Microbiology Chapter 6

Front 1

Microbes grown aerobically use glucose less rapidly than those grown anaerobically
How can this be explained ?

Back 1

The Pasteur Effect
Rate-limiting step of the EMP glycolytic pathway is the reaction catalyzed by phosphofructokinase (PFK)

Fructose-6-phosphate + ATP --PFK--> Fructose-1,6-diphosphate + ADP

Front 2

Describe an allosteric enzyme and give an example of one (used in the Embden-Meyerhoff pathway)

Back 2

An enzyme that has two binding sites:
The active site binds the substrate
The allosteric site binds the effector
Allosteric activators make the substrate bind better
Allosteric inhibitors inhibit the binding of the substrate

PFK - phosphofructokinase

Front 3

Describe the roles of AMP, ADP and ATP in the Embden-Meyerhoff pathway

Back 3

ATP is an allosteric inhibitor
AMP and ADP are allosteric activators

Front 4

In the presence of oxygen, the cell is undergoing:

Back 4

aerobic respiration

Front 5

In the absence of oxygen, the cell is undergoing:

Back 5

fermentation

Front 6

In the presence of oxygen, the number of ATP's per glucose molecule is:

PFK is:

Back 6

high

inhibited

Front 7

In the absence of oxygen, the number of ATP's per glucose molecule is:

phosphofructokinase (PFK) is:

Back 7

low

not inhibited

Front 8

Where does the tricarboxylic acid cycle occur

in eukaryotes:
in prokaryotes:

Back 8

mitochondria
cytoplasm

Front 9

For each pyruvate oxidized in the tricarboxylic acid cycle it produces:

Back 9

3 CO2 are produced by decarboxylation
4 NADH and 1 FADH2 are produced by REDOX reactions
1 Nucleoside triphosphate (NTP) is produced by substrate-level phosphorylation

Front 10

When pyruvate is converted to Acetyl-CoA in the first step of the tricarboxylic acid cycle, this enzyme is required:

Back 10

pyruvate dehydrogenase

Front 11

A major controlling point of the TCA cycle is:

Back 11

the reaction catalyzed by citrate synthase
Oxaloacetate + Acetyl-CoA --> Citrate

Front 12

Allosteric effectors in

Gram - bacteria:
Gram + bacteria:

Back 12

NADH and α-ketoglutarate in Gram-negative bacteria
ATP in Gram-positive bacteria

Front 13

The TCA cycle plays a biosynthetic as well as a bioenergetic role. These are examples:

Back 13

α-Ketoglutarate and oxaloacetate = Used in the biosynthesis of amino acids
Succinyl-CoA = Used for porphyrin rings for carriers which chelate iron
Oxaloacetate = Can be converted to PEP, a glucose precursor
Acetyl-CoA = Used in the biosynthesis of fatty acids 

Front 14

Membrane-associated electron carriers are found here in

prokaryotes:
eukaryotes:

Back 14

cell membrane
inner mitochondrial membrane

Front 15

Electron carriers and what they transport:

Back 15

Flavoproteins, Quinones = protons and e-
Iron-sulfur proteins, cytochromes = only e-

Front 16

The accumulation of H+ on one side of the membrane, results in the generation of a:

Back 16

pH gradient
eletrochemical potential

Front 17

Describe the proton motive force and what determines it:

Back 17

The energized state of a membrane. The accumulation of H+ on one side of the membrane causes the membrane to be energized with potential energy

Front 18

ATP synthase protein complex contains channels for:

Back 18

proton entry

Front 19

Because protons cannot permeate the membrane, these provide passage:

Back 19

ATP synthase protein complex channels

Front 20

Describe ATP synthase protein complex:

Back 20

Contains channels for protons to travel through the membrane. As protons push in through this channel, the potential energy is used to generate ATP

Front 21

How many coupling sites are there for ATP generation in the ATP synthase protein complex?

Back 21

There are 3 coupling sites for ATP generation

Front 22

List the amount of ATP generated In chemiosmotic ATP generation and where it comes from.

Back 22

Each NADH molecule produces as many as 3 ATP molecules
Each FADH₂ molecule produces as many as 2 ATP molecules

Front 23

List the classes of chemicals that affect electron transport and give examples:

Back 23

Inhibitors = Block transport of e- through the ETC to O2
Example: Cyanide

Uncouplers = Prevent the synthesis of ATP but do not interfere with electron transport
Example: 2,4 dinitrophenol

Front 24

Describe in detail (each step) the theoretical maximum ATP yield from aerobic oxidation of glucose.

