BioChem Exam #4 Flashcards
1
Q
What are the overall products of Glycolysis?
A
- 2 ATP;
- 2 NADH + 2H+
- 2 Pyruvate
2
Q
What is the purpose of Glycolysis?
A
- Produce ATP;
- Provide building blocks for synthetic purposes
3
Q
What are the 2 pathways that Pyruvate can take after glycolysis?
A
- ANAEROBIC to Lactic Acid or Alcoholic Fermentation;
- AEROBIC to the Citric Acid Cycle
4
Q
What is Lactic Acid Fermentation?
A
- ANAEROBIC;
- Oxidation Reduction Rxn single conversion from pyruvate to lactic acid;
- USES 2 NADH + 2H+ to produce Lactic acid and 2NAD+;
- 2C pyruvate to 3C lactic acid
5
Q
What is the enzyme for Lactic Acid Fermentation?
A
Lactate Dehydrogenase =
- Give’s pyruvate electrons (reduce) to REMAKE NAD+
- NADH is oxidized;
- Found in Muscle Tissue and Lactic Acid bacteria
6
Q
What is Alcoholic Fermentation?
A
- ANAEROBIC;
- 2 step process that generates 2CO2 and 2 ethanol and 2 NAD+ from pyruvate;
- Yeast in bread and alcohol
7
Q
What is the first step of Alcoholic Fermentation?
A
- Pyruvate DECARBOXYLASE Rxn;
- Converts Pyruvate (3C) to acetylaldehyde (2C) with CO2 as a byproduct
8
Q
What is the second step of Alcoholic Fermentation?
A
- ALCOHOL DEHYDROGENASE;
- Oxidation reduction rxn of 2 acetylaldehye to 2 ethanol and 2NAD+;
- Reduces the acetylaldehye (add electrons) and oxidize NAHD + H+ (lose electrons) to make ethanol and REMAKE NAD+
9
Q
What is the purpose of both methods of Fermentation?
A
- Regeneration of NAD+ so that it can return to glycolysis and keep it going;
- Other products are TOXIC!
10
Q
How much ATP is made after both glycolysis and fermentation?
A
- STILL only 2 ATP that came from glycolysis;
- Fermentation makes NO energy
11
Q
What is the TCA (Citric Acid Cycle)?
A
- The AEROBIC, ENERGY generating of pyruvate;
- Occurs after glycolysis in the presence of Oxygen
12
Q
What are the products of the TCA cycle?
A
- GTP (analogous to ATP);
- NADH + H+
- 6 CO2;
- DOES NOT remake NAD+
13
Q
What is the purpose of the TCA cycle?
A
- Complete breakdown of glucose to CO2;
- Produce energy-containing molecules (GTP);
- Provide building blocks for other pathways (NADH)
14
Q
What happens in AEROBIC respiration after the TCA cycle?
A
- The (NAHD + H+) takes its extra electron to the electron transport chain to REMAKE NAD+;
- Electrons are then passed down the chain
15
Q
What happens with the Electron Transport Chain (ETC)?
A
- The energy from the electrons being passed down the down, drive the synthesis of ATP (energy);
- Electrons themselves (and protons) are picked up by Oxygen and H2O is produced as a waste product
16
Q
What is the purpose of the ETC?
A
- Regenerate NAD+;
- Drive ATP synthesis
17
Q
How many ATP are produced after AEROBIC Respiration (Glycolysis, TCA, and ETC)?
A
-36-38 total ATP per glucose molecule
18
Q
What are the WASTE products of AEROBIC respiration?
A
- Lactic acid
- Ethanol
- Gets rid of excess electrons
19
Q
What is the WASTER product of AEROBIC respiration?
A
- H2O
* Gets rid of excess electrons
20
Q
What are the final ELECTRON ACCEPTOR for ANAEROBIC respiration?
A
- Pyruvate;
- Acetaldehyde
21
Q
What is the final ELECTRON ACCEPTOR for AEROBIC respiration?
A
-Oxygen
22
Q
Why does NAD+ need to be regenerate so that Glycolysis can keep going?
A
- NAD+ needs to be in EXCESS to drive the generation of ATP forward and take on electrons (be reduced);
- WIthout enough, the Glyceraldehyde-3-PO4 dehydrogenase rxn will stop and glycolysis will stop
23
Q
Why would not having enough NAD+ stop the GLyceraldehyde-3-PO$ dehydrogenase rxn?
A
- This reaction is a Oxidation-Reduction ruxn;
- NAD+ is reduced so that Glyceraldehyde-3-PO4 can be oxidized to Glycerate-3-PO4 which will then generate ATP;
- Without this redox, glycolysis can’t continue and no ATP are created
24
Q
Why can’t the brain run off of ANAEROBIC pathways?
A
- Can’t handle the toxic products (ethanol and lactic acid);
- Needs high amount of energy constantly;
- Cells do not have fermenting capabilities
25
What is the Pasteur Effect?
