KNH 505 protein exam

central alpha carbon

the _______________ is bonded to an amino acid (-NH2), hydrogen (-H), carboxyl group (-COOH), and side chain (-R)

9

how many essential AAs are there?

essential AAs

-leucine

-isoleucine

-valine

-threonine

-methionine

-lysine

-histidine

-phenlyalanine

-tryptophan

disulfide

free -SH on side chain forms a ________ bond

conditionally essential AAs

non-essential AAs that become essential when the rate of synthesis does not equal metabolic demand

phenylalanine

conditionally essential AAs: tyrosine is derived from ___________

methionine

conditionally essential AAs: cysteine is derived from ____________

glutamic acid

conditionally essential AAs: proline is derived from ____________

arginine

conditionally essential AAs: ___________ is derived from glutamine, glutamic acid, and aspartic acid

glutamine

conditionally essential AAs: ____________ is derived from glutamic acid + ammonia

arginine and glutamine

conditionally essential AAs: ___________ and __________ become essential in cases of severe burn trauma, sepsis, and premature infancy

tertiary

in a __________ protein structure, R-group interactions give full 3D shape

hydrogen

in tertiary protein structures, __________ bonds are located between polar side chains

nonpolar

in tertiary protein structures, hydrophobic interactions occur, with __________ side chains clustering toward the center

electrostatic/ionic interactions

tertiary protein structures: opposite chargers attract, and like charges repulse

disulfide

in tertiary protein structures, _________ bonds are a covalent link between Cys side chains

sickle cell trait

protein structure error where Val replaces Glu in hemoglobin

albumin

transport protein: non-specific carrier: Ca, Zn, vit B6, and FFAs

lipoproteins

transport proteins: carries lipids (triglycerides and cholesterol)

disulfide

in cysteine, two cys are joined by disulfide bonds

complete proteins

high-quality protein; contain all 9 essential AAs; highly digestible; usually are animal or soy proteins

incomplete proteins

proteins that are low in or missing one or more essential AAs; less digestible; many plant proteins

complementary proteins

turn incomplete proteins into complete proteins

increase

protein requirements increase during stages of growth

less

older adults have lower muscle mass but absorb __________ protein

high

during pregnancy, there is a _______ demand for protein due to high growth rate of fetus

breast milk

during lactation, a portion of protein intake goes into ___________

catabolic

during ___________ states, there is a high demand of protein to repair/replace lost protein; this could be illness, injury, or metabolic stress

increased

during dieting, there is a decreased total calorie intake, and there should be an ____________ protein intake to spare muscle

increased

during exercise, in order to repair and build muscle, protein intake should be ___________ for a higher lean body mass

stomach

where does protein digestion start?

HCl

released in the stomach; stimulated by gastrin; denatures secondary, tertiary, and quaternary structures; activates pepsinogen and turns it into pepsin

pepsinogen

inactive form of pepsin

pepsin

active form of pepsinogen

secretin and CCK

protein digestion: when acid chyme enters duodenum, S-cells and I-cells release __________ and _________

pancreas and brush border

protein digestion: secretin and CCK travel in blood and target __________ and ___________

zymogens

protein digestion: when secretin and CCK reach pancreas, stimulate release of ___________, such as trypsinogen, chymotripsinogen, procarboxypeptidase A and B

enteropeptidase

protein digestion: when secretin and CCK reach brush border, stimulate release of ___________

enteropeptidase

-activates trypsinogen to trypsin; released at brush border

trypsin

once activated by enteropeptidase, ___________ then activates trypsinogen into more __________, chymotrypsinogen into chymotrypsin, and procarboxypeptidases A and B into carboxypeptidases A and B

trypsinogen

due to feedback controls, excess trypsin slows ___________ synthesis and release

small intestine

single AA transport primarily occurs in upper __________

active transport

single AA transport primarily uses ______________ as a carrier method

single AA

_________ transport is mostly Na+ and ATP-dependent

single AA transport

1. Na+ binds the carrier

2. AA binds the carrier

3. Na-AA cotransporter forms

4. Na+ and AA enter enterocyte

5. Na+/K+-ATPase pumps Na+ out

PEPT1

separate system from single AA; peptide transport

H+

PEPT1 is co-transported with _____, which is pumped back out for Na+; Na+/K+-ATPase keeps the gradient

dipeptides or tripeptides

more than 60% of AAs are absorbed as either __________ or __________; this is because it is faster

inside

most di/tripeptides are hydrolyzed into single AAs ________ the cell

glutamine

main fuel for GI mucosal cells

portal vein

AAs move into enterocytes, then into the __________, and finally into the liver

liver

the _________ works as a regulator for AAs by taking them up into carriers and matching metabolism

constantly

protein is __________ being degraded and rebuilt so that the body protein stays constant

100

the amino acid pool is small, at around ______g at a time in blood and cells

true

t or f: protein can be reused (protein economy)

dietary

in protein turnover, losses are replaced by __________ protein

transamination

first step of AA catabolism; amine group swap/is transferred; NH2 and C=O swap places; amine group moves from alpha-ketoglutarate to glutamate; AA becomes new alpha-keto acid

PLP/B6

aminotransferases (ALT and AST) require _____/_____

amine

in transamination, PLP carries the _______ group

oxidative deamination

removes the amine group as free NH3, mainly in liver and kidney

transamination and deamination

how are AAs disposed? (2 parts, N to glutamate, then N removed)

transamination

done via aminotransferases (AST and ALT; require PLP/vitamin B6)

oxidative deamination

done via glutamate dehydrogenase; requires NAD+ and NADP+

urea cycle

process where ammonia is converted to urea

amino acids

___________ are each degraded into NH3 + a carbon skeleton

carbon skeletons

____________ are used for energy and can enter the TCA cycle directly; also used for gluconeogenesis(glucogenic), can be converted to ketone bodies(ketogenic), go into lipid synthesis

cholesterol

leucine can be used to make ___________ via HMG-CoA

glutamate

__________ is deaminated by glutamate dehydrogenase (GDH)

oxaloacetate

AST transfers amino group from glutamate to ____________

urea

disposal form of amino-group nitrogen; makes up 80-90% of nitrogen-containing compounds in urine; made in liver, which has all urea cycle enzymes

arginase

kidney has all enzymes except ____________, so it has synthesis site for this enzyme

liver; kidneys

the ________ makes urea, and the ___________ filter and secrete it

arginase

enzyme that is only found in the liver that is used in the urea cycle

alanine and glutamine

nitrogen travels between organs mainly as ___________ and ____________

glutamine

in the intestine, dietary AAs are absorbed ___________ is used as an energy source

glutamine

intestinal absorption: _____________ is converted to glutamic acid using glutaminase; glu + pyruvate —> alpha-KG + Ala by ALT; proline and citruline are also formed; dietary AAs, Als, Pro, citruline go to portal blood then liver

liver

the ___________ synthesizes the liver and plasma proteins and catabolizes AAs through gluconeogenesis, urea synthesis, and ketogenesis

skeletal muscle

____________ is the main tissue uptake for BCAA

glutamic acid

most of the nitrogen from BCAA goes to ____________, which is picked up by alpha-ketoglutamate