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Explain the importance of water as a solvent in transport.
- Water has a dipole nature. This means that the molecules have uneven charges.
- Ions are easily separated in water.
- Hydrogen bonds create cohesion and give water a very high specific heat capacity.
What is the difference between a monosaccharide, disaccharide and polysaccharide?
- Monosaccharides are the simplest form of carbohydrate. They are colourless, soluble, crystalline solids. e.g. Glucose, Fructose. General formula is .Disaccharides are two monosaccharides joined together by condensation reaction. e.g. sucrose, lactose, maltose. General formula is .
- Polysaccharides are long chains of monosaccharides. They can be linear of branched. e.g. starch, glycogen, cellulose.
How do mono and disaccharides join and split?
- Mono and disaccharides join by condensation reactions to form glycosidic bonds. In this reaction a water molecule is released.
- Mono and disaccharides are split by a hydrolysis reaction, where a glycosidic bond is broken. A water molecule is needed.
Explain the structure of amylose, amylopectin, starch and glycogen.
- -An unbranched polysaccharide and forms 1,4 glycosidic bonds.
- -Chains form spirals/coils.
- -Formed of α glucose molecules joined by condensation reactions.
- -It releases energy over a long period of time due to compact structure.
- -Branched + unbranched polysaccharide, made of a glucose.
- -Forms 1,4 & 1,6 glycosidic bonds.
- -Spiral structure with side branches.
- -Broken down easily dues to several terminal glucose molecules.
- -Referred to as 'animal starch', made of a glucose.
- -Many side branches for fast hydrolysis. (1,4 and 1,6 glycosidic bonds.)
- -Compact molecule and supplies energy very fast when needed.
- -Insoluble in water and unreactive - does not affect reactions going on around it, no osmotic effect.
- -Made from amylose and amylopectin.
- -Insoluble, no osmotic effect.
- -Made of a glucose.
How does a triglyceride form? And what is the difference between a saturated and unsaturated lipid?
glycerol + 3 fatty acids = triglyceride
- Low density
- Vital role in cell membranes
Glycerol and fatty acids join by a condensation reaction to form ester bonds
- Saturated lipids are fully saturated with hydrogen. No double bonds, straight molecule.
- Unsaturated lipids have 1+ double bonds. Bent molecule. If 2+ double bonds then polyunsaturated.
Why do animals have a heart and circulation?
- Small S.A. to volume ratio.
- Diffusion is too slow to supply nutrients.
- Needs a mass transport system to supply organism with and glucose.
- Circulation to transport nutrients in blood, heart to pump blood around the body.
Describe the cardiac cycle.
- Atrial systole: The atria contract, atrial pressure rises and blood is pushed from atria into ventricles.
- Ventricular systole: The ventricles contract and ventricular pressure rises above atrial pressure. AV valves close. When ventricular pressure is higher than in arteries, semilunar valves open and blood leaves heart.
- Diastole: Ventricles and atria relax. Semilunar valves close and AV valves open. Blood rushes into atria and ventricles.
How does the structure of the heart relate to its function?
- Walls of left ventricle are thicker due to having to pump blood all around the body - higher pressure.
- Cardiac muscle cells are myogenic - has own intrinsic rhythm.
Daphnia experiment. Ethical issues?
- Ethical issues:
- Daphnia are invertebrates, can't feel pain - is it right to cause them pain though?
- Cant give consent
- Control variables: Temperature, size of daphnia, pH of water
- IV: Caffeine concentrations
- DV: Heart rate
- Have a control daphnia, no ceffeine.
- Then repeat with different caffeine conc.
- Repeat experiment - reliability.
Describe the blood clotting process.
- Platelets are activated by damage in collagen fibres.
- Thromboplastin is released and initiates cascade of events.
- If blood clot is dislodged and is carried around bloodstream it can cause:
- Stroke in the brain
- Blockage of coronary arteries (CHD)
Explain the course of events that leads to atherosclerosis.
- 1. Endothelium is damaged.
- 2. White blood cells (macrophages) move into the damaged area.
- 3. LDL also enters the damaged endothelium and together they form a fatty streak.
- 4. More WBC, LDL and connective tissue build up and harden to form a fibrous plaque - atheroma.
- 5. The larger the plaque, the smaller the lumen becomes - blood pressure increases.
- 6. If plaque bursts, clot can form and block the artery.
Describe the factors that increase the risk of CVD.
- Genetics: Some people can have a genetic predisposition for CVD.
- Diet: Diet high in saturated fats increases cholesterol.
- Alcohol and salt increase blood pressure.
- Age: The older you get, the higher the risk of CVD.
- Gender: Males have a higher chance of getting CVD than females.
- High Blood pressure: Speeds up atheroma formation.
- Damages endothelium.
- Smoking:Nicotine damages endothelium.
- Inactivity: Increases blood pressure.
- Increases LDL levels.
- Heart is not very fit.
What are the benefits and risks of treatments for CVD?
- Antihypertensives can be given in combination.
- Blood pressure can be monitored at home.
- Palpitations, abnormal heart rhythms, fainting, headaches, allergic reactions, depression.
- Plant statins:(reduce LDL)Reduce risk of developing CVDCan reduce absorption of vitamins in gut.
- Can be used on people with existing blood clots.
- Prevent any existing blood clots from growing.
- Cant get rid of existing blood clots.
- Can cause to excessive bleeding - fainting, death.
- Allergic reactions, osteoporosis, swelling of tissue.
- Platelet Inhibitory drugs:
- Can be used on people with existing blood clots.
- Rashes, diarrhoea, nausea, liver problems, excessive bleeding.
What is the relationship between blood cholesterol levels and CVD?
- We can get cholesterol from the liver and our diet.
- High LDL & low HDL = increased risk of CVD
- High HDL & low LDL = decreased risk of CVD
- High cholesterol levels = increased risk of CVD
How is scientific knowledge used to reduce risk of CHD?
Scientists use knowledge about risk factors to help people reduce the risk of getting CHD.
Vitamin C experiment.
- IV: Selected solution
- DV: Vitamin C conc.
- Control variables:
- Volume of DCPIP used
- Person counting drops
- 1. Measure 1cm3 of DCPIP and titrate unknown solution into DCPIP until it turn from blue to colourless.
- 2. Measure volume of solution used.
- 3. More solution used = lower vitamin C conc.
- Less solution used = higher vitamin C conc.
- 4. Mention use of repeats. - reliability.
What happens when there is an energy imbalance?
- BMI is used to measure is you are underweight/normal/overweight.
- Energy in > energy out = weight gain
- Energy in < energy out = weight loss
What is the difference between correlation and causation?
- Correlation: When two variables share a relationship, it being positive or negative.
- A correlation does not show that one variable causes the other.
- Causation: When one variable causes another variable to change.
What makes a study reliable?
- Sample selection: The more varied the sample, the more reliable.
- Sample size: The greater the number of people is a study, the more reliable.
- Variables: The more controlled variables, the more reliable.
- Controls: more controls, more reliable.
- Repetition by other scientists: If same results are produced, study is reliable.
- Data collection: The less bias in data collection, the more reliable. e.g. questionnaires are unreliable.
Why do people underestimate or overestimate risks?
- Risk factors for CVD tend to be underestimated because people don't realise that many risks are associated with one another.
- E.g. If you smoke, drink and are obese then you are likely to have a diet high in LDL and salt.