CELLULAR
RESPIRATION
Campbell Chapter 9
Raven & Johnson Chapter 7
From
hamburger
to energy…
how does it
happen??
CELL RESPIRATION BASICS
C 6H 12O 6 + 6O 2 6CO 2 + 6H 2O + Energy
Exergonic (-686 kcal/mol)
OXIDATION & REDUCTION
REACTIONS (RXN)
Oxidation/Reduction Rxn = Redox Rxn
LEO says GER
Xe - + Y -> X + Ye X is e- donor
›X is oxidized
›Known as reducing agent (it reduces Y)
Y is e- acceptor
›Y is reduced
›Known as oxidizing agent (it oxidizes X)
OXIDATION & REDUCTION
REACTIONS (RXN)
Oxygen – extremely electronegative –
strong pull on electrons – great oxidizing
agent
RESPIRATION &
ELECTRONS
Reduction
C 6H 12O 6 + 6O 2 6CO 2 + 6H 2O
Oxidation
OH…WOW…
OK…HERE WE GO!!
 Cell respiration has three major steps
1. Glycolysis
2. Krebs cycle
3. Electron transport chain & oxidative
phosphorylation
OK…HERE WE GO!!
 Glycolysis – in cytosol – breaks glucose into
two molecules of pyruvate
 Krebs cycle – in mitochondrial matrix –
decomposes a derivative of pyruvate to CO 2
 Oxidative phosphorylation – inner membrane
of mitochondria - ATP synthesis due to energy
released by electron transport chain (90% of
energy made this way)
OK…HERE WE GO!!
Some energy made by substrate-level
phosphorylation
Enzyme transfers P
from substrate
directly to ADP
A CLOSER LOOK GLYCOLYSIS
Glucose split into two 3-carbon rings
Each is oxidized & rearranged to make
pyruvate
Ten steps, each controlled by enzymes
First 5 steps – ATP is used to phosphorylate
the fuel molecules
A CLOSER LOOK GLYCOLYSIS
Step 3 – enzyme is phosphofructokinase
(involved in regulation)
Turns off glycolysis when enough ATP is
made
A CLOSER LOOK GLYCOLYSIS
Second 5 steps – 4 ATP are made by
substrate-level phosphorylation, NAD+
reduced to NADH
End result – 4 ATP (2 net), 2 NADH, 2
pyruvate (why??)
Occurs with or without oxygen
LET’S ANIMATE THIS
DO IT AGAIN!!!!
A CLOSER LOOK GLYCOLYSIS
FIRST FIVE STEPS
(KNOW 1 & 3)
SECOND FIVE STEPS
(KNOW #10)
A CLOSER LOOK –
TRANSITION
 If molecular oxygen is around, pyruvate
enters mitochondria
 Pyruvate first modified by enzymes to
become acetyl coenzyme A (acetyl CoA)
 Acteyl CoA is now ready for the Krebs
cycle
TAKE A LOOK AT THE EXCITEMENT!!!!!!
A CLOSER LOOK TRANSITION
A CLOSER LOOK –
KREBS CYCLE
Hans Krebs – 1930s
Occurs in mitochondrial matrix
Eight steps, enzyme controlled
Begins when acetate combines with
oxaloacetate to form citrate
A CLOSER LOOK –
KREBS CYCLE
 Ultimately, the oxaloacetate is recycled
for the next turn of the cycle
 Each cycle produces one ATP by substratelevel phosphorylation, three NADH, and
one FADH 2 (another electron acceptor) per
acetyl CoA
›Remember – the cycle turns two times!!
TIME TO ANIMATE!
One More Time!!!!!
