AS Human Biology ISA Flashcards

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What is the function of carbohydrates?
Provide energy.
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What is the function of fats?
Acts as an energy store, provide insulation, make up cell membranes, physically protect organs.
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What is the function of proteins?
Needed for growth, repair of tissues and to make enzymes. Excess protein used as energy.
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What is the function of vitamins?
Different vitamins have different functions, e.g. vitamin D is need for calcium absorption, vitamin K is needed for blood clotting.
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What is the function of mineral salts?
Different mineral salts have different functions, e.g. iron is needed to make haemoglobin in the blood, calcium is needed for bone formation.
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Why are we advised to eat plenty of fruit and vegetables?
They're a good source of vitamins, minerals and fibre, which are essential in a healthy diet. Help maintain a healthy body weight and reduce the risk of heart disease and some types of cancers.
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Why are we advised to eat less salt and fat?
Lowers blood pressure and reduce the risk of heart disease and stroke. Eating too much saturated fat can increase the amount of cholesterol which increases risk of heart disease.
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What is Glycaemic Index (GI)?
Measure of how quickly the carbohydrates in different foods raise our blood sugar level after eating.
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Describe High GI?
Carbohydrates in foods with a high GI break down and absorbed quickly - our blood glucose level rises rapidly after eating.
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Describe Low GI?
Crabohydrates in foods with a low GI break down and absorbed slowly - our blood glucose level rises gradually.
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What is the link between endurance athletes and GI?
Endurance athletes often eat foods with a low GI before a competition, to give them energy throughout the competition. Then they eat foods with a high GI afterwards to give them a quick energy boost.
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What are isotonic sports drinks?
Drinks that quickly replace glucose, electrolytes and water used by during exercise. Isotonic drinks have the same water potential as blood plasma. They have a high GI - the glucose they contain doesn't need to be digested, so it's absorbed quickly.
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What is Glycaemic Load (GL)?
Takes into account the amount of carbohydrates in an average portion of food. GL = Carbohydrate content x (GI ÷ 100)
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What are gut bacteria?
Bacteria that live in the digestive system. They're found in large numbers in the colon.
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Describe the role of gut bacteria?
They help the body to break down some types of indigestable carbohydrates, releasing extra nutrients. Prevent growth of harmful bacteria by competing with them. Some produce vitamin K, which is important for blood clotting.
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What is obesity?
Common medical problem. People gain body weight when they eat more calories than they can work off. People said to be obese if they have a BMI over 30 and so much body fat that it causes health problems. It can increase the risk of diseases.
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What is diabetes?
Condition where the body can't regulate the amount of glucose in the blood properly. Usually because of a lack of the hormone insulin which regulates our blood glucose level.
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Describe type 1 diabetes?
Body can't produce enough insulin
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Describe type 2 diabetes?
Insulin that's produced doesn't work well - cells become resistant to insulin.
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What is fat composed of?
Most fats are composed of one molecule of glycerol and three fatty acid molecules attached to it. These fats are known as triglycerides.
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What are polymers?
Polymers are made by joining together lots of smaller molecules called monomers, e.g. monosaccharides join together to form carbohydrates (polysaccharide) and amino acids join together to form proteins.
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What is a condensation reaction?
A condensation reaction is a where a bond forms between two monomers and a molecule of water is released.
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Explain how polysaccharides are formed?
Single sugar molecules are called monosaccharides, and when two of these join together, a disaccharide is formed. When more than two monosaccharides join together, a polysaccharide is formed.
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Give examples of all the different types of molecules formed when glucose link together?
Glucose is an example of a monosaccharide. Maltose is a disaccharide formed from two glucose molecules. Starch/Glycogen/Cellulose is a polysaccharide made from many glucose molecules.
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How are proteins made?
Amino acids are the monomers of proteins. A dipeptide is formed when two amino acids join together. A polypeptide is formed when more than two amino acids join together. Proteins are made up of one or more polypeptides.
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What is the primary structure of a protein?
This is the sequence of amino acids in the polypeptide chain.
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What is the secondary structure of a protein?
Hydrogen bonds form between amino acids in the chain making an alpha helix or beta pleated sheet.
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What is the tertiary structure of a protein?
Amino acids often become coiled and folded further. More bonds form between different parts of the polypeptide chain. The tertiary structure is the overall 3D shape of the protein.
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What bonds hold the tertiary structure of a protein in place?
Hydrogen bonds, ionic bonds and disulphide bridges (bond between two sulphur atoms).
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Describe the process of digestion of food?
Food is broken down into smaller molecules. Large biological molecules (e.g. polymers) in food are insoluble. During digestion, they are broken down into smaller molecules, which are soluble and easily absorbed.
