Tag: biology

Questions Related to biology

During senescence of a plant.

senescence senescence and death plant growth plant growth and development biology

  1. The plant displays sequential senescence of the leave

  2. Metabolites like carbohydrates, proteins etc. Are transported from young leaves to the aging leaves

  3. Metabolites like carbohydrates, proteins etc. Are transported out of the aging leaves to the young leaves

  4. Secondary plant products accumulate in the tissues are organs during aging

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Correct Option: A

Senescent phase of an organism's life span can be recognised by

senescence senescence and death plant growth plant growth and development biology

  1. Slow metabolism

  2. Cessation of reproduction

  3. Decreased immunity

  4. All of the above

Show answer
Correct Option: D
Explanation:
The terminal irreversible stage of ageing is called senesence. This is the last phase of life span, that ultimately leads to death. This phase can be recognised by slow metabolism, cessation of reproduction and decreased immunity.

So, the correct answer is 'All of the above'.

When a plant undergoes senescence, the nutrients may be ____________.

senescence senescence and death plant growth plant growth and development biology

  1. Accumulated

  2. Bound to cell wall

  3. Translocated

  4. None of these

Show answer
Correct Option: C
Explanation:

When a plant part undergoes senescence, nutrient resources(minerals and carbohydrates) shift away or are translocated from the senescened part to other parts. In leaves at the time of senescene we observe loss of chlorophyll, RNA and protein, transport of nutrients and then abscission.

Senescence in plants leads into .......... of cells.

senescence senescence and death plant growth plant growth and development biology

  1. Increase in size

  2. Increase in number

  3. Death

  4. Differentiation

Show answer
Correct Option: C
Explanation:

Senescence in plants is a process of aging. During process of senescence, cells undergo differentiation. It ultimately leads into the death of cells. 

Thus, the correct answer is option C.

Select the correct option:

Lipids are arranged within the membrane with

biology caskets of life the cell structure cytoplasm unicellular and multicellular organisms number and shape of cells

  1. Polar heads toward inner side and the hydrophobic tails toward outerside

  2. Both heads and tails toward outerside

  3. Heads toward outerside and tail towards inside

  4. Both heads and tails toward innerside

Show answer
Correct Option: C
Explanation:

In lipid bilayer, lipids are arranged with the polar head towards the outer side and the hydrophobic/ non-polar tails towards the inner side.

Select the correct option:

The best material for the study of structure of cell membrane is

biology caskets of life the cell structure cytoplasm unicellular and multicellular organisms number and shape of cells

  1. RBC of human

  2. Liver cell

  3. Kidney cell

  4. Muscle cell

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Correct Option: A
Explanation:

RBCs lack a nucleus and may other cell organelles thus they are best suited to study cell membrane without any complication.

So, the correct answer is 'RBC of human'.

Select the correct option:Who gave the lamellar or sandwich model of cell membrane?

biology caskets of life the cell structure cytoplasm unicellular and multicellular organisms number and shape of cells

  1. Singer and Nicolson

  2. Danielli and Davson

  3. J. Robertson

  4. None of these

Show answer
Correct Option: B
Explanation:

In $1935$, Danielli and Davson proposed that cell membrane is made of a double layer of phospholipid molecules sandwiched between two single layers of proteins. The three layers are held together by electrostatic forces while phospholipid layers are kept adhered by vander Waal's forces.

So, the correct answwer is 'Danielli and Davson'.

Nucleolus contains

biology caskets of life the cell structure cytoplasm unicellular and multicellular organisms number and shape of cells

  1. Genetic instructions

  2. Ribosome assembly line

  3. Protein synthesis machinery

  4. Enzymes for polysaccharide formation

Show answer
Correct Option: B
Explanation:
The nucleolus, whose primary function is to assemble ribosomes is the largest structure in the cell nucleus. The nucleolus takes up around 25% of the volume of the nucleus. It is made up of proteins and ribonucleic acids (RNA). Its main function is to synthesize ribosomal RNA (rRNA) which helps in the synthesis of proteins. It has a ribosome assembly line.
So the correct answer is 'Ribosome assembly line'.

What is true of fluid mosaic model?

biology caskets of life the cell structure cytoplasm unicellular and multicellular organisms number and shape of cells

  1. Phospholipid monolayer is present over protein layer

  2. Phospholipid bilayer is present over protein layer

  3. Protein embedded in phospholipid bilayer

  4. Phospholipid layer is sandwitched between two protein layers.

Show answer
Correct Option: C
Explanation:
  • The fluid mosaic model of the biomembrane or cell membrane was proposed by SJ Singer and GL Nicolson in the year 1972.
  • According to this model, the protein molecules are embedded in the phospholipid bilayer.
  • Thus, the proteins are seen as icebergs in the sea of lipids.
  • The lipid bilayer of the cell membrane provides fluidity, flexibility and elasticity to the membrane. 
  • So, the correct answer is 'Protein embedded in phospholipid bilayer'.

Which of the following show selective permeability?

biology caskets of life the cell structure cytoplasm unicellular and multicellular organisms number and shape of cells

  1. Cell membrane

  2. Cell wall

  3. Cytoplasm

  4. Protoplasm

Show answer
Correct Option: A
Explanation:
  • The cell membrane or plasmalemma is a phospholipid bilayer that are selectively permeable membranes which separate the interior of the cells (cell organelles and cytoplasm) from the outside environment or the extracellular space.
  •  A selectively permeable can be defined as a cell membrane which allows only certain molecules or ions to pass through the membrane by active or passive transport.
  • So, the correct answer is 'Cell membrane'.