UNIT III CELLULAR ENERGY
Big Campbell ~ Ch 9, 10 1 I. THE CYCLE OF LIFE 2 II. ENERGY IN THE
CELL Catabolic Pathway
Breakdown of molecules that releases stored energy; exergonic rxn
_____________________ partial breakdown of sugars w/o O2
___________________________ breakdown of sugars w/ O2 Similar to a
car burning gasoline Although much energy is lost as heat, some can
be used to generate ATP by phosphorylating ADP Oxidation-Reduction
Reactions (Redox) Energy produced in catabolism comes from transfer
of e- Movement of e- releases chemical energy of molecule Released
energy is used to attach Pi to ADP to form ATP 1 molecule loses an
e- and a 2nd molecule gains an e- 3 II. ENERGY IN THE CELL,
cont
Oxidation-Reduction Reactions, cont _________________ Loss of e-
_________________ Gain of e- _________________ agent- e- donor
_________________ agent- e- acceptor Sometimes there is a complete
transfer of e- and other times there is a change in the degree of
e- sharing in covalent bonds Inorganic Example: Na + Cl Na+ + Cl-
Organic Example: 4 II. ENERGY IN THE CELL, cont
Importance of Electron Carriers Energy contained in molecules (ex:
glucose) must be released in a series of steps Electrons are
released as hydrogen atoms with corresponding proton (hydrogen's
are clipped off) Hydrogen atoms are passed to an _________________
Electron carriers are coenzymes Carry ______ electrons in the form
of H-atoms Only 1 proton & 2 electrons are delivered One H+ is
released into the surrounding solution Allow for max energy
transfer, minimum energy loss 5 II. ENERGY IN THE CELL, cont
Electron Carriers (oxidative states) _________ e- acceptor in
cellular respiration Becomes NADH when reduced Yields about ____
ATP __________ e- acceptor in Krebs Cycle / TCA Cycle / Citric Acid
Cycle e- acceptor in light reaction of photosynthesis Not used in
cellular respiration 6 II. ENERGY IN THE CELL, cont
A Closer Look at Electron Carrier Function in Cellular Respiration
Reduction of NAD+ ___________________ oxidizes substrate by
removing 2 H-atoms NAD+ is reduced, creating NADH + H+ NADH
shuttles electrons to
___________________________________________________.Electrons fall
down to _______________ in a series of steps, each releasing energy
in small amounts. 7 III. CELLULAR RESPIRATION OVERVIEW
8 III. CELLULAR RESPIRATION OVERVIEW, contd
Cellular process to convert chemical energy in ___________ (and
other molecules) into ________ Primarily takes place in
___________________ of eukaryotic cells Overall Reaction
____________________________________________________ Steps in
Cellular Respiration Glycolysis occurs in cytosol Splitting of
sugar Initial breakdown of glucose to pyruvate, some ATP Citric
Acid Cycle occurs in mitochondria Completes oxidation of glucose to
CO2 Produces ATP, but more importantly provides high-energy
electrons for ETC Electron Transport Chain occurs in mitochondria
Oxidative Phosphorylation Highest ATP yield; uses energy released
from downhill flow of e- to generate ATP Citric Acid Cycle +
Electron Transport Chain = Oxidative Respiration 9 IV. GLYCOLYSIS
10 steps Occurs in cytosol of cell
Does not require oxygen 1st part of pathway is energy investment
phase (5 steps) 2nd part of pathway is energy pay-off phase (5
steps) Energy Investment Phase 10 IV.GLYCOLYSIS, cont Energy
Pay-Off Phase 11 IV.GLYCOLYSIS, cont Summary of Glycolysis 12 V.
OXIDATIVE RESPIRATION
2 pyruvates formed from glycolysis still contain a tremendous
amount of chemical energy If oxygen is available, pyruvate enters
mitochondrion for citric acid cycle and further oxidation Upon
entering mitochondrion but prior to entering citric acid cycle
Grooming Step Carboxyl group of pyruvate is removed, given off as
CO2 Remaining 2-C molecule is oxidized to acetate NAD+ reduced to
NADH + H+ Acetate binds to molecule known as Coenzyme A to form
acetyl CoA 13 V. OXIDATIVE RESPIRATION, cont
Grooming Step 14 V. OXIDATIVE RESPIRATION, cont
In the citric acid cycle (AKAKrebs cycle or TCA Cycle), 2 3-carbon
molecules go through a series of redox rxns. Occurs in
mitochondrial matrix Produces NADH, FADH2, ATP, and CO2. CoA is not
actually a part of the reaction it is recycled remember, it is an
enzyme! 15 V. OXIDATIVE RESPIRATION, cont
16 V. OXIDATIVE RESPIRATION, cont
Electron Transport Oxidative Phosphorylation Traditionally called
Electron Transport, now more commonly called ________
________________________. Occurs in inner mitochondrial membrane
Membrane organized into cristae to ________________
__________________________ Two components to Oxidative
Phosphorylation _________________________ 17 V. OXIDATIVE
RESPIRATION, cont
Electron Transport Chain Collection of molecules, each more
electronegative than the one before it Molecules are reduced, then
oxidized as electrons are passed down the chain __________ is
ultimate electron acceptor Purpose is to establish H+ gradient on
two sides of inner mitochondrial membrane Energy from falling
electrons used to pump H+ from matrix into intermembrane space 18
V. OXIDATIVE RESPIRATION, cont
Chemiosmosis Enzyme complexes known as _________________ located in
inner mitochondrial membrane H+ electrochemical gradientprovides
energy Known as _________________ Movement of H+ions through
membrane rotates enzyme complex Rotation exposes active sites in
complex ATP is produced from ADP and Pi 19 V. OXIDATIVE
RESPIRATION, cont
A summary of electron transport . . . 20 VI. CELLULAR RESPIRATION A
SUMMARY
Total ATP Gain in Cellular Respiration = ___ (glycolysis) + ____
(citric acid cycle) + ____ (oxidative phosphorylation) = _____ ATP
/ glucose 21 VII. CELLULAR RESPIRATION & OTHER FOOD
MOLECULES
22 VIII. METABOLIC POISONS
Blockage of Electron Transport Chain Inhibition of ATP Synthase
Uncouplers Prevent creation of H+ ion gradients due to leakiness of
mitochondrial membrane 23 VIII. METABOLIC POISONS, cont
24 IX. FERMENTATION Anaerobic pathway Occurs in cytosol
Purpose
In glycolysis, glucose is oxidized to 2 pyruvate, 2 NAD+ are
reduced to 2 NADH, and there is a net gain of 2 ATP In oxidative
respiration, NADH is oxidized back to NAD+ in electron transport
chain If oxygen is not present, another mechanism must be available
to regenerate NAD+ or glycolysis cannot continue In fermentation,
pyruvate is reduced thereby oxidizing NADH to NAD+ Allows
glycolysis and net gain of 2 ATP per glucose to continue 25
IX.FERMENTATION, cont 26 IX.FERMENTATION, cont 27
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