Topic 7: Run for your life

Question 1

Tendon

Answer 1

Non-elastic tissue which connects muscle to bone.

Question 2

Ligaments

Answer 2

elastic tissue that joins bone together & determines the amount of movement possible at a joint.

Question 3

Joints

Answer 3

The area where two bones bone are attached for the purpose of permitting body parts to move. They’re made of fibrous connective tissues & cartilage.

Question 4

Skeletal muscles

Answer 4

Muscles attached to bones, they are arranged in antagonistic pairs.

Question 5

Antagonistic muscle pairs

Answer 5

Pairs of muscles which pull in opposite directions - as one muscle contracts (the agonist), the other relaxes (the antagonist). Extensors act to straighten the joint, while flexors act to bend the joint.
Examples:
When the triceps (the extensor) relaxes, the biceps (the flexor) contracts to lift the arm.
When the quadriceps (the extensors) relax, the hamstrings (the flexors) contract to bend the leg.

Question 6

Muscle fibre structure

Answer 6

• sarcolemma = Cell membrane
• sarcoplasm = cytoplasm
• T-tubules = Inward folds of the sarcolemma across the muscle fibre, which stick into the sarcoplasm. Help to send electrical impulses through the sarcoplasm so they reach all parts of the muscle fibre.
• Sarcoplasmic reticulum = internal membranes running through the sarcoplasm. Store & release calcium ions needed for muscle contraction.
• mitochondria = provides ATP needed for muscle contraction
• multinucleate
• contain myofibrils = long, cyndrical organelles made of proteins. Highly specialised for contracion.

Question 7

Myofibril structure

Answer 7

Contain bundles of thick and thin myofilaments, which move past each other to make muscles contract:
- Thick myosin filaments - dark bands
- Thin Actin filaments - light bands

Areas of a myofibril:
H band - area containing only thick myosin filaments
I band - Only thin actin filaments present
A band - Contains areas where only myosin filaments are present & areas where myosin & actin overlap
M line - Middle of myosin filaments
Z line - Attchments for actin filaments. Mark the ends of each sarcomere. Sarcomeres are joined lengthways at their Z-lines.
Sarcomere - The section of a myofibril between two Z-line.

Question 8

What happens to the bands when a sarcomere contracts?

Answer 8

Myosin and actin filaments slide over one another to make the sarcomere contract. As a result:
- I band gets shorter
- H zone gets shorter
- A band stays the same length
- Sarcomere gets shorter

Question 9

Muscle contraction: Sliding Filament Theory

Answer 9

1. Calcium ions released from sarcoplasmic reticulum (SR) upon nervous stimulation (arrival of an AP at neuromuscular junction). Bind to troponin molecule - changing its shape.
2. Myosin binding sites exposed, myosin head moves forward to form an actomyosin cross bridge.
3. ADP + Pi released, myosin head moves forward, pulling the actin filaments and shortening the sarcomere.
4. Free ATP binds to myosin head , myosin head changes shape and detaches from actin filament.
5. ATPase in myosin head hydrolyses ATP (to ADP+Pi), which causes myosin head to move back to its original position - recovery stroke.
6. Repeated stimulation, the presence of calcium ions and ATP causes continued contraction - myosin head re-attaches further along the actin filament and the cycle repeats.
7. If stimulation is stopped, ATP released is used to actively transport Ca2+ ions back into the sarcoplasmic reticulum. Actin filaments slide back to their relaxed position, which lengthens the sarcomere.

Question 10

Fast twitch muscle fibres

Answer 10

• Short contraction-relaxation cycle.
• Fewer capillaries & low amounts of myoglobin - appear lighter
• ATP supplied mostly from anaerobic respiration
• Fewer, smaller mitochondria present
• Large store of calcium ions in the sarcoplasmic reticulum
• Large amounts of glycogen & phosphocreatine present
• Faster rate of ATP hydrolysis in myosin heads
• Fatigue rapidly due to greater lactate formation

Question 11

Slow twitch muscle fibres

Answer 11

• Long contraction-relaxation cycle
• Denser network of capillaries, high amounts of myoglobin and haemoglobin - appear dark red
• ATP supplied mostly from aerobic respiration
• Many large mitochondria present
• Small store of calcium ions in the sarcoplasmic reticulum
• Small amounts of glycogen present
• Slower rate of hydrolysis in myosin heads
• fatigues more slowly due to reduced lactate formation

Question 12

Summaries the stages of aerobic respiration

Answer 12

1. Glycolysis - phosphorylation & splitting of glucose - occurs in cytoplasm.
2. Link reaction - Decarboxylation & dehydrogenation of pyruvate - occurs in matrix of mitochondria.
3. Krebs cycle - cyclical pathway with enzyme controlled reaction - occurs in matrix of mitochondria.
4. Oxidative phosphorylation - production of ATP through oxidation of hydrogen atoms - occurs in innermembrane of mitochondria.

