Tag: bio-chemistry

Questions Related to bio-chemistry

A cell membrane controls what goes in and out of the cell. Because of the hydrophilic and hydrophobic regions of the phospholipid bilayer, small nonpolar molecules cross the membrane easily, while large and hydrophilic molecules cannot cross easily.
The term used to describe this differential movement of molecules across a membrane is

bio-chemistry absorption by roots - the processes involved diffusion transport across membrane means of transport

  1. Passive transport

  2. Selective permeability

  3. Osmosis

  4. Diffusion

Show answer
Correct Option: B
Explanation:

Selective permeability is the membrane's ability to differentiate between the molecules crossing it.

Passive transport is the movement of molecules across the membrane along their concentration gradient with the help of carrier proteins.
Osmosis is the movement of solvent from a solution of low solute concentration to a solution of high solute concentration across a semipermeable membrane.
Diffusion is the movement of molecules from a region of high concentration to a region of low concentration.
So the correct answer is 'Selective permeability'.

A cell membrane regulates which substances can enter and leave the cell based on their size and polarity . Which mode of cell transport is the movement of a substance from a high concentration to an area of lower concentration without the use of protein channels or energy?

bio-chemistry absorption by roots - the processes involved diffusion transport across membrane means of transport

  1. Simple diffusion

  2. Facilitated diffusion

  3. Osmosis

  4. Active transport

  5. Isotonic

Show answer
Correct Option: A
Explanation:
A. Simple diffusion is the net movement of particles of a substance from a region of greater or higher concentration to a region of lower concentration due to their own intrinsic kinetic energy. In simple words, it is a passive movement of molecules along their concentration gradient.
B. Facilitated diffusion is the passive movement of molecules along their concentration gradient with the help of membrane proteins known as channel proteins or carrier proteins.
C. Osmosis is the diffusion of water molecules through a semipermeable membrane along the concentration gradient.
D. In Active transport, molecules are carried from a region of lower concentration to a region of higher concentration against the concentration gradient with the utilisation of ATP.
E. Isotonic solution is a solution with equal solute concentrations to one another and thus, there is no net movement of water.
So, the correct answer is Simple diffusion,

 A cell membrane regulates, which substances can enter and leave the cell based on their size and polarity. Ions cross the cell membrane through which of the following processes? 

bio-chemistry absorption by roots - the processes involved diffusion transport across membrane means of transport

  1. Simple diffusion

  2. Active transport

  3. Endocytosis

  4. Osmosis

  5. Facilitated diffusion

Show answer
Correct Option: E
Explanation:
A. Simple diffusion is the net movement of particles of a substance from a region of greater or higher concentration to a region of lower concentration due to their own intrinsic kinetic energy. In simple words, it is a passive movement of molecules along their concentration gradient.
B. In Active transport, molecules are carried from a region of lower concentration to a region of higher concentration against the concentration gradient with the utilisation of ATP.
C. Endocytosis is a process in which there is engulfing of material by the invagination of cell membrane.
D. Osmosis is the diffusion of water molecules through a semipermeable membrane along the concentration gradient.
E. Facilitated diffusion is the passive movement of molecules along their concentration gradient with the help of membrane proteins known as channel proteins or carrier proteins.
Since ions cross the cell membrane with the help of membrane proteins, it is called facilitated diffusion.
So, the correct answer is 'Facilitated diffusion'.

Type of transport across the biomembrane without the help of proteins is

bio-chemistry absorption by roots - the processes involved diffusion transport across membrane means of transport

  1. Facilitated diffusion

  2. Active transport

  3. Simple diffusion

  4. Diffusion via symport

Show answer
Correct Option: C
Explanation:
  • Simple diffusion can be defined as the process by which solutes particles are moved along the concentration gradient through the semipermeable membrane (cell membrane)
  • Eg- water, oxygen, carbon dioxide, ethanol and urea are transported by simple diffusion.
  • This type of transport does not require energy for the transport of molecules across the cell membrane. 
  • So, the correct answer is 'Simple diffusion'.

Diffusion is more rapid in liquid than in gases.

bio-chemistry absorption by roots - the processes involved diffusion transport across membrane means of transport

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

Diffusion is more rapid in gas as compared to liquid, this is because gases have more kinetic energy and gas molecules are smaller compared to liquid molecules. When the temperature is raised, this results in the increase of kinetic energy of the molecules and rate of diffusion is also increased.

So, the correct answer is option B.

Plasma membrane does not have carrier molecules for

bio-chemistry absorption by roots - the processes involved diffusion transport across membrane means of transport

  1. Active transport

  2. Simple diffusion

  3. Faciliated diffusion

  4. $Na^+-K^+$ pump

Show answer
Correct Option: B
Explanation:

In facilitated diffusion, molecules diffuse across the plasma membrane with assistance from membrane proteins, such as channels and carriers.
For active transport, as the movement is against the concentration gradient, carriers or pumps are required. Similarly with Na-K pump.
Simple diffusion is just the movement of molecules from a place of higher concentration to lower concentration without any carrier molecules.
Thus, the correct answer is option (B). 

Cell wall shows

bio-chemistry absorption by roots - the processes involved diffusion transport across membrane means of transport

  1. Semi permeability

  2. Selective permeability

  3. Complete permeability

  4. Impermeability

Show answer
Correct Option: B
Explanation:

Cell wall is the outer protective layer of a cell. Cellulose is an important constituent of the cell wall. It is made up of carbon, hydrogen and oxygen. It is is selectively permeable, as it allows molecules upto 30-60kD to pass easily without the expenditure of energy and fully permeable to water and proteins molecules.

Differential permeability is a semipermeable membrane which is almost completely impermeable to solute molecules, but is permeable to the solvent.
Complete permeability is a membrane which is almost completely permeable to all the solute and solvent molecules.
Semipermeable membrane allows certain molecules or ions to pass through it by diffusion
So, the correct answer is option ' Selectively permeable'.

The movement of free atoms from higher concentration to lower concentration is called:

bio-chemistry absorption by roots - the processes involved diffusion transport across membrane means of transport

  1. Osmosis

  2. Diffusion

  3. Endosmosis

  4. Exosmosis

Show answer
Correct Option: B
Explanation:

Osmosis is the movement of solvent through a semi-permeable membrane to a region of higher solute concentration.

Diffusion is a process of movement of ions or molecules from a higher concentration to an area of lower concentration.
Endosmosis is the process of movement of solvent from outside to the inside of the cell.
While, exosmosis is the process of movement of solvent from inside to the outside of the cell.
Thus, the correct answer is option (B). 


State whether the following statements are true or false.
Lipid-soluble molecules are able to diffuse into a cell more rapidly than water-soluble molecules.

bio-chemistry absorption by roots - the processes involved diffusion transport across membrane means of transport

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Fat-soluble molecules, such as steroids, alcohols, and some vitamins, can dissolve in the lipid portion of the membrane and diffuse in and out the cell. Water soluble molecules can't pass through the hydrophobic portion of the phospholipid layer.

So, the correct option is 'True'.

Which one of the following process of transporting substances across a membrane does not involve a change in the shape of the transport protein?

bio-chemistry absorption by roots - the processes involved diffusion transport across membrane means of transport

  1. Active transport

  2. $Na^+ - K^+$ pump

  3. Simple diffusion

  4. Facilitated diffusion

Show answer
Correct Option: C
Explanation:

Both active transport and facilitated diffusion are mediated through membrane proteins, here channel proteins allow diffusion of solutes of appropriate size only, so in this size and shape of transport protein changes while simple diffusion does not require proteins for transportation.

 So, the correct option is 'Simple diffusion'.