First 3 weekly Quiz questions Flashcards
In animals, carbohydrates are stored as polysaccharides in muscle and other tissues as what?
Glycogen
During which phase of the cross-bridge cycle is ATP hydrolysed?
Return phase
The hydrolysis of ATP is what?
A catabolic reaction and an exergonic reaction.
The range of motion of a myofibrill is determined by the number of sarcomeres added in parallel within the muscle fibre.
false
The A-band is the portion of the sarcomere which consists of only actin (thin) filaments
False, the A band which is located in the middle of the sarcomere consists of thick (myosin) and thin (actin) filaments
How is the force generated within each sarcomere of a myofibril eventually transferred outside the cell to the tendon?
Longitudinal force transfer
The terminal sarcomere of a myofibril attached to the cell membrane via actin filaments to transmembrane protiens called costameres. These costameres in turn make rigor attachments to collagen fibrils and other structural proteins of the extracellular matrix
Lateral force transfer
The Z discs of parallel myofibrils are connected to each other via filamentous proteins called desmin. in turn the Z-discs nearest the sarcolemma are attached to the cell membrane via desmin to transmembrane proteins called costameres. The costameres form rigid attachments to structural proteins which run along the longitudinal axis of the muscle fibre in the ECM. These connective tissues eventually communicate with the musculotendinous junction at the end of each cell.
True or False? The thick filaments in a sarcomere are where tropomyosin and troponin are located
False, tropomyosin and troponin are located on the thin filaments within the actin strain.
The metabolism (breakdown) of glucose is coupled to what?
the production of ATP
Briefly describe the pathway that results in lactate production
lactate is produced when enzymes lactate dehydrogenase converts pyruvate into lactate using NADH and releasing NAD+
What is a exergonic reaction?
An exergonic reaction is a chemical reaction where their release of free energy and an endergonic reaction is a chemical reaction where energy is absorbed.
Cross-sectional area (CSA) of a muscle fibre is a good indicator of the cell’s what?
Maximal force-generating capacity
True or false, The “bare zone” of the myosin filament is responsible for the plateau in force at mid-range sarcomere lengths
True
There are 3 major connective tissues (sheaths) which divide and separate the macrostructure of a skeletal muscle. In descending order of scale they are:
Epimysium -> Perimysium -> Endomysium
Using what you know about enzymes catalysed reactions, describe the situation when this pathway will proceed.
Enzyme catalyzed reactions are driven by the concentration of substrate, so when there is a build-up of NADH and pyruvate in the cytosol this drives the conversion of pyruvate into lactate.
True or False, Force-generating capacity of a sarcomere continues to rise the further that it is stretched.
False
What best describes the nature of the force-velocity curve of a sarcomere?
force-generating capacity of a sarcomere rapidly increases the slower the velocity of shortening and rapidly declines the faster the velocity of shortening,
Is glycogenesis a producer of ATP within cells?
Glycogenesis is NOT a producer of ATP, Glycogenesis is the making of glycogen from glucose subunits, it does not produce ATP
What is a catabolic reaction?
Catabolic reactions break down larger molecules, such as carbohydrates, lipids, and proteins from ingested food
List 3 important points that occur within the power stroke phase of the cross bridge cycle.
Release of Pi from nucleotide binding site of myosin head causes conformational change in position of the S1 fragment
The movement of the myosin head (S1) from the pre-power stroke to the rigor conformation is called the power stroke
At the end of the power stroke phase ADP is released from the nucleotide binding site on the myosin head
The hydrolysis of ATP, and its subsequent release of free energy is NOT involved in the power stroke phase of the cross-bridge cycle. This energy is used to cock the myosin head into a pre-ppower stroke conformation and it is consumed during the return phase of the cross bridge cycle.
True or False, G-Actin refers to a single molecule of actin (in it’s globular form)
True
The total amount of ATP produced by the LDH reaction which produces lactate from pyruvate is what?
Zero, the products of this reaction are NAD+ and lactate
List the methods of ATP resynthesis in order of Fastest to slowest
Immediate energy systems (myokinase and creatine kinase reactions) Glycolysis + LDH (Anaerobic glycolysis) Glucose oxidation (Aerobic glycolysis) Fatty Acid Oxidation
What causes “rigor mortis”?
Failure to supply the vacant nucleotide binding site of the Myosin head with a fresh molecule of ATP
How many “heads does a single molecule of myosin have?
2 heads
A sarcomere is a series of myofibrils added end-to-end to form a long cable-like structure
False. Myofibrils are made up of thick and thin myofilaments, which help give the muscle its striped appearance.
Given that the conversion of pyruvate into lactate does not produce ATP, what does the cell “get” out of the pathway?
The release of NAD+ when converting pyruvate into lactate can then be used as a substrate in the earlier step in the breakdown of glucose to pyruvate. Allowing that process to continue which does produce ATP.
True or false, force generating capacity rapidly declines at very short sarcomeric lengths
True
