# The cardiovascular system

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1.

a) The name of the stage of the cardiac cycle shown in the diagram is systole.

b) Two reasons it is this stage are; the tricuspid valves are open allowing blood to flow into the ventricles and the semi lunar valves are still closed preventing blood flow into the aorta and pulmonary artery.

c) A function for part A on the diagram is to prevent backflow of blood from the ventricles back into the atrium.

A function for part B on the diagram is to contract to push blood out of the ventricle and into the pulmonary artery.

2.

a) At 0.1 seconds the pressure in the left ventricle increases from 0KPa to 15KPa by the time it reaches 0.3 seconds which is on the graph is shown as an almost vertical line demonstrating how much of a steep increase this is, the pressure then decreases just as quickly back down to 0KPa by 0.5 seconds. In comparison at 0.1 seconds the pressure in the right ventricle only increases by 5KPa so this is shown on the graph as a much more gradual increase but it does decrease back down to 0KPa in the same way the left ventricle does. This is then repeated at roughly 0.8 seconds.

b) At 0 seconds the pressure in the left ventricle is at 0KPa however at the same time the pressure in the aorta is at 11KPa, the aorta then shows a slight decrease down to 10KPa at 0.1 seconds. The pressure in both then increases to roughly 15KPa by 0.3 seconds, for the left ventricle this is shown as a much steeper increase than in the aorta. The pressure in the aorta then decreases to 14KPa at 0.4 seconds, it then gradually decreases to 10KPa between 0.4 seconds and 0.9 seconds. The left ventricle on the other hand shows a steep decrease to slightly below 0KPa between 0.3 seconds and 0.45seconds, this then increases to 0KPa by 0.8 seconds. The pressure in the left ventricle then rises to 15KPa once again by the time one second has passed, the pressure in the aorta then also increase to15KPa between 0.9 and 1 second.

c) The cardiac muscle is myogenic s they contract due to a pulse produced by a myocyte. The four parts of the heart that allow it to beat are the; sino-atrial node, atrioventricular node, the bundle of his and the purkine fibres. The SAN in the wall near the right atrium, it sends a signal across the atrium the walls of both contract generating pressure allowing the ventricle to fill with blood, this stage of the cardiac process is called atrial systole. The AVN which is located between the two atria picks up the signal released by the SAN after one second (the delay allowing the ventricles to fi with blood), the signal then travels down the bundle of his then travels throughout the purkine fibres which are located along the bottom of the ventricles. The fibres then contract once the atria have relaxed allowing the ventricles to push blood into the pulmonary artery and aorta. This stage is known as ventricular systole.

3. The higher the altitude the climber’s progress to, the higher the haemoglobin count in their blood. As the climbers progressed from 1000m to 1500m there was a change of 0.6g haemoglobin and when they climbed 2500m higher to 4000m there had been an increase of 3.4g. Between 4000m and 4500m there was an increase of 0.5g and from 4500m to 4600m there was a very substantial increase of 1.2g. These measurements seem to suggest that the higher the altitude the more haemoglobin is needed in the blood and the higher the altitude the more the mean level will increase.

4.

a) There is a higher fat content in lean lamb and pork compared with that of lean beef and chicken because it has higher energy content per KJ than lean beef and chicken.

b) Lean meat contains little vitamin D because vitamin D is stored in fat and lean meat has a very low fat content so cannot store a lot of vitamin D.

c) The difference in energy content is because energy comes from fat content and lean pork has a fat content of 7 whereas chicken only has one of 4 thus causing the difference in energy content by 107 per KJ, other than fat content they have the same iron and protein content.

5. Although it is required only in small amounts, iron is a component of melanin and this is the pigment which gives blood its colour. Without enough iron in the diet, a condition called anaemia may result. There are some foods such as red meat and fish, which are rich in iron.

6. Basal metabolic rate is the basic amount of energy needed so that normal functions can be maintained; it is measured whilst at rest. It is calculated from body temperature changes over a given period of time.

