Sarcomere Coloring Answer Key

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You may come here because you are looking for information about the Sarcomere coloring answer key. Well, here I have the answer key for this, so you are able to check it below. And hopefully, it helps you understand more about sarcomere.

Sarcomere Coloring Answer Key

Here, you are asked to color the individual myofilaments (A) purple, these are composed of both thick and thin filaments. Then, there is also Mitochondria (B) which are dispersed through the muscle fibers and you have to color all mitochondria in pink. It is explained that recall that mitochondria supply energy that is needed for muscle contraction.

There are also two types of transport systems which are found within the muscle. There is the sarcoplasmic reticulum (E) which is a network of tubes that run parallel to the myofilaments. You are required to color this network green. The transverse tubules (C) run perpendicular to the filaments and you are required to color both yellow. The enter muscle fiber is surrounded by the sarcolemma (D) and you have to color this membrane brown.

Sarcomere Coloring Answer Key

Let’s say it is expanded. If so, the light and dark bands are shown as individual thick and thin filaments. You have to color the thick filaments (not labeled) red and the thin filaments blue. How about the Z line? It is the boundary between sarcomeres, named after its shape and you have to color the Z line orange.

You are able to see the complete answer for coloring it by accessing this:

About Sarcomere

Here is the explanation about sarcomere according to Wikipedia. A sarcomere is defined as the smallest functional unit of striated muscle tissue. Found between two Z-lines, it is the repeating unit. Tubular muscle cells can be found in skeletal muscles where the name is muscle fibers or myofibers and they are shaped during embryonic myogenesis. In the muscle fibers, there are numerous tubular myofibrils. In the myofibrils, there are repeating sections of sarcomeres which appear under the microscope as alternating dark and light bands.

Sarcomeres consist of long, fibrous proteins as filaments that slide past each other when a muscle contracts or relaxes. How about the costamere? It is a different component that connects the sarcomere to the sarcolemma.

There are two of the important proteins and those are myosin which shapes the thick filament and actin which shapes the thin filament.

Myosin has a tail which is long and fibrous and also it has a globular head which binds to actin. The head of myosin binds to ATP which is the source of energy for muscle movement. Myosin is only able to bind to actin when the binding sites on actin are exposed by calcium ions.

Actin molecules are bound to the Z-line which shapes the borders of the sarcomere. Other bands come up when the sarcomere is relaxed. It is important for you to know that the myofibrils of smooth muscle cells are not arranged into sarcomeres.


Here is the explanation about bands according to Wikipedia.

Skeletal and cardiac muscle has striated appearance from sarcomeres and it was first described by Van Leeuwenhoek.

  • A sarcomere has a definition as the segment between two neighbouring Z-lines (or Z-discs). In electron micrographs of cross-striated muscle, there is the Z line which appears in between the I-bands as a dark line that anchors the actin myofilaments.
  • The region of the I-band for isotropic is surrounding the Z line. I-band is the zone of thin filaments which is not superimposed by filaments which are thick (myosin).
  • A-band (for anisotropic) is something which follows the I-band. It is named for their properties under a polarized light microscope. In an A-band, it has the whole length of a single thick filament. The anisotropic band has both thick and thin filaments.
  • In the A-band, there is a paler region named the H-zone. It is named for their appearance which is lighter under a polarization microscope. H-band is the zone of the thick filaments which does not have actin.
  • In the H-zone, there is a thin M-line and it appears in the middle of the sarcomere shaped of cross-connecting elements of the cytoskeleton.

And here is the explanation about the relationship between the proteins and the regions of the sarcomere according to Wikipedia.

  • The major component of the I-band are Actin filaments which are the thin filaments and extend into the A-band.
  • Myosin filaments which are the thick filaments are bipolar and extend throughout the A-band. At the centre, they are cross-linked by the M-band.
  • The giant protein titin (connectin) extends from the Z-line of the sarcomere where it binds to the myosin (thick filament) system, to the M-band, where it is thought to interact with the thick filaments. Titin and its splice isoforms is the largest single highly elasticated protein which can be found in nature. It gives binding sites for numerous proteins and is thought to play an important role as sarcomeric ruler and as blueprint for the assembly of the sarcomere.
  • There is also another giant protein namely nebulin and it is hypothesised to extend along the thin filaments and the whole I-Band. Same as titin, it is thought to act as a molecular ruler along for thin filament assembly.
  • There are several proteins which are important for the stability of the sarcomeric structure and they can be found in the Z-line and also in the M-band of the sarcomere.
  • In the Z-disc, actin filaments and titin molecules are cross-lined via the Z-line protein alpha-actinin.
  • The M-band proteins myomesin and also C-protein crosslink the thick filament system namely myosins and the M-band part of titin or the elastic filaments.
  • Creatine kinase is also bound by the M-line where it facilitates the reaction of ADP and phosphocreatine into ATP and creatine.
  • In the A-band of the sarcomere, the interaction between actin and myosin filaments has the function for the muscle contraction based on the sliding filament model.

Most cells of muscle save enough ATP for only a small number of muscle contractions. While cells of muscle also save glycogen, most of the energy needed for contraction is derived from phosphagens. One of these phosphagen namely creatine phosphate, is utilized to provide ADP with a phosphate group for ATP synthesis in vertebrates.

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