EDEXCEL SALTERS NUFFIELD BIOLOGY A LEVEL- TOPIC 1, Exams of Advanced Education

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EDEXCEL SALTERS NUFFIELD BIOLOGY A

LEVEL- TOPIC 1

Define monosaccharide and give the structural isomers for glucose - Carbohyrate monomer which cannot be broken down further

• fructose -galactose Alpha Glucose structure - -- Monosaccharide general properties - small - can diffuse through cell membranes soluble - in water so can dissolve in blood for transport sweet How are disaccharides and polysaccharides formed? Bonding? - Condensation reactions (reversible, passive) Glycosidic 1-4 bonds Water produced Where are Maltose, sucrose and lactose found, and what monosaccharides and bonding do they each have? - maltose: 2 glucose, found in barley seeds, alpha 1- glycosidic bonds sucrose: plants, glucose and fructose, alpha 1-2 glycosidic bonds lactose: milk sugar, galactose and B glucose, beta 1-4 glycosidic bonds Describe the structure of starch - - mixture of amylose and amylopectin
• amylose is linear, non-branched, 1-4 bonds only
• amylopectin is branched, with 1-6 bonds for branches - it is less compact than amylose and is broken down more quickly Function of starch - - short term storage of energy in plants, which does not disrupt osmotic gradient
• found in plasmids, stored as starch grains, insoluble Glycogen structure - Branches have alpha(1,6) bonds; Linkages have alpha(1,4) bonds Highly branched - more than amylopectin - animals have higherbasal metabolic rate so needs energy faster and more
• less dense than starch
• broken down by glycogen phosphoyrlase fatty acid structure - COOH carboxyl group head, hydrocarbon tail (R group that varies in length) saturated or unsaturated

Difference between saturated and unsaturated fatty acids? - Saturated = full

• they have no double bonds and no kinks - one straight chain - this means they can pack more tightly and require more energy to split apart - solid at RTP Unsaturated = not full
• they have at least one double bond (mono or polyunsat) creating kinks
• they don't pack as tightly and require less energy to break apart so liquid at RTP What elements are lipids made of? - carbon, hydrogen, oxygen What elements are carbohydrates made of? - carbon, hydrogen, oxygen What elements are proteins made of? - carbon, hydrogen, oxygen, nitrogen What is the structure of a triglyceride? - one glycerol and three fatty acids ester bonds condensation reaction CH2O-OC.R x Properties of triglycerides - -insoluble - storage of energy -hydrophobic -less dense than water -- buoyancy
• used in insulation and protection too -poor heat conductor - insulating layer of subcutaneous fat
• does not disrupt osmotic gradients Phospholipids structure - phosphate group head, 2 fatty acids, glycerol backbone ester bonds condensation amphipathic - hydrophobic tails and hydrophilic heads Functions of phospholipids relating to structure - cell membrane! phospholipids form a bilayer in water because of hydrophobic tails and hydrophilic heads self-sealing if punctured or opened fluid so individual molecules can move laterally emulsion test for lipids - - Shake test substance with ethanol for about a minute, then pour the solution into water.
• Any lipid will show up as a milky emulsion.
• The more lipid there is, the more noticeable the milky colour will be. Homeotherm definition - Organism that can regulate its core temp

Poikilotherm definition - Organism that cannot regulate core temp Xerophite definition - Organism adapted to live in arid conditions e.g. cammels Roles of lipids and why their structure allows this - - long term energy store: insoluble, non-polar, higher proportion of H atoms to O atoms compared to carbs and proteins so release a larger amount of energy

• thermal insulation: poor heat conductors
• electrical insulation: poor electrical conductors e.g. myelin sheath
• buoyancy - less dense than water so float on surface
• protection from knocks - organs not protected by skeletal system
• cell membranes - phospholipids form a bilayer because amphipathic Describe how hydrogen bonding determines many properties of water - polar - because of both +ve and -ve charge cohesion - H bonds between molecules form a strong lattice and allows water molecules to stick together adhesion - attracts other charged molecules and polar molecules habitat - constant temp of sea and ice freezes top down because of air spaces making it less dense - forms an insulating layer and keeps sea water liquid evaporation - allows heat loss during homeostasis solvent - other polar molecules can dissolve in, allowing water to be a transport medium thermal insulator - high latent heat capacity gives a relatively stable temperature, (same as habitat point) surface tension Why do multicellular organisms need transport systems? - smaller SA:Vol ratio than single-celled organisms so diffusion would take much longer, also there are layers of cells where there would need to be a lower concentration in the next layer Where does diffusion take place in multicellular organisms? - - alveoli (lungs)
• villi (small intestines)
• Ca2+ ions sarcoplasmic reticulum during respiration What is the difference between an open and closed circulatory system? Describe them both. - open - basic, molluscs have this, haemolymph fluid pumped by heart through vessels into a haemocoel (cavity) and back into the heart. It is quite slow as steep concentration gradients are not maintained closed - more complex, blood is fully enclosed, preventing the mixing of oxygenated and deoxygenated blood, gradients are maintained and regulation is quicker and more efficient

