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The principles of Energy Harvesto Cellular respiration and
fermentation are catabolic, energy-yielding pathways
They gain energy by breaking down complex molecules This is
called fermentation
y Degradation of sugars in the absence of oxygen The more
efficient process ifcellular respiration
y Oxygen is consumedy Organic compounds + Oxygen CO2+ water +
energy
This breakdown of glucose if exergonic Cells recycle the ATP
they use for work
y Cells transfer phosphate groups from the ATP to other
molecules inorder to perform work
y The transfer of ATP to ADP, along with the inorganic
Phosphate, is themain process for this.
Redox reactions release energy when electrons move closer to
electronegativeatoms
y These reactions are based upon the transfer of electrons
betweenreactants.
o These are called redox reactionso The reactant that loses
electrons areoxidized, and the one that
gains the electrons are reduced.
Glucose and other organic fuels are broken down graduallyy
Hydrogen atoms are stripped from their glucosey Not transmitted to
Oxygeny They are passed to NAD+ -- oxidizing agent during
respirationy Dehydrogenases remove a pair of hydrogen atoms from
the substratey Since NAD+ gains an Hydrogen, it becomesNADHy The
cell uses the electron transport chain to break the fall of
electrons
to oxygen into several energy-releasing steps instead of just
one.
o The chain consists of many molecules built into the
innermembrane of the mitochondrion
o NADHmoves the electrons to the top of the chain and when
itreaches the bottom, it becomes water.
o Exergonic reactiono Instead of all the energy being released
in one reaction, small
amounts of energy are released between each step.
o Each step of the chain is more electronegative than the
onebefore it.
o Thus, the electrons move down.o This chain moves like this:
food NADH electron transport
chain oxygen.
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Respiration involves Glycolysis, Krebs cycle, and electron
transport.o Glycolysis: happens in the cytosol; breaks the glucose
into pyruvateo Krebs cycle: Within the mitrochondrial matrix;
pyruvates into carbon dioxide;o Dehydrogenases move the electrons
from the subtrates into the NAD+ to NADHo In the third stage of
respiration, the electron transport chain accepts electronso
Oxidative phosphorylation: the release of a little bit of energy in
each step.o Substrate level phosphorylation accounts for a small
part of ATP production.o ATP is formed when a phosphate is
separated from a substrate to an ADP.
In-depth look at each of the cycleso Glycolysis
Is the splitting of sugar Glucose, a six carbon sugar, is split
into two three sugar carbons. After this, the molecules are formed
into pyruvate. This is divided into ten phases:
y The first five goes into the Energy investment phasey Energy
payoff phase goes into the next five stepsy During the investment
phase, ATP goes into the processy The result is 2 ATP and 2 NADPHy
Glycolysis is oxygen independent
o Krebs Cycle Most of the energy is stored within the
pyruvates
ENERGY INVESTMENT PHASE
1. Glucose enters the cell and is phosphorylated by
hexokinase.Phosphorylation makes the glucose more reactive. ATP
transforms
into ADP and turns Glucose into Glucose-6-Phosphate
2. The Glucose-6-phosphate is transformed into fructose same
form.This is aided by phosphoglucoisomerase
3. Using Phosphofructokinase, ATP is transformed into ADP. The
sugaris ready to be split into two.
4. Fructose-1,6biophosphateAldolasethe enzyme cleaves
themolecule into two different three carbon sugars.
5.
