Lecture 23 Flashcards
To produce energy from glucose, microbes use two general processes:
cellular respiration and fermentation
After glycolysis, pyruvic acid can enter ________ or _______ ?
fermentation pathways, or it can go through the process of cellular respiration, where the pyruvic acid will be oxidized in the Krebs cycle with the resulting reduced electron carriers (NADH, FADH2) entering the e- transport chain
In the process of cellular respiration, the pyruvate that was produced by glycolysis will be oxidized completely to _______ using ________ .
CO2, using the Krebs cycle
The Krebs cycle was elucidated (made clear/explained) by __________ ?
Sir Hans Krebs a German-born British physician and biochemist
The Krebs cycle is the ______ stage of glucose metabolism, and can occur __________
2nd stage, and can occur without O2
-The Krebs cycle does not use oxygen, though it does stop in the absence of oxygen because it runs out of NAD and FAD.
Oxidation of Acetyl-CoA produces some ______ and the reduced coenzymes ________ and ________
ATP
NADH and FADH2 (which contain most of the energy originally stored in glucose)
Krebs cycle also part of the pathway to break down other metabolites like?
Fatty acids are converted into acetyl CoA by ________ . Whereas carbs are converted into acetyl CoA by ________ .
Other sugars, amino acids, fatty acids
- beta oxidation pathway
- glycolysis
Intermediates from the Krebs Cycle can go ________ and be used to ________ molecules such as ______ and _______ . Acetyl CoA can be used to synthesize _________ .
- in the other direction
- synthesize other molecules
- amino acids and fatty acids
- fatty acids
Pyruvic acid, the product of _______, cannot enter _______ directly. It must be converted to _________.
How does this happen? And what enzyme is the reaction catalyzed by?
This is also a ______ reaction. As ________ are removed from pyruvate during the reaction.
glycolysis, the Krebs Cycle
acetyl-CoA
- Pyruvic acid, a three-carbon molecule is decarboxylated (a carboxyl group is removed) to form the two carbon acetyl.
- pyruvate dehydrogenase, two electrons are removed and accepted by NAD+ resulting in the formation of NADH
The carboxyl group that is removed in the transition step from pyruvic acid to acetyl CoA is released as ______ ?
carbon dioxide
All dyhydrogenases catalyze what?
oxidation reactions. Enzyme that aids in the transfer of an electron to say NAD+ or NADP+
The oxidation of pyruvate is very _______ . Where is the energy transferred and used?
exergonic
Energy is transferred with the electrons to NADH and some is used to energize acetyl by adding coenzyme A (CoA) to acetyl
The acetyl group is attached via a ________ to what? final product of bridge/transition step.
high energy bond to CoA
this is a common intermediate. involved in the oxidation of amino acids, fats, and glucose (see slide 5)
Acetyl-CoA (now ready to enter the Kreb’s cycle)
First step in the Kreb’s cycle. What happens to acetyl-coA? And what is the end product (molecule) of this step?
CoA is removed, and the energy released is used to take the four carbon acetyl group and add it to oxaloacetic acid (2-carbon molecule).
Citric acid
Step 2: what happens to citric acid?
It is isomerized to get isocitric acid (6 carbon molecule)
Step 3: what happens to isocitric acid?
- it is decarboxylated COOH is removed, and CO2 is released into the environment
- also isocitric acid is simultaneously oxidized, and H atoms are picked up by coenzymes NAD+ to form NADH
-and isocitric acid becomes a 5 carbon compound: alpha ketoglutaric acid (5 carbon molecule)
NAD+ picks up what?
2 e- and 1 proton so becomes NADH
FAD+ picks up what?
2 e- and 2 protons so becomes FADH2
Step 4: alpha ketoglutaric acid is oxidized and decarboxylated to _________ . One extra process in this step than in the last.
Succinyl-CoA (4 carbon molecule)
-it is decarboxylated COOH is removed, and CO2 is released in the process. Also, it is oxidized, and NADH is formed. At the same time, CoA is added as a high energy bond compound.
Step 5: _______ is made from _______ , and ______ is released (which is where the energy to form ATP comes from). What is the end product here?
ATP is made from SLP, and CoA is released forming.... Succinic acid (4 carbon molecule)
Step 6: What happens to succinic acid? What is formed – final molecular structure?
Succinic acid is oxidized but the 2 e- and 2 protons are dumped onto FAD+ forming FADH2
-Fumaric acid is formed (4 carbon molecule)
Step 7: fumaric acid is rearranged to make _________
malic acid (4 carbon compound)
Step 8: final _______ step. Converts malic acid to ________ which is ready for what?
final oxidation step, converts malic acid to oxalacetic acid, which is ready to enter another round of the Kreb’s cycle
electrons are dumped onto NAD+ to form NADH
Overall summary, after two cycles for 2 pyruvic acid. What all is formed?