- Breakdown of glucose in the PRESENCE of OXYGEN decreases drastically in yeast cells;
- Aerobically produce so much energy per glucose molecule, so need Fewer glucose to get the same/more energy;
- Yeast cells always need energy at a constant rate so energy quickly becomes excess with oxygen
26
Where does the TCA cycle take place?
-Mitochondria MATRIX (eukaryotic cells)
27
What are the components of the Mitochondria?
- Inner membrane (very selective);
- Outer membrane (not selective);
- Cristae (folds of the inner membrane);
- Intermembrane space
- MATRIX is enclosed by the inner membrane
28
The inner membrane of mitochondria is NOT permeable to what molecules?
- Sugars;
- NAD+, NADH;
- H+ (protons_
29
What is found in the matrix to allows for aerobic respiration and utilization of pyruvate?
- Matrix contains soluble enzymes that catalyze the oxidation of pyruvate;
- ATP synthase is found in the inner membrane which allows for the ultimate production of ATP through the ETC
30
How does pyruvate get into the mitochondria?
-Requires a transport mechanism due to selectivity of the membranes;
(Glycolysis had occurred in the cytoplasm)
31
How does Pyruvate enter into the TCA Cycle?
- ACTIVATED to Acetyl-CoA;
- Oxidative Decarboxylation rxn;
- Enzyme = Pyruvate Dehydrogenase Complex
32
How does the Oxidative Decarboxylation Rxn of PYRUVATE to ACETYL-CoA work?
- Pyruvate (3C) is oxidized (lose electrons);
- Then reacts with Coenzyme-A-SH;
- NAD+ is reduced (gains electrons) and produces NADH and H+;
- CO2 is also generated and removed from Pyruvate;
- Acetyl-CoA (2C) is produced
33
What are the rxn characteristics of the activation of Pyruvate to Acetyl-Co-A?
- Oxidative Decarboxylation Rxn (pyruvate oxidized, loses CO2);
- Irreversible, spontaneous;
- Large, negative delta G;
- Activation step!;
- Enzyme complex is controlled
34
What is the Pyruvate Dehydrogenase Complex?
- GROUP of soluble enzymes that ALWAYS work together in succession to turn pyruvate into acetyl-cowa;
- All-or-nothing, permanently linked;
- Highly efficient;
- Very large complex;
- All components are separate, but work hand-in-hand passing from one to the next;
35
How many catalytic enzymes are apart of the Pyruvate Dehydrogenase Complex?
- E1 (alpha, beta dimer, surround the core)
- E2 (forms the core);
- E3 ( dimer, "the glue between the others)
36
What are the two forms of Cofactors?
- Prosthetic group (permanently attached to enzymes)
| - Coenzymes (come in and out of attachment as needed)
37
What is the cofactor for E1?
-TPP (thiamine pyrophosphate) = PROSTHETIC;
| Need Thiamine to produce
38
What are the cofactors for E2?
- Lipoic acid = PROSTHETIC;
| - CoA-SH = COENZYME (need pantothenic acid to produce)
39
What are the cofactors for E3?
- FAD = PROSTHETIC (need riboflavin);
| - NAD+ = COENZYME (need niacin)
40
What are the REGULATORY components of the Pyruvate Dehydrogenase Complex?
- Pyruvate dehydrogenase kinase;
- Pyruvate dehydrogenase phosphate phosphatase;
* REGULATE E1
41
Why is the production of Acetyl-Co-A controlled?
-Because it is a BRANCH POINT compound for several pathways
42
What types of enzyme control regulate the Pyruvate Dehydrogenase Complex?
- Allosteric inhibitors (products);
- Location/Degree of organization in the cell (Mitochondria/All or nothingMulti-enzyme complex);
- Covalent modification (adding/removing PO4 to E1)
43
How is the Complex regulated ALLOSTERICALLY?
- E2 is INHIBITED by AcCoA;
- E3 is INHIBITED by NADH
* Regulated by the PRODUCTS of that rxn, b/c it is a branch point!
44
How is the Complex regulated by COVALENT MODIFICATION at E1?
- E1 ALONE is ACTIVE;
- Adding PO4 makes E1 INACTIVE;
- Reversible by another enzyme;
- Totally turns E1 OFF (typical covalent modification)
45
How is PO4 added to E1 to make it INACTIVE?
- Enzyme = Pyruvate Dehydrogenase Kinase removes a PO4 (Pi, inorganic phosphate) from ATP and ADDS it to E1 and leaving ADP;
- Allosteric control of Kinase
46
What is the INACTIVE form of E1?
-Pyruvate Dehydrogenase Phosphate
47
How is E1 REACTIVATED?
- Enzyme = Pyruvate Dehydrogenase Phosphate Phosphatase;
- PO4 (Pi) is REMOVED creating a free inorganic phosphate (Pi) and ACTIVE E1;
- Allosteric control of Phosphatase
48
How is Pyruvate Dehydrogenase KINASE (regulator enzyme) controlled?
- Allosteric;
- ACTIVATED by Acetyl-CoA and NADH;
- INHIBITED by CoA and NAD+
49
How is Pyruvate Dehydrogenase Phosphate PHOSPHATASE (regulator enzyme) controlled?
