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KULIAH MIKROBIOLOGI DASAR�“METABOLISME MIKROBIA”

OLEH : D A R I U S

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Microbial Metabolism

Energy Metabolism
The Relationship between Catabolism and Anabolism
Respiration
Fermentation

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Metabolism - all of the chemical reactions within a living organism

1. Catabolism ( Catabolic )

breakdown of complex organic molecules into simpler compounds
releases ENERGY

2. Anabolism ( Anabolic )

the building of complex organic molecules from simpler ones
requires ENERGY

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An Overview metabolism

　metabolism：

the sum total of all chemical reactions occurring in the cell

metabolism

catabolism

anabolism

Complex molecules

catabolism

anabolism

Simple molecules

ATP

[H]

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Anabolism and Catabolism

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Chapter 5

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summarize

Energy Metabolism in Microbes

Primary Energy

Organic Compounds

Sunlight

Inorganic Compounds

in Reduced State

ATP

Chemoheterotroph

Photoautotroph

Photoheterotroph

Chemoautotroph

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Chapter 5

Breakdown

Proteins to Amino Acids, Starch to Glucose

Synthesis

Amino Acids to Proteins, Glucose to Starch

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Chapter 5

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Pyruvate: universal intermediate

Aerobic respiration

Fermentation

Glycolysis (EMP pathway)

Substrate-level phosphorylation

Catabolism

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Tricarboxylic Acid (TCA) cycle

1. Pyruvate => Acetyl-CoA

1x NADH => 3ATP

2. TCA cycle:

3x NADH => 3x 3 ATP

1x FADH2 => 1x 2 ATP

1x GTP => 1x ATP

3. NADH & FADH2 go to

the Electron transport chain

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Electron transport

chain

1. Electrons carried by NADH (FADH2)

A series of donor-acceptor pairs
Oxygen: terminal electron acceptor
Aerobic respiration

2. Some bacteria use other compounds

(CO2, NO₃^-) as terminal acceptor

Anaerobic respiration
Produce less ATP

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Chemiosmosis

Production of ATP in Electron Transport
Electrochemical Gradient Formed between membranes
H+ (Protons) generated from NADH
Electrical Force (+) & pH Force (Acid)
Gradient formed
ATPase enzyme that channels H+ from High to Low concentration

Chapter 5

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6.13 Fermentation enables cells to produce ATP without oxygen

Fermentation is an anaerobic (without oxygen) energy-generating process

It takes advantage of glycolysis, producing two ATP molecules and reducing NAD⁺ to NADH
The trick is to oxidize the NADH without passing its electrons through the electron transport chain to oxygen

Fermentation captures significantly less energy from a glucose molecule than is captured from glucose through respiration.

Student Misconceptions and Concerns

1. Perhaps more than anywhere else in general biology, students studying aerobic metabolism may fail to see the forest for the trees. Students may focus on the details of each stage of aerobic metabolism and devote little attention to the overall process and products. Consider emphasizing the products and energy yields associated with glycolysis, the citric acid cycle, and oxidative phosphorylation before detailing the specifics of each reaction.

2. The location within a cell in which each reaction takes place is often forgotten in the details of the chemical processes, but it is important to emphasize. Consider using Figure 6.12 as a common reference to locate each stage as you discuss the details of cellular respiration.

3. Students frequently think that plants have chloroplasts instead of mitochondria. Take care to point out the need for mitochondria in plants when photosynthesis is not efficient or possible (such as during the night).

4. Students may expect that fermentation will produce alcohol and maybe even carbon dioxide. Take the time to clarify the different possible products of fermentation and correct this general misconception.

Teaching Tips

1. The text notes that some microbes are useful in the dairy industry because they produce lactic acid. However, the impact of acids on milk may not be obvious to many students. Consider a simple demonstration mixing about equal portions of milk (skim or 2%) with some acid (vinegar will work). Notice the accumulation of strands of milk curd (protein) on the side of the container and stirring device.

