Metabolism

Question 1

What is respiration?

Answer 1

electrons are passed from an electron donor to a terminal electron acceptor via the electron transfer system in the cell membrane forming a proton gradient

Question 2

What is aerobic respiration?

Answer 2

O2 is the final electron acceptor which then is reduced to H2O

Question 3

What is anaerobic respiration?

Answer 3

An ion or compound other than O2 is the terminal electron acceptor(nitrite, nitrate, sulfur)

Question 4

Although the presence of oxygen yields more ATP what is a negative characterization of it?

Answer 4

Forms two highly toxic compounds

Question 5

Why do anaerobes die in the presence of oxygen?

Answer 5

They lack catalase and superoxide dismutase

Question 6

Do facultative anaerobes grow faster in aerobe or anaerobe conditions?

Answer 6

Grows faster while respiring aerobically due to a higher yield of ATP per glucose

Question 7

How do chemoautotrophs generate ATP?

Answer 7

Generate ATP by oxidizing inorganic compounds via respiration and the electron transport system.

Question 8

Examples of inorganic energy sources

Answer 8

H2S, Fe2+, Mn2+

Question 9

Gets its energy from sunlight and its carbon from CO 2?

Answer 9

Photoautotrophs
Ex. algae and cyanobacteria

Question 10

Gets its energy and carbon from inorganic sources? Give examples of inorganic sources of energy and carbon for these microbes.

Answer 10

Chemoautotrophs
-Ex: H2S, Fe2+, Mn2+

Question 11

Gets its energy from sunlight and its carbon from organic compounds?

Answer 11

Photoheterotrophs

Question 12

Is most similar to animals in its energy and carbon sources?

Answer 12

Chemoheterotrophs

Question 13

Is most similar to plants in its energy and carbon sources?

Answer 13

Photoautotrophs

Question 14

What are ways in which prokaryotes can generate an ion transmembrane gradient?

Answer 14

-Respiration(aerobic or anaerobic)
-photosynthesis(oxygenic or anoxygenic)
-Enzyme ion pumps: membrane protein not associated with electron transport chain can that can pump protons or other ions across the membrane
-scalar reactions: consume or produce ions rather than move them

Question 15

What is photosynthesis?

Answer 15

Light energy activates electrons in chlorophyll in which flow down through an electron transport system to produce ATP or a reducing power

Question 16

Cyanobacteria

Answer 16

Have the same oxygenic photosynthesis as algae and plants
- water is the electron donor, oxygen formed

Question 17

Anoxygenic

Answer 17

-Other bacterias carry out anoxygenic photosynthesis using electron donors other than water such as H2 or H2S
-These bacteria include purple sulfur bacteria, purple non sulfur bacteria, and green sulfur bacteria

Question 18

Passive Transport

Answer 18

-Difussion
-Facilitated Diffusion: uses channel proteins for specific molecules
-Requires no energy and only occurs if solute is at a higher concentration outside the cell

Question 19

Active Transport

Answer 19

-requires energy
-Ion coupled: uses energy from the transmembrane ion gradient
-ABC transport: uses ATP hydrolysis to pump a nutrient into the cell after it has bound its corresponding periplasmic binding protein
-Phototransferase system(PTS): uses a high energy phosphate group to chemically modify a solute after it is transported so it can’t exit

Question 20

How do autotrophs fix CO 2 to make their precursor metabolites?

Answer 20

-uses the Calvin cycle for CO2 fixation
-catalyzes addition of CO2 in RUBISCO

Question 21

What are 3 common pathways that comprise central metabolism?

Answer 21

Pentose phosphate pathway, glycolysis, and TCA

Question 22

What is the purpose of the 13 precursor metabolites?

Answer 22

Biosynthesis
of the building
blocks (e.g.
sugars, amino
acids,
nucleotides,
fatty acids)

Question 23

Prototrophs

Answer 23

Bacteria that have no nutritional requirements for the building blocks

Question 24

Auxotrophs

Answer 24

are mutants of the prototrophs that now have one or more nutritional requirements for the building blocks
-Can grow if provided with the intermediate after the blocked step

Question 25

What is feedback inhibition?

