cellular respiration
the process by which cells release the energy stored within organic molecules and use this energy to synthesize ATP molecules
cellular respiration is an aerobic process
meaning it requires oxygen and releases carbon dioxide
Pathways of Cellular Respiration
allow the energy within a glucose molecule to be released slowly for ATP synthesis
step-by-step breakdown of glucose to CO2 and H2O
produces a maximum yield of 36-38 ATP molecules
cellular respiration pathways
allow the energy within a glucose molecule to be released slowly so the ATP can be produced gradually
NAD+
a coenzyme used in oxidation-reduction reactions
When a metabolite is oxidized,
NAD+ accepts 2 electrons plus a hydrogen ion and NADH results
When NADH passes on electrons,
NAD+ results
FAD
a coenzyme of oxidation reduction
FAD accepts two electrons and two hydrogen ions
FADH2 results
Cellular respiration involves four phases
...
First phase
glycolysis is the breakdown of glucose to 2 molecules of pyruvate
Second phase
During the preparatory reaction, pyruvate is oxidized to a C2 acetyl group carried by CoA and CO2 is removed
Third phase
Krebs/Citric Acid cycle: For glucose, cycle repeats 2x, breakdown of pyruvic which results in carbon dioxide and releases 2 ATPs in this stage
Fourth phase
Membrane bound carriers that transport electrons, produces 32 ATP's
If oxygen is not available to the cell,
fermentation occurs in cytoplasm instead of continued aerobic cellular respiration
Glycolysis
the initial stage of cellular respiration
For each molecule of glucose,
the inputs are 2 ATPs and 2NAD+
The outputs are
2 molecules of pyruvate, 2 NADHs, 2 ADPs and 4 ATPS. There's a net gain of 2 ATPs
complete breakdown of glucose requires
an input of oxygen to keep the electron transport chain working
When FADH2 gives up its electrons to the chain,
it becomes FAD and releases H+ ions
If oxygen is limited,
pyruvate molecules accumulate in the cell and intermediates such as NAD+ and FAD, cannot be recycled
Two basic forms of fermentation
lactic acid and alcohol fermentation
lactic acid fermentation
A series of anaerobic chemical reactions using pyruvic acid that supplies energy when oxygen is scarce
alcholic fermentation
pyruvate is reduced to produce alcohol. NAD+ are regenerated and releases small amounts of CO2
Cristae
structure of a mitochondrion includes folds of an inner membrane
Preparatory (prep) reaction
it produces the molecule that can enter the citric acid cycle
Citric Acid Cycle (Krebs Cycle)
- 2 Pyruvates enter the mitochondrion
- releases 2 ATP, 6NADH, and 2 FADH2 for each glucose
electron transport chain
a series of electron proteins carriers that pass electrons from one to the other
When NADH gives up its electron to the chain,
it releases H+ ions and becomes NAD+