Definition
ATP (adenosine triphosphate) releases usable energy when the bond to its last phosphate group is broken, becoming ADP. Cells constantly convert ADP back to ATP using energy from respiration, so it can be spent again — this is why ATP is called the cell's energy currency.
Word equation: carbon dioxide water glucose oxygen
Definition
Light (dependent) reactions: occur in the thylakoid membranes of the chloroplast; chlorophyll absorbs light (mainly red and blue wavelengths), water is split to release oxygen, and energy is captured as ATP.
Dark reactions (Calvin cycle): occur in the stroma of the chloroplast; use that ATP to fix carbon dioxide into glucose — don't directly need light, but depend on the ATP the light reactions supply.
Aerobic: glucose oxygen carbon dioxide water energy (ATP)
Rule
Aerobic respiration (with oxygen) releases far more ATP per glucose molecule than anaerobic respiration (without oxygen) — oxygen allows glucose to be broken down far more completely.
Example 1 — anaerobic respiration in muscles vs. yeast
What are the end products of anaerobic respiration in (a) animal muscle cells, (b) yeast?
- Animal muscle, short of oxygen during intense exercise, produces lactic acid.
- Yeast (fermentation) produces ethanol and carbon dioxide.
Answer: (a) lactic acid; (b) ethanol + CO
Remember
Anaerobic respiration nets only ATP per glucose molecule, far less than aerobic respiration — this is why muscles fatigue quickly when working anaerobically during intense exercise.
Rule
Photosynthesis stores energy (builds glucose, releases oxygen); respiration releases energy (breaks down glucose, uses oxygen) — each process is essentially the reverse of the other.
Quick Recap
- ●ATP ADP: the cell's rechargeable energy currency
- ●Photosynthesis: CO+water glucose+O, light reactions (thylakoid, makes ATP+O) then dark reactions (stroma, builds glucose)
- ●Aerobic respiration: glucose+O CO+water+lots of ATP
- ●Anaerobic: much less ATP; lactic acid (muscle) or ethanol+CO (yeast)
- ●Photosynthesis stores energy; respiration releases it — near-opposite processes
