Chapter 23 Metabolic Pathways for Metabolic Pathways and Energy Production Author Timberlake...

download Chapter 23 Metabolic Pathways for   Metabolic Pathways and Energy Production Author Timberlake Created Date 6/20/2007 11:32:56 AM

of 45

  • date post

    04-May-2018
  • Category

    Documents

  • view

    233
  • download

    7

Embed Size (px)

Transcript of Chapter 23 Metabolic Pathways for Metabolic Pathways and Energy Production Author Timberlake...

  • 1Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    23.4 Digestion of Carbohydrates23.5 Glycolysis: Oxidation of Glucose23.6 Pathways for Pyruvate

    Chapter 23 Metabolic Pathways for Carbohydrates

  • 2Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    In the mouth, salivary amylase hydrolyzes -glycosidic bonds in polysaccharides to give smaller polysaccharides (dextrins), maltose, and some glucose.In the small intestine, pancreatic amylasehydrolyzes dextrins to maltose and glucose.The disaccharides maltose, lactose, and sucrose are hydrolyzed to monosaccharides.The monosaccharides enter the bloodstream for transport to the cells.

    Stage 1: Digestion of Carbohydrates

  • 3Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Digestion of Carbohydrates

  • 4Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    GlycolysisIn Stage 2, the metabolic pathway called glycolysisdegrades glucose (6C) to pyruvate (3C).

  • 5Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

  • 6Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Glycolysis: Energy-InvestmentIn reactions 1-5 of glycolysis:

    Energy is used to add phosphate groups to glucose and fructose. Glucose is converted to two three-carbon molecules.

    http://instruct1.cit.cornell.edu/courses/biomi290/ASM/glycolysis.dcrhttp://instruct1.cit.cornell.edu/courses/biomi290/ASM/glycolysis.dcrhttp://programs.northlandcollege.edu/biology/Biology1111/animations/glycolysis.htmlhttp://www.tcd.ie/Biochemistry/IUBMB-Nicholson/swf/glycolysis.swf

  • 7Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Glycolysis: Energy Investment

    1

    2

    3

    4

    5 5

  • 8Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Glycolysis: Energy-ProductionIn reactions 7 and 10, the hydrolysis of phosphates in the triosephosphates generates four ATP molecules.

  • 9Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Glycolysis: Reactions 6-10

    6

    7

    8

    9

    10

  • 10Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Glycolysis generates 2 ATP and 2 NADH.Two ATP are used in energy-investment to add phosphate groups to glucose and fructose-6-phosphate.Four ATP are formed in energy-generation by direct transfers of phosphate groups to four ADP.

    Glucose + 2ADP + 2Pi + 2NAD+2Pyruvate + 2ATP + 2NADH + 4H+

    Glycolysis: Overall Reaction

  • 11Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Regulation of GlycolysisReaction 1 Hexokinase is inhibited by high levels of glucose-6-phosphate, which prevents the phosphorylation of glucose.Reaction 3 Phosphofructokinase, an allostericenzyme, is inhibited by high levels of ATP and activated by high levels of ADP and AMP.Reaction 10 Pyruvate kinase, another allostericenzyme is inhibited by high levels of ATP or acetyl CoA.

  • 12Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Learning CheckIn glycolysis, what compounds provide phosphate groups for the production of ATP?

  • 13Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    SolutionIn glycolysis, what compounds provide phosphate groups for the production of ATP?In reaction 7, phosphate groups from two 1,3-bisphosphoglycerate molecules are used to form two ATP.In reaction 10, phosphate groups from two phosphoenolpyruvate molecules are used to form two more ATP.

  • 14Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    When oxygen is present in the cell, (aerobic conditions), pyruvate from glycolysis is decarboxylated to produce acetyl CoA and CO2.

    O||

    CH3CCOO- + HSCoA + NAD+pyruvate

    O||

    CH3CSCoA + CO2 + NADH + H+acetyl CoA

    23.5 The Fate of Pyruvate

  • 15Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    When oxygen is not available (anaerobic conditions), pyruvate is reduced to lactate, which replenishes NAD+ to continue glycolysis.

