Biochemistry: Nutrition and Protein Quality
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Questions and Answers

What is the primary purpose of nutrition?

  • To build muscle mass
  • To provide essential constituents that cannot be synthesized de novo (correct)
  • To provide energy only
  • To reduce body fat

    • What determines protein quality?

  • The proportion of essential amino acids in the food compared to requirements for good nutrition (correct)
  • The amount of protein in the food
  • The type of fatty acid in the protein
  • The amount of energy derived from the protein

    • What happens to protein requirements when energy intake from carbohydrates and fats increases?

  • Protein requirements increase
  • Protein requirements remain the same
  • Protein requirements are unaffected
  • Protein requirements decrease (correct)

    • What is the term for a deficiency of both energy and protein, resulting in generalized wasting?

    <p>Marasmus</p> Signup and view all the answers

    What is the term for a deficiency of protein quality, resulting in edema?

    <p>Kwashiorkor</p> Signup and view all the answers

    What is the main function of fiber in the digestive system?

    <p>To aid in water retention during passage of food along the gut</p> Signup and view all the answers

    What is a beneficial effect of a high-fiber diet?

    <p>Reduced risk of diverticulosis</p> Signup and view all the answers

    What happens to blood glucose levels when fiber is present in the digestive system?

    <p>They rise slowly</p> Signup and view all the answers

    What is one of the functions of lipids in the body?

    <p>to produce a feeling of satiety</p> Signup and view all the answers

    What is the function of vitamin A in the body?

    <p>to maintain epithelial cells of skin, eye, and mucous membrane</p> Signup and view all the answers

    What is the primary source of vitamin D?

    <p>skin exposure to UV rays</p> Signup and view all the answers

    What is the function of vitamin K in the body?

    <p>to synthesize prothrombin in the liver</p> Signup and view all the answers

    What is the deficiency symptom of vitamin E?

    <p>sterility in some animals, death of embryos</p> Signup and view all the answers

    What is the function of thiamin (B1) in the body?

    <p>to act as a coenzyme in carbohydrate metabolism</p> Signup and view all the answers

    What is the principal caution of sodium in the body?

    <p>Regulating plasma volume and acid-base balance</p> Signup and view all the answers

    What are the sources of vitamin A?

    <p>both plant and animal sources, including cod-liver oil</p> Signup and view all the answers

    What is a common effect of high fat consumption, especially of saturated fat?

    <p>increased risk of coronary heart disease</p> Signup and view all the answers

    Which of the following is a function of magnesium?

    <p>Constituting bones and teeth</p> Signup and view all the answers

    What is the unit of energy used to measure energy expenditure?

    <p>Kilo calorie</p> Signup and view all the answers

    Which of the following is a characteristic of basal metabolic rate?

    <p>It is proportional to mean body weight and surface area</p> Signup and view all the answers

    What is the function of chromium in the body?

    <p>Part of the 'glucose tolerance factor'</p> Signup and view all the answers

    What is the function of fluoride in the body?

    <p>Increasing hardness of bones and teeth</p> Signup and view all the answers

    What is the function of selenium in the body?

    <p>Constituent of glutathione peroxidase</p> Signup and view all the answers

    What is the function of copper in the body?

    <p>Constituent of oxidase enzymes</p> Signup and view all the answers

    What is the function of Riboflavin (B2) in the body?

    <p>Playing a role in oxidative process and intermediate metabolism of food</p> Signup and view all the answers

    What is the effect of Niacin (Nicotinic acid) deficiency?

    <p>Pellagra in humans</p> Signup and view all the answers

    What is the source of Pyridoxine (B6)?

    <p>Found in yeast, meat, eggs, nuts, and cereals</p> Signup and view all the answers

    What is the function of Folic Acid?

    <p>Essential for growth and formation of blood cells</p> Signup and view all the answers

    What is the effect of Pantothenic Acid deficiency?

    <p>No specific deficiency disease</p> Signup and view all the answers

    What is the source of Cyanocobalamin (B12)?

    <p>Found in milk, egg yolk, liver, and oysters</p> Signup and view all the answers

    What is the function of Vitamin C (Ascorbic Acid)?

    <p>Formation of intercellular material</p> Signup and view all the answers

    What is the category of Calcium and Phosphorus?

    <p>Macrominerals</p> Signup and view all the answers

    What is the thermogenic effect of food?

    <p>The extra heat associated with the consumption of food equivalent to about 5-10% of total energy expenditure</p> Signup and view all the answers

    What is the range of physical activity in terms of energy expenditure?

    <p>10-fold</p> Signup and view all the answers

    What happens to energy expenditure when environmental temperature is low?

    <p>It increases</p> Signup and view all the answers

    What is the primary function of glucose in the body?

    <p>To provide energy for the body's cells or to be stored as glycogen</p> Signup and view all the answers

    What is the byproduct of glucose oxidation when sufficient oxygen is present?

    <p>CO2 and H2O</p> Signup and view all the answers

    What is the purpose of the enzyme salivary a-amylase in the digestion of carbohydrates?

    <p>To catalyze the hydrolysis of a-glycosidic linkages in starch and glycogen</p> Signup and view all the answers

    What is the fate of glucose in the absence of oxygen?

    <p>It is partially oxidized to lactic acid</p> Signup and view all the answers

    What is the purpose of NADH and NADPH in carbohydrate metabolism?

