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

Cytoplasmic bridge formed during the conjugation of paramoec, Cytoplasmic b...

Cytoplasmic bridge formed during the conjugation of paramoec: The two paramoecia that undergo conjugation are called conjugants. During conjugation, the two conjugants com

Proteins, what is he importance of proteins for living beings

what is he importance of proteins for living beings

Membrane protein purification and reconstitution, The first step of the pur...

The first step of the purification of an integral membrane protein is to disrupt its interactions with other integral proteins and the lipids in the membrane.  This is commonly ach

Define bioactive substances from protein foods, Define Bioactive Substances...

Define Bioactive Substances from Protein Foods? Bioactive substances are derived from living organisms that can be used by humans for a variety of applications. They are consti

Determine the digestion of carbohydrates, How does the pancreatic juice res...

How does the pancreatic juice resume the digestion of carbohydrates? What is the involved enzyme? Carbohydrate digestion starts with the action of the salivary amylase (ptyalin

Myocardial contractility, Inspiration decreases the pressure in the central...

Inspiration decreases the pressure in the central veins and thus increases the pressure gradient between the peripheral and central veins thus augmenting venous return. Skeletal mu

Do algae reproduce asexually or sexually, Q. Do algae reproduce asexually o...

Q. Do algae reproduce asexually or sexually? There are algae that reproduce asexually, There are algae that reproduce sexually and. In unicellular algae reproduction is usually

Endothelium - ovule, Endothelium - Ovule In plants bearing unitegmic o...

Endothelium - Ovule In plants bearing unitegmic ovules, the nucellus degenerates during early stages of ovule development and the embryo sac comes in contact with the innermos

Explain what is probing depth, Q. Explain What is Probing Depth? This p...

Q. Explain What is Probing Depth? This parameter is applicable to one stage implants when they are evaluated prior to prosthetic phase and used to evaluate the health of the im

Main means by which autotrophic beings obtain energy, What is the main mean...

What is the main means by which autotrophic beings obtain energy? The major means by which autotrophs obtain energy is photosynthesis (There are also chemosynthetic autotrophs)

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