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Cellular Respiration and Fermentation

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Jean Battinieri

on 15 February 2019

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Transcript of Cellular Respiration and Fermentation

Cellular Respiration
The break down of sugar that occurs WITHOUT oxygen
break down of sugar WITH oxygen to create energy (ATP)
(NAD+) + (e-) + (H+) + (e-) yields NADH
(FAD) + (e-) + (H+) + (e-) + (H+) yields FADH
Two ways to generate or re-generate energy

Cellular respiration Fermentation

with Oxygen w/out Oxygen

both start with a process called glycolysis
break down of glucose
The main energy foods, carbohydrates and fats, are reservoirs of electrons associated with hydrogen, the breaking of these bonds and the transfer of the electrons.
Cellular respiration brings hydrogen and oxygen together to form water.
Oxygen's role:
the H that reacts with oxygen is derived from organic molecules.
Uses Electron Transport Chain (ETC) to break the fall of electrons to oxygen into several energy-releasing steps
ETC consists of a number of molecules mostly proteins built into the inner membrane of a mitochondria
Electrons removed from food are shuttled by NADH to the "top" end of the oxygen captures these electrons along with H+ forming water
Electrons cascade down the chain from one carrier molecule to the next losing a small amount of energy with each step until they reach oxygen - THE TERMINAL ELECTON ACCEPTOR
Oxygen pulls electrons down the chain in an energy-yielding tumble similar to gravity pulling objects downhill
Transition reaction and Krebs Cycle/Citric Acid cycle
occurs in the cytosol
can occur with oxygen - if it does then cellular respiration occurs
can occur without oxygen - if it does then fermentation occurs
Krebs Cycle also called the Citric Acid Cycle
Take place in the mitochondrial matrix
Named for Hans Kreb
The Process
Acetyl CoA (2C) joins with oxaloacetate (4C) producing Citric Acid (6C)
Citrate converts to isocitrate
Isocitrate (6C) loses a CO2 and forms alpha ketogluteric acid (5C) AND NAD+ picks up electrons to form NADH
alpha ketogluteric acid loses a CO2 and converts to succinic acid (4C)- as this occurs, NAD+ picks up electrons to form NADH, ADP converts to ATP
Succinic acid converts to Fumaric acid - as this occurs FAD picks up electrons and forms FADH
Fumaric Acid converts to Malic acid
Malic Acid converts to Oxaloacetic acid - as this occurs NAD+ picks up electrons to form NADH and the cycle continues
Transition Reaction
The junction between glycolysis and the Krebs Cycle
Pyruvate carboxyl's group is removed as CO The two carbons that are left forms acetate and NAD+ picks up electrons to form NADH
Coenzyme A reacts with acetate to form Acetyl CoA
Acetyl CoA moves into the Kreb's Cycle and bonds with oxaloacetic acid
Cellular Respiration has 3 main pathways if oxygen is present
In eukaryotes
glycolysis - occurs in the cytosol
Krebs Cycle - occurs in the mitochondrial matrix
Electron Transport Chain (ETC) - occurs in the inner mitochondrial membrane (christae)
C H O + 6O + 6H O 6CO + 12 H O + energy
Electron Transport Chain (ETC) and Chemiosmosis
The electron transport chain
collection of molecules (mostly proteins) in the inner membrane of the mitochondrion
folding of the inner membrane to form cristae increases surface area
electrons removed from food during Glycolysis and the Krebs cycle are transferred by NADH to the first molecule of the ETC
the last part of the chain passes the electrons to oxygen which also picks up a pair of hydrogen ions to form water
for every 2 NADH molecules one O forms 2H O
Another source of electrons is for the ETC is FADH which also comes from the Krebs cycle
FADH enters the ETC at a lower level than NADH therefore it provides less energy than the NADH
Chemiosmosis occurs next
many copies of ATP synthase
ATP synthase uses the energy of an existing ion gradient - the difference in the concentration of H+ on opposite sides of the inner mitochondrial membrane
the ETC is an energy converter that use the exergonic flow of electrons to pump H+ across the membrane, from the matrix to the intermembrane space
H+ pass through ATP synthase which uses the energy to convert ADP to ATP
chemiosmosis is an energy coupling mechanism that uses energy stored in the form of an H+ gradient across a membrane to drive cellular work
chloroplasts use this too to make ATP
Prokaryotes which lack both mitochondria and chloroplasts, generate H+ gradients across their plasma membranes.
Energy totals for cellular respiration for one glucose molecule
2 NADH that goes to the ETC
Krebs Cycle
Transition Reaction
2 NADH that go to the ETC
6 NADH that go to the ETC
2 FADH that go to the ETC
2 NADH (from Glycolysis) form 4 ATP
2 NADH (from Transition) form 6 ATP
6 NADH (from Krebs) form 18 ATP
2 FADH (from Krebs) form 4 ATP
Compare and contrast cellular respiration and photosynthesis
Cell respiration
2 common type of fermentation
alcoholic fermentation
lactic acid fermentation
fermentation is an extension of glycolysis that can help generate ATP - as long as there is a way to recycle NAD+ from NADH
Alcohol fermentation
pyruvate is converted into ethyl alcohol
2 step process
releases CO2 from pyruvate which is converted into acetaldehyde
acetaldehyde is reduced by NADH to ethyl alcohol - regenerating NAD+ for glycolysis
carried out by yeast, fungus, and many bacteria
used in brewing, wine making, and making bread
Lactic Acid Fermentation
reduced directly by NADH to form lactic acid
used by some fungi and bacteria
used in the dairy industry to make cheese and yogurt
human muscle cells make ATP by lactic acid fermentation when Oxygen is scarce
occurs in the early stages of exercise - 1st 90 seconds
occurs when the breakdown of glucose for ATP production happens faster than the muscles can supply the oxygen from the blood
cells switch from aerobic respiration to L.A. fermentation
L.A. accumulates as a waste product and may cause muscle fatigue and pain
the L.A. is gradually carried away by the blood to the liver where is is converted back to pyruvic acid
Compare and contrast cell respiration and fermentation
cell respiration

In prokaryotes:
glycolysis - cytosol/cytoplasm
Krebs - cytosol/cytoplasm
ETC - cell membrane
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