All Free Biology MCQs with Answers

3981. In the second step of glycolysis, two hydrogen atoms are removed from a molecule of glucose-3-phosphoglycerate(G3P) and transferred to a molecule of NAD. What is the name of this step?

• A. Preparatory phase
• B. Lactic acid fermentation
• C. Payoff phase
• D. Carbon fixation

Explanation: A. This is the first step of glycolysis.B. In absence of oxygen, pyruvic acid is converted into lactic acid. This happens after glycolysis, when pyruvic acid is formed.D. Refers to the initial incorporation of carbon dioxide into organic molecule Rubp in Calvin cycle.

3982. Breaking of the terminal phosphate of ATP releases about _ Kcal of energy.

• A. 6.1
• B. 6.3
• C. 7.1
• D. 7.3

Explanation: Breaking of the terminal phosphate of ATP releases about 7.3 Kcal of energy.

3983. Spectrophotometer is used to measure:

• A. Absorption of CO2
• B. Absorption of O2
• C. Reflection of pigments
• D. Absorption of different wavelengths

Explanation: Spectrophotometer is a device that is designed to measure the absorption of different wavelength of light by substance across a range of wavelengths. By analysing the absorption pattern scientist can gain insight into the chemical composition, concentration or other properties of the sample.

3984. Which shows the effectiveness of wavelengths of light driving photosynthesis?

• A. Absorption spectrum
• B. Action spectrum
• C. Broad spectrum
• D. Narrow spectrum

Explanation: The graph showing relative effectiveness of different wavelengths of light in driving photosynthesis is called action spectrum. It was reported by T. W Engelmann.The action spectrum is a graph that is used to determine the effectiveness of different wavelength of light in driving a specific biological or chemical processes such as photosynthesis. It helps identify the wavelength of light that have the greatest impact on the activity or response being studied.

3985. Wavelength of blue light that is absorbed maximum by pigments:

• A. 670 nm
• B. 540 nm
• C. 430 nm
• D. 750 nm

Explanation: Wavelength of visible light varies from 380 nm to 750 nm. This spectrum contains seven different colors. Out of them blue and red wavelengths are absorbed maximally. 430 nm and 670 nm are most effective and they represent blue and red color respectively.

3986. Which of the following groups does not use water as proton donor?

• A. Cyanobacteria
• B. Purple sulphur bacteria
• C. Plants
• D. Algae

Explanation: purple sulphur bacteria use hydrogen sulphide as proton donor. Rest of organisms use water as proton donor for photosynthesis. purple sulphur bacteria use hydrogen sulphide as proton donor. Rest of organisms use water as proton donor for photosynthesis.

3987. Magnesium is central part of:

• A. Porphyrin ring
• B. Phytol tail
• C. Pyrrole ring
• D. Hydrophobic part

Explanation: In porphyrin rings, the central atom is typically a metal ion, and one common metal ion found in porphyrin rings is magnesium (Mg).Explanation is given below.In porphyrin rings, the central atom is typically a metal ion, and one common metal ion found in porphyrin rings is magnesium (Mg).tral atom is typically a metal ion, and one common metal ion found in porphyrin rings is magnesium (Mg).The porphyrin ring structure consists of four pyrrole units connected together by methine bridges. The central magnesium ion coordinates with the four nitrogen atoms present in the pyrrole rings, forming coordination bonds. This coordination complex is often referred to as a metalloporphyrin.The porphyrin ring structure consists of four pyrrole units connected together by methine bridges. The central magnesium ion coordinates with the four nitrogen atoms present in the pyrrole rings, forming coordination bonds. This coordination complex is often referred to as a metalloporphyrin.

3988. Following is correct sequence of energy transfer between photosynthetic pigments:

• A. Chl.a→Chl.b→Carotenoids
• B. Carotenoids→Chl.b→Chl.a
• C. Chl.b→Carotenoids→Chl.a
• D. In any direction

Explanation: Carotenoids and chloroph II 'b' are called accessory pigments because they absorb light and transfer the energy to chlorophyll a, which then initiates the light reactions. It is generally believed that the order of tranfer of energy is.

3989. Location of phytol tail of chlorophyll b is:

• A. Stroma
• B. Thylakoid membrane
• C. Thylakoid surface
• D. Thylakoid lumen

Explanation: Chlorophyll molecule has a long hydrocarbons tail which is attached to one of the pyrrole rings of chlorophyll molecules and is embedded in the hydrophobic core of thylakoid membrane.

3990. Which one of the following is not of carotenoids?

• A. Convert light energy into chemical energy
• B. Protect chlorophyll
• C. Transfer energy
• D. Protect human eye

Explanation: Transfer of energy, broadening the spectrum, protection of chlorophyll molecules and eyes are the functions of carotcnoids. The conversion of light energy into chemical energy is the function of chlorophyll molecules. In chloroplasts, the responsibility of converting light energy into chemical energy lies with the photosystems. The photosystems are protein complexes embedded in the thylakoid membrane of the chloroplasts.