2. Dry wines are produced when the yeast cells use up all or most of the sugar available. Sweet wines result when the alcohol accumulates enough to inhibit fermentation before the sugar is depleted.

3. Exposing fermenting yeast to oxygen will slow or stop the process, because the yeast will switch back to aerobic respiration. When fermentation is rapid, the carbon dioxide produced drives away the oxygen immediately above the wine. However, as fermentation slows down, the wine must be sealed to prevent oxygen exposure and permit the fermentation process to finish.

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6.13 Fermentation enables cells to produce ATP without oxygen

Your muscle cells and certain bacteria can oxidize NADH through lactic acid fermentation

NADH is oxidized to NAD⁺ when pyruvate is reduced to lactate
In a sense, pyruvate is serving as an “electron sink,” a place to dispose of the electrons generated by oxidation reactions in glycolysis

Animation: Fermentation Overview

Fermentations are used by the dairy industry to make cheese and yogurt, while other industries produce soy sauce and sauerkraut through fermentation reactions.

Student Misconceptions and Concerns

1. Perhaps more than anywhere else in general biology, students studying aerobic metabolism may fail to see the forest for the trees. Students may focus on the details of each stage of aerobic metabolism and devote little attention to the overall process and products. Consider emphasizing the products and energy yields associated with glycolysis, the citric acid cycle, and oxidative phosphorylation before detailing the specifics of each reaction.

2. The location within a cell in which each reaction takes place is often forgotten in the details of the chemical processes, but it is important to emphasize. Consider using Figure 6.12 as a common reference to locate each stage as you discuss the details of cellular respiration.

3. Students frequently think that plants have chloroplasts instead of mitochondria. Take care to point out the need for mitochondria in plants when photosynthesis is not efficient or possible (such as during the night).

4. Students may expect that fermentation will produce alcohol and maybe even carbon dioxide. Take the time to clarify the different possible products of fermentation and correct this general misconception.

Teaching Tips

1. The text notes that some microbes are useful in the dairy industry because they produce lactic acid. However, the impact of acids on milk may not be obvious to many students. Consider a simple demonstration mixing about equal portions of milk (skim or 2%) with some acid (vinegar will work). Notice the accumulation of strands of milk curd (protein) on the side of the container and stirring device.

2. Dry wines are produced when the yeast cells use up all or most of the sugar available. Sweet wines result when the alcohol accumulates enough to inhibit fermentation before the sugar is depleted.

3. Exposing fermenting yeast to oxygen will slow or stop the process, because the yeast will switch back to aerobic respiration. When fermentation is rapid, the carbon dioxide produced drives away the oxygen immediately above the wine. However, as fermentation slows down, the wine must be sealed to prevent oxygen exposure and permit the fermentation process to finish.

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6.13 Fermentation enables cells to produce ATP without oxygen

The baking and winemaking industry have used alcohol fermentation for thousands of years

Yeasts are single-celled fungi that not only can use respiration for energy but can ferment under anaerobic conditions
They convert pyruvate to CO₂ and ethanol while oxidizing NADH back to NAD⁺

The carbon dioxide provides the bubbles in beer and champagne and also the bubbles in dough that cause bread to rise.

Student Misconceptions and Concerns

1. Perhaps more than anywhere else in general biology, students studying aerobic metabolism may fail to see the forest for the trees. Students may focus on the details of each stage of aerobic metabolism and devote little attention to the overall process and products. Consider emphasizing the products and energy yields associated with glycolysis, the citric acid cycle, and oxidative phosphorylation before detailing the specifics of each reaction.

2. The location within a cell in which each reaction takes place is often forgotten in the details of the chemical processes, but it is important to emphasize. Consider using Figure 6.12 as a common reference to locate each stage as you discuss the details of cellular respiration.

3. Students frequently think that plants have chloroplasts instead of mitochondria. Take care to point out the need for mitochondria in plants when photosynthesis is not efficient or possible (such as during the night).

