All Free Biology MCQs with Answers

1441. Which of the following carbohydrate is tasteless___________?

• A. Monosaccharide
• B. Oligosaccharide
• C. Polysaccharide
• D. None of these

Explanation: Polysaccharides such as starch and cellulose are generally tasteless because their large molecules do not stimulate sweet taste receptors like many simple sugars do. Students may choose monosaccharides, but glucose and fructose are examples of sweet monosaccharides.

1442. Heart beats about ________ times in one's life.

• A. 2.8 Billion
• B. 3.7 Billion
• C. 4.2 Billion
• D. Infinite

Explanation: A typical estimate is about 70 beats/minute x 60 minutes/hour x 24 hours/day x 365 days/year x 70 years = 2,574,720,000 beats, or about 2.6 billion beats. Since estimates vary with heart rate and lifespan, 2.8 billion is the closest listed value; students may choose 3.7 billion by using an unnecessarily high lifetime estimate.

1443. A single heart beat involves ________ stages.

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: One cardiac cycle has three main stages: atrial systole, ventricular systole, and joint diastole. Students may choose two by counting only the two systolic stages and overlooking the diastolic stage in which all chambers relax.

1444. A decrease in the rate of beating of heart is called__________?

• A. Bradycardia
• B. Tachycardia
• C. Braditachycardia
• D. Non of these

Explanation: Bradycardia means an abnormally slow heart rate, commonly defined in adults as fewer than 60 beats per minute at rest. Students may choose tachycardia because it is another term ending in “cardia,” but tachycardia means an increased, not decreased, rate.

1445. An increase in the heart rate is termed as:_________?

• A. Bradycardia
• B. Tachycardia
• C. Trachybradycardia
• D. Non of these

Explanation: Tachycardia is an abnormally rapid heart rate, often described in adults as more than 100 beats per minute at rest. Students may choose bradycardia because both terms describe heart-rate changes, but bradycardia refers to a slow rate.

1446. "lub" sound is produced after _________ ?

• A. The ventricles are fully contracted
• B. The ventricles start to relax
• C. The bicuspid and tricuspid valves suddenly close
• D. The semilunar valves are closed

Explanation: The “lub” sound is produced when the atrioventricular valves, the bicuspid and tricuspid valves, suddenly close at the beginning of ventricular systole. Students often choose d because the semilunar valves also close during the cardiac cycle, but their closure produces the “dub” sound.

1447. QRS complex represents____________?

• A. Atrial systole
• B. Ventricular systole
• C. Atrial diastole
• D. Ventricular diastole

Explanation: The QRS complex records ventricular depolarisation, which initiates ventricular contraction or ventricular systole. Students may choose atrial systole because it is also a contraction phase, but atrial depolarisation is represented mainly by the P wave.

1448. "lubb" sound is produced due to___________________?

• A. Opening of inlet valve
• B. Closure of inlet valve
• C. Opening of outlet valve
• D. Closure of outlet valve

Explanation: The lubb sound occurs when the atrioventricular, or inlet, valves close at the beginning of ventricular systole. Their closure prevents backflow into the atria, whereas closure of the outlet valves produces the dubb sound, making d the likely error.

1449. The mechanism for ATP synthesis is_____________?

• A. Chemosynthesis
• B. Photosynthesis
• C. Phosphorylation
• D. Chemiosmosis

Explanation: Chemiosmosis synthesizes ATP by using the flow of protons through ATP synthase down their electrochemical gradient, which drives phosphorylation of ADP. Photosynthesis and chemosynthesis are energy-producing pathways, not the specific mechanism of ATP formation. Students may choose phosphorylation because ATP is formed by adding phosphate, but phosphorylation describes the chemical step rather than the proton-driven mechanism.

1450. Biologist 'Grass' discovered the life cycle of plasmodium in_______?

• A. 1896
• B. 1897
• C. 1898
• D. 1899

Explanation: Giovanni Battista Grassi's work helped establish that malaria parasites develop in and are transmitted by mosquitoes, with the key discovery dated to 1898. Students may choose 1897 because important malaria transmission observations occurred around that period, but the standard date for Grassi's life-cycle discovery is 1898.