All Free Biology MCQs with Answers

4051. Due to slight difference in their _, the chlorophyll a and chlorophyll b show slightly different _.

• A. Structure, Absorption spectra
• B. Structure, Molecular formula
• C. Absorption spectra, Structure
• D. Absorption spectra, Molecular formula

Explanation: Option A is correct.Due to a slightly different chemical structure, the chlorophyll a and chlorophyll b show slightly different absorption spectra. The main difference between chlorophyll a and chlorophyll b is the presence of a 3-methyl group on the porphyrin ring in chlorophyll b. This 3-methyl group absorbs light in the blue-green region of the spectrum, which is why chlorophyll b appears blue-green. In chlorophyll a, the 3-methyl group is replaced with a formyl group. This formyl group absorbs light in the red region of the spectrum, which is why chlorophyll a appears red. The different chemical structures of chlorophyll a and chlorophyll b result in slightly different absorption spectra. Chlorophyll a absorbs more blue-green light than chlorophyll b, while chlorophyll b absorbs more red light than chlorophyll a. This means that they absorb slightly different wavelengths of light.The slightly different absorption spectra of chlorophyll a and chlorophyll b allow them to work together to absorb a wider range of wavelengths of light. This is essential for the efficient conversion of light energy into chemical energy.

4052. Difference in structure of different pigments:

• A. Increase the range of light wavelengths being absorbed
• B. Decrease the range of light wavelengths being absorbed
• C. Have no effect on range of light wavelengths being absorbed
• D. Have no effects on the color of pigment

Explanation: Option A is correct.Yes, the difference in structure of different pigments can increase the range of light wavelengths being absorbed. This is because different pigments have different absorption spectra, meaning that they absorb different wavelengths of light. For example, chlorophyll a absorbs light in the blue-green and red regions of the spectrum, while chlorophyll b absorbs light in the blue-green, yellow, and red regions of the spectrum. This means that chlorophyll a and chlorophyll b can absorb a wider range of wavelengths of light than either pigment could on its own. Other pigments, such as carotenoids and phycobilins, also have different absorption spectra. This allows plants to absorb a wider range of wavelengths of light, which is essential for the efficient conversion of light energy into chemical energy.

4053. Pick up the one(s) called as accessory pigments:

• A. Carotenes
• B. Chlorophylls
• C. Xanthophylls
• D. All of these

Explanation: Yes, carotenoids,xanthophylls and chlorophylls are accessory pigments. Accessory pigments are pigments that are not directly involved in the light-dependent reactions of photosynthesis, but they help to absorb light energy and transfer it to chlorophyll a, which is the primary pigment involved in photosynthesis. Carotenoids are yellow, orange, and red pigments that are found in plants, algae, and some bacteria. They absorb light energy in the blue and violet regions of the spectrum, which chlorophyll a does not absorb as well. This allows carotenoids to broaden the range of wavelengths that can be used for photosynthesis.Xanthophylls are yellow and orange pigments that are also found in plants, algae, and some bacteria. They absorb light energy in the blue-green and yellow-orange regions of the spectrum. This allows xanthophylls to absorb light that chlorophyll a and carotenoids cannot absorb, which helps to extend the range of wavelengths that can be used for photosynthesis. Chlorophylls are accessory pigments. Accessory pigments are pigments that help to absorb light energy and transfer it to chlorophyll a, which is the primary pigment involved in photosynthesis. Chlorophyll a is the most abundant pigment in plants and algae. It absorbs light in the blue-green and red regions of the spectrum. However, it cannot absorb all of the light that is available in the environment. This is where accessory pigments come in.

