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45 Cards in this Set

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1. Why do we need amino acids?

Five reasons...
1. Protein synthesis
2. Synthesis of important N compounds
3. Use of carbon skeletons for fuel
4. Use of carbon skeletons to make glucose and ketone bodies
(important fate by mass)
5. Use of C requires excretion of amino nitrogen (urea/urine)
2. What are some important compounds synthesized from amino acids?
1. Neurotransmitter
-GABA
-Serotonin
-Melatonin
-Norepinephrine
2. Glutathione
3. Heme
4. Nucleotide bases
-pyrimidines
-purines
5. Creatine-P (NRG reservoir in muscles)
3. What are the 10 essential amino acids?
1. Lysine (basic)
2. Histidine (basic)
3. Arginine (basic)
4. Leucine
5. Isoleucine
6. Valine
7. Threonine
8. Tryptophan
9. Phenylalanine
10. Methionine (S containing AA)
4. What charge do the basic amino acids have?

What are the branched AAs?

What are the aromatic AAs?

When is arginine required?
Positive

Leucine, isoleucine, threonine, valine

Tryptophan, phenylalanin

During growth (not adulthood)
**make alot in synthesis of urea
5. What will the body do if an essential AA is missing?
Break down muscle protein to get it causing wasting
6. What is the 2 C non-essential AA?

What are the 3 C non-essential AA?

What are the 4 C non-essential AA?

What are the 5 C non-essential AA?
Glycine

Serine, cysteine (S), alanine

Asparate, Asparagine

Glutamate, Glutamine, Proline, Arginine (except in growing children)
7. What are the non-essential AA made from essential AA?
Tyrosine (from phenylalanine)

Cysteine (from methionine)
8. What is meant by "complimentary proteins"?

Give an example
Some plant protein sources are incomplete so remedy by consuming together

Legumes lack methionine
Grains lack lysine
**consume them together
9. What can low methionine cause?

What can low lysine cause?
Retard growth in children

Hinder growth in children
10. What do most AA produce?
Glucose (glucogenic)

-feed into TCA cycle to then form new glucose
11. What do the 3C AA form?

What do the 4C AA form?

What do the 5C AA form?

What do the branched chain AA form?
Pyruvate

Oxaloacetate

α-ketoglutarate

Succingyl CoA
12. What are the only long term storage forms of energy in the body?

What can FAs only form?

What can AA form?

In a fast what happens then?
Protein and Fat

Acetyl CoA (cannot form glucose)

New glucose (and KB)

12 hr+ skeletal muscle degrades to make new glucose (lots of urea is also made)

**Bulk of AA are gluconeogenic (use in long term fast like overnight)
13. What are the only 2 AA that can only form KB and not glucose?

What other AA are ketogenic as well as gluconeogenic?
1. Lysine
2. Leucine

Threonine, Isoleucine, Tryptophan, Phenylalanine, Tyrosine
14. What role does chewing play in protein digestion?

Does saliva contain proteases?

What role does cooking food and HCl from the stomach play in protein digestion?
Expose proteins

No

Denature proteins so more susceptible to digestive processes
-breaking down fibers and membranes to make proteins available
15. What does pepsin do in protein digestion?

What role does bicarbonate (released from the pancreas) play in protein digestion?

What are the precursors to proteases found in the intestines?
Cut proteins up into smaller pieces

Neutralize HCl from stomach in intestines

Trypsinogen
Chymotrypsinogen
Preelastase
Precarboxypeptidases A and B

**Have to also digest these digestive enzymes which have a lot of protein in them
16. What is the precursor for pepsin and trypsin?
Trypsinogen
17. What is pepsin?

Where does it cleave?
Stomach protease

Cleave after glutatate (Glu), asparatate (Asp), and some aromatic AA (tyrosine and phenylalanine)
18. From where is trypsin secreted?

Where is it found?

Where does it cleave?
Secreted from pancreas

Only in gut

Cleave to carboxy side of either arginine (Arg) or lysine (Lys)
19. What is zymogen activation?
Zymogen is the proenzyme or precursor form that is secreted by the pancreas

In order to form the active enzyme there must be activation of the zymogen
20. What is the zymogen of pepsin?

How is it activated?

Where is pepsin active?
Pepsinogen

Activates self with H+

Pepsin is only active in stomach
21. What is the zymogen of trypsin?

What activates it?

