A Level Biology Revision Lesson 214:

Photosynthesis: - The Calvin Cycle

Task 1. Check Where this Lesson fits into your Exam Specification!

Task 2. Watch the Revision Lessons in Full.


Check Your Spec!

★ AQA A Level Biology Specification Reference: - 3.5.1 Photosynthesis (A-level only). The light-independent reaction in such detail as to show that: Carbon dioxide reacts with ribulose bisphosphate (RuBP) to form two molecules of glycerate 3-phosphate (GP). This reaction is catalysed by the enzyme rubisco. ATP and reduced NADP from the light-dependent reaction are used to reduce GP to triose phosphate. Some of the triose phosphate is used to regenerate RuBP in the Calvin cycle. Some of the triose phosphate is converted to useful organic substances.


★ CIE A Level Biology Specification Reference: -13.1 Photosynthesis as an energy transfer process. Light energy absorbed by chloroplast pigments in the light dependent stage of photosynthesis is used to drive reactions of the light independent stage that produce complex organic compounds. Chromatography is used to identify chloroplast pigments and was also used to identify the intermediates in the Calvin cycle. Explain that energy transferred as ATP and reduced NADP from the light dependent stage is used during the light independent stage (Calvin cycle) of photosynthesis to produce complex organic molecules. State the sites of the light dependent and the light independent stages in the chloroplast. Outline the three main stages of the Calvin cycle: Fixation by rubisco of carbon dioxide by combination with ribulose bisphosphate (RuBP), a 5C compound, to yield two molecules of GP (PGA), a 3C compound. The reduction of GP to triose phosphate (TP) involving ATP and reduced NADP. The regeneration of ribulose bisphosphate (RuBP) using ATP. Describe, in outline, the conversion of Calvin cycle intermediates to carbohydrates, lipids and amino acids and their uses in the plant cell.


★ Edexcel A Level Biology (Biology A – Salters-Nuffield) Specification Reference: - Topic 5: On the Wild Side: 5.8 i) Understand the light-independent reactions as reduction of carbon dioxide using the products of the light-dependent reactions (carbon fixation in the Calvin cycle, the role of GP, GALP, RuBP and RUBISCO). ii) Know that the products are simple sugars that are used by plants, animals and other organisms in respiration and the synthesis of new biological molecules (polysaccharides, amino acids, lipids and nucleic acids).

★ Edexcel A Level Biology (Biology B) Specification Reference: - Topic 5: Energy for Biological Processes. 5.7 Photosynthesis: - Light-independent stage: Understand the role of the stroma in the light-independent stage of photosynthesis. Understand how carbon dioxide is fixed by combination with 5C ribulose bisphosphate (RuBP) to form glycerate 3-phosphate (GP) using the enzyme ribulose bisphosphate carboxylase (RUBISCO). Understand how reduced NADP and ATP from the light-dependent stage are used: to synthesise glyceraldehyde phosphate (GALP) from GP, to regenerate 5C ribulose bisphosphate in the Calvin cycle (details of intermediate compounds are not required). Understand how GALP is used as a raw material in the production of monosaccharides, amino acids and other molecules.

★ OCR A Level Biology (Biology A) Specification Reference: - 5.2 Energy for biological processes. 5.2.1 Photosynthesis: (e) the fixation of carbon dioxide and the light independent stage of photosynthesis: To include how the products of the light-dependent stage are used in the light-independent stage (Calvin cycle) to produce triose phosphate (TP) with reference to ribulose bisphosphate (RuBP), ribulose bisphosphate carboxylase (RuBisCO) and glycerate 3-phosphate (GP) – no other biochemical detail is required. (f) the uses of triose phosphate (TP) To include the use of TP as a starting material for the synthesis of carbohydrates, lipids and amino acids AND the recycling of TP to regenerate the supply of RuBP.

★ OCR A Level Biology (Biology B) Specification Reference: - Module 4: Energy, reproduction and populations: 4.3 Photosynthesis, food production and populations - 4.3.1 Photosynthesis, food production and management of the environment : c) the production of complex organic molecules in the light-independent stage of photosynthesis (Calvin cycle). To include the use of the products of the light-dependent reactions (ATP and reduced NADP) within the light-independent reactions AND the role of carbon dioxide, ribulose bisphosphate carboxylase (RuBisCO), ribulose bisphosphate (RuBP), glycerate-3-phosphate (GP) and triose phosphate (TP) but no other biochemical detail is required. e) the metabolism of TP and GP to produce carbohydrates, lipids and amino acids. To include reference to the need for appropriate mineral ions (e.g. nitrates and sulfates in relation to amino acids).


★ WJEC A Level Biology Specification Reference: - Energy for Life: 2. Photosynthesis uses light energy to synthesise organic molecules. Learners should be able to demonstrate and apply their knowledge and understanding of: (h) reduced NADP as a source of reducing power and ATP as a source of energy for the following reactions: the light-independent stage and the formation of glucose; uptake of carbon dioxide by ribulose bisphosphate to form glycerate-3-phosphate catalysed by Rubisco. (i) the reduction of glycerate-3-phosphate to produce triose phosphate (carbohydrate) with the regeneration of ribulose bisphosphate. (j) the production of other carbohydrates, lipids and amino acids from the triose phosphate (no details of the chemistry of these processes is needed).

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