Exam 6

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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


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