Biotyping Based on Oxygen Use and Tolerance Lab 17

Question 1

Why do so many organisms use oxygen in chemical reactions that generate ATP?

Answer 1

• oxygen is reactive

- is the final electron acceptor in the electron transport chain, assisting the movement of electrons down the chain

Question 2

What are the characteristics of reactive oxygen species (ROS)?

Answer 2

• chemical entity (reactive)
• are made as unintended products in chemical reactions that transfer electrons
• Damages important molecules (proteins, lipids, DNA)

Question 3

Name 4 reactive oxygen species

Answer 3

1. singlet oxygen
2. superoxide radicals
3. hydroxyl radicals
4. hydroperoxide anions

Question 4

What is a radical (free radical)?

Answer 4

• a molecule that has an unpaired electron

- are very destructive

Question 5

What happens when a free radical reacts with another molecule?

Answer 5

• breaks the molecule into 2 fragments one, one of which is then a radical
• 2nd radical repeats this process causing a chain reaction of cellular destruction

Question 6

Name 3 antioxidant enzymes that organisms posses that help detoxify ROS

Answer 6

• superoxide dismutase
• catalase
• peroxidase

Question 7

summarize a superoxide dismutase reaction

Answer 7

02 - 02 > H2O2 + O2

Question 8

summerise a catalase reaction

Answer 8

2 H2O2 > 2 H2O + O2 (bubbles in the catalase test)

Question 9

Summarise a peroxidase test

Answer 9

H2O2 + NADH + H+ > 2 H20 + 2 NAD+

Question 10

Name 3 antioxidant compounds

Answer 10

Vit A
Vit C
Vit E

Question 11

What is a obligate aerobe?

Answer 11

• O2 is necessary to grow/survive

- cell resp to make ATP

Question 12

What is a facultative anaerobe?

Answer 12

• will use O2 if available (faster growth)
• if no O2 available > fermentation

-has antioxidants

Question 13

What is a obligate anaerobe?

Answer 13

• does not use O2
• O2 is toxic
• No antioxidants

Question 14

What is a Aerotolerant anaerobe?

Answer 14

-Does not use O2 (fermentation only), but not harmed by it either ( because of antioxidants)

Question 15

What is a microaerophile?

Answer 15

-needs O2, but cannot tolerate large concentrations

• 21% O2= death
• 0% O2= no growth
• 2-10%= cell resp

Question 16

What is the purpose of a thioglycolate medium?

Answer 16

• reacts with O2, creating lower concentraions of O2 deeper in the tube
• low concentration of agar creates semisolid, slowing O2 diffusion

Question 17

In a thioglycolate medium, what ingredients indicate the presence of O2?

Answer 17

-resazurin or methylene blue (only near top)