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After studying this chapter, the reader should be able to:

  • 2.1 Explain the factors that constitute a high-quality protein.

  • 2.2 Briefly describe the process of protein digestion and absorption.

  • 2.3 Outline the process of protein metabolism.

  • 2.4 Describe several benefits and risks of a high-protein diet.

  • 2.5 List various types of protein and their effect on athletic performance.

  • 2.6 List several considerations when working with clients interested in adopting a high-protein diet.


  • amino acids The basic building blocks of proteins. Each amino acid has an amino- or nitrogen-containing group and a unique R chain that determines its ability to be used in various processes. Also known as peptides.

  • amino acid pool The amino acids available in the body to be used for protein synthesis.

  • anabolism The state in which the body builds and creates new tissues.

  • antibodies Proteins that fight infection.

  • bioavailability The degree to which a nutrient can be absorbed and used by the body.

  • branched chain amino acids (BCAA) Essential amino acids with a branched R chain. The three BCAAs, leucine, isoleucine, and valine, are metabolized in the muscle and are thought to be important in the formation of muscle mass.

  • catabolism The state in which the body breaks down tissues and amino acids for fuel.

  • complementary protein Combining two or more limiting proteins to form a complete protein.

  • complete protein A food item that contains all of the essential amino acids.

  • deamination The process of removing a nitrogen group from an amino acid.

  • denaturation The process of unfolding a protein by destroying its quaternary, tertiary, and secondary structure.

  • dipeptide Two amino acids connected by a peptide bond.

  • enzymes Proteins that speed up the rate of chemical reactions.

  • essential amino acid An amino acid that cannot be made by the body and must be consumed in the diet.

  • gastrin Hormone that prepares the stomach for food digestion; secreted by the stomach and stimulates pepsin release.

  • glucose-alanine cycle The cycle of transporting pyruvate and nitrogen from the muscle tissues to the liver as the amino acid alanine. In the liver, the alanine unloads the nitrogen group to become pyruvate, which is converted to glucose through gluconeogenesis. This process moves the work of gluconeogenesis from the muscle to the liver.

  • hypertrophy Abnormal increase in size; excessive growth.

  • incomplete protein A food item that does not contain all of the essential amino acids.

  • lacto-ovo vegetarian A vegetarian who consumes eggs and dairy products but does not consume meat, poultry, or fish.

  • lacto-vegetarian A vegetarian who consumes dairy products but does not consume eggs, meat, poultry, or fish.

  • micelle A compound similar to a soap sud that has a hydrophobic (water-averse) inside and a hydrophilic (water-loving) outside.

  • nitrogen balance The amount of nitrogen (via protein) consumed compared to the amount of nitrogen excreted. This provides information as to the person’s metabolic state, muscle synthesis, muscle degradation, or equilibrium.

  • nonessential amino acid An amino acid that can be made by the body.

  • pepsin...

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