Biochemistry

Analysis of Statements:

✅ Option 1: "Km: Approximate inverse measure of the affinity of the enzyme for a given substrate." 🔹 Correct. Km (Michaelis constant) is an approximate inverse measure of enzyme-substrate affinity. A lower Km indicates higher affinity.

❌ Option 2: "Km: Approximate measure of the concentration of substrate at which the reaction rate is half of the maximum rate." 🔹 Incorrect. Km represents the substrate concentration at which the reaction rate reaches half of Vmax, but it is not just an "approximate measure" of concentration needed for half-maximal activity.

✅ Option 3: "Enzymes generally function in a broad range of temperature and pH." 🔹 Correct. Enzymes have optimal temperature and pH but can still function in a broader range, albeit with lower efficiency.

✅ Option 4: "2.7.1.2 is enzyme code for Glucose-6-Phosphotransferase." 🔹 Correct. The enzyme commission (EC) number 2.7.1.2 belongs to Glucose-6-Phosphotransferase.

Incorrect Statement: Option (2)

Let’s analyze the correct matches based on plant characteristics:

• Maize: Maize (corn) has photosynthetic roots. The roots are capable of photosynthesis, which helps in supporting the plant. Hence, Maize matches with E (Photosynthetic roots).
• Striga: Striga is a partial parasite, which attaches itself to the roots of other plants and derives nutrients. So, Striga matches with A (Partial parasite).
• Banyan: The Banyan tree produces prop roots. These roots grow downward from the branches to the soil. Hence, Banyan matches with C (Prop roots).
• Taeniophyllum: Taeniophyllum has velamen roots, a type of root that serves as a protective layer and is found in epiphytic plants like orchids. So, Taeniophyllum matches with D (Velamen roots).

Thus, the correct matching is:

• I (Maize) = E (Photosynthetic roots)
• II (Striga) = A (Partial parasite)
• III (Banyan) = C (Prop roots)
• IV (Taeniophyllum) = D (Velamen roots)

The correct answer is: (2) I-B, II-A, III-C, IV-E.

The cup or saucer-shaped ascocarp is characteristic of Apothecium, which is a type of ascocarp found in several Ascomycetes fungi.

• Penicillium produces Perithecium, which is an entirely different shape (globose or flask-shaped).
• Claviceps forms Cleistothecium, which is spherical and does not have an open cup shape.
• Neurospora produces Apothecium, which is a large, open, cup-like ascocarp. This matches the description of a cup or saucer-shaped ascocarp.
• Aspergillus forms Ascohecium, but this is not the typical description of a cup-shaped ascocarp.

Thus, the correct answer is: (3) Neurospora, Apothecium.

Matching the Items

Let's match the items:

• A. Creutzfeldt Jakob: This is a prion disease, which is related to the misfolding of proteins.
  Hence, A matches with III (prions).
• B. Swollen shoot: This disease is caused by a viroid, which is a small infectious RNA molecule.
  Hence, B matches with II (viroid).
• C. Bovine Encephalitis: This disease is associated with a tiny nucleic acid in the form of a virus, affecting cattle's brain.
  Hence, C matches with IV (tiny nucleic acid).
• D. Cucumber: This is typically affected by a virus, as it causes various diseases like mosaic in cucumbers.
  Hence, D matches with I (virus).

Thus, the correct matching is:

A-III, B-II, C-IV, D-I

Therefore, the correct answer is (1) A-III, B-II, C-IV, D-I.

Analyzing Each Statement

• I. Primary cell wall is capable of growth in mature plant cell: This statement is incorrect. The primary cell wall is capable of growth in young, developing cells, not in mature plant cells. In mature plant cells, it is the secondary wall (if formed) that provides strength and rigidity.
• II. Middle lamella is the first formed layer of the cell wall and it is the outermost layer in mature plant cells: This statement is correct. The middle lamella is indeed the first layer formed during cell division, and it lies between adjacent plant cells, forming the outermost layer in mature cells.
• III. Addition of lignin in cellulose inter-fibrillar spaces leads to the formation of the secondary cell wall in mature plant cells: This statement is correct. The secondary cell wall is formed in mature plant cells by the addition of lignin to the cellulose fibrils, which strengthens the wall.

