SNAB Topic 1 - Lifestyle, Health and Risk

Water

  • Water is used as the medium for transporting substances and carbon dioxide around the body
  • Water is a polar molecule (has an uneven charge distribution)
  • One end of the water molecule is slightly positive and the opposite end is slightly negative
  • Water is a liquid at room temperature
  • Hydrogen bonds are formed between the molecules due to their dipole nature
  • Water easily dissolves molecules held together by ionic bonds
  • Sodium and Chloride ions in salt are pulled apart and surrounded by water molecules
  • Water also dissolves polar molecules like sugars and amino acids
  • Non-polar molecules e.g. lipids aren't dissolved (so membranes aren't dissolved)
  • Water has a high specific heat capacity so a large amount of energy is required to cause a change in temperature
  • This means that the internal temperature is constant so there aren't any sudden temperature changes that may affect metabollic processes
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Circulatory Systems

  • Small organisms have an open circulatory system where oxygen and nutrients diffuse from a cavity into the cells when required
  • Larger organisms have a closed circulatory system involving blood vessels where nutrients and oxygen are transported all around the body
  • This is due to the differences in the Surface Area:Volume Ratios (SA:V)
  • Smaller organisms can diffuse substances into their cells due to a large SA:V ratio
  • The larger an organism, the smaller the SA:V ratio and so the need for a transport system is required to transport the substances to the body
  • SA:V Ratio is calculated by Dividing the Surface Area by the Volume
  • Mass Flow is the method of transport in mammals which allows blood to be pumped around the body based on pressure changes
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Arteries

  • Transport blood away from the heart
  • Have: a thick wall to withstand the high pressures
  • Smooth muscles allow alteration of the diameter of the lumen to vary blood flow
  • Elastic fibres allow the walls to stretch when blood is pumped into the artery and then recoil, smoothing blood flow
  • Lined with smooth layer of endothelial cells to create a low friction surface to ease blood flow
  • Narrow lumen to create a high blood pressure

Image result for artery cross section

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Veins

  • Veins carry blood towards the heart
  • They have a Thin Wall due to them having a Low Blood Pressure
  • There is very little smooth muscle or elastic fibres as there is no pulse of blood so there is no stretching or recoiling
  • There is a wide lumen to increase the flow of blood back to the heart
  • Valves are also used to stop backflow of blood and ensure one way flow

Image result for vein structure cross section

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Capillaries

  • Capillaries allow gas exchange between the blood and cells
  • Very thin wall (1 cell thick) to alllow rapid gas exchange between the blood and tissues
  • Very small lumen to increase friction between red blood cells and the walls to slow the flow and increase time for gas exchange to occur

Image result for capillary structure cross section labeled a level

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Heart Anatomy

Image result for heart structure a level

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Heart Dissection

  • The heart has its own blood vessels (Coronary Arteries) which can be seen branching over its surface which provide it with its own oxygen supply
  • Water running into the pulmonary vein will emerge at the aorta which shows that the seperated into two halves internally
  • Observing the left and right ventricles, different thicknesses can be observed. The Left Ventricle has thicker walls because it needs to maintain high pressure to pump blood around the whole body, whilst the Right Ventricle only has to pump blood to the lungs
  • Inside the heart, the atrioventricular valves can be seen to stop blood flow from the ventricles to the atria as well as the semilunar valves which stop blood flow from the arteries to the ventricles
  • Tendons are attached to the valves which prevent the valves turing inside out
  • The Septum can be seen which creates a divide between the left and right side of the heart
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The Cardiac Cycle

  • Blood drains into the atria from the veins (Vena Cava and Pulmonary Vein)
  • Raising of the blood pressure in the atria forces the atrioventricular valves to open
  • Contraction of the atrial muscles (Atrial Systole) forces more blood through the valve
  • As soon as Atrial Systole is over, the ventricles contract (Ventircular Systole)
  • This forces the atrioventricular valves to close and opens the valve in the mouth of the aorta and pulmonary artery
  • Once the blood has been ejected from the ventricles, the heart relaxes (Cardiac Diastole)

Image result for cardiac cycle stages

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Cardiac Cycle Graph

Image result for cardiac cycle stages (http://philschatz.com/anatomy-book/resources/2029_Cardiac_Cycle_vs_Heart_Sounds.jpg)

