All Free Biology MCQs with Answers

1041. Glycoproteins are formed as a result of the combination of:

• A. Lipids and proteins
• B. Carbohydrates and proteins
• C. Nucleic acid and proteins
• D. Fatty acids and carbohydrates

Explanation: The prefix glyco means sugar, so a glycoprotein is protein joined to a carbohydrate group, and such molecules coat the cell surface where they act in recognition and as receptors. Lipid with protein gives a lipoprotein and nucleic acid with protein a nucleoprotein, both of which are conjugated molecules of other kinds. Reading the prefix identifies the non protein partner every time.

1042. A student observed a boundary in both plant and animal cells that controls entry and exit of substances. Which of the following structures is likely being observed?

• A. Mitochondria
• B. Golgi apparatus
• C. Plasma membrane
• D. Cell wall

Explanation: The plasma membrane is present in every cell and is partially permeable, so it decides what enters and leaves, which is exactly the function described. The cell wall is the trap: it is a boundary too, but it occurs only in plants and is fully permeable, so it controls nothing. The words both plant and animal are what rule it out.

1043. If a normal person marries with colour blind female what will be the possibility of normal male child:

• A. 0%
• B. 25%
• C. 50%
• D. 75%

Explanation: A colour blind mother carries the defective allele on both her X chromosomes, and a son receives his only X from her, so every son must be colour blind. The daughters each receive a normal X from the father and are carriers with normal vision. This is the clearest illustration of why an X linked recessive trait passes from mother to son.

1044. Which of the following characters is shared by both skeletal and cardiac muscles?

• A. Presence of striation
• B. Involuntary control
• C. Multinucleated fibers
• D. Intercalated discs

Explanation: Both use the same regular arrangement of actin and myosin filaments, so both show cross striations under the microscope. They differ in control, skeletal being voluntary and cardiac involuntary, and intercalated discs and branching belong to cardiac muscle alone. Multinucleated fibres are a skeletal muscle feature.

1045. Which of the following muscle types are involuntary in action?

• A. Skeletal and smooth
• B. Skeletal and cardiac
• C. Cardiac and smooth
• D. Smooth muscle only

Explanation: Cardiac muscle beats rhythmically without conscious control and smooth muscle works the gut, blood vessels and other hollow organs automatically, so both are involuntary. Skeletal muscle is the only voluntary type, which eliminates the first two options at once. Smooth muscle alone is too narrow, since it leaves cardiac muscle out.

1046. In which of the following combinations, both components have non-striated muscle fibers?

• A. Intestine & biceps
• B. Intestine & blood vessels
• C. Heart & lungs
• D. Stomach & heart

Explanation: The walls of the intestine and of blood vessels both contain smooth muscle, which has no striations and works involuntarily. The biceps is skeletal muscle and the heart is cardiac, and both of those are striated, so any pairing including them fails. Recognising which organ contains which muscle type is the whole of this question.

1047. Numerous opportunistic diseases might attack a person suffering from which of the following diseases:

• A. Measles
• B. Influenza
• C. Hepatitis A
• D. AIDS

Explanation: AIDS destroys or severely weakens CD4 helper T cells, reducing immune coordination and allowing opportunistic infections to develop. Students may choose measles because it can temporarily suppress immunity, but the extensive opportunistic disease pattern is characteristic of AIDS. Therefore, option d is correct.

1048. The major cell infected by the HIV is lymphocyte ?

• A. helper-T
• B. B
• C. both T and B
• D. none of these

Explanation: HIV mainly infects helper T lymphocytes because the virus attaches to the CD4 receptor on these cells, gradually weakening specific immunity. The likely alternative is B lymphocytes, due to their role in antibody production, but HIV’s principal target is the CD4-positive helper T cell.

1049. AIDS is caused by ________ virus?

• A. HAV
• B. HIV
• C. Rabies
• D. Pigs

Explanation: AIDS is caused by human immunodeficiency virus, or HIV, which progressively damages immune cells, especially CD4 T lymphocytes. Students may choose HAV because it is also a viral abbreviation, but HAV causes hepatitis A rather than AIDS.

1050. HIV is a ________ virus?

• A. SsRNA
• B. DsRNA
• C. SsDNA
• D. DsDNA

Explanation: HIV is an enveloped single-stranded RNA virus and is a retrovirus because it uses reverse transcriptase to make DNA from its RNA genome. Students may choose ssDNA by focusing on the presence of a DNA stage, but the viral genome entering the host cell is single-stranded RNA.