7.

a)

i) The minimum for a man of 170cm is 61 kg. The maximum is 74kg.

ii) BMI is used as an indicator for obesity as it was developed to classify normal ranges of body compositions and as it takes into account height it can use this to see if a person is overweight in proportion to their height.

b)

i) Males BMI is made up of more skeleton, skeletal muscle and non-muscle/lean tissue than a woman of the same BMI. A male’s skeleton makes up 7kg whereas a woman’s only makes up 5kg of her BMI. Lean tissue in a woman’s body makes up 16kg of her BMI however in a male it takes up much more, weighing 20kg. A man’s skeletal muscle weighs 28kg compared to a woman’s 18kg. However women’s BMI is made up of much larger amount of fat compared to men’s. A woman has 26kg of fat whereas a man only has 10kg.

ii) Differences in body composition could be caused by the different ways males and females store and burn fat, it may also be caused by the height and bone density displayed in the different genders, men on average are taller than women so this may contribute to their larger skeletal weight.

8.

a) Food is burnt in oxygen because oxygen is needed for it to burn as it causes an exothermic reaction to take place, the reaction to release CO2 will release a lot of energy in the form of heat.

b) To calculate the energy value of a food sample using a calorimeter the measurements that need to be taken are: weight of food sample, temperature at the beginning of the experiment and the temperature at the end of the experiment and then the difference in temperature.

9.

a) Carbon monoxide and nicotine put strain on the heart making it work harder and increasing the chances of blood clots.

b) People who are obese can reduce their body mass index by eating a balanced and calorie controlled diet and taking up physical exercise such as swimming.

10.

a) Pulmonary vein

b) The higher the individuals blood cholesterol it seems the higher the risk of a heart attack as demonstrated by the graph at 5 mmol dm-3 the number of people having heart attacks is about 3.5% whereas those with a blood cholesterol of 8mmol dm-3 and the percentage had risen to 10%.

c) On the graph it shows that the risk of a heart attack occurring is higher than that of non-smokers even when their blood cholesterol levels are the same. Although the higher the blood cholesterol levels get in both smokers and non-smokers the risk increases at roughly the same rate although the risk in smokers seems to increase slightly more than that of non-smokers each time the cholesterol levels increase. When the blood cholesterol level in both is at 5mmol dm-3 smokers have a slightly higher risk of 5% unlike non-smokers who have a risk of 3.5%. At 7mmol dm-3 the risk to non-smokers is roughly 7.5% but in smokers it is slightly higher at 12%. Finally at 8mmol dm-3 the risk to smokers is 18% whereas in non-smokers it is only 10%. This demonstrates that the risk of a heart attack is higher in smokers than non-smokers even those who have the same cholesterol levels.

d) A saturated fatty acid is a fatty acid whose carbon chain cannot absorb any more hydrogen atoms.

11.

Water has the chemical formula H20. Water molecules are described as diPolar and this is because they have a slightly positive charge at one end of the molecule and a slight negative charge at the other end. Therefore, the individual molecules form hydrogen bonds with each other. Water is an important element in all living organisms, because most biochemical reactions take place in aqueous solution. Water also has a high specific heat capacity, which means that its temperature remains stable despite changes in the temperature of the surrounding environment.

12.

a) Hydrogen bonds

b) Water molecules are described as dipolar because they have two poles as the oxygen is electronegative and the hydrogen is electropositive.

c) Water has a high specific heat capacity and this keeps the temperature of the water stable as it takes a lot of energy to change the temperature. This makes the sea able to support marine life as it minimises the fluctuation in the temperature of cells.

13.

Proteins are composed of long chains of monomers that are called Polymers. These are linked together by bonds, which are formed by reactions between adjacent monomers. The primary structure of a protein is the precise sequence of monomers in a polypeptide chain and thus determines secondary and tertiary protein structures. The secondary structure of a protein might be a type of coil known as an and this is held in this shape by the bonds called which are located between different monomers in the chain.

