Question

What are the three major components of plasma membranes and their functions? How is osmosis a type of diffusion? In what ways is the plasma membrane selectively permeable? What happens to plant and animal cells placed in hypotonic, Isotonic, and hypertonic solutions? How are passive and active transport different? How do membrane transport proteins function? What molecule is the "energy currency of cells? What does this mean? How do enzymes speed up chemical reactions? What factors influence the activity of enzymes? How do they cause this change?

Answer 1

1. Plasma membrane defines the border of the cell as well as maintain it's contact with environment in a controlled manner. The 3 major components of plasma membrane and their functions are;

a. Phospholipids - In the form of bilayer consisting of lipid made of glycerol, two fatty acid tails and a phosphate head and makes a semipermiable membrane between cells and outside environment.

b. Proteins - Performs the cross membrane transportation and cell communication.

c. Crabohydrates (sugars and sugar chains) - These molecules help cells recognize each other.

2.

• Osmosis is a process in which solvent particles moves from a dilte solution into a concentrated solution through a passive membrane whereas diffusion involves movement of particles from an area of higher concentration to lower concentration till it is equalize throughout the medium.
• So, osmosis and diffusion both a show similarity in balancing the concentartion of two solutions.
• Also these both are a passive process i.e. these do not require any external energy to occur.

3.

• Plasma membrane plays an important role in the maintanance and functions of cells and organisms.
• Plasma membrane has a selective permiability property i.e. only small, polar and hydrophobic molecules can diffuse through it but not ion or proteins.

4.

• Hypotonic solution - Hypotonic solution means extracellular fluid has less osmolarity than the fluids inside the cell. When a cell is placed in a hypoteonic environment becuase of the entry of water molecule, it will swell.
• Hpertonic solution - When a cell is placed in a hypertonic environment it will lose the water and shrink because of the higher osmolarity of the extracellular fluid.
• Isotonic solution - In this case the extracelullar fluid has the same osmolarity as the cell and there will be no movement of water inside or outside the cell and hence, no effect on the cell.

5.

• Both active and passive transport involve the movment of moleule across cell membrane.
• The key distinction between these two processes are - use of energy and concentration gradient.
• Active transport uses energy whereas passive transport does not.
• Active transport involves movement of molecules froma higher of low concentration to an area of low concentration (i.e. against the concntaraion gradient ) where as passive transport involves movement of molecules from an area of higher concentarion to low concentartion (i.e. from higher to lower conc. gradient).