Question 13

Glycolysis

Answer 13

1. Phosphorylation of glucose
   - Requires 2 ATP molecules to provide phosphates and produces 2ADPs and 2 triose phosphates.
2. Oxidation of triose phosphate
   After triose phosphate loses hydrogen, it forms two molecules of pyruvate.
   The hydrogen ions are collected by NAD which forms two reduced NAD.
   Triose phosphates are dephosphorylated
   4ATPs are produced but 2 were used in phosphorylation of glucose meaning there is a net gain of 2ATP molecules.

Question 14

Aerobic respiration

Answer 14

Aerobic respiration is the splitting of a respiratory substrate, including glucose, reuniting hydrogen with atmospheric oxygen to release a large amount of energy and carbon dioxide as a waste product. It is a multi-step process, with each step controlled and catalysed by a specific intracellular enzyme. It yiels ATP, which is used a source of energy for metabolic reaction.

Question 15

Link reaction

Answer 15

1) Pyruvate (3C) is decarboxylated (one carbon atom is removed in the form of CO2)
2) Pyruvate is oxidised/dehydrogenated, changing into acetate (2C). NAD collects the hydrogen atom from pyruvate becoming reduced NAD.
3. Acetate combines with coenzyme A (CoA) to form acetyl conenzyme A (acetyl CoA).

Occurs 2x for every glucose molecule.

Question 16

Krebs Cycle

Answer 16

In the mitochndrial matrix:

1. Acetyl CoA (2C) enters the krebs cycle and acetyl is accepted by the four carbon compound oxaloacetate (4C) to form citrate (6C). CoA is released and reused in the link reaction
2. 6C citrate is converted to a 5C molecule
   - Decarboxylation of citrate releases CO2 as a waste.
   - Oxidation (dehydrogenation) of citrate, releases a H atom that reduces NAD.
3. 5C molecule converts back to oxaloacetate (4C)
   decarboxylation & dehydrogenation occur sagain, producing 1reducedFAD and 2reducedNAD.
   Substrate-linked phosphorylation occurs when a phosphate is transferred from an intermediate compound to ADP, forming 1ATP to supply energy.

Total products:
1xCoA
Oxaloacetate
2xCO2
1xATP
3xreducedNAD
1xreducedFAD

Question 17

What is substrate level phosphorylation

Answer 17

Substrate level phosphorylation is when ATP is produced due to a phosphate group from an intermediate compound being directly transferred/added to ADP.
(when a phosphate group is directly transfered from one molecule to another).

Question 18

Oxidative phosphorylation

Answer 18

The process in which ATP is synthesised via chemiosmosis in the electron transport chain.

1. Reduced coenzymes carry hydrogen ions and electrons to the electron transport chain, which occurs on the inner mitochondrial membrane.
2. Hydrogen atoms are split into protons & electrons: H > H+ + e-
3. Electrons are carried from one electron carrier to another is a series of redox reactions (the electron carrier which passes the electron on is oxidised, whereas the electron carrier which receives it is reduced).
4. protons are actively transported across the membrane into the intermembrane space - using the energy released for the redox reactions. As a result, the concentration of protons in the intermembrane space is high.
5. The protons return to the matrix via facilitated diffusion through the channel enzyme ATPsynthase.
6. The movement of protons down their electrochemical gradient provides energy for ATP synthesis, which occurs on stalked particles using ATP synthase.
7. oxygen acts as the ‘final electron acceptor’ and combines with protons and electrons at the end of the ETC to form water.

