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aqa biology1 jan12
AQABIOLOGYAS!
| Question | Answer |
|---|---|
| Some seeds contain lipids. Describe how you could use the emulsion test to show that a seed contains lipids. | 1. Crush/grind; 2. With ethanol/ alcohol; 3. Then add water/then add to water; 4. Forms emulsion / goes white/cloudy; |
| A triglyceride is one type of lipid. The diagram shows the structure of a triglyceride molecule. A triglyceride molecule is formed by condensation. From how many molecules is this triglyceride formed? | 4 |
| The structure of a phospholipid molecule is different from that of a triglyceride. Describe how a phospholipid is different. | 1. Phosphate/ PO4; 2. Instead of one of the fatty acids / and two fatty acids; |
| Use the diagram to explain what is meant by an unsaturated fatty acid. | 1. Double bonds (present); 2. Some/two carbons with only one hydrogen / (double bonds) between carbon atoms / not saturated with hydrogen; 3. In (fatty acid) C/3; May show 1 and 2 on diagram |
| A person with asthma breathed out as hard as he could. The graph shows the volume of air he breathed out in the first 6 seconds of a breath. Curve A shows the volume before he used an inhaler. Curve B shows the volume after he used an inhaler. | |
| Explain how the diaphragm helps to bring about the changes shown by the curve A. | 1. (Diaphragm/diaphragm muscle) relaxes/relaxed; 2. Domed shape / (diaphragm) moves up; 3. Increases pressure; 4. Decreases volume; |
| You could use curve A to find the total volume of air that this person could breathe out in one complete breath. Describe how. | 1. Extend/extrapolate curve/graph; 2. (Read off where) it flattens/ reaches maximum / peaks |
| The inhaler which the person used contained a substance that dilates bronchioles. Use this information to explain why curve A is different from curve B. | 1. (Without inhaler) narrower bronchioles / bronchioles not dilated; 2. Muscle (surrounding bronchioles) contracted; 3. Less air able to pass through / more difficult for air to pass through |
| The table shows some features of cells. Complete the table by putting a tick in the box if the feature is present in cholera bacterium Cell-surface membrane Flagellum Nucleus | cell membrane flagellum |
| The table shows some features of cells. Complete the table by putting a tick in the box if the feature is present in epithelial cell of intestine Cell-surface membrane Flagellum Nucleus | cell membrane nucleus |
| The table shows some features of cells. Complete the table by putting a tick in the box if the feature is present in epithelial cell from alvelous of lung Cell-surface membrane Flagellum Nucleus | cell membrane nucleus |
| The diagram shows part of an epithelial cell from an insect’s gut Use the diagram to explain how this cell is adapted for each of these functions. Use a different feature in the diagram for each of your answers.. | |
| The active transport of substances from the cell into the blood | 1. Mitochondria respire; 2. Release energy/ produce ATP; 3. Transport against gradient; OR 4. Infolding of membrane; 5. Increases area; 6. More proteins for active transport |
| The synthesis of enzymes | 1. Ribosomes make proteins/ enzymes; 2. Enzymes are proteins; OR 3. Mitochrondria respire; 4. Release energy/produce ATP; 5. (Energy/ATP) for protein / enzyme synthesis; |
| Rapid diffusion of substances from the lumen of the gut into the cytoplasm | Microvilli increase area / have large area |
| Scientists who investigate disease may look at risk factors. What is a risk factor? | Something that increases chance / increases probability / makes it more likely |
| Scientists investigated the link between pollution from vehicle exhausts and the number of cases of asthma related to A the concentration in the air of substances from vehicle exhausts B the number of cases of asthma. | GRAPH |
| Between which years on the graph was there a positive correlation between the number of cases of asthma and the concentration in the air of substances from vehicle exhausts | 1976 –/to/and 1980; |
| Between which years on the graph was there a negative correlation between the number of cases of asthma and the concentration in the air of substances from vehicle exhausts? | 1980 –/to/and 1996; |
| The scientists concluded that substances in the air from vehicle exhausts did not cause the increase in asthma between 1976 and 1980. Explain why | Correlation does not mean that there is a causal relationship; May be some other factor, Associated with vehicles and asthma / producing rise in both; (After 1980) asthma continues to rise but exhaust concentration falls / negative correlation |
