Lifestyle and Risk

Question 1

Describe why animals have a heart and circulatory system

Answer 1

The heart and circulatory system have one primary purpose - to move substances around the body by mass flow. e.g. pumping blood

Question 2

Define the terms: ‘mass flow’ and ‘diffusion’

Answer 2

Mass flow- the transport of substances in bulk from one part of an organism to another

Diffusion- the net movement of molecules or atoms from a high concentration to a low concentration until evenly distrubuted

Question 3

Describe the features of a mass flow system and explain why certain organisms need to use mass flow

Answer 3

Features of mass flow systems:
A system of vessels to carry substances e.g. xylem, veins.
A way of making sure the substances move in the right direction e.g. valves, pressure.
A means of moving the substances fast enough to supply the needs of the organism e.g. heart.
A suitable transport medium e.g. blood.

Large organisms cannot rely only on diffusion as this process is much too slow to meet their needs. Mass transport enables organisms to overcome the limitation of diffusion.

Question 4

1.4) ★★ Describe the differences between ‘open circulatory systems’ and ‘closed circulatory systems’

Answer 4

Open:
1. Blood isn’t enclosed within blood vessels.Blood flows into large cavities. Blood is in direct contact with body tissues.
2. When blood is in direct contact with tissues, only then exchange of materials takes place.
3. Lower blood pressure, blood travels slower, less efficient at delivering substances around the body.
4. Generally animals with open circulatory systems are smaller in size

Closed:
1. Blood is always enclosed in blood vessels, i.e. arteries, capillaries and veins.
2. In capillaries, nutrients and waste materials are exchanged between tissues and blood by means of tissue fluid.
3. Higher blood pressure, blood travels faster, more efficient at delivering substances around the body.
4. Generally animals with closed circulatory systems are larger in size.

Question 5

1.5) ★★ Identify key features of single circulatory systems and double circulatory systems and explain their features

Answer 5

Single Circulatory Systems:
Blood only flows through the heart once for each complete circuit of the body.
No separate pulmonary circulation –
pulmonary and systemic circulation
together as one circuit.
Heart has two chambers.
Blood pressure drops through gas exchange organ (e.g. gills in fish) and isn’t increased again as it circulates around the body.
Oxygen and food substances required for metabolic processes are usually delivered more rapidly to cells. E.g. Fish

Double Circulatory Systems:
Blood flows through the heart twice for each complete circuit of the body.
Pulmonary circulation present and separate to systemic circulation.
Heart consists of three (amphibians) or four chambers – usually two atria and two ventricles.
Blood returns to the heart from the lungs, increasing
pressure so reducing the time it takes for the blood to circulate around the whole body.
The LV pumps blood faster, and at a higher pressure to the body. The RV pumps blood slower, and at a lower pressure to the lungs. This is important as it reduces the risk of
damage to the lungs.
Allows mammals and birds to have a high metabolic rate, because oxygen and food substances required for
metabolic processes can be delivered more rapidly to cells. E.g. Mamals

Question 6

1.6) ★★ Describe the structure of the pulmonary circulation and systemic circulation and list their differences

Answer 6

Pulmonary:
Starts at right ventricle
Ends at left atrium
Carries blood between heart and lungs
Blood to lungs is deoxygenated (pulmonary artery)
Blood returning to heart (via pulmonary vein) is oxygenated
Low pressure circulation (max 40mmHg)
Low pressure means less risk of damage to lungs plus slower speed of blood flow leading to increase gaseous exchange in lungs

Systemic:
Starts at left ventricle.
Ends at right atrium.
Carries blood between heart and all other organ systems except lungs.
Blood to body is oxygenated (aorta)
Blood returning to heart (via superior and inferior vena cava veins) is deoxygenated.
High pressure circulation (max 120mmHg).
High pressure means faster speed of blood flow resulting in increased
efficiency of blood flow to all body organs.

Question 7

1.7) ★★ List the components of blood and describe their functions

Answer 7

Blood is composed of cells in a liquid medium (plasma).
1) Plasma is mostly made of water, which contains many
dissolved substances such as oxygen, CO2, proteins, amino acids, sugars, salts, enzymes, hormones, antibodies and urea.
2) Red blood cells (erythrocytes) are mostly for oxygen transport (bound to haemoglobin)
3) White blood cells (leucocytes) are involved with defence.
4) Platelets (cell fragments / thrombocytes) are involved
with blood clotting.

Blood also has a role in regulating body temperature, and
transferring energy around the body.

