Chapter 6 Proteins and Amino Acids

Chapter 6 Proteins and Amino Acids
Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Sources of Protein in the Diet
Protein deficiency is rare in the U.S. About two-thirds of dietary protein comes from meat, poultry, seafood, eggs and dairy products Most of the world relies on plant proteins from grains and vegetables As a country’s economy improves, the proportion of animal foods in the diet tends to increase Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 2

Sources of Protein in the Diet

How Protein Source Impacts the Diet
Animal products provide sources of protein, B vitamins and minerals such as iron, zinc and calcium However, animal products are low in fiber and can be high in fat Plant sources of protein are also a good source of B vitamins, iron, zinc, fiber, phytochemicals and calcium, but in less absorbable forms Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 4

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.
Amino Acids Are the building blocks of protein Each contains a central carbon atom bound to a hydrogen atom, an amino group, an acid group and a side chain Essential amino acids cannot be synthesized by the human body in sufficient amounts to meet needs Must be included in the diet Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 5

Amino Acids: Transamination
When a nonessential amino acid is not available from the diet, it can be made in the body by the process of transamination Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 7

Protein Structure Amino acids are linked by peptide bonds These bonds are formed between the acid group of one amino acid and the nitrogen group of the next amino acid Dipeptide bonds are formed between two amino acids Polypeptides are formed between many amino acids A protein is made of one or more polypeptide chains folded into a three-dimensional shape Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 8

Protein Shape Determines Function
Connective tissue proteins and collagen are elongated Hemoglobin is spherical If the shape of a protein is altered, its function may be disrupted Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 10

Protein Digestion and Absorption
Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 13

Protein Digestion and Food Allergies
Food allergies are triggered when a protein from the diet is absorbed without being completely digested Proteins from milk, eggs, nuts, wheat, soy, fish, shellfish and peanuts are common causes of food allergies A rapid, severe allergic reaction is called anaphylaxis People with GI disease are prone to allergies because their damaged intestines allow for the absorption of whole proteins Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 14

Protein Synthesis: Transcription and Translation

The Limiting Amino Acid

Amino Acids as an Energy Source

Protein Functions Provide structure Enzymes speed up metabolic reactions Transport proteins move substances in and out of cells Antibodies help the immune system in fighting off foreign bodies Contractile proteins help the muscles to move Hormones are chemical messengers, such as insulin and glucagon Proteins help to regulate fluid and acid-base balance Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 20

Proteins Provide Structure and Regulation

Protein Deficiency Protein-energy malnutrition (PEM) is a term that covers a range of protein deficiency conditions that may include only protein deficiency or protein deficiency plus energy deficiency Kwashiorkor is a pure protein deficiency Marasmus is an energy and protein deficiency Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 22

Protein-Energy Malnutrition

Protein Excess Elevated protein intakes over long periods of time can result in Hydration and kidney function issues Bone health issues Kidney stones Increased risk of heart disease and cancer Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 24

Proteins that May Harm Certain Individuals: Phenylalanine
Phenylketonuria (PKU) is an inherited condition attributed to a defective gene Aspartame, a sugar substitute, contains phenylalanine Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 25

Proteins that May Harm Certain Individuals: Glutamic Acid
Monosodium glutamate (MSG) consists of the amino acid glutamic acid (or glutamate) bound to sodium Anecdotal reactions include flushed face, tingling or burning sensations, headache, rapid heartbeat, chest pain, and general weakness MSG symptom complex is commonly termed Chinese restaurant syndrome Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Protein Requirements Adults require 0.8g/kg body weight per day Acceptable Macronutrient Distribution Range (AMDR) is 10–35% of energy for adults Protein needs increase during periods of growth, pregnancy and lactation Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 28

Maintaining Muscle Mass in Older Adults

Do We Need Protein and Amino Acid Supplements?

Considering Protein Quality

Protein Complementation

Choosing Protein Wisely

Types of Vegetarian Diets

Meeting Protein Needs with a Vegan Diet

37

Chapter 6 Copyright 2016 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information herein. . Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 38

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