Muscles And Synapses L7

Question 1

Multiple myofilaments

Answer 1

• several myosin and actin filaments are interacting = sliding filament theory of muscle contraction
• even tho the sacromere shortens, the length of each myofilament does not change. However the width of the H zone changes

Question 2

The 5 different molecules involved in slipping filament theory

Answer 2

1) myosin
2) actin
3) trpomyosin
4) troponin
5) ATP
6) calcium ions

Question 3

In skeletal muscle cells, myosin are bundles together to form the

Answer 3

Thick filament

Question 4

The cross bridge (head) of the myosin module has the ability to

Answer 4

Move back and forth, this movement provides power stroke for muscle contraction

Question 5

The cross bridge has two binding sites, one site binds to

Answer 5

ATP (low E conformation), hydrolysis = (high E conformation) and the other binds to actin.

Question 6

______ is a major component in the thin filament

Answer 6

Actin, each actin subunit has binding site to which myosin crowd bridge binds to

Question 7

The actin portion of the thin filament is composed of actin subunits twisted into a

Answer 7

Double helical chain

Question 8

Tropomyosin is part of the thin filament ?

Answer 8

YES

Question 9

Tropomyosin wraps around actin, in unstimulated muscle, the tropomyosin wraps around

Answer 9

binding sites of actin, preventing myosin cross bridge form binding

Question 10

In order to move tropomyosin and myosin aside to expose the binding sites,

Answer 10

Troponin attaches and and is spaced periodically along tropomyosin strand

Question 11

After an AP, calcium ions are released from the terminal cisternae and bind to troponin. This causes conformational change in the

Answer 11

tropomylosin-troponin complex, dragging the tropomyosin strands off the bidning site

Question 12

6 steps of cross bridge cycling

Answer 12

1) the influx of calcium, triggers the exposure of binding steps on actin
2) binding of myosin to actin
3) the power stroke of the cross bridge that causes the sliding of the thin filaments
4) the binding of ATP to the cross bridge, which results in the cross bridge disconnecting from actin.
5) hydrolysis of ATP = re-energizing the repositioning of the cross bridge
6) the transport of calcium ions back into the sacroplamic reticulum

Question 13

STEP 1: exposure of binding sites on actin

Answer 13

• AP binds calcium ion form terminal cisternae of thesacroplasmic recticulum
• Ca flood into cytosol and bind to the troponin, causing a change in conformation of the troponin-tropomyosin complex = exposing the binding sites

Question 14

STEP 2: binding of myosin of actin

Answer 14

When a binding site on actin is exposed, an energized cross bridge binds to it

Question 15

STEP 3: power stroke of the cross bridge

Answer 15

• the binding of myosin to actin about a change in the conformation of the cross bridge, resulting in the release of ADP inorganic phosphate
• cross birdge flexes, pulling the thin filament inward toward Center pol the sacromere = power stroke
• the chemical E of ATP is transformed onto mechanical E of a contraction

Question 16

STEP 4: disconnecting the cross bridge actin

Answer 16

In order to disconnect the cross bridge form actin, ATP must bind on the myosin cross bridge

Question 17

STEP 5: re-energizing and repositioning the cross bridge

Answer 17

• the release of the myosin cross bridge form actin triggers the hydrolysis of the ATP
• E transferred form ATP top my sos in bridge, which returns to its high E conformation

Question 18

STEP 6: removal of calcium ions

Answer 18

• calcium is actively transported form the cytosol into the sacroplamsic recticulum by ion pumps
• Ca removed, troponin-tropomyosin complex again covers the binding site.

Question 19

During contraction, all cross bridges are

Answer 19

Neither bound nor disconnected at the same time

Question 20

Ca pumps

Answer 20

Active transport moves Ca in sacroplasmic recticulum

• ATP hydrolysis

Question 21

Role of ATP

Answer 21

1) energizing power stroke of the myosin cross bridge
2) disconnecting myosin courses bridge from BS on actin act the conclusion of the power stoke
3) pumping Ca back into the sacroplasmic recticulum

Question 22

Types of muscle fibre

Answer 22

• white muscle fibre

- red muscle fibre

Question 23

Features of white muscle fibre

Answer 23

• large
• light colour cuz of reduced myoglobin
• surrounded by few capillaries
• few mitochondria
• high glycan (glycolysis)

(Small O2 amount available, powered by glyoclysis cuz doesn’t use O2)

Question 24

Features of red muscle fibres

Answer 24

• small
• dark colour = lots of myoglobin
• many capillaries
• lots of mitochondria
• low glycan

(Use KREBS and oxidative phosphorylation, which require mithcodornia and O2)

Question 25

Metabolism in white muscle fibres

Answer 25

• muscle w many WMF are better for activities requiring speed and power for short duration.
• glycolysis = synthesizes ATP quickly
• cross bridge cycling occurs in fast contractions (fast twitch glycolytic fibres )
• fatigue rapidly due to lactic acid build up
  And depletion of glycogen

Question 26

Metabolism of red muscle fibres

Answer 26

• muscle w many RMF are better for activates needing endurance
• Krebs and oxidative phosphorylation = ATP
• cross bridge cycling occurs slowly (slow-twitch oxidative fibres)
• fatigue resistant, high endurance