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Atherosclerosis

  • Atherosclerosis is the disease process that leads to Cardiovascular Diseases
  • Raised blood pressure causes damage to the endothelium
  • White blood cells move into the artery wall during an inflammatory response
  • Fatty deposits of cholesterol accumulate on the endothelium causing an athermoa
  • A build up of calcium salts and fibres lead to plaque formation
  • The artery becomes narrower and loses elasticity
  • This increases blood pressure resulting in a positive feedback loop
  • The more atheromas there are, the higher the risk of a blood clot and the higher the risk of Cardiovascular Disease
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Health Effects of an Atheroma

  • Increase Blood Pressure: Can damage kidneys, retina and may cause strokes
  • Aneurysms: Increased blood pressure causes swelling of an artery and the eventual bursting of it resulting in internal haemoraging
  • Angina: A chest pain felt during exercise, caused by reduced blood flow to the heart due to narrowing of coronary arteries (Ischaemia)
  • Myocardial Infarction: Heart attack, when a coronary artery becomes totally blocked, and part of the heart is starved of oxygen and dies
  • Transient Ischaemic Attack: A ministroke, where a clot temporarily blocks the flow of blood. Early warning signs of a stroke
  • Stroke: An interruption to the blood supply of the brain which can cause paralysis or death
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Thrombosis

  • Thrombosis is the scientific term for Blood Clots
  • There has to be a number of factors present before a clot can form to prevent clots forming at the wrong time or wrong place e.g. inside a blood vessel
  • When a cut occurs in the blood vessel, platelets gather at the site to form a platlet plug.
  • Platelets and the damaged tissue release thromboplastin
  • Thromboplastin catalyses the transformation of prothrombin into thrombin when Calcium and Vitamin K are present
  • Thrombin transforms Soluble Fibrinogen into insoluble fibrin which forms a mesh trapping blood cells and ions to form a clot
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The Clotting Cascade

Only Key Terms mentioned previously are required to be known

Image result for clotting cascade simplified

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Blood Pressure

  • Measured as Systolic Pressure/Diastolic Pressure
  • Measured in mmHg using a sphygmomanometer
  • Ideal blood pressure is 120/80 mmHg
  • Hypertension is defined as a blood pressure over 140/90 mmHg
  • Hypertension causes damage to the epithelium of the arteries making atherosclerosis more likely
  • This results in a higher risk of a heart attack
  • Stress and high salt intake can contribute to hypertension
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Risk Perception

  • People overestimate the risk of an event if it is:
  • Involuntary (being a passenger in an airplane as opposed to driving a car)
  • Dreaded (nuclear accident or natural disaster)
  • Not natural (nuclear power)
  • Unfair
  • Unfamiliar
  • Very Small
  • Poor diet, lack of exercise and smoking increase the risk of cardiovascular disease (CVD)
  • However, people underestimate the risk of CVD and don't change their lifestyles
  • Risk of CVD is increased due to peer pressures (drinking, smoking etc.), inability to assess the risks and basing the opinions on previous experiences
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Correlation and Causation

  • Correlation is the effect of one factor directly resulting in a change in another factor
  • Causation is the direct causal reason for a change in a factor due to another factor
  • Positive Correlation: When one factor increases, the other factor increases
  • Negative Correlation: When one factor increases, the other factor decreases
  • No Correlation: When an increase in one factor has no effect on the other factor
  • Can be analysed using Spearmans Rank

Image result for positive negative no correlation

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Cohort and Case Control Studies

Cohort Studies

  • Cohort Studies follow a large group of people over an extended period of time
  • The subjects are then monitored to see if they develop the condition
  • The cohort is then divided into two groups, those with the condition and those without
  • Subjects are then interviewed to assess their risk factors
  • Correlation between risk factors and development of the condition is looked for

Case-Control Studies

  • Case-control studies compare a group with the condition (Cases) to those without the condition (Control)
  • Past histories of the two groups are investigated
  • The study will have validity if the two groups are matched for other factors such as gender and age
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How to Make a Good Study

  • Variables should be controlled when selecting groups to ensure validity and reliability. (This is hard to do as humans are so variable)
  • Measurement techniques or the questions on a questionnaire must be standardised
  • Large sample sizes are required as some conditions only affect a small percentage of the population so in order to be analysed they require a large sample size. This also improves the validity of the study
  • The studied sample should also be representative of the whole population to avoid bias
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Basal Metabolic Rate (BMR)

  • Basal Metabolic Rate (BMR) is the basic energy required for a day to perform metabolic reactions
  • Energy budgets can be calculated by finding the amount of energy used to perform metabolic reactions. This should be the ideal energy taken in
  • An energy imbalance puts you at risk of weight gain and obesity or weight loss
  • More energy is required to be consumed if there is a disease e.g. Cystic Fibrosis, if they are exercising or if they are pregnant
  • Less energy is required to be consumed if there is less exercise being performed
  • BMR is measured in kJ/day
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Body Mass Index (BMI) & Waist-to-Hip