| The human heart has four chambers. In which one of the four chambers of the human heart does pressure reach the highest value | Left ventricle; |
| Explain how the structure of the left ventricle causes this high pressure | thick muscle/thick walls |
| Table shows the volume of blood in a man’s right ventricle at different times during one cardiac cycle. Time/s Volume of blood/cm3 0.0 125 0.1 148 0.2 103 0.3 70 0.4 56 0.5 55 0.6 98 0.7 125 | |
| Use the data in the table to calculate the man’s heart rate. Heart rate = .......... beats per minute Use this answer to calculate the man’s cardiac output. Show your working. Cardiac output = ....cm3 per minute | 85.7/86; Two marks for correct answer of 7905 – 7998;; One mark for incorrect answer in which candidate provides evidence of multiplying heart rate by stroke volume |
| Use information from table to show whether the valves are open or closed at each of the times shown Time/s Valve between right atrium Valve between right ventricle 0.2 & right ventricle & pulmonary artery 0.6 | 1. Closed open; 2. Open closed; |
| The diagram shows an antibody molecule. 6 (a) What is the evidence from the diagram that this antibody has a quaternary structure? | Has more than one/four polypeptide chains / made up of polypeptide chains; |
| Scientists use this antibody to detect an antigen on the bacterium that causes stomach ulcers. Explain why the antibody will only detect this antigen. | 1. Antibody/variable region has specific amino acid sequence/primary structure; 2. The shape/tertiary structure of the binding site; 3. Complementary to/fits/binds with these antigens; 4. Forms complex between antigen & antibody |
| Aspirin is a very useful drug. reading prnt | aspirin artlce to print out |
| Name the monomers that make up the active site of the enzyme | Amino acid / amino acids ; |
| The diagram shows the pathways by which prostaglandins and thromboxane are formed. Aspirin only affects one of the enzymes in this pathway Use reading to explain why aspirin does not affect the other enzymes | 1. Affects one monomer/amino acid; 2. Not found in all active sites; |
| Which enzyme, X, Y or Z, is inhibited by aspirin? Explain the evidence from the passage that supports your answer. Enzyme Explanation | 1. X; 2. Enzyme in both pathways; |
| Aspirin is an enzyme inhibitor. Explain how aspirin prevents substrate molecules being converted to product molecules. | 1. Occupies/blocks/binds to active site; 2. Substrate will not fit / does not bind / no longer complementary to / enzyme-substrate complex not formed |
| Aspirin may reduce the risk of myocardial infarction. Explain how. | 1. Prevents/reduces formation of thromboxane; 2. Blood clots do not form / less likely to form; 3. (Do not block) coronary arteries / vessels; 4. Heart muscle/wall gets oxygen |
| Vaccines protect people against disease. Explain how. | Vaccines contain antigens/antigens are injected; Dead pathogens/weakened pathogens; Memory cells made; 2nd exposure memory cells produce antibodies/become active/recognise pathogens; cont |
| More & rapid production antibodies Antibodies destroy pathogens; Herd effect | |
| Oral rehydration solutions (ORS) are used to treat diarrhoeal disease. What does an ORS consist of and how does it work? | 1. Contains glucose/starch/ carbohydrate / sugar; 2. Sodium/salt; 3. Co-transport / symport; 4. Sodium and glucose taken up (from lumen); 5. Lowers water potential in cells/ increases water potential gradient; 6. Water taken up by osmosis |
| Explain how downward movement of the diaphragm leads to air entering the lungs. | 1. Increases volume (in lungs/thorax); 2. Lowers pressure (in lungs/thorax); 3. Air (pushed) in by higher outside pressure / down pressure gradient; |
| Pulmonary ventilation =........ × .......... | Tidal volume and ventilation rate; |
| Organelle X is a mitochondrion. What is the function of this organelle? | (Aerobic) respiration; |
| This photograph was taken using a transmission electron microscope. The structure of the organelles visible in the photograph could not have been seen using an optical (light) microscope. Explain why. | Optical microscope 1. Has low resolution/not high enough resolution; 2. (Because) wavelength of light not short enough/too long; |
| Name the monosaccharides of which the following disaccharides are composed. lactose | |
| Name the monosaccharides of which the following disaccharides are composed. sucrose | |
| What enzymes are involved in the digestion of starch | Amylase and maltase |
