Tag: bio-chemistry

Questions Related to bio-chemistry

Which of the following is not true of the carrier molecules involved in facilitated diffusion?

bio-chemistry plant physiology active transport and passive transport types of plant transport atp

  1. They increase the speed of transport across a membrane

  2. They concentrate solute molecules on one side of the membrane

  3. They have specific binding sites for molecules they transport

  4. Transport protein may undergo conformational change upon binding of solutes

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Correct Option: A

Which of the following have no effect at rate of facilitated diffusion?

bio-chemistry plant physiology active transport and passive transport types of plant transport atp

  1. Transport saturation

  2. Presence and absence of membrane protein

  3. Low ATP concentration

  4. Concentration gradient difference

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Correct Option: A
Explanation:

Facilitated diffusion is the movement of water and other substances against the concentration gradient. The movement is through ions channels or membrane proteins which are present on the surface of the membrane. It requires the energy for the movement of substances. The movement is dependent upon the concentration gradient.

So, the correct option is 'Transport saturation'.

Facilitated diffusion

bio-chemistry plant physiology active transport and passive transport types of plant transport atp

  1. Needs a carrier protein

  2. Is an active process

  3. Occurs against the concentration gradient

  4. Needs ATP

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Correct Option: A
Explanation:

Substances having a hydrophilic moiety find it difficult to pass through the membrane. Their movement has to be facilitated. So, facilitated diffusion needs a 'carrier protein'. 

Thus, the correct answer is 'Needs a carrier protein.'

Select the incorrect statement regarding facilitated diffusion.

bio-chemistry plant physiology active transport and passive transport types of plant transport atp

  1. It is a very specific process

  2. It is a passive process

  3. It helps the hydrophilic substances to be transported across the membrane

  4. It is faster than active process

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Correct Option: D

In apoplast pathway, water moves exclusively through the

bio-chemistry plant physiology active transport and passive transport types of plant transport atp

  1. Plasmodesmata

  2. Cell walls

  3. Intercellular spaces

  4. Both B and C

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Correct Option: D
Explanation:
Apoplast pathway consists of non-living parts of plant body i.e., cell walls and intercellular spaces. In apoplast pathway, water passes from root hair to xylem through the walls of intervening cells without crossing any membrane or cytoplasm. The pathway provides the least resistance to movement of water. However, it is interrupted by the presence of impermeable lingo-suberin casparian strips in the walls of endodermal cells.
So, the correct answer is 'Both B and C'.

When transport proteins simultaneously move two molecules across a membrane in the same direction, the process is called

bio-chemistry plant physiology active transport and passive transport types of plant transport atp

  1. Uniport

  2. Antiport

  3. Symport

  4. Diffusive port

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Correct Option: C
Explanation:
Some carrier proteins allow transport only if two types of molecules move together. This is called cotransport. It is of two types: symport and antiport method. In symport method of cotransport, both molecules cross the membrane in the same direction at the same time. In antiport method of cotransport, both molecules move in opposite direction. When a molecule move across a membrane independent of other molecule, the process is called uniport.
So, the correct answer is 'Symport'.

The type of diffusion in which substance move across the membrane along their concentration gradient in the presence of certain or transport proteins is called as 

bio-chemistry plant physiology active transport and passive transport types of plant transport atp

  1. Simple diffusion

  2. Facilitated diffusion

  3. Osmosis

  4. Active transport

Show answer
Correct Option: B
Explanation:
The diffusion of hydrophilic substances along the concentration gradient through fixed membrane transport proteins without involving energy expenditure, is called facilitated diffusion. Facilitated diffusion is very specific as it allows cell to select substances for uptake. It is sensitive to inhibitors as well as show saturation effect. Two major types of transport proteins are known viz, carrier proteins(also called carriers, transporters) and channel proteins. Carrier proteins bind the particular solute to be transported and deliver the same to the other side of the membrane.
So, the correct answer is 'Facilitated diffusion'.

Which of the below mentioned properties is not true with respect to facilitated transport?

bio-chemistry plant physiology active transport and passive transport types of plant transport atp

  1. Requires special membrane proteins

  2. Transport saturates

  3. Uphill transport

  4. Highly selective

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Correct Option: C
Explanation:
Active transport is also known as uphill transport that requires the transport of molecules from a low-concentration region to a high-concentration region.  whereas facilitated transport is the passive transport of molecules or ions across a biological membrane via specific transmembrane integral proteins.
So the correct answer is 'Uphill transport'.

When a molecule moves across a membrane independent of other molecules, the process is called (i) Uniport (ii) Symport (iii) Antiport?

bio-chemistry cell membrane active transport and passive transport types of plant transport atp

  1. i

  2. i and ii

  3. i and iii

  4. ii and iii

  5. iii

Show answer
Correct Option: A
Explanation:

When a molecule moves across a membrane independent of other molecule, it is called uniport.

When two molecules move simultaneously across the membrane in the same direction, it is called symport.
When two molecules move in opposite direction to each other across the membrane, it is called antiport. Thus, the correct answer is A.

When a molecule moves across a membrane independent of other molecules, the process is called

bio-chemistry cell membrane active transport and passive transport types of plant transport atp

  1. Uniport

  2. Symport

  3. Antiport

  4. None of these

Show answer
Correct Option: D
Explanation:

A uniporter is an integral membrane protein that transports a single type of substrate species (charged or uncharged) across a cell membrane. It may use either facilitated diffusion and transport along a diffusion gradient or transport against one with an active transport process. They can be either ion channels or carrier proteins. In facilitated diffusion, molecules diffuse across the plasma membrane with assistance from membrane proteins, such as channels and carriers.

So the correct option is 'None of the above'