Answer 25

• a type of noncompetitive inhibition
  -a way to control metabolic pathways in which the final product of the pathway inhibits the enzyme that catalyzes the first step of the pathway

Question 26

Prokaryotes have an amazing diversity in the ways they can metabolize energy. Which of these ways are also used by plants and animals? Which of these are unique to prokaryotes?

Answer 26

-photoheterotrophy and chemoautotrophy

Question 27

Transmembrane ion gradient

Answer 27

*proton gradient across the membrane = “proton motive force”
*a proton gradient represents a form of electrochemical energy
*ATP synthase (F 1 F 0 ATPase) mediates the interconversion of the
energy of the gradient with ATP

Question 28

Define: fermentation. What is the relationship between substrate-level phosphorylation and fermentation? What is NOT needed for fermentation to occur?

Answer 28

-fermentation: pathway in which glucose is partially oxidized into acids and alcohols
-when microbes are fermenting they use substrate level phosphorylation to generate ATP
-Fermentation does not require oxygen to occur
does not involve transmembrane ion gradient
-Many fermentations involve pyruvate

Question 29

What are the similarities & differences btwn. fermentation & Anaerobic respiration?

Answer 29

→ Similarities: Don’t need O2. Generate ATP.
→ Differences: Fermentation doesn’t use a Transmembrane ion gradient, while Anaerobic resp. does. Anaerobic resp. uses something other than O2 as final electron acceptor in ETC.

Question 30

What 2 qualities of enzymes make them so critical for life? What is the “active site”? What is an “allosteric site”?

Answer 30

1) Enzymes can catalyze reactions (speed up reactions)
2) Enzymes are very specific, they can control who is in charge of the reaction (lock and key model)
Active site = where the substrate binds to
Allosteric site = site other than active site, when something binds here it changes the enzyme, which doesn’t allow the reaction to go forward since change in shape = change in function for the enzyme

Question 31

Which 3 macromolecules are most abundant (by weight) in an E. coli cell?

Answer 31

Protein, RNA, phospholipids

Question 32

Substrate Level Phosphorylation

Answer 32

Transfer of high energy phosphate bond to ADP to make ATP

Question 33

What are two ways to synthesize ATP?

Answer 33

-substrate level phosphorylation
-transmembrane ion gradient

Question 34

Competitive Inhibition

Answer 34

A competitive inhibitor competes for binding to the enzyme’s active site

Question 35

Can CO2 be used as an energy source?

Answer 35

No

Question 36

Define: oxidation, reduction. Of the following pairs of compounds, state which is more highly reduced: H2O vs. O2; C6H12O6 vs. CO2; NAD+ vs. NADH; Fe3+ vs. Fe2+.

Answer 36

➟ Oxidation: the loss of electrons
➟ Reduction: the gain of electrons

➟ H2O2 vs. O2: H2O2 b/c gain of H
➟ C6H12O6 vs. CO2: C6H12O6 b/c gain of H. Also b/c glucose is a known energy source but CO2 is fully oxidized, so it has no harvestable energy.
➟ NAD+ vs. NADH: NADH b/c gain of H
➟ Fe^3+ vs. Fe^2+: Fe^2+ b/c gain of electrons

Question 37

What are examples of organic carbon sources?

Answer 37

Lipids, carbohydrates, proteins

Question 38

What are sulfa drugs example of?

Answer 38

Competitive inhibitors of the bacterial enzyme for making folic acid

Question 39

Why does fermentation yield less ATP?

Answer 39

Because it needs to regenerate NAD+ so pyruvate is reduced to yield lactate

Question 40

Who carries out fermentation for fueling and why?

Answer 40

Heterotrophs because fermentation only uses organic molecules as substrates

Question 41

Define fermentation

Answer 41

Process in which organisms convert carbohydrates into alcohol or acids