- Allosteric;
| - ACTIVATED by ADP (low energy)
50
Why do the INHIBITORS of E2 and E3 (Acetyl-CoA and NADH) ACTIVATE the Kinase regulator?
-When the complex needs to be turned OFF, Acetyl-CoA and NADH are present to both STOP E2 and E3, but also activate pyruvate dehydrogenase Kinase, which then STOPS E1
51
Why is the Pyruvate Dehydrogenase Complex so carefully controlled?
- Because creating Acetyl-CoA from pyruvate is the commitment step AWAY from any glucose synthesis or glycolysis!;
- NO more Carbons are available for net Carb synthesis;
- This can only occur when the brain is happy and has adequate glucose to function
52
Why is the conversion from pyruvate to acetyl-coA important?
- Irreversible, spontaneous, large neg. delta G reaction;
- Activation step for several pathways;
- Commitment step to make Acetyl-CoA = NO MORE CARBS
53
Where else can Acetyl-CoA come from?
- Carbs to pyruvate to Ac-CoA;
- Breakdown of some amino acids (can be used for energy, but not as glucose);
- Fatty acid breakdown
54
What else can Acetyl-CoA be used to make?
- Enter TCA cycle to make energy;
- Fatty acid synthesis;
- Some amino acid synthesis;
- Synthesis of some steroids and other lipids
55
What are the roles of the TCA cycle?
1. Oxidized acetyl (Carbon) group to CO2 and H2O;
2. Produce biosynthetic intermediates (building blocks for other paths);
3. Recover energy as NADH, FADH2, and GTP (ATP)
56
How is energy recovered through the TCA by NADH and FADH2?
-They are oxidized and give electrons the the ETC where oxidative phosphorylation can create ATP from the electrons energy
57
What is the FIRST step with Acetyl-CoA to start the TCA cycle?
- 2C Acetyl-CoA combines with 4C oaxaloacetate (OAA) to create a 6C Citrate;
- Bond between the Carbonyl C of OAA and the activated CH3 of Ac-CoA;
- Enzyme = Citrate Synthase;
- Large, neg. delta G rxn
58
How the small CH3 group on Ac-CoA made reactive?
-The high energy contained in the THIOESTER bond with Sulfur and Coenzyme A n the Ac-CoA withdraws electrons making it more reactive
59
What are the 2 roles of Citrate Synthase?
- Removes the SH-CoA from the acetyl group of Acetyl-CoA;
- And then combines the 2C acetyl group with the 4C OAA;
- Makes Citrate (6C)
60
How is the CItrate Synthase Reaction controlled?
* Commitment to TCA!;
1. Allosteric;
2. Substrate conc. of OAA
61
How is the Citrate Synthase Rxn controlled Allosterically?
-INHIBITED by ATP, NADH, Succinyl-CoA
62
How the Citrate Synthase Rxn controlled by Substrate conc OAA?
- The conc. of OAA is VERY LOW, so any change in the conc. at ALL causes as Large change;
- Not much to work with in the first place
63
Why does the Citrate Synthase Rxn release so much energy as heat?
- The large negative delta G value is NOT stored as energy, but it needed to pull the cycle around and allow it to continue;
- The delta G value to convert from L-malate to OAA is very positive and needs the extra energy to occur
* DIRECT ENERGY COUPLING REACTION
64
What is CITRATE (6C) converted to?
- ISOCITRATE (6C);
| - Undergoes a rearrangement of an (-OH) group from the 3rd to 4th carbon
65
How is Citrate converted to Isocitrate?
Enzyme = ACONITASE:
- Rearrangement occurs by the removal of an H2O that swings around the molecule and is put back on in the backwards position with the help of IRON (Ferris Wheel mechanism);
- Positive delta G, so PREFERES THE REVERSE rxn
66
Why does Aconitase always move the -OH from the 3rd to the 4th carbon?
- Aconitase is a STEREOSPECIFIC enzyme;
- Even though Carbon of citrate was NOT chiral, the stereospecifcity of Aconitase always moves the -OH down from the 3rd to 4th carbons
67
What is ISOCITRATE (6C) converted to?
- ALPHA KETOGLUTARATE (5C);
- Dehydrogenase and Oxidative decarboxylation rxn that REMOVES CO2 and uses NAD+ to remove electrons (dehydrogenase or redox rxn);
- Products are CO2 and (NADH + H+)
68
How is Isocitrate converted to Alpha-KG?
Enzyme = ISOCITRATE DEHYDROGENASE
- Decarboxylation removal of CO2 to convert 6C to 5C;
- Reduction of NAD+ to NADH + H+ to remove electrons (;
- IRREVERSIBLE;
- Allosterically increased by ADP/NAD+;
- Allosterically inhibited by ATP/NADH
69
What is Alpha-KG converted to?
- SUCCINYL-CoA (4C);
| - Removal of CO2 (oxidative decarboxylation) and electrons (dehydrogenase) to ADD CoA-SH
70
How is Alpha-KG converted to Succinyl-CoA?
