skeletal muscles

Question 1

what microscope is used for a muscle

Answer 1

-light microscope

Question 2

describe the structure of muscle fibres

Answer 2

-they’re cylindrical in shape
-contain many nuclei
-contain many protein strands called microfibilis
-are arranged In parallel to give striped appearance

Question 3

what microscope is used to detect the ultrastructure of a muscle

Answer 3

electron miscrospe

Question 4

what causes the stripe , banding pattern of skeletal muscles

Answer 4

• the arrangement of protein filaments myosin and actin

Question 5

what are myosin and actin ( general(

Answer 5

-protein filaments

Question 6

what is each repeating pattern of banding called

Answer 6

-sarcomere

Question 7

what do the A bands represent in a sarcomere

Answer 7

• the length of myosin
  -the outer region of the A bands are darker as theyre the overlapped actin and myosin

Question 8

what does the H zone represent

Answer 8

H zone is the centre of the A band and is light in colour as only contains myosin

Question 9

What does the M line represent

Answer 9

-where the myosin filaments are joined in the middle

Question 10

what does the I band represent

Answer 10

-represents the actin filaments - thin

Question 11

what does the z line represent

Answer 11

• where actin filaments are joined together

Question 12

what does the sliding filament hypothesis mean

Answer 12

-its the mechanism of muscle contraction
-actin filaments are pulled close to the myosin filaments
-results in the shortening of muscle fibre

Question 13

describe one contraction

Answer 13

-the H zone narrows
-a band remains same size
-I band narrows
- z lines move closer together
-the length of the sarcomere decreases

Question 14

describe the structure of Myosin

Answer 14

-contains thick filaments
- has many many myosin molecules bundled together
-myosin heads extend over the surface
-mysoin heads contain atp which is hydrolysed for muscle contraction
-

Question 15

what does actin do in relation to myosin

Answer 15

• possesses binding sites for myosin heads
  -forms thin filaments

Question 16

what is muscle contraction mechanism general

Answer 16

forming of cross bridges between actin and myosin filaments

Question 17

what is the binding site on actin filaments in RELAXED muscle covered by

Answer 17

PROTEIN called tropomyosin

Question 18

what is muscle contraction activated by

Answer 18

calcium ions

Question 19

where are calcium ions releasd from

Answer 19

the sarcoplasmic reticulum in the muscle fibre when the fibre is stimulated

Question 20

what happens to the calcium ions when theyre released

Answer 20

-bind to tropomyosin causing it to change shape and move from the binding site

Question 21

what does the changing shape of tropomyosin mean

Answer 21

• that actinomyosin bridges can form as myosin heads attach to actin filaments

Question 22

what do calcium ions do in relation to ATP

Answer 22

-they stimulate the action of ATP hydrolase present in the myosin heads , giving myosin the energy to move the actin filaments and detect to myosin heads
-which breaks actinomyson bridges

or
-atp is hydrolysed causing the myosin heads to bend , pulling the actin filaments

Question 23

Describe the roles of calcium ions and ATP in the contraction of a myofibril.

Answer 23

-calcium ions diffuse into myofibrils from reticulum
-calcium ions cause movement of tropomyosin
-whihc causes exposure of binding sites on actin
-myosin heads attach to binding sites on actin
-hydrolysis of ATP on myosin heads cause myosin heads to bend
-bending pulls actin molecules
-attatchment of a new ATP molecule to each myosin head causes myosin heads to detach from actin sites