Lecture 11: Electron Transport and Enzymes

Question 1

Describe how energy is generated through electron transport

Answer 1

Electron transport chain: The first electron carrier in an ETC has the most negative each successive carrier is slightly less negative. Thus electrons are transferred spontaneously from one carrier to the next.

• Free energy is made available from electron transfer.
• Linking up several redox reactions: Electron transport chain

Question 2

List the different types of common electron carriers

Answer 2

NADH dehydrogenases:

Flavoproteins:

Iron-sulfur proteins:

Cytochromes

Quinones

Question 3

What is the mechanism of enzymes in metabolic reactions?

Answer 3

• Enzymes go to the active site where they catalyze the reaction
• How? The lower the activation energy by concentrating substrates, which are the molecules that are reacting together.

Question 4

Develop ideas for antibiotic/enzyme inhibitors

Answer 4

What do Enzyme inhibitors do? 
-They lower the efficiency of the enzyme
How do they do this?
You can have a Competitive inhibitor
-Directly competes with the substrate and binds in the active site
-Cannot be converted to products
OR
You can have a Noncompetitive inhibitor
-Binds somewhere else in/on the enzyme
-Enzyme’s structure changes and results in decreased activity

Question 5

What is the function of enzymes in metabolic reactions?

Answer 5

What is the function of enzymes in metabolic reactions?

-Catalyst and enzymes increase the rate of reactions.

Question 6

Define substrates, products, and active site.

Answer 6

Substrates: reacting molecules

Products: substrates formed

Active site: location in enzyme where catalysis occurs

Question 7

What is proportional to ΔG

Answer 7

Change in reduction potential is proportional to ΔG

Question 8

Characteristics of NADH dehydrogenases.

Answer 8

NADH dehydrogenases:

• Proteins bound in the cytoplasmic membrane
• Proteins bound in membrane. Most negative Eo.

(NADH is related to NADPH and donates electrons to the electron transport chain. They contain a nicotinamide ring which accepts 2 electrons and 1 proton from a donor, the second electron is released.)

Question 9

Characteristics of Flavoproteins.

Answer 9

Flavoproteins:

FAD or FMN, exchange 2 electrons and 2 protons

Question 10

Characteristics of Iron-sulfur proteins.

Answer 10

Iron-sulfur proteins:
-Non-heme
-Carry one e- at a time
(Ferredoxin is an Fe-S protein)

Question 11

Characteristics of Cytochromes.

Answer 11

Cytochromes

• Heme
• Carry 1 e- at a time
• iron atoms are apart of the heme group

Question 12

Characteristics of Quinones.

Answer 12

Quinones
-Coenzyme Q (ubiquinone)
-Transports 2 electrons and 2 protons to cytochromes and several other carriers
(Hydrophobic molecules that move about in the membrane)