Body Mass Index (BMI)

  • BMI = body mass (kg) / (height (m))²
  • <20 = Underweight
  • 20-25 = Healthy Weight
  • 25-30 = Overweight
  • >30 = Obese
  • BMI doesn't take into account age or muscle mass so is unreliable

Waist : Hip Ratio

  • The size of the waist's diameter is compared to the hips diameter
  • The ratio should not be greater than:
  • 0.9 in men
  • 0.85 in women
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Monosaccharides

  • Single sugar units (monomers) that make up carbohydrates
  • They have the General formular CnH2nOn
  • Hexose Sugars have 6 carbons e.g. Glucose
  • Molecules are normally cyclic and the carbons are labeled clockwise from the oxygen atom
  • Glucose is the source of most readily avaliable energy and is required in respiration
  • It is soluble in water so can be easily transported
  • It is a relatively small molecule so can move into cells
  • It has two isomers: α-glucose and β-glucose
  • Two glucose molecules form maltose
  • Fructose is a sweet monosacharide that forms sucrose when paired with glucose
  • Galactose is a monosacharide that forms lactose when paired with glucose
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Glucose

Image result for alpha glucose

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Forming Disaccharides

  • Disaccharides are two single sugar units bonded together
  • The bond between two monosaccharides is a glycosidic bond
  • Monosaccharides bond together at carbons 1 and 4 (forming a 1,4-glycosidic bond)
  • The reaction to join two monosaccharides is a condensation reaction and removes one water molecule from the reaction
  • The reaction to split a disaccharide is a hydrolysis reaction and requires water to split the glycosidic bond

Image result for condensation hydrolysis reactions

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Polysaccharides

  • Multiple monosaccharides bonded together in a polymer
  • Larger molecules so require breaking down before they can be transported into a cell
  • Starch consists of amylose and amylopectin
  • Amylose is a straight coiled chain that consists of only 1,4-glycosidic bonds
  • Amylopectin is a branched molecule that consists of both 1,4 and 1,6-glycosidic bonds
  • The coiled shape of starch makes it more compact, so it can store a lot of glucose (and energy) in a small space
  • It is insoluble so doesn't disrupt the osmotic balance
  • The branches on amylopectin allow it to be easily hydrolysed so it can quickly release energy
  • Glycogen consists of more frequent branches which results in quicker hydrolysis of the glucose in its structure
  • Glycogen is the store of glucose in muscles and the liver
  • Cellulose is formed from straight chains of β-glucose molecules bonded together and held together by hydrogen bonds
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Triglycerides

  • Lipids are fats and oils and are all hydrophobic molecules
  • Lipids act as energy stores, waterproofing and in cell membranes
  • Triglycerides are made of three fatty acid and a glycerol molecule joined together by ester bonds during 3 condensation reactions (one for each tail)

Image result for triglyceride structure

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Fatty Acids

  • Lipids vary depending on the fatty acid structure
  • Saturated fatty acids have no double bonds and contain the maximum number of hydrogens per carbon atom e.g. Palmitic Acid
  • Monounsaturated fatty acids have one double bond e.g. Oleic Acid
  • Polyunsaturated fatty acids have multiple double bonds e.g. Omega 3
  • Unsaturated fatty acids have kinks due to the double bonds, which makes them more fluid
  • Transfats have a double bond but the carbon chain is seen in a trans-isomer. These are very bad for consumption

Image result for saturated vs unsaturated vs trans fatty acid structure

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Cholesterol

  • Cholesterol is an important part in regulating the fluidity of membranes
  • Low Density Lipoproteins (LDLs) are formed from saturated fats bonded to proteins which bind to cell surface receptors which become saturated leaving LDLs in the blood
  • These have been linked to the formation of atheromas and need to be reduced
  • High Density Lipoproteins (HDLs) are formed from unsaturated fats bonded to proteins which aid in transporting cholesterol away from the body to the liver where it is broken down
  • These have been reducing the formation of atheromas and should be maintained at high levels

Image result for cholesterol

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Nonmodifiable Risk Factors

  • Gender: Oestrogen gives women some protection against CVD before the menopause
  • Age: Elasticity and width of arteries decreases with age
  • Genetics: Inherited tendancy to have a high blood pressure, poor cholesterol metabolism or easily damaged arteries
  • The Apolipoprotein Genes result in the formation of LDLs and VLDLs
  • Inherited Diseases: Type 1 and 2 Diabetes can reduce the removal of glucose from the blood by producing less insulin
  • Race and Ethnicity: Certain ethnicities are at a higher risk of developing a CVD
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Modifiable Risk Factors

