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