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40 Cards in this Set
- Front
- Back
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What is anaerobic glycolysis?
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When the pyruvate and NADH from glycolysis are converted to lactate for the generation of ATP in the absence of oxygen
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What are the two phases of the glycolytic pathway?
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A preparative phase
ATP -generating phase |
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What is the preparative phase in the glycolytic pathway?
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This phase uses 2 ATP per mole of glucose to phosphorylate glucose twice and cleave it into two triose phosphates
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What is the ATP generating phase in the glycolytic pathway?
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This phase generates 4 ATP and 2 NADH.
Glyceraldehyde 3-phosphate is phosphorylated using an inorganic phosphate and this bond is transferred to ATP. It's partner dihydyroxyacetone phosphate is rearranged to 1,3 bis- Phosphoglycerate which has a high energy phosphate bond which is transferred to ADP |
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What is the net yield of the the glycolytic pathway?
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2 mol of ATP, 2 mol of NADH, and 2 mol of pyruvate per mole of glucose
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Why is the phosphorylation of glucose irreversible?
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it is irreversible because the reaction has a high negative delta G
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Name the enzymes that catalyze the phosphorylation of glucose?
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Hexokinases
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How does the hexokinases in the liver and the beta cell of the pancreas differ from other cells?
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The hexokinase isoenzyme of liver and beta cell of pancreas has a much higher Km and is called glucokinase.
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What step of glycolysis permanently commits glucose to the glycolytic pathway?
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The phosphorylation of F6P to F 1,6 bis-P by PFK-1
The regulation of PFK controls the entrance of glucose into the glycolytic pathway |
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What is the fate of F 1,6 bis- P in the glycolytic pathway?
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It is cleaved by aldolase into Dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate .
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What is the fate of DHAP?
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It is isomerized to glyceraldehyde 3-P by phosphoglycerate kinase
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What is the step in the glycolytic pathway where NAD+ is reduced to NADH?
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The oxidation of glyceraldehyde 3-P by glyceraldehyde 3-P dehydrogenase to 1,3 bis- phophoglycerate
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How much ATP does the oxidation of pyruvate generate?
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12.5 mol of ATP
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What are the compounds in the glycolytic pathway that provide the high energy phosphate bonds for ADP ?
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Phosophoenol-pyruvate
1,3 bis- phosphoglycerate |
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Why do we need NADH to be recycled back to NAD+ for glycolysis?
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We need a continuous supple of NAD+ as the proton acceptor for the glyceraldehyde 3-P
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What are the two routes for the oxidation of NADH?
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Aerobic --> using shuttles that transfer reducing equivalents across the mitochondrial membrane then to the electron transport chain and to oxygen
Anaerobic --> does not need oxygen. |
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What are the two options for pyruvate?
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It is based on how NADH is reoxidized
1. If NADH is reoxidized by the shuttle system then pyruvate can be used for other pathways i.e acetyl CoA 2. If NADH is reoxidized by lactate dehydrogenase then pyruvate is reduced to lactate |
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Name the two shuttle systems for NADH.
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Glycerol 3-P
Malate -Asparate |
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Why do you need a shuttle for NADH for the oxidation process?
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The inner mitochondrial membrane is impermeable to NADH and there is no direct transport protein for NADH to cross the membrane
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Where does NADH transfer its eletrons in the glycerol 3-P shuttle?
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DHAP
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Where does NADH transfer its electrons in the malate-aspartate shuttle?
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oxaloacetate
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Describe the glycerol 3-phosphate shuttle
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NAD+ is regenerated from NADH transfering its electron to DHAP. This transfer changes DHAP to glycerol 3-P. Glycreol 3-P diffuses through the outer to inner mitochondrial membrane where it tranfers its electron to FAD to make FAD (2H)
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Describe the malate- aspartate shuttle
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NAD+ is regenerated to NADH by transferring its electron to oxaloacetate. This transfer changes oxaloacetate to malate. Malate is transported into the mitochonria using a translocase that exchanges it for alpha-ketoglutarate. Inside the mitochondria malate donates its electron to NAD+ and is converted back to oxaloacetate. Since this can't leave the cell, it is transaminated to asparate. Aspartate leaves via a translocase that exchanges it with glutamate. Once outside aspartate is transaminased back to oxaloacetate.