Back 24

EMP Pathway of Glycolysis:
Substrate-level phosphorylation (ATP) - 2 ATP
Oxidative phosphorylation with 2 NADH - 6 ATP

2 Pyruvate to 2 Acetyl-CoA:
Oxidative phosphorylation with 2 NADH - 6 ATP

Tricarboxylic Acid Cycle:
Substrate-level phosphorylation (GTP) - 2 ATP
Oxidative phosphorylation with 6 NADH - 18 ATP
Oxidative phosphorylation with 2 FADH2 - 4 ATP

TOTAL: 38ATP

Front 25

Write the overall reaction for aerobic respiration of glucose.

Back 25

C6H12O6 + 6O2 + 38ADP + 38Pi --> 6CO2 + 6H2O + 38ATP

Front 26

This organism has an ETC that gives the theoretical maximum yield:

Back 26

Paracoccus denitrificans

Front 27

List the amount of ATP that Escherichia coli gives for each NADH and FADH2

Back 27

2ATP for each NADH
1ATP for each FADH₂

Front 28

Escherichia coli has an ETC that gives
2 ATP for every NADH
1 ATP for every FADH2

What is the maximum yield of ATP from glucose in aerobic respiration?

Back 28

EMP Pathway of Glycolysis:
Substrate-level phosphorylation (ATP) - 2 ATP
Oxidative phosphorylation with 2 NADH - 4 ATP

2 Pyruvate to 2 Acetyl-CoA:
Oxidative phosphorylation with 2 NADH - 4 ATP

Tricarboxylic Acid Cycle:
Substrate-level phosphorylation (GTP) - 2 ATP
Oxidative phosphorylation with 6 NADH - 12 ATP
Oxidative phosphorylation with 2 FADH2 - 2 ATP

TOTAL: 26ATP

Front 29

What is the major difference between aerobic and anaerobic respiration?

Back 29

The difference is that the TEA in the electron transport chain is a chemical compound other than oxygen. This makes the change in redox potential (E_o) much smaller and therefore less energy can be generated.

Front 30

List the anaerobic organisms given, their terminal electron acceptors, and the product formed.

Back 30

Escherichia coli NO₃- NO₂-
Escherichia coli Fumarate Succinate
Desulfovibrio desulfuricans SO₄2- H₂S
Methanosarcina barkeri CO₂ CH₄
Geobacter metallireducens Fe3+ Fe2+

Front 31

For every glucose molecule converted into pyruvate, how many NAD+ molecules are consumed during fermentation?

Back 31

2

Front 32

List the organisms and the type of fermentation:

Back 32

Escherichia: Mixed acid
Enterobacter: Butanediol
Lactobacillus: Lactic acid
Saccharomyces: Alcoholic
Propionibacterium: Propionic acid
Clostridium: Butyric acid

Front 33

There are several different fermentation pathways but they are all similar in these ways:

Back 33

NADH is oxidized into NAD+
The electron acceptor is a pyruvate derivative

Front 34

Describe homolactic fermentation:

Back 34

Homolactic Fermentation
Involves the EMP pathway
Overall reaction:
Glucose + 2 ADP + 2 Pi --> 2 lactic acid + 2 ATP

Front 35

What organisms use homolactic fermentation?

Back 35

It is utilized by Streptococcus, some Lactobacillus
It is also utilized by algae, protozoa and even in human skeletal muscle

Front 36

What enzyme does homolactic fermentation use?

Back 36

lactic dehydrogenase

Front 37

Describe heterolactic fermentation:

Back 37

Involves the Pentose Phosphate pathway
Overall reaction:
Glucose + ADP + Pi --> lactic acid + ethanol + CO2 + ATP

Front 38

What organisms use heterolactic fermentation?

Back 38

It is utilized by Leuconostoc, some Lactobacillus

Front 39

Describe ethanolic fermentation:

Back 39

Involves the EMP pathway
Overall reaction:
Glucose + 2 ADP + 2 Pi --> 2 ethanol + 2 CO2 + 2 ATP

Front 40

What enzyme does ethanolic fermentation use?

Back 40

Pyruvate decarboxylase
Alcohol dehydrogenase

Front 41

What is the need of fermentation?

Back 41

For every glucose molecule converted into pyruvate, two NAD+ molecules are consumed. There is a limited amount of NAD+ in the cell so if it is not regenerated then the oxidation of glyceraldehyde-3-phosphate will cease and glycolysis will STOP

Front 42

Briefly describe the process of fermentation.

Back 42

Fermentation is an energy-yielding process in which organic molecules serve as both electron donors and acceptors