After studying this chapter you will be able to understand: Why is protein important? amino acids are the building blocks of proteins, functions of body proteins, protein digestion and absorption, proteins in the body, proteins in the diet.
Chapter Proteins and Amino Acids: Function Follows Form Why Is Protein Important? • • • • • Major component of all plant and animal issues Vital to many aspects of health Provide energy and help keep skin, hair, and nails healthy Deficiency leads to wasting Excess protein intake a greater problem in the U.S Amino Acids Are the Building Blocks of Proteins • Proteins are sequences of amino acids (AA) • 20 different amino acids – – essential amino acids • Body cannot make them • Must get them through diet 11 nonessential amino acids • Do not need to be supplied by diet • If body cannot make them, categorized Amino Acids as Building Blocks • • Amino acid structure – One central carbon atom – One hydrogen atom (H) – One carboxylic acid group (-COOH) – One amino group (-NH2) – One side group unique to each amino acid Side group gives the amino Protein Structure • Amino Acid Sequence – Each amino acid is joined to the next by a peptide bond – Peptide bonds • • • Dipeptide (2 AA) Oligopeptide (3 AA) Polypeptide (4-10 Protein Structure • Protein Shape – Sequence and properties of AA determines protein shape – Shape determines protein’s function Protein Denaturation • Denaturation – Disrupts shape – Protein unfolds and loses its shape (denature) – Caused by acidic or alkalinity, high temperature, alcohol, oxidation, and Functions of Body Proteins • Each protein has a specific function determined by its unique shape Protein in the Diet • Protein Quality – Evaluating Protein Quality and Digestibility • • Provides all the indispensable amino acids at amounts the body needs Provides enough other amino acids to serve as nitrogen sources for making dispensable amino acids • Should be easy to digest • Consider the protein digestibility- Protein in the Diet • Proteins and AAs as Additives and Supplements – Protein and AA additives • – Structure, texture, and taste of foods Protein and AA supplements • • Used for a variety of reasons: dieters, athletes, certain diseases Risks unknown Vegetarian Eating • Why People Become Vegetarians – Various reasons, including • Religious beliefs • Environmental concerns • • – Aversion to eating another living creature Concerns about animal cruelty concerns In some cases a necessity Vegetarian Eating • Health Benefits of Vegetarian Diets – Less fat, saturated fat, and cholesterol intake – More magnesium and folate – More antioxidants – More fiber and phytochemicals • Reduces risk for heart disease, obesity, hypertension, and cancer Vegetarian Eating • Health Risks of Vegetarian Diets – Vegan diets may be low in some nutrients • Calcium, iron, zinc, vitamin D, and vitamin B12 – Higher intake of phytates – More restrictive food choices = less nutrients – Careful planning needed for growth and overall health Vegetarian Eating • Dietary Recommendations for Vegetarians – Choose a variety of foods – Choose whole, unrefined foods – Choose a variety of fruits and vegetables – Choose lower-fat dairy products and eggs in moderation – Consume a regular source of vitamins B12 and D • Fortified foods or supplements Health Effects of Too Little or Too Much Protein • Protein-Energy Malnutrition – Kwashiorkor • Edema and other signs • Between ages of 18 and 24 months • Associated with extreme poverty Health Effects of Too Little or Too Much Protein • Protein-Energy Malnutrition – Marasmus • Chronic PEM • Infants and 6- to 18-month-old children • Adults with cancer or starvation Health Effects of Too Little or Too Much Protein • Health Effects of Excess Dietary Protein – Kidney function • – Increases kidney filtration rate, straining function Mineral losses • Link between high-protein diet and osteoporosis Health Effects of Too Little or Too Much Protein • Health Effects of Excess Dietary Protein – Obesity • – Heart disease • – Correlation with body fat Increased saturated fat and cholesterol intake Cancer • Increased risk for certain types of cancer ... proteins • Functions of Body Proteins • Immune functions – Antibodies • • Blood proteins that attack and inactivate bacteria and viruses Part of the body’s immune response Functions of Body Proteins. .. – Acidosis or alkalosis occurs when proteins unable to fulfill buffer function Functions of Body Proteins • Transport functions – Proteins act as • Channels and pumps, allowing substances to flow... Blocks of Proteins • Proteins are sequences of amino acids (AA) • 20 different amino acids – – essential amino acids • Body cannot make them • Must get them through diet 11 nonessential amino acids