Which are the special proteins in muscles that contract and relax to cause movement?

 

A sarcomere is the basic unit of striated muscle tissue. It is the repeating unit between two Z lines.

Skeletal muscles are composed of tubular muscle cells (myocytes called muscle fibers or myofibers) which are formed in a process known as myogenesis. Muscle fibers contain numerous tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as alternating dark and light bands. Sarcomeres are composed of long, fibrous proteins as filaments that slide past each other when a muscle contracts or relaxes.

A muscle fiber from a biceps muscle may contain 100,000 sarcomeres.

Most bacteria divide by binary fission, a form of cell division in which DNA replication and segregation occur simultaneously. This process involves active partitioning of the single bacterial chromosome and positioning of the site of septation.

Bacteria reproduce by binary fission. In this process the bacterium, which is a single cell, divides into two identical daughter cells.

Binary fission begins when the DNA of the bacterium divides into two replicates. The bacterial cell then elongates and splits into two daughter cells each with identical DNA to the parent cell. Each daughter cell is a clone of the parent cell.

Polygenic inheritance involves the determination of a particular phenotypic characteristic by many genes, called polygenes(group of genes influencing a quantitative characteristic), each having a small effect individually.

Height and skin colour in humans are examples of Polygenic characters.

Eukaryotic cells are found in plants, animals and unicellular organisms.

The three main part of Eukaryotic cells are

1. Plasma membrane or membrane-bound organelles which carries out the cell functions.

2. Nucleus which contains the cell's DNA (and)

3. Cytoplasm which is a jelly like fluid interior of the cell.

Oxygen in our blood is transported by a protein named Haemoglobin.

The only transport method that can move species against their concentration gradient i.e, from low to high concentration is called Active transport.

Facilitated diffusion only moves species down their concentration gradient i.e, from high to low concentration.

Fermentation is the chemical breakdown of a substance by bacteria, yeasts, or other microorganisms, typically involving effervescence and the giving off of heat.

The two most common types of fermentation are

(1) alcoholic fermentation (and) 

(2) lactic acid fermentation.

(1) Alcoholic fermentation : the type of fermentation in which ethyl alcohol is the main end product .This is very common in yeast (unicellular fungus) and also seen in some bacteria. Yeast cells release enzymes called zymase complex which bring about the fermentation. The reactions are similar to anaerobic respiration.

(2) Lactic acid fermentation : The type of fermentation in which lactic acid is the end product.

It is carried out by some bacteria (e.g. lactic acid bacteria), and also by animals (muscle glycolysis in animals, under oxygen deficiency, results in the formation of lactic acid this is whay we experience in muscle cramps, or "Charley horse").