Download NS 315 Unit 6: Proteins

NS 315
Unit 6: Proteins
Jeanette Andrade MS,RD,LDN,CDE
Kaplan University
Objectives
 Definitions
 Essential Amino Acids
 Protein Structure and Organization
 Protein Digestion, Absorption and Metabolism
 Urea Cycle
 Alanine Cycle
 Recommended Daily Intakes
 Case Study
Defintions
 Amino Acids: molecule containing both amine and
carboxyl functional groups
Side chain
Amino group
Carboxylic acid group
R
O
H2N
C
C
OH
H
 Protein: Large organic compounds made of amino
acids arranged in a linear chain and joined together
by peptide bonds between the carboxyl and amino
groups of adjacent amino acid groups
Definitions
 Protein Quality: Particular protein providing a
balanced pattern of indispensable amino acids
 Denaturation: Precipitation of proteins with heat
causing them to turn “inside out”
 Amino-transferases: enzymes transferring amino
groups usually between amino group to 2-keto acid,
e.g. l-alanine and 2-ketoglutarate
Essential Amino Acids
9 essential amino acids we need to
consume due to cannot be synthesized
Acronym: PVT TIM HLL
 phenylalanine, valine, threonine, tryptophan,
isoleucine, methionine, histidine, leucine, and
lysine
http://en.wikipedia.org/wiki/Essential_amino_acids
Protein Structure and Organization
Protein Structure:
H
H
CH3
O
+
H3N
C
O
C
H
+
N
C
C
-
O-
O
H
H
H
Glycine
Alanine
H2O
H
O
H
CH3
O
+
H3N
C
C
N
C
C
O-
H
H
Peptide bond in Glycyl-Alanine
http://www.gbiosciences.com/EducationalProducts/Protein-StructureAnalysis.aspx
Protein Digestion and Absorption
Where does Protein Digestion begin?
What aids in breaking down the protein
structure?
How are proteins absorbed into the
intestinal cells?
Urea Cycle: Protein Catabolism

Urea is the end product of the nitrogen metabolism

Ammonia must be removed from the body and usually is converted to
urea to be excreted

Ammonia is usually the from of energy produced during starvation
mode and urea is the form of energy produced during fed states

This reaction occurs in the liver and then urea is transported to the
kidney

Urea is generally measured in the body as BUN (Blood Urea Nitrogen)

If BUN elevated: maybe due to renal failure, dehydration, CHF
(congestive heart failure)

Uric acid salts deposited within the joints can lead to a condition
referred to as gout
http://guweb2.gonzaga.edu/faculty/cronk/biochem/images/urea-cycle-eqn.gif
Alanine Cycle






Alanine is usually produced during times of exercise
when oxygen depleted (anaerobic).
Shuttled to liver to produce glucose
Energy by-product: urea
Recycles carbon skeletons between muscle and liver
Transports Ammonia (NH4+) to liver to be converted to
urea
During liver diseases (non-alcoholic fatty liver disease,
cirrhosis) cannot convert NH4+ to urea
http://en.wikipedia.org/wiki/Alanine_cycle
Alanine Cycle
http://www.wiley.com/college/fob/quiz/quiz2
1/21-6.html
http://en.wikipedia.org/wiki/Alanine_cycle
Recommended Daily Intake
Nitrogen Balance: Difference between the
amount of nitrogen consumed per day by
the amount of nitrogen excreted per day
 Nitrogen Balance= (grams of nitrogen eaten - grams
of nitrogen lost)
 Positive nitrogen balance indicates growth- What
age groups are in the positive nitrogen balance?
Protein- Case Study
 R.C. is a 30 year old male who is interested in losing weight
and has heard the quickest way to do it is by a low
carbohydrate, high protein diet. He realizes he also has to
exercise, but since he cannot do cardio because he is always
short of breath, he is going to lift weights. He informs you he
has started incorporating more protein already into his diet
and has lost 20 lbs within 2 months. When you review his
diet, he is consuming 300 gm of protein per day.
 Height: 5’11” Weight: 330 lbs previous weight: 350 lbs (2 months ago)
 What do you foresee to be a problem with the amount of
protein consumed?
 What can you suggest to this client to reduce the amount of
protein consumed?