Answer:
Ligand-receptor interaction is the first interaction that triggers cell signalling.
Ligands are the hormones, drugs or neurotransmitters that specifically bind with receptors present in cell surface to initiate cell signalling. Ligand binding to the receptor is reversible. Binding of the ligand to the receptor can activate or inactivate receptor. Activation may lead to cell signalling pathways. Inside cells, there are secondary molecules which on activation starts a cascade of reactions. which in-turn regulate the function of the ligand molecule.
At first, the activated receptor relates with G proteins molecules in the cell.
before the ultimate physiological effect of the ligand on the cell's behavior is produced Therefore, the cellular signaling starts as soon as the first messenger (the ligand) binds to its receptor.
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Answer:
Here are the correct order of events that show evolution of the universe:
- Inflation
- Separation of last two fundamental forces
- Formation of subatomic particles
- Nucleosynthesis
- Formation of first stars
Explanation:
According to big bang theory, there were series of events carried on that lead to the formation of stars in the universe.
- Inflation was the time when universe began to expand at extremely fast pace.The dimensions of that old universe during the fraction of a second expanded by a factor of at-least 10^26 to 10 cm. Elementary particles like quark began to expand into the thin layer of universe.
- A strong nuclear force separated from its other two forces and the interactions between already created particles lead to the formation of more particles like Higgs bosons, W and Z etc.
- When the universe began to cool down below 10 quadrillion degrees, neutrinos, electrons and quarks began to form. Antiquarks and quarks annihilated with each other in a process called baryogenesis, this lead to the formation of matter.
- When the universe began to cool down below a billion degrees, the atomic nuclei begin to form when neutrons and protons combined by fusion reactions. The initially created nuclei were of simplest elements like helium, hydrogen and lithium.
- The period between the formation of first stars and atoms is called as dark age because there were no stars at that time. The formation of stars and galaxies was made 300 - 500 million years later. When the universe was kept expanding, gas pockets and gases became more and more dense. The small gas particles were collapsed under own gravity and became so hot that fusion reactions were triggered in them. Fusion between hydrogen atoms was the reaction which lead to the formation of most primitive stars.
Synovial membranes are connective tissue membranes that line the cavities of the freely movable joints such as the shoulder, elbow, and knee.
Membrane
A membrane is a selective barrier; it lets some items pass but prevents others from doing so. These entities could be ions, molecules, or other tiny particles. Biological and manufactured membranes are the two broad categories into which membranes can be placed. Cell membranes, which are the exterior coverings of cells or organelles that permit the passage of specific components, nuclear membranes, which enclose the cell nucleus, and tissue membranes like mucosae and serosae are all examples of biological membranes. Humans create synthetic membranes for use in laboratories and industries (such as chemical plants).
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