  • Smoking: Carcinogens cause artery damage, tar creates a surface for a clot to form
  • Inactivity: Performing little exercise results in less energy being used and so an increase in body weight from stored fats. Regular exercise reduces the blood pressure and raises HDL levels
  • Stress: High stress levels can cause damage to the arteries resulting in atheroma formation
  • Fats: High saturated fat intake results in an increase in LDL levels
  • Salt: Salt results in a raised blood pressure which damages the artery walls
  • UV light exposure: UV light causes an increase in free radicals which damage cells and DNA
  • Antioxidants: Antioxidants reduce the damage that radicals do to cells and DNA. Antioxidants can be found in Fruit Juices.
  • Alcohol: Excessive consumption of alcohol results in liver damage and poor metabolism which increases the risk of CVD. Moderate drinking of some alcohols such as red wine can increase antioxidant levels
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Reducing Risk of CVDs

  • Stop smoking
  • Maintain low blood cholesterol levels
  • Maintain a low resting blood pressure (120/80 mmHg)
  • Maintain a normal BMI and Waist:Hip Ratio
  • Take regular physical exercise
  • Moderate or no alcohol consumption
  • Reduce stress levels
  • Reduce saturated fat levels (reduces total cholesterol but maintains high HDL levels)
  • Eat more polyunsaturated fats (reduces LDL levels)
  • Reduce salt (lower fluid levels and lower blood pressure)
  • Eat more fruit and vegetables (antioxidants and non-starch carbohydrates = lower cholesterol)
  • Eat more oily fish (reduces blood pressure and risk of blood clotting)
  • Eat more non-starch polysaccharides
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CORE PRACTICAL - Vitamin C

Method

  • Pipette a known volume of DCPIP into a conical flask
  • Fill a burette with a volume of a fruit juice and record the starting reading
  • Open the tap of the burette and allow the juice to flow into the conical flask
  • Swirl the conical flask to prevent a localised change in colour
  • Turn the tap to allow the juice to drip through one drop at a time near the end point
  • Turn the tap off when a colour change has occured (Blue -> Colourless)
  • Record the final burette reading and calculate the volume of fruit juice used
  • Repeat 3 times with the same fruit juice and disregard any annomalies
  • Repeat the process with different fruit juices
  • Compare the recordings for each fruit juice with that of pure Vitamin C to deduce the amount of Vitamin C in each fruit juice

Vitamin C provides electrons for the DCPIP which causes the colour change

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CORE PRACTICAL - Daphnia

Method

  • Place a daphnia on a microscope slide with water and a piece of cotton wool covering it
  • Count the resting heart rate of the daphnia under a microscope
  • Repeat 3 times and calculate an average
  • Add a drop of caffeine to the daphnia and count the heart rate
  • Repeat 3 times and calculate an average
  • Repeat with different amounts of caffeine

Ethical Issues

  • Daphnia have a simple nervous system so don't feel as much pain
  • No need for a dissection as the heart is visable due to the daphnias transparent body
  • Daphnia are abundant and there will be no loss to genetic variation
  • Daphnia can't give consent to be tested on
  • Daphnia can't be compared fully to humans as their hearts work in a different way
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Antihypertensives

  • Diuretics:
  • Increase the volume of urine; lower blood volume and blood pressure
  • Can cause dizziness, nausea and muscle cramps
  • Calcium Channel Blockers:
  • Disrupts the calcium ion movement through calcium channels in the cell membrane, reducing muscle contraction - increasing artery diameter, reduces strength of heart beats and the frequency and lowering the blood pressure
  • Can cause headaches, dizziness, swollen ankles, constipation and flushing in the face
  • ACE Inhibitors:
  • Blocks the production of angiotensin converting enzymes, reducing arterial constriction and lowering blood pressure
  • Can cause coughing, dizziness, abnormal heart rhythm (arhythmia) and impared kidney function
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Statins, Aspirin and Anticoagulents

  • Statins
  • Inhibit an enzyme in the liver that produces LDL cholesterol
  • Can cause: tiredness, distrubed sleep, nausea, diarrhoea, headaches, muscle weakness and require people to have a healthy diet
  • Anticoagulents (Warfarin)
  • Reduce the risk of clot formation
  • Can cause a risk of uncontrolable bleeding and requires dosage to be precise
  • Platelet Inhibitory Drugs (Statins)
  • Make platelets less sticky reducing clot formation
  • Aspirin can cause irritation of the stomach lining and can cause stomach bleeding
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