| steps for respiration | Glycolysis, link reaction, Krebs's cycle and oxidative phosphorylation |
| define tendon | made connective tissue
they connect skeletal muscles to bones |
| what are muscles? | tissues composed of cells with the ability to contract in order to produce movement
made up of long, slender cells called muscle fibres
there are three types of muscle cell: skeletal, cardiac and smooth |
| structure of muscle cells | myofibrils
actin and myosin filaments
sarcomere
sarcolemma
sarcoplasm
sarcoplasmic reticulum |
| what is the sarcomere? | section of myofibrils between two Z lines |
| what is the sarcolemma? | muscle fibre membrane |
| what is the sarcoplasmic reticulum? | the ER of a muscle fibre
releases Ca2+ ions during contraction |
| sliding filament theory | a nerve impulse is received at the neuromuscular junction
this causes Ca2+ ions to be released from the sarcoplasmic reticulum
the Ca2+ ions diffuse through the sarcoplasm bind to troponin changing its shape and position which displaces tropomyosin exposing the actin binding sites
myosin heads and actin filaments can now form a cross bridge
the hydrolysis of ATP provides energy for the myosin heads to pull on the actin filaments and the sarcomere shortens
ATP then binds to the myosin head to break the cross bridge and cock the myosin head back for another power stroke
this happens along the whole actin filament
when the nerve impulse stops ATP is used to actively transport Ca2+ back into the sarcoplasmic reticulum |
| the role of ATPase in contraction | the enzyme that catalyses the hydrolysis of ATP into ADP and Pi to release energy so the myosin heads can pull the actin filaments and shorten the sarcomere |
| the role of ATP in contraction | it is used to detach the myosin head from the actin filament to break the cross bridge
also provides energy for the active transport of Ca2+ back into the sarcoplasmic reticulum when the nerve impulse stops |
| the role of calcium ions in contraction | attaches to troponin to change its shape to that tropomyosin can expose the actin binding sites |
| define flexors | muscles that bend the limbs/joints |
| define extensors | muscles that straighten the limbs/joints |
| define antagonistic muscle pairs | a pair of muscles that pull in opposite directions
as one muscle contracts the other relaxes |
| what is the skeleton? | gives the body its structure
the skeletal muscles are attached to the skeleton to provide movement |
| define ligament | made of connective tissue
they connect bones together and stabilise the joint in between |
| where does respiration happen? | in the mitochondrial matrix |
| process of glycolysis | first glucose is phosphorylated using ATP to create 2 molecules of triose phosphate-TP (3C) and 2 ADP
TP is then oxidised forming pyruvate (3C)
NAD collects the lost hydrogens to form 2NADH
then 4 ATP molecules are made |
| where does glycolysis occur? | in the cytoplasm |
| process of the link reaction | pyruvate is decarboxylated and oxidised by NAD making NADH and acetate(2C)
acetate combines with co-enzyme A to form acetyl CoA
this reaction happens twice per glucose molecule |
| where does the link reaction take place? | the mitochondrial matrix |
| Krebs's cycle | Acetyl CoA (2C) combines with oxaloacetate(4C) to form citrate (6C)
CoA returns back to the link reaction to be used again and citrate is decarboxylated into a 5C compound
dehydrogenation of citrate also occurs and NADH is made
ATP is also produced
the 5C compound is then converted back into oxaloacetate by decarboxylation
dehydrogenation occurs again to form FADH2 and 2NADH molecules
this reaction also happens twice per glucose molecule |
| where does the Kreb's cycle happen? | in the mitochondrial matrix |
| ETC | electron transport chain
made up of proteins in the membrane that transport electrons via a series of redox reactions |
| oxidative phosphorylation | NADH and FADH2 are oxidised
the released hydrogen atoms split into H+ ions and electrons
the electrons move down the ETC via electron carriers releasing energy along the chain
this released energy is used to actively pump H+ from the matrix into the intermembrane space
an electrochemical gradient is formed because the H+ concentration is higher in the intermembrane space than the matrix
the H+ ions move down the electrochemical gradient back into the matrix via ATP synthase
the movement of the ions provides the energy needed to form ATP from ADP and Pi; this is known as chemiosmosis
at the end of the ETC the H+, electrons and O2 from blood combine to form water and oxygen acts as the final electron acceptor |
| where does oxidative phosphorylation occur? | inner membrane/ intermembrane space |
| what is aerobic respiration? | the splitting of the respiratory substrate glucose to reunite hydrogen with atmospheric oxygen making water and CO2 also releasing a large amount of energy
C6H12O6 + 6O2 ==> 6CO2 + 6H2O |
| what is anaerobic respiration? | respiration without oxygen
pyruvate is converted into lactate
NAD is regenerated
causes muscle fatigue |
| the effect of lactate build up | blood lactate increases
pH falls as H+ is released
the H+ combine with the negatively charged areas on the enzyme
the active site changes shape
the substrate is unable to fit with the enzyme |
| what happens to lactate after a period of aerobic respiration? | most of the lactate is converted back into pyruvate
it is oxidised directly to CO2 and H2O via the Krebs cycle
this releases energy to synthesise ATP increasing oxygen uptake
some lactate may also be converted into glycogen |
| define oxygen debt | excess oxygen needed to oxidise lactate into pyruvate |
| investigate the rate of respiration | two test tubes attached to a respirometer
one should contain a woodlouse with a known mass on a gauze over some soda lime
the other test tube will only have water
mark the starting position of the coloured liquid
close the tap and start the stop watch
take a reading every min for 5 min
carry out repeats to get the mean
calculate the volume of oxygen uptake by doing v = πrh |
| how is lactate removed from the body? | transported to the liver via the blood to be broken down
oxidised into CO2 and water or converted into glucose then glycogen |
