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Phys Exam two > amino acid metabolism > Flashcards

amino acid metabolism Flashcards

1
Q

when is protein synthesis occurring and what does degradation do?

A

protein synthesis and degradation are constantly happening. Degradation removes old/damaged proteins, serves as a regulation point, releases free AA which can be used to synthesize new proteins

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2
Q

how many proteins are degraded per day?

A

1-2%

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3
Q

why are new AA necessary?

Not all AA can be what?

A

to replace proteins and not all amino acids can be recaptured or reused.

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4
Q

Essential AA - PVT TIM HALL

A

Phe, Val, Thr, Trp,Ile, Met, His, Arg, Leuc, Lys

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5
Q

Non-essential AA

A

Ala, Asn, Asp, Cys, Glu, Gly, Gln, Pro, Ser, Tyr

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6
Q

species/age dependent amino acids

A

Arg, His

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7
Q

Which AA are branched chained AA? Branched Chained AA are a major component of what? How much skeletal muscle is made of BCAA? Used by? Metabolized where?

A

BCAA (leu, ile, val) are a major component of muscle, 1/3 skeletal muscle proteins, used by brain to synthesize neurotransmitters, liver does not have enzymes to metabolism these so occurs in muscle.

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8
Q

BCAA means?

Are the bonds easy to make or break?

A

There is a branch in the chain, branching means much more complicated to metabolism, not an easy bond to make or break

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9
Q

BCAA necessary for creating what component of muscle?

A

Actin/myosin

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10
Q

Incorrect amount of BCAA in the body can lead to?

A

problem in the brain

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11
Q

Where are proteins hydrolyzed? what are they broken down into?

A

Hydrolyzed in the stomach and small intestine into AA.

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12
Q

Stomach role in proteins

A

stomach is acidic and secretes pepsinogens which are activated by the acid for initial cleavage of proteins

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13
Q

Pancreas role in proteins

A

Pancreas secretes several strong proteases (trypsinogen, chymotrypsin) which are activated in the duodenum to contain protein cleavage. Products of this are free AA and short 2-3 AA peptides

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14
Q

How are neonates different regarding stomach acid?

A

They dont produce enough stomach acid in the first few days of life and colostrum contains a trypsin inhibitor so they do not cleave proteins. Proteins can be absorbed whole for first 2-3 days, facilitates transfer of whole immunoglobulins for maternal immunity.

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15
Q

Why is it important for proteins to be absorbed first 1-2 days for neonates?

A

allows us to get antibodies in the small intestine without being digested.

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16
Q

when and where are the AA and peptides absorbed? What absorbs them?

A

after cleavage, AA and short peptides absorbed in duodenum and jejunum by intestinal epithelial cells

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17
Q

How are the small peptides turned into free AA after cleavage?

A

intestinal epithelial cells hydrolyze them.

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18
Q

What happens after all AA are free AA?

A

They are absorbed and processed and transported into the blood where they enter portal circulation to go to the liver.

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19
Q

How are AA transported into the blood?

A

via concentration gradient.

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20
Q

Why are AA going to the liver after put into blood circulation?

A

The liver is the first processing point of aa.

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21
Q

How are basic AA absorbed across the epithelial membrane?

A

SLCA19 - Na+

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22
Q

How are acidic AA absorbed across epithelial membrane?

A

SLCA 14 - Na+, Cl-

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23
Q

How are di or tripeptides absorbed across the epithelial membrane?

A

SLCA15A1 - H+

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24
Q

How are neutral AA absorbed across the epithelial membrane?

A

SLCA15 - Na+

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25
Q

AA used for gluconeogenesis and ketogenesis, why and which ones?

A

phenylalanine, tyrosine, threonine, tryptophan, isoleucine due to their carbon backbone.

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26
Q

AA used in TCA cycle or to form ketone bodies are..

A

leucine and lysine

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27
Q

What does ketogenic mean? What will those AA form?

A

means they will never form glucose, they form acetyl-coA which can never be processed back to glucose

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28
Q

First step of AA catabolism and what happens?
What about the second step?
What are the products and where do they go?

A

Transamination followed by deamination.
Transamination - remove amine group from AA and replace it with an oxygen to form pyruvate, the amine is transferred to alpha-ketoglutamate which then forms glutamate.

Deamination
Need to get a-ketogluterate back to deal with amine so we take it off of glutamate and turn it into free ammonium and NADH which goes to the ETS

29
Q

C2, C3 and Tryptophan converted to what amino acid?

What is C2 and C3?

A

C3 - 3 carbon AA can be converted into pyruvate
C2 - two glycines can be converted to pyruvate
Tryptophan and threonine can partially be converted to pyruvate (tryptophan is converted to alanine instead which leads to pyruvate) Threonine is converted to two glycines > pyruvate

30
Q

What can we do with pyruvate?

