Cholesterol and Protein Metabolism

Created by pantherrob82 

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What is cholesterol the precursor to?

bile salts and steroid hormones

What is the precursor to steroid synthesis?

pregnenolone

What is a ketoacid?

what is left when the amino group is removed from an amino acid

Where is the amino group from a ketoacid normally transferred?

to another ketoacid

What area a-ketoacids used for?

ATP+H2O+CO2, glucose, ketones, and fatty acids

What do we get when we add NH3+ and pyruvate?

alanine

Alanine -NH3=?

pyruvate

Glutamine-N=?

glutamate

glutamate - NH3+=?

a-ketoglutarate

a-ketoglutarate+NH3+=?

glutamate

glutamate+ NH2+=?

glutamine

Pyruvate, a-ketoglutarate and oxaloacetate are?

a-ketoacids

oxaloacetate +NH3+=?

aspartate

aspartate +NH2=?

asparagine

What are the purely ketogenic amino acids?

leucine and lysine

Are carriers inducible?

yes, the body can make more or less of them

What is absorbed faster, BCAAs or smaller amino acids?

BCAAs

What is absorbed more, peptides or free AAs?

peptides

What % of absorption is peptide?

67%

What % of absorption is free amino acid?

33%

What happens to peptides once into the enterocyte?

broken down to free AAs for the blood

What is the function of the gamma-glutamyl cycle?

to get an amino acid into a cell

What happens in the gamma-glutamyl cycle?

glutamate breaks off glutathione and escorts amino acids into cells

What is glutathione?

an antioxidant

What is the primary site for amino acid uptake following a meal?

liver

What % of amino acid uptake takes place in the liver after a meal?

50-65%

What amino acids is skeletal muscle able to oxidize?

leucine, isoleucine, valine, glutamate, aspartate, and asparagine

How much of protein is found in its free form in the free amino acid pool?

less than 2%, 200 grams

What is the ratio of intracellular to extracellular glutamate?

>50 to 1

What is anaplerosis?

adding to the pathway

What is cataplerosis?

taking from the pathway

What are the two products of an amino acid being broken down?

NH3 and a-keto acids

What enzyme is lacking in skeletal muscle?

glucose 6 phosphatase

What is the function of glucose 6 phosphatase?

to form glucose to be released into the blood

Because muscle is lacking glucose 6 phosphatase, how does it release glucose into the blood?

the cori cycle and the glucose-alanine cycle

What are the steps of the cori cycle?

muscle glycogen ->glucose 6P ->pyruvate->lactic acid ->to liver ->pyruvate->glucose -> to blood

What are the steps of the glucose-alanine cycle?

muscle glycogen->glucose 6P->pyruvate->alanine->to liver->pyruvate->glucose ->to blood

How does the glucose-alanine cycle maintain blood glucose?

gluconeogenesis

What is the main source of nitrogen?

glutamine

What are the steps of the glutamine-glutamate cycle?

muscle imports glutamate, muscle turns glutamate into glutamine, glutamine goes to cells needing nitrogen, glutamine turns back into glutamate, glutamate goes back to the muscle

How does muscle turn glutamate into glutamine?

glutamine synthetase adds nitrogen to glutamate, nitrogen is taken from amino acids

What cells need nitrogen?

gut and immune cells

How is glutamine turned back to glutamate?

glutaminase hydrolyzes glutamine

How are most amino acids released?

in proportion to their relative occurrence in muscle protein

What amino acids are not released in proportion to their relative occurrence in muscle protein?

leucine, isoleucine, valine (BCAAs), glutamate, aspartate, asparagine, glutamine, and alanine

What amino acids are released in amounts less than what is taken in?

BCAAs, glutamate, aspartate, and asparagine

What are the most abundantly released amino acids?

glutamine and alanine (50% and 30%)

When is there a large uptake of BCAA and glutamate?

after eating

Describe the uptake of BCAA and glutamate after eating:

large uptake: more than 90% of muscle amino acid uptake

Why doesn't the gut have a large uptake of BCAAs?

it lacks sensitivity

What happens to muscle release of glutamine after eating?

it more than doubles

What is a large source of ATP creation for muscle?

BCAA

What inhibits pyruvate degradation during starvation?

BCAAs, allowing pyruvate(lactate or alanine) to leave for gluconeogenesis

What is the function of alanine aminotransferase in muscle?

to take the NH3 group from gluatamte and give it to nitrogen, forming alanine and a-ketoglutarate

What is low intensity exercise?

