Run For Your Life Flashcards
Describe how joints work.
Muscle pairs are antagonistic. Muscles causing extension are extensors and flexors reverse the change. Tendons join muscle to bone. Ligaments join bone to bone and are strong and flexible. Cartilage absorbs synovial fluid and shock.
What makes up muscle cells?
- Multinucleate - fibres form from the fusion of individual muscle cells and hence have many nuclei
- Large number of mitochondria - muscle contraction requires ATP hydrolysis
- Sarcoplasmic reticulum - stores calcium ions
- Thin filament (actin) and thick filament (myosin)
- The continuous membrane surrounding the muscle fibre is called the sarcolemma and contains invaginations called T tubules
Activation of muscle contraction
- The neurotransmitter Acetylcholine is released and attached to the ACh receptor in the sarcolemma.
- The action potential is then stimulated in the sarcolemma.
- Action potential travels into the muscle fibre through T- tubules.
- When the action potential reaches the sarcoplasmic reticulum, calcium ion channels open and calcium diffuses into the sarcoplasm.
- The calcium ions then bind to the troponin.
Describe sliding filament theory.
- The calcium attaches to troponin. troponin changes shape and tropomyosin moves away from the binding site.
- myosin head to attach to the binding site on the actin. forms a actin-myosin cross bridge
- ADP and Pi are released from the myosin which causes the myosin head to change shape, pulling the actin filament along.
- ATP attaches to myosin and myosin head detaches TATP is broken down causing the myosin head to move back to its original position, the actin doesn’t move. - This is repeated causing the scaremore to shorten.
How does the myofibril look once contracted
Contracted:
A band → Stays the same length
I- band → Narrower
H-zone → Narrower
Sarcomere → Shortens (z-lines move closer)
Describe glycolysis.
Stages:
- Phosphorylation of glucose, 2 phosphates are added to a glucose molecule. 2 ATP molecules are hydrolyzed to obtain the phosphate needed.
- The splitting of the phosphorylated glucose. This causes 2 triose phosphate molecules to form.
- Oxidation of the split glucose to form pyruvate. 2 hydrogen atoms are removed and are accepted by the NAD which causes them to be reduced. 2 phosphate molecules are then used to produce 4 ATP molecules.
Final products:
2 pyruvate molecules, 2 reduced NAD molecules, net of 2 ATP molecules.
Describe the link reaction.
Stages:
- Decarboxylation and dehydrogenation. Hydrogen is removed and forms reduced NAD and carbon dioxide is produced due to the removal of the carboxyl group. This cause the formation of acetate
- The acetate combines with coenzyme A which forms acetyl COA.
Final Products:
Reduced NAD, CO2 and actively CoA
Describe the Krebs cycle.
Stages:
- Actley group is released from the acetyl CoA
- The 2 carbon acetyl group then combines with the 4 carbon compound to form a 6 carbon compound (citrate)
- The citrate is then decarboxylated and dehydrogenated. So 1 CO2 and 1 Reduced NAD is production. This forms a 5 carbon compound.
- The 5 carbon compound is then decarboxylated and dehydrogenated. This produces 1 CO2 and 1 molecule of reduced NAD. This forms a 4 carbon compound.
- The 4 carbon compound is then temporarily combined with coenzyme A. ATP is also produced (substrate-level phosphorylation)
- The 4 carbon compound is then dehydrogenated twice. This produces reduced FAD and reduced NAD.
Final Products:
3 reduced NAD, 2 CO2, 1 ATP and 1 reduced FAD
Oxidative Phosphorylation
- NADH and FADH are oxidised by releasing hydrogen atoms.
- The hydrogen is split into H+ and electrons.
- The electrons then pass through the electron transport chain through a series of redox reactions.
- This energy pumps the H+ from the matric into the intermembrane space.
- High concentration of H+ in the intermembrane space, creating an electrochemical gradient.
- The H+ move down the electrochemical gradient via the ATP synthase. This phosphorylates ADP and Pi to ATP.
- The electrons and H+ ions recombine to form hydrogen atoms which then combine with oxygen to form water. Oxygen is known as the final electron acceptor.
ATP is synthesised by Chemiosmosis
The hydrogen ions diffuse down the electrochemical gradient through a protein channel.
As the hydrogen ions pass through the channel, ATP synthesis is catalysed by the ATP synthase.
The hydrogen ion causes a conformational change in the enzyme’s active site, enabling the ADP and Pi to bind to the site.
Describe anaerobic respiration.
- Occurs when there isn’t enough oxygen available in a given time period.
- Oxygen cannot act as the final electron acceptor.
- So the proton gradient across the inner mitochondrial membrane cannot be maintained and NADH and FADH are not oxidised.
- So there is no link reaction, Krebs cycle and oxidative phosphorylation.
- Glycolysis occurs and glucose is converted to pyruvate.
- Reduced NAD transfers H to pyruvate to form lactate and NAD
- The NAD can then be reused in glycolysis
- Only 2 ATP made at a time.
Lactic acid reduces PH so it needs to be broken down by:
Converting it back to pyruvate (using oxygen)
Liver cells convert it back to glucose
Describe slow twitch muscle fibres.
- Endurance work - Aerobic respiration
- Large store of myoglobin - a molecule that stores oxygen very efficiently, giving it a more redder colour.
- Rich blood supply
- Higher density of mitochondria to provide a constant and large supply of ATP for contraction
- Contract rapidly and produce powerful contractions but for short period of time
- Large concentration of enzymes involved in anaerobic respiration - allowing them to provide ATP.
- High concentration of glycogen
- Low concentration of myoglobin so a light colour
White, many sarcoplasmic reticulum, high glycogen content. Fatigues quickly.
Myofibril structure
I band (light) → Only actin filaments A band (darker) → Actin and myosin H-zone (lighter) → Only myosin Z-line to Z-line → Sarcomere