Question 8

1.8) ★★★ Describe, with the aid of a diagram, the structure of a water molecule illustrating hydrogen bonding

Answer 8

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

Question 9

1.9) Describe how the polar (dipole) nature of water makes it a useful solvent

Answer 9

Many polar chemicals dissolve easily in water, allowing vital biochemical reactions to occur in the cytoplasm of cells. The dissolved substances can also be transported around organisms, in animals via the blood and lymph systems, and in plants through the xylem and phloem.

Question 10

1.10) ★★★ Describe the structure of arteries, veins and capillaries and relate this to their functions

Answer 10

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).

Question 11

1.13) ★★ Explain why the left ventricle wall is thicker than the right ventricle (in terms of pulmonary and systemic circulation)

Answer 11

Right Ventricle wall:
Pumps blood to lungs – pulmonary circulation.
Thinner – less cardiac muscle tissue.
Generates lower pressure (max 40mmHg) on contraction (ventricular systole).
Blood flow to lungs is slower.
Lower pressure means
* Less risk of damage to lung capillaries
* Slower speed results in increased gaseous exchange between alveoli and lung capillaries as blood is at the exchange surfaces for longer.
* High pressure is not needed as lungs are physically close to heart.

Question 12

1.14, 1.15) ★★★ Describe the sequence of events of atrial systole/diastole, ventricular systole/diastole and cardiac diastole in terms of blood flow, pressure changes and valves opening/closing

Answer 12

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

Question 13

1.16) ★★ Describe and explain what causes the valves to open/close

Answer 13

1. Blood moves due to the pressure differences (from high to low pressure) created by the contraction (systole) and relaxation (diastole) of the atria and ventricles during the cardiac cycle.
2. When the pressure in the atria > pressure in the ventricles, the
   atrioventricular valves open – this happens at the end of diastole & during atrial systole
3. When the pressure in the ventricles > pressure in the atria, the
   atrioventricular valves close – this happens during ventricular systole
4. When the pressure in the ventricles > pressure in the aorta & pulmonary
   artery, the semi-lunar valves open – this happens during ventricular systole
5. When the pressure in the aorta & pulmonary artery > pressure in the
   ventricles, the semi-lunar valves close – this happens during ventricular
   diastole

Question 14

1.18) ★★ Define what is meant by the terms; myocardial infarction, stroke, angina, aneurysm, thrombosis and endothelial dysfunction

Answer 14

Myocardial infarction(heart attack):
Death to areas of cardiac muscle due to lack of oxygen / blood flow
(ischaemia) as a result of a blockage in a coronary artery

Stroke:
Sudden death of some brain cells due to a lack of oxygen when the blood
flow to the brain is impaired by blockage or rupture of an artery to the brain.

Angina:
A pain in the chest, left arm, neck or jaw caused by lack of oxygen flow to
heart muscle.

Aneurysm:
A localised, blood-filled balloon-like bulge in the wall of a blood vessel

Thrombosis:
The formation of a blood clot inside a blood vessel, obstructing the flow of
blood through the circulatory system.

Endothelial dysfunction:
Damage to the delicate endothelial cells lining blood vessels e.g can be
caused by harmful chemicals from cigarette smoke (e.g. CO), by viral
infection, high blood pressure etc.

Question 15

1.21) ★★★ List the sequence of events that can lead to atherosclerosis

Answer 15

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.

Question 16

1.23) ★★★ List the sequence of events that leads to the formation of a thrombus (blood clot)

Answer 16

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

Question 17

1.24) ★★ Give definitions for: risk, probability, correlation and causation

Answer 17

Risk:
The probability of occurrence of some unwanted event or outcome.

Probability:
Has a precise mathematical meaning and can be calculated to give a numerical value for the size of the risk i.e. the extent to which an event is likely to occur, measured by the ratio of the favourable or unfavourable cases to the whole number of cases possible.

Correlation:
A change in one of the variables is reflected by a change in the other variable.

Causation:
When a change in one variable is responsible for a change in
another variable

Question 18

1.30) ★★ Describe 3 features of a good study

Answer 18

1) Clear aim
A well-designed study should include a clearly stated hypothesis or aim. The design of the study must be appropriate to the stated hypothesis or aim and produce results that are valid and reliable.
2) Representative sample
A representative sample must be selected from the wider population that the study’s conclusions will be applied to.
3) Reliable results
Any methods used must produce reliable data, from measurements that provide information on what the study set out to measure.

The method used to collect results must be reliable. For example, if measuring blood pressure, the same type of equipment and same procedure should be used each time the measurement is made.

