TOPIC 1

Water is a solvent meaning substances are able to dissolve in it.

Water transports substances which can be transported easily if they're dissolved in water.

A molecule of water is two hydrogen and one oxygen and they are joined by shared electrons.

Water is dipolar, meaning one side of the atom is negative and one is positive.

Water is very cohesive due to it being dipolar which helps it to flow.

Multicellular organisms need mass transport systems.

Mass transport systems are used to carry raw materials from specialised organs to the body cells.

In mammals, the mass transport system is the circulatory system which carries blood throughout the body.

Individual cells in tissues and organs get nutrients and oxygen from the blood.

The heart has four chambers, two atrium above and two ventricles below.

The left and right sides are separated by a septum.

The ventricle walls are thicker than the atria, the left one is thicker than the right because the left sides pumps the blood to the whole body whereas the right pumps blood only to the lungs.

The atrioventricular valves seperate the atria from the ventricles and the semilunar valves are at the entrance to the arteries leaving the heart.

The aorta leaves from the left ventricle and the pulmonary artery from the right ventricle.

The vena cava and pulmonary vein enter the atria.

The heart is supplied with blood via the coronary arteries.

The left ventricle is thicker as it has to pump oxygenated blood to the whole body.

The right ventricle only pumps blood to the lungs, this blood is deoxygenated.

The atrioventricular valves link the atria to the ventricles to stop the back-flow of blood to the atrium when the ventricles contract.

The semi-lunar valves link the ventricles to the pulmonary artery and aorta and stop blood back-flowing into the heart after the ventricles contract.

The valves only open one way and whether they are open or closed depends on the relative pressure in the heart chambers.

If there is higher pressure infront of the valve, it is forced shut. When the pressure is higher behind the valve, it is forced open.

There are three types of blood vessels - arteries, veins and capillaries.

Arteries carry blood from the heart to the rest of the body. They have thick muscular walls and have elastic tissue so they are able to handle high amounts of pressure. The endothelium is folded to allow the artery to expand.

Veins take blood back to the heart. They're wider than arteries with very little elastic and muscle tissue. Veins contain valves to stop the blood flowing backwards and blood-flow through the veins is aided by the contraction of body muscles.

Capillaries are the smallest blood vessel. They are where metabolic exchange occurs meaning substances are exchanged between cells and the capillaries. There are networks of capillaries in tissues which increase the surface area for exchange. They are also only one cell thick.

An ongoing sequence of contraction (systole) and relaxation (diastole) of the atria and ventricles which keeps blood continuously circulating the body.

1. Ventricular disasole, atrial systole:The ventricles are relaxed and the atria contract, this pushes the blood into the ventricles.

2. Ventricular systole, atrial diastole:The atria relax and the ventricles contract, the AV valves shut and the SL valves open and blood is forced out of the ventricles into the arteries.

3. Cardiac diastole:The ventricles and atria both relax. The SL valves close and blood begins to fill the atria again. As the ventricles continue to relax, the blood is able to flow passively into the ventricles from the atria. The atria contract and the whole process begins again.

Cardiovascular disease starts with an atheroma formation.

1. The endothelium becomes damaged and there is an inflammatory responce meaning the white blood cells move into the area.

2. The white blood cells and lipids (fats) from the blood clump together under the damaged endothelium which then form fatty streaks.

3. Over a period of time, more white blood cells, lipids and connective tissue build up and harden to form a fibrous plaque called an atheroma.

4. This fibrous plaque partially blocks the lumen and restricts the blood flow which causes blood pressure to increase.

5. The hardening of arteries caused by atheromas is called atherosclerosis.

Thrombosis is used by the body to prevent loss of blood when a blood vessel is damaged.

1. An atheroma can rupture the endothelium of an artery, damaging the artery wall and leaving a rough surface.

2. A protein called thromboplastin is released from the damaged blood vessel.

3. Thromboplastin and calcium ions from the plasma trigger the conversion of prothrombin, which is a soluble protein, into thrombin which is an enzyme.

4. Thrombin then catalyses the conversion of fibrinogen (a soluble protein) to fibrin (solid insoluble fibres).

5. The fibrin fibres form a mesh by tangling together. Platelets and red blood cells then get trapped in the mesh and a blood clot is formed.

Coronary heart disease is when coronary arteries have lots of atheromas in them which restricts blood flow to the heart.

The atheromas also increase the risk of blood clots forming, which then leads to an increased risk of heart attack.

Diet:A diet in high saturated fats increases the risk of CVD because it increases blood chloesterol which increases the chances of atheroma formation. A diet high in salt also increases the risk of CVD because it increases the risk of high blood pressure which can damage the endothelium.

High blood pressure:High blood pressure increases the risk of damage to the endothelium which increases the risk of atheroma formation. Excessive alcohol consumption, stress and diet all increase blood pressure.

Smoking: Carbon monoxide combines with haemoglobin which reduces the amount of oxygen transported in the blood. If heart muscles do not recieve enough oxygen it can lead to a heart attack. Nicotine makes platelets sticky increasing the chance of blood clots. Smoking also decreases the amount of antioxidants in blood which are important for protecting cells from damage.

Inactivity: A lack of exercise increases the risk of CVD because it increases blood pressure.

