Metabolism

    Cards (58)

    • Aerobic respiration:
      • Inputs: glucose
      • Outputs: ATP
      • Key steps: glycolysis, pyruvate dehydrogenase complex, citric acid cycle
    • Carbohydrate metabolism goal: Convert glucose into usable energy in the form of ATP
    • Glycolysis:
      • Functions: split glucose into pyruvate, reduce NAD+ to NADH, generate ATP from ADP
      • Inputs: 1 glucose, 2 NAD+, 2 ATP
      • Outputs: 2 pyruvate, 2 NADH, 4 ATP
    • Energy Investment Phase:
      • Hexokinase phosphorylates glucose
      • Conversion of isomers: G6P into fructose-6-phosphate
      • Conversion F6P into fructose 1,6-bisphosphate by PFK-1
      • F 1,6BP is cleaved into G3P and DHAP
    • Energy Payoff Phase:
      • Conversion of G3P into 1,3-bisphosphoglycerate, reducing NAD+ to NADH (substrate level phosphorylation)
      • Transfer of a phosphate from 1,3-bisphosphoglycerate to ADP, forming ATP
      • Rearrangement of 3-phosphoglycerate into PEP
      • Transfer of a phosphate from PEP to ADP, forming ATP and pyruvate
    • Pyruvate Dehydrogenase Complex:
      • Transport into mitochondrial matrix via carrier proteins
      • Pyruvate is decarboxylated to form acetyl-CoA
      • Inputs: pyruvate, NAD+
      • Outputs: Acetyl-CoA, NADH
    • Citric Acid Cycle:
      • Acetyl-CoA fused with oxaloacetate to form citrate
      • Reduction of electron carriers and formation of GTP
      • Inputs (each turn): 1 pyruvate, 3 NAD+, 1 FAD
      • Outputs (each turn): 1 GTP, 3 NADH, 1 FADH2, 2 CO2
    • Gluconeogenesis:
      • Creates glucose from non-carbohydrate sources
      • Occurs in the liver and kidneys
      • Pyruvate is starting point, which comes from various sources, not products of glycolysis
      • bypasses irreversible steps of glycolysis
    • Regulation Of Glycolysis:
      • Negative feedback regulation, hormone regulation, allosteric regulation
      • Three main regulatory steps: Phosphofructokinase, Hexokinase, pyruvate kinase
    • PDC regulation:
      Cells needing energy: High levels of AMP, coenzyme A and NAD+ upregulate PDC
      Cells with surplus of energy regulate via feedback inhibition (high ATP, NADH, or acetyl-CoA downregulate PDC)
    • Electron Transport Chain Disruption:
      • Cyanide inhibition of Cytochrome C
      • 2,4-Dinitrophenol and ATP synthase bypass
    • Anabolic reactions build up larger molecules from simpler ones using the released energy.
    • Catabolic reactions break down molecules into smaller units to release energy.
    • Glycolysis occurs in the cytosol of the cell
    • Glycolysis functions:
      -involves breakdown of glucose (6 carbons) into two pyruvate (3 carbons)
      -split glucose into 2 pyruvate
      -Reduces NAD+ to NADH
      -Generate 2 ATP per 1 glucose
    • Glycolysis: Net production of 2 ATP molecules per glucose molecule
    • Energy investment phase utilizes 2 ATP molecules to begin breakdown of glucose
    • Energy payoff phase results in 2 molecules of pyruvate, 2 NADH, and a net gain of 4 ATP per glucose
    • In aerobic cellular conditions, pyruvate enters the citric acid cycle, NADH goes to the electron transport chain for more ATP production
    • In anaerobic cellular conditions, fermentation process regenerates NAD+ and allows glycolysis to continue
    • Insulin upregulates glycolysis; glucagon downregulates glycolysis
    • Gluconeogenesis occurs when blood glucose levels are low
    • High ratio ATP to ADP/AMP downregulates glycolysis; low ratio of ATP to ADP/AMP upregulates glycolysis
    • High levels of citrate and NADH downregulates glycolysis. this indicates an abundance of energy resources
    • Hexokinase is inhibited by glucose-6-phosphate (negative feedback inhibition)
    • PFK-1 inhibited by ATP and citrate; activated by AMP; controlled by fructose 2,6-bisphosphate (allosteric effector)
    • Hexokinase, phosphofructose kinase, and pyruvate kinase are regulatory steps in glycolysis
    • Pyruvate kinase inhibited by ATP, acetyl CoA, and fatty acids (negative feedback inhibition)
    • The liver produces most of the glucose needed during fasting through gluconeogenesis.
    • Lactic acid fermentation involves the reduction of pyruvate to lactic acid via lactate dehydrogenase; recycles NADH to NAD+ to sustain glycolysis in anaerobic conditions
    • Ethanol fermentation is two-step pathway characteristic in yeast, brewing, and food fermentation. Regenerates NAD+ from NADH to sustain glycolysis during anaerobic conditions
      1. Pyruvate decarboxylation to acetaldehyde with CO2 release by pyruvate decarboxylase
      2. Reduction of acetaldehyde to ethanol by alcohol dehydrogenase
    • Substrates for gluconeogenesis:
      • protein via amino acid convertion
      • glycerol from FA breakdown
      • lactate from lactic acid fermentation
    • First step in gluconeogenesis: pyruvate to oxaloacetate by pyruvate decarboxylase in mitochondria
      -malate shuttle transports oxaloacetate back to cytosol
      Second step: oxaloacetate to PEP by PEP carboxykinase in cytosol
    • Key bypass reactions in gluconeogenesis:
      • first step: conversion of pyruvate to oxaloacetate then to PEP
      • hydrolysis of fructose 1,6-biphosphate to fructose 6-phosphate by fructose 1,6-biphosphatase
      • isomerization of F6P back to G6P, followed by the formation of glucose by glucose 6-phosphatase
    • High acetyl-Coa downregulates pyruvate's conversion to acetyl-Coa in mitochondria, causing pyruvate to be diverted towards gluconeogenesis
    • Glucagon reduces levels of F2,6-BP, promoting gluconeogenesis
    • Insulin activates F2,6-BP, inhibiting gluconeogenesis
    • High levels of F2,6-BP inhibits gluconeogenesis (via F1,6BPhostaphase) and activates glyclolysis (via PFK1)
    • High AMP indicates low energy, inhibiting gluconeogenesis
    • Inner mitochondrial membrane is impermeable to most substances except H2O and small gas molecules
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