14.

b) Phospholipid

c) Condensation reaction

d) It only lets certain molecules such as oxygen the cell needs inside.

e) Phospholipids form a bilayer which forms a barrier around the cell with hydrophilic head on the outside and hydrophobic tails facing inwards.

15.

Blue to cloudy orange

Dilute HCL

Potassium iodide

Biuret

16.

High blood pressure- causes the arteries to harden and thicken restricting blood flow as the channel which it travels through is narrower.

Smoking- Nicotine in cigarettes can constrict the blood vessels whist the carbon monoxide can cause damage to the inner lining increasing the chances of atherosclerosis. As the blood flow is constricted this puts a strain on the heart increasing the chances of a heart attack.

High stress- This can cause the arteries to tighten, restricting blood flow to the heart and increasing the chances of a heart attack occurring. There is also an indirect way this can cause heart attacks, as emotional upset often causes people to take u smoking or eat more which both in themselves are risk factors for CHD.

High cholesterol levels- If there are high levels of cholesterol in the blood plaques and atheromas can form. High cholesterol levels can be caused by high levels of LDL’S and low levels of HDL’s. The levels of cholesterol in an individual’s blood can be cause by factors such as age, gender, diet etc.

Diabetes- in type 1 diabetes blood sugar levels are high which may lead to a build-up of plaque in the arteries restricting blood flow and increasing the risk to the individual of CHD. They also both have very similar risk factors such as obesity and high cholesterol.

17.

Quantitative research involves gathering numerical data, for example degrees or minutes whereas qualitative research involves looking at the quality of something for example colour or shape.

AS unit 1: Topic 2 Assignment B (TMA)

1. Enzyme activity is affected by the temperature of its surroundings; enzymes have an optimum temperature at which they work best which is 37.0°C any above or below this the activity of the enzyme will be affected. Too high above the optimum temperature the enzyme will denature as the active sites of the molecules change shape making them less complimentary to the substrate molecules so they will not be able to fit together. Too far below the optimum temperature and the amount of kinetic energy possessed by the molecules will be too low for many reactions to take place between the active sites and the substrate molecules as there will be too few random collisions. Enzyme activity can also be affected by pH; different molecules have different optimum pHs but in all of them it is the pH where there shape is most complementary to the substrate molecules and significant changes in this pH can cause the enzyme to denature but only small changes will not cause permanent damage as the bonds within them can be reformed but it will cause a large decrease in the number of successful collisions. The concentration can also affect the activity as the more substrate and enzyme molecules there are the more random collisions will take place causing he reaction however here must be enough substrate to React with the enzyme as otherwise the rate will go down as the enzyme has nothing to bond to. The presence of inhibitors will also affect the enzyme activity as they can sometimes stop them working all together as they occupy the active site and stop substrate from binding there or they occupy another space on the molecule which causes the active site to change shape meaning I will no longer be complimentary to the substrate preventing them from binding.

2.

Catalysts

Energy

Substrate

Active site

Temperature

Decrease

3.

a) Osmosis is the diffusion of water molecules from an area of low concentration to an area of high concentration down a gradient and through a semi-permeable membrane.

b) Facilitated diffusion is the transport of substances across a membrane by a Tran’s membrane protein molecule, either by channel proteins or carrier proteins.

4.

a)

i) Four

ii) A sequence of codons in an MRNA molecule specifies the genetic code.

b)

i) UAC- AUG

ii) The role of TRNA molecules in the process of protein synthesis is to recognise specific codons and then once that is recognised deliver the corresponding amino acid. Each tRNA molecule can only carry one amino acid so there are many different types within the cell to covalently bond to and carry the different types of amino acids to bind to each codon.

5.

a) A gene is a section of DNA which encodes a protein whereas an allele is a version of a gene.

b)

i) Person 1: I0 I0 (OO)

Person 2: IA IB (AB)

Person 4: IA IO (AO)

Person 5: IB IO (BO)

Person 6:IB IB (BB)

ii) O as person 7 also has the blood type O so it would make sense for it to be inherited from the above generation as it could not be from either parents as the blood type is not present even as a recessive allele.

