Download Notes CH 7 - Haiku Learning

Chapter 7: Cell Respiration
• Cell respiration is the controlled release of energy
from organic compounds to produce ATP.
• ATP from cell respiration is immediately available as
a source of energy in the cell.
• Anaerobic cell respiration gives a small yield of ATP
from glucose.
• Aerobic cell respiration requires oxygen and gives a
large yield of ATP from glucose
I. Cell Respiration: Overview
A. Cell respiration is used by all cells to
produce ATP
1. Organic molecules contain energy in
their molecular structures
a) Each covalent bond in glucose,
amino acid, or fatty acid
represents stored chemical energy
2. Cells break down (metabolize) their nutrients by
slow oxidation (Can use glucose, amino acids, or
fatty acids)
a) Covalent bonds are broken (oxidized) by a
series of chemical reactions by the use of
enzymes
b) When a covalent bond is broken a small
amount of energy is released
c) Energy is released in a controlled way in
order to trap the released energy into ATP
Section 9-1
Chemical Pathways
Glucose
Glycolysis
Krebs
cycle
Fermentation
(without oxygen)
Go to
Section:
Electron
transport
Alcohol or
lactic acid
B. Glycolysis is the first step in cell respiration
1. All cells using glucose will start cell
respiration in the same way
2. Overview of steps
a) Glucose enters through cell
membrane and floats in the cytoplasm
b) Enzymes modify the glucose
c) Series of reactions that cut the 6C glucose
into two 3C molecules (pyruvate)
d) Some covalent bonds are broken and a
small amount of energy is released and forms
ATP
e) 2 molecules of ATP are used to start the
reaction and 4 molecules of ATP are
produced, so there is a net gain of 2 ATP
molecules Glycolysis
C. Anaerobic Respiration
1. Cell respiration: variety of biochemical
pathways that can be used to metabolize
glucose
2. Anaerobic: do not require oxygen
3. Aerobic: do require oxygen
4. Fermentation: breakdown of organic
molecules for ATP production in an
anaerobic way
a) Alcoholic
b) Lactic acid
D. Alcoholic fermentation
1. Yeast: single-celled fungus that uses
alcoholic fermentation for ATP production
when no oxygen is present
2. Yeast uses glucose and goes through
glycolysis to produce 2 ATP and 2 pyruvate
3. Pyruvate is then converted to ethanol,
carbon dioxide, and NAD+
4. Carbon dioxide makes dough rise
5. Ethanol is used in alcoholic
drinks
New Glarus Brewery
E. Lactic Acid Fermentation
1. Converts pyruvate into lactic acid
(lactate) and NAD+, when oxygen is not
present
2. Allows glycolysis to continue, which will
produce a small amount of ATP
3. Muscles cells will use lactic acid
fermentation during strenuous exercise when
they are not getting enough oxygen
Lactic Acid Fermentation
Section 9-1
Glucose
Go to
Section:
Pyruvic acid
Lactic acid
4. Used by microorganisms, which is used in
food products like yogurt and cheese
Fermentation clip
Examples of Food Products Using Fermentation
Bread: yeast, fungus
Yogurt: streptococcus, bacteria
Cheese: streptococcus, bacteria
Soy sauce: aspergillus, fungus
Cured olives: lactobacillus, bacteria
F. Aerobic cell respiration is the most efficient
pathway
1. Cells that have a mitochondria
usually use an aerobic pathway for
cell respiration
Steps
1. Glycolysis: make 2 ATP and 2 pyruvate
molecules
2. 2 pyruvate enter mitochondria and are
metabolized
3. Pyruvate loses a CO2 molecule and becomes
acetyl-CoA
4. Acetyl-CoA enters the Krebs cycle
5. Krebs cycle: series of reactions that begins and
ends with the same molecule
a) 2 molecules of CO2 are released
b) Some ATP and other molecules are made that
will further generate more ATP by using oxygen
(Electron Transport Chain)
Summary: Aerobic cell respiration breaks down a
glucose molecule and the end products are CO2, water,
and ATP
Equation: C6H12O6 + 6O2  6H2O + 6CO2 + ATP
Flowchart
Section 9-2
Cellular Respiration
Glucose
(C6H1206)
+
Oxygen
(02)
Go to
Section:
Glycolysis
Krebs
Cycle
Electron
Transport
Chain
Carbon
Dioxide
(CO2)
+
Water
(H2O)
Respiration: An Overview
Section 9-1
Mitochondrion
Electrons carried in NADH
Pyruvic
acid
Glucose
Glycolysis
Krebs
Cycle
Electrons
carried in
NADH and
FADH2
Electron
Transport
Chain
