Cell: The Unit of Life

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

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

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

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

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

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

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

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

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

In chloroplasts, chlorophyll is present in the :-

1. Outer membrane
2. Inner membrane
3. Thylakoids
4. Stroma

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.