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PROTEINS
Chapter 7
Building Blocks of Proteins?
Amine group Carboxylic Acid group R group
R O
NH2 C C OH
H
Examples of Amino Acids
Essential versus Non-essential
Limiting Amino Acid
CCCCC AAAAAAAA CAR CAR CAR RRRRRR CAR CAR R A A A
C is the limiting amino acid in this example
Limiting Amino Acids
Complementary Protein
Food 1 Food 2
CC CCCC AAAA AA CAR CAR
CAR RRR RRR CAR CAR
CAR
Dietary Aspects
PKU = Phenylketonuria
Vegetarian Diets
Protein Synthesis
Step 1: Transcription
Step 2: Processing
Step 3: Translation
Transcription
Formation of RNA from DNA template
A C T G A T
U G A C U A
DNA=
RNA=
CODON #1 CODON #2
Condensation Synthesis
Peptide bond
Dipeptide
Tripeptide
Oligopeptide
Polypeptide
Levels of Protein Structure
Sickle Cell Anemia
Denaturation of Protein
Turnover and Metabolism
Protein Digestion
Absorption of Amino Acids
Functions of Proteins Supplies nitrogen in a
useable form
Structural components
Blood clotting
Maintain fluid and acid/base balance
Immune function
Functions of Proteins
Hormones and enzymes Insulin and Thyroxine Pepsin, Trypsin
Visual processes
Formation of glucose (Gluconeogenesis)
Energy Source (4 kcal/energy)
RDA for Protein Promotes equilibrium 0.8 gm of protein / kg of healthy body
weight 154 lb. = 70 kg 2.2 kg/lb.
70 kg x 0.8 g protein = 56 g protein kg healthy body wt
Proteins in Foods
Proteins in Foods
Americans tend to eat more animal protein than plant protein (70%)
There are many benefits to eating more plant proteins:
Plant Protein
No cholesterol Low in saturated fat High in (soluble) dietary fiber
and phytochemicals
HOWEVER: Somewhat less efficient (than
animal protein) Lacking in one or more
essential amino acid
Protein-Energy Malnutrition
Types of PEM: Kwashiorkor Marasmus
Causes: Famine Anorexia Intestinal disorders
Kwashiorkor
Low protein density diet
Energy needs are marginally met
Subcutaneous fat is present
Poor growth, edema, weakness, apathy, diarrhea, listlessness
Marasmus
Starving to death “skin and bones”
appearance Insufficient protein,
energy, nutrients Little or no
subcutaneous fat Reduce brain
growth
Nutrition Perspective
Vegan - primarily eats only plant foods Fruitarian - primarily eats fruits,
honey, and vegetable oils Lactovegetarian - consumes plant
products and dairy products Lactoovovegetarian - consumes plant
products, dairy products, and eggs