Difference between single and double circulatory systems? - single - one way, two chambered heart, e.g. in fish, relies on a single pump to direct deoxygenated blood towards the gills for instance, where once oxygenated it continues to travel to the body double - two separate loops: pulmonary and body, 4 chambered heart to avoid mixing oxygenated and deoxygenated blood, delivery is faster due to steeper concentration gradients, and pressure is higher. Describe the heart structure - - left and right atria

• left and right ventricles
• atrioventricular valves
• semilunar valves
• septum
• tendinous cords
• aorta
• vena cava
• pulmonary veins and arteries What do semilunar valves prevent? - Backflow of blood from the aorta (high BP) back into left ventricle during diastole What do atrioventricular valves prevent? - Backflow of blood into the left and right atria from the ventricles during ventricular systole Why does the LHS of the heart have a more muscular wall? - It has to make a stronger contraction to push the blood at a higher pressure further around the body than the right side, which only has to push it to the lungs What would be the result of a hole in the septum of the heart? - Oxy and deoxy blood would be able to mix -> blood would have a lower % saturation of oxygen so the heart and breathing rates would have to increase to supply the cells with enough O2 for respiration What would be the result of atrioventricular valve failure? - - backflow of blood into atria
• O2 delivered less efficiently and slower
• fatigue and shortness of breath What would be the result of a blocked coronary vein? - - no oxygenated blood would reach cardiac tissue
• cells revert to anaerobic respiration, producing lactic acid which builds up and causes tissue damage, heart attacks and angina Describe atrial systole - atria (full of blood) contract and force blood through the atrioventricular valves and into the ventricles
• 70% of the blood flows passively

Describe ventricular systole - atria relax, thick muscular ventricle walls contract and force blood into the aorta and pulmonary artery the pressure of blood causes the atrioventricular valves to shut, preventing backflow of blood into the atria

• first part of heartbeat Describe diastole - - ventricles relax
• BP drops below the BP in the arteries, causing semilunar valves to shut
• heart muscle relaxes and blood from vena cava and pulmonary vein trickles into atria Describe how the cardiac cycle appears on a graph - - ventricular systole is more forceful and high pressure than atrial systole
• when the atria/ventricles relax, the pressure decreases Describe the (electrical) control of the heartbeat - heart muscle is myogenic - it can contract without the need of external electrical impulses SAN = sino-atrial node SAN sends electrical impulses across the atria in a wave of depolarisation both atria contract but the ventricles do not because collagen fibres block the impulses (high electrical resistance) the AVN (atrioventricular node) I the lower wall of the right atrium picks up the SAN impulse and generates its own electrical impulse in response travels down bundle of his, through Purkinje fibres and to myocytes which lead to the ventricles contracting depolarised myocytes remain contracted until repolarisation What does an electrocardiogram show and what does each wave/peak represent - EEG = used to detect changes in electrical activity in the cardiac cycle e.g. bradycardia, tachycardia, ectopic heartbeat P wave - atrial systole wave of depolarisation from SAN QRS complex - ventricular systole, larger than atrial because more energy is needed to make ventricles contract T wave - diastole, takes a longer time for repolarisation and relaxation of whole heart What is the rate of depolarisation of the SAN affected by? - adrenaline -> excitatory effect, faster and stronger contractions due to adrenaline binding to SAN receptors noradrenaline -> excitatory effect acetylcholine -> inhibitory effect, slowing HR Describe what an elevated ST segment shows on an ECG - enlarged left ventricle or impending heart attack, possibly due to CVD Describe what ventricular fibrillation shows in an EEG - absence of a coordinated ventricular contraction, caused by chaotic electrical activity CPAC: effect of caffeine on daphnia - - cotton wool on cavity slide to restrict movement

