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Cellular RespirationHow is energy in organic matter released for used for in living systems?
Cellular Respiration
Organisms that perform cellular respiration are called chemoheterotrophs● Includes both eukaryote and prokaryote cells● Ex. Animals, fungi, bacteria and PLANTS
2 main types of cellular respiration:○ Aerobic
■ Consumes oxygen■ Occurs in mitochondria■ Large energy output (36 ATP)
○ Anaerobic■ Does not require oxygen■ Called “fermentation”■ Small energy output (2 ATP)
Cellular Respiration
Like photosynthesis, cellular respiration also relies on high-energy molecules
NAD+ and FAD+ are electron acceptors NADH and FADH2 are electron carriers
Low-energy form High-energy form
ADP/P → ATP ←
NAD+, H+, 2e- → NADH←
FAD+, 2H+, 2e- → FADH2←
Similar to
NADP+/NADPH
In cellular respiration, once NADH and FADH2 are produced they enter the ETC and are
converted into ATP
1 NADH → 3 ATP1 FADH2 → 2 ATP
NADH ( Nicotinamide adenine dinucleotide)and FAD (Flavin adenine dinucleotide)
NAD+ is an electron acceptor
it becomes reduced (accepts electrons) to become NADH
NAD+ + H+ + 2e- → NADH
NADH → NAD+ + H+ + 2e-
FAD is an electron acceptor
it becomes reduced (accepts electrons) to become FADH2
FAD+ + 2H+ + 2e- → FADH2
FADH2 → FAD+ + 2H+ + 2e-
Reduction reaction (molecule is gaining electrons)
Oxidation reaction (molecule is losing electrons)
Aerobic Respiration - introduction
4 main stages:
1. Glycolysis2. Pyruvate oxidation3. Krebs cycle4. ETC
Is the complementing process to photosynthesis.
NET aerobic respiration reaction:
1 glucose + 6 O2 + 36 ADP/P → 6 CO2 + 6 H2O + 36 ATP
The Mitochondria - ‘the ATP powerhouse’
Inner Membrane
Outer Membrane
Intermembrane Space
Cristae (fold of the inner membrane)
Matrix (space inside the inner membrane)
Aerobic Respiration - 1. Glycolysis
Is the first step of cellular respiration
Happens in BOTH aerobic and anaerobic respiration
Occurs in cytoplasm of the cell
Aerobic Respiration - 1. Glycolysis
Glycolysis convert 1 glucose into 2 pyruvate molecules(6C) 2x (3C)
2
2
4
4
Aerobic Respiration - 1. Glycolysis
Requires an initial investment of 2 ATP
As glucose bonds broken, the energy is used to form 4 ATP and 2 NADH
NET glycolysis reaction:
1 glucose + 2 ADP/P + 2 NAD+
2 pyruvate + 2 ATP + 2 NADH
2
2
4
4
Aerobic Respiration - 2. Pyruvate Oxidation
Is the second step of aerobic cellular respiration
The 2 pyruvate molecules from glycolysis are transported to the matrix of mitochondria
Aerobic Respiration - 2. Pyruvate Oxidation
Pyruvate Oxidation converts each pyruvate into a aceytl-CoA molecule
Note: Since 2 pyruvate molecules are produced from 1 glucose, pyruvate oxidation and the Krebs cycle each occur 2x
Aerobic Respiration - 2. Pyruvate Oxidation
Coenzyme A (CoA) is added to the pyruvate
releasing a CO2 molecule
NET pyruvate oxidation reaction:
2 pyruvate + 2 NAD+ + 2 CoA
2 acetyl-CoA + 2 NADH + 2 CO2
Glycolysis and Pyruvate Oxidation:
Have gone from a 6C molecule to two, 2C molecules.
How?
What high-energy molecules have we released so far?
Poster projectsAerobic Cellular Respiration
Glycolysis and Pyruvate Oxidation:
So far have gone from a 6C molecule to two, 2C molecules.
How? Can you fili in the blanks?
Could you write a NET equation for each step?
