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96 Cards in this Set
- Front
- Back
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Glycogenolysis:
1. Major enzyme 2. In what tissue does the mentioned enzyme save 1 atp for glycolysis? 3. Where does glycogen phosphorylase stop? |
1. Glycogen phosphorylase
2. Muscle tissue 3. 4 units before branching point |
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Glycogenolysis:
1. Name of the debranching enzyme 2. What does it do 3. What does Amylo-alpha-1,6-glycosidase do? |
1. 4 alpha glucanotransferase
2. Moves 3 of the 4 glucose units to another non reducing end 3. hydrolysis of a 1 --> 6 glycosidic bond |
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Fate of glucose 1 phosphate, after glycogenolysis
1. In the muscle. 2. In the liver. |
1. Phosphoglucomutase makes G6P for glycolysis
2. Phosphoglucomutase and glucose-6-phosphatase release glucose into circulation |
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Glycogen synthesis
1. What does phosphoglucomutase do? 2. What is the reaction that UDP-glucose pyrophosphorylase carries out? 3. What does amylo-1,4 --> 1,6 translglycosylase do? |
1. Converts g6p to g1p
2. UTP + G1P --> UDPG + PPi 3. moves at least 6 residues from a non reducing end to at least 4 residues from the last branching point |
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What is the allosteric control of glycogen phosphorylase?
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8AMP, 9G6P
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What is the hormonal regulation of glycogen, in muscle?
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Epinephrine, which binds the B receptor (Gs), cAMP, protein kinase A, stimulates glycogen phosphorylase, inhibits glycogen synthase
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Regulation of glycogen:
Epinephrine in liver has what effect? with regards to insulin? |
Activates Protein Kinase C (inositol phosphate) and phosphorylates insulin receptor, which decreases insulin binding
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Regulation of glycogen:
What effect does Glucagon have on liver and muscle? |
Hits B receptor, increases blood sugar by breaking down glycogen
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Regulation of glycogen:
Protein phosphatase-1 |
Active when cAMP disappears. stimulated by free glucose and by separation from glycogen phosphorylase a.
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Three steps of glycogen degradation:
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1. Release of glucose 1 phosphate from glycogen
2. remodeling of glycogen substrate to permit further degradation 3. Conversion of G1P to G6P |
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What are three possible fates of G6P after glycogen breakdown?
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Glycolysis
Free Glucose Forms pentose, releasing NADPH |
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Glycogen synthesis requires an activated form of glucose called
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UDP-glucose
Formed from UTP and glucose-1-phosphate |
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How does glycogen phosphorylase cleave glycogen?
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By adding orthophosphate (Pi)
This is called phosphorolysis. |
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Is the phosphorolytic cleavage of glycogen energetically advantageous?
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Yes.
Glucose is released and is already phosphorylated. Free glucose needs to be phosphorylated an additional time to continue with glycolysis, or to catch up with G1P. Also, the negatively charged G1P cannot exit the muscle cell - a useful attribute in muscle cells. |
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What enzyme in the liver allows glucose 6 phosphate to leave the cell?
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Glucose-6-phosphatase
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PENTOSE PHOSPHATE PATHWAY DELINIATION!
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yeah pentose phosphate for a while
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What are some pathways requiring NADPH?
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Fatty acid biosynthesis
Cholesterol Biosynthesis Neurotransmitter Biosynthesis Nucleotide Biosynthesis (detox) reduction of oxidized glutathione Cytochrome P450 monooxygenases |
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Pentose Phosphate Pathway:
1. Phase 1 2. Phase 2 |
1. Oxidative Phase. Oxidation of G6P to ribulose-5-phosphate. Creates 2 NADPH.
2. Nonoxidative phase. Pathway catalyzes the interconversion of 3, 4, 5, 6, and 7 carbon sugars. All reactions take place in the cytoplasm. |
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Oxidative Phase Part 1
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G6P is converted into 6-Phosphoglucono-sigma-lactone. How? By the enzyme Glucose 6-phosphate dehydrogenase. One NADPH is produced.
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Oxidative Phase Part 2
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6-phosphoglucono-sigma-lactone is converted to 6 phosphogluconate. How? By the enzyme Lactonase.
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Oxidative Phase Part 3
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Phosphogluconate is converted to ribulose 5-phosphate. How? By the enzyme 6-phosphogluconate dehydrogenase. 1 NADPH is produced.
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Some tissues that NADPH is produced in:
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Adrenal Glands
Testes Liver Adipose Tissue Ovary Mammary Glands |
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What is the key regulatory enzyme in glycogen synthesis?
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Glycogen synthase
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What does pka do to glycogen synthase?
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Phosphorylates it, turning it from glycogen synthase A to glycogen synthase B. Inactive form.
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What does pka do to glycogen phosphorylase?
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Phosphorylates it, turning it from glycogen phosphorylase B to A. Active form.
