Topic 1 Three Star LOs 2024 Biology Past Paper PDF

1.8)Describe, with the aid of a diagram, the structure of a water molecule illustrating hydrogen bonding A water molecule has: 1) One Oxygen atom (shaded/red circles) 2) Two Hydrogen atoms (white circles) 3) The Oxygen atom has a slightly negative charge 4) The Hydrogen atoms have a sli...

1.8)Describe, with the aid of a diagram, the structure of a water molecule illustrating hydrogen bonding A water molecule has: 1) One Oxygen atom (shaded/red circles) 2) Two Hydrogen atoms (white circles) 3) The Oxygen atom has a slightly negative charge 4) The Hydrogen atoms have a slightly positive charge 5) Hydrogen bonds between molecules form between oxygen and hydrogen atoms 1.10)List the structures of arteries, veins and capillaries and relate these to their function Arteries: Have a relatively thick wall to cope with the high pressure blood in the lumen. Smooth muscle tissue which can contract to narrow the lumen and reduce blood flow to an area or relax to increase the blood flow to an area. Elastic tissue which allows the artery to stretch during systole and recoil during diastole to even out changes in pressure and maintain pressure during diastole. Veins: Have a relatively thin wall as they don’t have to cope with high pressure blood. They have valves to prevent the backflow of blood. Smooth muscle which contracts to maintain pressure. Both arteries and veins: Have an outer coat of connective tissue containing collagen to protect the blood vessels from physical damage within the body (it makes them strong and durable). The endothelium is very smooth to minimise friction and so maximise the efficiency of blood flow. Capillaries: Are the exchange surface of the circulatory system and have a wall that is only a single layer of thin cells to minimise the distance for diffusion and allow molecules to diffuse quickly into or out of the blood. The lumen of a capillary is just smaller than the diameter of a red blood cell so RBCs have to slow down to squeeze through the capillaries (giving more time for diffusion of oxygen to occur in to the tissues or into the blood from the lungs). 1.11)Label and annotate diagrams of the heart, both internal and external views The blood vessels over the surface of the heart are the coronary arteries which supply the heart muscle with blood. 1.14, 1.15)Describe the sequence of events in the cardiac cycle. Name the stages and describe pressure changes, opening and closing of valves and direction of blood flow through chambers Atrial systole Muscles in walls of atria contract Pressure in atria is above pressure in ventricles so the atrioventricular valves open Blood flows from the atria to the ventricles Ventricular systole Muscles in walls of ventricles contract Pressure in ventricles rises above pressure in atria so the atrioventricular valves close Pressure in ventricles rises above pressure in arteries so the semilunar valves open Blood flows from the ventricles to the arteries Cardiac diastole Muscles in the walls of the atria and the ventricles are relaxed Pressure in the ventricles drops below the pressure in the arteries so the semilunar valves close Blood returning to the heart flows under low pressure into the atria Pressure in the ventricles drops below the pressure in the atria so the atrioventricular valves open 1.21)List the sequence of events leading to atherosclerosis 1) Damage to the endothelium / wall of arteries 2) Causes an inflammatory response 3) White blood cells move into the artery wall 4) These white blood cells accumulate cholesterol 5) This accumulation of cholesterol is called an atheroma 6) Calcium salts and fibrous tissue build up forming a plaque – this is atherosclerosis 7) Atherosclerosis narrows the lumen of the artery and makes the artery walls less elastic 8) A narrower lumen and less elastic walls means that a higher blood pressure is needed to pump the blood around the body 9) This higher blood pressure means that further damage to artery walls is likely – positive feedback. 1.23) List the sequence of events that leads to the formation of a thrombus (blood clot) 1) Platelets come into contact with collagen in artery wall 2) Platelets change shape, stick to the damaged area and each other forming a platelet plug 3) Platelets and damaged tissue release thromboplastin 4) In the presence of calcium ions and Vitamin K 5) Thromboplastin catalyses the conversion of prothrombin into an enzyme called thrombin 6) Thrombin catalyses the conversion of fibrinogen into fibrin 7) Fibrin is insoluble in water and forms a mesh over the damaged area 8) This mesh traps red blood cells, forming a blood clot 1.31)List at least 6 factors that increase the risk of cardiovascular disease 1.32)Classify the risk factors into controllable or uncontrollable groups 1.37) List the aspects of diet that can lead to CVD Controllable risk factors Uncontrollable risk factors Smoking Age – getting older Excessive alcohol consumption Gender – being male Obesity Genetics – a family history Lack of exercise of CVD High blood cholesterol levels Also: High blood pressure Diabetes (type 1) Dietary factors: High Salt diet High saturated fat diet High cholesterol diet High calorie diet Low levels of antioxidants in diet 1.34)Explain how high blood pressure can lead to CVD and myocardial infarction 1. High blood pressure can cause damage to the endothelium/artery walls 2. Damage to artery walls can lead to atherosclerosis 3. Atherosclerosis leads to narrowing of the lumen of arteries and reduced elasticity of artery walls by formation of plaques 4. Rupture of these plaques in artery walls can lead to blood clots forming which can further narrow the artery or break off and block other blood vessels 5. If coronary arteries are blocked (or become too narrow) by atherosclerosis or a blood clot then the blood supply to some of