An Overview of Cellular Respiration
Cellular respiration occurs at the mitochondria:
Parts of the Mitochondria
• Outer Membrane: contains many pore proteins to allow
materials in and out of the mitochondria.
• Inner Membrane: contains enzymes essential for cell
respiration.
• Cristae: the folded sections of the inner
membrane.
• Inner membrane is about 5 times larger
than the outer membrane (increases
surface area and rate of respiration)
• The inner membrane must be folded to fit
inside
An Overview of Cellular Respiration
• Intermembrane Space:
space between the inner
and outer membrane of
the mitochondria.
• Matrix: the area inside of
the inner membrane.
• Contains proteins,
cytosol, and
mitochondrial DNA.
An Overview of Cellular Respiration
• Cellular respiration happens slowly and in many steps.
• If all the energy was released in one step . . . Most
would be lost as light and heat.
• Three steps of
cellular respiration
1. Glycolysis
2. Krebs Cycle
3. Electron
Transport
Chain
Oxygen and Energy
• Glycolysis is an ANAEROBIC
processes. It does not directly
require oxygen, nor does it rely on
an oxygen-requiring process to run.
• Glycolysis is still considered part of
cellular respiration.
• Glycolysis takes place in the
cytoplasm of a cell.
Oxygen and Energy
• Pathways of cellular respiration
that require oxygen are called
AEROBIC.
• The Krebs cycle and electron
transport chain are both aerobic
processes.
• Both processes take place inside
the mitochondria.
Overview of Cellular Respiration
NADH
High-energy electrons
carried by NADH
NADH
FADH2
and
Stage 1
Stage 3
Stage 2
OXIDATIVE
PHOSPHORYLATION
(Electron Transport
and Chemiosmosis)
GLYCOLYSIS
Glucose
CITRIC ACID CYCLE
Pyruvate
Krebs
Mitochondrion
Cytoplasm
ATP
Substrate-level phosphorylation
CO2
CO2
ATP
ATP
Substrate-level phosphorylation
Oxidative phosphorylation
Step 1: Glycolysis
• Location: In the cytosol just
outside the mitochondria
• Purpose: Splits glucose into two
molecules of pyruvic acid.
• To begin glycolysis the cell needs
to invest two ATP
• Glycolysis produces 4 ATP and 2
NADH
(NADH is similar to NADPH in
photosynthesis)
Glycolysis
________
↓
GLUCOSE
___________
→
→
↓
2 PYRUVIC ACID
_____________
ATP
ATP
ATP
ATP
NADH
____________________ + _______________
Put in 2 ATP and get back 4 ATP
Net gain of 2 ATP and 2 NADH
NADH
Step 2: Krebs Cycle
• Location: The mitochondrial matrix
• Pyruvic acid from glycolysis enters the
mitochondria.
• Purpose: To break down the pyruvic acid
into CO2.
• Every turn of the Krebs Cycle produces:
•
•
•
•
3 CO2
1 ATP
1 FADH2 (similar to NADH)
4 NADH
The Krebs Cycle
•Pyruvic acid from
glycolysis enters the
matrix, the
innermost
compartment of the
mitochondrion.
The Krebs Cycle
• During the Krebs cycle, the 2nd stage
of cellular respiration, pyruvic acid
produced in glycolysis is broken
down into carbon dioxide in a series
of energy-extracting reactions.
• The Krebs Cycle is also known as the
Citric Acid Cycle because citric acid is
the first compound formed in this
series of reactions.
Citric Acid Cycle An Overview (3:17)
KREBS CYCLE
KREBS CYCLE
PRODUCES
3
____
1
____
1
____
4
____
Krebs Cycle Animation
The Krebs Cycle
• Energy released by the breaking and
rearranging of carbon bonds is
captured in the forms of ATP, NADH,
and FADH2.
• For each turn of the cycle, 1 ADP
molecule is converted into ATP.
• ATP can directly power the cell’s activities.
• NADH and FADH2 are used in the
electron transport chain to generate
ATP.
Energy Extraction
• Remember! Each molecule of glucose
results in 2 molecules of pyruvic acid,
which enter the Krebs cycle. So each
molecule of glucose results in 2
complete “turns” of the Krebs cycle.
• Therefore, for each glucose
molecule, 6 CO2 molecules, 2 ATP
molecules, 8 NADH molecules,
and 2 FADH2 molecules are
produced.
Step 2: Krebs Cycle
What happens to the products of the Krebs cycle?
Carbon dioxide is lost to the atmosphere
ATP can be used directly to supply energy for the
cell
High energy electron carriers move to the
electron transport chain.