Thus, the correct answer is (3) II, III.

Golden Rice and Its Nutritional Benefit

Golden rice is genetically modified to produce Beta Carotene, which is a precursor of Vitamin A.

• This nutrient is more abundant in Golden rice compared to conventional rice.
• The genetic modification enables the rice to produce higher levels of beta carotene, which the human body can convert into Vitamin A.

Thus, the correct answer is: (D) Beta Carotene.

Hypostomatic Leaves and Structural Adaptations

In plants, hypostomatic refers to the condition where stomata are present on the lower surface of the leaf. Additionally, sunken stomata and stomatal hairs are structural adaptations that help reduce water loss through transpiration, especially in plants growing in arid conditions.

• Option 1: "Nymphaea" ❌ Incorrect. Nymphaea (water lily) typically has stomata on the upper surface, not sunken.
• Option 2: "Nerium" ✅ Correct. Nerium (oleander) has hypostomatic leaves with sunken stomata and stomatal hairs, which help minimize water loss.
• Option 3: "Typha" ❌ Incorrect. Typha (cattails) has different leaf adaptations, but not sunken stomata or stomatal hairs.
• Option 4: "Sagittaria" ❌ Incorrect. Sagittaria (arrowhead) does not exhibit sunken stomata and stomatal hairs like Nerium.

Thus, the correct answer is: (2) Nerium.

Calculation of Cytosine Molecules in a dsDNA Molecule

In a double-stranded (ds) DNA molecule, the number of hydrogen bonds between the bases follows the rule:

• A-T pairs contribute 2 hydrogen bonds.
• C-G pairs contribute 3 hydrogen bonds.

Given that there are 480 hydrogen bonds in total and 20 coils of DNA, let's analyze the distribution:

Let the number of C-G pairs be . Since each C-G pair has 3 hydrogen bonds, the total contribution from C-G pairs is:

Let the number of A-T pairs be . Since each A-T pair has 2 hydrogen bonds, the total contribution from A-T pairs is:

Now, the total number of hydrogen bonds is given by:

Also, the total number of base pairs equals the number of coils:

Solving these equations:

From the second equation:

Substituting into the first equation:

So, the number of C-G pairs (cytosine paired with guanine) is 80, and since each C-G pair contains one cytosine molecule, the total number of cytosine molecules is:

80

Therefore, the correct answer is (2) 80.

Chromosome Number in Maize Root Cells

In maize root cells:

• G1 Phase: At the G1 phase, the cell contains the full set of chromosomes, which is 20 in this case.
• S Phase: During the S phase, DNA replication occurs, and the chromosomes duplicate. However, the chromosome number in the cell remains 20, as each chromosome has only replicated into two sister chromatids, still counted as one chromosome each.
• M Phase (Mitosis): During mitosis, the chromosomes are segregated into two daughter cells, maintaining the same chromosome number, which remains 20 in both daughter cells.

Thus, the number of chromosomes at each stage (G1, after S, and after M) in maize root cells is:

20, 20, 20

The correct answer is (1) 20, 20, 20.

Analysis of the Statements

Let's analyze the statements:

• I. Rate of respiration in plants is less than in animals: This statement is correct. Plants generally have a slower rate of respiration compared to animals, as their metabolic processes are less energy-demanding.
• II. Loose packing of parenchyma cells: This statement is correct. Parenchyma cells in plants are loosely packed, providing spaces for gas exchange within the plant tissues. This is why plants do not need specialized respiratory organs like animals.
• III. Most cells of a plant have at least a part of their surface in contact with air: This statement is correct. Since many plant cells are exposed to air, gas exchange can occur directly across the surface of the cells without the need for specialized respiratory organs.
• IV. Transport of gases within the plant is more: This statement is incorrect. While plants do transport gases (such as oxygen and carbon dioxide) via diffusion through stomata, the transport is not as efficient as in animals that have specialized respiratory organs. This is one of the reasons why plants do not require distinct respiratory organs.

Thus, the correct reasons are I, II, and III.

Therefore, the correct answer is (2) I, II, III.