Exam 6
define quaternary structure
+2 globular forms * shape held by noncovalent bonds
In what scenarios does AA exit the bloodstream? (5)
1- Amino Acid degradation (in liver) 2- To enzymes/hormones 3- Muscle/other tissue protein synthesis 4- wool, hair, hooves 5- fetus
What are the two entry points for amino groups into the urea cycle?
1- Carbamyl phosphate 2- Aspartic acid
What paths are possible in amino acid degradation? (3)
1- N used in heme, creatine 2- N exits as urea (urine) 3- Energy
what are the 2 reasons for protein/AA catabolism?
1- Provide E from carbon skeleton (make fat/glucose) 2- Remaining N used in protein synthesis
name the 2 coenzyme forms of Vitamin B 6 (pyridoxine) and groups included in their structure
1- Pyridoxal phosphate (aldehyde and phosphate) 2- Pyridoxamine phosphate (amino + phosphate)
In what scenarios does AA enter the blood stream? (3)
1- Tissue protein degradation 2- Nonessential Amino Acid Synthesis (in cells) 3- Dietary/Microbial Protein degradation
What are the analogs of 1- Pyruvate 2- OA 3- alpha- ketoglutarate
1- alanine 2- aspartic acid 3- glutamic acid
what can denature proteins (3)
1- heat 2- acid 3- some chemicals
What two steps are needed to convert MHA--> methionine
1- oxidation 2- transamination
what is the glandular stomach in: 1- monogastrics 2- ruminants 3- chicken
1- the stomach 2- abomasum 3- proventriculus
what are the two steps to amino acid synthesis
1- transamination 2- reductive amination
define dipeptides
2 AA linked by Peptide bonds
define oligopeptides
2-20 AA linked by peptide bonds
How many AA are found in nature? About how many are essential?
21 AA about half are essential nutrients
define tripeptides
3 AA linked by peptide bonds
What vitamin is used in transamination?
Vitamin B6
define primary structure
a line of AA with branches *w/ covalent bonds
What reaction allows you to acquire glutamate
alpha=ketoglutarate --> glutamate (reductive amination)
Define transamination
amine group transferred to new compound
Oxidative Deamination pathway summary
amino group --> free ammonia
define amino terminus
amino group not used in the peptide bond
Summary of transamination
Amino --> alpha keto acid
Pathway summary of the urea cycle (including prep step)
Ammonia (NH4) --> Urea
Pathway summary for the synthesis of carbamyl phosphate
CO2 + free ammonia + 2 ATP --> carbamyl phosphate
Why are racemic mixtures less efficient?
D configurations are not absorbed as efficiently
what orientation are naturally occurring AA
L configuration
What is the difference between MHA and methionine?
MHA has a hydroxy group instead of amine
what is the intermediate in Methionine synthesis
MKA
Pathway summary of amino acid synthesis
NH3 --> AA
What reaction allows you to acquire aspartate
OA + glutamate --> aspartate + alpha-ketoglutarate (transamination)
What is the prep step to the urea cycle?
Synthesis of carbamyl phosphate
What two criteria change the types of AA required by an animal?
animal species and age
what is the purpose of luminal digestion?
break peptides into smaller groups in order to facilitate absorption (mucosal digestion)
define carboxyl terminus
carboxyl group not used in peptide bond
define protease
catalyze proteolysis
where is most AA found (Amino Acid Pool)?
cells, blood, extracellular fluid
Why is methionine special?
contains sulfur and is the most limited AA in the body (regulate AA catabolism)
How do mammals remove excess ammonia?
create urea and excrete through urine (after traveling blood --> kidney)
define denaturation
destruction of secondary, tertiary, and quaternary structures losing their function
What is the purpose of MHA
dietary supplement used in monogastric, poultry, and swine
How do fish remove excess ammonia?
eliminate ammonia directly
what activates trypsinogen --> trypsin
enterokinase
how do reptiles/birds remove excess ammonia?
form uric acid
define tertiary structures
globular form of AA (folded ribbon) * shape held by noncovalent bonds
define polypeptides
greater than 50 AA linked by peptide bonds
define secondary structures
helical form of amino acids (twisted ribbon) * shape held by noncovalent bonds
define proteolysis
hydrolysis of peptide bonds using the enzyme pepsin
Where is AA stored?
in body tissues
where does the urea cycle occur? Does it require ATP?
in the liver (partially in cytosol and in the mitochondria) yes, require ATP
define zymogen
inactive form of enzyme
define pepsinogen How is it activated?
inactive form of pepsin activated by HCL
define peptides
less than 2-50 AA linked by peptide bonds
where does AA metabolism take place
liver
what is the purpose of mucus in the stomach
lubrication
what system is used for travel?
lymph system (immunoglobulins)
define protein
many AA linked by peptide bonds arranged in higher types of structures
What are the two most limiting amino acids?
methionine and lysine
What does MHA stand for
methionine hydroxy analog
what are essential AA essential for? (2)
nutrient requirements and building blocks for endogenous sources
Define essential nutrient
nutrient that must be obtained/provide from an exogeneous source
What is used to initiate the digestion of protein?
pepsin
what enzyme is used for degradation in the stomach?
pepsin
what is the only protein structure (1,2,3,4) made with covalent bonds
primary (1)
what reaction allows you to acquire alanine
pyruvate + glutamate --> alanine + alpha-ketoglutarate (transamination)
Where does protein digestion begin?
stomach
Define glandular stomach
stomach producing excretions (HCl, pepsinogen, mucus)
what is the problem with synthetically produced amino acids?
synthetically produced are racemic mixtures (L and D configurations)
T/F small peptides can be absorbed into enterocytes
true
what is the key enzyme for protein breakdown in the small intestine?
trypsin
what is the inactive form of trypsin
trypsinogen
Define analog
two structures highly similar to one another. generally reversible
why is pepsin kept inactive?
would degrade stomach wall if protein is not present
