Biology Unit 1 Topic 1: Lifestyle, Health and Risk

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Circulatory Systems 1

Unicellular Organisms:

  • Substances and materials such as glucose and oxygen diffuse directly into the cell. The diffusion rate is quick because of the short distance the substances have to travel.

Multicellular Organisms:

  • Diffusion would be too slow to move substances round the larger bodies of multicellular organisms as they have a smaller surface area to volume ratio. They have mass transport systems (circulatory system).
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Circulatory Systems 2

Closed circulatory systems:

  • Blood is enclosed in narrow blood vessels, which increases efficiency, as blood travels faster at a higher pressure.
  • Blood leaves heart under pressure → arteriesarteriolescapillaries.
  • After passing through capillaries → blood goes back to the heart via venulesveins.

Single circulatory system: (e.g. in fish)

  • Heart pumps deoxygenated blood → gills.
  • Gaseous exchange (diffusion of CO2 from blood to H2O that surrounds the gills, and diffusion of O2 from H2O into the blood).
  • Blood leaves gills → rest of body → heart.

Double circulatory system (e.g. birds and mammals):

  • Right ventricle pumps deoxygenated blood to the lungs where it receives oxygen.
  • The oxygenated blood then returns to the heart to be pumped a second time ( by the left ventricle) out to the rest of the body.
  • Allows blood to travel around the bodies faster, delivering nutrients faster, so animal have a higher metabolic rate.
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Importance as a solvent in transport:

  • Has an uneven charge distribution, as the O  molecule is - and the H is + (Dipolar).
  • This means ionic substances (e.g. salt) dissolve easily as the ions are seperated due to the polar nature of water.
  • Hydrogen bonds form between the two molecules of H20 which creates cohesion.
  • This helps water to flow, making it good for transporting substances.
  • It takes a long time to heat and cool down water which means living organisms can survive as temperature fluctuations are small.


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Blood Vessels


  • THICK WALLS- Withstands high blood pressure
  • NARROW LUMEN- Blood flows under high pressure
  • ELASTIC FIBRES- Allows walls to strech when blood is pumped into the artery and recoil when the heart relaxes
  • SMOOTH LAYER OF ENDOTHELIAL CELLS- Low friction to ease blood flow

Vein :

  • VALVES- Stops backflow of blood
  • WIDE LUMEN- Blood flows under low pressure
  • RELATIVELY THIN WALL- Blood flows under low pressure


  • THIN WALL(ONE CELL THICK)- Allows rapid exchange between blood and tissues

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Cardiac Cycle

ATRIAL SYSTOLE- Pressure in the atria increases as they fill with blood. Increased pressure opens the atrioventricular valves allowing blood to enter the ventricles. The atria contracts to force remaining blood into the ventricles.

VENTRICULAR SYSTOLE- Ventricles contract from the base up, increasing the pressure and closing the atrio ventricular valves. The semilunar valves open and blood is forced into the atreries.

DIASTOLE- As the atria and ventricles relax, pressure falls. In the ventricles this causes closure of the semilunar valves. In the atria, blood id draen into the heart from the veins.

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Full Cardiac Cycle


  • Oxygenated blood drains into the left atrium from lungs along the pulmonary vein
  • Raising of blood pressure in the atrium forces open the left atrioventricular valve
  • Left atrial systole forces more blood through the valve
  • As soon as left atrial systole is over, the left ventricular muscles start to contract. This forces the left AV valve closed and opens the valve in the mouth of the aorta
  • Blood then leaves through the aorta to the body


  • Deoxygenated blood enters from the body along the vena cava
  • The right atrial muscle contracts and the right AV valve opens due to the pressure difference
  • The blood enters the right ventricle and it contracts, forcing the semilunar valve in the pulmonary artery open and the blood leaves through this valve along the artery into the lungs.
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Atherosclerosis: A disease that hardens the arteries, which leads to less elasticity and narrows the arteries due to the formation of plaque.

1. The endothelial lining becomes damaged for reasons such as high blood pressure or toxins from smoking

2. There is an inflammatory response and white blood cells move into the artery wall, cholesterol builds up which leads to a formation of atheroma

3. Calcium salts and fibres build up which leads to the formation of plaque and the artery narrows

4. The narrowing of the artery leads to high blood pressure, which means it is more likely for more plaques to form

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Blood Clots

Blood clots when it flows very slowly or when blood vessel walls are damaged.

1. Thromoboplastin is released from the damaged blood vessel.

2. Thromoboplastin triggers the conversion of prothrombin into thrombin (calcium and vitamin K is present in plasma).

3. Thrombin then catalyses the conversion of fibrinogen to fibrin.

4. The fibrin fibres tangle together and form a mesh in which platelets and red blood cells get trapped forming a blood clot.

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Monosaccharides- Single sugar unit e.g. alpha glucose, fructose and galactose.

Disaccharides- 2 sugar units bonded by glycosidic bonds e.g. 

  • Sucrose - (glucose + fructose) form in which sugar is transported in a plant
  • Maltose - (glucose + glucose) produced when amylase breaks down starch
  • Lactose - (galactose + glucose) the sugar found in milk

Polysaccharides- Long chains of glucose molecules e.g. Starch, glycogen

The bonds that form between monosaccharides are glycosidic bonds. In the reaction that forms a glycosidic bond there is a loss of one molecule of water, this is called a condensation reaction.

Hydrolysis breaks the glycosidic bond, adding back the water molecule.