Mitochondrion
Cytoplasm
Go to
Section:
Interactive
Respirometer: devices used to measure an
organism’s rate of respiration by measuring the
oxygen rate of exchange
1. Carbon dioxide that is produced is
absorbed by potassium hydroxide
2. Measurement of oxygen exchange can
then be taken
II. Cell Respiration: Higher Level
A. Oxidation and reduction
1. Cellular metabolism is the sum total of all the
chemical reactions carried out by an organism
a) Catabolic: breakdown of complex
molecules into small molecules (cellular
respiration)
b) Anabolic: synthesis of more complex
molecules from simpler ones (photosynthesis)
Hints
• Oil: Oxidation is loss (of electrons)
• Rig: Reduction is gain (of electrons)
2. Oxidation and reduction reactions occur
together in a chemical reaction (Redox reaction)
3. Redox reactions play a key role in the flow of
energy through living systems: Electrons that
are flowing from one molecule to the next are
carrying energy with them
4. C6H12O6 + 6O2  6CO2 + 6 H2O + energy
a) Glucose is oxidized because electrons are
transferred from it to oxygen.
b) The protons follow the electrons to produce water.
c) Oxygen atoms on the reactant sided are reduced
d) Large drop in potential energy of the compounds
on the product side of the equation
B. Glycolysis: sugar splitting
1. Characteristics
a) Perhaps the first biochemical pathway to evolve
b) Uses no oxygen
c) Occurs in cytosol/cytoplasm
d) No organelles required
e) Occurs in both prokaryotic and eukaryotic cells
f) Hexose sugar, usually glucose, is split in three
stages
Three stages of glycolysis
1. Two ATP are used
a) Phosphorylation: phosphates from ATP
are added to glucose to form
fructose-1,6-biphosphate
b) Step creates a less stable molecule
2. Lysis: Splitting of fructose-1,6-biphosphate into
two 3-carbon sugars called glyceraldehyde-3phosphate (G3P)
3. Oxidation phase: 2 molecules of G3P undergo
oxidation
a) NAD+ (electron carrier) is reduced to form NADH
b) Released energy is used to
add phosphates to the 3-C compound
c) Enzymes then remove phosphates
to form ATP from ADP
d) End result: 4 ATP, 2 NADH, and 2
pyruvate
2. Summary of glycolysis
a) 2 ATPs are used to start process
b) 4 ATPs are produced for net gain of 2
c) 2 molecules of NADH are produced
d) Pathway involves substrate level
phosphorylation, lysis, oxidation, and ATP
production
e) Occurs in cytoplasm
f) Controlled by enzymes: when ATP levels in the
cell are high, feedback inhibition will block the first
enzyme of the pathway to slow or stop the process
g) 2 pyruvate molecules are present at the end of
the pathway
Glycolysis
C. Link Reaction
1. If oxygen is present after glycolysis, the pyruvate enters
the matrix of the mitochondria by active transport
2. Pyruvate is decarboxylated: removal of a carbon atom to
form carbon dioxide and 2-C acetyl group
a) CO2 is released as a waste gas
b) Acetyl group is oxidized with the formation of
NADH
3. Acetyl group combines with coenzyme A (CoA) to form
acetyl CoA
4. Acetyl CoA will enter the next step, the Krebs cycle
Coenzyme: molecule that aids an enzyme in its
action and usually acts as electron donors or
acceptors
5. Acetyl CoA can be produced from most
carbohydrates and fats
a) If ATP levels are high, then acetyl CoA can
be stored as a lipid
b) If ATP levels are low, then acetyl CoA will
enter the Krebs cycle
D. Krebs cycle: tricarboxylic acid cycle
1. Overview
a) Occurs in matrix of mitochondria
b) Cycle because it begins and ends with the
same substance
Steps
1. Acetyl CoA combines with 4-C oxaloacetate to
form 6-C citrate
2. Citrate is oxidized and decarboxylated to from a
5-C compound
a) CO2 is released
b) NAD+ is reduced to NADH
3. 5-C compound is oxidized and decarboxylated to
form a 4-C compound
a) CO2 is released
b) NAD+ is reduced to form NADH
4. 4-C compound undergoes various changes and
produces several products
a) NADH
b) Coenzyme FAD is reduced to FADH2
c) Reduction of ADP to make ATP
d) 4-C compound changed into starting
compound of oxaloacetate
Krebs cycle
krebstca
2. Summary for one molecule of glucose
a) Krebs cycle runs twice for each glucose
molecule since 2 molecules of pyruvate are made
in glycolysis
b)
c)
d)
