Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Chapter 6 Proteins

Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED.

Chapter 6

Proteins


Objectives

• State functions of proteins in body

• Identify elements that make up proteins

• Describe effects of protein deficiency

• State energy yield of proteins

• Identify at least six food sources of complete proteins and at least six food sources of incomplete proteins


Functions

• Build and repair body tissue

• Regulate body functions– Metabolism and digestion

– Fluid and electrolyte balance

– Development of antibodies

• Provide energy– Each gram of protein provides 4 calories


Food Sources

• Animal food sources:– Complete proteins

– Meats, fish, poultry, eggs, milk, and cheese

• Plant food sources:– Incomplete proteins

– Corn, grain, nuts, sunflower seeds, sesame seeds, and legumes

(continues)


Food Sources

• Analogues:– Meat alternatives made from soy protein and other

ingredients to simulate various kinds of meat

– Tofu• Soft, cheese-like food made from soy milk

– Helpful for strict vegetarians to meet protein needs


Classification

• Depends on type and amino acids it contains

• Complete or high biologic value– High quality

– Contains all 10 essential amino acids

• Incomplete – Lacks one or more amino acids

– Cannot build tissue without help of other proteins

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Classification

• Complementary– Combination of incomplete proteins eaten in same day to

make complete protein

– E.g., corn and beans, rice and beans, bread and peanut butter, bread and split pea soup, bread and cheese, bread and baked beans, macaroni and cheese, cereal and milk


Composition

• Only nutrient that contains nitrogen

• Composed of amino acids

• Essential amino acids must be provided by diet

• Nonessential amino acids can be produced by body


Stop and Share

• Consider the following scenario:– Your client is concerned because her daughter is a

vegetarian and does not eat meat. Your client states: “My daughter does not eat meat, so I know she doesn’t get any protein. She is ruining her body.” How do you respond?

(continues)


Stop and Share

• Although animal foods are best sources of complete proteins, foods that provide incomplete proteins can be combined to make complete proteins

(continues)


Stop and Share

• Best sources of incomplete proteins:– Legumes, corn, grains, and nuts

• Soy protein and tofu– Nutritious meat replacements


Digestion and Absorption

• Mechanical digestion– Begins in mouth

– Teeth grind food into small pieces

• Chemical digestion– Begins in stomach

– Hydrochloric acid prepares stomach

– Pepsin reduces proteins to polypeptides

(continues)


Digestion and Absorption

• Chemical digestion– Polypeptides:

• 10 or more amino acids bonded together

– In small intestine, pancreatic enzymes continue chemical digestion

– Absorption occurs through villi

– Carried by blood to all body tissues


Metabolism and Elimination

• Amino acids broken down

• Deamination occurs

• Ammonia produced and released in bloodstream

• Liver picks up ammonia and converts it to urea

(continues)


Metabolism and Elimination

• Kidney filters out urea and excretes it

• Remaining parts used for energy or converted to carbohydrate or fat and stored as glycogen or adipose tissue


Dietary Requirements

• Determined by size, age, sex, and physical and emotional conditions

• National Research Council of National Academy of Sciences considers average daily requirement to be 0.8 g of protein for each kilogram of body weight


Stop and Share

• Consider the following scenario:– Your client weighs 170 pounds. What is her daily

requirement for protein?

(continues)


Stop and Share

• 170 pounds 2.2 pounds per kilogram = 77.27 kg

• 77.27 kg x 0.8 g of protein = 61.81 g

• 62 g of protein


Protein Excess

• Saturated fats and cholesterol found in complete proteins may contribute to heart disease

• Connection to colon cancer

• Often used as substitute for other healthful foods

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Protein Excess

• Increased demand on kidneys

• National Research Council recommends that protein intake represent no more than 15 to 20 percent of one’s daily caloric intake and not exceed double the amount given in RDA table


Stop and Share

• Consider the following scenario:– You are the nurse, and your client asks you whether taking

daily protein supplements will help build muscles, strengthen nails, and control weight. How do you respond?

(continues)


Stop and Share

• “Bulking up” athletes– Lifting weights builds muscle

• Not supplements

• Growing fingernails– Fingernails have never been affected by extra protein

• Sparing body protein in weight loss– Dieters need balanced diet using MyPyramid guidelines


Nitrogen Balance

• Nitrogen intake equals nitrogen excreted

• Positive nitrogen balance exists when nitrogen intake exceeds amount excreted

• Negative nitrogen balance exists when more nitrogen lost than taken in


Stop and Share

• Consider the following questions:– What conditions cause a positive nitrogen balance?

– What conditions cause a negative nitrogen balance?

(continues)


Stop and Share

• Positive nitrogen balance:– Pregnancy

– Growth periods

– Building of muscle

– Rebuilding of tissue after trauma or illness

(continues)


Stop and Share

• Negative nitrogen balance:– Fever

– Injury

– Surgery

– Burn

– Starvation

– Immobilization


Protein Deficiency

• Muscle wasting occurs

• Albumin (protein in blood plasma) deficiency causes edema

• Loss of appetite, strength, and weight

• Lethargy, depression, and slow wound healing


Protein Energy Malnutrition (PEM)

• Lack protein and energy-rich foods

• Found in developing countries with shortages of protein and energy-rich foods

• Causes stunted growth in children

• Impaired mental capacities may occur in infants born from mothers with protein deficiency


Marasmus

• Affects very young children

• Results from severe malnutrition– Lack of energy, protein, vitamins, and minerals

• Emaciated– No edema

• Dull, dry hair

• Thin, wrinkled skin


Kwashiorkor

• Affects children and adults

• Results from sudden or recent lack of protein-containing food

• Fat accumulates in liver

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Kwashiorkor

• Lack of protein and hormones results in edema, painful skin lesions, and changes in pigmentation of skin and hair

• High mortality rate


Stop and Share

• Consider the following question:– What are three differences between marasmus and

kwashiorkor?

(continues)


Stop and Share

Marasmus KwashiorkorWeight decreased Weight within normal limits

Visceral proteins within normal limits

Visceral proteins decreased

Immune function within normal limits

Immune function decreased

Dull, dry hair Reddish colored hair

Emaciated, wrinkled appearance

Edema with puffy appearance


Conclusion

• Proteins– Contain nitrogen

– Build and repair body tissues, regulate body processes, and supply energy

– Composed of amino acids

• Each gram of protein provides 4 calories

• Ten of the amino acids are essential for growth and development

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Copyright © 2011 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Chapter 6 Proteins