| Product of enzyme reaction and where enzyme produced maltase | in/on epithelium (of small intestine), produces glucose |
| Product of enzyme reaction and where enzyme produced amylase | pancreas produces maltose; |
| Cholera bacteria produce toxins which increase secretion of chloride ions into the lumen of the intestine. Explain why this results in severe diarrhoea (watery faeces). | 1. Water lost into gut/water moves into gut/ water leaves cells; 2. Low(er) water potential of intestine/gut (lumen); 3. Osmosis/movement down a WP gradient; 4. Less/not enough water (re)absorbed; |
| Scientists investigated how effective two oral rehydration solutions, A and B, were in treating patients with diarrhoea caused by cholera. Solution A contained glucose. Solution B was identical to A, except that glucose was replaced by starch. | |
| The water potential of solution B was higher (less negative) than the water potential of solution A. Explain why. | Starch is not (very) soluble/does not dissolve well |
| The enzyme tyrosine kinase (TK) is found in human cells. TK can exist in a non-functional and a functional form. The functional form of TK is only produced when a phosphate group is added to non-functional TK Explain . | 1. (Phosphate) changes shape of TK/changes shape of enzyme/changes the active site; 2. Active site forms/becomes the right shape/can bind to substrate/complementary to substrate/E-S complex can form |
| The binding of the functional form of TK to its substrate leads to cell division. Chronic myeloid leukaemia is a cancer caused by a faulty form of TK. Cancer involves uncontrolled cell division.Suggest how faulty TK leads to chronic myeloid leukaemia | 1 . Faulty TK has functional active site without phosphate; 2. (So, faulty) TK functional all the time/TK not controlled (by phosphate) |
| Imatinib is a drug used to treat chronic myeloid leukaemia. Imatinib inhibits faulty TK. Using all of the information, describe how imatinib stops the development of chronic myeloid leukaemia. . | 1. Non-competitive inhibitor/binds to site other than active site; 2. Causes TK to be in non- functional form/active site not formed/wrong shape/E-S complex not formed; 3. So, (uncontrolled) cell division stopped/slowed/controlled |
| Some people have a form of heart failure where their heart is not pumping blood as well as it used to. Some people with heart failure are given an artificial heart to improve circulation of blood from the left ventricle. | diagram |
| Name the blood vessel to which the artificial heart is connected. | aorta |
| In these patients, the right ventricle still produces sufficient blood flow to keep the patient alive. Suggest why the left ventricle requires the help of the artificial heart but the right ventricle does not. | 1. Left ventricle pumps to whole body (except lungs)/pumps blood further; 2. Left ventricle does most work/produces a greater pressure/produces a greater force |
| Diagram hows the internal structure of this type of artificial heart. Valves A and B have the same functions as heart valves involved in the cardiac cycle. Name the heart valve that has the same function as: valve A valve B | 1. (Valve A) atrioventricular valve; 2. Semi-lunar valve; |
| There are different designs of artificial heart. Doctors compared results for patients who received two different types of artificial heart, X and Y. Which type of artificial heart was the more successful? Use calculations to support your answer. | Table X because (no mark) 1. 52.1% survived without replacement compared to 12.1% / 2. 10.9% required repair or replacement compared to 41.4% 3. 37% died compared to 46.6%; OR (X/Y = 119 divided by 58 = 2.05) 14.4; 49.2; 55.4; |
| Explain what white coat hypertension is | Some people develop a higher than normal heart rate and blood pressure when they are in a doctor’s surgery. High heart rate is correlated with high blood pressure. |
| Doctors investigated difference between men with & without whitecoathypertension. Mean heart rates measured could be measured under the following conditions... | in the doctor’s surgery, by recording the pulse in the wrist for 1 minute, lying down at home, using a portable heart rate monitor when walking around at home, using a portable heart rate monitor when sleeping. |
| Explain why the pulse recordings in the doctor’s surgery were taken when the men were lying down | Patients were at rest/not moving/not using muscles/in standardised position/controlled conditions; |
