Exam 4 Review:  Chapter 24:  Carbohydrate Metabolism

Krebs cycle = citric acid cycle - A repetitive series of enzymatic reactions occurring in the matrix of the mitochondria involving oxidative metabolism of acetyl grouped, provided by the production of Acetyl CoA from the decarboxylattion of pyruvate molecules to produce high-energy phosphate compounds (GTPs) or electron transport compounds (NADs and FADs) capable of transferring energetic electrons and hydrogen ions to the electron transport system to produce high-energy phosphate compounds (GTPs); the products of this pathway are a major source of cellular energy.  aka - tricarboxylic acid cycle.

pyruvate = pyruvic acid - The 3-carbon end product of aerobic glycolysis which can be transferred from the cell cytoplasm to the matrix of the mitochondria to enter the citric acid cycle, which can use the molecule as a nutrient source for additional energy production.

lactate = lactic acid - The 3-carbon end product of anaerobic glycolysis (fermentation of pyruvate) which must leave the muscle cell and travel to the liver, heart, or kidneys, which can use the molecule as a nutrient source for additional energy production; the liver is also capable of reconverting this molecule into glucose or glycogen.

acetyl CoA - A metobolic intermediary compound consisting of the 2-carbon acetate group covalently joined to the carrier CoEnzyme A; it carries acetate groups from the decarboxylation of pyruvate molecules or from the beta oxidation of fatty acids or from the deamination of amino acids to enter the citric acid cycle in the matrix of the mitochondria to produce useful chemical energy; this compound can also serve as a building block for the synthesis of fatty acids, amino acids, glucose, and other organic molecules in the cell.

For more information, visit the "Layperson's Guide to Bioenergetics."

List:

12. the four stages of glucose catabolism and where they occur within the cell.

          (1)  glycolysis = the glycolytic pathway - occurs in the cytoplasm
          (2)  decarboxylation of pyruvate to acetate = formation of acetyl Coenzyme A - occurs in the matrix of the mitochondrion
          (3)  Kreb's Cycle = Citric Acid Cycle = TriCarboxylic Acid Cycle - occurs in the matrix of the mitochondrion
          (4)  oxidative phosphorylation = electron transport chain - occurs in the inner membrane = cristae membrane of the mitochondrion

Sketch and Label:

3. the structure of a mitochondrion. Show where the four stages of glucose catabolism occur relative to the structure of the mitochondrion.

(1)  glycolysis = the glycolytic pathway - occurs in the cytoplasm

(2)  decarboxylation of pyruvate to acetate = formation of acetyl Coenzyme A - occurs in the matrix of the mitochondrion

(3)  Kreb's Cycle = Citric Acid Cycle = TriCarboxylic Acid Cycle - occurs in the matrix of the mitochondrion

(4)  oxidative phosphorylation = electron transport chain - occurs in the inner membrane = cristae membrane of the mitochondrion

Describe:

4.  the fate of pyruvate under (a) anaerobic and (b) aerobic conditions in the cell in terms of the final end (waste) products and useful energy harvest (ATP production).

 
  Final End (Waste) Products Useful Energy Harvest (ATP Production)
Anaerobic 2 molecules lactate per glucose and waste heat net gain 2 ATPs per glucose
Aerobic 6 CO2 and 12 H2O and waste heat net gain 36-38 ATPs per glucose