Biology · Science General

Cell Biology and Structure

3,221 Questions

Cell biology focuses on the structure and function of cellular organelles. Key topics include cellular respiration, DNA inheritance, and energy production. These fundamental biology concepts are crucial for medical entrance and state service examinations.

Cell organelles functionsCellular respiration sitesDNA and ribosomesAnimal cell structurePlant cell components

Cell Biology and Structure Questions

Multiple choice

Which of the following statements is/are false? a. Different organisms have same number of cells in their bodies. b. The cells in a multicellular organism have many different shapes. c. The cells in a multicellular organism can have many different sizes.

  1. Only a

  2. Only a and b

  3. Only b

  4. Only b and c

  5. Only c
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Statement 'a' is  false. Thus, it is the correct option. Different organisms have different number of cells in their bodies.

Multiple choice

Match the following:

 
Bodies Functions in an animal cell
a, Mitochondria 1. To hold air, water and particles of food.
b. Vacuole 2. To carry out all the activities of the life processes.
c. Cytoplasm 3. To carry out respiration for releasing energy from food.

  1. a - 3, b - 1, c - 2

  2. a - 3, b - 2, c - 1

  3. a - 1, b - 3, c - 2

  4. a - 1, b - 2, c - 3

  5. a - 2, b - 1, c - 3
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is the correct option. The function of mitochondria in an animal cell is to carry out respiration, and  releasing energy from food. The function of  a vacuole in an animal cell is to hold air, water and particles of food. The function of  the cytoplasm in an animal cell is to carry out all the activities.

Multiple choice

What activates protein kinase A?

  1. ATP

  2. GDP

  3. GTP

  4. Cyclic AMP

  5. RGS proteins
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The activation of protein kinase A depends on the cyclic AMP and therefore, it is commonly known as cAMP-dependent protein kinase. The role of protein kinase A is to transfer phosphate from ATP to serine or threonine residues of various proteins in order to alter their activities.

Multiple choice

In a G protein mediated signal transduction cascade of cAMP, adenylase cyclase is activated by

  1. G-alpha GDP complex with G-beta, Gama subunits

  2. G-beta GDP Complex

  3. G-alpha-beta GDP complex

  4. G-beta-gama GDP complex

  5. G-alpha GTP complex
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

GTP in addition to the G protein is essential for the signal transduction to proceed. G-alpha is the activated subunit of G-protein. The binding of a ligand like epinephrine causes conformational change in the G-protein that assist in making the nucleotide binding site of the G-protein more accessible to the cytosol where the concentration of GTP is high. The alpha unit of it releases the GDP and binds to GTP. In other words, GTP is exchanged for the GDP. The binding of GTP causes additional conformational change in G alpha subunit and then G-protein disassociates to leave beta and Gama units. G alpha-GTP complex then binds to adenylate cyclase and activates it.

Multiple choice

The signal termination of the signal transduction by the 7TM receptor becomes impossible if

  1. intrinsic GTPase activity of the G-protein becomes defective

  2. adnylate cyclase fails to bind to the G-alpha stimulatory subunit of G-protein

  3. the concentration of GTP is more in the cytosol

  4. G-alpha fails to reassociate with the G-beta, Gama subunits

  5. both Beta-adrenergic receptor kinase and Beta arrestin becomes defective
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The important step in the termination process is the resetting of the hormone-bound activated receptor. This is achieved by two processes. The first step marks the removal of hormone, and the receptor goes back to the inactivated state. The next step involves the phosphorylation of the serine and threonine residues in the carboxyl-terminal of the hormone-receptor complex by the receptor kinases. The final step includes the binding of B-arrestin to the phosphorylated receptor. This finally reduces the G-protein-activating ability of the receptor completely. Thus, the continuous activation of the G-protein is prevented by the phosphorylation and binding of B-arrestin that desensitize the receptor after continuous exposure to epinephrine hormone. This marks the termination of the cascade. However, if beta-adrenergic receptor kinase and Beta arrestin becomes defective, the signal termination of the signal transduction by the 7TM receptor becomes impossible.

Multiple choice

Which cell organelle contains cristae?

  1. Nucleus

  2. Chloroplast

  3. Ribosomes

  4. Mitochondria
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Each of the partial partitions in a mitochondrion formed by infolding of the inner membrane are called cristae.

Multiple choice

Identify the false statement(s).

  1. Regulation of cell cycle progression depends on cyclin dependent kinase (CDK) and protease activity.
  2. Photorespiratory reaction occurring in oxidative photosynthetic carbon (C2) pathway involves a cooperative interaction among three organelles: chloroplast, peroxisome and mitochondria.
  3. Cytokinins acts as a promoter of senescence and ethylene act as a senescence antagonist.

  1. Only 1

  2. Only 2

  3. Only 3

  4. Both 1 and 2

  5. Both 2 and 3
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Correct answer. Ethylene acts as a promoter of senescence and cytokinins act as a senescence antagonist.