Question 19

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

Answer 19

Controllable risk factors:
Smoking
* Excessive alcohol consumption
* Obesity
* Lack of exercise
* High blood cholesterol levels
* High blood pressure
Dietary factors:
* High Salt diet
* High saturated fat diet
* High cholesterol diet
* High calorie diet
* Low levels of antioxidants in
diet

Uncontrollable risk factors:
* Age – getting older
* Gender – being male
* Genetics – a family history
of CVD
Also:
* Diabetes (type 1)

Question 20

1.33) ★★ Explain, using a mind map or a spider diagram, how each risk leads to CVD

Answer 20

Risk factors for CVD (template)
- Explain the effects of each factor and indicate whether they are
controllable / modifiable or non-controllable / non-modifiable

Genetic:
Ethnicity
Weak blood vessels e.g. Mark – (haemorrhagic stroke).
Familial Hypercholestrolaemia
(FH) – high blood cholesterol levels.
Gender

Lifestyle:
Lack of exercise.
Smoking.
High levels of stress.
Excessive alcohol consumption.

Diet:
Low intake of antioxidants.
Too much carbohydrates.
Too much salt intake.
Too much cholesterol (LDL).
Too much saturated fats.
Obesity.

Question 21

1.34) ★★★ Explain how high blood pressure can lead to CVD and myocardial infarction

Answer 21

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

Question 22

1.35) ★★ Define the terms; hypertension, systolic pressure, diastolic pressure and sphygmomanometer

Answer 22

Hypertension:
Permanent or sustained high blood pressure (could be diastolic, systolic or both – each is indicative of a pathological condition).

Systolic pressure:
The pressure in an artery is highest during the phase of the cardiac cycle when the ventricles have contracted and forced blood into the arteries.

Diastolic pressure:
Pressure is at its lowest in the artery when the ventricles are relaxed.

Question 23

1.38) ★★ Define the terms monosaccharide, disaccharide and polysaccharides

Answer 23

Monosaccharide:
A simple sugar that constitutes the building blocks (monomers) of a more complex form of carbohydrate; examples are fructose, glucose, galactose (all hexose sugars).
Monosaccharides can be classified by the number of carbon atoms they contain: triose (3), pentose (5) e.g. ribose and hexose (6) etc..

Disaccharide:
Two monosaccharides linked together by a 1,4 glycosidic bond
form a disaccharide (e.g. maltose (glucose + glucose), lactose (glucose + galactose).

Polysaccharide:
Many monosaccharides (monomers) linked together by glycosidic bonds form the polymer called a polysaccharide (e.g. starch, cellulose, glycogen). Different properties to sugars (not sweet, and insoluble in water).

Question 24

1.41) ★★★ Draw a molecule of glucose

Answer 24

Monosaccharides
* glucose, fructose, galactose

Disaccharides
* maltose (glucose + glucose)
* lactose (glucose + galactose)
* sucrose (glucose + fructose)

Note: all of these sugars are sweet and soluble

Question 25

1.42) ★★★ Draw a labelled diagram showing 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 produced

Answer 25

Many monosaccharides linked together form a polymer called a polysaccharide Examples: * starch * cellulose * glycogen

Question 26

1.44) ★★★ Describe using a diagram how hydrolysis of maltose occurs and why water is needed

Answer 26

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

Question 27

1.45) ★★★ Name the two different polysaccharides that make up starch

Answer 27

Amylose: Insoluble in water. 1,4 glycosidic bonds. Stores energy. Coil shape made of glucose. Compact shape. Amylopectin: Broken down quicker as enzymes can go to different ends. Straight chain with side branches. 1,4 and 1,6 glycosidic bonds. Compact shape.

Question 28

1.47) ★★★ Explain with the use of diagrams why glycosidic bonds are called 1,4 or 1,6 glycosidic bonds

Answer 28

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. If they link the carbon 1 of one molecule with the carbon 6 of another then they are called 1-6 glycosidic bonds.

Question 29

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

Answer 29

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.

Question 30

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’, and showing where an ester bond is formed

Answer 30

When a triglyceride is formed by a condensation reaction 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.

Question 31

1.51) ★★★ Explain in a sentence and draw a diagram to illustrate differences between monounsaturated, polyunsaturated and saturated lipids

Answer 31

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.

