week 2 carbohydratemetabolism l2.pdf

8/10/2019 WEEK 2 CARBOHYDRATEMETABOLISM L2.pdf

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BIOCHEMISTRY

CARBOHYDRATES METABOLISM

LECTURE 2

Taif UniversityCollege of Medicine

Second Year Students

Dr. Gaber Shehab

Stage 2: Glycolysis Pathway

Catabolism of Carbohydrates


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Stage 2: Glycolysis Pathway

In this Stage, the glucose

(6C) obtained from

digestion is degraded to 2

pyruvate (3C).

2

2

P 113

Atlas of Biochemistry, page 113


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Lecture Outline

GLYCOLYSIS

Pathway

Location

Overview of the Pathway

Equations

Function

Regulation

GLYCOLYSIS LOCATION

Cytosol of all cells


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GLYCOLYSIS PATHWAYS

In glycolysis a molecule of glucose is degraded in a

series of enzyme-catalyzed reactions to yield two

molecules of the three-carbon compound pyruvate.

The breakdown of glucose into two molecules of

pyruvate occurs in ten steps,

the first five of which constitute thepreparatory phaseand

the last five of which constitute thepayoff phase

GLYCOLYSIS PATHWAYS


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the

p

reparatoryphase

the

payoffphase

5Steps

5St

eps

G

lycolysisPathway

2

ee

ee

ee

Glycolysis: Energy-Investing phase

In reactions 1-5 of glycolysis:

Energy is used to add phosphate groups to glucose

and fructose-6-phosphate.

Glucose (6C) is converted to two molecules (3C).


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Glycolysis: : Energy-Investing phase

1

2

3

4

5

5

3-

Glycolysis: Energy-generating phase

In reactions 7

and 10, the

hydrolysis of

phosphates in

the triose

phosphates

generates four

ATP molecules.


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Glycolysis: Reactions 6-10

6

7

8

9

10

Enolase

Glucose + 2ADP +

2Pi + 2 NAD+

2 Pyruvate + 2 ATP

+ 2 NADH + 2H+

Glycolysis: Overall Reaction


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Important note

Under Anaerobic condition Glucose converts to

two molecules of the three-carbon compound

Lactate.

Anaerobic Glycolysis

ee

ee

Glycolysis


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Glucose

2 lactate + 2ATP

Anaerobic Glycolysis

GLYCOLYSIS EQUATIONS

Aerobic:

Glucose + 2ADP + 2Pi + 2NAD 2 pyruvate + 2ATP + 2NADH + 2H+

Anaerobic:

Glucose + 2ADP + 2Pi 2 lactate + 2ATP


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Important note

During the oxidative phosphorylation

(Aerobic condition; Mitocondria)

Each NADH produces 3 ATP

Each FADH produces 2 ATP

CALCULATE THE NET ATP PRODUCESDURING GLYCOLYSIS FROM ONE MOLE

GLUCOSE UNDER AEROBIC AND

ANAEROBIC CONDITION?

Question


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GlycolysisFunctions

Glycolysis: General Functions

ATP production by converting glucose to pyruvate or lactate.

Recycle NADH by making lactate under anaerobic condition

Hexose monophosphate pathway (Glucose-6-phosphate)

Glycogen synthesis (Glucose-1-phosphate)

Fatty acid synthesis (Source of Acetyl CoA)

Krebs Cycle (Source of Acetyl CoA)

(Source of Glycerol-phosphate)TG synthesis

Generate intermediates for other pathways:


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Atlas of Biochemistry, page 113

Glycolysis: Specific Tissue Functions

RBCsRely exclusively for energy (No Mitochondria)

Skeletal muscleSource of energy during exercise,Particularly high intensity exercise (lack of oxygen)

Adipose tissue & LiverSource of glycerol-P for TG synthesis

Source of acetyl-CoA for FA synthesis


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Regulation ofGlycolysis

Effect of insulinand glucagon onthe synthesis ofkey enzymes ofglycolysis in liver.

Hormonal

Regulation of

Glycolysis


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Regulation of Glycolysis

Reaction 1 Hexokinase is inhibited by high levels of glucose-6-

phosphate, which prevents the phosphorylation of glucose.

Reaction 3 Phosphofructokinase, an allosteric enzyme, is

inhibited by high levels of ATP and activated by high levels of

ADP and AMP.

Reaction 10 Pyruvate kinase, another allosteric enzyme is

inhibited by high levels of ATP or acetyl CoA.

From Another Reference

Glycolysis Pathway


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Glycolysis Pathway

Glycolysis Pathway

week 2 carbohydratemetabolism l2.pdf

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