Chapter 14

Question 1

Nitrogen Fixation

Answer 1

N2NH3 is a reduction that requires energy. It requires at least 16 ATP per N2. Nitrogen fixation allows many plants and animals to do synthesize many N0 containing biomolecules such as proteins and nucleic acids. Only a few prokaryotes can fix nitrogen. Plants receive their nitrogen via symbiotic relationships with N2-fixing prokaryotes or by absorbing NH3 or NO3 synthesized by soil bacteria. Animals take organic nitrogen mainly as amino acids. The liver determine that fate of ingested amino acids.

Question 2

Amino Acid Pool

Answer 2

= amino acids available for metabolic processes. Amino acids from the degradation of dietary and tissue proteins enter the pool; excreted nitrogenous end products such as urea and uric acid leave the pool. Amino acids enter cells via membrane-bound transport proteins; some are Na+-transport dependent

Question 3

Transamination Reactions

Answer 3

=the transfer of amino groups makes the synthesis of new amino acids possible. Amino groups are transferred from an alpha amino acid to an alpha keto acid, Because transamination reactions are readily reversible they play an important role in both the synthesis and

Question 4

Nitrogen Balance

Answer 4

• Nitrogen balance
– Positive: Nintake> Nloss; pregnancy, infants, recuperating patients
– Negative: Nintake< Nloss; malnutrition, Kwashiorkor

Question 5

One-carbon Metabolism

Answer 5

 Carbon atoms have several oxidation states
 Those of interest are found in methanol, formaldehyde, and formate
 The most important carriers of one-carbon groups are folic acid and S-adenosylmethionine

Question 6

NucleoTide=

Answer 6

The total package: sugar + base + Phosphate Too

Question 7

NucleoSide=

Answer 7

Sugar+Base (purines and pyrimidine

Question 8

Which amino acids contribute to the making of purine and pyridine ring atoms?

Answer 8

Purines: Adenine, Guanine, Hypoxanthine
Pyrimidine: Cytidine, Uracil, Thymine

Question 9

1) Identify the major nitrogen donors in the Urea cycle.

Answer 9

**Glutamate= synthesis of amino acids from α-ketoacids.
Glutamine
Alpha ketogluterate

Question 10

**What does synthesis of the allosteric regulating compound indicate?

Answer 10

1. AMP inhibits the formation of adenylosuccinate, a precursor to AMP. GMP inhibits the formation of xanthylate, a precursor to GMP.
2. GTP stimulates the synthesis of AMP, while ATP stimulates the synthesis of GMP.

Question 11

Identify the 2 components of the Nitrogenase complex and list their function.
Is Nitrogen Fixation energy favorable?

Answer 11

Nitrogenase=aka, MoFe protein, uses P cluster and MoFe cofactor prosthetic groups and catalyzes the reaction N2 to 2NH3
Reductase= also called iron protein, transfers electrons from ferredoxin to nitrogenase
Requires 16 ATP per N2 so it is unfavorable

Question 12

Is it seen in aerobic or anaerobic organisms?

Answer 12

Anaerobic- to protect from O2

Reaction:
N2+8H+8e  2NH3 +H2

Question 13

Name the precursors of each family of amino acids:

Glutamate= 
Serine= 
Aromatics= 
Aspartate= 
Pyruvate=
histidine=

Answer 13

Name the precursors of each family of amino acids:

Glutamate= Alpha-ketogluterate
Serine= Glycerate-3-Phosphate
Aromatics= Phosphenolpyruvate
Aspartate= Oxaloacetate
Pyruvate=pyruvate
histidine= Ribose-5-Phosphate

Question 14

Q: What is Folic acid converted into it allow for single carbon fixation?

Answer 14

THF

Question 15

1.) What are the six amino acid biosynthetic families?

Answer 15

Oxaloacetate, alpha ketoglutarate, pyruvate, 3 phosphoglerate, phosphoenolpyruvate+erythrose 4-phosphate, ribose-5-phosphate

Question 16

2.) What’s the function of Tetrahydrofolate (THF)?

Answer 16

To carry one carbon groups such as methyl, methylene, formyl, formimino, methenyl

Question 17

What is the most common method of regulation in nitrogen metabolism synthesis?

Answer 17

Purine Nucleotide Biosynthesis Regulation that is controlled to a considerable degree by PRPP

Question 18

In the nitrogen fixation phase of nitrogen metabolism, what is the energy requirement to convert atmospheric nitrogen gas to a usable form?

Answer 18

16 ATP per N2

Question 19

What is the difference between essential and non-essential molecules?

Answer 19

Essential: must be provided by diet LLe, Leu, Lys, Met, Phe, Thr, Trp, Val
Nonessential: can by synthesized from available metabolites: Ala, Arg, Asn, Asp, Cyc,Glu,Gln,Gly,His,Pro,Ser,Tyr

Question 20

Which amino acids/aa derivatives function as neurotransmitters? What neurotransmitters? , Table 14.4 pg 535

Answer 20

Glycine-norepinephrine
Glutamate-epinephrine
GABA- Dopamine, Serotonin, Histamine

Question 21

List the two most important carriers of one-carbon groups which participate in one-carbon metabolism

Answer 21

Folic Acid and S-adenosylmethionine

Question 22

What are the precursors for the novo synthesis of pyrimidines?

Answer 22

Bicarbondate, carbamoyl phosphate, aspartate

Question 23

What is the most common form of useable Nitrogen?

Answer 23

amino acids

Question 24

What is cumulative feedback inhibition?

Answer 24

In cumulative inhibition, each inhibitor can reduce the activity of the enzyme, even when other inhibitors are bound at saturating levels. The enzymatic activity of glutamine synthetase is switched off almost completely when all final products are bound to the enzyme

Question 25

Nitrogen fixation

Answer 25

N2+8e- + 16ATP + 10H+  2NH3 + 16ADP + 16Pi + H2