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Cell: The Unit of Life · Question 110

AIPMT 2008MCQMedium📈 Topic in 25% papers+4−1
1

Keeping in view the "fluid mosaic model" for the structure of cell membrane, which one of the following statements is correct with respect to the movement of lipids and proteins from one lipid monolayer to the other (described as flip-flop movement)?

  1. Both lipids and proteins can flip-flop
  2. While lipids can rarely flip-flop proteins cannot
  3. While proteins can flip-flop, lipids cannot
  4. neither lipids, nor proteins can flip-flop

Answer

(2) While lipids can rarely flip-flop proteins cannot

Solution

⇒ As per NCERT, the fluid mosaic model (Singer and Nicolson, 1972) states that the quasi-fluid nature of lipid enables lateral movement of proteins within the overall bilayer.

⇒ Transverse (flip-flop) movement from one monolayer to the other requires the polar head of a molecule to pass through the hydrophobic core of the bilayer. Small phospholipid molecules can do this only rarely (slowly, aided by flippases).

⇒ Proteins are large molecules with big hydrophilic regions, so they cannot flip-flop; they move only laterally.

∴ Lipids can rarely flip-flop, proteins cannot.

Answer: (2)

AIPMT 2008

Keep practising — Cell: The Unit of Life

2

Which one of the following is not a constituent of cell membrane?

  1. Glycolipids
  2. Proline
  3. Phospholipids
  4. Cholesterol
AIPMT 2007
3

Select the wrong statement from the following:

  1. The chloroplasts are generally much larger than mitochondria
  2. Both chloroplasts and mitochondria contain DNA
  3. Both chloroplasts and mitochondria contain an inner and an outer membrane
  4. Both chloroplasts and mitochondria have an internal compartment, the thylakoid space bounded by the thylakoid membrane
AIPMT 2007
4

Which of the following statements regarding mitochondrial membrane is not correct ?

  1. The inner membrane is highly convoluted forming a series of infoldings
  2. The outer membrane resembles a sieve
  3. The outer membrane is permeable to all kinds of molecules
  4. The enzymes of the electron transfer chain are embedded in the outer membrane
AIPMT 2006
5

Which of the following statements regarding cilia is not correct ?

  1. Microtubules of cilia are composed of tubulin
  2. The organized beating of cilia is controlled by fluxes of Ca2+ across the membrane
  3. Cilia are hair-like cellular appendages
  4. Cilia contain an outer ring of nine doublet microtubules surrounding two single microtubules
AIPMT 2006
6

A major breakthrough in the studies of cells came with the development of electron microscope. This is because

  1. Electron beam can pass through thick materials, whereas light microscopy requires thin sections
  2. The resolution power of the electron microscope is much higher than that of the light microscope
  3. The electron microscope is more powerful than the light microscope as it uses a beam of electrons which has wavelength much longer than that of photons
  4. The resolving power of the electron microscope is 200-350 nm as compared to 0.1-0.2 nm for the light microscope
AIPMT 2006
7

According to widely accepted "fluid mosaic model" cell membranes are semi-fluid, where lipids and integral proteins can diffuse randomly. In recent years, this model has been modified in several respects. In this regard, which of the following statements is incorrect ?

  1. Proteins in cell membranes can travel within the lipid bilayer
  2. Proteins can also undergo flip-flop movements in the lipid bilayer
  3. Proteins can remain confined within certain domains of the membranes
  4. Many proteins remain completely embedded within the lipid bilayer
AIPMT 2005
8

The main organelle involved in modification and routing of newly synthesized proteins to their destinations is -

  1. Mitochondria
  2. Endoplasmic Reticulum
  3. Chloroplast
  4. Lysosome
AIPMT 2005
9

In chloroplasts, chlorophyll is present in the :-

  1. Outer membrane
  2. Inner membrane
  3. Thylakoids
  4. Stroma
AIPMT 2004
10

Chromosomes in a bacterial cell can be 1–3 in number and

  1. are always circular
  2. are always linear
  3. can be either circular or linear, but never both within the same cell
  4. can be circular as well as linear within the same cell.
AIPMT 2003
11

In bacteria, plasmid is

  1. extra chromosomal material
  2. main DNA
  3. non functional DNA
  4. repetitive gene.
AIPMT 2002

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