    O lactate|| dehydrogenase

    CH3CCOO- + NADH + H+ pyruvate

    OH|

    CH3CHCOO- + NAD+lactate

    Lactate Formation

  • 16Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Under anaerobic conditions (strenuous exercise):Oxygen in the muscles is depleted.Lactate accumulates in the muscles.Muscles tire and become painful. Rest is needed to repay the oxygen debt and to reform pyruvate in the liver.

    Lactate in Muscles

  • 17Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Pathways for Pyruvate

  • 18Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Match the following terms with the descriptions:1) Catabolic reactions 2) Coenzymes3) Glycolysis 4) LactateA. Produced during anaerobic conditions.B. Reaction series that converts glucose to pyruvate.C. Metabolic reactions that break down large

    molecules to smaller molecules + energy.D. Substances that remove or add H atoms in

    oxidation and reduction reactions.

    Learning Check

  • 19Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Match the following terms with the descriptions:1) Catabolic reactions 2) Coenzymes3) Glycolysis 4) Lactate

    A. 4 Produced during anaerobic conditions.B. 3 Reaction series that converts glucose to pyruvate.C. 1 Metabolic reactions that break down large

    molecules to smaller molecules + energy.D. 2 Substances that remove or add H atoms in

    oxidation and reduction reactions.

    Solution

  • 20Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    23.7 Regulation of Glucose Metabolism and energy Production

    High glucose levels and insulin promote glycolysis. Low glucose levels and glucagonpromote gluconeogenesis.

  • 21Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    23.10 Glycogen Metabolism: Glycogenesis and Glycogenolysis

  • 22Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Glycogenesis

    Glycogenesis:Stores glucose by converting glucose to glycogen.Operates when high levels of glucose-6-phosphate are formed in the first reaction of glycolysis.Does not operate when energy stores (glycogen) are full, which means that additional glucose is converted to body fat.

  • 23Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Diagram of Glycogenesis

  • 24Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Formation of Glucose-6-PhosphateGlucose is converted to glucose-6-phosphate using ATP.

    Glucose-6-phosphate

    O

    OHOH

    OH

    OH

    CH2OP

  • 25Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Formation of Glucose-1-PhosphateGlucose-6-phosphate is convertedto glucose-1-phosphate.

    Glucose-6-phosphate Glucose-1-phosphate

    O

    OOH

    OH

    OH

    CH2OH

    P

    O

    OHOH

    OH

    OH

    CH2OP

  • 26Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    UDP-GlucoseUTP converts glucose-1-phosphate to UDP-glucose and pyrophosphate (PPi).

    UDP-glucose

    O

    OOH

    OH

    OH

    CH2OH

    P

    O

    O-O P

    O

    O-O CH2

    O

    OHOH

    N

    N

    O

    H

    O

  • 27Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Glycogenesis: GlycogenThe glucose in UDP-glucose adds to glycogen.

    UDP-Glucose + glycogen glycogen-glucose + UDP

    The UDP reacts with ATP to regenerate UTP.UDP + ATP UTP + ADP

  • 28Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Glycogenolysis

    Glycogenolysisis the break down of glycogen to glucose.

  • 29Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    GlycogenolysisGlycogenolysis:

    Is activated by glucagon (low blood glucose). Bonds glucose to phosphate to form glucose-1-phosphate.Glycogen-glucose + Pi

    Glycogen + glucose-1-phosphate

  • 30Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Isomerization of Glucose-1-phosphate

    The glucose-1-phosphate isomerizes to glucose-6-phosphate, which enters glycolysis for energy production.

  • 31Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Glucose-6-phosphateGlucose-6-phosphate:

    Is not utilized by brain and skeletal muscle because they lack glucose-6-phosphatase. Hydrolyzes to glucose in the liver and kidney, where glucose-6-phosphatase is available providing free glucose for the brain and skeletal muscle.

  • 32Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    Learning CheckMatch each description with:1) Glycogenesis 2) GlycogenolysisA. Activated by low levels of blood glucose.B. Converts glucose-1-phosphate to glucose-6-

    phosphate.C. Activated by high levels of glucose-6-phosphate.D. Glucose + UTP UDP-glucose + PPi

  • 33Copyright 2004 Pearson Education Inc., publishing as Benjamin Cummings.

    SolutionMatch each description with:1) Glycogenesis 2) GlycogenolysisA. 2 Activated by low levels of blood glucose.B. 2 Converts glucose-1-phosphate to glucose-6-

    phosphate.C. 1 Activated by high levels of gluco