Bridge step forms 2 CO2, and 2 NADH
Krebs cycle produces - 4 CO2, 6 NADH, and 2 FADH2, 2 ATP from SLP in step 5
1 NADH can produce how many ATP?
1 FADH2 can produce how many ATP?
1 NADH = 3 ATP
1 FADH2 = 2 ATP
So, our sugar molecule has been burned, releasing _______, but where is all of the energy?
releasing CO2,
it is trapped in NADH, FADH2 (the e- carriers)
An ETC consists of a series of __________ ?
membrane bound carrier molecules (prosthetic groups) capable of oxidation and reduction used to transport energy from electrons in order to eventually drive chemiosmotic generation to produce ATP
In eukaryotes, the ETC is found where? In prokaryotes the ETC is found where?
In eukaryotes the ETC is found in the inner membrane of the mitochondria.
In prokaryotes the ETC is found in the plasma membrane.
The three classes of carrier molecules in the ETC
- Flavoproteins
- cytochromes
- ubiquinones or coenzyme Q (symbolized Q)
Flavoproteins. Ex?
have flavin, a coenzyme made from riboflavin, eg. Flavin mononucleotide (FMN) - first portion of ETC
Cytochromes, and what are the different cytochromes?
proteins with an iron containing (or heme) group, capable of altering as the reduced Fe2+ or oxidized Fe3+
-cyt b, cyt c1, cyt c, cyt a, cyt a3 are involved in the ETC
ubiquinones or coenzyme Q (symbolized Q)
these are small nonprotein carriers. Some
some organisms have proteins with _______ cluster. What do they do?
Fe-S clusters, which are best known for oxidation reduction reactions in ETCs
SEE SLIDE: two Fe/S centers both consist of Fe and S atoms bound to the protein through the sulfhydryl groups of cysteine residues
All ET chains achieve the same goals?
to release energy as electrons are transferred from higher-energy compounds to lower energy compounds
ETC in bacteria are ______
diverse. A single bacterium may have several types of ETCs
Electron carriers in the ETC are organized into 3 complexes
NADH dehydrogenase complex (first complex)
Cytochrome b-c1 complex
Cytochrome oxidase complex
In cellular respiration ______ is responsible for the most ATP made.
chemiosmosis
In prokaryotes, protons are pumped across the ________ to the ________ side.
plasma membrane from the cytoplasmic side to the periplasmic space
In eukaryotic cells, protons are pumped from the ________ side of the mitochondrial membrane to the __________ space
matrix side of to the intermembrane space
Step 1 of ETC. What happens?
NADH enters the ETC and meets with the NADH dehydrogenase complex where NADH is oxidized to NAD+. The electron from this oxidation is transferred to the first carrier molecule in the chain (flavoprotein called FMN for flavinmononucleotide), which gets reduced when it receives the electron
While the energetic electrons from NADH get passed down the ETC, some of the carriers in the chain do what? What are these carriers specifically called in regards to this action?
Does the first complex have a proton pump?
pump, or actively transport protons across the membrane. They are called proton pumps.
Yes the NADH dehydrogenase complex does pump a proton into the periplasmic space via FMN (this happens if the bacteria is Gram negative)
this one directional pumping of protons establishes what?
a concentration gradient and an electrical charge gradient
the periplasmic space becomes more positively charged than the cytoplasmic side creating an electrical charge gradient. This results in potential energy called _________ ?
The proton motive force (PMF)
The two processes ETC and OXPHOS are linked together by?
Chemiosmosis
See chart for the process of the electron passing between complexes (oxidation reduction process)
-When the electrons reach the ________ complex (last complex) what happens here?
cytochrome oxidase complex here the electrons join with protons and oxygen to form H20.
aerobic cellular respiration final electron acceptor?
anaerobic cellular respiration final electron acceptors?
aerobic = oxygen is the final e- acceptor
anaerobic = nitrate, nitrite, etc.
Protons want to move back into the cytoplasmic space from high to low concentration, so using the proton motive force they can travel through _________. What kind of phosphorylation is this?
special protein channels that contain an enzyme called ATP synthase
oxidative phosphorylation
ATP synthase found where in eukaryotes and where in prokaryotes
found in the cytoplasmic membrane in prokaryotes, and found in the inner membrane of the mitochondria in eukaryotes
how many protons moving through ATP synthase is enough to convert a molecule of ADP and Pi (inorganic phosphate) into a molecule of ATP
3 to 4 protons
one ATP synthase complex can generate _______ molecules of ATP each second
> 100 molecules of ATP
The ATP synthase can also _______ and _______ ATP to pump ions against an electrochemical gradient
reverse itself, and hydrolyze (breakdown by addition of water) ATP to pump ions against an electrochemical gradient
Membrane spanning portion of ATP synthase is called what? What does it comprised of?
Fo, comprising the ion channel
Soluble portion of ATP synthase called what? What is it comprised of?
F1, containing catalytic sites
Regeneration of NAD+ comes from? SO if you only go through glycolysis, eventually you will run out of NAD+
Kreb’s cycle, ETC or fermentation
anaerobic cellular respiration yields ______ energy than aerobic respiration
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