Cell: The Unit of Life

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.

In bacteria, plasmid is

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

Ribosomes are produced in:

1. Mitochondria
2. Golgi body
3. Nucleolus
4. Cytoplasm

In fluid mosaic model of plasma membrane

1. Phospholipids form a bimolecular layer in middle part
2. Upper layer is non-polar and hydrophilic
3. Proteins form a middle layer
4. Polar layer is hydrophobic

Difference in gram positive and gram negative bacteria is due to

1. cell wall
2. cell membrane
3. ribosome
4. cytoplasm

Element necessary for the middle lamella is

1. K
2. Cu
3. Ca
4. Zn