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What is the role of lactate dehydrogenase in anaerobic glycolysis?
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NADH is oxidized to NAD+ and pyruvate is reduced to lactate by lactate dehydrogenase.
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Why does the cotinuous anaerobic glycolysis use up the glycogen stores
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To make the same amount of ATP pre unit time from anaerobic glycolysis as the complete aerobic oxidation of glucose to CO2, anaerobic glycolysis must occur 15 X faster and use 15 x more glucose
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How does the glycerol 3-P shuttle compare to the malate -asparate shuttle?
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If the cytosolic NADH is oxidized by glycerol 3-P shuttle then 1.5 mol of ATP is made per NADH
If the cytosolic NADH is oxidized by malate-asparate shuttle then 2.5 mol of ATP is produced |
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What are the energy -generating steps as pyruvate is completely oxidized to carbon dioxide to make 12.5 molecules of ATP per pyruvate?
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Four steps generate NADH:
pyruvate dehydrogenase isocitrate dehydrogenase alpha-ketoglutarate dehydrogenase malate dehydrogenase Each step makes NADH and each NADH makes 2.5 mol of ATP (10) Additional steps: succinate dehydrogenase makes FAD (2H) --> make 1.5 ATP succinate thiokinase phosphorylation --> makes 1 ATP This makes the total 12 |
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What is the fate of lactic acid?
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At the intracellular pH of 7.35, lactic acid dissociates to form lactate anion and H+
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What are the conditions for lactic acidosis?
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Lactic acid dissociates intracellularly to lactate and H+. These are transported into the interstitial fluid and eventually diffuse into the blood.
If the amount of lactate generated exceeds the buffering capacity of the blood, the pH drops below the normal range, resulting in lactic acidosis |
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Name some tissues that rely on anaerobic glycolysis at least partly.
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RBCs
WBCs the kidney medulla The tissues of the eye skeletal muscles |
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Which tissues of the eye use at least some anaerobic glycolysis?
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the corneal epithelium and the lens
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Why does the eye use anaerobic glycolysis?
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The eye contains cells that transmit light and these cells cannot be filled with opaque structures like mitochondria or dense capillary beds
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How does the cornea obtain oxygen?
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It diffuses from the air
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What is the process that the lens uses to make ATP if it has no mitochondria?
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A small amount of ATP is required (for ion balance) so anaerobic glycolysis can easily generate it for its needs.
The lens is able to pick up glucose and release lactate into the vitreous body and aqueous humor. It does not need oxygen and has no need for capillaries |
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Why don't RBCs need mitchondria?
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The mature RBC has no mitochondria because oxidative metabolism might interfere with its function in transporting oxygen bound to hemoglobin
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What is the typical profile of a tissue or cell relies heavily on anaerobic glycolysis?
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It usually has a low ATP demand, high levels of glycolytic enzymes and few capillaries ( oxygen has to diffuse a greater distance)
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What is the Cori cycle?
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Lactate released from cells from anaerobic glycolysis is taken up by the liver, skeletal muscle, and heart and oxidized back to pyruvate. In the liver the pyruvate is used for gluconeogenesis
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How is lactate recycled in the peripheral tissues?
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The lactate is oxidized to pyruvate which is oxidized to CO2 in the TCA cycle
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Describe the structure of LDH?
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LDH is a tetramer composed of A subunits (also called M subunits for skeletal muscle form) and B subunits ( also called H subunits for heart
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What type of LDH is found in the heart?
What type of LDH is found in the muscle? |
In skeletal muscle, the M4 form converts pyruvate to lactate
In cardiac muscle, the H4 form converts lactate to pyruvate |