A

use it to get to gluconeogenesis

31
Q

C4 converted to?

C4 AA are?

A

4 carbon aa converted to oxaloacetate. Aspartate requires a transamination event while asparagus requires 2 to become oxaloacetate.

32
Q

What can we do with oxaloacetate?

A

Can use it to get back to gluconeogenesis.

33
Q

C5 and C6 - what are they and what do they convert to

A

5 or 6 Carbon AA converted to glutamate which then can be transaminated or deaminated to alpha keto gluterate

34
Q

Where is alpha-ketogluterate used and what can it make?

A

Used in the TCA cycle, keep going around until we get oxaloacetate which can lead to gluconeogensis

35
Q

What can BCAA be converted to, how, and where?

A

methionine and some BCAA can form propionyl-coA. BCAA transaminated in skeletal muscle. Transamination produces alanine and glutamine (major exports of skeletal muscle during starvation). Their carbon backbones eventually converted to succinyl co-A

36
Q

What is propionyl-CoA in?
What can it be converted to? In what cycle?
Carbon backbones are converted to?

A

Propionyl-coA is in VFA’s, when its put into gluconeogenesis it is converted to succinyl co-A which can be turned into oxaloacetate and converted into gluconeogenesis.
Backbones > succinyl co-A

37
Q

What AA are exported from muscle during starvation conditions?

A

alanine and glutamine sent to liver to make glucose

38
Q

Aromatic AA?

Metabolized where?

A

PHe/Tyr

liver

39
Q

liver function measured by what radio

A

BCAA:AAA

40
Q

what can liver failure cause?

A

liver failure can raise AAA circulation, causing neurotransmitter dysregulation in the brain

41
Q

normal BCAA:AAA ratio?

A

3:1

42
Q

Tyr and Phe (aromatic AA) converted to?

Which can be used in?

A

fumerate, which is in the TCA cycle, can go to oxaloacetate to form glucose

43
Q

Ketogenic amino acids?
what do they form?
Product used in what cycle?

A

Leucine and Lysine, forms acetoacetate which is metabolized to acetyl-coA which can enter the TCA cycle when combined with oxaloacetate to form citric acid

44
Q

What cant acetyl-coA do in the TCA cycle and why?

A

Cant donate any carbons bc the two carbons are fully oxidized as Co2

45
Q

Where does leucine become transaminated and why?

A

muscle, it is a BCAA

46
Q

where is lysine transaminated and why?

A

liver

47
Q

Glucogenic and ketogenic AA used in?
backboned converted to?
Can be used in citrate cycle when?
What happens if oxaloacetate is low?

A

gluconeogenesis, backbones go to acetyl-coA or acetoacetate. when oxaloacetate is plentiful, these can be used in citrate cycle. If oxaloacetate is low, shunted into ketone bodies.

48
Q

When are ketone bodies formed?

A

when oxaloacetate and free HS-coA have been depleted. Oxaloacetate used by gluconeogenesis while free HS-CoA used by fat or ketogenic AA

49
Q

What does ketogenesis do?

A

regenerates free HS-coA and supplies energy to tissues especially through the heart and brain through ketone bodies

50
Q

A 2 y/o irish wolfhound with sporadic progressive ataxia and recent seizures. BW shows high levels of ammonia and serum bile acid and a low ratio fo BCAA:AAA
Diagnosis?

A

Portal vein skipping the liver is a portal vein shunt which is why it looks
Like the liver isn’t processing ammonia well. It is not scavenging the
BCAA. Why does this cause ataxia and seizures?
Neurotransmitters. Both branched and aromatic amino acids are taken
Up by the brain, when the ratio gets off will first see neurological symptoms
Brain takes up AA and converts them to neurotransmitters which will
Mess up neurologic function.
Ammonia will be the other reason

51
Q

A 2 y/o irish wolfhound with sporadic progressive ataxia and recent seizures. BW shows high levels of ammonia and serum bile acid and a low ratio fo BCAA:AAA
Treatment?

A

Low protein diet, need to control NH4+ and BCAA:AAA ratio, many animals with hepatic encephalopathy are already very sick and underweight so a high protein diet is needed. High quality low protein diet needed to sustain body weight and minimize NH4+. Low protein diet enriched in BCAA - cottage cheese supplementation

52
Q

Transamination/Deamination of AA - how do we produce aspartate?

A

Through a double transamination, both NH4+ and aspartate are important in the urea cycle

53
Q

What cycles are important in urea cycle?

A

NH4+ and aspartate

54
Q

What compound is ammonia? What does it become in an aqueous solution? What can its products in an aqueous solution do to the body?

A

Strong base, highly toxic. Aqueous solution it becomes NH4+ and OH-, increasing the pH. NH4+ interferes with the brains ability to regulate K+ since they look the same based on charge.

