π Photosynthesis: Capturing Sunlight's Energy
Photosynthesis is how plants and some bacteria convert light energy into chemical energy in the form of glucose (sugar). It's essentially how they make their food! This process occurs in chloroplasts, organelles found in plant cells.
- βοΈ Light-Dependent Reactions:
- π Water (H\βO) is split: This releases oxygen (O\β) as a byproduct, which is why plants are essential for us to breathe. Electrons are also released, powering the next stage.
- β‘ Energy Capture: Light energy is captured by chlorophyll and used to create ATP (energy currency) and NADPH (reducing power).
- π Light-Independent Reactions (Calvin Cycle):
- π¨ Carbon Dioxide (CO\β) is fixed: CO\β from the atmosphere is incorporated into organic molecules.
- π¬ Sugar Production: ATP and NADPH are used to convert the fixed carbon dioxide into glucose (C\βH\ββO\β).
π₯ Cellular Respiration: Releasing Energy from Glucose
Cellular respiration is the process by which organisms break down glucose to release energy in the form of ATP. This happens in the mitochondria of eukaryotic cells (and in the cytoplasm of prokaryotic cells).
- π§ͺ Glycolysis:
- πͺ Glucose Breakdown: Glucose is broken down into pyruvate in the cytoplasm. This process yields a small amount of ATP and NADH.
- πͺ Transition Reaction:
- π Pyruvate Conversion: Pyruvate is converted into Acetyl-CoA, which enters the Krebs cycle.
- π Krebs Cycle (Citric Acid Cycle):
- π₯ Energy Release: Acetyl-CoA is further broken down, releasing CO\β, ATP, NADH, and FADH\β.
- π’ Electron Transport Chain (ETC) and Oxidative Phosphorylation:
- π ATP Production: NADH and FADH\β donate electrons to the ETC, creating a proton gradient that drives ATP synthase to produce a large amount of ATP. Oxygen (O\β) acts as the final electron acceptor, forming water (H\βO).
π The Connection: A Cycle of Life
Photosynthesis and cellular respiration are complementary processes. Photosynthesis uses sunlight, water, and carbon dioxide to produce glucose and oxygen. Cellular respiration uses glucose and oxygen to produce energy (ATP), water, and carbon dioxide. The products of one process are the reactants of the other, forming a vital cycle for life on Earth.
π Comparing Photosynthesis and Cellular Respiration:
| Feature |
Photosynthesis |
Cellular Respiration |
| Location |
Chloroplasts |
Mitochondria (Eukaryotes), Cytoplasm (Prokaryotes) |
| Reactants |
CO\β, H\βO, Light Energy |
Glucose, O\β |
| Products |
Glucose, O\β |
CO\β, H\βO, ATP |
| Purpose |
Energy Storage |
Energy Release |