e)
2 ATP
6 NADH
2 FADH2
4 CO2
Special note on CO2: 2 CO2 are released in the link
reaction and 4 are released during Krebs cycle, so
glucose is completely catabolized and energy is now
carried as NADH, FADH2, or stored as ATP
3. Summary of ATP production for glycolysis and
Krebs cycle
a) 4ATP made in glycolysis
b) 2 ATP from Krebs cycle
c) 2 ATP were used to start glycolysis
d) Total of 4 ATP gained and made by
substrate-level phosphorylation
e) Substrate-level phosphorylation: ATP is
made by phosphate group being transferred
directly to ADP from phosphate-bearing
molecule
E. Electron transport chain
1. Electron transport chain: most of the
ATP is made, oxygen is needed, and occurs in
the inner mitochondrial membrane and cristae
membranes of the mitochondria
2. Molecules are embedded in the membranes
that are easily oxidized and reduced
3. Electrons (energy) carriers are close
together and pass the electrons from one to
another because of an energy gradient
4. Each carrier has a slightly different
electronegativity and therefore a different
attraction for electrons
5. Cytochromes: carriers that are proteins
with heme (haem) group
6. Coenzyme Q: carrier that is not a protein
7. Electrons are passed down the chain from
one carrier to the next
Electron Transport Chain: Oxidation and reduction
reactions
8. During the process of electron transport,
small amounts of energy are released
9. NADH and FADH2 supply the electrons
that move through the electron transport
chain
10. Oxygen is the final electron acceptor
because it has a very high electronegativity
and has a strong attraction for electrons
11. The oxygen with its electrons combines with 2
hydrogens from the surroundings and forms water
12.Energy lost at each step is used by the cell for
phosphorylation to make ATP
Electron transport chain
F. Chemiosmosis: process of making ATP by the
movement of protons (H atoms) to provide
energy so phosphorylation can occur
1. Oxidative phosphorylation: uses the
electron transport chain to make ATP
2. Mitochondria structure is closely related to its
function in cellular respiration
a) Matrix: space where the Krebs cycle occurs
b) Cristae: folded interior membranes that
holds enzymes and provides a large surface area
for electron transport chain and forms a barrier
allowing protons to increase on one side
3. ATP synthase: enzyme in the inner membranes
that uses the energy of an ion gradient to allow
the phosphorylation of ADP to form ATP
a) Ion gradient is created by a difference in
hydrogen ion concentration across the cristae
membranes
b) H+ are pumped out of the matrix into the
intermembrane space and the energy is
provided by the electrons moving through the
electron transport chain
c) More H+ on one side of the membrane creates the
gradient
d) H+ then moves passively through a channel in
ATP synthase back into the mitochondrial matrix
e) As the H+ moves through the ATP synthase, the
enzyme harnesses the available energy and allows
the phosphorylation of ADP into ATP
http://www.science.smith.edu/departments/Biology/B
io231/etc.html
ATP synthase
G. Summary of ATP production in cellular respiration
1. Complete catabolism of one molecule of
glucose
a) Reactants: glucose and oxygen
b) Many enzymes, carriers, and other
molecules used in the process
c) Products: CO2, water, and ATP
2. ATPs are essential because they provide the
energy by which life is maintained
3. Energy flow
4. Three main processes in cellular respiration
a) Glycolysis
b) Krebs cycle
c) Electron transport chain
5. 36 ATP are produced, but in reality it is closer to 30
a) Some H+ may move back to the matrix without going
through ATP synthase
b) Some energy used to move pyruvate into mitochondria
c) About 30% of the energy present in chemical bonds of
glucose is generated into ATP and the rest of the energy is
lost from the cell as heat
6. Cellular respiration: process by which ATP is
provided to the organisms so it can live
a) Complex series of chemical reactions
b) Mostly takes place in mitochondria
c) All organisms need the ability to produce
ATP for energy, so all organisms carry out
respiration
C6H12O6 + 6O2 6CO2 + 6H2O + ATP
Cell Respiration Song