4054. Absorption spectrum for chlorophyll indicates that absorption is maximum in:

• A. Blue part of spectrum
• B. Red part of spectrum
• C. Blue and Red parts of spectrum
• D. White and red part of spectrum

Explanation: Option C is correct.The absorption spectrum for chlorophyll indicates that absorption is maximum in the blue and red parts of the spectrum. Chlorophyll is a green pigment that is found in plants and algae. It is responsible for absorbing light energy and using it to produce food. The absorption spectrum of chlorophyll shows that it absorbs light most strongly in the blue and red regions of the spectrum. This is because the chlorophyll molecule has a structure that allows it to absorb light in these wavelengths. The blue region of the spectrum corresponds to wavelengths of light that are about 400-500 nanometers (nm). The red region of the spectrum corresponds to wavelengths of light that are about 600-700 nm. The absorption of light in the blue and red regions of the spectrum is important for photosynthesis. This is because these wavelengths of light provide the energy that is needed to split water molecules into hydrogen and oxygen. The hydrogen is then used to produce ATP, a molecule that stores energy. The oxygen is released as a byproduct. So, the absorption spectrum for chlorophyll shows that it is most effective at absorbing light in the blue and red regions of the spectrum. This is important for photosynthesis, as it is the energy from these wavelengths of light that is used to split water molecules and produce ATP.

4055. An absorption spectrum of chlorophylls have:

• A. Two peaks
• B. Two peaks, one valley
• C. Two valleys
• D. One peaks, two valleys

Explanation: Option B is correct.An absorption spectrum of chlorophylls has two peaks and one valley. The peaks are located at wavelengths of 430-470 nm (blue-green) and 660-670 nm (red). The valley is located at a wavelength of 520-530 nm (green). The peaks in the absorption spectrum of chlorophylls correspond to the wavelengths of light that are absorbed most strongly by chlorophyll. The valley corresponds to the wavelength of light that is absorbed least strongly by chlorophyll. The absorption spectrum of chlorophyll is important because it shows the wavelengths of light that are most useful for photosynthesis. The blue-green and red parts of the spectrum correspond to the wavelengths of light that are most useful for photosynthesis, so chlorophyll is able to absorb these wavelengths of light very well.

4056. Pick up the one having broadest valley:

• A. Absorption spectrum of chlorophyll a
• B. Absorption spectrum of carotenoids
• C. Absorption spectrum of chlorophyll b
• D. All have broadest peaks

Explanation: Option D is correct.The absorption spectrum of chlorophyll a has two peaks and one valley. The peaks are located at wavelengths of 430-470 nm (blue-green) and 660-670 nm (red). The valley is located at a wavelength of 520-530 nm (green). The valley in the absorption spectrum of chlorophyll a is the broadest. This means that chlorophyll a absorbs light least strongly in the green region of the spectrum. This is why plants appear green, because the green light is reflected rather than absorbed. The broadness of the valley in the absorption spectrum of chlorophyll a is due to the structure of the chlorophyll molecule. The chlorophyll molecule has a porphyrin ring, which is a large molecule that is made up of four pyrrole rings that are linked together. The porphyrin ring is hydrophobic, which means that it does not mix well with water. The magnesium atom in the center of the porphyrin ring also makes chlorophylls hydrophobic.The carotenoids with the broadest valley in its absorption spectrum is lutein. Lutein has a valley in its absorption spectrum at a wavelength of 520-530 nm (green). This is the same wavelength that chlorophyll has a peak in its absorption spectrum. The broadness of the valley in lutein's absorption spectrum means that it absorbs light in a wide range of wavelengths around 520-530 nm. This allows lutein to absorb light that chlorophyll does not absorb as well, which helps to extend the range of wavelengths that can be used for photosynthesis. The absorption spectrum of chlorophyll b has the broadest valley. This valley is located at a wavelength of 520-530 nm (green). The broad valley in the absorption spectrum of chlorophyll b is due to the fact that chlorophyll b absorbs light less strongly in the green part of the spectrum than it does in the blue-green and red parts of the spectrum. This is why plants appear green, because the green light is reflected rather than absorbed.