| The groups of men selected for this investigation into white coat hypertension were matched. Other than being men, suggest one factor for which they should have been matched. | One suitable factor; E.g. Age/no heart condition/not on medication |
| The pulse felt in the artery in the wrist can be recorded and used to measure heart rate. Suggest why the pulse felt can be used to measure heart rate. | 1. Caused by pressure/surge of blood; 2. From (one) contraction/beat of (left) ventricle/heart; |
| The portable heart rate monitor recorded the men’s heart rates continuously. This gave more reliable mean heart rates than those obtained by recording the pulse in the wrist for 1 minute. Suggest why it is more reliable | Records HR over long period of time/more data Anomalies-less effect PR for one minute only may give an anomalous/atypical result; Errors when counting PR 1 min/human error; Monitor records HR over a range of activities/PR for 1set of conditions |
| A journalist, who saw these results, stated that they showed there is no such thing as white-coat hypertension. Do these data support this statement? Give reasons for your answer. | Men with conditions have higher HR No direct measurements of BP Only one investigation/need more studies; Using different recording methods/conditions (in each case so cannot compare results); Men without condition also have higher HR in surgery; |
| Why do people with HIV eventually die? | The human immunodeficiency virus (HIV) leads to the development of acquired immunodeficiency syndrome (AIDS). Eventually, people with AIDS die because they are unable to produce an immune response to pathogens. |
| Why is it difficult to develop a vaccine against HIV? | SHIV rapidly enters host cells. HIV causes the death of T cells that activate B cells. HIV shows a lot of antigenic variability. |
| Name 3 types of HIV vaccine | 1 HIV in an inactivated form 2 attenuated HIV which replicates in the body but does not kill host cells. 3 uses a different, non-pathogenic virus to carry genetic information from HIV into the person’s cells so person’s cells produce HIV proteins. |
| Why are not doctors using HIV vaccines to protect people in a mass vaccination programme? | Inactive virus may become active/viral transformation; Attenuated virus might become harmful; Non-pathogenic virus may mutate and harm cells; Genetic info/protein may harm cells; May become/test positive after vaccine ; May affect their work/life; |
| People with AIDS die because they are unable to produce an immune response to pathogens. Explain why this leads to death. | 1. Infected by/susceptible to (other) pathogen(s)/named disease caused by a pathogen (from environment); 2. Pathogen(s) reproduce/cause diease (in host); 3. Damage cells/tissues/organs; 4. Release toxins |
| Explain why each of the following means that a vaccine might not be effective against HIV. HIV rapidly enters host cells | enters cellsbefore antibodies can bind to/destroy it; Antibodies cannot enter cells stay in blood; OR enters cells) before (secondary) immune response caused/before memory cells have time to respond So no antibodies present (to attack HIV); OR |
| Explain why each of the following means that a vaccine might not be effective against HIV. HIV shows a lot of antigenic variability | Antigen changes; (Specific) antibody/receptor no longer binds to (new) antigen; OR |
| Explain why each of the following means that a vaccine might not be effective against HIV. HIV rapidly enters host cells | 5. Vaccine taken up too quickly to cause immune response; 6. So no antibodies/memory cells formed; |
| Explain why each of the following means that a vaccine might not be effective against HIV. HIV shows a lot of antigenic variability | OR Many different strains of HIV/many antigens present on HIV; Not possible to make a vaccine for all antigens/vaccine may not stimulate an antibody for a particular antigen; |
| Some substances can cross the cell-surface membrane of a cell by simple diffusion through the phospholipid bilayer. Describe Osmosis | 1. From a high water potential to a low water potential/down a water potential gradient; 2. Through aquaporins/water channels; |
| Some substances can cross the cell-surface membrane of a cell by simple diffusion through the phospholipid bilayer. Describe facilitated diffusion | Channel/carrier protein; Down concentration gradient; |
| Some substances can cross the cell-surface membrane of a cell by simple diffusion through the phospholipid bilayer. Describe active transport | Carrier protein/protein pumps; Against concentration gradient; Using ATP/energy (from respiration); |
