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# System prepended metadata

title: Cellular energetics

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# Cellular energetics

## Breaking down glucose

Animals and plants.

### Glycolysis

Inputs:
  * 1 glucose
  * 2 ADP 
  * 2 NAD+
  * 2 phosphates

Outputs:
  * 2 pyruvate
  * 2 NADH
  * 2 ATP
  * 2 water

### Fermentation

We have to convert NADH into NAD+, preventing glycolysis.

Animals: lactic acid reduction
Plants/fungi: ethanol/carbon dioxide

### Link reaction

Input: pyruvate, CoA, NAD+, water
Output: A-CoA, carbon dioxide, NADH

### TCA, Krebbs

Inputs: A-CoA, 3 NAD+, FAD, Pi, 1 GDP, 3 oxygen (hence aerobic!)
Output: 2 carbon dioxide, 3 NADH, 1 GTP, 1 FADH2

Oxaloacetate + A-CoA \rightarrow citrate

### Electron transport chain

Pumps protons into the intermembrance space from the matrix of the mitochondrion

Concentration gradient (high in IMS, low in matrix), protons will flow back into the matrix through ATP synthase.  ATP synthase spins, taking advantage of the energy from the gradient.

#### ATP synthase

Subunits?

## Photosynthesis

Plants only.

### Acyclic light-dependent reaction

Thylakoid lumen or space: inside
Stroma: outside

Water enters thylakoid space, splits into oxygen, proton, 2 electrons.

Oxygen is a byproduct. We don't care.

Light comes in to chlorophyll, PSII.

Electron moves through electron transport chainand pumps protons IN to the lumen.

Electron reaches PSI.  Another photon is incident to PSI.  Electron leaves through ferrodoxin-NADP reductase to create NADPH from NADP.

Proton is harvested from the stroma, leaving a higher concentration in the lumen.  Protons then flow OUT of the lumen through ATP synthase to make ATP.

### Cyclic reaction

PSII not involved.

Electron moves through PSI and back to the ETC to pump protons.  As a result, no water needed but no NADPH created.

### Light-independent reaction ("dark" reactions)

Occurs in stroma.  Produces glucose.

* RuBP (5C) + carbon dioxide
* Catalyzed by RuBisCo
  * Slow
  * Can trap CO_2
  * Highly conserved
* 3PG
    * Uses ATP and NADPH
    * Converts to G3P
* 2 _excess_ 3PG "becomes glucose"

6 carbons in glucose, must regenerate ribulose bisphosphate

12 ATP + 6 NADPH for 1 glucose

Three phases:
1. Carbon fixation: carbon dioxide bonds to ribulose bisphosphate to make 3PG (catalyzed by RuBisCo)
2. Reduction: 3PG converted to 2 G3P
3. Regeneration: G3P to RuBP by adding a carbon