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Questions and Answers

Which type of muscle is characterized by having striations and being under voluntary control?

Skeletal muscle (correct)

Smooth muscle

Cardiac muscle

All muscle types

What happens when troponin is fully saturated with Ca2+?

Tetanus occurs (correct)

Cross-bridge cycling slows down

Cross-bridge cycling stops

Calcium uptake is enhanced

What protein does calcium bind to in smooth muscle to initiate contraction?

Troponin

Tropomyosin

Actin

Calmodulin (correct)

What primary role does tropomyosin play in skeletal muscle contraction?

Blocking myosin binding sites on actin Signup and view all the answers

Which reaction describes the energy production from ATP?

ATP → ADP + P + Energy + Heat Signup and view all the answers

Which feature is exclusive to cardiac muscle among the three muscle types?

Intercalated disks Signup and view all the answers

What is produced during glycolysis from one molecule of glucose?

2 ATP Signup and view all the answers

How many ATPs are produced from the complete oxidation of one glucose molecule, including the Krebs cycle and electron transport chain?

38 ATP Signup and view all the answers

During a twitch contraction, what occurs during the latency phase?

Calcium is released from the sarcoplasmic reticulum Signup and view all the answers

What is the role of creatine kinase in the energy production process?

Assists in converting PCr to creatine Signup and view all the answers

Which type of muscle fibers can undergo summation and produce greater tension?

Skeletal muscle fibers Signup and view all the answers

What is the primary source of calcium for contraction in smooth muscle compared to skeletal muscle?

From extracellular space and sarcoplasmic reticulum Signup and view all the answers

What byproduct is produced when glycolysis occurs without oxygen?

Lactic acid Signup and view all the answers

What is the main difference in the action potential between skeletal and cardiac/smooth muscle?

Cardiac and smooth muscle AP involves different sources of calcium Signup and view all the answers

How many NADH molecules are produced from one molecule of glucose in the Krebs cycle?

6 NADH Signup and view all the answers

What is the main source of energy production through aerobic pathways from fats?

Fatty acids Signup and view all the answers

Which statement about the reverse reactions in glycolysis is true?

They can produce glucose from pyruvic acid Signup and view all the answers

What is the total ATP yield from one palmitic acid molecule during complete oxidation?

387 ATP Signup and view all the answers

Study Notes

Muscle Types

Skeletal Muscle: Striated, voluntary, multi-nucleated, involved in somatic nervous system, has specific neuromuscular junctions
Smooth Muscle: Non-striated, involuntary, involved in autonomic nervous system, has varicosities (diffuse innervation) and gap junctions
Cardiac Muscle: Striated, involuntary, involved in autonomic nervous system, has gap junctions and intercalated disks

Muscle Contraction Mechanisms

Skeletal and Cardiac Muscle: Calcium binds to troponin-C, triggering a conformational change that moves tropomyosin. This exposes the myosin binding site on actin, allowing cross-bridge formation and contraction.
Smooth Muscle: Calcium binds to calmodulin, activating myosin light chain kinase (MLCK) which phosphorylates myosin light chains. This phosphorylation permits myosin to bind to actin, triggering contraction.

Depolarization in Muscle Types

Skeletal Muscle: Action potential triggers calcium release from the sarcoplasmic reticulum
Cardiac and Smooth Muscle: Different mechanisms for action potential and calcium source

Twitch Contraction

Definition: Contraction in response to a single action potential
Characteristics: All-or-nothing for a muscle fiber, can be induced in a fiber, motor unit, or whole muscle
Phases: Latency (time delay between stimulation and E-C coupling), contraction (cross-bridge cycling), relaxation (calcium uptake)

Frequency and Summation

Factors: Action potential duration (2ms), contraction duration (10-200ms), tension dependent on intracellular calcium concentration
Mechanism: Increase in stimulation frequency leads to increased calcium release and longer calcium duration, leading to increased tension and force.
Tetanus: Occurs when the system is saturated with calcium (all troponin bound) and cross-bridge cycling is maxed out, resulting in a sustained contraction.

Energy Production - ATP

How ATP provides energy: ATP breaks down into ADP, phosphate, and energy through a catabolic reaction, releasing heat.
ATP Stores: Sufficient for only a few seconds of maximal work

Energy Production - PCr System

Mechanism: PCr breaks down into phosphate, creatine, and energy, facilitated by creatine kinase. The released energy is used to synthesize ATP from ADP and phosphate.

Energy Production - Glycolysis

Process: Breakdown of glucose (6-carbon molecule) into two pyruvic acid molecules (3-carbon) through 10 enzyme controlled reactions.
Net Gain: Produces 2 ATP molecules
Reversibility: All reactions are reversible

Energy Production - Aerobic Pathways

Krebs Cycle: Series of reactions leading to net production of 2 ATP, 6 NADH, and 2 FADH2 per glucose molecule.
Electron Transport Chain: Utilizes NADH and FADH2 to produce approximately 30 ATP and 4 ATP respectively.
Total ATP Production: 38 ATP from complete oxidation of glucose (Krebs cycle and electron transport chain).

Energy Production - Triglycerides

Breakdown: Triglyceride broken down into glycerol and fatty acids.
Glycerol: Enters glycolysis, Krebs cycle, and ETC, producing 15-19 ATP.
Fatty Acids: Broken down by beta-oxidation, producing acetyl CoA which enters the Krebs cycle and ETC. Each fatty acid produces 129 ATP.

Energy Production - Free Fatty Acids

Breakdown: Free fatty acids are broken down by beta-oxidation, producing acetyl CoA which enters the Krebs cycle and ETC, providing 129 ATP.
Total ATP Production: 387 ATP from the breakdown of 3 fatty acids.