| Some substances can cross the cell-surface membrane of a cell by simple diffusion through the phospholipid bilayer. Describe phagocytosis/endocytosis | Engulfing by cell surface membrane to form vesicle/vacuole |
| List types of diffusion | Osmosis Facilitated diffusion Active transport Phagocytosis/endocytosis exocytosis/role of Golgi vesicles |
| Some substances can cross the cell-surface membrane of a cell by simple diffusion through the phospholipid bilayer. Describe exocytosis/role of Golgi vesicles | Fusion of vesicle with cell surface membrane; |
| Name two other structures which show that the amoeba is a eukaryotic cell. | 1. Nucleus; 2. Mitochondrion; 3. Endoplasmic reticulum/ER; 4. Lysosome; |
| The scientists used a transmission electron microscope to study the structure of the amoeba. Explain why. | 1. High/ better resolution; 2. Shorter wavelength; 3. To see internal structures/ organelles/named organelles; |
| Scientists studied results of an investigations into the effect of drinking different amounts of alcohol on the risk of developing heart disease. The volunteers were aged between 40 and 50. Explain how this improved this investigation. | Age affects heart disease / age affects how alcohol affects the body; |
| Describe how oxygen in air in the alveoli enters the blood in capillaries | 1. Diffusion; 2. Across (alveoli)epithelium/ (capillary) endothelium; |
| Air moves into the lungs between times P and Q. Explain how the diaphragm causes this. | 1. Diaphragm contracts/moves down/ flattens; 2. Increases volume (of thorax); 3. Decrease in pressure; 4. Air moves from high to lower pressure/down pressure gradient; |
| What is a pathogen? | (Micro)organism that causes disease / harm to body / an immune response; |
| When a pathogen enters the body it may be destroyed by phagocytosis. Describe how. | Phagocyte attracted by a substance/ recognises (foreign) antigen; Pathogenengulfed/ ingested; Enclosed in vacuole/ vesicle/ phagosome; (Vacuole) fuses/joins with lysosome; Lysosome contains enzymes; Pathogen digested/ molecules hydrolysed |
| When a pathogen causes an infection, plasma cells secrete antibodies which destroy this pathogen. Explain why these antibodies are only effective against a specific pathogen | 1. AG are a specific shape/have specific tertiary/3D structure; 2. AB fits/binds/is complementary to AG OR vv |
| What is gluten? | Gluten is a protein found in wheat. When gluten is digested in the small intestine, the products include peptides. Peptides are short chains of amino acids. These peptides cannot be absorbed by facilitated diffusion and leave the gut in faeces |
| Describe how the student would show that reducing sugars were present in a solution. ............................................................................................................................... | 1. Add Benedict’s; 2. Heat; 3. Red/orange/yellow/green (shows reducing sugar present); |
| What happens to peptides from gluten in a healthy person | When gluten is digested in the small intestine, the products include peptides. Peptides are short chains of amino acids. These peptides cannot be absorbed by facilitated diffusion and leave the gut in faeces |
| What is coeliac disease | Epithelial cells do not absorb the products of digestion very well, some of the gluten peptides can can pass between these cells and enter the intestine wall. cause an immune response that leads to the destruction of microvilli on the cells. |
| Name the type of chemical reaction which produces amino acids from proteins. | Hydrolysis (reaction); |
| The peptides released when gluten is digested cannot be absorbed by facilitated diffusion (lines 2 – 3). Suggest why. | 1. Too big/ wrong shape; 2. To fit/ bind/ pass through (membrane/ into cell/through carrier/ channel protein); 3. Carrier / channel protein; |
| The epithelial cells of people with coeliac disease do not absorb the products of digestion very well (lines 4 – 5). Explain why. | 1. Villi /microvilli damaged/ destroyed; 2. Reduced surface area ; 3. For (facilitated) diffusion/ active transport; |
| Explain why the peptides cause an immune response | Foreign/(act as) antigen /non-self; |
| Scientists have carried out trials of a drug to treat coeliac disease (lines 10 – 11). Suggest two factors that should be considered before the drug can be used on patients with the disease | 1. Dose to be given; 2. No (serious) side effects; 3. How effective; 4. Cost of drug; |