55
Q

What can be messed up by ammonium?

A

any potassium selective channel or transporter; we will see neurological symptoms

56
Q

Urea cycle - where does it occur? inputs? outputs?

A

occurs in the liver, inputs - 2NH4+ (from glutamate), HCO3-, 3ATP, and oxaloacetate (or NAD+ in TCA cycle).
Outputs - urea, 2ADP, AMP, 4pi, and fumerate (or NADH in TCA cycle)

57
Q

Urea cycle further explanation

A

Take ammonium and combine it will bicarbonate to create carbamoyl phosphate, take ornithine and add it to the carbamoyl phosphate, release phosphate which will drive a reaction to create citrulline which is an ammonium waste attached to AA. Take citrulline and aspartate to create argino-succinate. Now we have both amines from ammonium and aspartate in one molecule. Will cleave something off of arginine and create urea, can then dump urea into blood.
Input - two amines from glutamate from transamination reactions. Oxaloacetate or TCA cycle needs to be running.
Outputs - urea
Free amine, and amino from bicarbonate come together to convert urea in the liver. Both amines came from glutamate in the transaminase reactions.
A lot of this happens in the mitochondria.

58
Q 
Step 1 of urea cycle
What steps?
Control point?
What compound is produced when glutamate is high?
occurs where?
A

Carbamoyl phosphate synthetase. Rate limiting and committed step for urea cycle/creatine synthesis.
Control point - N-acetylglutamate is an allosteric activator of CPS
N-acetylglutamate is produced when glutamate is high.
Occurs in mitochondria

59
Q

Regulation of N-acetylglutamate:
___ to ____ during transamination of AA catabolism?
Therefore, high aa catabolism leads to high concentrations of what?
What is N-acetylglutamate sythetase activated by?
what does it act as?
what does it activate?
Balances what?

A

Product of AA catabolism is glutamate, comes from a-ketogluterate during transamination.
high aa catabolism leads to high glutamate conc.
Activated by high glutamate producing N-acetylglutamate which acts as an allosteric activator for carbamoyl phosphate synthase.
Balances urea production with nitrogen waste production in aa catabolism

60
Q 
Step two of urea cycle
What is it?
Where does it occur?
\_\_\_ + \_\_\_\_= \_\_\_\_\_
Product transported to what by what?
A

Ornithine transcarbamylase - occurs in mitochondria. Ornithine combined with carbamoyl phosphate produces citrulline. Onihtine transported to mitochondria and citrulline transporte dot cytoplasm by citrulline/ornithine antiporter.

61
Q

Step three of urea cycle

What is it and wheres it occur

A

arginosuccinate synthetase occurs in cytoplasm (citrulline + aspartate = arginosuccinate)

62
Q

Step four of urea cycle, what is it and where does it occur?

A

Arginosuccinate lyase (arginosuccinate = fumerate + arginine) occurs in cytoplasm

63
Q

step five of urea cycle where does it occur and what does it restore

A

arginase, (arginine > ornithine + urea) Urea goes to blood then to urine. occurs in cytoplasm and restores onithine. urea is soluble waste

64
Q

Step 5b of urea cycle: - what is it and what does it restore?

A

L-arginine: glycine amidinotransferase.

Restores ornithine similar to arginase

65
Q

Step 6 of urea cycle, what is it?

A

Guanidinoacetate methyltransferase

66
Q

Step 7 of urea cycle
What reaction used to store high energy phosphate bonds?
what occurs during rest? what occurs during intensive work?
____ spontaneously forms ____?
What is used to assay renal function?

A

creatine kinase; the creatine phosphocreatine reaction is used by muscle to store high energy phosphate bonds.
Rest - high levels of ATP used to drive reaction forwards producing phosphocreatine.
Intense work - phsophocreatine donates a phosphate to ADP to create ATP.
Creatine kinase spontaneously forms creatine as a byproduct - used to assay renal function

67
Q

Forms of nitrogen waste

A

urea - ureotelic animals (mammals, amphibians)
Uric acid - uricotelic animals (birds, terrestrial mammals, insects)
Ammonium - aquatic animals

68
Q

Nitrogen waste toxicities high to low and water availabilities

A

ammonia, urea (moderate water availability), uric acid (low water availability)

69
Q

Uric Acid synthesis overview (avian/reptile)

What aa are involved? What are taken from them? How many? What is uric acid secreted as?

A

Generate purines off of the hexomonophosphate shunt. Bases can be taken off of purines which is nucleotide degradation > hypoxanthine > xanthine > uric acid.
Inputs will be four amino acids that have four amine groups associated with them. Take the AA and build them into the purine base and get the purine base back as uric acid. Two amines came from glutamine, one from glycine, one from aspartate. This is excreted as a solid.

Phys Exam two (13 decks)

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