the heart muscle will stop 6. Without a supply of blood the heart muscle doesn’t receive the oxygen and glucose it needs 7. This means the cells cannot respire aerobically 8. And so the muscle cells cannot contract 9. Without all the heart muscle cells able to contract the heart cannot beat properly 10.This is a heart attack or myocardial infarction 11.A person will have a stroke if the same thing happens in arteries in the brain 1.39) List 3 examples of monosaccharides and disaccharides Monosaccharides glucose, fructose, galactose Disaccharides maltose (glucose + glucose) lactose (glucose + galactose) sucrose (glucose + fructose) Note: all of these sugars are sweet and soluble 1.40) List 2 examples of polysaccharides Many monosaccharides linked together form a polymer called a polysaccharide Examples: starch cellulose glycogen 1.41)Draw a molecule of glucose  O H H HO OH Detailed diagram of Glucose Simplified diagram of Glucose 1.42)Draw a labelled diagram demonstrating how 2 molecules of glucose form a disaccharide in a condensation reaction, showing the location of a 1,4-glycosidic link and from where a water molecule is generated 1.44)Describe using a diagram how hydrolysis of maltose occurs and why water is needed Glycosidic bonds are given numbers (e.g. 1,4) after the carbon numbers that are joined. Water is produced by removing an OH group from one glucose and a Hydrogen from an OH group of the other glucose 1.45)Name the two different polysaccharides that make up starch Amylose and amylopectin 1.46)Draw a table to compare and contrast amylose, amylopectin and glycogen  Glycogen Amylose Amylopectin Found in? Animals Plants Plants Function? Glucose/energy Glucose/energy Glucose/energy store store store Made of which Glucose Glucose Glucose monomer? Branches? Yes – many No Yes – a few 1,4 glycosidic Yes Yes Yes links? 1,6 glycosidic Yes No Yes links? Soluble in water? No No No 1.47)Explain with the use of diagrams why glycosidic bonds are called 1,4 or 1,6 glycosidic bond  If the glycosidic bonds link the carbon 1 of one molecule to the carbon 4 of another molecule they are called 1-4 glycosidic bonds. 1,4 glycosidic bond If they link the carbon 1 of one molecule with the carbon 6 of another then they are called 1-6 glycosidic bonds. 1,6 glycosidic bond 1,4 glycosidic bond 1.48)List 4 reasons why polysaccharides are considered good energy storage molecules with reference to their solubility, size, bonding and presence of side-chains 1) They are compact molecules so lots of glucose can be stored in a small volume (i.e. in one cell). 2) They are coiled (particularly amylose) which makes them compact. 3) They are insoluble in water and so don’t affect the concentration of water in the cytoplasm and so do not affect movement of water into or out of the cell by osmosis. 4) They are made of glucose and so can be hydrolysed to release glucose for respiration. 5) They are branched (amylopectin and glycogen) and so can release glucose quickly. 1.49)Describe, using a labelled diagram, the basic structure of a triglyceride 1.50)Describe with the aid of a diagram, how a triglyceride is formed and broken down with reference to the terms, ‘condensation’ and ‘hydrolysis’, noting where an ester bond is formed When a triglyceride is formed 3 water molecules are released. Hydrolysis reactions are the reverse of condensation reactions and so add in 3 water molecules to break up a triglyceride into a glycerol molecule and 3 fatty acids. 1.51)Explain in a sentence and draw a diagram to illustrate differences between monounsaturated, polyunsaturated and saturated lipids Saturated lipids/triglycerides contain fatty acids with the maximum number of hydrogen atoms, all carbon to carbon bonds are single bonds. In monounsaturated lipids the fatty acids each contain one carbon to carbon double bond and in polyunsaturated lipids the fatty acids contain two or more carbon to carbon double bonds. A saturated fatty acid A monounsaturated fatty acid Core practical: 1.67) Describe a safe, reliable method for investigating the Vitamin C content of food and drink 1) Make sure both fruits have been kept for the same length of time under the same conditions 2) Blend a known, constant mass of each fruit (in a known, constant quantity of water if necessary) and analyse the juice 3) Use DCPIP 4) DCPIP turns from blue to colourless in the presence of vitamin C 5) Add juice drop by drop into 1cm3 of 1% DCPIP solution and record the volume needed to turn the DCPIP colourless 6) Swirl the DCPIP solution after each drop 7) Repeat for the other fruit keeping everything else the same 8) Repeat 10 times for each fruit 9) Maintain a constant temperature throughout all repeats (20°C) 10)Compare values for each fruit to a value determined with a known concentration of Vitamin C in order to work out how much vitamin C was in each fruit. Core practical : 1.70) Describe a safe, reliable method for measuring the effect of caffeine on the heart rate of Daphnia 1) Put Daphnia on a dimpled slide in a drop of pond water 2) Use a small amount of cotton wool to prevent Daphnia moving around 3) View Daphnia under a microscope 4) Allow time for Daphnia to acclimatise 5) Determine heart rate before adding caffeine (beats per minute) – you can make a dot with a pen on a piece of paper for each beat and then count the dots or use a clicker-counter. 6) Add caffeine (this is likely to be specific to the context of the exam question) and measure heart rate again 7) Repeat 10 times 8) Keep temperature constant by using a heat sink (tray of water) between the microscope lamp and the Daphnia 9) Compare results to the same experiment (keep everything else the same) but just adding more pond water as a placebo 10)Design the experiment so that the person measuring the heart rate doesn’t know whether caffeine or just pond water was added – a blind experiment.