How Does Photosynthesis Compare To Cellular Respiration?

What is photosynthesis?

Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy, stored in glucose. It occurs in two main stages:

Light-dependent Reactions: ;These occur in the thylakoid membranes of the chloroplasts where chlorophyll absorbs light energy, which is then used to split water molecules (photolysis) into oxygen, protons, and electrons. The light energy is converted into chemical energy in the form of ATP and NADPH.

Calvin Cycle (Light-independent Reactions): ;These reactions occur in the stroma of the chloroplasts. ATP and NADPH produced in the light-dependent reactions are used to fix carbon dioxide into glucose through a series of enzyme-catalyzed steps.

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What is cellular respiration?

Cellular respiration is the process by which cells break down glucose and other organic molecules to produce ATP, the energy currency of the cell. It consists of several stages:

Glycolysis: ;Occurs in the cytoplasm and breaks down one molecule of glucose into two molecules of pyruvate, yielding 2 ATP and 2 NADH.

Link Reaction and Krebs Cycle: ;These occur in the mitochondrial matrix. Pyruvate is converted to Acetyl-CoA, which enters the Krebs cycle, producing ATP, NADH, and FADH₂;;;.

Electron Transport Chain (ETC) and Oxidative Phosphorylation: ;These occur in the inner mitochondrial membrane. Electrons from NADH and FADH₂;;; pass through the ETC, driving the production of ATP. Oxygen is the final electron acceptor, forming water.

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Exam Tips: Answering Questions on Photosynthesis vs. Cellular Respiration

Understand the Processes Thoroughly: ;Be familiar with each step of both photosynthesis and cellular respiration. Know the inputs and outputs, where each process takes place, and the role of each molecule involved.

Use Comparative Language: ;When asked to compare and contrast, use precise language like “in contrast,” “however,” “similarly,” or “both.”

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Draw and Annotate Diagrams: For questions that require diagrams, ensure you can draw and label the chloroplast and mitochondria, indicating where each stage of the process occurs. Annotate key steps to show understanding.

Memorize Key Differences and Similarities: ;Use tables or flashcards to memorize the key differences and similarities between photosynthesis and cellular respiration. This can help you quickly recall information in exam conditions.

Practice Past Paper Questions: ;Utilize past papers and sample questions to practice comparing and contrasting these processes. Pay attention to mark schemes to understand how points are awarded for detail and clarity.

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