Question 19

Work out how many molecules of ATP can be made from one glucose molecule during aerobic respiration

Answer 19

• 3ATP are made from each reduced NAD
• 2ATP are made from each reduced FAD

Glycolysis = 2ATP
Glycolysis = 2reducedNAD = (2x3) = 6ATP
Link Reaction (x2) = 2reducedNAD = (2x3) = 6ATP
Krebs cycle (x2) = 2ATP
Krebs cycle (x2) = 6reducedNAD = (6x3) = 18ATP
Krebs Cycle (x2) = 2reducedFAD = (2x2) = 4ATP

Total ATP = 38

Question 20

Describe the effect of metabolic poisons such as carbon monoxide on aearobic respiration

Answer 20

Some metabolic poisons target electron carriers in oxidative phosphorylation, preventing them from passing on electrons down the electron tansport chain. This stops chemiosmosis. There’s no energy released to phosphorylate ADP/produce ATP, consequently ATP synthesis in the cell is hugely reduced.
Reduced NAD and FAD are no longer oxidised, so NAD and FAD aren’t regenerated for the krebs cycle, causing the kreb cycle to also stop.

Question 21

Why do the link reaction and the kreb cycle occur in the mitochondria when glycolysis occurs in the cytoplasm?

Answer 21

The matrix contains all the enzymes necessary (I.e coenzyme A) for the biochemical reactions involved in the link reaction and kreb cycle.

Question 22

Core practical 16: Investigate the rate of respiration
1) Describe how a respirometer works
2) What is the control for this practical?
3) How do you find the volume of oxygen consumed using a respirometer?
4) How can the volume of carbon dioxide produced be found?
5) How is the rate of respiration calculated using data from the respirometer?
6) State the hazard andsafety precaution involved in the practical

Answer 22

1) It is a chamber/test tube connected to a capillary tube with a drop of dye. As the organism in the chamber respires and uses oxygen, the pressure decreases and the liquid moves in the capillary.
2) Replace the organism with an inert object of the same mass.
3) Place a fixed mass of soda lime in the respirometer with the organism. Measure the distance moved by the dye, and use the formula: volume = distance X πr^2 (area of respiratory tube)
4) Perform two set-ups, one with soda lime (A), and one without (B). Find the volume of gas used in a given time. Volume of carbon dioxide: Volume of A - Volume of B
5) Rate = Volume of oxygen used / mass of organism / time
6) The soda lime is corrosive. Wear eye protection and handle with gloves.

Question 23

During exercise muscles contract more frequently and need more energy. This requires an increas in aerobic respiration to take in more oxygen and remove more CO2. How does the body do this?

Answer 23

• By increasing breathing rate and depth - to obtain more O2 and remove more CO2.
• Increasing heart rate - to deliver O2 (and glucose) to the muscles faster and remove extra CO2 produced by the increased rate of respiration in muscle cells.

Question 24

Explain how breathing rate is controlled

Answer 24

1) The inspiratory centre in the medulla oblongata sends nerve impulses to intercostal and diaphragm muscles to make them contract.
2) This increases the volume of the lungs, which lowers the pressure in the lungs to slightly below atmospheric pressure. (The inspiratory centre also send nerve impulses to the expiratory centre to inhibit it).
3) Air enters the lungs due to the pressure differnece between the lungs and air outside.
4) As the lungs inflate, stretch receptors in the lungs are stimulated. The stretch receptors send nerve impulses back to the medulla oblongata and inhibit the action of the inspiratory centre.
5) The expiratory centre (no longer inhibited) then sends nerve impulses to the diaphragm and intercostal muscles to relax. This causes the lungs to deflate, expelling air. As the lungs deflate, the stretch receptors become inactive. The inispiratory centre is no longer inhibited and the cycle starts again.

Question 25

Explain the effects of exercise on breathing rate

Answer 25

1) The **extra CO2 **that is produced due to the increase in rate of respiration during exercise dissolves in the blood to form carbonic acid, which dissociates into hydrogen ions (H+) & hydrogencarbonate ions (HCO3-).
2) The increase in the concentration of H+ ions decreases the pH of the blood (it becomes more acidic)
3) The decrease in pH is detected by chemoreceptors (receptors that sense chemicals and are located in the medulla oblongata, the aortic bodies, and carotid bodies).
4) This stimulate chemoreceptors to send nerve impulses to the ventiliation centre in the medulla oblongata , which sends more frequent nerve impulses to the intercostal & diaphragm muscles to increase the rate & strength of contractions.
5) This increases the rate & depth of breathing, causing gaseous change to speed up. The CO2 levels drop and extra O2 is supplied for the musclees - the pH returns the normal and breathing rate decreases.