4057. The absorptive peaks in the absorption spectrum of chlorophyll b are at the wave length of:

• A. 430 - 670 nm
• B. 440 - 480 nm
• C. 460 - 640 nm
• D. 420 - 610 nm

Explanation: Option B is correct.The absorptive peaks in the absorption spectrum of chlorophyll b are almost at the wavelength of 450-475 nm. Chlorophyll b is a pigment that is found in plants and algae. It is similar to chlorophyll a, but it has a slightly different absorption spectrum. The absorption spectrum of chlorophyll b shows that it absorbs light most strongly in the blue-green and far-red parts of the spectrum. The peak absorption wavelength of chlorophyll b is 450-475 nm, which is in the blue-green region of the spectrum. This means that chlorophyll b absorbs light most strongly in this region of the spectrum.

4058. The reactions of photosynthesis consists of:

• A. Two phases
• B. Four phases
• C. Three phases
• D. Many phases

Explanation: Option A is correct.The reactions of photosynthesis consist of two phases, the light-dependent reactions and the Calvin cycle.Light-dependent reactions take place in the thylakoid membranes of chloroplasts. They use light energy to split water molecules into oxygen and hydrogen ions. The hydrogen ions are then used to produce ATP, a molecule that stores energy.Calvin cycle takes place in the stroma of chloroplasts. It uses ATP and NADPH, the energy molecules produced in the light-dependent reactions, to fix carbon dioxide into glucose

4059. In photosynthesis, reducing power and assimilatory power is synthesized during:

• A. Dark reaction
• B. Light reaction
• C. Calvin cycle
• D. Oxidation phosphorylation

Explanation: Option B is correct.The reducing power and assimilatory power are synthesized during the light-dependent reactions of photosynthesis. These reactions take place in the thylakoid membranes of chloroplasts. They use light energy to split water molecules into oxygen and hydrogen ions. The hydrogen ions are then used to produce ATP, a molecule that stores energy. NADPH is also produced during the light-dependent reactions. NADPH is a molecule that carries electrons, and it is used as a reducing agent in the Calvin cycle.Reducing power is a term used to describe the ability of a molecule to donate electrons. In photosynthesis, reducing power is provided by NADPH, which is produced in the light-dependent reactions. NADPH is used by the Calvin cycle to fix carbon dioxide into glucose.Assimilative power is a term used to describe the ability of a molecule to store energy. In photosynthesis, assimilatory power is provided by ATP, which is also produced in the light-dependent reactions. ATP is used by the Calvin cycle to drive the reactions that fix carbon dioxide into glucose.

4060. For synthesis of sugar by reducing CO2, NADPH2 provides:

• A. Enzymes
• B. Co-enzymes
• C. Energized electrons
• D. Both B and C

Explanation: Option B and C are correct.NADPH provides energized electrons for the synthesis of sugar by reducing CO2. NADPH is a molecule that is produced in the light-dependent reactions of photosynthesis. It is a carrier of high-energy electrons, which are used by the Calvin cycle to reduce carbon dioxide into glucose.The Calvin cycle is a series of reactions that take place in the stroma of chloroplasts. It is the second phase of photosynthesis, and it is where sugar is produced. The Calvin cycle uses ATP and NADPH, the energy molecules produced in the light-dependent reactions, to fix carbon dioxide into glucose.The electrons from NADPH are used to reduce carbon dioxide, which means that they are donated to carbon dioxide. This reduces carbon dioxide to a form that can be used to build sugar. The electrons from NADPH are also used to power the reactions of the Calvin cycle. NADPH2 provides co-enzymes for sugar synthesis. Co-enzymes are molecules that help enzymes function. NADPH2 is a coenzyme that provides electrons for the reduction of carbon dioxide. The reduction of carbon dioxide is the process of adding electrons to carbon dioxide, which eventually forms glucose.In photosynthesis, NADPH2 is produced in the light-dependent reactions. It is then used by the Calvin cycle to reduce carbon dioxide into glucose. The Calvin cycle is a series of reactions that take place in the stroma of chloroplasts. It is the second stage of photosynthesis, and it is where glucose is actually produced.