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Year2 - Committe 2 - Biochemstry > Biochemistry Of The Muscle Tissue > Flashcards

Biochemistry Of The Muscle Tissue Flashcards

(54 cards)

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1
Q

What are the three types of muscles ?

A
  • Cardiac muscle
  • Skeletal muscle
  • Smooth muscle
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2
Q

Why is muscle tissue is a major biochemical transducer (machine) ?

A

It that converts potential (chemical) energy into kinetic (mechanical) energy.

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3
Q

Since muscle is the largest single tissue in the human body what is the percentage of it babies, young adult and aged adult ?

A

25% in babies, more than 40% in young adult and less than 30% in the aged adult.

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4
Q

What are myogenic regulatory factors (MRFs) ?

A

They are DNA-binding transcription factors with a
helix-loop-helix (HLH) structure.

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5
Q

What is the 5 steps of Myogenic regulatory factors (MRFs) DNA-binding transcription factors ?

A
  • Myo D and Myf 5:controlled by PAX3 and PAX7 homeotic genes
  • Myogenin controls the myoblasts to be committed for terminal differentiation
  • Myo-D, an early marker of muscle differentiation (from stem cells to myoblasts)
  • Committed myoblasts do not divide, but fuse with each other and form multinucleated
    muscle fibers.
  • The number of muscle fibers does not change after birth.
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6
Q

What dose myostain inhibit ?

A

proliferation of myoblasts.

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7
Q

How dose Myogenic cells respond to myostatin by ?

A

downregulating the expression of Pax-3 and Myf-5,
transcriptional regulators of myogenic cell proliferation.

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8
Q

What is follistatin ?

A

(a myostatin inhibitor) increases
muscle mass .

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9
Q

What is follistatin ?

A

(a myostatin inhibitor) increases
muscle mass.

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10
Q

What dose mutations in the gene encoding lead to ?

A

leading to its inhibition explain the double muscled (muscular hypertrophy)

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11
Q

What are the three primary sources of ATP ?

A
  • Creatine phosphate (CP) cycle,
  • Anaerobic glycolysis,
  • Aerobic glycolysis and oxidative phosphorylation
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12
Q

What happens in the creatine phosphate cycle ?

A

ADP is converted back to ATP by donating
its phosphate to ADP by the catalysis
of creatine kinase (CK)/creatine
phosphokinase (CPK)

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13
Q

How long is the creatine phosphate cycle ?

A

up to 30 seconds (cells do not store high amounts of CP)

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14
Q

Why is creatine phosphate serves as the major source of energy ?

A

This form of energy generation neither produces
lactate nor requires oxygen.

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15
Q

Where is creatine formed during exercise is excreted ?

A

In urine

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16
Q

When dose the process of anaerobic glycolysis begin ?

A

As soon as muscle contraction starts.

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17
Q

How long dose the anaerobic glycolysis last ?

A

lasts from 30 - 60seconds.

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18
Q

What is the major substrate of anaerobic glycolysis ?

A

Muscle glycogen and some blood glucose.

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19
Q

What is formed as the end product of anaerobic glycolysis ?

A

Lactate

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20
Q

What is formed as the end product of anaerobic glycolysis ?

A

Lactate

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21
Q

What are the three types of energy metabolism ?

A

Crearine phosphate
Anaerobic glycolsis
Areobic glycolisis

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22
Q

What are the two muscles that are involved in the cori / lactic acid cycle ?

Study These Flashcards
A

Muscle and liver

23
Q

What happens in the liver in the cori / lactis acid cycle ?

Study These Flashcards
A

GLUCONEOGENESIS converts lactate to pyruvate and glucose. Glucose is transported to the muscle and lactate is produced by anaerobic glycolysis.

24
Q

What is the Cori / lactic acid cycle ?

Study These Flashcards
A

It is a metabolic pathway that links anaerobic glycolysis in the muscle tissue to gluconeogensis in the liver.

