Biology: Autotrophs and Photosynthesis

Autotrophs

Autotrophs are organisms that produce their own food through various metabolic processes. There are two main types of autotrophs: photoautotrophs and chemoautotrophs.

Photosynthesis

Definition: Photosynthesis is the process by which photoautotrophs convert light energy from the sun into chemical energy in the form of organic compounds, such as glucose.

Light-Dependent Reactions:

• Occur in thylakoid membranes of chloroplasts
• Light energy is absorbed by pigments (e.g., chlorophyll) and converted into ATP and NADPH

Light-Independent Reactions (Calvin Cycle):

• Occur in stroma of chloroplasts
• ATP and NADPH from light-dependent reactions are used to convert CO2 into glucose

Overall Equation: 6 CO2 + 6 H2O + light energy → C6H12O6 (glucose) + 6 O2

Cellular Respiration

Definition: Cellular respiration is the process by which cells generate energy from glucose and other organic molecules.

Stages of Cellular Respiration:

1. Glycolysis: Breakdown of glucose into pyruvate, producing ATP and NADH
2. Pyruvate Oxidation: Conversion of pyruvate into acetyl-CoA, producing NADH and FADH2
3. Citric Acid Cycle (Krebs Cycle): Breakdown of acetyl-CoA into CO2, producing ATP, NADH, and FADH2
4. Electron Transport Chain: Transfer of electrons from NADH and FADH2 to generate ATP

Overall Equation: C6H12O6 (glucose) + 6 O2 → 6 CO2 + 6 H2O + ATP (energy)

Autotrophs

• Autotrophs are organisms that produce their own food through various metabolic processes.
• There are two main types of autotrophs: photoautotrophs and chemoautotrophs.

Photosynthesis

• Photosynthesis is the process by which photoautotrophs convert light energy from the sun into chemical energy in the form of organic compounds, such as glucose.
• Light energy is absorbed by pigments (e.g., chlorophyll) and converted into ATP and NADPH in the light-dependent reactions.
• ATP and NADPH from light-dependent reactions are used to convert CO2 into glucose in the light-independent reactions (Calvin Cycle).
• The overall equation for photosynthesis is: 6 CO2 + 6 H2O + light energy → C6H12O6 (glucose) + 6 O2.

Cellular Respiration

• Cellular respiration is the process by which cells generate energy from glucose and other organic molecules.
• The stages of cellular respiration include: glycolysis, pyruvate oxidation, citric acid cycle (Krebs Cycle), and electron transport chain.
• Glycolysis breaks down glucose into pyruvate, producing ATP and NADH.
• Pyruvate oxidation converts pyruvate into acetyl-CoA, producing NADH and FADH2.
• The citric acid cycle (Krebs Cycle) breaks down acetyl-CoA into CO2, producing ATP, NADH, and FADH2.
• The electron transport chain transfers electrons from NADH and FADH2 to generate ATP.
• The overall equation for cellular respiration is: C6H12O6 (glucose) + 6 O2 → 6 CO2 + 6 H2O + ATP (energy).