CELL
RESPIRATION
TO P I C 2 . 8 A N D 8 . 1
CELL RESPIRATION
• Is used by all cells to produce ATP
• Organic molecules contain energy
– Each covalent bond represents stored chemical energy
• Cells perform slow oxidation (act of burning/breaking covalent bonds)
– Molecule is acted upon by a series of enzymes
• Trap released energy in ATP molecules
CELL RESPIRATION
• Cell Respiration--controlled
release of energy from organic
compounds in cells to form
ATP
• Aerobic Cellular Respiration
a metabolic pathway with over
20 reactions,
using 20 enzymes
OXIDATION AND REDUCTION
Oxidation
Reduction
Loss of electrons
Gain of electrons
Gain of oxygen
Loss of oxygen
Loss of hydrogen
Gain of hydrogen
Results in many C-O bonds
Results in many C-H bonds
Results in a compound with lowers potential energy
Results in a compound with higher potential energy
LEO goes GER
Lose Electrons Oxidized
Gain Electrons Reduced
MITOCHONDRION--STRUCTURE AND FUNCTION
2 PHOSPHOLIPIDS BILAYERS WITH EMBEDDED PROTEIN
Aerobic Cellular Respiration
C6H12O6 + 6O2 --> 6CO2 + 6H2O
GLYCOLYSIS
• Two molecules of ATP are used to begin. The phosphates from the
ATPs phosphorylate glucose to form fructose-1,6-bisphosphate.
6- carbon glucose
2 ATP
2 ADP
P
Substrate-level
Phosphorylation
P
GLYCOLYSIS
• The 6C phosphorylated fructose is split into two 3C sugars called
glyceraldehyde – 3 – phosphate (G3P)
P
P
Lysis
P
Glyceraldehyde – 3 – phosphate
P
Glyceraldehyde – 3 – phosphate
GLYCOLYSIS
• Entering the oxidation phase: ATP formation and production of the
reduced coenzyme NAD. As NADH is being formed, released
energy is used to add an inorganic phosphate. Phosphates are
removed, creating pyruvate.
Substrate-level phosphorylation
2 P
P
P
P
2
2
2
G3P
pyruvate
2NAD+
Oxidation
2 NADH
4 ADP
4 ATP
GLYCOLYSIS
• Summary
– Two ATPs are used to start the process
– A total of four ATPs are produced – a net gain of two ATPs
– Two molecules of NADH are produced
– Involves substrate – level phosphorylation, lysis, oxidation and ATP
formation
– Occurs in the cytoplasm of the cell
– This metabolic pathway is controlled by enzymes
– Two pyruvate molecules are present at the end of the pathway
ANAEROBIC RESPIRATION
• ‘Cell Respiration’ – refers to a variety of biochemical pathways that
can be used to metabolize glucose
• All the pathways start with GLYCOLYSIS
• Occurs in an anaerobic environment
– Without oxygen
• Breaking down organic molecules in an anaerobic environment is
FERMENTATION
ALCOHOLIC RESPIRATION
• Yeast use alcoholic respiration for ATP production
– Use in Bread and Alcoholic production
CO2
Pyruvate
3C
Glucose
6C
Ethanol
2C
CO2
Pyruvate
3C
Glycolysis
Net gain of 2 ATP
Ethanol
2C
LACTIC ACID FERMENTATION
• Aerobic cells (like our muscle cells) can be starved of oxygen (like
when exercising) and enter anaerobic respiration
• Benefit?
– Allows glycolysis to continue with the small gain of ATP (even if the
aerobic pathway is not accessible)
Pyruvate
3C
Glucose
6C
Lactate
3C
Reaction reversible when oxygen
available
Pyruvate
3C
Net gain of 2 ATP
Aerobic Pathway
(lots of ATP made)
Lactate
3C
AEROBIC IS MORE EFFICIENT
Aerobic
Anaerobic
Breaks down glucose completely
Partial breakdown
End products: CO2 and H2O
End Products: ethanol and lactic acid
Large yield of ATP (34-38)
Low yield of ATP (only 2)
LINK REACTION
Pyruvate enters the matrix of the
mitochondria via active transport
1.
CO2 is released as a waste
gas
2.
Acetyl group is oxidized
while reducing NAD+
3.
