Chapter 9, Problem 16STP

Summary Introduction

To name and describe:

Two enzymes involved in photosynthesis

Introduction:

Photosynthesis is an anabolic pathway in which light energy from the Sun is converted to chemical energy for use by the cell. Light energy is trapped by pigments called chlorophyll and is converted to chemical energy. Photosynthesis occurs in two phases; light dependent reaction and light independent reaction. The light dependent reaction is also called light reaction. In phase one or light reactions, light energy is converted into chemical energy in the form of ATP and NADPH. In phase two or light independent reactions, the ATP and NADPH are used to produce glucose.

Answer to Problem 16STP

Two most important enzymes used in photosynthesis are Rubisco and ATP synthase.

Rubisco is considered to be one of the most important biological enzymes as it converts inorganic carbon dioxide molecules into organic molecules. It helps in carbon fixation.

ATP synthase is an enzyme used during light reaction of photosynthesis to generate ATP.

Explanation of Solution

Rubisco- In the final step of the Calvin cycle, Rubisco, an enzyme converts ten G3P(glyceraldehyde 3-phosphate) molecules into 5- carbon molecules called ribulose 1,5- bisphosphates (RuBP). These molecules combine with new carbon dioxide molecules to continue the Calvin cycle.

ATP synthase- During light reactions, ATP is produced in conjunction with electron transport by the process of chemiosmosis. The H+ ions produced by splitting of water molecules accumulate in the interior of thylakoid. Due to difference in concentration of H+ ions in the interior of thylakoid and stroma, the H+ ions diffuse down the concentration gradient through ion channels. ATP synthases are the enzymes that help in diffusing of H+ ions. As a result of this movement, ATP is formed in the stroma.