Chapter 1: Introduction

• Energy is needed for all cellular activities

• Energy comes from the sun through nuclear fusion reactions

• Plants use sunlight, carbon dioxide, and water to produce glucose

• Glucose is the starting material for metabolic processes in our bodies

• Cellular respiration is the degradation of biomolecules to generate energy

Chapter 2: Aerobic Respiration

• Aerobic respiration requires oxygen

• Glucose can be converted into carbon dioxide, water, and energy in the presence of oxygen

• Biological organisms can be viewed as machines that undergo combustion reactions

• NAD+ and NADH are electron carriers involved in metabolic pathways

• Dehydrogenase enzyme facilitates the breakdown of glucose

Chapter 3: Cellular Respiration Pathways

• Cellular respiration occurs through three major pathways: glycolysis, the citric acid cycle, and oxidative phosphorylation

Glycolysis

• Glycolysis occurs in the cytoplasm of the cell

• Glycolysis is the process of splitting glucose into two pyruvate molecules

• Glycolysis is an anaerobic pathway, meaning it does not require oxygen

• One glucose molecule can yield a net of two ATPs in glycolysis

Chapter 1: ATP Yield in Pathway

• This pathway yields 2 ATP molecules.

• It involves 10 steps, each catalyzed by a specific enzyme.

• In the preparatory phase, two ATP molecules are invested.

• In the payoff phase, four ATP molecules are generated over several steps.

Chapter 2: Ten Enzymes Ten Steps

Overview of Each Step

• Hexokinase Reaction

  • The enzyme hexokinase phosphorylates the oxygen on carbon 6 to make glucose 6-phosphate.

  • The polar phosphate group traps the molecule inside the cell.

  • The concentration of regular glucose inside the cell is reduced, encouraging more glucose to enter by diffusion.

  • This step costs 1 ATP, which provides the necessary phosphate group for the reaction.

• Glucose-6-phosphate Isomerization

  • Glucose-6-phosphate isomerizes to become fructose-6-phosphate.

  • This process is catalyzed by phosphoglucoisomerase.

Chapter 3: Isomerization

• Phosphorylation on carbon 1 hydroxyl

  • Catalyzed by phosphofructokinase 1

  • Costs another ATP

• Cleavage of fructose-1,6-bisphosphate into two smaller molecules

Chapter 4: Second Phosphorylation

• Fructose bisphosphate aldolase is a lyase enzyme

• It splits fructose-1,6-bisphosphate into:

  • A molecule of glyceraldehyde-3-phosphate (GADP)

  • A molecule of dihydroxyacetone phosphate (DHAP)

• The DHAP is converted into another molecule of GADP

  • This conversion is done by the enzyme triosephosphate isomerase

• Result: Two molecules of GADP

Chapter 5: Cleavage

• The preparatory phase has ended with two ATPs spent for phosphorylations.

• The payoff phase begins.

• One of the GADP molecules from the preparatory phase will undergo oxidation.

• The oxidation will result in the formation of 1,3-bisphosphoglycerate.

Chapter 6: Conversion of DHAP into GADP

• This conversion requires NAD+ and a free phosphate (inorganic phosphate)

• The enzyme involved in this conversion is called glyceraldehyde phosphate dehydrogenase

Chapter 7: Oxidation

Main Ideas:

• A phosphoglycerate kinase catalyzes the transfer of a phosphate group to ADP to become 3-phosphoglycerate, producing one ATP in the process.

• Each of the two GADP molecules will make one ATP, resulting in a total of two ATPs for half the total payoff of glycolysis.

• Phosphoglycerate mutase transfers the remaining phosphate from this hydroxyl to the next one over to make 2-phosphoglycerate.

Chapter 8: Phosphate Transfer

• Enolase catalyzes a dehydration reaction

  • Results in the loss of a hydroxyl group

  • Produces phosphoenolpyruvate

Chapter 9: Dehydration

• The remaining phosphate group is transferred to an ADP by pyruvate kinase

  • This process generates another ATP

  • The pyruvate we discussed before is also produced

Chapter 10: Second Dephosphorylation

• The glycolysis process consists of 10 steps

• Preparatory phase:

  • Converts one molecule of glucose into two molecules of GADP

  • Requires two ATP

• Payoff phase:

  • Converts each molecule of GADP into pyruvate

  • Produces two ATP per molecule of GADP

  • Total of four ATP produced

• Net energy production from one molecule of glucose is two ATP

Memorizing Glycolysis

• Basic facts about glycolysis can be summarized as follows

• Glycolysis converts glucose into pyruvate in the cytoplasm of the cell

• Pyruvate then moves on to the next stage of cellular respiration

Enzymes and Steps

Here is a table listing the necessary enzymes for each step of glycolysis, along with any relevant input or output:

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