What is special about trypsin?
Trypsinogen (secreted by pancreas)

Enteropeptidase

It activates most other gut proteases
22. Pepsin...
1. Location
2. Cleavage type
3. Cleaves after
4. Zymogen
5. Activation
6. Key Role
1. Stomach
2. Endoprotease
3. Phe, Tyr, Glu, Asp
4. Pepsinogen
5. By acid, by pepsinogen
6. First protease
23. Trypsin...
1. Location
2. Cleavage type
3. Cleaves after
4. Zymogen
5. Activation
6. Key Role
1. Intestine
2. Endoprotease
3. Lys, Arg
4. Trypsinogen
5. Enteropeptidase
6. Activates other zymogens
24. How are AA transported from the intestinal lumen to the portal vein or serosal side?
1. Pull AA into cell w/ Na+
-sodium linked carriers
-broad specificities
-same transporters in gut, kidney

2. Facilitated transporter carriers cell out to serosal side
25. What are the 4 major nitrogenous urinary excretory products?

Why must we dispose of N?
1. Urea (12-20 g urea N)
2. NH4+ (140-1,500 mg)
3. Creatinine (14-26 mg/kg females)
(11-20 mg/kg males)
4. Uric Acid (250-750 mg)

Must dispose of N to use carbon skeletons (α-keto acids)
26. Describe urea.

Four points
1. Neutral molecule

2. Soluble

3. Non-toxic to mammals

4. Doesn't contain a lot of energy
27. Why is NH4+ not a good excretion molecule?
1. Charged
-need to couple positive charge w/ negative charge

2. Soluble BUT toxic to mammals (neural toxicity)
28. What can creatine levels indicate and why?

What is creatine proportional to?
How is at getting rid of small molecules (kidney function indicator b/c it's a specific breakdown molecule)

Muscle mass (less muscle, secrete less creatine)
29. What is uric acid a product of?

Describe uric acid?
Purine breakdown

Insoluble
-white crystalline mass
30. What happens in the aminotransferase reaction?
Get N from any AA and trap it in glutamate

AA1 α-Keto acid1

α-Keto acid 2 AA2

**use PLP
31. How are AA1 and α-Keto acid 1 related?

What is the C skeleton of glutamate?

From what vitamin is PLP derived from?
α-keto acid 1 is C skeleton of AA1

α-ketoglutarate
**capture N in form of glutamate

B12
32. What are some characteristics of aminotransferases?

Three things...
1. Freely reversible: N goes both directions

2. An AT exists for nearly every AA

3. Most use Glutamate/α-ketoglutarate as one substrate produce pair
33. Describe the reaction in which glutamate dehydrogenase catalyzes?
Glutamate <----> α-ketoglutarate

-freely reversible
-NADP dependent
(form NADPH if form α-ketoglutarate)

Form NH4+ when form α-ketoglutarate
34. How can you form ammonia?

Five ways....
1. Glutamate dehydrogenase (GDH) reaction (glutamate -> α-ketoglutarate)

2. Asparagine -> Aspartate

3. Histidien -> Urocanate

4. Purine nucleotide cycle in muscles

5. AA to various products
35. How do you get N into urea?
1. Transamination
-take N from AA and trap in glutamate

2. GDH
-glutamate to NH4+

3. NH4+ into urea cycle to form urea

4. Glutamate to aspartate which enters urea cycle
36. From where does the urea cycle ge the 2 N atoms it needs?
1. One from ammonia (NH4+)

2. One from aspartate)
37. Where do the reactions of the urea cycle take place?

How is analogous to the TCA cycle?
Mitochondria (liver cells)
Cytosol

Cyclic
Regenerate intermediates
38. What is the first reaction of the urea cycle in the mitochondria?

What is the enzyme involved?

What else?

What does the product do?
Bicarbonate + NH4+ -> Carbamoyl P

Carboamoyl phosphate synthetase I
(CPS I)

2 ATP

Activated form of amino group that transfers it on to other groups
39. What is the second reaction of the urea cycle in the mitochondria?

What is the enzyme involved?

What happens to the end product?
Carbamoyl P + Ornithine -> Citrulline

Ornithine transcarbamoylase

Transport citrulline out of mitochondria into cytosol
40. Where does the second N in the urea cycle come from?

What is an interesting intermediate in the urea cycle?

What does the urea cycle regenerate that it uses?
Aspartate

Arginine
**this arginine doesn't escape from liver cells to supply rest of body w/ arginine

Ornithine
41. What enzymes collaborate to send N to urea?
Aminotransferases and GDH
42. What regulates the Urea cycle?
(four)

Which step is regulated?
1. NAG
2. Glutamate
3. Ammonia
4. Arginine

First step at CPS I
43. How does NAG affect CPS I?

How does arginine affect NAG?

How does glutamate affect NAG?
CPS I has allosteric activator (NAG) that is necessary
**NAG only activates CPS I when levels build up

NAG synthesis is allosterically activated by arginine

Glutamate is used to make NAG
44. How is urea production during fasting?

When is urea production the highest?
Increases

B/c taking apart muscles/AA and the N is captured in urea

Highest 12 hrs fasting
45. Why does urea production diminish after 5-6 weeks of fasting?
Tissues that were dependent on glucose now use KB

Spare blood glucose so spare muscle degradation