Topic 7

• Deduce how athletes with transtibial amputations are able to move their prosthetic limbs during a race.

  - muscle still attached to lower leg, prosthetic limb attached to lower leg
• Explain the effect of increasing calcium ion concentration on the mean force produced by muscle fibres.

  - no force below 1, threshold for Ca+ conc- Ca+ increases, force increases- more actin and myosin interact / myosin binding sites exposed - no increase in force @ high conc.- all myosin binding sites occupied
• Describe the role of calcium ions in the contraction of muscle fibres.


  - bind to troponin- alter shape of tropomyosin- expose myosin binding site on actin
• Explain how the structure of a muscle fibre is related to its specialised function

  - sarcolemma contains voltage-gated channels to allow depolarisation, sarcoplasmic reticulum stores/releases calcium ions•- many mitochondria for aerobic respiration / to supply ATP - presence of myofibrils / actin and myosin - myofibrils allow contraction (of muscle
• A student stated that loss of heat when sweating is related to the dipole nature of water.Justify this statement.

  - water has an uneven distribution of charge (making it a dipole) - water forms hydrogen bonds with other water molecules - it requires a lot of heat energy to break these bonds - and allow water to evaporate taking the heat energy with it
• Explain the role of the nervous system in bringing about the increase in temp of the fingertips

  - thermoreceptors detect increase in temperature - thermoregulatory centre coordinates heat loss mechanism- more impulses are sent along the sympathetic nerves- constriction of shunt vessels - vasodilation of arterioles - more warm blood flows near the skin surface
• A woman was wrapped in blankets and her feet were put in hot water for 30 mins. The temp. of the skin at her fingertips were recorded. Explain why there where no changes from 0-3mins.

  - Takes time for heat to warm blood- Bc. of layer of insulation in skin- Takes time for warm blood to circulate
• Spirometer definitions + calculations

  - Respiratory minute ventilation:Tidal volume x ventilation rate Tidal volume= diff. in peak to trough volume Ventilation rate= no. of peaks in 1 min - Oxygen consumption per minute Diff. in volume of 1 peak compared to prev. peakDivide by time between two peaks x60
• Why is ATP required for the conversion of F-6-P into F-2-6-BP

  - hydrolysis of ATP- provides energy for the reaction- provides the phosphate group for phosphorylation
• Explain how starting to exercise causes an increase in breathing rate

  - exercise initiates impulses from motor cortex/stretch receptors- impulses sent from ventilation centre in medulla- increased impulses to intercostal muscles/diaphragm
• Explain the effect of exercise on the changes in oxygen consumption

  - increases O2 consumption - increased aerobic respiration - more ATP needed by muscles- oxygen needed to convert lactate to pyruvate- oxygen consumption begins to decrease after exercis
• Explain the role of the carrier molecules in the ETC

  - receive hydrogen from reduced NAD / FAD- allow reduced NAD / FAD to be oxidised - break hydrogen into protons and electron- electrons transferred by a series of redox reactions- energy released is used to pump H+ into intermembrane space
• Explain why some ATP is broken down during glycolysis

  - donates phosphate to glucose- supplies energy to break down glucose, makes glucose more active - produce phosphorylated 3C compounds (GP, GALP)
• MCQs: - during which processes is ATP formed?- what is transferred to FAD to form reduced FAD- what are the products of glycolysis- where does chemiosmosis occur in the mitochondria- where is reduced NAD produced- The number of ATP molecules synthesised in mitochondria from one molecule of acetyl CoA is-


  - glycolysis, Krebs, ETC- 2 hydrogen atoms- pyruvate + ATP- cristae- cytoplasm- 12
• Cells produce lactate during anaerobic respirationLiver cells can absorb lactate from the bloodDeduce what happens to the lactate in these cells

  - oxidised to pyruvate- converted to glucose/glycogen- used in respiration (glycolysis: glucose, link reaction: pyruvate)
• Compare and contrast the structures of actin and collagen

  - actin: has tertiary structure- collagen: has 3 polypeptide chains, actin: only 1- both= seq. of amino acids joined by peptide bonds- both= have secondary structures
• Describe how the brain reduces the activity of the sweat glands after exercise

  - thermoreceptors detect temp change- thermoregulatory centre sends fewer impulses to sweat glands
• Explain the role of the brain in reducing the student's heart rate after exercise

  - chemoreceptors detect change in pH- cardiovascular control centre sends impulses to heart - impulses transmitted along parasympathetic nerve to SAN to reduce heart rate
• Explain how the respiratory centre is involved in the control of ventilation rate in the 10 minutes of rest after exercise

  - High CO2 in the blood stimulates the respiratory centre- Increase in lactate / fall in pH stimulates the respiratory centre - chemoreceptors in the aortic bodies stimulated - More impulses sent to diaphragm and intercostal muscles - increase in the rate and depth of breathing - pH returns to normal as CO2 is removed and ventilation rate decreases
• Explain the change in the oxygen consumption during the 10 minutes of rest after exercise

  - anaerobic respiration occurs during exercise because oxygen supply to cells is limited - therefore glycolysis used to produce ATP - glycolysis also produces lactate - oxygen consumption is higher at end of exercise than at rest because lactate is converted back to pyruvate- pyruvate enters Krebs cycle - oxygen used in electron transport chain as final hydrogen electron acceptor to form water
• Explain why muscles come in pairs

  - muscles can only work in one direction - need to create opposite forces - must have extensors and flexors
• Person A has more fast twitch fibres, person B has more slow twitch fibres.Explain which person has muscles that are more resistant to fatigue.