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What is a hydrolysis reaction?
Breaking down molecules into smaller molecules, by adding water to break bonds.
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Give example of hydrolysis reactions?
Fats are broken down into fatty acids, and glycerol. Carbohydrates are broken down into monosaccharides and proteins are broken down into amino acids.
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Describe the use digestive enzymes?
Digestive enzymes speed up the hydrolysis of fats, carbohydrates and proteins. They have a specific shape that allows large biological molecules to bind to the enzyme, providing a site for them to react with water.
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Give examples of digestive enzymes?
Protease speed u p the digestion of proteins, carbohydrases speed up the digestion of carbohydrates, and lipases speed up the digestion of fats.
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Physiological conditions in the gut?
Body temperature is 37℃ - warm enough for digestive enzymes to work quickly. Liver produces bile - neutralises stomach acid and creates alkaline conditions in the s intestine. Stomach produces hydrochloric acid - which creates acidic conditions.
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What is chromatography?
Chromatography separates out components in a mixture.
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How is chromatography performed?
Pencil line across some chromatography paper, put a spot of test solution onto the point of origin. Put paper in solvent making sure baseline stays above solvent. Different chemicals move at different rates.
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How is the Rf value of a chemical calculated?
Rf value = distance travelled by spot ÷ distance travelled by solvent
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What is an enzyme?
Enzymes are biological catalysts, which speed up chemical reactions. They catalyse metabolic reactions. Enzymes are proteins
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What is the structure of an enzyme?
Enzymes have an active site, which has a specific shape. The active site is the part of the enzyme where the substrate molecules bind to. For the enzyme to work, the substrate has to fit the active site complementary. Enzymes are highly specific.
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How to enzymes speed up the rate of reaction?
Enzymes reduce the activation energy needed, often making reactions happen at a lower temperature. This speeds up the rate of reaction. When the substrate binds to the active site, an enzyme-substrate complex is formed.
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Explain the 'induced fit' model of enzyme activity?
It states that the substrate doesn't only have to be the right shape to fit the active site, it has to make the active site change shape.
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What is the effect of temperature on enzyme activity?
The rate of reaction increases when the temperature increases, as more heat means more kinetic energy, so molecules move faster, which makes the enzyme more likely to collide with the substrate molecules.
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How can temperature cause enzyme activity to decrease?
if the temperature goes above the optimum temperature, the vibration breaks some of the bonds that hold the enzyme in shape so the active site changes shape and the enzyme-substrate complex can no longer form. The enzyme is denatured.
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What is the effect of pH on enzyme activity?
All enzymes have an optimum pH value. Above and below the optimum pH can break the ionic and hydrogen bonds that hold the enzyme's tertiary structure, making the enzyme's active site change shape, so the enzyme is denatured.
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What is the effect of substrate concentration on the rate of reaction?
Higher the substrate concentration, the faster the reaction. Up to the saturation point, after that, all the enzymes active sites are full, so adding more will not make a difference.
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Explain why our bodies can digest starch but not cellulose?
Starch and cellulose are different types of carbohydrates. Our bodies produce amylase, which speeds up the digestion of starch. Because cellulose doesn't fit into the active site of amylase, we can't breakdown cellulose.
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Describe lactose intolerance?
Is caused by the lack of the enzyme, lactase found in the intestines. If you don't have enough lactase, you can't breakdown the milk sugar lactose which causes the condition.
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What are the effects of lactose intolerance?
Undigested lactose is fermented by bacteria that can cause intestinal complaints such as stomach cramps, flatulence and diarrhoea.
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How is lactose intolerance treated?
Milk can be artificially treated with purified lactase to make it suitable for lactose-intolerance people.
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Which side of the heart carries oxygenated blood?
Left side pumps oxygenated blood to the whole body.
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Why is the left ventricle wall more muscular than the right ventricle wall?
The left ventricle of the heart is thicker, because it needs to contract powerfully to pump blood all around the body. Whereas, the right side only needs to pump blood to the lungs.
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What is the role of the atrioventricular (AV) valves?
They link the atria to the ventricles and stop blood flowing back into the heart when ventricles contract.
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What is the role of semi-lunar (SL) valves?
They link the ventricles to the pulmonary artery and aorta, and stop blood flowing back into the heart after the ventricles have contracted.
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What does 'myogenic' mean?
This means that the heart can contract and relax without receiving signals from nerves.
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Describe the role of the sino-atrial node (SAN)?
This is in the wall of the right atrium. This acts as the pacemaker and sends waves of electrical impulses to the atrial walls causing them to contract at the same time.
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What is the purpose of collagen tissue?
This is a band of non-conductive tissue, that prevents the waves of electrical impulses being passed directly from the atrial to the ventricles.
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Where does the electrical pass to from the SAN?
