5.3 Light-Independent Reactions Unit 5: Cell Energy 5.3 Light-Independent Reactions

Light-Independent Reactions During light-independent reactions, ATP and NADPH from light- dependent reactions are used to produce high- energy sugars Also known as the Calvin Cycle

Summary No light is required ATP and NADPH are used to make sugars Take place in the stroma Carbon dioxide is required

Summary Carbon Dioxide enters the cycle Sugar Production Six CO2 molecules from the atmosphere combine with six 5-carbon molecules Produces twelve 3-carbon compounds Sugar Production Energy from ATP and NADPH are used to convert the 3-carbon molecules Two of the twelve 3-carbon molecules are removed from the cycle to produce sugars, lipids, amino acids, etc. Remaining ten 3-carbon molecules are converted back into 5-carbon forms that start the cycle again

PGA: Phosphoglyceric acid RuBP: Rubulose Biphosphate G3P: Glyceraldehyde-2-phosphate

Animation https://www.youtube.com/watch?v=E_XQR800AgM

Factors Affecting Photosynthesis

Factors that Influence the Rate of Photosynthesis Many factors influence the rate of photosynthesis. The most important are: Temperature Enzymes function best at 0⁰-35⁰ C An increase or decrease in temperature will slow the reaction

Factors that Influence the Rate of Photosynthesis Light Intensity High light intensity increases the rate of photosynthesis At a certain level, the rate reaches its max and levels off

Factors that Influence the Rate of Photosynthesis Availability of Water Water shortage can stop photosynthesis Water loss can damage plant tissues Plants living in dry conditions often have waxy leaves