Transcript Cell Respiration SAT II Review

Cellular Respiration
● Cellular Respiration is the process of converting food energy into
ATP energy (i.e. – the controlled release of energy from organic
compounds in cells to form ATP):
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 36 ATP
The Pathway of energy in
living organisms
cellular Chemical
Chemical
Light
photosynthesis
respiration energy for use
energy
stored
energy
in the form of
in glucose,
from the sun
ATP
fats, or
carbohydrates
A Heterotroph Must Convert:
To ATP in order to perform work
(ATP is form of chemical energy that is usable by the cell).
What is Cellular Respiration?
• The process of converting food energy into ATP
energy because organic compounds contain stored
(potential) chemical energy in their bonds (the steps
of cellular respiration can be traced using glucose as
an example )
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 36 ATP
• ATP is a form of chemical energy and cellular
enzymes can easily make use of this energy source
(when that energy is released, cells can use it for
metabolism)
• All living organisms must perform cellular
respiration (plants and animals) to get ATP.
Cell Respiration “Big Picture”
Cellular Respiration – The Big Idea
 Glycolysis is the first step in cellular respiration
 Two types of cellular respiration: Aerobic (uses oxygen)
and anaerobic (without oxygen)
 Two types of anaerobic respiration: Lactic acid
fermentation (humans) and alcoholic fermentation (yeast)
Glycolysis “Big Picture”
Glycolysis “Big Picture” Flower Warm-up
Glycolysis “Big Picture” consists of two major phases
“Big” Overview of Glycolysis
A closer look at the energy investment phase
A closer look at the energy payoff (yielding) phase
The Link Reaction - A Segue To the Mitochondrion
Link Reaction “Big Picture”
Oxidation of Pyruvate /Link Reaction
• When Oxygen is present, the 2 Pyruvates are
translocated to the matrix of the mitochondrion
where they are converted into 2 Acetyl CoA (C2).
• Each Pyruvate releases CO2 (decarboxylation) to
form Acetate.
• The Acetate is oxidized and gives electrons and H+
ions to 2 NAD+ → 2 NADH.
• The Acetate is combined with Coenzyme A to
produce 2 Acetyl CoA molecules.
– Next stop is the Kreb’s cycle
• 2 NADH’s carry electrons and hydrogens to the
Electron Transport Chain.
The Link Rxn
Krebs Cycle “Big Picture”
The Krebs Cycle
• Acetyl-CoA will now contribute its acetate, to the starting
step of the Krebs cycle for further oxidation.
• During this cycle CO2 is released
• Substrates are oxidized give electrons and H+ ions to
NAD+ → NADH.
• For each entering acetate, 3 molecules of NADH are
produced.
• Another electron acceptor is FAD (flavin adenine
dinucleotide) which is reduced to FADH2. This will also
pass on electrons (like NADH) to ETC.
• After all the steps, the same compound (the starting point,
oxaloacetate) is returned, hence a cycle.
The Link Rxn
The Buzz Terminology
Link & Krebs
CoA
Anaerobic
Matrix
C4 + C2 → C6 →C5→C4→C4→
Mitochondria
Phosphorylation
FADH2 SLP
Decarboxylation
NADH
ATP
Oxidation
What Happens to all the Reduced
Coenzymes and Oxygen?
• NADH and FADH2 produced earlier, go to the ETC
• NADH and FADH2 release electrons to carriers/proteins
embedded in the membrane of the cristae.
• NADH and FADH2(less energy) both hand over the
electrons to ETC, but at different levels.
• As the electrons are transferred, H+ ions are pumped from
the matrix to the intermembrane space up the concentration
gradient.
• Electrons are passed along a series of carriers until they are
ultimately donated to an Oxygen molecule.
½ O2 + 2 electrons + 2 H+ (from NADH and FADH2) → H2O.
• The H+ diffuses down its gradient through channels
provided by ATP synthases and the enzyme uses this flow
to drive the oxidative phosphorylation of ADP to ATP
Electron Transport Chain and Oxidative
phosphorylation /ATP synthesis
Cell Respiration “Wrap Up”
The Buzz Terminology
Ox Phos
Oxygen
ETC
Chemiosmosis
Inner Membrane space
Inner Membrane
Phosphorylation
NADH
ATP
FADH2
cristae
ATPase
Proton pump
The account in terms of ATP output
Each NADH will result in ~ 3ATPs (except for cytosol derived products), and
each FADH2 in ~2 ATPs , through ETC and chemiosmosis.
From glycolysis
• 2 ATP (SLP)
• 2 NADH (ox phos)
ATPs
2
6 (4)
From Krebs cycle
• 8 NADH (ox phos)
• 2 FADH2 (ox phos)
• 2 ATP (SLP)
24
4
2
After ETC and Chemiosmosis
38 (36)
Oxidative phosphorylation will stop in the absence of electronegative oxygen
that pulls electrons down the transport chain.
Fermentation Overview
• An extension of glycolysis
• A process in which ATP is produced without the help of
oxygen.
• Without the electronegative oxygen to pull electrons down
the transport chain, oxidative phosphorylation ceases
• ATP generated soley by Substrate level phosporylation
• Sufficient supply of some oxidizing agent is required
(usually, NAD+, which needs to be recycled).
• No ETC since there is no oxygen
• NAD+ gets recycled by use of an organic hydrogen acceptor
forming lactate or ethanol.
• Common in prokaryotes and very useful to humans.
Fermentation Factoids
Two Types of Fermentation
• Alcoholic Fermentation
–
–
–
–
Produces ethyl alcohol and CO2
Yeast/Fungi and some prokaryotes
Used to make wine and beer
CO2 released by yeast as a byproduct causes bread to rise
• Lactic Acid Fermentation
– Produces lactic acid when O2 isn’t available
– Animals and most bacteria
– A build up of lactate in your muscles from over exerting yourself
and not taking in enough oxygen causes muscle fatigue
(i.e.“rubbery feeling”) and leads to some soreness.
Alcohol Fermentation
• Pyruvate is
converted to
ethanol in
two steps.
• Alcohol
fermentation
by yeast is
used in
brewing and
winemaking.
Lactic Acid Fermentation
• Pyruvate is reduced
directly by NADH to
form lactate
• Lactic acid
fermentation by
some fungi and
bacteria is used to
make cheese and
yogurt
• The waste product,
lactate, is
converted back to
pyruvate in the liver.
The metabolism of all macromolecules
is tied to cellular respiration
• Excess intermediates of glycolysis and the Kreb’s cycle can
be converted to stored carbohydrates, fats and proteins.
Pathway for
synthesis of
RNA, DNA
Fats
Glycogen
or starch
Glucose
Phospholipids
Fatty acids
Pruvate
Acetyl
CoA
Lactate
(from fermentation)
Krebs
cycle
Several
intermediaries
used as
substrates in
amino acid
synthesis
A Visual Guide to Cellular
Respiration and Fermentation