Transcript unit iii – cellular energy

UNIT III – CELLULAR
ENERGY
Big Campbell ~
Ch 9, 10
I. ♪ ♫ THE CYCLE OF LIFE ♪ ♫
II. ENERGY IN THE CELL
• Catabolic Pathway
o Breakdown of molecules that releases stored energy;
exergonic rxn
o _____________________ – partial breakdown of sugars w/o O2
o ___________________________ – breakdown of sugars w/ O2
o Similar to a car burning gasoline
o Although much energy is lost as heat, some can be used to
generate ATP by phosphorylating ADP
• Oxidation-Reduction Reactions (Redox)
o Energy produced in catabolism comes from transfer of eo Movement of e- releases chemical energy of molecule
o Released energy is used to attach Pi to ADP to form ATP
o 1 molecule loses an e- and a 2nd molecule gains an e-
II. ENERGY IN THE CELL, cont
• Oxidation-Reduction Reactions, cont
o
o
o
o
o
_________________ – 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:
II. ENERGY IN THE CELL, cont
• Importance of Electron Carriers
o 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 _________________
o Electron carriers are coenzymes
o “Carry” ______ electrons in the form of H-atoms
o Only 1 proton & 2 electrons are delivered
o One H+ is released into the surrounding solution
o Allow for max energy transfer, minimum energy loss
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
Yields about ____ ATP
 __________
 e- acceptor in light
reaction of photosynthesis
 Not used in cellular
respiration
II. ENERGY IN THE CELL, cont
• A Closer Look at Electron
Carrier Function in Cellular
Respiration
 Reduction of NAD+
o ___________________ oxidizes
substrate by removing 2 Hatoms
o NAD+ is reduced, creating
NADH + H+
o NADH shuttles electrons to
__________________________
_________________________.
Electrons “fall” down to
_______________ in a series of
steps, each releasing energy in
small amounts.
III. CELLULAR RESPIRATION OVERVIEW
III. CELLULAR RESPIRATION OVERVIEW, cont’d
• 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
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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
IV. GLYCOLYSIS, cont
Energy Pay-Off Phase
IV. GLYCOLYSIS, cont
• Summary of Glycolysis
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
o “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
V. OXIDATIVE RESPIRATION, cont
Grooming Step
V. OXIDATIVE RESPIRATION, cont
• In the citric acid cycle
(AKA…Krebs 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!
V. OXIDATIVE RESPIRATION, cont
V. OXIDATIVE RESPIRATION, cont
• Electron Transport –
Oxidative Phosphorylation
o Traditionally called Electron
Transport, now more
commonly called ________
________________________.
o Occurs in inner
mitochondrial membrane
 Membrane organized into
cristae to ________________
__________________________
o Two components to
Oxidative Phosphorylation
 _________________________
 _________________________
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
V. OXIDATIVE RESPIRATION, cont
• Chemiosmosis
 Enzyme complexes known as
_________________ located
in inner mitochondrial
membrane
 H+ electrochemical gradient
provides 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
V. OXIDATIVE RESPIRATION, cont
• A summary of electron
transport . . .
VI. CELLULAR RESPIRATION – A SUMMARY
• Total ATP Gain in Cellular Respiration =
___ (glycolysis) + ____ (citric acid cycle) + ____ (oxidative phosphorylation) = _____ ATP / glucose
VII. CELLULAR RESPIRATION & OTHER
FOOD MOLECULES
VIII. METABOLIC POISONS
• Blockage of Electron Transport Chain
• Inhibition of ATP Synthase
• “Uncouplers”
o Prevent creation of H+ ion gradients due to leakiness
of mitochondrial membrane
VIII. METABOLIC POISONS, cont
IX. FERMENTATION
• Anaerobic pathway
• Occurs in cytosol
• Purpose
o In glycolysis, glucose is oxidized to 2 pyruvate, 2 NAD+ are
reduced to 2 NADH, and there is a net gain of 2 ATP
o In oxidative respiration, NADH is oxidized back to NAD+ in
electron transport chain
o If oxygen is not present, another mechanism must be
available to regenerate NAD+ or glycolysis cannot continue
o In fermentation, pyruvate is reduced thereby oxidizing
NADH to NAD+
o Allows glycolysis and net gain of 2 ATP per glucose to
continue
IX. FERMENTATION, cont
IX. FERMENTATION, cont