Question 55
NECO_MODEL_QUESTIONS_VOL1
•
2023
•
ENGLISH_LANGUAGE
•
objective
Write an expository essay (250-300 words) explaining the process of photosynthesis. The essay must contain an introduction, three distinct stages of the process, a conclusion, and at least one scientific term (e.g., chlorophyll, thylakoid) italicised.
Answer Options
A.
An alternative explanation of photosynthesis mistakenly claims that the process begins with the absorption of carbon monoxide rather than carbon dioxide. In the first stage, *chlorophyll* in the *thylakoid* membranes is said to split carbon monoxide molecules, releasing nitrogen and generating ATP and NADPH. The second stage supposedly transports these energy carriers to the mitochondria, where they are used in a series of electron‑transfer reactions that actually belong to cellular respiration. The third stage, labeled as the Calvin cycle, is incorrectly described as a light‑dependent reaction that synthesizes glucose directly from carbon monoxide and water, producing oxygen as a by‑product. The conclusion of this erroneous account suggests that plants primarily produce nitrogen gas, which is not supported by scientific evidence.
B.
A common misconception about photosynthesis places the entire process inside the plant's mitochondria instead of the chloroplasts. According to this view, the first stage occurs in the mitochondrial inner membrane where *chlorophyll* captures light energy and splits water to release carbon dioxide. The second stage is presented as the electron transport chain of mitochondria, mistakenly using the term *thylakoid* to describe mitochondrial cristae. In the third stage, the Calvin cycle is said to happen in the mitochondrial matrix, where ATP and NADPH are used to convert carbon dioxide into glucose, even though these molecules are actually produced in the chloroplast. The conclusion incorrectly asserts that photosynthesis is a mitochondrial function, overlooking the essential role of chloroplasts and the true locations of the reactions.
C.
Photosynthesis is often described as the way plants turn sunlight into food, but this description contains several inaccuracies. In the first stage, the light‑dependent reactions are mistakenly said to take place in the stroma of the chloroplast, where *chlorophyll* supposedly captures light and directly converts carbon dioxide into oxygen, producing ATP and NADPH without water splitting. The second stage is described as a transport phase where the high‑energy carriers move through the cytoplasm, a process that does not actually occur in the thylakoid membrane. In the third stage, the so‑called Calvin cycle is incorrectly portrayed as occurring in the thylakoid lumen, using the ATP and NADPH to transform oxygen into glucose, which contradicts the true carbon fixation pathway. In conclusion, this version misplaces the locations of reactions and reverses the roles of oxygen and carbon dioxide, leading to a fundamentally flawed understanding of photosynthesis.
Correct Answer
D.
Photosynthesis is the fundamental process by which green plants convert solar energy into chemical energy, sustaining life on Earth. In the first stage, the light‑dependent reactions occur in the thylakoid membranes of the chloroplasts, where *chlorophyll* absorbs sunlight and uses it to split water molecules, releasing oxygen and generating ATP and NADPH. The second stage involves the transport of these high‑energy carriers through the thylakoid membrane, a series of electron‑transfer reactions that further amplify the energy captured from light. In the third stage, known as the Calvin cycle or light‑independent reactions, the ATP and NADPH produced earlier drive the fixation of carbon dioxide into glucose within the stroma of the chloroplast. This cycle repeats, gradually building complex carbohydrates that serve as food for the plant and, ultimately, for the entire food chain. In conclusion, photosynthesis transforms light into life‑supporting chemical energy through a coordinated sequence of reactions, highlighting the remarkable efficiency of plant biology and its essential role in global ecosystems.
Correct Answer
D
Correct Option:
Photosynthesis is the fundamental process by which green plants convert solar energy into chemical energy, sustaining life on Earth. In the first stage, the light‑dependent reactions occur in the thylakoid membranes of the chloroplasts, where *chlorophyll* absorbs sunlight and uses it to split water molecules, releasing oxygen and generating ATP and NADPH. The second stage involves the transport of these high‑energy carriers through the thylakoid membrane, a series of electron‑transfer reactions that further amplify the energy captured from light. In the third stage, known as the Calvin cycle or light‑independent reactions, the ATP and NADPH produced earlier drive the fixation of carbon dioxide into glucose within the stroma of the chloroplast. This cycle repeats, gradually building complex carbohydrates that serve as food for the plant and, ultimately, for the entire food chain. In conclusion, photosynthesis transforms light into life‑supporting chemical energy through a coordinated sequence of reactions, highlighting the remarkable efficiency of plant biology and its essential role in global ecosystems.
About This Question
This is
Neco Model Questions Vol1
2023
English Language
Question 55.
It is one of the
objective
questions from the
2023
Neco Model Questions Vol1
English Language
examination.
Difficulty level:
Hard
.