Question
▶️Answer/Explanation
Explanation:
Insulin is a globular protein made up of two separate polypeptide chains (A and B) linked by disulfide bridges. It has a quaternary structure because it consists of more than one chain. The folding and bonding give insulin its functional three-dimensional shape.
Option Evaluation:
A. Incorrect – Fibrous proteins (like collagen) are long and strand-like. Insulin is globular, not fibrous, and the diagram shows folded chains, not just a linear pattern.
B. Incorrect – Insulin is made of two chains, not a single continuous chain. It has two ends per chain, not just one amino and one carboxyl end total.
C. Correct – Insulin consists of two chains (A and B), connected by three disulfide bridges (two between chains, one within chain A), giving it tertiary and quaternary structure.
D. Incorrect – While the diagram shows the sequence of amino acids (primary structure), the presence of disulfide bridges and two chains indicates tertiary and quaternary structure, not just primary and secondary.
Question
What is the function of tRNA-activating enzymes in protein synthesis?
A. They attach amino acids to tRNA molecules using ATP.
B. They activate tRNA and amino acids during transcription.
C. They synthesise ATP and bind it to specific tRNA molecules.
D. They allow the formation of H bonds between tRNA anticodons and specific amino acids.
▶️Answer/Explanation
Answer: A. They attach amino acids to tRNA molecules using ATP.
A. Correct – These enzymes use ATP to link a specific amino acid to its correct tRNA. This step “activates” the tRNA so it can bring the amino acid to the ribosome during translation.
B. Incorrect – Transcription is the process of making mRNA from DNA and doesn’t involve tRNA-activating enzymes. These enzymes work before translation, not transcription.
C. Incorrect – tRNA-activating enzymes do not make ATP. They use ATP to help bind amino acids to tRNA, but they don’t synthesize ATP.
D. Incorrect – Hydrogen bonds form between tRNA anticodons and mRNA codons, not between tRNA and amino acids. The enzyme forms a covalent bond between the amino acid and tRNA.
Question
The three-toed sloth, Bradypus variegatus, lives in treetops where it feeds on leaves. It also feeds on algae and fungi which live in its fur.
In which trophic group should the three-toed sloth be classified?
A. Autotroph
B. Consumer
C. Detritivore
D. Saprotroph
▶️Answer/Explanation
Answer: B. Consumer
Explanation:
What are trophic groups?
Trophic groups describe how organisms get their food. Autotrophs make their own food (like plants). Consumers eat other organisms. Detritivores feed on dead material. Saprotrophs break down dead organic matter using external enzymes.
A. Incorrect – Autotrophs make their own food using sunlight or chemicals. The sloth does not do this.
B. Correct – The sloth feeds on living plant material (leaves) and also on algae and fungi. This means it consumes other living organisms, so it’s a consumer.
C. Incorrect – Detritivores eat dead material (like earthworms). The sloth eats living things, not dead material.
D. Incorrect – Saprotrophs (like fungi and bacteria) break down dead organisms using enzymes. The sloth does not do this.
Question
Which processes occur in an ecosystem?
I. Biomass increases in each successive trophic level.
II. Inorganic nutrients are recycled.
III. Chemical energy is stored in carbon compounds.
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
▶️Answer/Explanation
Answer: C. II and III only
Explanation:
What happens in ecosystems?
In an ecosystem, energy flows from producers to consumers, but some energy is lost at each level. Biomass generally decreases up the food chain. Inorganic nutrients like carbon and nitrogen are recycled. Energy is stored in organic molecules like carbohydrates.
I. Incorrect – Biomass actually decreases as you go up the food chain, because energy is lost as heat and waste.
II. Correct – Nutrients like nitrogen, carbon, and phosphorus are recycled by decomposers and returned to the environment.
III. Correct – Plants convert light energy into chemical energy stored in molecules like glucose (carbon compounds).
Therefore, II and III are correct
Question
A hummingbird is shown visiting a large flower.
What makes this a mutualistic relationship?
A. The bird feeds on nectar and transfers pollen to the stamen of a flower of the same species.
B. The bird obtains nutrients, and the plant is assisted with pollination for sexual reproduction.
C. The bird requires pollen as a protein source and, while obtaining this, disperses seeds for the plant.
D. The bird transfers pollen to the stigma of flowers of a different species while feeding.
Answer/Explanation
Answer: B. The bird obtains nutrients, and the plant is assisted with pollination for sexual reproduction.
Explanation:
What is mutualism?
Mutualism is a type of symbiotic relationship where both species benefit. In this case, the bird gets food (nectar), and the plant gets help with pollination, which increases its chances of reproduction.
A. Incorrect – The bird transfers pollen to the stigma (female part), not the stamen (male part). This choice shows misunderstanding of flower parts.
B. Correct – This option clearly shows that both species benefit: the bird gets nutrients, and the plant gets pollinated.
C. Incorrect – Birds do not disperse seeds when eating pollen. Also, birds usually don’t eat pollen for protein they seek nectar.
D. Incorrect – Pollination is successful only when pollen reaches a flower of the same species. Transferring pollen to a different species doesn’t benefit the plant.