All Free Biology MCQs with Answers

• A. Carboxylic acids
• B. Carbohydrates
• C. Proteins
• D. Lipids

Explanation: The endoplasmic reticulum (ER) is the site of protein and lipid synthesis and carbohydrate metabolism. It is mainly composed of a high percentage of proteins, with enzymes, cholesterol, triglycerides, and phos­pholipids in lower percentages.Carboxylic acids are absent.

• A. Endoplasmic reticulum
• B. Nucleolus
• C. Nucleus
• D. Ribosomes

Explanation: Prokaryotic cells lack membrane-bound organelles. They do not synthesize proteins in the endoplasmic reticulum. The protein factory in prokaryotic cells are ribosomes found in the cytosol.

• A. Cell wall
• B. Slime
• C. Capsule
• D. Cell membrane

Explanation: Cell envelope includes capsule, slime and cell wall. The bacterial envelope contains a cell wall made up of peptidoglycans and a bilayer cell membrane (double). Capsule is present outside the cell envelope and slime is a part of the capsule.

• A. 2
• B. 3
• C. No similar proteins
• D. 1

Explanation: The ribosomes must start from the start codon in order to begin translating the protein. If they all bind at different points, then they would not be induced into making any similar proteins

• A. Chloroplasts
• B. Mitochondria
• C. Mesosomes
• D. Peroxisomes

Explanation: The main respiratory action occurs in mitochondria, thus mitochondrial matrix and membranes usually enclose respiratory enzymes.

• A. One
• B. Two
• C. Five
• D. Six

Explanation: Mitochondria, the powerhouse of the cell, can be divided into two major compartments: inter-membrane space and matrix. The inter-membranal space is enclosed within the outer and inner membranes and plays an important role in the electron transport chain step of respiration. The matrix, on the other hand, is a viscous gel-like fluid present in the center of mitochondria. It is the site of the citric/ tricarboxylic acid (TCA) cycle.

• A. Cell wall and cell membrane
• B. Cell membrane
• C. Cell wall
• D. Cytoplasm

Explanation: Protoplasts are those cells that have their cell wall removed. The cell wall is removed by the action of digestive enzymes like cellulase and pectinase. Cellulase enzyme breaks down the cellulose in the cell wall whereas pectinase digests pectin. A cell that has its cell wall removed appears spherical in shape. The protoplast consists of the cell's nucleus, cytoplasm and plasma membrane.

• A. Detoxification of harmful drugs.
• B. Synthesis of phospholipids for plasma membrane.
• C. Synthesis of membrane proteins.
• D. Synthesis of steroid hormones from cholesterol.

Explanation: Protein synthesis is a function of the rough endoplasmic reticulum and not of the smooth endoplasmic reticulum.

• A. They are unable to cross the hydrophilic phosphate heads of the lipid bilayer.
• B. They are unable to cross the hydrophobic tails of the lipid bilayer.
• C. They are unable to cross both the phosphate heads and fatty acid chains of the lipid bilayer.
• D. They are too big to cross the plasma membrane.

Explanation: Ions being are hydrophilic in nature and so are repelled by the hydrophobic interior of the plasma membrane which consists of hydrophobic fatty acid chains. This prevents the ions from freely crossing the membrane without any channel or carrier proteins.

• A. Transport of molecules
• B. Mechanical support
• C. Conjugated molecules synthesis
• D. All of these

Explanation: The endoplasmic reticulum allows the transport of material in the cell and the synthesis of conjugated molecules (glycoproteins). The membranes of ER act as an ultrastructural skeletal framework in the cell and provide mechanical support.