Topic One - Lifestyle, Health and Risk


Why animals have a heart and circulation

Single celled organisms - raw materials can diffuse directly into the cells across the cell surface membrane. The diffusion rate is faster because of the short diffusion pathway

Multicellular organisms - The diffusion pathway is too large, because of this multicellular organisms have a mass transport system. In mammals, the mass circulatory system is the circulatory systemwhere the heart pumps the blood around the body. This allows raw materials to be carried to organs, and metabolic waste to be removed.

Mass flow - movement of fluid in one direction

Mass transport - The means by which the materials are moved

Open circulatory system - blood flows directly into cavities making direct contact with tissues

Closed circulatory system - blood is carried through vessels either as a double or single circulatory system (how many times it passes through the heart)

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Importance of water

Many biological reactions take place in solutions so water is essential. It is also important to transport solvents around plants and animals.

  • Water molecules have a dipolar structure. The hydrogen atoms are slightly positively-chargd which attacts them to the negatively-charged oxygen atom. The attraction is called hydrogen bonding as many water molecules bind together.
  • Water molecules have a high cohension. This helps the water to flow as it creates an unbroken chain. There is also high adhesion in water where molecules stick to other surfacesto travel up xylem.
  • Water is a great solvent. Its dipolar nature means it is attracted to both negative and positive ions. Once the ion is surrrounded, they dissolve
  • Its thermal properties are high specific heat capacity, high latent heat of evaporation (it takes a lot of energy to heat water by 1 degree and to evaporate water) as well as a high latent heat of fusion. This means that organisms can survive in the cold without freezing.
  • Water is transparent so water plants can receive light for photosynthesis. Water has a low compressability which allows buoyancy. Ice forms on the surface which allows organisms below to survive (ice has a lower density meaning molecules are closer together)
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Structure of blood vessels

The heart pumps blood around the body through blood vessels.

  • Arteries carry blood from the heart to the body. They have thick muscular walls and elastic fibres within the walls to cope with high pressure. The inner endothelium lining is folded to allow expansion
  • Veins carry blood back to the heart from the body. They have a wider lumen with less elasic fibres as there is a lower blood pressure. Veins contain valves which stop the blood flowing backwards
  • Capillaries are small blood vessels. This is where metabolic reactions occur from tissues and blood. Capillaries are spread into networks which increase the surface area. The walls are only one cell thick which allows efficient diffusion in and out of the cells
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Cardiac cycle

Stage 1 - Ventricular and atrial diastole (blood fills up both ventricle and atrium)

Stage 2 - Atria systole (blood forced into ventricle)

Stage 3 - Ventricular systole (blood is pushed up through the arteries

Structure - the left side of the heart has thicker walls than the right to contract powerfully and pump blood around the body. Ventricles have thicker walls than the atria as they have to push blood a further distance. AV (atrioventricular) vlaves connect atria to ventricles to stop blood flowing backwards. SL (semi-lunar) valves link arteries to the ventricles to stop blood flowing back into the heart 

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Events leading to atherosclerosis

Atheroscelerosis is a build-up of fatty acids in the arteries

1. Endothelium in artery wall is damaged

2. Inflammatory response - white blood cells deposit cholestrol. This causes a fatty deposit to form (atheroma)

3. Calcium salts and fibrous tissues build up which forms hard deposits called plaque

4. Blood pressure increases, increases chance of blood clot as a positive feedback system occurs as there is a higher chance of daage and therefore plaque formation

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Blood-clotting process

Thrombosis - blockage of arteries through the formation of a blood clot

1. collagen fibresa are exposed in damagd blood vessels. contact with collagen leads to activation of platelets.

2. Platelets stick to exposed collagen and form a platelet plug. Platelets release thromboplastin.

3. Thromboplastin catalyses the formation of thrombin from prothrombin.

4. Thrombon catalyses the formation of fibrin from fibrinogen.

5. Fibrin mesh is formed.

6. Red blood cells and platelets are trapped in the fibrin msh creating blood clots.

Blocked arteries can lead to stroke, heart attack or aneuryism (blockage leading up to the heart, in the brain or rupture leading to massive blood loss.

