Chapter 5- Microbial Metabolism

Question 1

Properties of a metabolic pathway

Answer 1

determined by enzymes, and allows organisms to release and store energy in a series of controlled reactions as opposed to a single burst that would be very inefficient (much of the energy would be lost in the form of heat).

Question 2

What determines whether a chemical rxn will occur from the collision?

Answer 2

speed of the particles, orientation of the particles, and the activation energy required for the rxn.

Question 3

How can you increase non-biological reaction rates?

Answer 3

increasing temperature, concentration, or the pressure.

Question 4

Activation energy

Answer 4

the amount of collision energy needed for a chemical rxn.

Question 5

Reaction rate

Answer 5

how fast or slow a rxn takes place determined by the frequency of collisions containing sufficient energy to bring about a rxn.

Question 6

enzyme characteristics?

Answer 6

generally globular, acts on a specific substance(s), and its substrate(s), catalyzes only one reaction, can operate at physiological temperatures, subject to various cellular controls, and does not always bind just one substrate.

Question 7

how do enzymes lower the activation energy?

Answer 7

proximity and orientation: enzyme orients substrate into position that increases the probability of a successful rxn.

Question 8

What allows the release of an enzyme’s products?

Answer 8

upon completion of the rxn, the products no longer fit in the active site, so they are then released.

Question 9

Effects of pH on enzyme?

Answer 9

extreme pH changes the enzyme’s 3D structure, because H+ and OH- compete with its hydrogen and ionic bonds

Question 10

Example of a competitive inhibitor?

Answer 10

Sulfanilamide; PABA is needed to synthesize to produce folic acid and sulfanilamide competes with PABA. Sulfanilamide isn’t toxic to mammals because they get their folic acid in the form of a B vitamin. And bacterial cells cannot use folic acid from their environment because they cannot transport it across the cell.

Question 11

Examples of enzyme poisons

Answer 11

Cyanide: binds the iron in iron-containing enzymes cytochrome).

Fluoride: binds Ca2+ or Mg2+

Question 12

3 Mechanisms to generate ATP?

Answer 12

Substrate-level phosphorylation: a high-energy phosphate from a catabolic intermediate is transferred to ADP or GDP.

Oxidative phosphorylation: e-‘s from molecules are used to reduce e- carriers such as NAD+ and FAD that pass their e-‘s to the ETC. This carries protons and e-‘s, which results in e-‘s going to acceptors and the transportation of protons across a membrane to establish a proton gradient.

photophosphorylation: occurs only in photosynthesis, and light energy is converted to ATP and NADPH.

Question 13

Glycolysis

Answer 13

AKA EMP pathway, the breakdown of 1 glucose molecule into 2 NADH and 2 ATP molecules and 2 pyruvates; consists of a preparatory stage and an energy conserving stage.

Question 14

Prep stage of glycolysis

Answer 14

2 ATP are used; glucose is phosphorylated, isomerized, phosphorylated and then split into 2 glyceraldehyde-3-phosphate molecules.

Question 15

Energy-conserving stage of glycolysis

Answer 15

2 G3Ps are oxidized to 2 pyruvates with a yield of 4 ATPS (remember: 2 ATP NET), and 2 NADH produced.

Question 16

Other pathways for prokaryotes to oxidize glucose?

Answer 16

Pentose phosphate pathway and ED pathway.

Question 17

Pentose phosphate pathway

Answer 17

Can be used with glycolysis or ED pathway, breaks down 5-C sugars/glucose to produce 2 mol of NADPH for each glucose; has intermediates that can be used to synthesize amino acids, nucleic acids and other macromolecules.

Question 18

ED pathway

Answer 18

catabolize glucose to pyruvate without glucose or pentose phosphate pathway. produces 1 ATP, 1 NADPH and 1 NADH for each mol of glucose; present in some gram - bacteria.

Question 19

Krebs cycle

Answer 19

oxidation/reduction rxns that transfer the PE of acetyl-CoA to e- carrier coenzymes (NADH mainly, and FADH2); ATP is also produced via substrate-level phosphorylation. For every 2 mol of acetyl CoA=> 4 mol of CO2, 2 mol ATP, 6 mol of NADH and 2 mol of FADH2.

Question 20

Carriers in ETC

Answer 20

Flavoproteins: flavin mononucleotide (FMN>FMNH>FMNH2)

Cytochromes: proteins with heme.

Question 21

Complexes in ETC

Answer 21

1- pumps H+'s 
2- transfers e-'s to ubiquinone
3- pumps H+'s
4- pumps H+'s
5- ATP synthase

Question 22

Fermentation

Answer 22

anaerobic process where an organic molecule can be oxidized using an organic molecule as an e- acceptor to produce small amounts of ATP.

Question 23

Lactic acid fermentation

Answer 23

Homolactic- only lactic acid

heterolactic- produces lactic acid and other compounds.

Question 24

lipid catabolism

Answer 24

Lipids are broken down in the extracellular space by lipases to break down triacylglycerol into fatty acids and glycerol.

Question 25

Protein catabolism test

Answer 25

1. Tests for the decarboxylation of an amino acid that will produce a higher pH which will test positive (even though the microbe will be fermenting the glucose).
2. Testing for the desulfurylation of cysteine where the medium contains iron and it tests if H2S is produced because once H2S forms iron sulfide, it will show as a black precipitate.

Question 26

Urease

Answer 26

tests for the catabolism of urea (urea > ammonia and CO2) . A positive test results from the hydrolysis of urea which will produce ammonia that leads to a higher pH.

Question 27

Photosynthesis

Answer 27

Has oxygenic and anoxygenic (photosystem 1 only)

oxy- 6CO2 + 12H2O + light = glucose +6 H2O + 6 O2

anoxy- 6CO2 + 12H2S + light = glucose +6 H2O + 12 S

Question 28

Stages of photosynthesis

Answer 28

Light dependent (photophosphorylation)- light energy converts ADP and Pi into ATP

Light independent rxns (calvin-benson)- e-‘s and ATP are used to reduce CO2 to sugar.

Question 29

2 types of photophosphorylation

Answer 29

cyclic- e-‘s released from chlorophyll in photosystem 1 return back to chlorophyll, O2 isn’t produced, energy from e- transfer is used for ATP synthesis.

noncyclic- e-‘s from chlorophyll leave as NADPH (energy from e- transfer is converted to ATP and NADPH; photosystem 2 regains e-‘s by splitting water , leaving O2 a a product

Question 30

products of the calvin-benson cycle

Answer 30

fixation of CO2; 3 turns of the cycle produce 1 G3P (6 turns in total are needed for 1 glucose)

so the total needed for 1 glucose molecule: 6 CO2, 18 ATP, 12 NADPH