25
Why dose Muscles contain the highest mitochondrial content of any tissue in the body ?
In order to provide a massive amount of ATP for the movement and exercise.
26
Why dose Muscles contain the highest mitochondrial content of any tissue in the body ?
In order to provide a massive amount of ATP for the movement and exercise.
27
What are the two types of striated muscle cells ?
- Slow-twitch muscle (Red muscle): They contract slowly and they obtain their energy from aerobic metabolism: oxidative type cells. They appeared due to their heme content from myoglobin and mitochondrial heme containing proteins. - Fast-twitch muscle (white muscle): They contract rapidly and they obtain their energy mainly from anaeorobic glycolysis: nonoxidative type cells. It uses ATP faster than it can replace it. They appear light pink because they have few mitochondria but no myoglobin.
28
What is the structure of sarcomeres ?
Myofibrils composed of thick thick and thin filaments.
29
What are the thick and thin filaments of myofibrils maid from ?
- Thick filaments are composed of the protein myosin. -thin filaments are composed of the protein actin.
30
How dose the contraction of striated muscle fibers occur ?
the sarcomeres, linearly arranged within myofibrils, shorten as myosin heads pull on the actin filaments.
31
How much of thee muscle protein dose myosin II make ?
It is 55% of muscle protein, 4th most abundant protein in human body (Collagen, actin, hemoglobin, myosin and keratin).
32
What are the two types of trypsin treatment of myosin ?
1. Light meromyosin (LMM: Large part of the fibrous tail) has no ATPase activity and does not bind to F-actin. 2. Heavy meromyosin (HMM: Globular head + small fibrous tail; has ATPase activity and binds to F-actin (fibrous actin).
33
What is the thin filament is made from ?
• Globular/monomeric actin (G-actin) polymerizes to form actin filaments (F-actin) by the hydrolysis of ATP, where the Polymerization requires Mg++ and K+.
34
What is the function of tropomyosin ?
Two tropomyosin chains intertwine F-actin helix and stabilize it.
35
What is the function of troponin complexes ?
Troponin complexes are added on this structure at regular intervals: - TnC subunit binds Ca2+ - TnI inhibits binding of myosin to F-actin ,and TnT binds to tropomyosine
36
How dose tropomyosin work ?
Tropomyosin winds around actin filament and covers the myosin-binding sites to prevent actin from binding to myosin.
37
How dose transverse tubules ( T- tubules ) and sarcoplasmic reticulum ( SR ) work ?
invaginations of sarcolemma (plasma membrane) penetrating into skeletal and cardiac muscle cells
38
What dose t-tubules conduct ?
It conducts electrical charges
39
What dose sarcoplasmic reticulum do ?
It stores calcium and regulates intracellular calcium levels.
40
What is the function of ion channels in T-tubules ?
They allow for electrical impulses (action potentials) travelling along the sarcolemma, to enter rapidly into the cell, to initiate muscle contraction.
41
What are the 4 steps of muscle contraction ?
1. When a nerve impulse reaches a skeletal muscle cell, it causes a change in electric potential across plasma membrane (depolarization) 2. Ca2+ release from SR: rise in cytosolic Ca2+ (chemical signal), initiates contraction 3- Muscle contraction 4. Relaxation (Resting) of a Muscle Fiber: Ca++ ions are pumped back into SR by Ca-ATPase
42
How dose calcium controls muscle contraction ?
The first step for contraction is Ca++ to bind to troponin so that tropomyosin can slide away from the binding sites on the actin strands. 34 Sliding Filament Model for Muscle Contraction CALCIUM CONTROLS MUSCLE CONTRACTION This allows the myosin heads to bind to these exposed binding sites and form cross-bridges. Actin filaments are then pulled by myosin heads to slide past the thick filaments toward the center of the sarcomere.
43
What happens when a sliding filament is signaled by a motor neuron ?
A sacromere contracts, the thin and thick filaments overlap.
44
What is titin ?
It is a very large protein that contributes to the elasticity of striated muscle fibers.
45
What is the function of titin ?
It connects the Z line to the M line in the sarcomere, Titin is important in the relaxation of striated muscle tissues as it controls the assembly of myosin myofilament by acting as a template.
46
What happens if there is a mutation in the titin gene ?
It causes familial hypertrophic cardiomyopathy ( thickened heart muscle, the most common cause of sudden cardiac death ).
47
What is the calsequestrin ?
It is a a calcium-binding protein of the SR, helps SR store large amounts of Ca++ even though the concentration of calcium in SR is much higher than in cytosole SR Ca++ -ATPase actively pumps Ca++ back into SR where Ca rebinds to calsequestrin.
48
What is a dystrophin ?
It is a rod-shaped cytoplasmic protein, It is between the sarcolemma (muscle cell membrane) and the outermost layer of myofilaments in the muscle fiber, it links actin filaments to the surrounding extracellular matrix
49
What happens in the absence of dystrophin ?
Dystrophin supports muscle fiber strength, and the absence of dystrophin reduces muscle stiffness, increases sarcolemmal deformability,
50
What dose dystrophin deficiency cause ?
Duchenne’s muscular dystrophy which is an X-linked recessive degenerative muscle disease characterized by a defective dystrophin gene.
51
What are the 4 properties of cardiac myocytes ?
- found only in heart and tips of blood vessels. - do not fatigue. - contract rhythmically. - controlled by central nervous system and ‘’ pacemaker ‘’ cells.
52
What are the 5 properties of cardiac muscle cells ?
• Cardiac myocytes contract rhythmically. • Rhythmic contraction is controlled by extracellular Ca2+. • Ca2+ enters the cell through voltage-gated Ca2+ channels. • During rest, most of the cytosolic Ca2+ is exported from myocyte by Ca2+ - Na+ exchanger pump, the contribution of Ca2+ -ATPase is minor. • Contain many mitochondria and high amounts of myoglobin.
53
What are the 6 characteristics of smooth muscle cells ?
• They have a single nucleus and NO myofibrils. • They DO NOT contain troponin. • The sarcoplasmic reticulum is not as well developed as in the striated muscles. • T tubules are not present/rudimentary. • Smooth muscle contraction is also controlled by Ca2+ • Contraction starts with the phosphorylation of myosin light chain.
54
How is the smooth muscle contraction controlled ?
It is controlled by Ca2+ BUT in smooth muscle contraction Ca+2 binds to CALMODULIN not troponin

Year2 - Committe 2 - Biochemstry (3 decks)

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