BIOL 207 Study Guide - Final Guide: Curare, Esterase, Active Transport
30 May 2018
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EXAM 3
• there are 4 basic types of proteins that make up muscle cells called…
Myofilaments
• Myosin - thick. has crossbridges
• actin - thin. around the crossbridges
• troponin - tiny and attached to actin
• tropomyosin - tiny and attached to actin
• the TT Complex is the troponin and tropomyosin working together. attached to actin
arranged on top of each other. they are studded along
• these 4 proteins (myosin, actin, troponin, tropomyosin) are arranged in perfect register.
there will be another myosin, actin etc arranged right aligned with the other.
• striated muscle gets its striations from the arrangement of these proteins (light, dark,
intermediate zones and bands due to the different thickness of myofilaments (actin, myosin,
troponin and tropomyosin))
• viewing from a microscope seeing lighter, darker, intermediate areas. this is what gives
striated muscle its characteristic. light, dark, intermediate zones and bands.
• a sarcomere are lined up in tandem, within the entire length of a muscle cell.
• sarcomere: the basic contractile unit of striated muscle
• when muscles contract all the sarcomeres contract
• sarcolemma: the muscle cell membrane
• myofibril: a long line of sarcomeres
• myofibril: a threadlike structure running longitudinally through a striated muscle fiber,
consisting mainly of myosin and actin myofilaments and their associated TT complexes. a series
of sarcomeres arranged in tandem. 80% of volume of striated muscles
• these sarcomeres will join to form a myofibril
• there will be many myofibrils in a given muscle cell. all their sarcomeres are in perfect
register/alignment with each other. this is why the entire muscle cell has light and dark lines.
• the TT complex plays a critical role in muscle contraction
• the light area is known as the I Band. there is no overlap at all, just possibly actin. it
represents the actin of two adjacent sarcomeres are located
• the area that expresses the width of the myosin is known as the A Band
• the middle of the A Band has the H Zone. this represents the area of the sarcomere
where you don’t have overlap of actin and myosin. it is just myosin.
• the Z Disc/Z Line is the entire width of a sarcomere on either side of each sarcomere
• the Z Disc/Z Line represents the point of junction between two sarcomeres
• muscle fibers are made up of many myofibrils which themselves are compromised of
numerous myofilaments which are arranged in sarcomere units than run in tandem
• there are 100s-1000s of myofibrils in a muscle cell running parallel (all of the sarcomeres
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of myofibrils line up perfectly which results in light and dark spaces creating striations in muscle
cells
• muscle fiber is a muscle cell
• myofilaments are myosin, actin, troponin and tropomyosin
• sarcomere is the basic contractile unit of striated muscle
• myofibrils are the threadlike structure running longitudinally through a striated muscle
fiber
• sarcolemma is the muscle cell membrane
• sarcoplasm is the stuff in between the proteins
• myofibrils represent a series of sarcomeres arranged in tandem
• all the nuclei in striated muscle are all arranged along the subsurface area of the cell
membrane. in the middle is the sarcoplasm and within the sarcoplasm there is a high
concentration of proteins. the sarcomere units are arranged in tandems
• 80-85% of a muscle cell is made up of all myofibril. myofibrils themselves are made up
of sarcomeres. sarcomeres themselves are made up of actin and myosin with the troponin and
tropomyosin attached to the actin
• muscle fibers are made up of many myofibrils, which are themselves comprised of
numerous myofilaments, which are arranged in sarcomere units that run in tandem
• when exercising (lifting) you are not increasing the number of muscle cells, but
increasing the number of actin and myosin. you are synthesizing more protein, and as a result
have more myofibrils in that cell and the muscle cell gets bigger, and therefore the muscle gets
bigger
• 80+ percent of muscles consist of myofibril proteins
• The A I Interface is where the I band meets up with the A band (at the edge of myosin
filament). this is where critical organelles of the muscle cells are located.
• Triad represents the existence of two critical, very important organelles, without which
the muscles would never contract. those two organelles are called…
• Sarcoplasmic reticulum is found traveling throughout the entire length of the striated
muscle cell, however, periodically that sarcoplasmic reticulum gives off branches, and those
branches surround each myofibril. those branches are referred to as cisternae or lateral sacs.
these collect calcium ions. so the principle function of the cisternae under normal circumstances
is to horde calcium ions. most of the calcium ions are found in the cisternae or lateral sacs (at
rest). they are found here
• transverse tubules (the T system) originate on the surface of the cell membrane,
periodically at every A I Interface. they run transversely to the axis of the cell. the function of
these is to transmit the impulse (action potential) along the surface of the cell membrane into
the cell.
• action potentials only occur across cell membranes because the resting membrane
potential, that unequal distribution of ions, is either on the outside or the inside, but if you want
something going on inside the cell there is need to transmit that action potential further down
and that is what the transverse tubules do.
Molecular Mechanism of Muscle Contraction - SFM: Sliding Filament Mechanism (pgs. 287,
288. figure 9.12, 9.13 on pgs. 292-295)
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Document Summary
There are 4 basic types of proteins that make up muscle cells called . Molecular mechanism of muscle contraction - sfm: sliding filament mechanism (pgs. 80+ percent of muscles consist of myofibril proteins. The a i interface is where the i band meets up with the a band (at the edge of myosin. This is an enzymatic capability that splits atp. When atp is split, it splits into adp+pi. When atp is split by atpase it gives rise to adp+pi. Because of the splitting of this high energy bond that energy is released. A lot of body temperature/heat is the result of atp splitting. Some of the energy is captured, some of it is lost as heat. Whenever atp lands on the cross bridge, immediately atp splits into adp+pi. In due time the adp+pi will be recycled in cell respiration to form new atps.
