Pakistan MCQs

The plasma membrane is selectively permeable.
It regulates exchange between the cell and its environment.

Phospholipids form a bilayer with hydrophilic heads and hydrophobic tails.
Proteins and other molecules are embedded within it.

Membrane components can move laterally within the bilayer.
The membrane is flexible rather than rigid.

The nucleus stores chromosomes in eukaryotic cells.
It also regulates gene expression and cell activities.

The nucleolus is a dense region inside the nucleus.
It produces rRNA and assembles ribosomal subunits.

Ribosomes translate mRNA into polypeptide chains.
They occur freely in cytoplasm or attached to rough ER.

Rough ER has ribosomes attached to its surface.
It folds and modifies proteins entering the endomembrane system.

Smooth ER lacks ribosomes.
It synthesizes lipids and helps detoxify chemicals.

The Golgi receives materials from the ER.
It modifies and directs them to their destinations.

Lysosomes break down macromolecules and damaged cell parts.
Their enzymes work best in an acidic environment.

Mitochondria convert energy from nutrients into ATP.
They contain their own DNA and ribosomes.

Chloroplasts contain chlorophyll and photosynthetic membranes.
They convert light energy into chemical energy.