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What protein reverses the regulatory effects of kinases, in glycogen metabolism?
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protein phosphatase 1
PP1 |
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How does insulin activate glycogen synthesis?
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Insulin binds to receptor tyrosine kinase
Phosphorylates IRS Activates protein kinases Protein kinases inactivate glycogen synthase kinase Glycogen synthase kinase can no longer phosphorolate glycogen synthase Remaining glycogen synthase w/ phospho group are DEphosphorylated by protein phosphatase 1 Dephosphorylated glycogen synthase is active A form, starts making glycogen |
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1. pka + glycogen synthase
2. pka + phosphorylase |
1. glycogen synthase B
2. phosphorylase A |
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What happens when Glycogen Phosphorylase is allosterically modified with glucose?
Which organ can this only occur in? |
Glucose causes it to go from the R form to T form.
This release PP1, which was attached to it. PP1 then dephosphorylates glycogen phosphorylase and glycogen synthase. This causes glycogen synthesis. Can only occur in the liver. Muscle phosphorylase A is unaffected by blood glucose concentration levels. |
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Fatty acid degradation steps
Fatty acid synthesis steps |
Oxidation
Hydration Oxidation Cleavage Condensation Reduction Dehydration Reduction |
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What does lipase do?
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degrades triacylglycerols into monoacylglycerol and free fatty acids.
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How are fats transported once inside the mucosal cells of the intestine?
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Via chylomicrons. Composed mainly of triacylglycerols, with apoliprotein b-48 as the main protein component.
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Protein constituents of lipoprotein particles are called...
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apolipoproteins.
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Triacylglycerol is broken up into fatty acids and glycerol. What is the fate(s) of glycerol?
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Glycerol is converted to DHAP, then G3P. This can either go through gluconeogenesis or glycolysis.
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What happens to the fatty acids?
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They are transported to other tissues, oxidized into acetyl CoA, and then cranked through the Krebs cycle.
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How can fatty acid linkage to Acetyl CoA be possible, if the reaction is reversible?
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A pyrophosphatase cleaves the product, halting the reverse reaction.
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Where are fatty acids activated?
How do they enter the inner mitochondrial membrane? |
On the outer mitochondrial membrane
Conjugate with carnitine, a zwitterionic alcohol, and pass the membrane through a translocase |
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What does the complete oxidation of palmitate yield in ATP?
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16 C fatty acid.
-2 ATP for activating with CoA 7 chops, each yielding one NADH and one FADH2 8 actyl CoA units, which each produce 3 NADH, 1 FADH2, and 1 GTP 106 ATP |
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Glycocholate
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A bile salt that aids in lipid digestion in the stomach
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When free glycerol is used in gluconeogenesis what is it converted to first?
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Glycerol P
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What does glyercol derived from triacylglycerides convert to in the fed state?
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Pyruvate.
While fed, energy is available in the form of glucose. So, glycolysis occurs. |
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What does glycerol derived from triacylglycerides convert to in the fasting state?
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Glucose, through gluconeogenesis.
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What happens to fatty acids when fasting is prolonged? As in diabetes?
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Acetyl Coa turns into ketone bodies.
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Why do ketone bodies form during the super fasting state?
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No carbohydrates means there is no oxaloacetate to join with acetyl coA in the Krebs cycle. Acetyl CoA, then, just kind of floats around until it turns into a ketone body
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What are some examples of ketone bodies?
Where are they made? What tissues are they a source of energy for? |
3-hydroxybutyrate, Acetoacetate
Liver Heart muscle, renal cortex |
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Can animals convert fatty acids into glucose?
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No
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Fatty Acid Synthesis:
1. Location 2. Intermediates are attached to... 3. Enzymes are how many units? 4. activated donor 5. elongation is driven by... 6. Reductant 7. Oxidants 8. When does elongation by fatty acid synthase complex stop? |
1. Cytoplasm
2. Acyl Carrier Protein (ACP) 3. Single polypeptide chain, called fatty acid synthase 4. malonyl ACP 5. release of CO2 6. NADPH 7. NAD+ and FAD 8. When you make palmitate |
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What is the committed step in Fatty Acid Synthesis
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The formation of Malonyl CoA
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The synthesis of malonyl CoA is catalyzed by
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acetyl coA carboxylase
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How does acetyl CoA make it out of the mitochondria after it's made?
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By combining with oxaloacetate to form citrate, which then can pass through the membrane.
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Acetyl CoA Carboxylase:
when phosphorylated, it's when dephosphorylated, it's |
activated
deactivated |
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Acetyl CoA Carboxylase:
what phosphorylates it? |
AMPK. AMP dependent protein kinase.
Activated by AMP. Inhibited by AMP. So carboxylase is inactivated when fuel reserves are low. Fats are not synthesized when energy is required. |
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Acetyl CoA Carboxylase:
Allosteric activation by what? |
Citrate.
