BIOLOGY 2 Marks Questions

ATP, NADPH and oxygen are the products of light reaction. ATP and NADPH are used in the reduction step of biosynthetic phase of photosynthesis. Oxygen is liberated into the atmosphere.

ATP, NADPH and oxygen are the products of light reaction:

• ATP and NADPH are used in the reduction step of biosynthetic phase of photosynthesis.
• Oxygen is liberated into the atmosphere.

Four basic requirements are as follows:

1. A unit membrane.
2. A proton pump.
3. A proton gradient.
4. ATP synthase enzym.

• Englemann used a prism to split light into its spectral components.
• He illuminated the green alga, Cladophora, kept in a suspension of aerobic bacteria; these bacteria were used to detect the sites of oxygen production.
• When photosynthesis was carried out under this set up, it was found that the bacteria accumulated in the blue and red regions of the split light spectrum.
• He plotted the graph, called action spectrum.

Dark reactions are dependent on light but not directly. Rather it is dependent on products of light reactions, which are ATP and NADPH. Since facilitation of dark reactions does not need light so they are called dark reactions.

Differences between stroma and grana of chloroplasts are:

S.No.	Stoma	Grana
(i)	It is the jelly-like matrix of the chloroplast.	These are formed of stacks of thylakoids.
(ii)	Dark reaction takes place here.	Light reaction takes place here.

Accessory pigments are those pigments, which assist in photosynthesis by capturing energy from light of different wavelengths, e.g., chlorophyll b, Xanthophylls and carotenoids. Role in Photosynthesis:

1. They absorb wavelength of light not absorbed by chlorophyll and transfer the energy to chlorophyll.
2. They also protect chlorophyll a from photo-oxidation.

It is a wasteful process because:

1. There is no synthesis of sugars or other energy rich compounds like ATP.
2. It consumes ATP and liberates the photosynthetically fixed carbon dioxide.

1. A membrane.
2. A proton pump.
3. A proton gradient.
4. ATP synthetase.

Cyonobacteria and some other photosynthetic bacteria have thylakoids suspended freely in the cytoplasm (i.e., they are not enclosed in membrane) and also have bacteriochlorophyll to conduct photosynthesis.

1. 3 molecules of ATP and 2 molecules of NADPH.
2. In the stroma of chloroplast.

In tropical rain forests, the canopy is thick and shorter plants growing below it called sciophytes (shade loving plants). They can photosynthesis in very low light conditions. They have larger photosynthetic units and hence they are able to carry out photosynthesis in filtered light.

1. Other factors necessary for photosynthesis may become limiting.
2. At high light intensities, the chlorophyll becomes destroyed due to photooxidation; hence the rate of photosynthesis decreases.

Mitochondria and Chloroplast are semi-autonomous organelles or endosymbionts of cells because they

1. Possess their own nucleic acid (DNA molecule).
2. Can form some of the required protein but for most of the proteins these are dependent on nuclear DNA and cytoplasmic ribosome.
3. Do not arise de novo.
4. Have membrane similar to those of bacteria.

Law of limiting factors states that when a physiological process is influenced by a number of factors, its rate will be determined by the factor which is the nearest to its minimal value (least). Blackman applied it to photosynthesis.

• A potted plant is kept in the dark for 48-72 hours for destarching.
• A part of a leaf is enclosed in a test tube containing some KOH (it absorbs the carbon dioxide), while the other half of the leaf is exposed to air.
• The set up is then kept in sunlight for some time.
• When the leaf is tested for starch, the exposed part of the leaf tested positive while the part enclosed in the test tube is tested negative.
• This shows that carbon dioxide is necessary for photosynthesis.

• Group A will show more photosynthesis.
• Chlorophyll absorbs maximum light in the blue region of the spectrum, i.e., 400-450 nm and hence photosynthetic rate will also be high.
• Group B will show negligible amount of photosynthesis or no photosynthesis.
• Chlorophyll does not absorb any light in the green region, i.e., 500-550 nm, but reflects green.

1. Absorption of light.
2. Splitting of water.
3. Oxygen release.
4. Formation of ATP and NADPH.

The different colors other than green are present in the plant because of presence of chromoplasts. It is a kind of plastid and develops different coloured pigments which are not photosynthetic. Pigment lycopene present in tomato, carrot and chillies, imparts red colour to them.

1. Photorespiration.
2. Yes, because by consuming oxygen at higher temperature, it protects the chlorophyll from photo-oxidation.

• Group A will show more photosynthesis.
• Chlorophyll absorbs maximum light in the blue region of the spectrum, i.e., 400-450 nm and hence photosynthetic rate will also be high.
• Group B will show negligible amount of photosynthesis or no photosynthesis.
• Chlorophyll does not absorb any light in the green region, i.e., 500-550 nm, but reflects green.

The acidic nature of lumen of thylakoids is due to the accumulation of protons by the photolysis of water. The same reaction does not occur in stroma so, it is basic in nature.

1. Ribulose 1, 5 bisphosphate.
2. It is the primary carbon dioxide acceptor.

The light transmitted through the tree canopy is of low intensity light. Therefore, plants growing under the canopy of others have adapted themselves to carryout photosynthesis in low light intensities.

Chlorophyll would not act as a limiting factor in photosynthesis, e.g., Sunloving plants contain less chlorophyll as compared to shadeloving plants, but the rate of photosynthesis in bright light is much higher in sunloving plants than is shadeloving plants.