Download Glycolysis Krebs Cycle Electron Transport Chain Carbon Dioxide

Cellular Respiration
What we do with the glucose
from photosynthesis to
release the energy stored in
it
Stored Energy
• The amount of energy available in a
molecule is measured in calories: the
amount of energy needed to warm 1
gram of water by 1 degree C.
• In food, this energy is measured as
kilocalories (kilo =?), or Calories.
• A gram of carbohydrates has 4
Calories; a gram of fat has 9.
Cellular respiration
Electrons carried in NADH
Pyruvic
acid
Glucose
Glycolysis
Krebs
Cycle
Electrons
carried in
NADH and
FADH2
Electron
Transport
Chain
Mitochondrion
Cytoplasm
Cellular Respiration
Glucose
(C6H1206)
+
Oxygen
(02)
Glycolysis
Krebs
Cycle
Electron
Transport
Chain
Carbon
Dioxide
(CO2)
+
Water
(H2O)
Glycolysis
Glucose
2 Pyruvic acid
To the electron
transport chain
What if there is no O2?
• One round of glycolysis doesn’t make
much ATP, but it happens really fast
and is done by thousands sets of
enzymes per second in a cell.
• Problem: lots of NAD+ is needed to pick
up electrons and H+. It will run out very
quickly.
• Usually aerobic respiration recycles it.
Aerobic and anaerobic pathways
Glucose
Glycolysis
Krebs
cycle
Fermentation
(without oxygen)
Electron
transport
Alcohol or
lactic acid
Lactic acid fermentation
Glucose
Pyruvic acid
Lactic acid
The point of fermentation
• Fermentation produces no more ATP,
but returns NADH to the low energy
form NAD+; this allows glycolysis to
continue working.
• Humans appreciate the products of
alcohol fermentation and use them to
produce alcohol and to make bread
rise.
Good, but not great
• Glycolysis and fermentation provide
enough ATP for single celled
organisms, or to power larger
organisms for a short time.
• Bigger organisms need to take
advantage of the remaining energy in
pyruvic acid.
Why Do We Need So Much ATP?
Number of
molecules per
cell
Molecules
synthesized per
second
Molecules of ATP required per
second for synthesis
DNA
1
0.00083
60,000
RNA
15,000
12.5
75,000
Polysacch
arides
39,000
32.5
65,000
Lipids
15,000,000
12,500.0
87,000
Proteins
1,700,000
1,400.0
2,120,000
Aerobic respiration
• Happens in the mitochondrion.
• 2 Sets of reactions:
– Krebs Cycle in mitochondrial matrix
– Electron transport chain and
chemiosmosis in cristae.
Citric Acid
Production
The Krebs Cycle
Krebs cycle
• From each pyruvic acid, a set of
chemical reactions produces
– 2 ATP
– NADH
– FADH2
– CO2 as a byproduct
• Since we started with 2 pyruvic acids,
the cycle runs twice for each glucose.
On to electron transport…
• The NADH and FADH2 will be used in
the electron transport chain.
– H ions will be released from them and
electrons will pump the ions
– chemiosmosis – just like in
photosynthesis!
Electron Transport Chain
Electron Transport
Hydrogen Ion Movement
Channel
Intermembrane
Space
ATP synthase
Inner
Membrane
Matrix
ATP Production
Aerobic exercise
• Aerobic respiration gives us more ATP,
but it takes longer to get started.
• Conditioning increases the number of
mitochondria in cells and the number
of red blood cells so we are better at
carrying oxygen.
• These factors make aerobic respiration
work more efficiently.
Anaerobic exercise?
• At the beginning of exercise, we rely on
glycolysis and fermentation to provide
ATP. Lasts about 90 seconds.
• After long periods of exercise
(breathing hard!) we start to run out of
oxygen and have to switch back to
fermentation for a bit.
• Lactic acid accumulates in muscles –
what happens?