Genetics:Some people inherit genes that make them more likely to have high blood pressure or high blood chloesterol so they are more likely to suffer from CVD.

Age:The risk of developing CVD increases with age as plaque can build up very slowly over time which can eventually lead to CVD.

Gender:Men are more likely to suffer from CVD than pre-menopausal women. This is due to their different levels of hormones. Oestrogen which is typically higher in females increases the level of good cholesterol. The relatively low level of this hormone can lead to higher levels of total blood cholesterol.

Prevention is better than a cure but there are some treatments for CVD.

Antihypertensive drugs reduce high blood pressure. These drugs include beta blockers which reduce the strength of the heart-beat and vasodilators which widen the blood vessels. They also contain diuretics which work by reducing the amount of sodium which results in less water which reduces the blood volume.

Statins reduce chloesterol in humans by reducing the amount of 'bad' LDL cholesterol produced inside the liver. A lower blood cholesterol reduces atheroma formation.

Anticoagulants reduce blood-clotting. This means blood clots are less likely to form at sites of damaged arteries so there's less chance of the blood vessels becoming blocked.

Platelet inhibitory drugs are a type of anticoagulant which works by preventing platelets clumping together to form a blood-clot.

Organisms take in and use up energy. An energy budget is used to describe the amount of energy taken in and used up.

Energy imbalance causes changes in weight. A persons energy budget should be balanced and if there is an imbalance it will affect the persons weight.

Weight gain:If energy intake is higher than energy output, the excess energy will be turned into fat reserves and the person will gain weight. If the energy difference is high and it is sustained over a long period of time, the person may become obese.

Weight loss:If energy intake is lower than energy output, the body will have to get more energy so will turn some of the fat reserves into energy, causing the person to lose weight. If the difference is sustained over a period of time, the person may become underweight.

Most carbohydrates are large complex molecules made from long chains of monosaccharides.

Glucose is a monosaccharide with six carbon atoms in each molecule and there are two types of glucose, alpha and beta.

Glucose's structure is related to it's function as a main energy source. It's structure makes it soluble so it can be easily transported and it's chemical bonds contain lots of energy.

Monosaccarides are joined together by glycosidic bonds in a condensation reaction to form disaccharides and polysaccharides.

Two alpha-glucose molecules are joined together to form maltose. Lactose is formed with a beta-glucose and galactose and sucrose is formed with an alpha-glucose and fructose.

Lots of alpha-glucose join together to form amylose. Amylopectin is formed with alpha-glucose and lots of side branches and glycogen is formed with alpha-glucose and even more side branches.

Cells get energy from glucose. Plants store excess glucose as starch and it is broken down when it is needed.

Starch is a mixture of two polysaccharides of alpha-glucose - amylose and amylopectin.

Amylose is a long unbranched chain of glucose joined together with 1-4 glycosidic bonds. It is a cylinder shape meaning it is compact and easier to store.

Amylopectin is a long branched chain of glucose that contains 1-4 and 1-6 glycosidic bonds.The branches mean the enzymes can reach the bonds easily and glucose can be broken down quickly.

Starch is also insoluble so it doesn't cause water to enter the cells by osmosis, which makes it good for storage.

Animal cells also get energy from glucose but store excess glucose as glycogen, another polysaccharide of alpha-glucose.

It has 1-4 and 1-6 glycosidic bonds except it has more side branches meaning that glucose can be released quickly.

It is also very compact so good for storing.

Glycogen is also insoluble in water, so the cells do not swell due to osmosis.

Glycogen is a large molecule, meaning it can store a lot of energy.

A tryglyceride is made of one molecule of glycerol with three fatty acids attached to it.

Fatty acid molecules have long tails made of hydrocarbons and the tails are hydrophobic which makes the lipids insoluble in water.

All fatty acids consist of the same basic structure but the hydrocarbon tail varies.

Tryglycerides are formed by condensation reactions and broken up by hyrdolosis reactions.

Three fatty acids and a single glycerol molcule are joined together by ester bonds.

A hydrogen atom on the glycerol molecule bonds to a hydroxyl (OH) group on the fatty acid, releasing a molecule of water.

The reverse happens in hydrolysis - a molecule of water is added to each ester bond to break it apart and the triglyceride splits up into three fatty acids and one glycerol molecule.

There are two types of lipids - saturated and unsaturated.

Saturated lipids are mainly found in animal fats such as butter and unsaturated lipids are mostly found in plants such as olive oil.

Unsaturated lipids melt at lower temperatures than saturated ones.

The difference between these two types of lipids in their hydrocarbon tails. Saturated lipids don't have any double bonds between their carbon atoms in their hydrocarbon tails but unsaturated lipids do have double bonds.

Cholesterol is a type of lipid that is made in the body and some is needed for the body to function normally.

Cholesterol has to be attached to proteins to move around so the body forms lipoproteins.

High density lipoproteins are mainly proteins, they transport cholesterol from body tissues to the liver where it is recycled or excreted.

Their function is to reduce the total blood cholesterol when it gets too high.

Low density lipoproteins are mainly lipids and transport cholesterol from the liver to the blood where it circulates until needed by cells.

Their function is to increase total blood cholesterol when the level is too low.