Enzyme = Alpha-KG dehydrogenase complex;
- Activation step to create a high energy THIOESTER bond between Carbon and Sulfur of Coenzyme A;
- Reduction reaction to remove electrons with NAD+ to (NADH + H+)-
- Decarboxylation to remove CO2 makes 5C (KG) into 4C;
- IRREVERSIBLE rxn
71
How is the Alpha-KG dehydrogenase complex controlled?
- ALLOSTERICALLY = increased by ADP/NAD+; inhibited by ATP/NADH;
- LOCATION or ORGANIZATION of the complex (all or nothing);
- NO covalent modification
72
What is the purpose of creating the thioester bond of Succinyl-CoA?
-Creates a HIGH ENERGY bond creating storage in the substrate (S-CoA) for the next reaction to be able to generate energy
73
What other conversion can occur at Alpha-KG?
- Entrance of or Exit to Glutamic Acid (amino acid);
- An intermediate of the TCA cycle that can be used as a building block for other processes (like amino acid synthesis);
- Glutamic acid can also enter the cycle and be broken down and eventually converted to energy
74
What is Succinyl-CoA (4C) converted to?
- SUCCINATE (4C);
- Substrate level phosphorylation!!! to create ENERGY in the form of GTP;
- Succinate is SYMMETRICAL
75
HOw is Succinyl-CoA (4C) converted to Succinate (4C) and energy made?
Enzyme = Succinyl-CoA Synthase ;
- Freely REVERSIBLE rxn;
- CoA-SH (coenzyme) is removed releasing the HIGH energy in the bond;
- GDP uses the energy released to bind a Pi (organic phosphate) and create energy = GTP
76
Why can the energy from the Succinyl-CoA Synthase reaction be STORED as energy?
- The energy is not needed in the reaction at that point (unlike between OAA and citrate), so it can be stored in an energy compound for the body to use
* ENERGETIC COUPLING Rxn using a high-energy intermediate
77
What is Succinate (4C) converted to?
-FUMARATE (4C);
Enzyme = Succinate Dehydrogenase:
-Removal of electrons of using FAD and REDUCING it to FADH2 (gain electrons);
-Succinate is OXIDIZED (losing electrons);
-NO carbons removed, creates a DOUBLE Bond
-Freely REVERSIBLE rxn
78
What make Succinate Dehydrogenase different from other enzymes?
-It is the only enzyme that is bound to the inner mitochondrial membrane
79
What happens to the FADH2 created in the conversion of Succinate to Fumarate?
FADH2 is unstable and immediately loses its electrons to the ETC
80
What is Fumarate (4C) converted to?
L-MALATE (4C);
Enzyme = FUMARASE;
-Hydration reaction (Adding water);
-Freely REVERSIBLE rxn
81
What is L-Malate converted to?
-OAA (4C);
Enzyme = MALATE DEHYDROGENASE;
-Uses NAD+ (reduced) to take on electrons and become (NADH + H+)
-L-Malate is oxidized as is Loses electrons to create a double bond and become OAA;
-*Greatly Prefers the REVERSE!
82
What then happens to the OAA (4C) generated from the Cycle?
-OAA is combined with Acetyl-CoA through the Citrate Synthase Rxn to create Citrate for the commitment step to start the TCA cycle over again;
OR
-OAA can be an exit/entrance point to the cycle for Aspartic Acid (amino acid)
83
What effect does the Malate Dehydrogenase rxn so greatly preferring the REVERSE have on the cycle?
- There is very low concentration of OAA;
- OAA is required to combine with Acetyl-CoA to start the TCA cyle, so OAA serves as a [substrate] control of the Citrate Synthase Rxn;
- Causes the the release of the large amount of energy that comes from the Citrate Synthase Rxn to be released as heat (not able to be stored) to simply drive the rxn and creation of OAA
84
What the the 3 reactions/changes to alter the 4 carbon compound of the TCA back to the starting OAA?
```
Succinate:
1. Removes H's - Oxidation
Fumarate:
2. Add H2O - Hydration
L-Malate:
3. Remove H's - Oxidation
OAA
```
85
Why can animals use the 2C Acetyl-CoA to directly make Glucose?
(NO NET CARBS)
- Even though there is a high energy bond in the 2C's of Acetyl-CoA they CANNOT be made into glucose;
- Acetyl-CoA cannot be an exit point to glucose because 2 carbons that enter the cycle are LOST through decarboxylation to make the cycle proceed;
- Lost to convert Isocitrate to Alpha-KG (5C), and then again to convert Alpha-KG to Succinyl-CoA (4C)
86
What intermediates of the TCA cycle could be used to exit and create Glucose?
-Only compounds that contain 4 carbons
87
Why can PLANTS use Acetyl-CoA to create glucose?
- Glyoxylate shunt;
- Plants bypass the steps to go from Isocitrate (6C) to Alpha-KG (5C) to Succinyl-CoA and then Succinate;
- They go DIRECTLY from Isocitrate to Succinate, so they don't LOSE the 2 carbons that entered the cycle;
- The 2 carbons that are then lost in this conversion (6 to 4 C's) and removal of a high energy bond can combine with more AC-CoA, be converted to OAA and then yield 6C glucose-
- Enzyme = Succinate Dehydrogenase
88
Why do plants use this shunt?
- Plants use seeds for reproductions;
- Cell walls are made of glucose (cellulose) so cells can divide and grow in the dirt, so they must be able to always make glucose;
- They store energy as fatty acids then use them for energy and synthesis
89
What enzymes are controlled in the TCA cycle?
1. Pyruvate Dehydrogenase Complex
2. Citrate Synthase
3. Isocitrate Dehydrogenase
4. Alpha-KG Dehydrogenase Complex
90
How is the Pyruvate Dehydrogenase Complex (enzyme) controlled?
- Allosterically
- Covalent Modification
- Location/Organization = Mitochondria/All-or-Nothing complex)
91
How is Citrate Synthase (enzyme) controlled?
- Allosterically (inhibited ATP, NADH, Succinyl-Co-A)
| - Concentration of the Substrate (OAA)
92
How is Isocitrate Dehydrogenase controlled?
-Allosterically
(Increased by ADP, NAD+)
(Inhibited by ATP, NADH)
93
How is the Alpha-KG Complex controlled?
- Allosterically = (Increased by ADP, NAD+) and (Inhibited by ATP, NADH)
- Location/Organization
- NO Covalent Modification
94
What makes the TCA cycle AMPHIBOLIC?
- It is BOTH a breakdown and synthesis cycle;
| - Catabolic (enter) and Anabolic (exit) Pathways
95
What is the Catabolic pathway of the TCA?
1. Carbs or amino acids are converted to Pyruvate;
2. Pyruvate, fatty acids or amino acids converted to Acetyl-CoA
3. TCA cycle is then entered with Acetyl-CoA and energy (GTP) is created along with (NADH + H+) and FADH2
96
Where all can Amino Acids enter the TCA cycle to be used for Catabolism (breakdown)?
- Pyruvate;
- Acetyl-CoA;
- Alpha-KG;
- OAA;
- Succinyl-CoA
97
What is the Anabolic pathway or Exit points of the TCA?
1. Alpha-KG
2. OAA
3. Succinyl-CoA
4. Acetyl-CoA
5. Pyruvate
98
What EXITS at Alpha-KG?
Glutamic acid and then becomes other amino acids
99
What EXITS at OAA?
- Aspartic Acid to become other amino acids;
- PEP to become amino acids
- Straight to Glucose
100
What EXITS at Succinyl-CoA?
-Combines with Glycine to make Heme
101
What EXITS at Acetyl-CoA?
- Amino acids
- Fatty acids
- Steroids
- NO glucose!!
102
What EXITS at Pyruvate?
- Amino acids through transamination (carboxyl replaced with amine);
- Creates ALANINE
103
What makes the TCA cycle ANAPLEROTIC?
- It performs reactions that refill the INTERMEDIATES of the metabolic pathway;
- "Filling up"
104
What is the Primary Anaplerotic reaction in animals?
-Convert pyruvate (3C) to OAA (4C) by adding CO2;
Enzyme = Pyruvate Carboxylase;
-CO2 is added with the help of an energy from breaking ATP to ADP and Pi
*Requires BIOTIN, ATP and a carbon source for carboxylation
105
How are Amino Acids used to in Anaplerotic reactions?
```
-Enter the cycle and provide it with needed Carbons;
Enter at =
-Alpha-KG (Glutamic Acid)
-OAA (Aspartic Acid)
-Succinyl-CoA
-Fumarate
```
106
What are the two processes involved in the Electron Transport Chain?
- Electron Transport COUPLED with Oxidative Phosphorylation;
| - Only occurs in AEROBIC Respiration
107
What is Oxidative Phosphorylation?
the metabolic pathway in which the mitochondria in cells use their structure, enzymes, and energy released by the oxidation of nutrients to reform ATP.
108
What is the purpose of the ETC?
After glycolysis and TCA there are leftover electrons in the form of NADH and FADH2 so...
1. The carriers need to be recycled and NAD+ and FAD regenerated so that glycolysis can continue;
2. Obtain Energy in the form of ATP
109
Why is the high energy output of the ETC so vital?
- We only keep about 50grams of ATP present in our body as avaible energy at any given time, but require the breaks down of a couple hundred kilograms just to maintain our weight;
- Lots of recycling!!
110
Where does the ETC take place?
- The components are embedded in the Inner Mitochondrial Membrane;
- The membrane is very highly folded with carriers throughout, which allows for a lot simultaneously electron transport, recycling, and generation of ATP
111
What are the components of the ETC?
* Some requires PROTONS, and some do not!
1. NADH Dehydrogenase
2. [Fe, S] Centers
3. Coenzyme Q
4. Cytochromes (b1, c1, c, a/a3)
112
What is NADH Dehydrogenase of the ETC?
- First ETC enzyme;
- Regenerates NAD+ form (NADH + H+);
- Has FMN (flavin mononuceotide) as a permanently attached prosthetic group;
- REQUIRES Protons;
- Passes electrons on the [Fe,S] centers
113
What are [Fe,S] centers of the ETC?
- ETC enzymes that consist of Iron and Sulfur in a variety of ratios;
- Non-Heme iron;
- Transfers electrons by only changing the ionization of the Fe (Fe3+ to Fe2+);
- NO Protons required!
114
What is Coenzyme Q (Ubiquione) of the ETC?
- Found in almost all eukaryotic cells;
- Entrance point to the ETC for electrons from FADH2
- REQUIRES Protons
115
What are Cytochromes of the ETC?
| b1, c1, c, a/a3
- Proteins made from linked amino acids;
- All are bound to the Intermitochondrial Membrane Ring;
- Iron-porphyrin ring (heme protein);
- DIFFER in their amino acid sequences and porphyrin rings;
- ALIKE ionization of F3+ and Fe2+
- NO Protons required
116
What does the differences in the Cytrochromes do for the ETC?
- Each has a different Redox Potential = Oxygen affinity or ability to grab electrons;
- Difference allows the passing of electrons from one carrier to the next;
- Affinity gets HIGHER as you go down through the ETC therefore allowing electron flow all the way to O2 and the release of the excess
117
What is the order of the use of Cytochromes?
- b;
- c1;
- c;
- a/a3
118
What is Cytochrome C?
- Ancient/Preserved structure;
| - Much of the protein sequence is very similar across organisms
119
What is Cytochrome a/a3?
- Cytochrome Oxidase;
- FINAL Step of the ETC;
- ONLY cytochrome that reacts with O2;
- 2 linked together because must pass 4 electrons at a time to molecular oxygen to avoid bad products and make 2 H2O
120
What happens when Cytochrome a/a3 (Cytochrome Oxidase) is blocked/inhibited?
- Cannot get rid of electrons by finally passing them to O2;
- Not getting rid of the excess electrons causes the brain cells to immediately start to die = NAD+ is not regenerated, so glycolysis can't provide the brain with glucose!;
- BLOCKED by Cyanide binding (like you're not breathing);
- INHIBITED by Carbon Monoxide and Hydrogen Sulfide (H2S)
121
What compounds donate electrons to the ETC with NADH?
- Pyruvate
- Iso-Citrate
- Alpha-KG
- Malate
- NADPH
- Glyceraldehyde-3-PO4 (malate aspartate shuttle from glycolysis/cytoplasm)
122
What compounds donate electrons to the ETC with FADH2?
- Succinate dehydrogenase (only membrane bound rxn);
| - Glyceraldehyde-3-PO4 (glycerol-PO4 shuttle from cytoplasm)
123
How is the ETC arranged to that electrons are shuttled through it?
- Enzymes are grouped in "sites" that work together;
- Cytchromes form the bridging compounds between the complexes;
- Moves "downhill" energetically to O2 with increase redox potential from one complex to the next
124
Complex 1 of the ETC
- NADH Dehydrogenase to [Fe,S] center;
| - Then CoQ (bridge)
125
Complex 2 of ETC
- Entrance of electrons with FADH2!;
- FADH2 to [FE,S] centers;
- Then CoQ (bridge)
126
Complex 3 of ETC
- NADH electrons and FADH2 electrons come together at CoQ;
- Cyt B to [Fe,S] to Cyt C1;
- Then Cyt C (bridge)
127
Complex 4 of ETC
- Cyt. a/a3;
| - Then finally passed on to O2 and water released as waste
128
How many ATP are generated at each site of the ETC?
- Site 1 (NADH to CoQ) = I ATP;
- Site 2 (CoQ to Cyt C) = 1 ATP;
- Site 3 (Cyt C to O2) = 1 ATP
129
What is the energy generation of the ETC?
- LARGE NEG. Delta G with lots of energy released;
- Entering at NADH gives 3 ATP;
- Entering at FADH2 gives 2 ATP
- Remainder of the energy not stored at ATP is let go as heat (reason we get hot!)
130
What is the mechanism of Oxidative Phosphoryaltion?
- Creation of a high energy PO4 bond;
- Tells where the ENERGY came from to make the high energy bond;
- Creates ATP using energy from Oxidation Reduction Rxns COUPLED with the Transport of Electrons (separate, yet linked, processes)
131
How can Oxidative Phosphorylation be UNCoupled?
- Oxidation-Reduction and Electron transport NO longer working together;
- Arsenate;
- Some Antibiotics;
- Mechanically (test tube)
* Makes the membrane permeable for the H+ ions so they don't need the proton gradient
132
What are the structures involved in Oxidative Phosphorylation?
- Electron transport happens along the Inner Mitochondrial Membrane that surrounds the Matrix;
- ATP Synthesis 'bulb' sticks out into the Matrix;
- TOGETHER the Electron Transport and ATP Synthesis make up the enzyme ATP SYNTHASE (ATPase)
133
What is ATP SYNTHASE?
- Enzyme of the ETC that provides energy for the cell to use through the synthesis of AT;
- Energy is released as hydrogen ions (H+), moving down an electrochemical gradient from the inter-membrane space into the matrix in mitochondria.
134
What is Chemiosmotic Coupling?
- Process that COUPLES the Electron Transport Chain with to ATP formation;
- PROTON GRADIENT
135
How is energy generated from the Chemiosmotic Coupling of the ETC and ATP formation?
- Electrons pass through the ETC releasing energy;
- A proton gradient is established across the Inner Mitochondrial membrane pumping out H+ into the inner membrane space;
- The proton gradient drives the protons (H+) to move down the gradient, releasing the energy that is in turn captured in the terminal phosphate bonds of ATP (between ADP and Pi)
136
What are the different gradients for Chemiosmotic Coupling?
- Proton gradient
- pH gradient
- Charge gradient
- Electrochemical gradient
137
What drives the movement of electrons down the gradient?
- The NET movement of protons from the matric to the intermembrane space;
- All depends upon some electrons carriers REQUIRING protons and other NOT requiring them
138
What happens when a carrier REQUIRES protons?
-The flow of electrons is oriented on the side of the MATRIX so that H+ can be pulled into the membrane by the 'bulb' of ATP Synthase
139
What happens when a carrier does NOT NEED protons?
- The flow of electrons is oriented on the side of the Intermembrane Space and the H+ are pushed out where they will stay;
- Impermeable membrane won't let those go back
140
What would make the ETC stop working and what would occur?
Without Oxygen (final electron acceptor)
- NO proton gradient;
- NO ATP;
- NO regeneration of NAD+;
- Can't get rid of excess electrons, so ETC will be "clogged" up;
- TCA will STOP;
- and without ANAEROBIC regeneration of NAD+, glycolysis will STOP;
- Brain cells begin to die in 2-3 minutes
141
What is the evidence supporting Chemiosmotic Coupling?
1. Inner membrane must be INTACT for oxidative phosphorylation to occur;
2. Inner membrane is IMPERMEABLE to H+, OH-, K+ and Cl-;
3. Uncoupling agents increase PERMEABILITY of membrane to H+ = No longer need gradient to link the processes
142
What are the uses of the changing H+ membrane gradient?
1. ATP Synthesis;
2. Transport of ADP and ATP in/out of mitochondria (don't want to use ATP energy before it even gets out);
3. Rotation of bacterial flagella;
4. Heat (Brown fat on infants and hibernating animal to produce heat through a permeable membrane)
143
What is the affect of the Inner Membrane becoming permeable?
- Membrane permeability and allowing H+ across does NOT immediately cause a lack of NAD+ (unlike cyanide), just less ATP;
- NAD+ is still being regenerated by ETC;
- Still gain some energy from TCA and glycolysis, but just a lot less!
- Substrate Level Phosphorylation CONTINUES but NOT Oxidative Phosphorylation (Proton gradient)
144
How are electrons of glycolytic products in the cytoplasm transferred to use in the mitochondria?
Transfer of glycolytic NADH (cyto) to the ETC (mitochondria) =
1. Glycerol Phosphate Shuttle
2. Malata-Aspartate Shuttle
145
What is the Glycerol Phosphate Shuttle?
- Occurs in the MUSCLE;
- One-step process;
- One direction into the Matrix;
- Yields 2 ATP per cytoplasmic NADH;
- Produced electron carrier is FADH2
146
Mechanism of Glycerol Phosphate Shuttle
- DHAP is REDUCED by from NADH (oxidized) to create NAD+ and Glycerol-PO4;
- Transporter then moves Glycerol-PO4 across the membranes and into Matrix;
- FAD is REDUCED taking electrons from the Glycerol-PO4 and becoming FADH2 and regenerating DHAP;
- FADH2 takes electrons to ETC;
- DHAP is moved back out of the mitochondria
147
Why is DHAP needed to utilize cytoplasmic NADH?
- NADH CANNOT go across the membranes!;
- Only take the electrons that are apart of NADH and "shuttle" those into the cell;
- Actual NADH compound is NOT ever taken into mitochondria
148
What is the Malate-Aspartate Shuttle?
- Occurs in the LIVER;
- More complex, multi-step;
- Reversible process (can take electrons out and not just take them into mito);
- Yields 3 ATP per cytoplasmic NADH
- Produced electron carrier is NADH
149
Mechanism for the Malate-Aspartate Shuttle
- Cytoplasmic NADH + H+ uses an electron carrier to take the electrons across the membranes;
- Once inside the matrix, NADH + H+ is regenerated as the electron carrier to go to the ETC
150
What are NADH and FADH2 in relation to the shuttles?
