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Cellular energy lecture for Bio 105

4 pages106 viewsSpring 2013

BIOL - Biology
Course Code
BIOL 105
Gregory Zagursky

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Biology 105- Cellular Energy
Basic mechanisms of energy release and storage
Cells tap energy from electrons “falling” from organic fuels to oxygen
Glucose gives up energy as it is oxidized (loses electrons)-electrons lose potential
Electrons fall down energy gradient
Dehydrogenase removes electron (in hydrogen atoms) from glucose molecules
And transfers them to NAD+ (reduction)
NADH passes electrons to an electron transport chain
As electrons “fall” from carrier to carrier and finally to O2
Energy is released in small quantities
Cellular Energy
1) All organisms use ATP to do cellular work
2) All organisms use some form of cellular respiration to produce ATP
3) All organisms start with glucose and break it down in series of enzyme
controlled steps
Some of the energy released is captured to make ATP; the rest is lost as heat
In an explosion, O2 is reduced in one step
4) An electron transport chain (ETC) allows for the gradual, controlled release
of energy, not present in all organisms
5) The maximum amount of ATP will be produced when all of the electrons
from glucose pass through an ETC and oxygen is present to accept them
Only occurs in organisms that have aerobic cellular respiration
Must have mitochondria
Stages of cellular respiration and fermentation
Aerobic cellular respiration occurs in three main stages
Cellular respiration oxidizes sugar and produces ATP in three main stages
Glycolysis occurs in the cytoplasm (all cells)
The citric acid cycle (Krebs’s cycle) and the oxidative phosphorylation (via the
electron transport chain) occur in the mitochondria
I. Glycolysis harvest chemical energy by oxidizing glucose to pyruvate
Net 2 ATP gained
Two 3-carbon molecules 2 electrons
Glycolysis produces ATP by substrate level phosphorylation
In which a phosphate group is transferred from an organic molecule to ADP
Two pathways to process the output from glycolysis
1)if oxygen and mitochondria are present, aerobic respiration
2) if oxygen and/or mitochondria are absent, anaerobic respiration
II Aerobic Respiration
Occurs in most cells
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