QUICK REVIEW
So far we have made…
2 FADH 2
10 NADH (6 here, 2 in glycolysis, 2 during
transition)
4 ADP  4 ATP by SLP (substrate-level
phosphorylation) (net of 2 in glycolysis, 2 in
Krebs cycle)
6 CO 2 (2 in transition, 4 in Krebs)
A CLOSER LOOK -ELECTRON
TRANSPORT CHAIN
Collection of molecules (proteins)
embedded in inner membrane of
mitochondria (cristae)
They alternate between reduced &
oxidized states as they accept &
donate electrons
A CLOSER LOOK ELECTRON TRANSPORT CHAIN
As electrons move down the chain,
there is a drop in free energy
Basically, e -, H +, O 2 go in and ATP and
H 2O go out
First, NADH transfers electrons to
first molecule of ETC - it is reduced
A CLOSER LOOK ELECTRON TRANSPORT CHAIN
Next, FMN is oxidized as
it gives electron to
Fe•S
Many electron carriers
are cytochromes
Heme prosthetic group
(iron, like in blood)
A CLOSER LOOK ELECTRON TRANSPORT CHAIN
Last cytochrome passes electrons to
oxygen, which also picks up H 2 from
aqueous solution to form water
FADH 2 adds electrons to chain at lower
point
End result – energy to make ATP is
being released a little at a time
FROM ENERGY TO ATP
Inner membrane of mitochondria – ATP
synthase
Uses energy of existing proton
(hydrogen ion) gradient to power ATP
synthesis
Protons came from NADH & FADH 2
being oxidized
More H+ outside than inside matrix
FROM ENERGY TO ATP
ETC uses energy from electron flow to
pump H + out of the matrix
As the H + leak back in, they pass
through the ATP synthase, which drives
the oxidative phosphorylation of ADP
The H+ gradient couples the redox
reactions of ETC to ATP synthesis (called
chemiosmosis)
MAKING ATP
ATP Synthase:
Rotor – spins clockwise
when H+ flows through
Rod connects rotor &
knob – spins, activating
catalytic sites on the
knob
MAKING ATP
›Knob contains
catalytic
sites that change
shape
when rod is turned –
join ADP & P to
make ATP
ANIMATION TIME!
DO IT AGAIN!!
A QUICK REVIEW
Chemiosmosis is an energy-coupling
mechanism that uses energy stored
in the form of an H + gradient across
a membrane to drive cellular work
Energy – comes from exergonic
redox reactions (glycolysis, krebs,
mostly ETC)
Cellular work – synthesis of ATP
OVERALL REVIEW
For every NADH oxidized, you get 3
ATP
FADH 2  2 ATP
So…..
OVERALL REVIEW
Glycolysis – 2 ATP by SLP, 2 NADH
Transition – 2 NADH
Krebs – 2 ATP by SLP, 6 NADH, 2 FADH 2
So…
 10 NADH = 30 ATP
2 FADH 2 = 4 ATP
SLP = 4 ATP
Animation of whole process
CELL
RESPIRATION
– NINJA
STYLE
FERMENTATION
(NO OXYGEN)
Review:
Glycolysis oxidizes glucose to 2
pyruvate
Oxidizing agent is NAD +, not O 2
Happens in aerobic & anaerobic
conditions
FERMENTATION
(NO OXYGEN)
ATP generated by SLP in glycolysis
Must have enough NAD + (must be
recycled to keep up the supply)
With oxygen, NAD+ comes from
NADH by transferring electrons to
the ETC
Without oxygen, electrons are
transferred from NADH to pyruvate
FERMENTATION
 Two types:
1. Alcohol fermentation
 Pyruvate  ethanol
 First, CO 2 released from pyruvate
– makes acetaldehyde
 Then acetaldehyde reduced by
NADH to ethanol
 Recycles supply of NAD+
 Yeast (baking, brewing) &
bacteria
FERMENTATION
2. Lactic acid fermentation
 Pyruvate reduced by NADH to
make lactate (lactic acid) – no
release of CO 2
 Fungi & bacteria for cheese &
yogurt
 Human muscle cells
LAST BITS OF INFO
Facultative anaerobes – yeast &
bacteria who can make enough ATP
to survive from fermentation or
respiration
Respiration can occur with
carbohydrates, proteins, or fats –
they just have to be prepared for the
process
LAST BITS OF INFO
Not everything is about making ATP –
food is broken down and taken to make
other molecules (amino acids, sugars,
fats) as we need them
Feedback mechanisms help to regulate
based on controlling enzyme activity