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Learning check
Once you have watched the video, check your learning with this quiz.
Why do organisms need carbon and energy?
Carbon
- Build cells and their internal structures
- Example: Cell division
Energy
- Perform energy-consuming reactions
- Examples: Movement, cell division
ATP – The cell’s energy currency
When an ATP molecule is cleaved into ADP + Pi, energy is released.
- The cell uses this energy to perform energy-consuming reactions.
What's an “energy currency”? The ATP cycle.
- The cell “pays” in ATP as soon as an energy-consuming reaction needs to take place.
- The cell “gets paid” in ATP by breaking down e.g. fat and sugar.
When an ATP molecule is cleaved into ADP + Pi, energy is released.
- The cell uses this energy to perform energy-consuming reactions.
What's an “energy currency”? The ATP cycle.
- The cell “pays” in ATP as soon as an energy-consuming reaction needs to take place.
- The cell “gets paid” in ATP by breaking down e.g. fat and sugar.
From where do organisms get their energy?
Chemotrophs
Get energy through cellular respiration
- Oxidation of sugar (glucose)
Cellular respiration
Glucose + oxygen → carbon dioxide + water + energy
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
The energy released is converted into ATP.
Phototrophs
Get energy from sunlight (photosynthesis)
- Synthesize glucose
Photosynthesis
Water + carbon dioxide + energy → glucose + oxygen
6H2O + 6CO2 + hν → C6H12O6 + 6O2
The energy in light (denoted "hν") is used to assimilate carbon dioxide and synthesize glucose.
From where do organisms get their carbon?
Autotrophs
Make their own “food” from CO2.
- Example: photosynthesis
Heterotrophs
Eat other organisms
- Examples: humans, fungi, most bacteria …
Different types of organisms
Organisms may be classified according to their primary energy and carbon sources:
| Autotrophs | Heterotrophs | ||
Type of organism | Photoautotroph | Chemoautotroph | Photoheterotroph | Chemoheterotroph |
Energy source | Light | Inorganic compounds | Light | Organic compounds |
Carbon source | CO2 | CO2 | Organic compounds | Organic compounds |