muscle contraction

Question 1

what is a myofibril

Answer 1

contractile unit of skeletal muscle

Question 2

what are the two protein filaments present in the myofibril

Answer 2

actin myosin

Question 3

what are the three proteins making up actin

Answer 3

troponin tropomyosin
actin

Question 4

what does the z line do in a myofibril

Answer 4

holds together the actin/ thin filament

Question 5

what are the different ways of saying actin in the myofibril

Answer 5

thin filament
light band
actin

Question 6

what is the dark band made of

Answer 6

myosin

Question 7

what is the h zone

Answer 7

when there is thick and thin filaments overlapping, but there is a dark region where there is no overlap, only dark band,

Question 8

what is the distance between two z lines called

Answer 8

sarcomere

Question 9

what is the function of tropomyosin

Answer 9

covers and exposes myosin head binding sites on the actin molecule.

Question 10

what does troponin do

Answer 10

changes shape when calcium is present

Question 11

what is the sliding filament hypothesis

Answer 11

during contraction, thick and thin filaments slide past eachother.

Question 12

describe the contraction cycle and role of atp in 4 steps

Answer 12

1- myosin head attaches to the actin filament forming a cross bridge
2- myosin head moves causing a power stroke (thin filament slide over thick filament). During a power stroke adp and pi are released from the myosin head.
3- after power stroke, new atp molecule attaches to myosin head and is hydrolysed allowing breakage of the cross bridge and reorientation of the myosin head.
4- myosin head can now make a new cross bridge further down the actin filament.

Question 13

what is a cross bridge

Answer 13

link between myosin head and actins binding site

Question 14

what are the three ways muscles maintain supply of atp

Answer 14

aerobic respiration-
anaerobic respiration
creatine phosphate

Question 15

how does creatine phosphate (cp) create atp

Answer 15

acts as a reserve store of phosphate groups. phosphate can be taken from cp to ADP to create adp rapidly.

Question 16

what two things occur during a power stroke

Answer 16

released adp and pi
causes thin and thick filaments to slide over eachother.

Question 17

how does aerobic respiration miantain atp supply

Answer 17

oxidative phosphorylation etc..

bohr effect allows more oxygen release from hb when intense activity, limited by oxygen delivery rate.

Question 18

why is anaerobic respiration not an effect source of atp for muscles

Answer 18

because they do give atp however, they release lactic acid which is toxic and caused fatigue.

Question 19

what causes the sliding action

Answer 19

movement of myosin heads when attached to actin

Question 20

what does tropomyosin do when muscle is stimulated

Answer 20

it moves and exposes the actin binding sites.

Question 21

what happens to actin when action potential has entered sarcoplasmic reticulum

Answer 21

action potential reaches sarcoplasmic reticulum which stores calcium and causes it to be released into the sarcoplasm

calcium binds to troponin, altering its shape and causing tropomyosin to move and expose actin binding sites.