Amino Acids Flashcards
What is the functional structure of amino acids
They’re simple, organic compounds that are the building blocks for proteins. They contain one amino group (N-terminal) and one carboxyl group (C-terminal), and are linked together with peptide bonds
Absorption of amino acids takes place where? Where do dietary proteins and amino acids not absorbed take place?
Absorption takes place in the small intestines into the bloodstream.
The ones that do not are excreted in feces
What are essential amino acids and which ones are they?
they’re the amino acids that cannot be synthesized in vivo fast enough and must be acquired by diet.
- histidine
- isoleucine
- leucine
- methionine
- phenylalanine
- theonine
- tryptophan
- valine
what are non-essential amino acids and which ones are they?
the body can synthesize adequate amounts of these, so dietary intake isn’t necessary
- alanine
- asparagine
- aspartic acid
- glutamic acid
- selenocysteine
- serine
Gastrin stimulates the secretion of what two things to promote the denaturation of proteins?
HCl (hydrochloric acid) and pepsin
Proteins catalyze almost all reactions in living cells. What are five of their functions?
- biochemical reactions
- transporting metals
- acting as receptors for hormones
- providing structure and support
- being part of the immune response
What causes maple syrup urine disease? What are some of the symptoms?
deficiency in branched chain keto acid decarboxylase. Leads to excess branched chain amino acids (valine, leucine, and isoleucine), which causes metabolic acidosis
maple syrup odor urine, seizures, coma, death
phenylketonuria is caused by what? What are some symptoms?
inability to metabolize phenylalanine
- this test is done on newborns
mousy odor urine, cerebral development loss, loss of interest, mental retardation, restlessness, and irritability
What causes cystinuria and what are some symptoms?
defect in renal tubule transport protein affecting dibasic amino acids
causes cystine kidney stones and crystalluria
what causes alkaptonuria and what are the symptoms?
inability to properly degrade tyrosine/defect in homogentistic acid
black urine and black cartilage and arthritis
What are parameters to be met when testing amino acids?
-blood samples after a fast
- heparin tube (Plasma removed)
- perform immediately or freeze at -40ºC
- urinary amino acid testing can be performed on random samples
- thin-layer chromatography
What are the five elements that make up protein structure? What are the four levels of protein structure?
Carbon, oxygen, hydrogen, nitrogen, and sulfur
- primary: number, type, and sequence of aa in a polypeptide chain
- secondary: commonly formed arrangements (alpha-helix and beta-pleated sheets) stabilized by hydrogen bonds between amino acids
- tertiary: the overall shape or conformation of the protein molecule
- quaternary: the interactions of one or more protein molecule (subunit) to function as a single unit (multimer)
What part of the protein changes the property of the protein? What determines if the protein is negatively or positively charged?
amino acid side chain (R group) changes the protein properties. Proteins are pos or neg charged due to the N- or C- terminal ends
What are the two protein groups that are not involved in the peptide bond/can exist in different charged forms depending on the pH of the surrounding environment? What happens when the pH of a solution increases?
the acid or base groups
as pH goes up,
- carboxyl groups become carboxylate
- ammonium groups to amino groups
What is the isoelectric point, and what happens when the pH increases or decreases from it?
isoelectric point: pH at which amino acid or protein has NO net charge
- pH greater than isoelectric point: net neg charge
- pH less than isoelectric point: net pos charge
Where are plasma proteins synthesized before being excreted into circulation? What is amino acids sequence determined by?
protein synthesis occurs in the liver
aa sequence determined by corresponding sequence of nitrogen bases of DNA (three-nucleotide combination = codon)
what is transcription and translation of protein synthesis?
transcription: formation of complementary strands of mRNA in the nucleus to be used as a template
translation: moving the mRNA across the nuclear membrane to the cytoplasm; then the mRNA strand threaded into the ribosome provided the RNA sequence for the codons with their corresponding aa’s to form a polypeptide chain
Proteins have no designated storage. They are repeatedly _____ and then _______. What is maintained by equal intake and excretion of amino acids? What happens when there is too much or too little of this substance?
they’re repeatedly synthesized and then degraded
Nitrogen balance is maintained by aa intake and excretion
Too little nitrogen: excessive tissue destruction, burns, starvation
Too much nitrogen: aa converted to urea for kidney excretion and into glucose or ketones for energy
Classification of proteins depend on what three things? What two classes (and subclasses) of proteins are there?
based on structure, composition, and function
- simple proteins: upon hydrolysis, yield only amino acids (eg albumin and troponin)
- conjugated/complex proteins: composed of a protein and a non-protein moiety
- enzymes, hormones, immunoglobulins
Routine analysis measurement of protein includes what three parts? What are three functions of plasma proteins?
measurement of total protein, albumin, and A/G (albumin/globulin) ratio
functions: catabolism, nitrogen balance, and hormone regulator
What is prealbumin, what is it a marker for in CSF, and what do increased and decreased concentrations indicate?
transport protein for thyroid hormones T3 and T4 (thyroxine and triiodothyronine).
Forms a complex with retinol-binding protein to transport vitamin A in CSF
Marker for nasal discharge
- decreased: hepatic damage, tissue necrosis, and poor nutrition
- increased: steroid therapy, alcohol abuse, and chronic renal failure
What is the roles of albumin?
maintains homeostatic pH by serving as a buffer in circulation and maintains the fluid balance between extra- and intra-vascular spaces (colloid osmotic pressure). It also binds bilirubin
negative acute phase protein
most abundant in plasma
what do increased and decreased concentrations of albumin indicate?
increased: not usually significant, but can mean dehydration
decreased: acute inflammatory response, liver/kidney disease, malabsorption/nutrition
What is the function of alpha-1-antitrypsin (A1AT), what kind of globulin is it, and what do increases and decreases of it signify?
positive acute phase reactant glycoprotein that functions to inhibit neutrophil elastase
-it’s a major protease inhibitor
it’s a alpha-1-globulin
increase: inflammation, pregnancy, contraceptive use
decrease: lung damage, emphysema
