lecturn fe 16 fri. 2.17.1dfd2

7/28/2019 Lecturn fe 16 Fri. 2.17.1dfd2

1/23

Lecture 16

Glycolysis II


2/23

Glycolysis & Human


3/23

Glucose

Cytoplasm

Transporter(Malfunction is related to Diabetes)

HOH

Before Step 1 of Glycolysis:

Inherited Diseases:

Deficiency of Phosphoglycerate Kinase (Step 7)Deficiency of Pyruvate Kinase (Step 10)

Inability of exercise due to muscle pains


4/23

Arsenate Poisoning

Arsenate (AsO43-) is structural analog of inorganic

phosphate Pi (HPO42-) Competes with phosphate for binding site inglyceraldehyde 3-phosphate dehydrogenase (Step 6)

Very unstable!


5/23

Questions & Answers


6/23

Quest ion:

What is the net outcome per molecule of

glucose during glycolysis?

1. 2 ATP consumed; 4 ATP produced; 2 pyruvate produced





7/23

Quest ion:

Why is the PFK-1 step of glycolysis

called the first commi t tedstep?

1. It is the first regulated step of the pathway.

2. It is the only metabolically irreversible step.

3. It is the first step through which all hexoses entering thepathway must pass.

4. It is the step bridging the hexose and triose phases.

5. It is the first step to produce ATP.


8/23

Quest ion:

Which is true about the four isozymes of

hexokinase?1. They all have approximately the same Kmvalue.

2. Hexokinases I and II catalyze the reverse of the

reaction catalyzed by hexokinases III and IV.3. All four hexokinases are usually saturated at normal

blood glucose concentrations.

4. Hexokinase I is active mostly in the liver.

5. Hexokinase IV has a much higherKmthan the others.


9/23

More Quest ions :

1. What are the three irreversible steps of

glycolysis?

2. The product of aldolase is dihdroxyacetone

phosphateand ______. Give name and chemical

structure.


10/23

Fate of Pyruvate,

Horto n Chapter 11.3


11/23

The Fate

of Pyruvate

10 Steps of Glycolysis

(See Lecture 11)

Citric Acid

Cycle CO2H2O

Animals, Plants

& many Microbesunderaerobicconditions

(see later)


12/23

The Fate

of Pyruvate

Anaerobic:

Fermentation to Ethanol

in yeast & some bacteria

Anaerobic:

Fermentation to Lactate

in exercising muscles,

red blood cells

and lactic acid bacteria

Precursor in

Gluconeogenesis
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13/23

Fermentation

In the absence of aerobic respiration(=membrane-associated electron transport system, see later)

Fermentation regenerates NAD+(Oxidizes NADH to NAD+)

If NAD+ would not be regeneratedglycolysis would stop!


14/23

~ ~~

NADH + H+NAD+

Step 6:The addition of a phosphategroup is coupled to an oxidation,

generating NADH and a

high-energy phosphate bond.Step 7:ATP is produced by

substrate-level

phosphorylation.

Step 8:A chemicalrearrangement occurs.

Step 10:ATP is produced bysubstrate-level

phosphorylation.

Step 9:Water is removed, causingthe phosphate bond tobecome high-energy.

Glyceraldehyde

3-phosphate

1,3-bisphospho-

glycerate

3-phospho-

glycerate2-phospho-

glycerate

Phospho-

enolpyruvate

Pyruvate

~

H2O

~ ~~


15/23

Reoxidation of NADH

during alcoholic Fermentation

In yeast & some bacteria (Zymomonas)


16/23

Reoxidation of NADH

during alcoholic Fermentation

In yeast & some bacteria (Zymomonas)

Production of alcoholic

beverages (beer & wine)

and bread

Hangover
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17/23

THE OVERALL REACTION

Glucose + 2 ADP3-

+ 2 Pi2-

+ 2 H+

2 Ethanol + 2 CO2 + 2 ATP4- + 2 H2O


18/23

Auto-Brewery Syndrome

Consumption of carbohydrate-rich foods (sugar)

the patient appears drunk

Ethanol production in the gut by yeast

Caused by infection (e.g. antibiotic poisoning)


19/23

Reoxidation of NADH

during Lactic Acid Fermentation

in exercising muscles,

red blood cells, and

lactic acid bacteria

(Strepto coc cus, Lactob aci l lus)

Exercise

Tooth decay

Cheese, Yogurt,

Sauerkraut, Pickles
http://upload.wikimedia.org/wikipedia/commons/4/45/Glasbutton_Tipp.svg


20/23

THE OVERALL REACTION

Glucose + 2 ADP3-

+ 2 Pi2-

2 Lactate- + 2 ATP4- + 2 H2O


21/23

Alligator:

Quick burst ofenergy by lactic

acid fermentation

Generate ATP inthe muscle quickly

without O2

Needs long

recovery to clear

excess lactate(source of sourness

after exercise)


22/23

The Pasteur Effect

Facultative microbes have both

fermentation and aerobic

respiration With O2 - Consumes less

glucose

Without O2 - Consumes moreglucose

S


23/23

Summary

Under anaerobic conditions:

Pyruvate Ethanol & CO2or Pyruvate LactateBoth processes regenerate NAD+ from NADH.

lecturn fe 16 fri. 2.17.1dfd2

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