Structure of myofibril, Biology

Assignment Help:

STRUCTURE OF A MYOFIBRIL -

  1. The dark bands of the myofibril are termed the A-bands (Anisotropic bands).
  2. Each A-band has at its middle a light zone called H-zone (Henson's line).
  3. The light bands are also called I-bands (Isotropic bands).
  4. Each I-band has at its centre a dark membrane termed the Krause's membrane or Dobie's line or Z disc or Z-line (Zwischenscheibe line).
  5. The sarcolemma is invaginated to form T -tubules (Transverse tubules).
  6. The T-tubules are present at the level of Z-line.
  7. The T-tubules form a simple mechanism of transportation of nuirients and carry the signals for contraction of the myofibrils from the sarcolemma to the interior.
  8. The part of the myofibril between two successive Z-lines is called sarcomere.
  9. Therefore, the sarcomere comprises A-band and half of each adjacent I-band.
  10. A sarcomere is about 2 to 3 mm long.
  11. The sarcomere is the functional unit of contractile system in muscle. In fact each sarcomere is a bundle of primary and secondary filaments.

204_structure of myofibril.png

(i)       Primary Filaments (= Myosin Filaments). The primary filaments are thicker and confined to the A-bands only.

They are free at both the ends. They are composed of myosin (protein) and bear minute projections called cross- bridges of the protein meromyosin.

(ii)      Secondary Filaments (= Actin Filaments). The secondary filaments are thinner and occur in I-bands, but extend for some distance into the A-bands between the primary filaments. This partial over lapping of the primary fila- ments by the secondary filaments gives dark appearance to the Abands. The secondary filaments are composed of the proteins actin, tropomysin and troponin. They are attached to the Z-lines by one end and are free at the other end. The secondary filaments are more numerous than the primary filaments. Six secondary filaments surround each primary filament. "

  1. The major component of muscle is water. Potassium is the most abundant mineral element in muscle.
  2. Other minerals such as sodium, calcium, phosphorus and magnesium are present only in traces.
  3. Muscles store glycogen. They have oxygen carrying pigment myoglobin or "muscle haemoglobin".
  4. Muscles also contain ATP, phosphocreatine, creatine, urea, etc.

Related Discussions:- Structure of myofibril

What factor cause the measurement to change, During gym class Sally noticed...

During gym class Sally noticed that her friend Melissa always ran faster than her. Sally knew that they exercised equally, so she wondered what could cause Melissa to run so fast.

Vagina, what is vagina explain with diagram

what is vagina explain with diagram

Points, What is the classification of protozoa with examples

What is the classification of protozoa with examples

How to removes hydrogen from fatty acids, Suppose you treated butter with a...

Suppose you treated butter with a fatty acid desaturase, an enzyme that removes hydrogen from fatty acids and creates double bonds. What would happen?

What is the significance of rhynchocoel, What is the significance of Rhynch...

What is the significance of Rhynchocoel? The unique body cavity of the Nemertean worms, which comprise the retractable proboscis. There is some debate on whether this is a true

Define the effects of deficiency of calcium in the body, Define the effects...

Define the effects of Deficiency of Calcium in the Body? If there is a continued inadequate intake or poor intestinal absorption of calcium, plasma calcium concentrations will

Define importance of nutrient and drug interaction, Define Importance of Nu...

Define Importance of Nutrient and Drug Interaction? Certain foods, beverages, alcohol, caffeine, and even cigarettes can interact with medicines. This may make them less effect

Ecology, What is the role of ecology to the evolution theory.

What is the role of ecology to the evolution theory.

Define functions of vitamin d, Define Functions of Vitamin D? Vitamin D...

Define Functions of Vitamin D? Vitamin D is required to maintain normal blood levels of calcium and phosphate, which are in turn needed for the normal mineralization of bone, m

Amelioration of mineral deficiency, Amelioration of mineral deficiency ...

Amelioration of mineral deficiency Performance of livestock in the tropics is mainly governed by the quality and quantity of nutrients provided in the diet. In most of the dev

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd