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68 Cards in this Set
- Front
- Back
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How does pyruvate get into the mitochondria? |
brought from cytosol into mitochondria via Mitochondrial Pyruvate Carrier (MPC) |
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Balanced reaction for acetyl CoA
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Pyruvate + CoA + NAD(+) ---> Acetyl CoA + CO2 + NADH catalyzed by Pyruvate dehydrogenase complex |
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What are the enzyme and cofactors names that catalyze conversion of pyruvate? |
1. Pyruvate dehydrogenase (E1) 2. Dihydrolipoamide transacetylase (E2) 3. Dihydrolipoamide dehydrogenase (E3) 1. Thiamine Pyrophosphate (TPP) 2. Lipoic Acid 3. Coenzyme A (CoA) 4. Flavin Adenine Dinucleotide (FAD) 5. Nicotinamide Adenine Dinucleotide (NAD+) |
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What is the function of E1? |
TPP is tightly bound to it; decarboxylates pyruvate to create hydroxyethyl-TPP. (ethanol with hydroxy carbanion that is attached to TPP) |
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What is the function of E2? |
Accepts the hydroxyethyl group from TPP and accepts acetyl group from lipoamide to create a thioester; gives acetyl group to CoA to make Acetyl CoA |
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What is the function of E3? |
Accepts electrons from reduced lipoamide and accepts electrons from reduced FADH2 |
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What are the two pathways that gets the reducing power of NADH into mitochondria? |
1. Glycerophosphate shuttle 2. Malate aspartate shuttle |
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Glycerophosphate shuttle |
NADH reduces dihydroxyacetone phosphate to 3-phosphoglycerol (aldolase step); product is a substrate for enzyme on mitochondria inner membrane that turns FAD into FADH |
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Malate aspartate shuttle |
NADH reduces oxaloacetate to malate which then enters inner mitochondria via malate/alpha-keotglutarate exchanger. electrons are trapped inside mitochondria now. Malate reduces NAD+ to NADH and then oxaloacetate gets converted to aspartate and transported out of the mitochondria |
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How is PDH regulated? |
PDH Kinase and PDH phosphatase |
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PDH Kinase regulation |
Increase in products (NADH and acetyl CoA) phosphorylates it (inhibits) |
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PDH Phosphatase regulation |
Activated by insulin and Ca2+, removes the phosphate on the pyruvate dehydrogenase which activates it |
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What is HIF-1? |
Hipoxy inducible factor; transcription factor that increases production of enzymes involved in glycolysis when O2 levels are low, including PDH Kinase (which phosphorylates E1 and shuts it down to keep pyruvate in the cytoplasm to make lactic acid instead of get brought to the mitochondria) |
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How do tumors encourage growth? |
HIF-1 stimulates production of specific growth factors (VEGF and EPO), allows for cell growth in hypoxic environments |
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What is EPO (erythropoietin)? |
Stimulates production of new erythrocytes (blood doping) |
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What is the overall reaction of the Citric Acid Cycle? |
Acetyl CoA + 3NAD+ + FAD + GDP + Pi + 2H2O ---> 2CO2 + 3NADH + FADH2 + 2H+ + CoA |
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Difference between synthase and synthetase |
synthase does not require ATP; synthetase does |
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What is the fate of the two carbons in Acetyl CoA? |
Fully oxidized to CO2 |
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Regulation of Citric Acid Cycle |
Citrate Synthase: citrate, NADH, succinyl CoA, ATP Isocitrate dehydrogenase: Inhibited by ATP, activated by Ca2+ and ADP Alpha ketoglutarate dehydrogenase: inhibited by Succinyl CoA, NADH, activated by Ca2+ |
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What is reduction potential? |
A measure of the potential energy of electrons; reflects how much a molecule prefers to be in the reduced state Positive means it prefers to be reduced; vice versa |
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What are the electron carriers in the ETC? |
Flavin mononucleotide (FMN), Iron-Sulfur proteins, Ubiquinone, cytochromes |
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Chain of events in Complex I and name |
NADH-Q Reductase Complex NADH reduces FMN, transfers electrons to FeS then reduces Q to QH2 pumps 4 H+ from cytoplasm to inter membrane space----> creates gradient |
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Q cycle |
transports to Complex III (Cytochrome C Reductase Complex) First half of cycle: QH2 donates 1 electron to Cytochrome 1 to form Q (releases 2 H+). QH2 can also donate the other electron to Q to form a Q radical Second Half of Cycle: QH2 recycles and can again give electron to cytochrome 1, also reduces Q radical to reform QH2 *takeaway: gives 1 electron to cytochrome c, gives 1 electron to re-reduce Q to create QH2 which goes back to Q pool |
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What is the function of cytochrome c? |
transfers the electrons from Complex III to Complex IV on the matrix sides of the membrane made up of a bunch of lysine (positive charges) |
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Complex IV and name |
Cytochrome c oxidase Complex Cytochrome binds to Complex IV's negative charges; transfers electrons which get transferred throughout protein until it reduces O2 to make H2O. 2 protons are made to use water, 2 more are pumped into inter membrane space |
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Complex II and name |
Succinate dehydrogenase, oxidizes succinate to fumarate and uses FADH2 feeds electrons to Q |
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What do chemical uncouplers do (DNP---> Dinitro Phenol) |
chemicals that Shuttle protons across the membrane and this dissipates the proton gradient that was built up by the pumps----> decrease in O2 consumption |
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Oligomycin and venturicidin |
inhibit atp synthase |
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What does it mean to have coupled mitochondria? |
The Proton gradient and ATP Synthase work together; electrons cannot flow if the proton gradient is too steep |
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Uncoupled mitochondria |
In brown fat; contains uncoupling protein 1 (UCP-1) which moves fatty acids into mitochondria and brings a proton inside as well which dissipates gradient. ATP is not produced because the animal isn't moving, so the energy is released as vibrational energy (heat) |
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ATP Synthase structure |
F1 and F0 substructures. |
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F1 subunit |
"knob"; contains 6 subunits, 3 are alpha and 3 are beta (catalytic part) all surrounding a gamma subunit with irregular shape |
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F0 subunit |
Integral membrane protein. When it rotates, the gamma subunit rotates and changes alpha and beta subunits structure (changes the way they bind ATP) |
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What does photosynthesis do? |
Converts light energy to chemical energy; done in the chloroplast |
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What happens during the light reaction? |
Chlorophyll absorbs blue light and electron gets excited; gets released. an oxidized acceptor (pheophytin) takes electron. transfer of electron generates a proton gradient. chlorophyll is now chlorophyll+. Produces 2 NADPH |
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How is electron replaced?
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Chlorophyll+ is very strong oxidant; splits water to replace electron, 4 H+ in lumen 2H2O ----> 4H+ + O2 |
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Light reaction total process |
1. chlorophyll in P680 absorbs red light, gets excited, reduced pheophytin in PSII. Chlorophyll now is chlorophyll+. Pheophytin reduces PQ 2. Reduced PQ which goes through Q cycle, transfers electron to cytochrome B6f (8H+ are pumped into lumen) 3. chlorophyll+ is strong oxidant, splits water to replace electrons. (OEC splits the water, gives the electron to the chlorophyll; manganese, calcium, and tyrosine are all involved) (takes 2 waters to make 1 oxygen) creates 4 H+ in lumen as well (balanced reaction) 4. cytochrome B6f transfers electron to PC; water soluble protein that shuttles electron to PSI. 5. electron from PC is given to another chlorophyll (P700) that gets excited again and reduced FeS complex, which reduces Ferredoxin. 6. Reductase transfers electron from Ferredoxin to make NADPH ****12 total H+ are pumped into lumen / 2 NADPH produced, 1 O2 |
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Location of product production |
ATP and NADPH are produced on the stroma side because proton gradient is pumping protons into the lumen |
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Product totals |
12 protons that get pumped produce 4 ATP. 3 protons go through ATP synthase to make 1 ATP. NADPH is analogous to NADH ~~ 2.5 ATP per NADPH. so 2 NADPH produced gives 5-6 ATP |
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Cyclic electron flow |
The flow of electrons from ferredoxin to PS1 that keeps cycling to produce ATP but no NADPH. |
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Calvin Cycle |
3 CO2 combines with 3 molecules of Ribulose 1,5 bisphosphate (RuBP) and cleaves to make 1,3 bisphosphoglycerate (BPG) and then gets reduced by NADH to make glyceraldehyde 3-phosphate (GAP). We now have 6 molecules of GAP; only 1 goes on to make sucrose, the other 5 are used to synthesize RuBP |
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What are the types of enzymes involved in the Calvin Cycle? |
Isomerase - converts to an isomer (ketose to aldose) aldolase - cleaves to make smaller molecules (6 carbon to 2 3-carbon molecules) or combines two smaller molecules to make a larger one phosphatase - removes a phosphate group transketolase - transfers 2 carbons to different carbohydrates Transaldolase - transfers 3 carbons epimerase - makes epimers of carbohydrates kinase - transfers phosphate from ATP to a substrate |
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How is RuBisCO regulated? |
1. Regulation by light a.) Regulated by pH; 8 is optimal. (This is because during the light reactions, protons are getting pumped into the lumen, so the pH is rising in the stroma) b.) Increase in [Mg2+] in the stroma. Positive regulator (activator) of RuBisCO activity. Since protons are being pumped into lumen, there is a build up of positive charge, which drives magnesium out of the lumen and into the stroma 2. Bisphosphatases Flow of electrons through PSI reduces Bisphosphatases and activates them; so activated bisphosphatases stimulates Calvin Cycle |
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How many Glyceraldehyde 6 Phosphates do you need to make Fructose-6-Phosphate? |
Requires two because GAP is only 3 carbons. So two cycles of the Calvin Cycle are required to make 1 F6P |
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Starch Synthesis Process (and location) |
1. Fructose-6-P -----> Glucose-6-P via Isomerase
2. Glucose-6-P---->Glucose-1-P via Mutase 3. Glucose-1-P---->ADP-Glucose via ATP 4. ADP-Glucose---->Amylose via Starch synthase ****in stroma of chloroplast |
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What are the two carbohydrate products from photosynthesis? |
Amylose (starch) and Sucrose (glucose and fructose) |
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Sucrose synthesis? and location |
1. GAP moves to cytoplasm 2. aldolase combines 2 GAP to make Fructose 1,6 Bisphosphate 3. Fructose 1,6 Bisphosphate--->Fructose-6-P via phosphatase 4. Fructose-6-P--->glucose-6-P via isomerase 5. glucose-6-P--->Glucose-1-P via Mutase 6. glucose-1-P--->UDP-glucose via UTP 7. enzyme combines UDP-glucose and fructose to make sucrose ****in cytoplasm |
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What is the Pentose-phosphate-pathway (PPP)? |
alternative way of oxidation of glucose in the cytosol. - generates NADPH for biosynthesis - generates pentoses for nucleotide biosynthesis - metabolizes pentoses |
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What are the products of the PPP? |
2 fructose-6-phosphates and 1 Glyceraldehyde-3-phosphate (GAP) |
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What is glycogen? |
Storage form of glucose; made up of glucose polymers |
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Where is most of the glycogen stored, and what is its function in each? |
Muscle: energy reservoir Liver: glucose reservoir (released into blood to supply other tissues) |
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Glycogen Breakdown Process |
Glycogen----->Glucose-6-Phosphate via 3 enzymes Glycogen phosphorylase, debranching enzyme (transfers and cleaves), Phosphoglucomutase |
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How does glycogen phosphorylase work? |
Cleaves the 1-4 linkages with a phosphate in chunks of 4 residues, produces Glucose-1-phosphate and glycogen chain |
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How does the debranching enzyme work? |
Step 1: Transfers a block of 3 residues to non-reducing end underneath Step 2: Cleaves the single remaining glucose left from the 1-6 linkage to produce glucose and a glycogen chain |
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How does phosphoglucomutase work? |
Enzyme contains a serine with a phosphate on it. Gives its Pi to C-6 on glucose to make Glucose-1,6-Bisphosphate. Then it takes the Pi off C-1 to yield Glucose-6-Phosphate |
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What is the fate of Glucose-6-Phosphate in the two locations? |
In the muscle, it will be turned into pyruvate to produce ATP In the liver, it will be dephosphorylized to make glucose |
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Glycogen synthesis steps |
1. Activation of glucose 2. Formation of 1-4 linkages (glycogen synthase and primer) 3. Formation of 1-6 linkages (branching enzyme) |
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What is the activation step? |
Glucose-1-phosphate is activated by UDP-Glucose-pyrophosphorylase and because UDP-Glucose |
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What is the second step in glycogen synthesis? |
Glycogen Synthase turns UDP-Glucose into into 1-4 linkages Needs a primer (glycogenin); glycogenin transfers glucose to itself and cuts of UDP, then transfers the glucose to glycogen via 1-4 linkages |
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What is the third step? |
Branching enzyme cleaves 1-4 bonded glucose residues every 7 residues and links these 7 residues to a chain via 1-6 linkage ~13 residues per branch ~2 branches per chain |
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How is UTP remade? |
ATP re-phosphorylates it to make ADP and UTP. Glycogen synthesis only uses 1 ATP |
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What are most glycogen-related diseases due to? |
Inability to breakdown glycogen (GSD; glycogen storage disease) |
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Von Gierke's Disease |
Most common; in the liver and kidney. malfunctioning Glucose-6-Phosphatase Low glucose levels in the blood, high glycogen levels in the liver = large liver, hypoglycemia |
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Anderson's Disease |
Branching enzyme disease. Less branching of glycogen = less reducing ends = slower degradation of glycogen = no energy, rarely survive past 5 |
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McArdle's Disease |
In the muscle; Glycogen phosphorylase disease Cannot cleave glycogen and activate it to make Glucose-1-Phosphate, so very little G-6-P can be made = less glycolysis = exercise intolerant |
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Hers' Disease |
In the liver; glycogen phosphorylase disease high glycogen levels in the liver, hypoglycemia |
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Why does glycogenolysis produce more ATP than glucose molecules going through glycolysis? |
Extracting glucose-1-phosphate from glycogen does not require the use of ATP, where as hexokinase needs to phosphorylate glucose in step 1 of glycolysis, which uses ATP. hense, you skip the investment step |
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Reaction of the PPP |
Stage 1 1 Glucose-6-Phosphate + 2 NADP+ ----> 1 Ribulose-5-Phosphate + 2 NADPH + CO2 ****multiply everything by 3 Stage 2 3 Ribulose-5-Phosphate -----> 2 Fructose-6-phosphates + GAP |