Question 26

Define the term ‘ventilation rate’ and describe how exercise effects it

Answer 26

Ventilation rate is the volume of air breathed in or out in a period of time, e.g. a minute.
It increases during exercise because breathing rate and depth increases

Question 27

What is the function of a spirometer?

Answer 27

Measures breathing respiration

Question 28

i) Define ‘Tidal Volume’
ii) How is it found using a spirometer?

Answer 28

i) Tidal volume = The volume of air that is breathed in or out during normal breathing (at rest).

ii) It is the distance from peak to trough when the participant is breathing normally.

Question 29

i) Define ‘vital capacity’
ii) How is it found using a spirometer?

Answer 29

i) Vital capacity is the maximum volume of air that can be breathed in and out of the lungs.

ii) The distance from peak to trough when the participant a forced deep breath.

Question 30

i) Define ‘respiratory minute ventilation’
ii) How is respiratory minute ventilation found?

Answer 30

i) Respiratory minute ventilation is the volume of air that can be breathed in or out in a minute and can be calculated by:
ii) Breathing rate X Tidal volume

Question 31

i) Define ‘Breathing rate’
ii) How is it found using a spirometer?

Answer 31

i) Breathing rate = The number of breaths taken in one minute (one breath = taking air in & breathing it back out again)
ii) To calculate the breathing rate, count the number of peaks on the trace in a minute.

Question 32

i) Define ‘oxygen consumption’
ii) How is it found using a spirometer?
iii) Explain what happens to the oxygen consumption during exercise?

Answer 32

i) The volume of oxygen used up by someone in a given time.
ii) O2 consumption is the slope of the spirometer trace and an be worked out by calculating the gradient: the change in the volume of gas in the spirometer over a period of time and divide this value by the time taken.
iii) The gradient is steeper during exercise because the air breathed into the spirometer has the Co2 removed by the soda lime; the oxygen is used for aerobic respiration.

Question 33

What happens to the tidal volume, vital capacity, breathing rate, and respiratory minute ventilation after exercise? Explain why these changes occur.

Answer 33

Tidal volume increases, vital capacity stays the same, breathing rate increases, respiratory minute ventilation increases.
This is because respiration increases during exercise because of increased muscle contraction. Therefore, more oxygen is required and more carbon dioxide is produced, so breathing rate, tidal volume and therefore respiratory minute ventilation increases to cope with this demand up to the maximum aerobic rate. After this point, minute ventilation will plateau to a maximum and
further respiration will be anaerobic.

Question 34

Core Practical 17: Investigating the effects of exercise
i) What is the canister of soda lime used for?
ii) What are the ethical concerns for this practical?

Answer 34

i) The soda lime is used to remove CO2 from the exhaled air. This allows for the volume of oxygen in the chamber to be measured & prevents the participant from inhaling CO2, which can cause respiratory distress as less oxygen is inhaled.
ii) Informed consent of the participant must be obtained, and the participant should be able to stop at any time during the practical.

Question 35

Core Practical 17: Outline a method to Investigating the effects of exercise and give two safety hazards

Answer 35

1. A person at rest will breathe into the spirometer for one minute
   Record the results.
2. The person will then exercise for two minutes while the spirometer chamber is refilled with oxygen.
3. After they stop exercising, they will immediately breathe into the spirometer for one minute
4. Record the results
5. Compare the recordings taken before and after exercising
   Disinfect mouthpiece and calibrate the equipment

Safety Hazards:
Disinfectant - flammable -Keep away from naked flame
Soda lime - corrosive - eye protection, avoid skin contact
Spirometer - breathing/circulatory problems - don’t use with breathing/circulatory issues

Question 36

Negative Feedback Loops

Answer 36

Self-regulatory mechanisms return the internal environment to optimum when there is a fluctuation.
Negative feedback loops counteracts any change in internal conditions. This means that all changes are reversed to restore the optimum conditions.

Example:
Regulation of blood glucose levels. When blood glucose levels rise, the pancreas releases insulin, which takes up glucose from the blood, decreasing glucose levels back to a stable level.

Question 37

Positive Feedback Loops

Answer 37

A fluctuation, which triggers changes that result in an even greater deviation from the normal level (increases the original change in the conditions).