Acetyl group combines with
coenzyme A (CoA) to form
Acetyl CoA
– CoA acts as a transport to get
Acetyl to the Kreb’s cycle
Reaction is controlled by
enzymes
KREB’S CYCLE
• Acetyl CoA:
– Can be produced from most carbohydrates and fats
– Can be synthesized into a lipid for storage
• Occurs with ATP levels are high
• Kreb’s Cycle
– When ATP is needed, acetyl CoA enters the cycle
– Occurs in the matrix of the mitochondria
KREBS CYCLE
• Acetyl CoA from the link reaction combines with a 4C compound
called oxaloacetate. The result if a 6C compound called citrate
AcetylCoA
Oxaloacetate
4C
- CoA
CoA
Citrate
6C
KREBS CYCLE
• Citrate (6C compound) is oxidized to form a 5C compound. In this
process, the carbon is released from the cell (after combining with
oxygen) as CO2. While the 6C compound is oxidized, NAD+ is
reduced to form NADH
Acetyl CoA
4C
CoA
6C
CO2
NAD+
5C
NAD
H
KREBS CYCLE
• The 5C compound is oxidized and decarboxylated to form a 4C
compound. Again, the removed carbon combines with oxygen and
is released as CO2. Another NAD+ is reduced to form NADH.
Acetyl CoA
CoA
4C
6C
CO2
NAD+
5C
4C
NAD
H
CO2
NAD+
NAD
KREBS CYCLE
• The 4C compound undergoes various changes resulting in several products.
One product is another NADH. The coenzyme FAD is reduced to from FADH2.
There is also a reduction of an ADP to form ATP. The 4C compound is changed
during these steps to re-from oxaloacetate.
Acetyl CoA
NAD
H
CoA
4C
6C
oxaloacetate
CO2
NAD+
NAD+
5C
FADH2
FAD
4C
ATP
ADP + Pi
NAD
NAD
H
CO2
NAD+
KREB’S CYCLE SUMMARY
• For each glucose, the cycle runs TWICE
• Products
– 2 ATP molecules
– 6 NADH molecules (allow energy storage and transfer)
– 2 FADH2 molecules
– 4 CO2 molecules
ELECTRON TRANSPORT CHAIN
• Where most of ATP is created
• Oxygen is needed
• Occurs in Mitochondria, on inner membrane and cristae
• Within the membranes are molecules
These carriers of electrons pass electrons from
one to another due to an energy gradient, due to
electronegativity.
As electrons move down the chain of
molecules, energy is released.
Electrons are provided by
coenzymes NADH and
FADH2
Each Movement
releases energy
Carriers:
• FMN: protein carrier has a
flavin-containing group
• Cyt: Cytochromes (ironcontaining proteins)
• CoQ: Coenzyme Q
(ubiquinone) is not a protein
Note: FADH2 enters later in the
chain, which means less energy is
given, therefore fewer ATPs are
produced
NADH: 3 ATPs
FADH2: 2 ATPs
At the end of chain, de-energized
electrons are accepted by oxygen
CHEMIOSMOSIS
• Involves the movement of protons (H+) to provide energy so that
phosphorylation can occur – oxidative phosphorylation
As e- is moved to each protein, the energy
released sends H+ against gradient
H+ pass back
through ATP
synthase creating
the energy needed
to attach an
inorganic
phosphate to ADP
2. Using the small amount of energy
released, H+ are pushed against
concentration gradient
3. As H+ concentration gets to be
too high, H+ passively move through
the ATP synthase
Inner
Membrane
Space
Inner
Membrane
4. As H+ passes
through, ATP
synthase spins, this
creates the energy
needed to attach
the P to the ADP
making ATP
Matrix
1. e- flow through chain,
releasing small amount of energy
Protons available
to move against
gradient
Oxygen is the final eacceptor creating water
C 6H 12O 6 + 6O 2 --> 6CO 2 + 6H 2O+ ENERGY
Stage
Location
Glycolysis cytosol
Link
Reaction
Reactants
Products
ATP
molecules
1 Glucose,
2 ATP, 4ADP,
2 NAD +
2 Pyruvate
4 ATP
2 NADH
2
2 Acetyl CoA
2 CO2
2 NADH
0
Upon entering 2 pyruvate
mitochondrion 2 CoenzymeA
2 NAD +
Krebs
Cycle
Mitochondria
matrix
2 Acetyl CoA
6 NAD +
2 FAD, 2 ADP
4 CO2
6 NADH
2 FADH2 2
ATP
2
Electron
Transport
Chain
Mitochondria
Cristae (inner
membrane)
10 NADH
2 FADH2
34 ATP
34
6O2
6H2O
FINAL LOOK
Structure
Function
Outer Mitochondrial Membrane
Separates the contents of the mitochondrion from the rest
of the cell
Matric
Internal cytosol-like area that contains the enzymes for the
link reaction and the Kreb’s cycle
Cristae
Tubular regions surrounded by membranes increasing
surface area for oxidative phosphorylation
Inner mitochondrial membrane
Contains the carriers for the electron transport chain and
ATP synthase for chemiosmosis
Inner membrane space
Reservoir for hydrogen ions (protons), the high
concentration of hydrogen ions is necessary for
chemiosomosis