Active and Passive Transport.

                 
                              Active Transport

Active transport:  Active transport means the movement of particles from areas of low concentration to areas of high concentration by requiring energy in the form of ATP against electrochemical gradient.

Example: Sodium -potassium pump in cell membrane.

Active transport can be divided into two aways.

1) Primary active transport.

2) Secondary active transport.

1) Primary active transport:  

These are generally use energy directly from hydrolysis of ATP molecule.

Primary active transport can perform by

* Sodium potassium pump.

* Calcium pump.

* Hydrogen potassium pump.

* Hydrogen protein pump.

Sodium potassium pump: 

Present in all Eukaryotic cells.

The pump maintains sodium potassium concentration difference across the plasma membrane.

Created a negative electrical charge inside the cell electronic pump.

This pump is essential for Oxygen utilization by the kidneys.

Calcium pump: 

Calcium ions are generally maintained at extremely low concentration in the intracellular cytosol of virtually all cells in the body.Concentration of intracellular is 10,000 times less than extracellular fluid.

It is achieved mainly two primary active transport calcium pump.

I) One is in the cell membrane and pumps calcium to the outside of the cell.

II) The other pump calcium ions into one or more of the intercellular vescicular organalles of the cell such as the sacroplasmic reticulum of muscle cells and the mitochondrial in all cells.

Hydrogen potassium pump ( H+/K+ ATPase)

Gastric gland:

In gastric gland pareital cells ( secretion HCL ) pumps hydrogen ions into the gastric lumen in exchange for potassium.

Renal tube:

Intercalated cells in the late distal tubules and cortical collecting ducts secretion of hydrogen ion reabsorbtions of potassium ion.

Proton pump (H+ATPase )

It is present in lysosome and also reticulum.

Pumps proton from cytosol into these organalles.

Secondary active transport (co- transporter)

Energy utilized in the transport of one substance helps in the movements of the other substance.

Energy is derived secondarily, from energy that has been stored in the form of ionic Concentration differences of secondary molecule or ionic substance between two sides of a cell membrane created originally by primary active transport.

The secondary process is also used to store high energy hydrogen ion in the mitochondria of plant and animal cells for the manufacture of ATP.

Secondary active transport can be follow three event:

Uniport: A uniporter carries one molecule or ion in a direction.

Symport: A symporter carries two molecules in a same direction.

Antiport: A antiporter carries two molecules in different of opposite direction.

  

Four major Active transport:

1) Exocytosis: A process in which the vescicle fusing with the plasma membrane and releasing their contents to the outside of the cell.

2) Endocytosis: It is a process in which a cell surround takes in materials from it's environment.

The particle does not pass through the cell membrane. It is simply engulfed and enclosed.

3) Pinocytosis:  The ingestion of liquid into a cell by the budding of small vescicle from the cell membrane.

4) Phagocytosis: once the vescicle has formed , it travels into the cytoplasm where it will fuse with lysosome that will kill and digest the engulfed material.

Figure: Phagocytosis process.

           


            Plasma Membrane Transport

Introduction:   Plasma membrane is a selectively permiable barrier between the cell and it's extracellular environment.

The permiability properties ensure that essential molecules such as glucose , amino acid, ions and lipids readily enter the cell, and the waste substances leave the cell.

Movement of all molecules and ions across cellular membrane is mediated by selective membrane transport proteins embedded in the phospholipid bilayer.

Passive Transport:

Passive transport: Passive transport means the movement of particles from the areas of high cocentration to areas of low concentration without requiring energy.

Types of Passive transport:

I) Diffusion.
II) Facilitated diffusion.
III) Osmosis.

I) Diffusion:

Oxygen, Carbondioxide, Water, Amino acid, molecules are small to diffuse across plasma membrane.

Proteins, carbohydrates and other ions are too large to diffuse across plasma membrane.





Diffusion is the movement of small particles across a selectively permiable membrane like the cell membrane until the condition is reached to equilibrium.
Water, lipid, lipid soluble substances can pass through plasma membrane by the process of diffusion.

II) Facilitated diffusion:

Some ions diffuse through channel protein. The pores remain always open or open in response to a stimuli. In this case energy is not required so it is called passive transport. Specific particles such as sugars, amino acids, ions can diffuse in to the cell.

Carrier protein: Transport non charged molecules with a specific shape.

Channel protein: Tunnel shape that transports very small charged molecules.

III) Osmosis:

Osmosis is the diffusion of water through a selectively permeable membrane such as plasma membrane . Water diffuses across a membrane from less to more concentration.

Osmosis is the diffusion of water across the cell membrane .

The direction of Osmosis depends on the concentration of solutes inside and outside of the cell.

Types of Osmosis Transport:

Isotonic solution: solute and water concentrations equal on both sides of membrane. Water molecule will move both ways randomly to maintain equilibrium.

Hypotonic solution: concentration of solutes outside of the cell is lower than the concentration of inside. Water will move into the cell to creat equilibrium.

Hypertonic solution: concentration of outside of the cell is higher than inside. Water will move out of the cell to creat equilibrium .

Equilibrium: All molecule occupy the same amount of space.

          Active and Passive Transport

 1 Mark Questions:

1. What is required for Active transport to occur?
2. What is meant when a membrane is describe as " Semipermeable"?
3. How does facilitated transport differ from diffusion?
4. Mention an advantage of Passive transport.
5. Why is facilitated diffusion a type of Passive transport?
6.What size molecules can pass through a membrane by a process called passive transport.
7. State a major difference between Active and Passive transport.
8.What is Osmosis?
9. Write the definition of Diffusion.
10. What will happen to a cell when it is placed in a hypotonic solution?

2 Mark Questions:

1. What is Integral and peripheral protein? Mention their functions.
2. Explain the following terms:
Diffusion, Active and Passive transport, Exocytosis and Endocytosis, Hypotonic, Hypertonic, Isotonic solution.
3. How you differ simple diffusion from facilitated diffusion.
4. Discuss the similarities and difference between diffusion and Osmosis.
5. What would happen to a cell in following solutions ( Describe and illustrate )
I) Isotonic
II) Hypotonic
III) Hypertonic
6. How Osmosis different from Diffusion? How is it the same?
7. What is the difference between Active and Passive transport.
8. Mention the general function of Plasma membrane.
9. What is Phagocytosis? Give an example of phagocytic cell in human body.
10. What do you mean by Pinocytosis? 


                  Plasma membrane

Q1.Give a chemical composition of plasma membrane.

Ans: Protein 60 - 80%

          Phospholipid 20 - 40%

          Cholesterol and carbohydrate present             in small amount.

Q2. How many types proteins are present in plasma membrane ?

Ans: Two types of protein present in plasma membrane. These proteins are 

1) Peripheral protein.

2) Integral protein.

Q3. Who first proposed the fluid mosaic model?

Ans: S.J. singer.

Q4. Sandwich model given by _________.

Ans: Davson.

Q5. What is simple diffusion?

Ans: Simple diffusion is the movement of the molecules from area of higher concentration to lower cocentration called simple diffusion.

Q6. What do you mean by facilitated diffusion?

Ans: The movement of molecules through the protein molecule from higher concentration to lower concentration known as facilitated diffusion.

Q7. Mention two major functions of plasma membrane.

Ans: A) Cell membrane allows some substances to moves in and keens other out. It is known as selective permiability.

B) There are sites for receptors contain specific cell identification marker. The markers differentiate cell type from other cells.

Long questions: 7 marks.

1) Describe different structures of plasma membrane.

2) Describe fluid mosaic model.

3) Give an account of different movement across plasma membrane.                           _____________