AA Transport & Metabolism (LM 11.1) Flashcards
what does nitrogen balance mean?
that the total amount of nitrogen in the body is stable over time
aka the body’s input vs. output of nitrogen in nitrogen containing compounds is equal on an ongoing basis
healthy humans are generally in nitrogen balance
what is a large amount of the body’s nitrogen a part of?
a large amount of the body’s nitrogen is comprised of nitrogen in AA in proteins
what are the body’s sources of nitrogen?
- incoming protein (AA) from the diet
- normal or pathological protein turnover in tissues
- turnover of other nitrogenous compounds such as nucleotides and ammonia produced by gut bacteria
what are the two ways of getting rid of excess nitrogen in the body?
- urea from the liver
2. ammonium ion by the kidney
how is nitrogen present in the body?
ammonia or ammonium
free ammonia or ammonium is actually very toxic so the body takes a lot of care to minimize the levels of these
what is the first step in AA catabolism? what happens to what’s left?
removal of their alpha-amino group
the remaining carbon skeleton is used in biosynthetic reactions or oxidized to produce energy?
what is protein turnover?
the ongoing and equally balanced synthesis and degradation of protein molecules in the body
in a healthy and well-fed adult, the total amount of protein in the body remains constant because the rate of new protein synthesis is just sufficient to replace the constant normal degradation of the body’s protein
is there a storage form of protein in the body?
NO
only carbohydrates (glycogen) and fats (TAGs) do
what’s the purpose of proteins in the body?
they do work in the body! muscles, structural proteins, enzymes, etc. all do stuff in our body
they aren’t meant to be used as energy unless you’re literally starving
fats and carbs are indeed meant for energy though
what is the body’s amino acid pool?
all the various locations and types of “free” AA in the body
the AA pool is also in balance - so what AA get taken out via output sources also get replaces from input sources
what are free amino acids? where are they found?
the single, individual AA not incorporated into proteins
they’re ready for the body to grab for bimolecular synthesis pathways at any time
they’re found in the blood, within cells, in the extracellular space
what are the 3 major sources of input into the body’s AA pool?
- body protein (the synthesis side of protein turnover)
- dietary protein (can vary)
- synthesis of non-essential AA (if dietary consumption is sufficient, then the body won’t make AA)
what are the major output sources of the body’s AA pool?
- body protein (protein degradation)
- synthesis of: porphyrins, creatine, neurotransmitters, purines, pyrimidines, other nitrogen containing compounds
- glucose & glycogen production; ketone bodies, FA & steroid synthesis; CO2 + H2O production from AA not used in biosynthetic reactions being burned as energy (varies based on energy needs)
what type of nitrogen imbalance is concerning? what is it?
negative nitrogen balance
it’s not healthy in the longer term because it means that your body is not taking in enough protein to rebuild its needs
examples:
- long term starvation/anorexia
- poor nutrient absorption
- lack of protein in diet
- other causes of muscle atrophy
what is positive nitrogen balance?
generally not an unhealthy condition
examples:
- body building to increase muscle mass
- pregnancy
- growing children
what are examples of people who would be in nitrogen balance?
- a 19 year old healthy male college student who is self-described couch potato who has been on a reduced far diet, but not low calorie diet, for the last month
- a 5 year old child who has had the flu for 1 day but is still eating normally
what are examples of people who would be in negative nitrogen balance?
- a person in late stage ALS
2. a late stage cancer patient who lost her appetite and is eating very little the last two months
what is the major form for storage of AA in the human body?
THERE ISN’T ONE!!
there is NO storage form for amino acids in the body ):
does digestion or absorption happen first?
digestion
what is digestion?
the process of degrading complete dietary proteins within the lumen of the small intestine
what is absorption?
digestion degrades dietary proteins in the lumen of the small intestine
absorption is getting these individual amino acids or di- and tri- peptides into the cells of the small intestine (intestinal enterocytes)
from there they are delivered into the blood stream for uptake into various tissues (primarily the liver)