  - slow twitch are more efficient at aerobic respiration because they have more mitochondria - slow twitch have many capillaries to give good oxygen supply- slow twitch have lots of myoglobin to store oxygen - therefore less likely to build up lactate
• The electron micrograph shows the myofibrils in a relaxed muscle. Exp lain how the appearance of this myofibril changes when a muscle contracts

  - actin + myosin remain same length, slide past each other- z lines closer, sarcomere shorter
• The last carrier in the electron transport chain is the enzyme cytochrome oxidase . Cyanide attaches permanently to the active site of this enzyme. Explain why cyanide is a lethal metabolic poison

  - cyanide inhibits cytochrome oxidase so it can no longer accept electrons - electrons stop moving along the electron transport chain - no movement of hydrogen ions into intermembrane space • - no movement of protons down gradient / no chemiosmosis - NADH/FADH can no longer give up electrons and regenerate NAD/FAD so Krebs cycle stops - no production of ATP from Krebs cycle or electron transport chain- cellular processes have no energy source e.g. heart muscle being prevented
• explain why heart rate increases in volcanic env.

  - conc. of CO2 in lungs higher- concentration of CO2 in blood is higher - pH of blood falls due to increased CO2- pH levels in blood detected by chemoreceptors- in carotid body - respiratory} centre- control in medulla - sends more impulses along neurones - to intercostals muscles / diaphragm
• Explain how a spirometer trace can be used to calculate the mean resting breathing rate of a person


  - one breath is peak to peak or trough to trough- count the number of peaks or troughs in a set time- number per minute - repetition to obtain a mean or improve reliability
• what is an ecg

  - shows heart rate- waves of electrical activity in the heart-. over a period of time during cardiac cycle
• Describe and explain the role of calcium ions and ATP in muscle contraction.

  - vesicles / t-tubules / sarcoplasmic reticulum contain calcium ions - binds to troponin - tropomyosin moves exposing binding sites for myosin - needs ATP to remove calcium ions- ATP provides energy for changing shape of myosin - ATP is required to break cross bridges - ATP for synthesis of neurotransmitter
• Comment on how gender could affect thermoregulation in marathon runners

  - increase in body temperature causes greater increase in rate of sweating in males - males lose heat faster because they produce sweat at a faster rate - females have larger SA to body mass ratio that allows for faster heat loss - males have less insulation which may allow faster heat loss
• Describe how thermoregulatory mechanisms are controlled to help marathon runners avoid heat stress

  - thermoreceptors in skin detect increase in temperature - thermoregulatory centre in hypothalamus stimulated- hypothalamus sends impulses to sweat glands- increased blood flow to surface of skin by vasodilation / constriction of shunt vessels- decreased metabolic rate
• Explain how the extensor and flexor muscles bring about movement of the lower leg

  - tendons attach muscles to bones - (flexor and extensor) muscles act as an antagonistic pair - extensor muscle contracts, it pulls on the tibia to extend the leg / flexor muscle contracts, it pulls on the fibula flexing the leg
• The seeds in the experiment with nitrogen gas continued to germinate. Suggest an explanation for the lack of movement of the liquid.

  - no oxygen available/no oxygen uptake - anaerobic respiration - carbon dioxide produced is absorbed - no (net) change of {volume / pressure} of gas
• Describe how the concentration of calcium ions around the myofibrils is controlled

  - Ca+ released from sarcoplasmic reticulum - in response to action potential- calcium channels open to allow calcium ions to cross the membrane - calcium ions taken back up into the sarcoplasmic reticulum by active transport
• Explain how the changes caused when calcium binds to actin allows muscles to contract

  - myosin heads can bind to binding sites - myosin changes shape- actin filaments slide over the myosin - muscle fibres / myofibril / sarcomeres shorten - ATP hydrolysed = ADP + Pi released
• Describe the changes caused when calcium ions binds to actin

  - tropomyosin is moved by troponin (shape altered)- myosin binding sites on actin are exposed- actin-myosin cross bridges formed
• Describe how the sinoatrial node (SAN) is involved in bringing about a change in heart rate as the level of activity increases

  - more stimulation / depolarisation of the SAN (from the sympathetic nervous system) - more impulses to the SAN - more frequent waves of depolarisation from the SAN (to the atria) - more frequent contraction of atria / stimulation of AVN
• EQ insect flight uses a lot of energy. insects use trehalose which is a disaccharide and glycogen Explain the advantages of this


  -glucose used in respiration to provide energy-glycogen is a polymer of glucose-glycogen has lots of branches so it can release glucose rapidly-breakdown of trehalose makes two molecules of glucose available
• EQ** the last carrier in the electron transport chain is the enzyme cytochrome oxidase. Cyanide attaches permanently to the active site of this enzymeexplain why cyanide is a lethal metabolic poison


  -cyanide inhibits cytochrome oxidase so it can no longer accept electrons. -this means electrons stop moving along the electron transport chain-so no movement of hydrogen ions into intermembrane space and so no movement of protons down gradient-this means NADH can no longer give up electrons and regenerate NAD so the Kreb cycle stops-so no production of ATP from Krebs cycle or electron transport chain and so cellular processes have no energy source-meaning muscle contraction prevented eg heart muscle
• state one difference between the structure of pyruvate and the structure of the acetyl group in acetyl CoA

  pyruvate has 3 carbons compared to 2 carbons in acetyl
• EQ describe the fate of reduced NAD in aerobic respiration

  -reduced NAD from glycolysis enters mitochondria-moves to inner membrane of mitochondrion-becomes oxidised to NAD+-as electrons transferred to electron transport chain-hydrogen ions are pumped into membrane space-NAD returns to Krebs cycle