• distilled water added to maintain sufficient O2 supply
• view under low power light so temperature doesn't get too high and damage the daphnia
• count heartbeats per min
• repeat with different concentrations of caffeine solution
• CVs: temp, vol of caffeine solution, same age/gender/size of daphnia Why use daphnia in an observation experiment? - - transparent so can observe living processes such as heart beat
• invertebrate so likely to feel less pain than vertebrates - fewer ethical issues Describe the structure and function of arteries - Oxygenated blood (except pulmonary artery) away from heart (all) Thick muscular walls carry blood at high pressure Narrow lumen increases BP Muscle fibres help vasoconstriction and dilation and control the amount of blood delivered to tissues Elatic fibres allow the walls to stretch with systole and recoil with diastole No valves because high BP and mostly travelling with gravity anyway Blood flows in pulses Describe the structure and function of veins - Deoxygenated blood (except pulmonary vein) carried towards the heart Walls are thin and there is a wide lumen, decreasing the BP to encourage blood flow which is usually against gravity Backflow is made more likely by low BP so valves are present to prevent this Veins are found within antagonistic pairs of muscles - contractions help to push the blood through the veins No pulse so no need for elastic fibres for recoil Describe the structure and function of capillaries - Walls are 1 cell thick, to pass close to body for efficient transport of materials - short diffusion distance Permeable, no elastic tissue, lumen slightly smaller than RBC diameter so transit time is slower to maximise transfer of substances Connected to the venules RBC structure and function - - biconcave shape to increase SA
• no nucleus or organelles to increase space for O
• haemoglobin - 4 polypeptide chain structure with an Fe2+ containing haem group, binds with O2 in a reversible reaction Describe the clotting process (coagulation) - - damaged wall of a blood vessel exposes collagen fibres
• platelets stick to fibres, swelling and activating thromboplastins (chemicals) which they release
• thromboplastins attract clotting factors (proteins) and set off a cascade effect

• in the presence of Ca2+ ions and vitamin K, thromboplastin converts prothrombin (inactive protein) to thrombin (active)
• thrombin catalyses the conversion of fibrinogen (soluble) into fibrin (insoluble)
• a fibrous mesh traps thrombocytes and strengthens the platelet plug, forming a blood clot How can diseases be grouped? - - acute (rapid onset, short lifespan) or chronic (slow onset, long-lasting)
• multifactorial or single factor -infectious or non-infectious (inherited/deficient/mental health) Define Cardiovascular Disease - The disease of heart and blood vessels Chronic, multi-factoral, non-infectious Symptoms: myocardial infarctions, strokes, angina, high respiratory rate Factors affecting CVD - - age - chronic = symptoms seen later in life, blood vessels lose elasticity over time and artery wall structure deteriorates
• gender - males more likely because oestrogen protects against CVD
• high BP - causes hypertension, leading to atherosclerosis as damage is done to the blood vessel walls
• genetics - high BP and poor liver function may be inherited
• smoking - cigarette chemicals raise BP and increase cholesterol, nicotine reduces blood clotting ability, carbon monoxide reduces O2 levels which leads to BP increase
• lifestyle and diet - high proportion of LDL and low HDL cholesterol in diet increases atherosclerosis risk, obesity from sedentary lifestyle risks hypertension and high BP Describe the process of atherosclerosis - - high BP causes damage to endothelium lining of artery wall -LDL cholesterol accumulates and oxidises, triggering an inflammatory response
• macrophages attempt to phagocytose the LDL but cannot, transforming into foam cells and depositing contents into the breakage, forming an atheroma
• a hard plaque forms over the top due to calcium salts and fibrous tissues accumulating and reducing elasticit of artery wall
• endothelium ruptures itself to attempt to repair itself, which exposes collagen fibres and begins the clotting process
• clots can block arteries or break off and block capillaries Describe how platelet inhibitors work against CVD. Strengths and Weaknesses/Risks - - reduce blood clot formation by preventing clumping platelets
• useful for treating people that already have CVD
• side effects include excess bleeding, nausea, diarrhea high dosage needed for efficacy Describe how statins work against CVD. Strengths and Weaknesses/Risks - - useful preventative measure, can be found naturally in some foods
• reduces cholesterol levels in blood

• does not affect LDL to HDL ratio
• liver failure, increased risk of diabetes Describe how anticoagulants work against CVD. Strengths and Weaknesses/Risks - - reduce blood clot formation by preventing new clots from forming and existing clots from becoming larger
• can be used with patients who already have CVD
• side effects - excess bleeding if wounded, anaemia
• cannot remove existing clots Describe how antihypertensive drugs work against CVD. Strengths and Weaknesses/Risks - - lowers BP e.g. vasodilators widen blood vessels, beta blockers reduce heart beat strength
• useful preventative drug, can be given in combinations
• fainting, poor circulation to extremities, abnormal heart rhythms What is the difference between HDL and LDL cholesterol? - HDL - high density lipoprotein
• removes excess cholesterol from cells and binds to it, carrying it back to the liver to be recycled LDL - low density lipoprotein
• sat fats, delivers cholesterol to the cells where it is needed in membranes, or synthesis of hormones, known as 'bad' cholesterol because if in excess, it can build up in the arteries CPAC: Vit C in fruit juices - - DCPIP in a test tube
• using a burette, add 1% vit c solution drop by drop into the test tube until the DCPIP turns from blue to colourless. Record how much vit C it took to reduce the DCPIP.
• repeat with fruit juices and calculate the vit C contents from the vol taken to decolourise DCPIP