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Starch and Glycogen

STARCH-Starch is the main energy storage material in plants. It is made up of a mixture of two molecules, amylose and amylopectin:

Amylose- a long, unbrached chain of glucose joined together by 1-4 glycosidic bonds. The angles of the glycosidic bonds give it a coiled structure. This makes it compact and good for storage. It is also insoulble water so it does not swell be osmosis.

Amylopectin- a long, branched chain of glucose joined by 1-4 and 1-6 glycosidic bonds. Its side branches allow the enzymes to get to the glycosidic bonds easily meaning that glucose can be released quickly.

GLYCOGEN-The main energy storage material in animals:

Its structure is similar to amylopectin. Loads of branches means that glucose can be released quickly. It is also a very compact molecule so it's good for storage.It is also insoulble water so it does not swell be osmosis.

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Lipids enhance the flavour and palatability of food.They are insoluble in water but soluble in organic solvents such as ethanol.

A triglyceride is made up of 3 fatty acids joined to 1 glycerol molecule. The fatty acid tails are hydrophobic which makes lipids insoluble in water.

When the molecules join together, a condensation reaction takes place and ester bonds are formed.

Saturated Fatty Acids: don't have any double bonds between the carbon atoms in their hydrocarbon tails. Every carbon is attached to at least two hydrogen atoms. The lipids are 'saturated' with hydrogen.

Unsaturated Fatty Acids: have double bonds between the carbon atom in their hydrocarbon tails. These double bonds cause the chain to kink. If they have two or more, the lipid is polyunsaturated.

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Risk Factors of CVD


  • Tendency to high blood pressure and poor cholesterol metabolism
  • Arteries that are more easily damaged
  • Mutations in genes that affect relative HDL:LDL levels in blood

Gender - Oestrogen can give women some protection

Ageing - Elasticity and width of arteries decrease with age

Diet - Saturated fats, cholesterol and lipoprotein levels

High blood pressure - should not be sustained 140/90

Smoking - chemicals physically damage artery linings and cause them to constrict

Inactivity - regular exercise reduces risk

Obesity - Increases rick of diabetes type II and CVD

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Population Studies

Sample Size- the greater the number of people used in a study, the more reliable the results.

Variables- the more variables that have been controlled in a study, the more reliable the results.

Data Collection- the less bias involved in collecting the data, the more reliable the results.

Controls- the presence of controls increases the reliability of the results.

Correlation- An increse in one is accompanied by an increase in the other.

Causation- A change in one is responsible for a change in the other.

Cohort studies

  • Large number of people followed for a long period of time and monitored to see if they develop the condition. Various risk factors the participant have been exposed to are looked at.

Case-control studies

  • A group with the condition (cases) is compared with a group who do not have it (control)
  • Past history is investigated to try to identify factors leading to one group having the disease and the others not
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Energy Budgets

Energy budget is a term used to describe the amount of energy taken in by an organism and the amount of energy used up by organisms.

If energy intake is higher than energy output, the excess energy will be turned into fat reserves by the body, so the person will gain weight.

If energy intake is lower than energy output, the body will have to get more energy by turning its fat reserves into energy, so the person will lose weight.

Energy input - Energy output = Energy budget

BMI = Body mass in kg / height in m (squared) 

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Cholesterol is not soluble in water. To be transported in the bloodstream it is combined with proteins to form soluble lipoproteins.

  • High-density lipoproteins: They are mainly protein. They transport cholestrol from body tissues to the liver where it's recycled or excreted. Their function is to reduce total blood cholestrol when the level is too high.
  • Low-density lipoproteins: They are mainly lipid. They transport cholestrol 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.

High total blood cholestrol level and high LDL level have both been linked to an increased risk of CVD.

Diet should be balanced; reduced cholesterol, saturated fats and salts; more polyunsaturated fats, including omega 3 fatty acids; more fruit + veg.

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Treatment for CVD

Antihypertensives- reduce high blood pressure. These drugs include:

  • Diuretics (which cause more urine to be produced, lowers blood pressure and volume)
  • Beta blockers (which reduces the strenght of the heartbeat)
  • Vasodilators (which widen the blood vessels)
  • Risks- Dizzieness, nausea, muscle cramps.

Plant Statins- lowers cholestrol level in the blood by reducing the amount of cholestrol absorbed from the gut. A lower blood cholestrol level reduces atheroma formation. Risks: they can reduce the absorption of some vitamins from the gut.

Anticoagulants- Reduces the formation of blood clots. These drugs include: warfarin, heparin. Risks: uncontrolled bleeding if pateint has wound.

Platelet Inhibitory Drugs(e.g.Aspirin) - Makes platelets less sticky. Risks: Rashes, diarrhaea, nausea.

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Daphnia Experiment

Daphnia are good for the experiment because they're transparent, so you can see their internal organs.

1. Make up a range of caffeine solutions of different concentrations and a control.

2. transfer one daphnia onto a cavity slide and place the slide under a microscope.

3. Place a small drop of caffeine solution onto the daphnia.

4. Count the number of heartbeats in 10 seconds and multiply by six to get bpm.

5. Repeat the experiment using a different concentration.

For: Very simple organism with basic nervous system.

Against: Any use of animals is wrong as we can't determine how much pain it feels.

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Vitamin C experiment

1. Make several vitamin C solutions of different, known concentrations.

2. Measure out a set volume of DCPIP into a test tube.

3. Titrate the vitamin C solution with the DCIPI and gently shake the tube.

4. When the solution goes from blue to colourless, the right volume of vitamin C has been added.

5. Repeat the experiment twice more, with the same solution and take an average.

6. Make sure all variables are constant e.g. same volume of DCPIP.

7. Use the results to make a calibration curve of DCPIP against vitamin C conc.

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