6. The large number of alveoli on the surface of the lung and the fact that they are folded increases the amount of gas which can diffuse in and out of the lung at any given time, increasing gas exchange rate. The walls of the alveoli are only one cell thick thus creating only a small diffusion distance for the gases to travel across making diffusion quicker and easier. Gases need to travel through a concentration gradient from an area of high concentration to an area of low concentration so it is important that the concentration gradient is maintained in order for the gases to diffuse, if it is not maintained gas exchange may not take place.

7.

a) To produce cell B meiosis must have occurred because four cells have been produced whereas mitosis only produces two and there Is only half the number of chromosomes than in the original cell which is common in meiosis whereas in mitosis there is another full set created.

b) For chromosome P to appear so different, a mutation must have occurred causing two of the chromosomes from the original cell to combine.

c) In the human male this type of cell division would take place in the testes.

8. Most cell surface membranes have the same structure which is the fluid mosaic model which is a sea of phospholipids with protein molecules floating between. They are arranged into a bilayer with the phospholipids having hydrophilic heads and hydrophobic tails so the heads are in contact with the cytoplasm. The proteins then line the pores within the bilayer and as they are polar this means substances cannot get through the layer but can still move from one side of the membrane to the other. Attached to the outside of the membrane there are short polysaccharide chains with the carbohydrates being attached to the proteins and being called glycoproteins. They aid interaction with other cells and recognise foreign molecules and hormones when they reach the cell membrane.

There are different types of proteins within the bilayer including channel proteins which create small gaps for molecules to diffuse through, carrier proteins which bring different molecules from outside the cell to inside of it, receptor proteins which start chemical reactions, cell recognition proteins and enzymatic proteins which carry out metabolic reactions. There is also cholesterol to strengthen the bilayer and glycolipids which signal molecules.

The cell membrane has many functions which include it being a semi-permeable barrier which controls what substances enter and exit the cell, they structurally support the cell and its organelles keeping them in place so the cell can function correctly. Cell surface membranes can also sometimes aid the cell in movement for example with amoeba and is quite importantly a site where many chemical reactions take place.

9. Deoxyribonucleic acid (DNA) is a macromolecule which is a large molecule which is built up of sub-units, the DNA then forms a double helix shape which gives the DNA stability and strength but also allows it to be quite flexible. The DNA is in a shape similar to a ladder which means it has ‘rungs’ which is where the complementary four bases meet up and carry different genetic information creating a genetic code. The four bases used are adenine, thymine, cytosine and guanine.

When a cell divides, first its nucleus has to do so and the first stage of this is the DNA replicating. The two strands of DNA then separate under the influence of enzymes and then each strand remains along its length as they are both joined strongly. Each strand then gets rebuilt by a complementary strand replacing the original strand it separated from. Complementary bases fit together which is adenine with thymine, guanine with cytosine, thymine with adenine and cytosine with guanine. Two identical strands of DNA are the result of this.

10.

a) Evidence that suggests the allele is recessive is the fact that no one is affected until the third generation and even then it is only two children from one couple that are affected suggesting that both the parents are carriers of the recessive gene. The fact that it has occurred in both a male and a female suggests it is an autosomal allele.

b)

i) 2

ii) The significance of the heterozygous genotype of cystic fibrosis in the population is that the more there are the more people will become carriers of the disease and the more likely two people who are both carriers and don’t know it will have a child who has the disease.

c) Cystic fibrosis is the result of a recessive gene which does not become evident until two carriers have a child together. To determine whether a person is a carrier of the disease a mouthwash test can be used which collects samples of cells from the mouth which is then tested for the CF gene.

11.

A) 1- Transcription , 2- Translation

b) Ribosomes

c) The TRNA brings the amino acids to the ribosomes and the one that has the correct anticodon has its amino acid attached to the growing polypeptide.