Atrioventricular node (AVN)
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Why is there a short time delay during the AVN?
After the electrical impulse passes through the bundle of His, there is a short time delay to make sure the ventricles contract after the atria have been completely emptied.
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What is the purpose of the bundle of His?
This is responsible for conducting the electrical activity to the right and left ventricles called the Purkyne fibres, which carry the impulses to the muscular walls causing them to contract.
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What is the cardiac cycle?
The cardiac cycle pumps blood all around the body. The volume of the atria and ventricles change as they contract and relax. Pressure changes also occur.
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Describe what happens during atrial systole?
Ventricles are relaxed. Atrial contract, decreasing the volume of the chamber and increasing the pressure inside. This pushes blood into the ventricles due to the pressure differences.
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Describe what happens during ventricular systole?
The atria relax. Ventricles contract increasing their pressure, pressure becomes ↑ in the ventricles than the atria, which forces AV valves shut to prevent back flow. Pressure in ventricles > aorta and pulmonary artery which forces SL valves open.
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Describe what happens during ventricular diastole?
Ventricles and atria both relax. ↑ pressure in aorta closes the SV valves to prevent back flow into ventricles. Blood returns to the heart and the atria fill with blood again due to a ↑ pressure in the vena cava and pulmonary vein. AV valves open.
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Name three types of blood vessel?
Arteries, veins and capillaries.
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What is the function of arteries?
Carry blood from the heart to the rest of the body.
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What is the structure of an artery?
They're thick walled, muscular and have elastic tissue in the walls to cope with high pressure. The endothelium is folded which allows the artery to expand.
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What is the function of veins?
Take blood back to the heart.
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What is the structure of a vein?
They're wider than arteries, with very little elastic or muscle tissue. Veins contain valves to stop the blood flowing backwards.
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What is the function of capillaries?
This is where metabolic exchange occurs between cells.
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What is the structure of a capillary?
They are the smallest blood vessel. There are a network of capillaries in tissues which increase the surface area, capillary walls are one cell thick, which speeds up diffusion of substances as they have a short diffusion pathway.
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What is tissue fluid?
is the fluid that surrounds cells in tissues.
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What is oedema?
Oedema is a build up of tissue fluid, which occurs when fluid isn't drawn back into the capillaries from the tissues. Excess fluid causes parts of the body to swell.
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What are the main causes of oedema?
High blood pressure can cause a build up of tissue fluid. Tissue fluid formation is increased as more fluid is pushed out of the capillaries.
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Describe how an atheroma forms?
If damage occurs to endothelium, white blood cells and lipids from the blood clump together under the lining and over time form a fibrous tissue called an atheroma. It partially blocks the lumen of the artery and restricts blood flow > Increased BP
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List four cardiovascular diseases that atheromas increase the risk of?
Aneurysm, Thrombosis, Angina and Myocardial Infarction
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Describe what an aneurysm is?
Is a balloon like swelling of the artery. When a atheroma forms, blood can push the inner layers of the artery through the outer elastic layer to form a balloon like swelling. This may burst, causing a haemorrhage.
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Describe what a thrombosis is?
It is the formation of a blood clot. An atheroma can rupture the endothelium of an artery which damages the artery wall leaving a rough surface. Proteins accumulate at the site of damage and form a blood clot, which can cause a complete blockage.
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Describe what an angina is?
It is severe chest pain, when coronary arteries become narrowed, there is a decrease in oxygenated blood to the heart muscle causing severe chest pain.
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Describe what myocardial infarction is?
When the coronary artery becomes completely blocked, an area of the muscle is totally cut off, receiving no oxygen. This causes a heart attack, which can cause damage or death to the heart. Symptoms include chest pain and sweating.
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What is angioplasty?
A deflated balloon is inserted into the narrowed coronary artery and then inflated, which compresses the atheroma plaque and stretches the artery. It improves blood supply to the heart muscle.
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What is coronary by-pass surgery?
Where a bit of healthy blood vessel from another part of the body is used to bypass the narrowed region of the artery - improving the blood supply.
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What is beta-blockers?
Drugs that lower blood pressure by reducing strength of the heartbeat.
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What is deep-vein thrombosis?
Is the formation of a blood clot in a vein deep inside the body, usually happens in the leg. It can be caused by prolonged activity.
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How can the risks of DVT be reduced?
Drugs can be taken to slow blood clotting and by wearing compression stockings to aid circulation.
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Card 2


What is the function of fats?


Acts as an energy store, provide insulation, make up cell membranes, physically protect organs.

Card 3


What is the function of proteins?


Preview of the front of card 3

Card 4


What is the function of vitamins?


Preview of the front of card 4

Card 5


What is the function of mineral salts?


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