Example:
Childbirth - as the baby moves down the birth canal, pressure on the cervix increases, stimulating the release of oxytocin, Oxytocin causes the uterus to contract, which further increases pressure on the cervix, leading to even more oxytocin release & stronger contractions.

Question 38

What is homeostasis?

Answer 38

The process of maintaining the internal environment in a state of dynamic equilibrium within narrow limits around an optimum.

Question 39

Why is it important that core temperature remains stable?

Answer 39

To maintain stable rate of enzyme-controlled reactions.
Temp too low = Enzyme & substrate molecules have insufficient kinetic energy. Low frequency of collisions.
Temp too high = Enzymes denature

Question 40

Why is homeostasis important during exercise?

Answer 40

Maintains body in dynamic equilibrium.

Question 41

How does the autonomic nervous system enable endotherms to thermoregulate?

Answer 41

Via negative feedback:
1. Changes is temp are detected by thermoreceptors in the ski, or thermoreceptors in the **hypothalamus, which detects change in blood temp.
2. Hypothalamus sends impulses to effectors and stimulates effectors to either decrease or increase body temp. May result in vasodilation/vasoconstriction, sweating, piloerection, shivering, an increase in metabolic rate (via impulses to the thyroid gland).

Question 42

Explain the role of the skin in thermoregulation

Answer 42

To increase body temp:
- Hair erector muscles contracts and follicle protrude to trap air for insulation.
- Vasoconstriction - Vessels constrict, reducing blood flow to the skin, reducing heat loss from skin by radiaiton.
- Hormones - adrenaline & thyroxine released (controlled by the hypothalamus) to increase metabolism - more heat is produced.
- Shivering - skeletal muscles contract - more heat is produced from increased respiration.

To decrease hair temp:
- Hair erector muscles relax, hairs lie flat trapping less air. Skin is less insulated & heat can be lost more easily.
- Sweat gland excrete sweat which cools the skin as it evaporates.
- Vasodilation - controlled by hypothalamus. Vessels dilate to increase blood flow to the skin. More heat is lost from the skin by radiaition and the temp decreases.

Question 43

State the homeostatic control mechanism that returns the pH of blood back to its original level.

Answer 43

Negative feedback loop

Question 44

The heart is myogenic. What is meant by the term ‘myogenic’?

Answer 44

The heart will beat without any external stimulus (contraction of the heart is initiated witihin the muscle itself rather than by nerve impulses.)

Question 45

How does electrical activity in the heart results in a heartbeat

Answer 45

1. The sinoatrial node (a group of cells in the wall of the right atrium below the opening to the superior vena cava) generates an an electrical impulse/wave of depolarisation.
2. Depolarisation spreads through/across the atria - causing atrial systole.
3. There is a region of non-conducting tissue which prevents depolarisation spreading straight to the ventricles.
4. The impulse reaches the atrioventricular node (AVN), where there is a breif delay (so the venticles contract after the atria).
5. The AVN passes dopalarisation along the bundle of His (a collection of conducting tissue in the septum.
6. the bundle of His divides into two conducting fibres called purkyne tissue, & carries the wave of excitation along them.
7. Purkyne fibres spread around the ventricles & initiate the depolarisation of ventricles from the apex (bottom) of the heart.
8. This makes ventricles contract from the bottom upwards & blood is forced out into the pulmonary artery and aorta.

Question 46

EXplain how heart rate is controlled

Answer 46

HR is a part of the autonomic nervous sytem and is controlled by the cardiovascular control centre (CCC) in the medulla oblongata. Receptors detect stimuli and send impulses the the CCC, which in response sends impulses along sympathetic or parasympathetic neurones to the SAN to either increase or decrease HR is response to the stimuli.

Question 47

Name the receptors involved in changing heart rate state their location.

Answer 47

Baroreceptors: (detect changes in blood pressure): carotid body.
chemoreceptors: (detect changes in pH e.g. due to increase CO2 concentration): carotid body, aortic body and medulla oblongata.