- Isozymes;
- They are both electron carriers that take electrons from glycolytic NADH to the ETC, but one is found in the MUSCLE (FADH2) and the other the LIVER (NADH)
151
Hexokinase...
| Glycolysis
USES 1 ATP
152
PFK...
| Glycolysis
USES 1 ATP
153
Glyceraldehyde-3-PO4-dehydrogenase...
| Glycolysis
Generates 2 NADH
| -Ultimately MAKE 4 or 6 ATP
154
Phosphoglycerol Kinase...
| Glycolysis
MAKES 2 ATP
155
Pyruvate Kinase...
| Glycolysis
MAKES 2 ATP
156
Total # of ATP's per glucose from Glycolysis
NET 6 or 8 ATP made
157
If electrons of NADH enter Mitochondria with Glycerol-PO4 Shuttle...
[Muscle]
| -Electrons passes to FADH2 = MAKES 2 ATP/cyto NADH
158
If electrons of NADH enter Mitochondria with Malate-Aspartate Shuttle...
[Liver]
| -Electrons passed to NADH = 3 ATP/cyto NADH
159
Pyruvate Dehydrogenase Complex...
| TCA
1 NADH = 3 ATP
160
Isocitrate Dehydrogenase...
| TCA
1 NADH = 3 ATP
161
Alpha - KG Dehydrogenase...
| TCA
1 NADH = 3 ATP
162
Succinyl-CoA Synthetase...
| TCA
1 GTP = 1 ATP
163
Succinate Dehydrogenase...
| TCA
1 FADH2 = 2 ATP
164
Malate Dehydrogenase...
| TCA
1 NADH = 3 ATP
165
How many ATP are created per PYRUVATE in the TCA?
```
15 ATP
(Goes around twice, so double for a total of 30, with 2 pyruvate)
```
166
How many ATP are created per GLUCOSE?
30 ATP
| From 2 pyruvate per glucose
167
What is Gluconeogenesis?
Formation of Glucose from NONCARB precursors
168
What is the Purpose of Gluconeogenesis?
1. Maintain blood glucose and resupply the body when no dietary source or glycogen store available
2. Re-use Lactic Acid produced in the muscle from Anaerobic respiration
169
What cannot be converted to use as Glucose with Gluconeogenesis?
- Acetyl-CoA;
| - Fatty acids - they are broken down to Acetyl-CoA so no use as glucose!
170
How is Lactic Acid recycled to be used as glucose?
- Muscle performs Anaerobic respiration and converts glucose in the muscle to lactic acid in the absence of O2;
- Lactic acid is then sent through the blood to the LIVER where it is converted back to Glucose (GLUCONEOGENESIS);
- Liver can then send the glucose into the blood;
* Doesn't occur in cells - in tissues
171
Why is Gluconeogenesis not just the Reverse of Glycolysis?
- Glycolysis has a NEGATIVE delta G and the simple reverse would be a POSITIVE delta G, but all reactions REQUIRE a NEGATIVE to occur;
- Must overcome the 3 irreversible steps of glycolysis for gluconeogenesis
172
What are the 3 irreversible glycolysis steps that Gluconeogensis must by-pass?
1. Hexokinase
2. PFK
3. Pyruvate Kinase
* In Glycolysis they release energy to drive the rxn, in the reverse they would REQUIRE too much energy
173
How does Gluconeogenesis by-pass PYRUVATE KINASE?
- 2 step process from Pyruvate to OAA to PEP;
1. Pyruvate Carboxylase Rxn
2. PEP Carboxykinase Rxn
174
What is the Pyruvate Carboxylase Rxn?
- Converts Pyruvate Carboxylase to OAA;
- Adds CO2 with the help of energy from ATP and Biotin;
- Negative delta G
175
What is the PEP Carboxykinase Rxn?
- Converts OAA to PEP with energy from GTP and removal of CO2;
- Positive delta G
176
What other compounds can by-pass Pyruvate Kinase rxn for Gluconeogenesis?
- Lactic Acid and Amino acids can enter at PYRUVATE;
| - Amino acids and TCA intermediates can enter at OAA
177
How does Gluconeogenesis by-pass PFK?
Fructose-1,6-bisphosphatase Rxn =
- Removes the PO4;
- Negative delta G
178
How does Gluconeogensis by-pass Hexokinase?
Glucose-6-Phosphatase Rxn =
- Removes the PO4
- ONLY IN THE LIVER
179
What compounds can be used to produce glucose with Gluconeogenesis?
- Lactic acid
- Gycerol (Lipid Backbone, NOT the fatty acid that became acetyl-coa)
- Glucogenic Amino Acids
180
What are Glucogenic Amino Acids converted to so they made be used for glucose?
- Pyruvate to OAA to glucose
- OAA to glucose
- TCA intermediates (with at least 4 carbons) to OAA to glucose
181
What are Amino acids that end up as Acetyl-CoA?
- Ketogenic and create Ketone Bodies that can supply the muscles
- CANNOT make Glucose!
182
What reaction of Glycolysis turns highly favorable in the reverse for Gluconeogenesis?
- Aldolase!;
- Very large positive delta G in the forward, but in the reverse becomes very negative and helps drive the reformation of glucose
