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Topic 7: Run for your life:
7.1 Cellular respiration

Respiration = The chemical process of releasing energy from organic compounds (respiratory
substrates) such as glucose through oxidation. The energy released is used to combine ADP
with inorganic phosphate to make ATP (energy). Respiration is a long series of
enzyme-controlled reactions.…

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If oxygen is available, the pyruvate moves to the mitochondrial matrix, where the link
reaction and Krebs cycle occurs. The link reaction converts pyruvate into acetyl CoA. The link
reaction does not produce any ATP.

1) Carbon dioxide is removed from pyruvate (decarboxylation) and diffuses out of
the mitochondria and…

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protons (hydrogen ions). The electrons are passed along the electron transport chain, on the
inner membrane of the mitochondria.

As they move along the chain in a series of redox reactions, they lose energy which is used
to transport hydrogen ions from the mitochondrial matrix across the inner membrane and…

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Anaerobic respiration
If oxygen is not available, the link reaction and Krebs cycle stop and oxidative
phosphorylation cannot occur as there is no final electron acceptor. Glycolysis can still
continue as long as the pyruvate can be removed and the reduced NAD can be converted
back to NAD. This does…

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The rate of oxygen uptake is measured using a respirometer. Organisms (woodlice) are
placed into a tube and the same mass of a non-living material is placed in the other. Soda
lime (or potassium hydroxide/KOH solution) in each tube absorbs the carbon dioxide.
Cotton wool prevents contact of the soda…

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Link reaction: Turns pyruvate into acetyl coA for the Krebs cycle by releasing carbon
dioxide and 2 hydrogens.
Decarboxylation: Carbon dioxide is released as a waste product
Dehydrogenation: Hydrogens removed and taken up by coenzymes
Acetyl coA: First step in Krebs cycle, last step in the link reaction
Krebs cycle:…

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Muscle fibres are made of myofibrils, which are made of many short units called sarcomeres.
The ends of sarcomeres have a Z line and the middle has an M line (attachment for myosin).
They contain bundles of protein filaments (myofilaments) called actin and myosin which
move past each other to…

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Low levels of creatine phosphate High levels of creatine phosphate
Less sarcoplasmic reticulum More sarcoplasmic reticulum
Relatively narrow so oxygen can diffuse Relatively wide

The sliding filament theory
Muscle contraction works as actin and myosin filaments slide between each other, causing
the sarcomeres to become shorter, shortening the whole…

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bend at the elbow is the biceps, known as the flexor muscle. The triceps are the extensor
muscle, causing the arm to straighten when it contracts. As the arm bends, the biceps
contract and the triceps relaxes, although it may contract slightly to control the movement.
Muscles can only pull…

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Sarcoplasm: Cytoplasm of a muscle cell

7.3 The heart, energy and exercise

Controlling the heart
The heart is myogenic ­ it contracts and relaxes automatically without stimulation from
nerves to pump blood around the body. It is specific and made of specialised tissue called
cardiac muscle. Rhythmic contraction of the…


Tilly - Team GR


So detailed and helpful. Thanks :)

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