PROTEIN-Part One NFSC 303 – Nutrition and Fitness McCafferty

FUNCTIONS §structure for tissues §transporters: § § § §fluid balance §acid/base balance

Basic Unit: Amino Acid §N essential from diet §Basic structure: C R group varies --

It takes 20 Amino Acids to make most proteins §Essential AAs l tryptophan l valine l threonine l isoleucine l leucine l lysine l phyenylalanine l methionine l histidine §Nonessential AAs l alanine l arginine l asparagine l aspartic acid l cysteine l glutamic acid l glutamine l glycine l proline l serine l tyrosine

A Few Terms: §Conditionally Essential AA: §Transamination:

§Deamination: l

Building Proteins from AAs § §

Polypeptide = several to hundreds of AAs linked together

Quaternary Structure: 2 or more polypeptides associated with each other, e.g. hemoglobin

Protein Digestion & Absorption §Mouth: l §Stomach: l Sight/smell/thought of food plus entry of food into the stomach stimulate ____________________.

HCl

§Small Intestine AAs (absorbed)

AAs are absorbed into the blood §AAs circulate through the liver l

§Any AAs that aren’t used to synthesize body proteins are “wasted.” l Deaminated: Remaining C skeletons are: l

Using Protein to Make ATP What is protein made of? What are the functions of protein? Do we store protein?

Remember §Each AA contains N, and must be deaminated before entering these pathways §Once the N is removed, 2-C and 3-C units remain, about half and half (simple story)

Amino Acids C Skeletons ( ) ( ) Glucose 6C Pyruvate 3C Acetyl CoA 2C Krebs ETS

§The 2C units enter at §The 3C units enter at l §

§We don’t store protein the same way we store CHO (glycogen) or fat (adipose) l Excess protein intake:

Summary of ATP Production from Protein §Under normal diet and exercise conditions, protein is not an important ENERGY source §Amino acids must be deaminated before they can be metabolized §Complete oxidation of AA’s produces urea, ATP, H 2 O and CO 2.

Summary of ATP Production from Protein §Because of their 3C skeleton, about half the carbons from AA’s (protein) can be used to synthesize glucose §Excess dietary protein is not stored as protein, but rather is used to produce ATP or is stored as fat (adipose)

GLUCONEOGENESIS The Making of New Glucose

Remember: §Exogenous fuels: from outside the body l dietary protein, CHO, and fat §Endogenous Fuels: from within the body l glucose from glycogen l fatty acids l fatty acids from adipose l amino acids from body proteins importance increases in times of inadequate kcalories or CHO intake

Remember... §Every cell uses glucose §Some cells are glucose dependent l §Gluconeogenesis is the making of new glucose form 3-carbon compounds l l l

§Gluconeogenic compounds: l pyruvate l lactate l glycerol l 3C AA’s, particularly alanine

Body Protein as a Source of Glucose § §To supply glucose to glu-dependent tissues, body proteins are catabolized §

Body Protein as a Source of Glucose glycerol (3C) §Remember, TG is catabolized too, but much more slowly, since only the glycerol (3C) can be used to synthesize glucose §So after the first 24 hours of a fast:

Ketone Bodies: An Alternative Fuel to Glucose? § § § §

§KBs are carried to other tissues for ATP production §

Liver Non-liver Tissues Adipose & Lean Body Tissues Acetyl CoA Ketone Bodies Acetyl CoA Krebs (ATP)