3/31 bio 150

Enzyme Function: The enzyme discussed catalyzes the reaction of adding carbon dioxide to a carbonyl carbon, resulting in a relatively unstable configuration.
Key Product: This reaction leads to the formation of
- 3-Carbon Phosphoglycerate (3-PGA)
- Following phosphorylation, it is converted into 1,3-Bisphosphoglycerate (1,3-BPG).

Photosynthesis Pathway:
- Carbon dioxide is incorporated into 3-PGA, which is then phosphorylated.
- Reduction using NADPH leads to the formation of glyceraldehyde.
- This process occurs in chloroplasts within plant cells.
Reverse of Glycolysis: In contrast, the glycolytic pathway occurs in the cytoplasm of both plant and animal cells, highlighting the universality of glycolysis.

Dark Reactions of Photosynthesis: Defined as operating in reverse of glycolysis, indicating an interconnectedness in biochemical pathways.
Role of Gibbs Free Energy: Shifting the concentration ratios of products and reactants can influence the direction of reactions.

Ribulose biphosphate carboxylase: This enzyme can also act as an oxygenase, which means it can bind oxygen in addition to carbon dioxide; this binding is less effective, leading to alternate products (glycolate).
Byproduct Management: Glycolate is transported to the peroxisome and converted into glyoxylate and subsequently to glycine, allowing for the release of carbon dioxide.

Experimental Genetic Insertion: Two genes were inserted into tobacco cells to enhance efficiency in photosynthesis, more specifically, genes for glycolate dehydrogenase and malate synthetase.
Outcome of Genetic Modification: Instead of producing glycolate from carbon dioxide, the modified plants convert it into malate, which enters the Krebs cycle for energy production without wasting carbon.
RNA Inhibition Technique: Preventing glycolate from exiting the cell; this led to a 40% increase in photosynthesis efficiency by retaining carbon.

Introduction to C4 Pathway: Research led to a distinction between C3 plants and C4 plants in their photosynthetic processes.
- Initial Fixation: In C4 plants like sugarcane, the first stable product is oxaloacetate, catalyzed by PEP carboxylase, unlike the 3-PGA in C3 plants.
- Cellular Specialization: C4 photosynthesis occurs in mesophyll cells and bundle sheath cells, while C3 occurs only in mesophyll.

Anatomy: C4 plants possess chloroplasts in bundle sheath cells, while C3 plants do not. This anatomical feature reflects adaptations to enhance photosynthetic efficiency in hot environments.
Gas Exchange: C4 plants exhibit reduced oxygen interference during the Calvin cycle due to cellular arrangement, allowing them to minimize carbon loss in arid conditions.

Michaelis-Menten Kinetics: PEP carboxylase has a lower Km value compared to RUBISCO, making it more efficient in binding carbon dioxide.
Practical Examples: Observational differences in carbon dioxide levels in cornfields versus highways illustrate the efficiency of C4 plants in utilizing carbon dioxide under competitive conditions.

C4 Plant Examples: Corn, sugarcane, and sorghum are all C4 plants with adaptations allowing them to grow efficiently under high temperature and dry conditions.
Adaptations: The anatomical changes in C4 plants also lead them to be more competitive against traditional grass types seen in less arid environments.

Crassulacean Acid Metabolism (CAM): A unique modification where carbon fixation occurs at night to minimize water loss, seen in plants like cacti and pineapples.
Process Overview: Similar to C4 but temporally distinct, allows fixation during cooler night hours and release during the day for photosynthesis.

Cellular Respiration: Will explore how cells manage genetic information and reproduce.
Cell Division and Cycle Overview:
- Asexual reproduction (binary fission) leads to genetically identical offspring.
- Sexual reproduction (meiosis) results in genetic diversity.

Mitosis Process: Involves condensation of chromatin into chromosomes and separation into two daughter cells. Cytokinesis is the process that leads to the physical division.
Differences in Plant and Animal Cell Division: Includes unique methods of cytokinesis (cleavage furrow vs. cell plate).