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Risk factors of CVD

Genetics - some genetic conditions are passed down through parents. Defects in the heart e.g damaged septum increase CVD risk. If a family member have been diagnosed with CVD.

Diet - being overweight increases your risk of diabetes and high blood pressure which are both CVD risk factors

Age - risk increases as you get older for both me and women. It increases massively for women after menopause. The difference between men and women decreases as age increases

Gender - Men are at a higher risk than women of CVD. Women are protected by hormones such as oestrogen

High blood pressure - high pressure damages the endotelium of the arteries. as you get older, arteries lose elasticity

Smoking - smoking damages your arteries and increases fatty deposits. Blood pressure is also raised

Inactivity - leads to high blood pressure and cholestrol levels

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Correlation and causation

Correlation - a relationship/pattern between two things. Requires knowlede of mechanism for how one variable affect another.

Causation - Change in one variable is responsible for the change in the other. Rquires controlled experiements to see if change one variable has the predicted effect.

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Risk factor studies

Types of study

Cohort study - prospective study where a group of people are followed over time to see who develops the disease

Case controlled study - retrospective study where a group of people with a disease are compared with a group who do not have the disease.

The groups selected should be representative of the entire population.

Reliability - results can be consistently reproduced

Validity - results are an accuate answer

Biases include:selection bias (pick unrepresentative people), recall bias (inaccurate recollection of past events), loss to follow up (exposure increases the risk of participants dropping out skewing comparisons).

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Perception of risk

Risk = number of people with unwanted outcome

           total people taking the risk

People overestimate risk because: it was undertaken involuntarily, unnatural, unfamiliar, feared, unfair, rare, consequences are sudden.

People underestimate risk because: it was undertaken voluntarily, natural, familiar, not feared bt enjoyed, fair, common and consequences are long term

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Energy budgets and diet

Energy budgets - 

Balanced (normal weight) energy input = energy use

Unbalanced (underweight) energy input < energy output

(illness, eating disorder) (excessive exercise)

    (overweight) energy input > energy output

(overeating)    (low exercies)

Our weight depends on our energy use and our energy input.

BMI = Weight (kg)

  Height (m^2)

An alternative is the hip to waist ratio - height is compared to the size of your waist.

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Monosaccharides, dissaccharides and polysaccharide

Monosaccharides - Cn(H2O)n is the most simple type of carbohydrate. Its soulbe in water as hydroxyl groups form hydrogen bonds between them. Used as compentents of DNA, RNA and as part of respiration. They can be in the form of ketones (double o bond) and aldehydes (double o bond with added H)

Disaccharides - Cn(H2O)n-1 are two monosaccharides joined together. They are used as an energy store and as transportation through xylem.

Polysaccharide - Polysaccharides are made up of many monosaccharides joined together. They can be both branched and unbranched depending on the position of the glycosidic bonds. These are mainly used for storing energy.

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Joining of monosaccharides

Monosaccharides are joined together through a condensation reaction to create disaccharides. During this process, the hydroxyl group from one molecule binds to the hydrogen of another, releasing water as a biproduct. This forms a covalent bond between the two as they share the oxygen of the hydroxyl group. This type of covalent bond is known as a glycosidic bond

e.g. Glucose + fructose = sucrose                Glucose + glucose = maltose

Glucose + galactose = lactose.

The formation of polysaccharides is the same with glycosidic bonds connecting each of the monosaccharides. The polysaccharides become branched depending on the position of the bond between the two monomers

e.g amylose has alpha (1-4) glycosidic bonds between two glucose monomers. Cellulose is alsounbranched and is made up of beta (1-4) glycosidic bonds

Amylopectin has alpha (1-6) and (1-4) glycosidic bonds.  Glycogen has a similar strucutre to amylopectin but has more branches within the structure.

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The most common type of lipid is a triglyceride. They're composed of 3 fatty acid chains attached to a glycerol backbone. Fatty acids are chains of carobn atoms with a carboxyl group at the end. The gylcerol backbone becomes attached to the fatty acids through condensation reactions which produce water. The bonds that form between them are known as ester bonds.

These triglycerides can be unsaturated (carbon double bond present) or saturated.

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Blood cholestrol levels

Lipoproteins are insoluble cholestrol (fatty acids) combined with proteins.