25% of VO2 max

What is the effect of low intensity exercise on skeletal muscle glutamate concentration?

20% decrease

What is the effect of low intensity exercise on skeletal muscle alanine concentration?

no change

What is moderate intensity exercise?

50% of VO2 max or more

What is the effect of moderate intensity exercise on skeletal muscle glutamate concentration?

40% decrease during the first minute

What is the effect of moderate intensity exercise on skeletal muscle alanine concentration?

40% increase in first minute

What is the effect of moderate intensity exercise on skeletal muscle glutamine concentration?

relatively constant

What happens to glutamate plasma concentration during exercise?

decreases

What happens to alanine plasma concentration during exercise?

increases

What happens to glutamine plasma concentration during exercise?

increases

What happens to glutamate intake in the initial phase of moderately intense exercise?

increases 1-3 fold

What happens to glutamine and alanine intake in the initial phase of moderately intense exercise?

increases 2-9 fold

On the graphs, which graph represents glutamate?

the one with drops

On the graphs, which graph represents alanine?

the one with increases

What happens to ATP turnover during exercise?

it can increase 100 fold

What happens to TCA intermediates during exercise?

increase 4-10 fold

What is the main player in anaplerosis?

glutamate

What is the substrate of TCA cycle?

acetyl CoA

What do we need to meet the ATP demands during exercise?

more TCA intermediates to combine with oxaloacetate, malate, succinate and fumarate all increase 5-6 fold

Why do we run fast glycolysis?

to create anaplerosis for the TCA

What is essential for exercising at high workloads?

muscle glycogen

What is responsible for the elevation of TCA cycle intermediates?

glycogen and alanine aminotransferase (ALT)

Can nitrogen be stored in the body?

no

Where is nitrogen sent?

the liver

What happens to excess amino acids?

they are degraded

How do we remove the amino groups from amino acids?

transamination, oxidative deamination

How is nitrogen excreted?

as urea

Why is nitrogen going to the liver?

ate too much protein, gluconeogenesis (exercise, starvation, not eating carbs)

Where does transamination happen?

liver and skeletal muscle

What do most amino acids transfer their amino group to?

a-ketoglutarate

amino acid+a-ketoglutarate=?

glutamate and an a-keto acid

What enzyme transfers amine groups from amino acids to a-ketoglutarate?

aminotransferases

What are the main ways nitrogen leaves the muscle?

glutamine and alanine

What enzyme is required to continually form glutamine and alanine?

transaminases

Where do oxidative deamination, carbomoyl phosphatase and the urea cycle take place?

liver

What is ALT?

alanine aminotransferase

Where is ALT found?

muscle and liver

What is the function of ALT in muscle?

change pyruvate+glutamate to alanine+a-ketoglutarate

What is the function of ALT in the liver?

change alanine+a-ketoglutarate to pyruvate+glutamate

What is GDH?

glutamate dehydrogenase

What is the function of GDH?

change glutamate+NAD+ to a-ketoglutarate+NH3 + NADH

What is AST?

aspartate aminotransferase

What is the function of AST?

transfers amino groups from glutamate to oxaloacetate forming aspartate, glutamate+OAA to a-ketoglutarate + aspartate

What are the key liver enzymes?

ALT and AST

What is the function of the urea cycle?

the livers way of dealing with ammonia

What is the function of gluconeogenesis?

liver turns a-ketoacids into glucose

How does 86% of the nitrogen leave the body?

urea

What is the function of carbamoyl phosphatase?

catalyzes CO2+NH3+2ATP to carbamoyl phosphate, the entry point of the urea cycle

Where is carbamoyl phosphatase found?

liver

What three things can enter the urea cycle?

carbamoyl phosphate, aspartate, and H2O

What are the four intermediates of the urea cycle?

citrulline, argininosuccinate, aginine, and ornithine

What are the products of the urea cycle, starting with ornithine?

ornithine+carbamoyl phosphate = citrulline +aspartate= argininosuccitate-fumarate= arginine +H2O= urea

What is the structure of urea?

H2N-C=O-NH2, Ns bond to C

How many nitrogen molecules on urea?

2

Where do the two nitrogens on urea come from?

one from aspartate, one from free NH3

What is the precursor for NH3 and aspartate?

glutamate

What conversion gives us free NH3?

glutamate to alpha KG

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