Question 32

1.62) ★★ Explain how an energy imbalance can lead to obesity

Answer 32

An energy budget is a balance sheet of energy income against expenditure. Carbohydrates & lipids in the diet provide a source of energy. If the energy input > the energy output, weight will be gained as the excess carbohydrates is converted to fate. Over time, this can lead to obesity. If energy input < energy output where if you consume fewer kilojoules per day than you use, stored body energy will be used to meet the demand, resulting in weight loss.

Question 33

1.64) ★★ Write the equation for BMI with the correct units and work out BMI given values

Answer 33

BMI = Body mass (kg) / (Height x height (m) )

Question 34

1.65) State the limitations of using the BMI as an indicator of risk of CVD and state a suitable alternative measurement

Answer 34

BMI does not have an exact correlation with body fat levels, and may not be accurate for athletes, people over 60, or those with long-term health conditions. BMI does not give any indication where the fat is located on the body. There is evidence that waist-to-hip ratio is a better measure of obesity than BMI and shows a highly significant association with risk of heart attack. Waist-to-hip ratio is calculated by dividing waist circumference by hip circumference.

Question 35

1.67) ★★★ Describe a safe, reliable method for investigating the Vitamin C content of food and drink

Answer 35

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.

Question 36

1.70) ★★★ Describe a safe, reliable method for measuring the effect of caffeine on the heart rate of Daphnia

Answer 36

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.

Question 37

1.75) Suggest and explain 3 lifestyle changes that a doctor may recommend to a patient in order to reduce their risk of CHD

Answer 37

1. Reduce intake of saturated fats – this reduces the likelihood of atheroma formation 2. Stop smoking – cigarette smokers are 4 times as likely to develop CHD than non-smokers. They are also more likely to die from a heart attack when they have one 3. Do more exercise – helps prevent high blood pressure, and reduces the levels of LDLs in the blood (reducing atheroma formation)

Question 38

1.78) ★★ Describe the benefits and risks of antihypertensives, statins, anticoagulants and platelet inhibitory drugs

Answer 38

Drug- Antihypertensive - ACE inhibitors Benefits- Lowers blood pressure by reducing vasoconstriction of blood vessels so reducing risk of atherosclerosis Risks- Dry cough, dizziness due to rapid lowering of the blood pressure, abnormal heart rhythms and a reduction in the function of the kidney Drug- Antihypertensive - Ca2+ channel blockers Benefits- Lowers blood pressure by reducing vasoconstriction of blood vessels by blocking Ca2+ influx into muscle cells, which is required for muscle contraction so reducing risk of atherosclerosis Risks- Headaches, dizziness, swollen ankles due to a build up of fluid in the legs, abnormal heart rhythms, flushing red in the face and constipation Drug- Antihypertensive - Diuretics Benefits- Lowers blood pressure by reducing plasma volume (and so cardiac output) by increasing volume of urine produced so reducing risk of atherosclerosis Risks- Dizziness, nausea or muscle cramps Drug- Antihypertensive - Beta Blockers Benefits- Lowers blood pressure by preventing adrenalin from entering the protein receptors on cell surface membranes of organs such as the heart, making the contraction of the heart less strong, so blood pressure is not raised as much so reducing risk of atherosclerosis Risks- Dizziness, tiredness (due to slow heart beat), nausea, and diarrhoea. Drug-Statins Benefits- Statins are cholesterol-lowering drugs which work by: inhibiting an enzyme involved in the production of LDL cholesterol they improve the balance of LDLs to HDLs by causing more LDL receptor proteins to be present in the cell surface membranes of liver cells (resulting in more LDLs being taken out of the circulation) reduce inflammation of the lining of the arteries. All of this reduces the risk of developing atherosclerosis Risks-For most people there are no side effects, but some suffer from muscle and joint aches, nausea, constipation and diarrhoea. There are two serious, but very rare, side-effects: * A fatal form of muscle inflammation * Liver damage The other concern is that some people who take statins return to bad eating habits as they mistakenly believe that they are now protected from the general ill-effects of a bad diet! Drug-Anticoagulants e.g. warfarin Benefits-Prevents the blood from clotting too easily e.g. If someone has suffered a blood clot, or recently had heart surgery, or may suffer from a heart attack or ischaemic stroke. Warfarin is an anticoagulant that specifically interferes with prothrombin production Risks- Can cause massive internal bleeding and death (haemorrhaging). Drug- Platelet Inhibitory Drugs e.g. aspirin Benefits-These drugs make the platelets less sticky, and so reduce the clotting ability of the blood. Risks-The risks of aspirin are well-known – it irritates the stomach lining and causes bleeding in the stomach, which can become serious. Aspirin is often not as effective as warfarin, but there is a reduced risk of bleeding.