SNAB Topic 7

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  • Created on: 27-08-14 13:08
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Sliding Filament Theory
1. Nerve impulses arrive at a neuromuscular junction.
2. Calcium ions are released from the sarcoplasmic reticulum (i.e endoplasmic
3. Calcium ions diffuse through the sarcoplasm.
4. This initiates the movement of the protein filaments.
5. Calcium attaches to the troponin molecule causing it to move.
6. As a result, the tropomyosin on the actin filament shifts its position exposing the
myosin binding sites on the actin filaments.
7. Myosin heads bind with myosin binding sites on the actin filament forming
8. When the myosin head binds to the actin ADP and Pi on the myosin head are
9. The myosin changes shape causing the myosin head to nod forward.
10. This movement results in the relative movement of the filaments, the attached
myosin moves over the myosin.
11. An ATP molecule binds to the myosin head causing the myosin head to detach.
12. An ATPase on the myosin head hydrolyses the ATP forming ADP and Pi.
13. This hydrolysis causes a change in shape of the myosin head.
14. The myosin head returns to its upright position and the cycle can start again.
The collective bending of many myosin heads combines to make the actin filaments
relative to the myosin filament. This results in muscle contraction.
Fast and slow twitch muscle fibres
Slow twitch muscle fibres Fast twitch muscle fibres

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Energy is released slowly through aerobic respiration Energy id released quickly through anaerobic
aerobic respiration is used to produce ATP slow respiration using glycogen anaerobic respiration
contractions over a long time period.…read more

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The release of CO2 takes place before oxygen is involved.
Respiration turns glucose into CO2 and oxygen into H2O
1. ATP is a nucleotide that consists of 3 main structures ­ the adenine base, ribose
sugar, and a chain of 3 phosphate groups. (Similar to DNA so can be called a
2. Energy is stored in the covalent bonds between the phosphate groups.
3. Energy is required to add the third phosphate bonds to ADP t o create ATP.
4.…read more

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ATPs are used initially and 4 are made, leaving a net gain of 2ATP per
molecule of glucose.
Glucose is at a higher energy level than the pyruvate and so on conversion some energy
becomes available for the direct creation of ATP.
Phosphate from intermediate compounds is transferred to ADP creating ATP which is
called Substrate Level Phosphorylation because the energy for the formation of ATP
comes from the substrates.
Link Reaction
1.…read more

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The remaining 5C compound is also decarboxylated, and then hydrogenated to
form three molecules of NADH and one FADH. This leaves the remaining 4C
compound to combine with another molecule of acetyl CoA. (redox reaction)
5. One of the steps involves Substrate Level Phosphorylation with direct synthesis
of a single ATP. (ADP + Pi ATP)
Electron Transport Chain
1. When a coenzyme accepts the hydrogen with its electron the coenzyme is
reduced (oxidised) becoming reduced FAD or reduced NAD from FADHs and
2.…read more

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Anaerobic Respiration
Glucose (C6H12O6 ) lactic acid (2C3 H6O3 ) + energy (2ATP)
Without oxygen to accept the hydrogen ions and electrons, the electron transport
chain will not function. The reduced NAD created during Glycolysis, the link reaction
and the Krebs cycle is not oxidised. Without a supply of oxidised NAD, most
respiration reactions cannot continue.
However Glycolysis will still continue as long as hydrogen can be removed from
pyruvate and NADH and be converted back to NAD.…read more

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Creatine phosphate breakdown occurs as soon as exercise starts (triggered by the
formation of ADP):
Creatine phosphate creatine + Pi
A.K.A = Creatine phosphate + ADP creatine + ATP
This reaction does not require oxygen ­ Known as the ATP/PC system.
Three energy systems
At the start of exercise, aerobic respiration cannot meet demands for energy
because the supply of oxygen to the muscles is insufficient.…read more

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Training effects
When we train, our bodies adapt. The adaptations are those that make these systems
more efficient. Adequate oxygen supply and higher VO2 max is maintained by:
- Increasing cardiac output
- Larger heart stroke volume
- Faster rate of breathing / deeper breathing increased blood volume and
- Increased muscle stores of glycogen and triglycerides and increased myoglobin
content of muscle
- Increased capilliarisation of lungs and muscles,
- Increased number and size of mitochondria and increased concentrations
of oxidative enzymes.…read more

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Gender male endurance athletes have bigger VO2 max than female endurance
athletes.…read more

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Heart rate
Heart rate varies in different individuals.
Differences in heart Size Those with larger hearts expel more blood with each beat
and so do not need to beat as frequently so circulate the same volume of blood around
the body.
Athletes will have low heart rates as the heart has increased in size due to a thickening
of the muscle walls.
Control of the heart
The heart muscle is myogenic, meaning that it can contract without the need for external
nervous stimulation.…read more


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