Transportation through the cell membrane

Transportation of substances across the cell membrane is essential to the life of a cell. Various substances must have moved into cells because they help to support metabolic reactions. This process is classified into two process these are Passive mechanism and Active mechanism.

Transportation through the cell membrane:-

Transportation of substances across the cell membrane is essential to the life of a cell. Various substances must have moved into cells because they help to support metabolic reactions.

Transportation process classified into two mechanisms:-

  1. Passive Mechanism
  2. Active Mechanism

Passive Mechanism (Diffusion) Transportation:-

It is the transportation of substance along the concentration gradient or electrical gradient or both (electrochemical gradient)is called Passive Transport.

In other words, it is the not movement of a substance from higher concentration to lower concentration, it is called Diffusion.

It is two types:-

  1. Simple Diffusion
  2. Facilities Diffusion

Simple Diffusion:- Simple diffusion is acquiring through the lipid layer and also acquire through the protein layer.

Example:-Gas exchange between alveoli and blood capillaries, oxygen diffused in alveoli to blood capillaries, and carbon-dioxide diffused from blood capillaries to the alveoli.

Facilities Diffusion:- In this type of diffusion some transport protein help in the transport of a substance.

Example:- Glucose and amino acid are transport by the facilities’ diffusion.

Osmosis:-

It is the movement of the from higher concentration to the lower concentration through a semi-permeable membrane.

In a living system, the solvent is water which moves by osmosis across the cell membrane from an area higher water concentration to lower water concentration.

Osmosis is a passive process in which water moves through a selectively permeable membrane from an area of lower solutes concentration to an of higher solute concentration.

Example:-Absorption of water by stomach and colon Re-absorption of water by tubules of the nephron.

Active Mechanism:-

Active transport is the movement of the molecule across a cell membrane against their concentration and electrical gradient.

It is an active process because energy is required for the transported protein to move solute across the cell membrane against their concentration and electrical gradient.

Active transport is of two types:-

  1. Primary Active Transport:- Transport or substance across the cell membrane against its concentration gradient by pumps. Transmembrane protein uses energy supplied by ATP. Example :- Na+,K+, ATPase pump.
  2. Secondary Active Transport:- Coupled of two substances across the cell membrane using energy supplied by the electrochemical gradient.
  • Anti-porter:- Antiporter moves ion and other ion in opposite direction across the cell membrane.
  • Symporter:- Symporter moves glucose and amino acid in the same direction across the cell membrane.

Fluid Mosaic Model and Cell Membrane

Cell Membrane and Fluid Mosaic Model

Q. Explain the fluid mosaic model of Singer and Nicolson ? or Structure of cell membrane by the fluid mosaic model?

The structure of the cell membrane is explained by the fluid mosaic model of Singer and Nicolson.

According to this model cell membrane is consist of three parts:-

  1. Lipid
  2. Protein
  3. Carbohydrate

1. Lipid:-

The structural framework of cell membrane is lipid by layer which consist of three types of lipid molecule:-

  • Phospholipid
  • Cholesterol
  • Glycolipid

Phospholipid:- It is formed by phosphate and fatty acid. The outer part of the phospholipid layer is the head which made up of phosphate.

The inner part is the tail portion which consists of fatty acid, this part is hydrophobic. The hydrophobic head part faces the ECF outside the cell and ICF inside the cell.

Cholesterol:- Cholesterol molecules are arrangements to act the phospholipid in the membrane to provide structural stability to the cell membranes.

Glycolipid:– It is formed when lipid attached to the carbohydrate. Glycolipid present on the outer surface of the cell.

2. Protein:-

The protein layer of the cell membrane situated on either side of the lipid layer. These protein molecules are classified into two groups:-

  • Integral Protein
  • Peripheral Protein

Integral Protein:- The integral protein is also known as Trans-membrane Protein are tightly adheres to the cell membrane. These portion molecules are pass through the entire fitness of the cell membrane from one side to another side.

Peripheral Protein:- They are also known as Peripheral Membrane Protein. Peripheral protein does not penetrate the cell membrane but partially embedded in the outer and inner surface of the cell membrane.

3. Carbohydrate:-

The Carbohydrate layer is consists of 2-6o monosaccharide change they may be branched or straight.

Some carbohydrates are attached to the lipid called Glycolipid and some carbohydrates are attached to protein are called Glycoprotein.