4. Students may expect that fermentation will produce alcohol and maybe even carbon dioxide. Take the time to clarify the different possible products of fermentation and correct this general misconception.

Teaching Tips

1. The text notes that some microbes are useful in the dairy industry because they produce lactic acid. However, the impact of acids on milk may not be obvious to many students. Consider a simple demonstration mixing about equal portions of milk (skim or 2%) with some acid (vinegar will work). Notice the accumulation of strands of milk curd (protein) on the side of the container and stirring device.

2. Dry wines are produced when the yeast cells use up all or most of the sugar available. Sweet wines result when the alcohol accumulates enough to inhibit fermentation before the sugar is depleted.

3. Exposing fermenting yeast to oxygen will slow or stop the process, because the yeast will switch back to aerobic respiration. When fermentation is rapid, the carbon dioxide produced drives away the oxygen immediately above the wine. However, as fermentation slows down, the wine must be sealed to prevent oxygen exposure and permit the fermentation process to finish.

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Saccharomycetes

E. coli

Clostridium

Propionebacterium

Enterobacter

Streptococcus

Lactobacillus

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CO₂

Autotroph

Organic Compounds

Heterotroph

Anabolism

(biosynthesis)

Carbons Sources

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Organic compounds,

i.e., glucose, succinate

Inorganic compounds,

S, Fe²⁺,CO₂, H₂, CH₄

Light

Chemical compounds

Organotrophs

Litotrophs

Phototrophs

Chemotrophs

Catabolism

ATP, pmf

Energy Sources:

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Common Step

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Fermentation: metabolic process in which the final electron acceptor is an organic compound.

Sources of metabolic energy

Respiration: chemical reduction of an electron acceptor through a specific series of electron carriers in the membrane. The electron acceptor is commonly O₂, but CO₂, SO₄^2-, and NO^3- are employed by some microorganisms.

Photosynthesis: similar to respiration except that the reductant and oxidant are created by light energy. Respiration can provide photosynthetic organisms with energy in the absence of light.

Substrate-level phosphorylation

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Chapter 5

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Generation of a proton-motive force(1)

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Glucose

NADH

NAD⁺

2

NADH

2

NAD⁺

2

2 ADP

P

ATP

2

2 Pyruvate

2 Lactate

GLYCOLYSIS

Lactic acid fermentation

+

2

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2 ADP

P

ATP

2

GLYCOLYSIS

NADH

NAD⁺

2

NADH

2

NAD⁺

2

2 Pyruvate

2 Ethanol

Alcohol fermentation

Glucose

CO₂

2

released

+

2

Wine- grapes, water, yeast

Beer- water, malted barley, hops and yeast

Grains make liquors from mashing and yeast

To Yeast, EtOH is toxic and secreted to the extracellular space. If you ferment too much, the yeast die and this limits the proof of what you are drinking.

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Electrons from organic compounds

Are usually first transferred to NAD⁺, a coenzyme

NAD⁺

H

O

O^–

O

O^–

O

P

CH₂

HO

OH

H

HO

OH

HO

H

N⁺

C

NH₂

H

N

H

NH₂

N

Nicotinamide�(oxidized form)

NH₂

+

2[H]

(from food)

Oxidation of NADH

2 e^–+ 2 H⁺

2 e^–+ H⁺

NADH

O

H

N

C

+

Nicotinamide�(reduced form)

N

Reduction of NAD⁺

Dehydrogenase

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Another Carrier Molecule... FAD+/FADH₂

Flavin adenine dinucleotide

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NAD⁺/NADH

NAD+ = Nicotinamide Adenine Dinucleotide
An organic molecule that cells make from the vitamin niacin (B3)
It is used to carry electrons during cell respiration
The electrons added to NAD⁺ in making NADH carry energy the cell has harvested and can eventually use

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Microbial Metabolism