| The heart controls and coordinates the regular contraction of the atria A and ventricles V. Describe how. | SAN → AVN → bundle of His/Purkyne fibres; Impulses/ lectrical activity (over A); A contract; Non-conducting tissue (between A and Vs); Delay (at AVN) ensures A empty/ ventricles fill before Vs contract; Ventricles contract from apex upwards; |
| The diet of a person can increase the risk of coronary heart disease. Explain how. | Too much saturated fat/cholesterol LDL/cholesterol in blood u Atheroma/fatty deposits/plaques in artery wall Diameter /blocks coronary arteries down Less oxygen/glucose to heart muscle/tissue/cells; BP up Risk of clot /thrombosis/embolism/aneurysm u |
| Name the type of reaction that joins monosaccharides together | Condensation (reaction); |
| Some cells lining the bronchi of the lungs secrete large amounts of mucus. Mucus contains protein. Name one organelle that you would expect to find in large numbers in a mucus-secreting cell and describe its role in the production of mucus. | Golgi (apparatus); Package/process proteins; OR Rough endoplasmic reticulum/ribosomes; Make polypeptide/protein/forming peptide bonds; OR Mitochondria; Release of energy/make ATP; OR Vesicles; Secretion/transport of protein; |
| An enzyme catalyses only one reaction. Explain why. | 1. (Enzyme has) active site; 2. Only substrate fits (the active site); |
| Name the process by which oxygen passes from an alveolus in the lungs into the blood. | (Simple) diffusion; |
| Describe two adaptations of the structure of alveoli for efficient gas exchange | 1. Thin walls/cells; 2. (Total) surface area is large; |
| Fire-breathers create a ball of fire by blowing a fine mist of paraffin oil onto a flame. Some of this mist is inhaled and may eventually lead to fibrosis so they cannot breathe out properly. Explain why. | 1. Loss of elasticity/elastic tissue; 2. Scar tissue; 3. Less recoil; |
| Infection by the cholera bacterium can cause acute diarrhoea. Explain how. | 1. Toxin (produced by bacterium) causes (chloride) ions to move into (lumen of) intestine; 2. Water potential (of iby osmosis into intestine/out of cells; |
| In areas where there are repeated outbreaks of cholera, most people who become infected by cholera Bacteria do not become ill. Suggest and explain one reason why. VaccinationCell | Previous infection/V produced memory Cs Different forms of B don't produce much/any toxins Few B ingested so not enough toxin to produce symptoms; Naturally resistant becuase of structure of C membranes/amount of secretions eg bile/pancreatic juices |
| Describe how you would test a sample of food for the presence of starch | 1. Add iodine/potassium iodide solution to the food sample; 2. Blue/black/purple indicates starch is present; |
| The concentration of glucose in the blood rises after eating a meal containing carbohydrates. The rise is slower if the carbohydrate is starch rather than sucrose. Explain why. | 1. Starch digested to maltose/by amylase; 2. Maltose digested to glucose/by maltase; 3. Digestion of sucrose is a single step/only one enzyme/sucrase; |
| What is Glycaemic Load? | The glycaemic load (GL) of a diet is a measure of how much digestible carbohydrate it contains |
| What effects does a high GL have? | The higher the GL of a diet the more quickly it raises the blood glucose concentration after a meal. A diet with a high GL also increases the concentration of harmful lipids in the blood. |
| Give two adaptations that other epithelial cells have for the absorption of food. | 1. Microvilli; 2. Carrier proteins/co-transport proteins/membrane-bound enzymes; 3. Many mitochondria; |
| What is an antigen? | Substance that causes an immune response/production of antibodies; |
| Describe how a heartbeat is initiated and coordinated. Atria Ventricle ImPulse Contract Electrical Activity Pressure | SAN sends wave of EA/IPs across A causing Al Cion; Nonconducting tissue prevents immediate Cion of Vs/prevents IPs reaching the Vs; AVN delays IP whilst blood leaves A/Vs fill; AVN sends wave of EP/IPs down Bundle of His; Causing Vs to C from base up |
| Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta. Atria Ventricle Contract Pressure v=valve Semilunar-SL Higher | Atrium H P than V due to filling/Cion AtrioVicular v opens V has higher P than atrium due to filling/Cion AtrioVricular v closes V H P than aorta SLv opens; H P in aorta than V as heart relaxes SLv closes; Muscle/Al/Vicular) Cion increases P; |
| Some people cannot digest lactose when they are adult. They could digest lactose when they were children. Use your knowledge of water potential to explain why these adults get diarrhoea when they drink milk. | Low(er) water potential in lumen / intestine / gut; Water enters lumen / leaves (body) cells / by osmosis |
