Lecture 29 Flashcards
Acetyl groups completely oxidize to what in the citric cycle
CO2
Substrate-level phosphorylation produces what
Citric cycle
ATP
Electrons removed in oxidations accepted by what
Citric cycle
NAD+ or FAD
Each acetyl group oxidized produces what
2CO2
1ATP
3NADH
1FADH2
Summary of citric acid cycle
8 reactions of the citric acid cycle (tricarboxylic acid cycle / Krebs cycle) oxidize acetyl groups completely to CO2, generate 3 NADH and 1 FADH2, and synthesize 1 ATP by substrate-level phosphorylation
1 acetyl-CoA + 3NAD+ + 1FAD + 1 ADP + 1 Pi + 2H2O -> 2CO2 + 3NADH + 1FADH2 + 1ATP + 3H+ + 1 CoA
Real payoff of cellular respiration is in the electron transport chain (aka respiratory chain)
Where does it take place
Inner membrane of the mitochondria
Electron transport chain and oxidative phosphorylation
A sequence of electron- carrier molecules that shuttle electrons during redox reactions, with the release of energy
Chain contains three (four) large enzyme complexes and several (mobile) electron carriers
The carriers can exist in an oxidized form or reduced form. Bind and release electrons in redox rxns
Electrons from NADH or FADH2 entering electron transport chain have relatively high energy content. And lose it as they go down each step of the chain
As redox occurs the electron carriers use some of the energy released as electrons pass down electron transport chain to actively transport protons (H+ ions) from one side of the mitochondrial membrane to the other. Which results in an H+ gradient
In the end. Electrons are simultaneously united with H+ from the surrounding medium to form hydrogen which reacts with O2 to produce water
NADH AND FADH2 are primary electron donors
O2 is the final electron acceptor
Electron transport chain is embedded where
Inner mitochondrial membrane (comparable to bacterial plasma membrane)
The chain contains three (four) large enzyme complexes
and several (mobile) electron carriers:
I NADH-Q redux taste complex
II (Succinate-Q reductase complex)
III cytochrome b/c1 reductase complex
IV cytochrome c oxidase complex
Flavin mono nucleotide (FMN)
Ubiquinome (Q)
Cytochrome (b. c. c1. a. a)
H+ chain
As redox occurs the electron carriers use some of the energy released as electrons pass down electron transport chain to actively transport protons (H+ ions) from one side of the mitochondrial membrane to the other. Which results in an H+ gradient
Electron transport chain primary electron donors
NADH and FADH2
Electron transport chain final electron acceptor
O2
Chemiosmosis
ATP synthase catalyses ATP synthesis using energy from the H+ gradient across the membrane (Chemiosmosis)
Enzyme consists of a basal unit that is embedded in the inner mitochondrial membrane and connected to a headpiece by a stalk
A stator bridges the basal unit and the head piece. Protons move through a channel between the basal unit and the stator. Making the stalk and headpiece spin. This reults in ATP synthesis.
Stator
Bridges the basal unit and the headpiece. Protons move through a channel between the basal unit and the stator. Making the stalk and the headpiece spin
Other sources of fuel for glycolysis
Carbohydrates: glucose and other sugars enter glycolysis directly
Proteins: amino acids
Ex. Alanine- pyruvate
Ex. Glutamate- ketoglutarate aspartate- oxaloacetate
Fats:
Glycerol + fatty acids
Glycerol - glycerol 3-phosphate
Fatty acids - acetyl-CoA
Each gram of lipid/ fat in the diet is how many kcal
9
Each gram of sugars or amino acids has how many kcal
4kcal
Is fermentation anaerobic respiration
NO
Fermentation
ATP-generating process which organic compounds act as both donors and acceptors of electrons; occurs in the absence of O2
Some organisms can survive without O2
Organisms survive on the energy base of 2 molecules of ATP per glucose molecule that come from glycolysis by substrate-level phosphorylation
Excess cytosolic NADH produced during glycolysis tends to be toxic to the cells
In fermentation, NADH molecules transfer their hydrogen atoms to organic molecules, thus regeneration of the NAD+ enables cells to keep glycolysis going
Alcoholic fermentation
Yeasts and certain bacteria convert the pyruvate produced by glycolysis to CO2 and ethanol
Lactate fermentation
In some fungi and bacteria, lactic acid, rather than alcohol is produced when NADH from glycolysis is oxidized
Lactic acid fermentation is used in the dairy industry to make cheese and yogurt
Human muscle cells can also make ATP by this metabolic pathway when oxygen is scarce
Anaerobic respiration
Terminal receptor isn’t oxygen
Used in bacteria and archaea which have respiratory electron transport chains in inner membranes (similar to mitochondria)
Anaerobic respiration used in
Used in bacteria and archaea which have respiratory electron transport chains in inner membranes (similar to mitochondria)
Anaerobic respiration electron receptors
SO4 2- (sulfate)
NO 3- (nitrate)
Fe 3+ (ferric iron)
Not as efficient an electron receptor, so aerobic respiration extracts a greater amount of energy
Aerobic life must balance the utility and reactivity of oxygen
oxygen is toxic bc it can steal electrons from other molecules
Process creates reduced forms called Reactive Oxygen Species (ROS)
ROS are reduced by enzymes Superoxide Dismitase and Catalase, and are protected from by antioxidants (vitamin C and E which also reduce ROS)
Some anaerobes die in O2 rich environments bc they don’t have SOD or catalase
