D.N.A
Objective: Sequence the events of cell respiration, including major reactants and
products of glycolysis, krebs cycle, ETC, and fermentation.
1. ATP serves as a common energy source for organisms because
A. it is the smallest energy molecule
B. it stores the least energy of any energy source
C. its energy can be easily transferred to do cellular work
D. it is extremely stable and can be stored in the cell for long
periods of time
E. traces of it have been found in fossils of ancient organisms
dating back to the beginning of life on Earth
2. Which metabolic process is common to both aerobic cellular
respiration and alcoholic fermentation?
A. Krebs cycle
B. Glycolysis
C. Electron transport chain
D. Conversion of pyruvic acid to acetyl CoA
E. Production of a proton gradient
D.N.A
Objective: Sequence the events of cell respiration, including major
reactants and products of glycolysis, krebs cycle, ETC, and
fermentation.
Which of the following describes glycolysis?
A. It begins the oxidation of glucose
B. It produces a small amount of ATP
C. Generates NADH
D. Splits glucose to form two molecules of pyruvate
E. All of the above
What is the function of O2 in aerobic metabolism
A. Oxidizes glucose, making it more soluble in water
B. Reduces enzymes, limiting glucose synthesis
C. Activates enzymes in the citric acid (Krebs) Cycle
D. Accepts electrons through the electron transport chain
E. Transforms ion gates to allow diffusion of K+
During complete aerobic cellular respiration, each
molecule of glucose broken down in the mitochondria
can yield 36 molecules of ATP. What conditions might
lead to a decrease in the amount of ATP produced in a
given system?
A. An increase in the amount of glucose added to the
system
B. A decrease in the amount of light the system is
exposed to
C. A decrease in the amount of oxygen available in the
system
D. A decrease in the amount of carbon dioxide available
in the system
E. An increase in the amount of ADP in the system
Cellular Respiration Overview
Cellular Respiration
Aerobic Cellular Respiration occurs in the
presence of oxygen in the cytosol and the
mitochondria
The process can be summarized as:
C6H12O6 + 6O2  6CO2 + 6H2O + Energy
(ATP and Heat)
Redox Reaction
Redox Reactions – Reactions involving
the transfer of electrons
Oxidation – When a substance loses
electrons in a redox reaction
– The substance accepting the electron is
known as the oxidizing agent
Reduction – When a substance gains
electrons in a redox reaction
– The substance donating the electron is known
as the reducing agent
Example: Sodium Chloride
Becomes Oxidized (loses electron)
Oxidizing
Agent
Reducing
Agent
Becomes Reduced (gains electron)
Production of ATP
Becomes Oxidized
Oxidizing
Agent
Reducing
Agent
Becomes Reduced
Overview of the Process
With oxygen present, there are 3 main
steps in cellular respiration:
1. Glycolysis
2. The Citric Acid Cycle (Krebs Cycle)
3. Oxidative Phosphorylation: ETC and
chemiosmosis
NADH
NADH and FADH2
Glucose
Glycolysis
ATP
Oxidative
Phosphorylation:
ETC
And
Chemiosmosis
Pyruvate
ATP
ATP
Types of Phosphorylation
Phosphorylation is how ATPs are formed
Oxidative Phosphorylation – Phosphates
added to ADP via the redox reactions in the
ETC
Substrate Level Phosphorylation – An
enzyme transfers a phosphate from a substrate,
to ADP (glycolysis and citric acid cycle)
Glycolysis
Glyco=Sugar; Lysis= Split
In Glycolysis, Glucose is split into two 3-carbon
pyruvate (pyruvic acid) molecules
In order to begin, glycolysis requires the input of
energy (ATP)
Glycolysis occurs in the cytosol
Lets look at Glycolysis in a very simple form:
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 
2 Pyruvate
4 ADP
2ATP
Glucose
C
C
C
C
C
C
C
2 ADP
C
C
C
C
C
2 4ATP
NADH Pyruvic Acid
C
C
C
2 NAD+
C
C
C
Citric Acid Cycle
Also referred to as the Krebs Cycle
Takes place in the mitochondrial matrix
When oxygen is present, the Citric Acid
Cycle follows Glycolysis
This cycle takes pyruvate from glycolysis
to make ATP, NADH, and FADH2
Citric Acid Cycle Simplified
Pyruvate turns into acetyl CoA
Acetyl CoA enters the Citric Acid Cycle
and is then transformed into citrate
Citric Acid Cycle - Products
3 NADH, 1 FADH2, 1ATP, and CO2 are
produced in the Citric Acid Cycle
– Each NADH will generate about 3 ATP
– FADH2 will generate about 2 ATP
The CO2 released from this cycle is the same
CO2 that you exhale while breathing
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 ATP (oxidative
phosphorylation)
Oxidative Phosphorylation
This is the process of extracting ATP form
the energy in NADH and FADH2
Occurs in the cristae of the mitochondria
The electrons are passed through an ETC
to release ATP
The final electron acceptor is oxygen
Oxygen bonds with 2 electrons (carried by
Hydrogen) to produce water
eeADP
ATP
ADP
ATP
ADP
ATP
ADP
ATP
H
H
O
Chemiosmosis
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
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
Anaerobic Environments
When no oxygen is present, the cell will
have to do one of two things:
– Die due to the fact that there is no Oxygen to
accept electrons at the end of oxidative, so no
more NAD+ are made
or
– They can undergo Fermentation:
Lactic Acid
Alcoholic
Fermentation
Takes place in the mitochondrial inner
membrane
Does not require oxygen to occur
Does not directly produce ATP
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