Question 48

Expplain how heart rate changes in response to changes in blood pressure

Answer 48

• When baroreceptors detect high blood pressure they send impulses to the cardioinhibitory centre in the medulla oblongata, which sends impulses down vagus nerve via the parasympathetic nervous system. parasympathetic neruones secrete acetylcholine. Acetylocholine binds to receptors on SAN causing it to fire impulses less frequently, slowing heart rate and reducing blood pressure.
• When baroreceptors detect low blood pressure they send impulses to the cardioacceratory centre in the medulla oblongata, which sends impulses along the sympathetic neurones. Sympathetic nuerones release secrete noradrenaline, which binds to receptors on SAN, causing the SAN to fire more frequently, increasing heart rate and blood pressure.

Question 49

Explain how Heart rate changes in response to changes in blood pH

Answer 49

During exercise respiration rate increases, which increases CO2 levels & reduces pH and O2 levels of the blood:
- When chemoreceptors detect high O2, low CO2 or high pH, they send impulses to the cardiovascular control centre, which sends impulses along parasympathetic neurones. Parasympathetic neurones secrete acetylcholine, which binds to receptors on the SAN, causes SAN to fire impulses less frequently, decreasing HR so that O2,Co2 and pH return to normal levels.
- When chemoreceptors detect low O2, high CO2, or low pH, they send impulses to the CCC, which sends impulses along the sympathetic neurones to the SAN. sympathetic neurones secrete noradrenaline, which binds to receptors on the SAN, causing the SAN to fire impulses more frequently, increasing HR, and returning O2, CO2, and PH levels back to normal.

Question 50

What is an ECG?

Answer 50

A graph showing the amount of electrical activity in the heart during the cardiac cycle.

Question 51

What does each element of an ECG represent?

Answer 51

P wave: Shows atrial systole (atrial depolarisation) caused by the SAN.
QRS complex: Shows ventricular systole (ventricular depolarisation).
T waves: Ventricular repolarisation

Question 52

Name the heart defects that ECGs can help to diagnose

Answer 52

Symptoms of cardiovascular disease including:
Tachycardia: HR = too fast (above 100bpm)
Bradycardia: HR = too slow (Bellow 60pbm)
Arrhythmia: Irregular heartbeat

Question 53

Why do heart and ventilation rate increase during exercise?

Answer 53

To increase O2 supply for respiring tissues & rapidly remove Co2

Question 54

What is cardiace output and how is it calcualted?

Answer 54

Cardiac output = the totoal volume of blood pumped by a ventricle every minute
Cardiac output (cm^3min^-1) = Heart Rate (bpm) x Stroke Volume (cm^3)

Question 55

Stroke Volume

Answer 55

the volume of blood pumped out of the heart’s left ventricle during each contraction.

Question 56

Using a spirometer to measure the effects of exercise

Answer 56

• Sterilize (disinfect the mouthpiece) and calibrate the equipment.
• Select a healthy volunteer

Question 57

Explain the effects of too much vigorous exercise

Answer 57

• Results in wear and tear of tendons leading to joint damage.
• Suppression of the immune system leading to increased risk of infection.

Question 58

Explain the benefits of moderate exercise

Answer 58

• Helps maintain a healthy weight by increasing metabolic rate and burns excess fat & calories.
• Improves cardiovascular health by strengthening hear muscles, decreasing blood pressure, improves circulation.
• Improves mental health by relieving stress, improving mood and reducing symptoms of depression and anxiety.
• Boosts the immune system - better defence mechanisms against ilnesses and infections.
• enhances strength and endurance - Increased muscle power & improved stamina.

Question 59

Risks of inactivity

Answer 59

Increased risk of cardiovascular disease, obesity, type 2 diabetes
Increased level of LDL’s which are associated with atherosclerosis

Question 60

What is the difference between correlation and causation?

Answer 60

Correlation indicates that there is a relationship between the pattern of two variables.
Causation indicates that the pattern of one variable is a direct consequence of another varaible.

A correlation does not equal a causation

Question 61

Performance-enhancing drugs

Answer 61

PED’s are drugs that can improve a person’s performance in sport and give them an unfair advantage over their oponents. They are banned from most competitive sports and random drug tests are carried out on athletes. If tested positive they are banned and may have medals removed.

• Anabolic steroids: Increase muscle size to give the user increased strength, speed and stamina but may lead to organ damage and increased agression.
• Stimulants: Make the user more alert and able to react faster, they will have greater endurance but it may also lead to aggressive behaviour.
• Narcotic analgesics: Very strong painkillers that enable users to maintain their performance despite suffering from injuries.
• Testosterone: Increases muscle mass
• Blood doping and haemoglobin products: Increase O2 to cells for respiration
• EPO: increase one’s red blood cell mass, which allows the body to transport more oxygen to muscles and therefore increase stamina and performance.
• HGH: help develop muscle mass and bone density
• Insulin increases blood sugar for respiration.

