Lecture 3 Skeletal Muscle 2

Question 1

Describe the events of the cross bridge cycle at the attachment phase

Answer 1

.The initial attachment of myosin head to thin filament forms a weak bond at binding site. It then breaks anoter weak bond holding Pi inside the nucleotide binding site releasing the Pi into cytosol. The Pi release allows a myosin head to create more noncovalent bonds with actin binding site thus creating a strong bond.

Question 2

Describe the events of the cross bridge cycle at the power stroke phase

Answer 2

.The release of the Pi causes the myosin head to conformationally change. This makes the Myosin head move from pre-power stroke to rigor position through the rotation of the S1 part of the myosin. This rotation is called the power stroke. At the end of the power stroke ADP is released from the nucleotide binding site on the myosin head.

Question 3

Describe the events of the cross bridge cycle at the detachment phase

Answer 3

.Myosin will stay bound to actin in rigor state until a fresh molecule of ATP arrives. When ATP arrives the myosin head breaks from the attachment of actin

Question 4

Describe the events of the cross bridge cycle at the return to the pre-power stroke conformation phase

Answer 4

.The return phase has the ATP in the myosin head become hydrolyzed by the myosin head to produce ADP + Pi. This makes the S1 rotate back to pre-power stroke conformation.

Question 5

Besides what the name is, what is ATP?

Answer 5

It is a molecule containing high-energy bonds used to transfer energy between systems within a cell

Question 6

What are the four steps in Cross-Bridge Cycle Theory aka Sliding Filament

Answer 6

Attachment, Power Stroke, Detachment, Return

Question 7

How much ATP is stored in muscles to be used at any given time?

Answer 7

A small amount, roughly 10 seconds worth

Question 8

How is ATP produced?

Answer 8

Phosphocreatine catabolism (CK)
Anaerobic Glycolysis (CHOs)
Oxidative phosphorylation (lipids, proteins and CHOs)

Question 9

What is ATP Hydrolysis?

Answer 9

It is the catabolic reaction by which chemical energy stored in ATP is released

Question 10

Why is the ATP Hydrolysis process called this?

Answer 10

Because water donates hydroxyl group to Pi molecule.

Question 11

How does muscle contraction occur?

Answer 11

It occurs through the metabolism of ATP in both catabolism and anabolism.

Question 12

How much energy is produced when splitting an ATP molecule in 1 mole.

Answer 12

65kJ

Question 13

What are nucleotides?

Answer 13

Compounds such as ATP and ADP

Question 14

What are ATPases enzymes?

Answer 14

NA+
K+
CA2+
Myosin

Question 15

What are the two shapes the Myosin head form to?

Answer 15

Pre-power stroke conformation and

Rigor Conformation

Question 16

How much force does one myosin head produce?

Answer 16

5 pN or 5 Trillionths of a newton

Question 17

How much force does a whole muscle need at peak performance

Answer 17

100-1000 Newtons

Question 18

What are costameres?

Answer 18

Costameres bind to the very end of a muscle cell where a Z-discs would normally be. They are then attached to the tendons that pull the muscle towards the point of reference

Question 19

What is desmin filaments?

Answer 19

Desmin attach to the lateral sides of the sarcomere which hold them all together.