Topic 7a - muscles and respiration Flashcards
What is a tendon?
Non-elastic tissue which connects muscle to bone
What is a ligament?
Elastic tissue that joins bones together and determines the amount of movement possible at a joint
What is a joint?
Area where 2 bones are attached for the purpose of permitting body parts to move
What are skeletal muscles?
Muscles that are attached to bones, arranged in antagonistic pairs
What are antagonistic pairs?
Pairs of muscles which pull in opposite directions - one contracts and the other relaxes.
Extensors - act to straighten the joint
Flexors - bend the joint
Give an example of antagonistic pairs
Tricep relaxes and bicep contracts to lift the arm
What is skeletal muscle made of?
Muscle fibres
What is the cell membrane of a muscle fibre cell?
Sarcolemma
What do the folds in the sarcolemma do?
Help spread electrical impulses throughout the sarcoplasm so they reach all parts all of the muscle fibre
What is the function of the sarcoplasmic reliculum?
stores + releases Ca+ which are needed for muscle contraction
Why do muscle fibres have lots of mitochondria?
To provide ATP that is needed for muscle contraction
What filaments do myofibrils contain?
Thick myosin filaments and thin actin filaments
How do thick and thin myofilaments cause muscles to contract?
They move past (slide over) each other
What are thick myofilaments made of?
The protein myosin
What are thin myofilaments made of
The protein actin
When viewing a myofibril under a microscope you will see dark bands, what do they contain?
Thick myosin filaments And some overlapping thin actin filaments
What is the A band made of?
A dark band containing thick myosin filaments and some overlapping thin actin filaments
What do light bands contain and what band do the light bands make?
I bands, thin actin filaments ONLY
What is myofibril made up of?
May short units called sarcomeres
What marks the end of each sarcomere?
Z-line
What line is in the middle of each sarcomere?
M-line
What does the H zone contain?
ONLY myosin filaments
How can muscle contraction be explained?
Sliding filament theory
What does the sliding filament theory state?
Myosin and actin filaments slide over one another to make the sacromeres contract
What causes myofibrils and muscle fibres to contract?
Simultaneous contraction of sarcomeres
Do sarcomeres return to their original length as the muscles relax?
Yes
When walking, your quadriceps (muscles at the front of the thigh) contract to straighten the leg, whilst your hamstrings (muscles at the back of the thigh) relax. Then your hamstrings contract to bend the leg, whilst the quadriceps relax.
a) State which of these muscles are the extensors and which are the flexors.
b) State the name given to muscles that work together to move a bone.
A) quadriceps = extensors, hamstrings = flexors
B) antagonistic pairs
Myosin filaments have g……. H…. And b…… s….
Globular heads and binding sites
Why are the globular heads on myosin filaments hinged?
So the globular heads can move back and fourth
Which myofilament has the actin-myosin binding sites?
Actin
Where are tropomyosin and tropin found between?
Actin filaments
Why are tropomyosin and troponin proteins attached to each other?
To help myofilaments move past each other
When resting muscles are blocked from contracting by t….
Tropomyosin
How in tropomyosin held in place?
Troponin
Why can’t myofilaments slide past eachother in a resting state?
Because the myosin heads can’t bind to the actin myosin binding site on the actin filament due to the tropomyosin blocking the binding site
Muscle contraction is triggered by a….. p…….
Action potential
What happens when action potential from motor neuron stimulates a muscle cell?
It depolarises the sarcomella (the difference in charge is reduced) and this depolarisation spreads down t-tubules to the sarcoplasmic reticulum.
What does the depolarisation of the sarcoplasmic reticulum cause?
It to release the stored calcium ions into the sarcoplasm
Where do calcium ions bind to?
Troponin
What happens when calcium ions bind to troponin?
It causes troponin to change shape which pulls the attached tropomyosin out of the actin- myosin binding site on the actin filament. Which exposes thE binding sites the myosin head to bind.
What is the name of the bond formed when a myosin head binds to an actin filament?
Actin-myosin cross bridge
What provides energy to move the myosin head?
ATP
What enzyme do calcium ions activate?
ATPase
What does ATPase do?
Break down ATP into ADP+pi to provide energy needed for muscle contraction
Energy released from … moves the …… …. Which ….. the ….. …….. along in a rowing action
ATP, myosin head, pulls, actin filament
What causes the actin-myosin cross bridge to break?
ATP
What happens when the actin-myosin cross bridge breaks but calcium ions are still present?
The myosin head reattaches to a different binding site which is further along the actin filament and a new cross bridge is formed + cycle is repeated
What does the formation and breaking of cross bridges rapidly cause?
The sarcomere to shorten which causes the muscle to contract
What needs to be present for muscle contraction to continue?
Calcium ions which are bound to troponin
What happens when the muscle cell stops being stimulated by motor neurones?
Calcium ions leave their binding sites on the troponin molecules + are moved by active transport back into the sarcoplasmic rectilium
What happens to troponin and tropomyosin when calcium ions leave the binding site?
Troponin molecules return to their original shape, pulling attached tropomyosin molecules with them, this means tropomyosin block the actin- myosin binding sites again
Why dont muscles contract when calcium ions arnet present?
