Transcript Cellular Respiration: Harvesting Chemical Energy

Cellular Respiration:
Harvesting Chemical Energy
Respiration is the process of extracting
stored energy from glucose and storing it in
the high energy bonds of ATP.
Cellular Respiration Equation
Reactants
C6H12O6 + 6 O2
Products
6 CO2 + 6 H2O and energy
• As a result of respiration, energy is released
from the chemical bonds and used for
“phosphorylation” of ATP.
• Phosphorylation is the process of adding a
phosphate group to a molecule…. By adding a
phosphate ADP it becomes ATP.
• The respiration reactions are controlled by
ENZYMES.
Cellular Respiration
• There are two types of Respiration:
Anaerobic Respiration and Aerobic
Respiration
• Some organisms use the Anaerobic
Respiration pathway, and some
organisms use the Aerobic
Respiration pathway.
Anaerobes
• Anaerobes are organisms that
use the Anaerobic Respiration
pathway
• Most anaerobes are bacteria
(not all).
• Anaerobes do NOT require
oxygen.
Aerobes
• Aerobes are organisms that
use the Aerobic Respiration
pathway.
• Aerobes require oxygen.
Anaerobic Respiration
Anaerobic Respiration does
NOT require oxygen!
The 2 most common forms of
Anaerobic Respiration are:
1. Alcoholic Fermentation, and
2. Lactic Acid Fermentation
The First Stage of
Respiration for ALL living
organisms, anaerobes or
aerobes,
is called Glycolysis
and takes place in the
Cytosol.
Glycolysis
• glyco means “glucose/sugar”, and
• lysis means “to split”. Therefore,
• glycolysis means “to split glucose”
• This process was likely used to
supply energy for the ancient
forms of bacteria.
Glycolysis
• Function - to split glucose and
produce NADH, ATP and Pyruvate
(pyruvic acid).
• Location - Cytosol
• Occurs in 9 steps- 6 of the steps
use magnesium (Mg) as a
cofactor.
Glycolysis
4 ATP’s are
produced
Pyruvic Acid (3 Carbons)
Glucose
(6 carbons)
2 ATP’s supply
the activation
energy
2 NAD+ + 2 e-
Pyruvic Acid (3 Carbons)
2 NADH
4 ATP Yield = 2 ATP Net Gain
Products of Glycolysis
• 2 Pyruvic Acids (a 3C acid)
• 4 ATP
• 2 NADH
Alcoholic Fermentation
is carried out by yeast,
a kind of fungus.
Alcoholic Fermentation
• Uses only Glycolysis.
• Does NOT require O2
• Produces ATP when O2 is
not available.
Alcoholic Fermentation
(Ethyl Alcohol
or Ethanol)
C6H12O6
2 C2H5OH + 2 CO2
As a result of Alcoholic
Fermentation,
Glucose is converted into 2
molecules of Ethyl Alcohol and 2
Molecules of Carbon Dioxide.
Alcoholic Fermentation
Glycolysis
Released into the environment
4 ATP’s are
produced
CO2
(C2H5OH)
Ethyl Alcohol (2C)
Pyruvic Acid (3C)
Released into the environment
Glucose
(6 carbons)
2 ATP’s supply the
activation energy
2 NAD+ + 2 e-
CO2
Pyruvic Acid (3C)
2 NADH
Ethyl Alcohol (2C)
(C2H5OH)
2 NAD+ + 2 e-
4 ATP Yield = 2 ATP Net Gain
Question
• Why is the alcohol content of wine
always around 12-14%?
• Because Alcohol is toxic and kills the
yeast at high concentrations.
Oh Yeah…..The Holes in Swiss
Cheese are bubbles of CO2 from
fermentation.
Importance of Fermentation
• Alcohol Industry - almost every
society has a fermented
beverage.
• Baking Industry - many breads
use yeast to provide bubbles to
raise the dough.
Lactic Acid Fermentation
• Uses only Glycolysis.
• Does NOT require O2
• Produces ATP when O2 is
not available.
Lactic Acid Fermentation
• Carried out by human muscle
cells under oxygen debt.
• Lactic Acid is a toxin and
causes fatigue, soreness and
stiffness in muscles.
Lactic Acid Fermentation
Glycolysis
4 ATP’s are
produced
Pyruvic Acid (3C)
Lactic Acid (3C)
Pyruvic Acid (3C)
Lactic Acid (3C)
Glucose
(6 carbons)
2 ATP’s supply the
activation energy
2 NAD+ + 2 e-
2 NADH
2 NAD+ + 2 e-
4 ATP Yield = 2 ATP Net Gain
Fermentation - Summary
• Releases 2 ATP from the
breakdown of a glucose
molecule
• Provides ATP to a cell even
when O2 is absent.
Aerobic Respiration
Aerobic Respiration
requires oxygen!
There are three phases to
Aerobic Respiration ... they are:
1. Glycolysis (same as the glycolysis of
anaerobic respiration)
2. Krebs cycle (AKA - Citric Acid cycle)
3. Oxidative Phosphorylation and The
Electron Transport Chain
Phase One: Glycolysis
(takes place in the cytoplasm)
Glycolysis
4 ATP’s are
produced
Pyruvic Acid (3C)
Glucose
(6 carbons)
2 ATP’s supply the
activation energy
2 NAD+ + 2 e-
Pyruvic Acid (3C)
2 NADH
4 ATP Yield = 2 ATP Net Gain
In order for Aerobic
Respiration to continue
the Pyruvic acid is first
converted to Acetic
Acid by losing a carbon
atom and 2 oxygens as
CO2.
The Acetic acid then
must enter the matrix
region of the
mitochondria. The CO2
produced is the CO2
animals exhale when
they breathe.
Phase Two: The Krebs Cycle
(AKA the Citric Acid Cycle)
Once the Acetic Acid enters the Matrix it combines with
Coenzyme A to form a new molecule called Acetyl-CoA.
The Acetyl-CoA then enters the Krebs Cycle.
Sir Hans Adolf
Krebs
Produces most of
the cell's energy in
the form of NADH
and FADH2… not
ATP
Does NOT require O2
CoA breaks off to gather
more acetic acid. The Acetic
acid is broken down.
+ 3H
3 NADH
Summary
As a result of one turn of the Krebs cycle the cell
makes:
1 FADH2
3 NADH
1 ATP
However, each glucose produces two pyruvic acid
molecules…. So the total outcome is:
2 FADH2
6 NADH
2 ATP
Comparing Aerobic
and
Anaerobic Respiration
• Aerobic Respiration–requires a mitochondrion and oxygen
–is a three phase process
• Anaerobic –
–does not require oxygen
–consists of one phase only-Glycolysis
Strict vs. Facultative Respiration
• Strict - can only carry out Respiration only
one way… aerobic or anaerobic. Ex - you
• Facultative - can switch respiration types
depending on O2 availability. Ex – yeast
• Aerobes – organisms that require oxygen
• Anaerobes - organisms that DO NOT require
oxygen
• Obligate Anaerobes – oxygen is LETHAL to
these organisms
• Facultative – organisms that can live with or
without oxygen
ATP Sum
• 10 NADH x 3 = 30 ATPs
• 2 FADH2 x 2 =
4 ATPs
• 2 ATPs (Gly) = 2 ATPs
• 2 ATPs (Krebs) = 2 ATPs
• Max = 38 ATPs per glucose
However...
Some energy (2 ATP’s) is used to
shuttle the NADH from
Glycolysis into the
mitochondria…..So, some
biologists teach there is an
actual ATP yield of 36 ATP’s per
glucose.