Can be in two forms: High denisty Lipoprotein HDL, or Low Density Lipoprotein LDL.

HDLs carry cholestrol away from the cells to the liver where it is broken down or passed as waste.

LDLs carry cholestrol to the cells that need it to maintaon cell membranes.

Anti cholestrol drugs reduce the levels of LDLs in the liver as there are known as the bad type of cholestrol

Healthy level of cholestrol consist of

LDL - 3mmol/l

HDL - above 1mmol/L

High levels of LDLs can build up fatty acids within your arteries and increase your risk of CVD

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Use of scientific knowledge

There are various ongoing studies to reduce the risk of CVDs and other coronary heart diseases. Scientific studies have confirmed that change in lifestyle can reduce the risk of heart dieases Diet rich in saturated fats increase the risk.

Obese people also have highr risk of CVDs. There are tow obesity indicators such as BMI (Body Mass Index) and Waste to Hip Ratio.

BMI = Body Mass (kg) / Height (sq m)

Waist to Hip Ratio = Waist (cm) / Hip (cm)

A normal adult has BMI between 18 and 25.

Smoking is also related to high CVDs risk. People are advised to either quit smoking or use nicotine patches to reduce the risk.

Research also confirms that exercies is the best way to prevent CVDs.

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Investigate the effect of caffeine on heart rate i

Independent variable - caffeine concentration

Dependent variable - heart rate of daphnia

Control variables - temperature, volume of solutions, stress of daphnia, size of daphnia, time to acclimatise

Remove daphnia with a pipette and place on a cavity slide with cotton wool on a microscope. Dab around the daphnia to remove excess water left. Replace the water with the caffeine solution with each concentration. Leave the daphnia for 5 minutes to acclimatise. Then count the heart rate for 15 seconds on a piece of paper. Times by 4 to get heart rate for 60 seconds.

Repeat across the different caffeine concentrations (0M, 0.2M, 0.3M, 0.4M and 0.5M)

This is the most ethical way as they reproduce asexually, they have a less developed nervous system so do not feel pain. They are transparent under the microscope so the heart is visable which avoids the need of dissection.

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Ethical issues

Use of invertebrates and other small animals allow for symptoms and side effects to be tested first before it is tested on a human. This means we can have many medical advances tested before humans ahve to suffer

To some this is unethical as we have no consent and cannot truly rule out no pain or discomfort.

Invertebrates are simple organisms with many similairties to humans which makes test results likely to be reflective

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Investigate the vitamin c content of fruit juice

Independent variable - type of fruit juice

Dependent variable - volume of juice (cm3) require to decolourise 1cm3 of DCPIP

Control variables - temperature, concentration of DCPIP, volume of DCPIP, same end point colour, sake each tube the same amount of times

Pipette 1cm3 of 1% DCPIP into a conical flask. Fill up a burette with distilled water to rinse it out. Empty into a  seperate flask and then refill with the first type of fruit juice. SLowly add the juice drop by drop, swirling tohe contents as you do so. Close the tap as soon as it loses its colour and note the end value. Repeat again at least 3 times, as you get closer to the end value add the juice into the flask in smaller volumes to get concordant results of when the DCPIP loses its colour. Repeat for all other concentrations (0% vitamin c, 1%, 2%, 3%, 5% and 10%)

Mass of vitamin c in fruit juice = mass of Vit C to decolourise 1cm3 of DCPIP x volume of sample required to decolourise 1cm3 of DCPIP

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benefits and risks of treatments for Cardiovascula

Antihypertensives - these medicines are used to reduce high blood pressure. These include beta-blockers and vasodilators. These drugs reduce the amount of sodium in the blood.

They reduce the risk of atheromas and blood clotting. These also increase the rate of heart beat, headache and drowsiness.

Statins - These reduce the choletrol level in blood. These reduce the risk of CVDs.

These also include side effects such as muscle pain, diabetes, headahces and nose bleeding.

Anticoagulents - These reduce the blood clotting.

These reduce the risk of VD such as atheromas. These include the risk of excessive bleeding, allergic reactions, swelling et.

Platelet Inhibitory Drugs - These include drugs such as aspirin. These are anticoagulant.

They have side effects of rashes, nausea, excessive bleeding

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