Aerobic Respiration - 3. Krebs Cycle
Occurs in the matrix of the mitochondria
Converts acetyl-CoA into ATP, NADH and FADH2
also called The Citric Acid cycle
Aerobic Respiration - 3. Krebs Cycle
The Krebs Cycle:
● Acetyl-CoA (2-carbon) molecule enters cycle, is converted to Citric acid (6-carbon)
● Citric acid undergoes several ‘rearrangements’ as high-energy bonds are replaced by low-energy bonds, until it returns to a 4-carbon state
● Released energy is used to form NADH, FADH2 and ATP
● 2 Carbons are released as CO2 gas
Aerobic Respiration - 3. Krebs Cycle
1 acetyl-CoA produces 2 CO2, 3 NADH, 1FADH2 and 1 ATP
(our NET equation per 1 glucose is x2)
NET Krebs cycle reaction:
2 acetyl-CoA + 6 NAD + 2 FAD + 2 ADP
4 CO2 + 6 NADH + 2 FADH2 + 2 ATP
Aerobic Respiration - 4. ETC
Occurs on the inner membrane of the mitochondria
Converts NADH and FADH2from Krebs cycle into ATP= oxidative phosphorylation
1 NADH → 3 ATP1 FADH2 → 2 ATP
Aerobic Respiration - 4. ETC
1. NADH or FADH2 donates high-energy electrons to ETC2. ETC transports H+ ions from matrix into intermembrane space 3. H+ ions accumulate in the intermembrane space creating an
electrical AND chemical concentration gradient = chemiosmosis4. ATP synthase uses the energy released as H+ moves from high
to low area of concentration gradient to generate ATP from ADP and P molecules = phosphorylation
5. The low-energy electrons at the end of the ETC are released by combining with O2 and H+ to form H2O = terminal electron acceptor
Aerobic Respiration - 4. ETC
NADH (or FADH2) donates e- to ETC
ETC transports H+ from matrix to intermembrane space
H+ accumulate in intermembrane space creating a concentration gradient
ATP synthase is powered by H+ gradient to produce ATP
terminal electrons are accepted by oxygen, forming H2O
Aerobic Respiration - summary
NET aerobic cellular respiration reaction:
1 C6H12O6 + 6O2 + 36 ADP/P → 6 CO2 + 6 H2O + 36 ATP
Where do the 36 ATP come from?
Aerobic Respiration - summary
Aerobic Respiration - summary
3. Krebs Cycle2 acetyl-CoA produce 6 NADH, 4 FADH2 and 2 ATP
2. Pyruvate Oxidation2 pyruvate molecules are converted into 2 acetyl-CoA molecules
Energy is released forming 2 NADH → 6 ATP
1. GlycolysisHigh-energy bonds of glucose are broken to form 2 pyruvate molecules
Energy released is used to form 2 ATP and 2 NADH
Cellular Respiration
Organisms that perform cellular respiration are called chemoheterotrophs● Includes both eukaryote and prokaryote cells● Ex. Animals, fungi, bacteria and PLANTS
2 main types of cellular respiration:○ Aerobic
■ Consumes oxygen■ Occurs in mitochondria■ Large energy output (36 ATP)
○ Anaerobic■ Does not require oxygen■ Called “fermentation”■ Small energy output (2 ATP)
Anaerboic Cellular Respiration
In environments without oxygen the ETC stops! (O2 is the terminal electron acceptor)
Glycolysis allows the cell to obtain 2 ATP for 1 glucose molecule but without the ETC there is no source of NAD+(so no glycolysis!)
Cells have evolved other ways of regenerating NAD+, one type is by fermentation...
NET OUTPUT 2 ATP
Anaerboic Cellular Respiration
Fermentation: transferring H+ molecule from NADH to organic molecules (instead of ETC)
Alcohol Fermentation
Lactic Acid Fermentation
Alcohol Fermentation● Occurs in yeast● Pyruvate (3 carbon) is converted into acetaldehyde
(2carbon)● NADH transfers H to acetaldehyde to form ethanol● excess Carbon released as CO2 gas
Alcohol Fermentation
● What are some uses of yeast (alcohol fermentation)?
Tomorrows lab will be looking at temperature as it affects rate of alcohol fermentation
Lactic Acid Fermentation● Occurs in most animal cells● Under high-energy demands cells require more ATP ● Lactic acid fermentation is a method of cells to quickly
break down glucose to release ATP ● NADH transfers H to pyruvate to form lactic acid
● Lactic acid is metabolised by the liver into glucose● It then can be transported back to cells (mitochondria)
● The increased pumping of blood and oxygen needed during exercise is experienced as increased heart rate and breathing
Lactic Acid Fermentation
Lactic Acid Threshold: Limit of exercise where production of lactic acid increases
Exercising above your lactic acid threshold will cause more pain, stiffness and fatigue
Lactic Acid Fermentation
Rigor Mortis - stiffening of muscles after death
Due to lactic acid buildup in muscles as glucose is fermented rapidly as oxygen levels drop
Exercise Physiology
● Aerobic Fitness - also called cardiopulmonary fitness● Is how well your body (heart, lungs, blood) can deliver
oxygen to your cells
Affected by body composition (fitness)
Better Aerobic Fitness = More oxygen to cells = More cellular respiration = More ATP = More energy
Muscle cells have high energy demands!
Exercise Physiology
VO2max: maximum oxygen consumption (mL/kg/min)Is a measure of the body’s ability to generate the ATP needed for physical activity
Measured by a treadmill test, where the person is pushed to run as fast as possible while breathing into a machine which measure oxygen consumption