Because the myosin heads arnet attached to actin filaments
How do actin filaments return to their relaxed position?
Actin filaments slide back to their relaxed position which lengthens sarcomere
What are some properties of slow twitch muscle fibres?
Contract slowly, muscles we use for posture, good for endurance activities, can work for a long time without getting tired, energy released slowly through aerobic respiration, reddish colour
Properties of fast twitch muscle fibres…
Contract quickly, muscles for fast movement, good for short bursts of energy, energy released through anaerobic respiration using glycogen, whitish colour
Rigor mortis is the stiffening of muscles in the body after death. It happens when ATP reserves are exhausted. Explain why a lack of ATP leads to muscles being unable to relax.
- lack of ATP leads to muscles being unable to relax because ATP is needed to break actin- myosin cross bridge
- if cross bridges cant be removed, myosin head remains attached to actin filaments so actin filaments can’t slide back to relaxed position
Write the equation for respiration
C6H12O6 + 6O2 -> 6CO2 + 6H2O + ENERGY
What are the four stages of respiration
1) glycolysis
2) link reaction
3) kerbs cycle
4) oxidative phosphorylation
What is the main purpose of glycolysis?
To make 2 x pyruvate from glucose
Where does glycolysis happen?
Cytoplasm
What are the 2 stages of glycolysis and briefly explain them?
Stage 1 = phosphorylation
- glucose is phosphorylated by adding 2 phosphates from 2 molecules of ATP
- creates 2 molecules of triose phosphate + 2 molecules of ADP
Stage 2 - oxidation
- triose phosphate is oxidised (loses H), forming 2 pyruvate
- NAD collectes hydrogen ions forming 2 NADH
- 4 ATP are produced but 2 are used in stage 1 so net profit of ATP = 2
Draw glycolysis
OneNote
What is the main purpose of the link reaction?
Converts pyruvate to acetyl coenzyme A
Where does the link reaction take place?
Mitochondrial matrix
Explain the link reaction
1) pyruvate is decarboxylated which results in co2 being released
2) NAD is reduced - collects hydrogen from pyruvate which changes pyruvate to acetate
3) acetate combines with coenzyme A (CoA) to form acetyl coenzyme a (Acetyl CoA)
4) No ATP is produced
Draw stage 2 of respiration
Link reaction: one note
How many times does the link reaction happen for every glucose molecule?
Twice
What is the main purpose of the Krebs cycle?
To produce reduced coenzymes and ATP
Where does the Krebs cycle take place?
Mitochondrial matrix
Explain the process of the Krebs cycle..
1) acetyl CoA from the link reaction combines with oxaloacetate (4c) to form citrate (6)
2) citrate molecule is converted to a 5c molecule, decarboxylation occurs where co2 is removed, dehydrogenation occurs and H is removed. H is used to produce NADH
3) 5C molecule is converted into a 4c molecule. Decarboxylation and dehydrogenation occur, producing 1 molecule reduced FAD and 2 NADH
- ATP is produced
- citrate has been converted to oxaloacetate (4c)
What is the main purpose of the fourth stage of respiration?
Produce lots of ATP
What are the two processes involved in oxidative phosphorylation?
Electron transport chain and chemiosis
Explain the process of oxidative phosphorylation
1) hydrogen atoms ate realised from reduced NAD and FAD as they are oxidised to NAD and FAD. H atoms split into protons and electrons
2) electrons move down electron transport chain and lose energy after each carry
3) energy is used by electron carriers to pump protons from the mitochondrial matrix into the intermembrane space
4) concentration of protons is now higher in the intermembrane space than in mitochondrial matrix - this forms electrochemical gradient
5) protons move down electrochemical gradinent back into the mitochondrial matrix via ATP synthase. This movement drives synthesis of ATP
6) movement of H+ ions across a membrane which generates ATP = chemiosis
7) in mitochondrial matrix, at the end of the transport chain, protons, electrons and o2 combine to form H20
8) Oxygen is the final electron pair acceptor
Draw the final step of aerobic respiration
Oxidative phosphorylation: one note
How much ATP can one molecule of glucose produce
38 ( links and krebs happen twice)
How do you measure the rate of respiration?
Respirometer
How does a respirometer work?
The volume of O2 taken up / the volume of co2 measured in a given time is measured
What equipment do you need in a respirometer and draw it ?
- calibrated scale
- manometer contains coloured fluid syringe
- woodlice/ maggots
- gauze
- soda lime/ potassium hydroxide
- glass beads
- test and control tube
Name a type of anaerobic respiration…
Lactate fermentation
What is the equation for lactate fermentation?
Glucose -> pyruvate -> lactate
(On second arrow NADH is turned to NAD)
How is glucose converted to pyruvate?
Glycolysis
What are the two ways in which lactic acid can be broken down?
- cells can convert lactic acid back to pyruvate
- liver cells can convert lactic acid back to glucose where is can then be respired or stored
Why can anaerobic respiration continue when no oxygen is present?
Because the production of lactate regenerated NAD, so glycolysis can continue