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Two potential sources of NADPH
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Pentose Phosphate Pathway
Conversion of Malate to Pyruvate in the acetyl coA transport cycle |
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True or False:
A phosphorylated Acetyl CoA carboxylase is inactive, but can be partially active with the presence of citrate |
True
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What is a common intermediate in the synthesis of phospholipids and triacylglycerols?
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Phosphatidate
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Where is phosphatidate synthesized?
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In the endoplasmic reticulum and outer mitochondrial membrane.
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Pathway of phospatidate synthesis
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Start with glycerol-3-phosphate.
Slap it with two acyl CoA's. Catalyzed by Glycerol Phosphate Acyl Transferase. |
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What is the primary site of triacylglycerol synthesis?
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The Liver
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Cholesterol synthesis:
What is the carbon source? |
Acetyl CoA. For all 27 carbons
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Cholesterol Synthesis:
3 stages |
Synthesis of isopentenyl pyrophosphate, the key building block of cholesterol
Condensation of 6 of these building blocks to form squalene Squalene cyclizes tetracyclic product is converted into cholesterol |
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What is the committed step in cholesterol formation?
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The synthesis of mevalonate.
Catalyzed by HMG co reductase |
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What is the fate of HMG CoA in the cytoplasm?
What is the fate of HMG CoA in the mitochondria? |
Mevalonate
Acetoacetate and Acetyl CoA |
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How is mevalonate turned into 3-isopentenyl pyrophosphate, the building block of squalene?
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By phosphorylating it 3 times and then a decarboxylation
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What is the major apolipoprotein of a chylomicron?
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B-48
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Where is cholesterol and triacylglycerol made?
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The liver
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How are triacylglycerols released from their lipoprotein shell?
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Lipoprotein lipases, attached to the wall of the blood vessels. Work by hydrolysis
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What is the major apolipoprotein of VLDL, IDL, LDL
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B-100 and apo E.
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What is the purpose of HDL?
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Cholesterol turnover - when cells and membranes die, HDL picks up the pieces, esterifies them and brings them to the liver.
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QUESTIONS FROM OLD TEST
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YEAH
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Which of the following is not a gluconeogenic substrate?
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Acetoacetate
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Which enzymes are required to convert pyruvate into phosphoenol pyruvate?
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Pyruvate carboxylase, and phosphoenol pyruvate carboxykinase
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Conversion of PFK 2 to fructose 2,6 bisphosphatase by protein kinase A activates...
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fructose 1, 6 bisphosphatase
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How many ATP molecules are required to make glucose from malate?
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4
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Several irreversible steps in glycolysis must be bypassed in gluconegenesis by specific enyzmes. The glycolytic steps include all the following except:
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substrate level phosphorylation of ADP from 1,3 bisphosphoglycerate
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What dehydrogenase also catalyzes a decarboxylation?
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6-phosphoglucanolactone dehydrogenase
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What is the prosthetic group of mitochondrial glycerol phosphate dehydrogenase?
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FAD
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How many ATPs are generated as a result of the oxidation of cytoplasmic NADH via the glycerol-P shuttle?
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1.5
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What respiratory complex doesn't pump protons?
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Complex II
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Which respiratory complex doesn't contain Fe-S proteins?
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complex IV
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In addition to complex I and I, which other flavoproteins transfer electrons to Coenzyme Q?
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Fatty acyl CoA dehydrogenase
Glycerol P dehydrogenase |
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Cyanide stops electron transfer fom cytochrome a3 to oxygen. This process is also blocked as a result of this inhibition.
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Proton pumping stops
NADH oxidation ATP formation Krebs cycle |
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The total amount of ATP resulting from the complete oxidation of glucose to 6 CO2 is:
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30
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The enzyme translocase (ATP/ADP antiport)
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Takes negative charges from the matrix
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What is the role of apoprotein C-II?
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To activate LPL
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Digested lipids in the intestine are packed and delivered as
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Chylomicrons
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Order of increasing density of lipoproteins:
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Chylomicrons
VLDL IDL LDL |
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Ketone bodies in the liver result indirectly from a combination of all the following processes except:
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accumulation of citrate.
meaning they DO result from: Gluconeogenesis When energy is only provided by B oxidation Protein Kinase A activation Increased cAMP |
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The formation of acetoacetyl CoA from acetoacetate in peripheral tissues requires:
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succinyl CoA
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What is the role of carnitine?
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transports acyl groups
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Which of the following lipases are activated by phosphorylation?
pancreatic lipase lipoprotein lipase pancreatic phospholipase A2 |
None of the above
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Can all krebs cycle intermediates be used for gluconeogenesis?
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Yes
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Are ketone bodies carried as part of VLDL?
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No
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Is fatty acid oxidation the main source of energy for gluconeogenesis?
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Yes
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Are cytochromes always inegral membrane proteins?
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No
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What is the main carrier of cholesterol in the blood?
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low density lipoprotein
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