Topic 7 part 2

• Use of ATP in glycolysis

  1. ATP hydrolysis

  2. Provides energy

  3. Provides a phosphate group to glucose to prime it for glycolysis
• products of glycolysis:

  Overall, 2 ATP formed, 2 pyruvate and NAD+ reduced to NADH in glycolysis
• Fate of lactate

  1. Lactate leaves the muscle, enters the blood

  2. Enters the liver

  3. Converted back to pyruvate, then pyruvate back to glucose
• Products of krebs cycle:

  Overall, 1 ATP formed, 2 CO2, FAD reduced to FADH2 and NAD+ reduced to NADH in the Krebs cycle/ citric acid cycle
• How the electron transport chain is coupled with proton pumping

  1. NADH is oxidised to NAD+ - H+ ions/protons and electrons are released

  2. Electrons flow through the electron transport chain to reduce oxygen to water

  3. This flow of electrons powers the pumping of H+ ions/protons from the matrix to the intermembrane space across the inner mitochondrial membrane – active transport
• How proton flowing back to the matrix is coupled with ATP synthesis

  1. ATP synthase is both a channel and an enzyme

  2. H+ ions/protons flow back into the matrix through ATP synthase -facilitated diffusion

  3. ATP synthase converts ADP and phosphate to ATP
• Oxidative phosphorylation

  1. NADH is oxidised back to NAD+ - H+ ions/protons and electrons are released

  2. Electrons flow through the electron transport chain to reduce oxygen to water

  3. This flow of electrons powers the pumping of H+ ions/protons from the matrix to the intermembrane space across the inner mitochondrial membrane – active transport

  4. ATP synthase is both a channel and an enzyme

  5. H+ ions/protons flow back into the matrix through ATP synthase -facilitated diffusion

  6. ATP synthase converts ADP and phosphate to ATP
• Mechanisms of thermoregulation during exercise

  1. Thermoreceptors in the hypothalamus detect increase in temperature

  2. Nerve impulses sent down motor neurons to effectors (sweat glands, muscles in blood vessels)

  3. More sweating - loss of heat due to evaporation of water

  4. Vasodilation (of arterioles), vasoconstriction of shunt vessels to increase blood flow towards skin surface/ into capillaries - loss of heat through radiation

  5. Heat production equals heat lost, example of negative feedback to maintain body homeostasis
• Myogenic

  Stimulation generated from within the muscle, this initiates depolarisation by the SAN
• How the heart initiates heartbeat

  1. Sinoatrial node (SAN) initiates depolarisation that travels through the walls of the atria, causing the atria to contract (atrial systole)

  2. Electrical activity is passed to the atrioventricular node (AVN), to the bundle of His and then to the Purkinje fibres, causing the ventricle to contract (ventricular systole)

  3. This initiates heartbeat
• How exercise increases heartrate

  1. Chemoreceptors in the medulla oblongata detect the decrease in pH due to increased respiration

  2. Nerve impulses sent down sympathetic nervous system (noradrenaline neurotransmitter) to the SAN, increasing the frequency of depolarisation, this increases heartrate
• Slow twitch muscle fibres

  • Adapted for aerobic respiration
  • More myoglobin and haemoglobin
  • More red blood cells and capillaries
  • Lots of mitochondria
• Fast twitch muscle fibres

  • Adapted for anaerobic respiration
  • Less myoglobin and haemoglobin
  • Less red blood cells and capillaries
  • Fewer mitochondria
• How calcium ions initiate muscle contraction

  1. Calcium ions are released from the sarcoplasmic reticulum, bind to troponin, troponin changes shape and moves

  2. This displaces tropomyosin, exposing myosin binding sites on actin so actin-myosin crossbridge can form
• How ATP hydrolysis is required for muscle contraction

  1. Myosin head uses energy from ATP hydrolysis to move backwards and pull the actin filaments towards the centre of the sarcomere

  2. ATP hydrolysis also provides energy to break the actin-myosin crossbridge and restart the process

  3. ATP hydrolysis also needed for the active transport of calcium ions back into the sarcoplasmic reticulum