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Cellular Respiration How is energy in organic matter released for used for in living systems?
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
