two new DNA molecules is made up of one strand from the original DNA molecule and one new strand.
