when plants do not receive enough water their photosynthetic rate drops this is because

HESI A2

HESI A2 Biology Practice Test

1. When plants do not receive enough water, their photosynthetic rate drops. This is because:

A. water is a raw material for the light reactions in photosynthesis
B. carbon dioxide is not available
C. water provides the carbon atoms used to make sugar
D. not enough oxygen is produced to keep fermentation running

Correct answer: A

Rationale: When plants do not receive enough water, their photosynthetic rate drops because water is a raw material required for the light reactions in photosynthesis. In the light reactions, water is split to provide electrons, which are then utilized to produce energy carriers used in converting carbon dioxide into glucose during the Calvin cycle. Therefore, without sufficient water, the light reactions cannot proceed effectively, ultimately leading to a decrease in photosynthetic rate. Choice B is incorrect because carbon dioxide is a separate raw material needed for the Calvin cycle, not the light reactions. Choice C is incorrect as water provides electrons, not carbon atoms, for photosynthesis. Choice D is incorrect because fermentation is not directly related to photosynthesis; oxygen is produced during photosynthesis, not fermentation.

2. What is the role of tRNA during protein synthesis?

A. Carries amino acids to the ribosome
B. Links nucleotides together
C. Copies DNA sequences
D. Replicates genetic material

Correct answer: A

Rationale: During protein synthesis, tRNA plays the crucial role of carrying amino acids to the ribosome. This process ensures that the correct amino acids are brought to the ribosome according to the mRNA sequence. Choice B, linking nucleotides together, refers to the role of RNA polymerase in transcription, not tRNA. Choice C, copying DNA sequences, is the function of DNA polymerase during DNA replication, while choice D, replicating genetic material, is an overarching function of DNA replication, not specific to tRNA's role in protein synthesis.

3. Which organelle is responsible for making proteins?

A. Ribosome
B. Chloroplast
C. Lysosome
D. Mitochondrion

Correct answer: A

Rationale: Ribosomes are the organelles responsible for protein synthesis within the cell. They are the sites where amino acids are linked together to form proteins based on the instructions carried by mRNA (messenger RNA). Ribosomes can be found free-floating in the cytoplasm or attached to the endoplasmic reticulum, and they play a crucial role in translating genetic information into proteins. Chloroplasts are responsible for photosynthesis, lysosomes are involved in digestion and waste removal, and mitochondria are known as the powerhouse of the cell responsible for energy production through cellular respiration. Therefore, the ribosome is the correct organelle responsible for making proteins.

4. Which of the following is a protein?

A. cellulose
B. hemoglobin
C. estrogen
D. ATP

Correct answer: B

Rationale: The correct answer is 'hemoglobin' because it is a protein that carries oxygen in the blood. Cellulose is a carbohydrate found in the cell walls of plants, not a protein. Estrogen is a hormone, not a protein. ATP (adenosine triphosphate) is a molecule that carries energy within cells, not a protein.

5. In an example of a male with hemophilia and a female carrier, what ratio of the offspring are predicted neither to carry nor to manifest the disease?

A. 0 females : 1 male
B. 1 female : 1 male
C. 1 female : 0 males
D. 2 females : 1 male

Correct answer: D

Rationale: In this scenario, the male offspring will inherit the Y chromosome from the father and the X chromosome from the carrier mother. As a result, they will not have the hemophilia gene. The female offspring will inherit one X chromosome from the mother, which does not carry the hemophilia gene, and one X chromosome from the father, which does not exist due to the Y chromosome. Therefore, all female offspring will not carry or manifest hemophilia, resulting in a ratio of 2 females to 1 male. Choice A is incorrect because it does not account for the female offspring. Choices B and C are incorrect as they do not reflect the correct ratio based on the inheritance pattern of hemophilia.