Bioenergetics

Bioenergetics: Study of energy transformation in living organisms (acquiring, converting, and storing energy).

Oxidation-Reduction (Redox):

• Oxidation: Loss of electrons under energy release.
• Reduction: Gain of electrons under energy storage.

Adenosine Triphosphate (ATP): Main energy source for cells. Discovered causing energy transfer by Fritz Lipmann.

Structure: 1. Adenine (base) 2. Ribose (sugar) 3. Three Phosphate groups.

Function: Breaking one phosphate bond releases ~7.3 kcal/mole energy, forming ADP (Adenosine Diphosphate). Common in energy-releasing (exergonic) and consuming (endergonic) processes.

Synthesis of glucose from $CO_2$ and $H_2O$ using sunlight and Chlorophyll, releasing Oxygen.

Phases:

1. Light Reactions (in Thylakoids): Captures light energy to make ATP and NADPH. Splits water (Photolysis) releasing Oxygen.
2. Dark Reactions (Calvin Cycle, in Stroma): Uses ATP and NADPH to reduce $CO_2$ into Glucose. Discovered by Melvin Calvin.

Chlorophyll: Main pigment, absorbs Blue and Red light. Accessory pigments absorb other wavelengths.

Process of oxidation of food (Glucose) to release energy (ATP). Two types:

• Aerobic Respiration: Uses Oxygen. Complete oxidation. High energy yield.
• Anaerobic Respiration (Fermentation): No Oxygen. Incomplete oxidation. Low energy yield.

1. Glycolysis (in Cytoplasm): Glucose (6C) splits into 2 Pyruvic molecules (3C). Produces 2 ATP, 2 NADH. Occurs in both aerobic and anaerobic.
2. Krebs Cycle (in Mitochondria): Pyruvic acid oxidizes into Acetyl CoA, then enters cycle producing $CO_2$, ATP, NADH, $FADH_2$. (Discovered by Hans Krebs).
3. Electron Transport Chain (ETC): NADH and $FADH_2$ release electrons. Energy used to create bulk ATP. Oxygen combines with H to form Water.

• Alcoholic Fermentation: Pyruvic acid -> Alcohol + $CO_2$ (Bacteria, Yeast). Used in baking/brewing.
• Lactic Acid Fermentation: Pyruvic acid -> Lactic acid (Skeletal muscles of humans during hard exercise, Bacteria). Used in yogurt/cheese.