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 ProteinFood 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