Photosynthesis lesson 2 of 2

structure, adaptations and functions of photosynthesis, chemistry of photosynthesis(light harvesting, electron transport and Calvin cycle), C3 and C4 plants, advantages of C4 plants over C3 plant, differences between respiration and photosynthesis.



Structure and Adaptations of Photosynthesis:
- Photosynthesis occurs in the chloroplasts of plant cells.
- Chloroplasts contain a green pigment called chlorophyll, which captures sunlight.
- The chloroplasts have an inner membrane, outer membrane, and thylakoid membranes, where the various stages of photosynthesis take place.
- The thylakoid membranes are arranged in stacks called grana, and the fluid-filled space surrounding the grana is called the stroma.
- Adaptations of photosynthesis include the presence of large surface areas with abundant chloroplasts in leaves, and the arrangement of chlorophyll molecules in the thylakoid membranes to maximize light absorption.

Functions of Photosynthesis:
- Conversion of sunlight energy into chemical energy in the form of glucose.
- Production of oxygen as a byproduct, which is released into the atmosphere.
- Biosynthesis of carbohydrates and other organic compounds necessary for the plant's growth and maintenance.

Chemistry of Photosynthesis:
1. Light Harvesting: Chlorophyll absorbs photons of light energy, exciting electrons and initiating the process.
2. Electron Transport: Excited electrons are passed through a series of electron carriers within the thylakoid membranes, generating ATP and reducing NADP+ to NADPH.
3. Calvin Cycle: This occurs in the stroma and involves a series of enzyme-mediated reactions that use ATP and NADPH to convert carbon dioxide into glucose.

C3 and C4 Plants:
- C3 plants: Common plants like wheat, rice, and oats that directly use the C3 pathway in photosynthesis. In this pathway, carbon dioxide is initially fixed into a three-carbon compound.
- C4 plants: Plants like corn, sugarcane, and sorghum that have an additional step before entering the C3 pathway. They first fix carbon dioxide into a four-carbon compound, helping them adapt to hotter and drier environments.

Advantages of C4 Plants over C3 Plants:
- C4 plants have a higher rate of photosynthesis and can better withstand high temperatures and low carbon dioxide conditions.
- Their unique carbon fixation process allows them to efficiently use water and nutrients, promoting their growth in arid conditions.
- C4 plants often exhibit better water use efficiency compared to C3 plants.

Differences between Respiration and Photosynthesis:
1. Respiration occurs in all living cells, while photosynthesis occurs only in plants, algae, and some bacteria.
2. Respiration involves the breakdown of glucose to produce ATP, releasing carbon dioxide as a byproduct, while photosynthesis fixes carbon dioxide to produce glucose, releasing oxygen as a byproduct.
3. Respiration occurs continuously, while photosynthesis typically occurs during daylight hours.
4. Respiration releases energy, while photosynthesis stores energy.