Cellular Respiration

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Transcript Cellular Respiration

December 5, 2012
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Cellular Respiration
C6H12O6 + 6 O2 6 CO2 + 6H2O + 38 ATP
Cellular Respiration: An Overview
Process by which cells convert the energy in
food (usually glucose) into usable ATP.

Terms to Know…
 Oxidation

Compound becomes more positive
 Reduction

= the loss of electrons
= the gain of electrons
Compound becomes more negative
and protons (H+) travel TOGETHER
 NAD+ = coenzyme derived from niacin; acts
as a H+ and e- acceptor. AN ENERGY
CARRIER!
 Electrons
Cellular Respiration: An Overview
Substrate-Level Phosphorylation
An enzyme transfers a phosphate group
directly from an organic molecule to ADP
to form ATP
 The ATP produced in Glycolysis & the
Krebs Cycle is produced by this method.

Oxidative Phosphorylation
(ETC + Chemiosmosis)
The production of ATP by using energy
derived from the redox reactions of the
Electron Transport Chain.
 The enzyme ATP synthase is needed to
phosphorylate the ADP to produce ATP.
 Almost 90% of the ATP produced from
cellular respiration is produced this way.

Cellular Respiration
Glucose
Glycolysis
Oxygen Absent
ATP
Oxygen Present
Anaerobic Respiration
Aerobic Respiration
(Fermentation)
(Krebs Cycle & ETC)
ATP
Glycolysis
“glucose-splitting”
 Big Picture:

 Glucose
(6-C) is broken down into 2
molecules of pyruvate (3-C)
Occurs in the cytosol
 Occurs with or without oxygen
 Made up of 2 phases:

 Energy
investment phase
 Energy yielding phase
Glycolysis: Energy Investment
Phase


Glucose is converted
into 2 G3P
(Glyceraldehyde-3phosphate)
Requires 2 ATP
Glycolysis: Energy-Yielding Phase
2
G3P are converted
into 2 Pyruvate (3C)
molecules.
 Dehydrogenase
enzymes remove H
from intermediate
compounds and
attach them to 2 NAD
to produce 2NADH
Net Gain in Glycolysis

2 ATP
- 2 ATP (Energy investment phase)
+ 4 ATP (Energy yielding phase)
+ 2 ATP

2 NADH
 Electron
carriers
 Will be used to make ATP later 
Choices, Choices! 

If oxygen is absent, anaerobic respiration
occurs
 Fermentation
Yeast & some bacteria  alcoholic fermentation
 Animal muscle lactic acid fermentation


If oxygen is present, aerobic respiration
occurs
 Krebs
Cycle and Electron Transport Chain
Cellular Respiration
Glucose
Glycolysis
Oxygen Absent
Anaerobic Respiration
ATP
Oxygen Present
Aerobic Respiration
(Fermentation)
ATP
Fermentation

2 major types:
 Alcoholic

and lactic acid fermentation
NAD+ acts as a hydrogen acceptor during
glycolysis
the supply of NAD+ runs out, then glycolysis
would have to stop.
 Fermentation occurs as simply a means of
recycling the NAD+, so that glycolysis can
occur again.
 If
Alcoholic
Fermentation
 Occurs in some BACTERIA and

YEAST
2 step process:

Carbon dioxide is released from
pyruvate (3-C), forming
acetaldehyde (2-C)
 Acetaldehyde is reduced by
NADH (gains an electron),
forming ethyl alcohol (ethanol)
 NAD+ is regenerated, thereby
allowing glycolysis to continue

Used to produce beer and wine
Lactic Acid Fermentation


Occurs in ANIMALS
1 step process:


Pyruvate is reduced by
NADH (gains an
electron), forming lactic
acid
NAD+ is regenerated,
thereby allowing
glycolysis to continue

Occurs in muscle cells,
causing muscle pain and
fatigue
Cellular Respiration
Glucose
Glycolysis
Oxygen Absent
Anaerobic Respiration
ATP
Oxygen Present
Aerobic Respiration
(Fermentation)
ATP
Aerobic Respiration



After glycolysis, most of
the energy from glucose
remains “locked” in 2
molecules of pyruvate
If oxygen is present, the
pyruvate enters the
mitochondrial matrix to
complete the Krebs Cycle
Pyruvate (3-C) is
converted to Acetyl CoA
(2-C)

CO2 is released as a
waste product
 NADH is produced
The Krebs Cycle

Yield per pyruvate molecule:
4
1
1
2

Yield per glucose molecule (two turns of Krebs
Cycle):
8
2
2
6

NADH
FADH2
ATP
CO2
NADH
FADH2
ATP
CO2
CO2 released as a waste product
Electron Transport Chain
The ETC converts the NADH and FADH2
from glycolysis and the Krebs Cycle into ATP
 Occurs in inner membrane of mitochondrion
 The energy in each NADH molecule moves
enough protons (H+) into the mitochondrial
matrix to create 3 ATP
 1 FADH2  2 ATP

The Electron Transport Chain



The electrons from NADH and FADH2 are
passed from one electron acceptor molecule to
another.
Each electron acceptor is more electronegative
than the last.
Oxygen is the final electron acceptor
eETC
oxygen
Chemiosmosis
Similarly to

photosynthesis, the
energy the electrons lose
along the way moves H+
out of the matrix and into
the intermembrane space
of the mitochondrion

As H+ ions diffuse
through the
membrane, ATP
synthase uses the
energy to join ADP
and a phosphate
group  ATP
Oxidative Phosphorylation: ETC & Chemiosmosis
Aerobic Respiration: Total Energy
Yield

Glycolysis:
2
ATP (Net)
 2 NADH  6 ATP

Krebs Cycle:
2
ATP
 8 NADH  24 ATP (ETC)
 2 FADH2  4 ATP (ETC)

TOTAL:
8
ATP + 30 ATP  38 ATP