Biology A2 Edexcel, Unit 5 Topic 7, Run For Your Life

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Unit 5
Run for your life
1.1 Structure and function of muscles
1.2 Respiration
1.3 Function of the heart
1.4 Physiological effects of exercise
1.5 Temperature regulation
1.6 Exercise and health
1.7 Performance-enhancing drugs in sport

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Structure and function of muscles
Structure ­ the arrangement of and relations to a complex something
Function ­ an activity or purpose natural to or intended for a person or thing
1.1.1 Muscles
Muscle tissue is made up of highly specialised cells that are able to use energy from the hydrolysis of ATP to make
themselves shorter in a contraction mechanism.…read more

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Heads of the myosin molecules, next to the uncovered binding sites, now bind with the actin filaments which
form `cross-bridges' between them
4. Myosin heads tilt, pushing the actin filaments along
5. ATP binds with the myosin heads and is hydrolysed by ATPase, releasing some energy. The synthesis of this
energy causes the myosin heads to disconnect themselves from the actin filaments
6. The disconnected myosin heads flip back to their original position, and bind with another exposed binding site
on the actin filament.…read more

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Muscles and the skeleton
Striated muscles are attached to the skeleton by strong, inelastic cords known as tendons. Tendons are made of long
fibres of the protein collagen, together with small amounts of another protein known as elastin. When a muscle
contracts, it will pull on the respective tendons which will transmit a force to a bone.
Bones are connected at joints. Joints where the bones can move with respect to each other, e.g. finger joints, elbow
joint, are synovial joints.…read more

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You measure the uptake of oxygen using a respirometer. Organisms can be investigated by placing them into a tube, and
a non-living material of the same mass in the other tube. Soda lime is placed in each tube to absorb the CO2. Cotton wool
prevents contact of the soda lime with the organisms.
Coloured fluid is poured into the reservoir of each manometer and allowed to flow into the capillary tube. It is essential
that there are no air bubbles.…read more

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The Link Reaction
If oxygen is available, the pyruvate now moves into a mitochondrion, where the Link Reaction and the Krebs Cycle
take place. During these processes, the glucose is completely oxidised.
Carbon dioxide is removed from the pyruvate. This CO2 diffuses out of the mitochondrion and out of the cell.
Hydrogen is also removed from the pyruvate, and is picked up by NAD, producing reduced NAD.…read more

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Oxidative Phosphorylation
The hydrogens picked up by the coenzymes are now split into electrons and protons. The electrons are passed along
an electron transport chain (ETC) on the inner membrane in the mitochondrion.
As they move along the chain, the electrons lose energy. This energy is used to actively transport hydrogen ions from
the matrix of the mitochondrion, across the inner membrane and into the space between the inner and outer
membranes. This builds up a high concentration of hydrogen ions in this space.…read more

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The lactate that is produced (usually in muscles) diffuses into the blood and is carried in solution to the blood plasma
to the liver. Here, liver cells convert is back to pyruvate. This requires O2, so extra oxygen is required after exercise
has finished. The extra oxygen is known as oxygen debt. Later, when the exercise has finished and oxygen is available
again, some of the pyruvate in liver cells is oxidised through the link reaction, the krebs cycle and the ETC.…read more

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Physiological effects of exercise
Exercise involves the contraction of muscles. Muscles obtain energy for contraction from ATP, which is produced
through respiration.…read more

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As a person breathes in and out through the mouthpiece, the lid of the air chamber moves up and down, producing a
trace on a chart
By counting the number of traces over known period of time, we can calculate breaths per minute.
Volume of air breathed in with each breath is tidal volume.
Ventilation rate = number of breaths per minute x mean volume of each breath
1.5 Temperature regulation
As energy is transferred, some is lost in the form of heat.…read more



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