Question 62

Discuss the ethical positions relating to the use of performance enhancing drugs

Answer 62

Rationalists think there may be times when there used is justified. They may argue that:
- Athletes shoulds have the freedom to choose if they want to deal with the risks of taking PEDs.
- May help to overcome inequalities since athletes do not have access to the same opportunities to improve themselves (i.e. training facilities, equipment, coaching).
- Competing at a higher level may only be possible for some athletes if they are using PEDs.

Absolutists think they are morally wrong and should be banned from all sports. They may argue that:
- Many PEDs are illegal.
- There are some serious health risks with PEDs. Side effects include high blood pressure and heart problems.
- Athletes may not be fully informed about the health issues involved.

Question 63

Not all genes are expressed. Why?

Answer 63

Proteins called DNA transcription factors silence or activate genes to enable cell specialisation / to control when proteins are produced.

Question 64

How do trancription factors work

Answer 64

1. Move from the cytoplasm into the nucleus.
2. Bind to promoter or enhancer region of targert gene.
3. Makes it easier or more difficult for RNA polymerase to bind to gene. This increases or decreases rate of transcription.

Question 65

What is the promoter region?

Answer 65

Base sequence upstream/start of a gene.
Facilitates binding of RNA polymerase to promote transcription.

Question 66

What is the enhancer region?

Answer 66

Short base sequence. Binding of transcription factor chromatin structure, making it less condense and enabling RNA polymerase to bind.

Question 67

Give an example of a hormone that affects transcription and how it works.

Answer 67

Thyroxine - hormonal regulation of body temperature
- Normal body temp: Thyroid hormone receptor (a transcription factor) binds to DNA at start of a gene. This decreases the transcription of a gene coding for a protein that increases metabolic rate.
- Cold Body temps: Thyroxine is released and because it is lipid-soluble it can cross the cell membrane and enter the nucleus. In the nucleus it binds to the thyroid hormone receptor causing it to act as an activator, enabling RNA polymerase to bind. The transcription rate increases, producing more protein. The protein increases the metabolic rate causing an increase in body temperature.

Question 68

Explain how hormones which are not lipid soluble can affect transcription factors

Answer 68

Hormones which are not lipid soluble (e.g. protein hormones) cannot cross the cell membrane. Instead they work by:
1. Binding to receptors in the cell membrane, which activates second messenger molecules in the cyroplasm.
2. The second messenger molecules activate enzymes called protein kinases, which triggers a cascade inside the cell.#
3. During the cascade, transcription factors can be activated - these then affect the transcription of genes in the cell nucleus.

Question 69

Hormone doping

Answer 69

• Drugs can act as hormones and control transcription factors to either stimulate or prevent transcription of a gene. This can be used to increase muscle mass or enhance physical activies in sport.

Steroid hormones (e.g. testosterone) are lipid soluble. They can enter through the plasma membrane to ftom a hormone-receptor complex; this initiates the changes in the nuclues.
Peptide hormones (e.g. EPO) cannot enter the cell directly and trigger the release of a second messenger molecule from the cell membrane, which can enter the nucleus to bring about a change.

Question 70

Name two medical technologies that enable those with injuries or disabilities to participate in sport.

Answer 70

• Keyhole surgery to repair damaged joints: uses fibre optics (i.e. endoscopes are a long, thin tube with a light and camera that allows a doctor to see inside the body) so incision can be smaller.
• Prostheses (artificial body parts).

Question 71

What are the advantages of keyhole surgery?

Answer 71

• Smaller incision = shorter recovery time, less risk of infection, less blood loss.
• Fewer staff requires = cheaper
• Less pain after surgery and quicker recovery
• shorter hospital stay

Question 72

What are protheses?

Answer 72

Missing or damaged body parts can be replaced with artificial versions. They can replace entire limbs or parts of limbs (i.e. joints).
Some protheses may be connected to electronic devices that can ‘read’ info from the nervous system (i.e. so prothesis hands can move fingers).
This enables individuals to participate in sports again even after serious injurires