| Describe how you could use the biuret test to distinguish a solution of the enzyme, lactase from a solution of lactose | (Add Biuret reagent to both solutions) – no mark; Lactase / enzyme will give purple / lilac / mauve; OR Lactose / reducing sugar will not give purple / lilac / mauve / will remain blue; |
| Describe the path by which oxygen goes from an alveolus to the blood | Through alveolar epithelium; Through capillary epithelium/endothelium; |
| In healthy lungs, a gradient is maintained between the concentration of O in the alveoli and the concentration of O in the lung capillaries. Describe how ventilation helps to maintain this difference in O concentration. Give one other way that helps | (In alveolus) Brings in air containing a high(er) oxygen concentration; Removes air with a low(er) oxygen concentration Circulation of blood / moving blood; |
| Methotrexate is a drug used in the treatment of cancer. It is a competitive inhibitor and affects the enzyme folate reductase. Explain how the drug lowers the rate of reaction controlled by folate reductase. | Methotrexate / drug is a similar shape / structure to substrate; Binds to / fits / is complementary to active site; Less substrate binds / less enzyme-substrate complexes formed; |
| Methotrexate only affects the rate of the reaction controlled by folate reductase. Explain why this drug does not affect other enzymes. | Methotrexate / drug is only similar shape to specific substrate / only fits this active site; OR Methotrexate / drug is a different shape to other substrates / will not fit other active sites; |
| Although people with coeliac disease can digest proteins they have low concentrations of amino acids in their blood. Explain why they have low concentrations of amino acids in their blood. | Reduced surface area so less absorption Membrane-bound enzymes less effective (So) proteins / polypeptides not digested; Cell membranes damaged so fewer/less effective carrier/channel proteins Carrier/channel proteins damaged so less absorption; |
| The students gave their results as a ratio. What is the advantage of giving the results as a ratio? | Allows comparison / shows proportional change; Idea that discs had different starting masses / weights; |
| The students were advised that they could improve their graph by taking additional readings. Explain how. | Line / curve of best fit is more reliable / precise; Intercept / point where line crosses axis is more reliable / precise; OR Can plot SD values / error bars; To show variability about the mean / how spread out the results are |
| List types of pathogen. | bacteria Virus / fungus / protozoan; |
| Give two ways in which a pathogen may cause disease when it has entered the body | Produces toxins; Damages cells / tissues / example given e.g. cell lysis |
| Some new tests use monoclonal antibodies.Explain why these antibodies are referred to as monoclonal. | (Antibodies) produced from a single clone of B cells / plasma cells; OR (Antibodies) produced from the same B cell / plasma cell; |
| Some new tests use monoclonal antibodies. Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why. | (Specific) primary structure / order of amino acids; (Specific) tertiary / 3D structure; (So) Only binds to / fits / complementary to one antigen |
| The tests using monoclonal antibodies allow vets to identify brucellosis while they are still on a farm. Explain the advantages of this. | (Rapid) treatment of carriers / infected cattle / disease; Can isolate / cull carriers / infected cattle; Infected (dairy) products not sold / consumed / tracked; Reduces spread of disease; No need to kill / prevents the death of non-infected animals |
| The cardiac cycle is controlled by the sinoatrial node (SAN) and the atrioventricular node (AVN). Describe how. Atria Electrical activity ImPulse Contract Wave Bundle of His Purkyne fibres | SAN initiates HB/acts as pacemaker/myogenic SAN sends W of EA/IPs (across A) causing Al Cion AVN delays EA/IPs Allows A to empty before Vs C/Vs to fill before they C AVN sends W of EA/IPs down BoH/PF Causing Vs to C from base up)Vcular systole; |
| What is atheroma and how may it cause myocardial infarction Heart Blood Artery Cell Muscle Tissue | Cholesterol/plaque/lipoprotein/LDL/fatty material/Cs In A wall/under lining/endothelium of A/Bvessel Atheroma link to B clot/thrombosis; Blocks coronary A/A supplying H M/tT/Cs Reduces O/glucose supply to H M/T/Cs H M/T/Cs can't respire/dies |
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catherinesturt