    <p>To provide reductive power in cells</p> Signup and view all the answers

    Study Notes

    Nutrition

    • Nutrition is the provision of needed energy and essential constituents that cannot be synthesized de novo.
    • Sound nutrition depends on food intake that includes carbohydrates, proteins, fats, vitamins, minerals, and water.

    Protein Quality

    • Measured by comparing the proportions of essential amino acids in a food with production required for good nutrition.
    • Egg and milk proteins are high-quality proteins used as a reference standard against which other proteins can be compared.

    Energy Intake

    • Energy derived from carbohydrates and fats affects protein requirements because it spares the use of proteins as an energy source.

    Physical Activity

    • Increases nitrogen retention from dietary protein.

    Protein Energy Malnutrition

    Marasmus

    • Generalized wasting due to deficiency of both energy and protein.

    Kwashiorkor

    • Characterized by edema due to deficiency of both quantity and quality of protein although energy intake may be adequate.

    Carbohydrate Requirements

    • Glucose is needed by tissues, but does not have to be part of the diet, since other dietary carbohydrates are readily converted to glucose.

    Fiber Requirement

    • Denotes all plant cell wall components that cannot be digested by animal enzymes.
    • Beneficial effects of high fiber include:
      • Aiding in water retention during passage of food along the gut, producing softer feces.
      • Reducing incidence of diverticulosis, cancer of the colon, cardiovascular disease, and diabetes mellitus.
      • Slowing stomach emptying and delaying the rise in blood glucose.

    Lipid Requirements

    • Increases the palatability of food.
    • Produces a feeling of satiety.
    • Acts as a dietary vehicle for fat-soluble vitamins.
    • Supplies essential polyunsaturated fatty acids that the body cannot synthesize.
    • High fat consumption, especially of saturated fat, correlates with coronary heart disease.

    Vitamin Requirements

    • Organic nutrients required in small quantities for normal metabolism that cannot be synthesized by the body in adequate amounts.

    Fat-Soluble Vitamins

    Vitamin A (Retinol)

    • Provitamin is beta carotene from plants for maintenance of epithelial cells of skin, eye, and mucous membrane.
    • Regenerates visual purple of the eye.
    • Deficiency causes xerophthalmia, night blindness, and retardation of growth.
    • Sources: butter, eggs, milk, carotene of plants, cod-liver oil.

    Vitamin D (Calciferol)

    • Provitamins are ergasterol from plants and yeasts and 7-dehydrocholesterol from skin.
    • Regulates calcium phosphorus metabolism.
    • Deficiency causes rickets in young.
    • Sources: eggs, fish oil, beef fat, skin (exposure to UV rays).

    Vitamin E (Alpha-Tocopherol)

    • Necessary for nuclear growth and activity.
    • Deficiency causes sterility in some animals and death of embryos.
    • Sources: green leaves, spinach, soybean oil, egg yolk, liver.

    Vitamin K (Anti-Hemorrhagic Vitamin)

    • Synthesizes prothrombin in liver, essential for blood clotting.
    • Deficiency results in failure of blood to clot.
    • Sources: green leaves, spinach, soybean oil, egg yolk, liver.

    Water-Soluble Vitamins

    Vitamin B Complex

    Thiamin (B1) Antineuretic

    • Necessary for carbohydrate metabolism; acts as a coenzyme to carboxylase.
    • Deficiency causes beriberi, loss of appetite, and cessation of growth.
    • Sources: yeast, germ of cereals, egg yolk, nuts, lean protein.

    Riboflavin (B2)

    • Concerned with oxidative process and intermediate metabolism of food; hydrogen acceptor and donor for cellular synthesis.
    • Deficiency causes stunted growth, dermatitis, and cheilosis (inflammation of mouth corners).
    • Sources: green leaves, eggs, meat, cheese, milk, liver.

    Niacin (Nicotinic Acid) - Antipellargic

    • Essential to cellular functions, constituents of certain coenzymes.
    • Deficiency causes pellagra in man and degeneration of nerve cells.
    • Sources: green leaves, egg yolk, wheat germ, liver, yeast.

    Pyridoxine (B6)

    • Functions as coenzymes of some transmitting enzymes.
    • Deficiency results in failure to grow, together with anemia and dermatitis.
    • Sources: yeast, meat, eggs, nuts, cereals.

    Folic Acid

    • Essential for growth and formation of blood cells.
    • Deficiency causes anemia and sprue in man.
    • Sources: green leaves, soybeans, yeasts, egg yolks.

    Pantothenic Acid

    • Forms coenzyme A of Krebs cycle metabolism, necessary for nerve and skin.
    • Sources: eggs, milk, meat, sweet potatoes, cane, molasses.

    Biotin

    • Forms coenzyme necessary for carbon dioxide utilization.
    • Sources: egg yolk, meat, molasses, fresh fruits, and vegetables, yeast, cereal grain.

    Cyanocobalamin (B12)

    • Extrinsic factor of anti-anemic factor.
    • Deficiency causes pernicious anemia.
    • Sources: milk, egg yolk, liver, oysters.

    Vitamin C (Ascorbic Acid)

    • Formation of intercellular material.
    • Deficiency causes scurvy in man.
    • Sources: citrus fruits, tomatoes, cabbage, spinach.

    Mineral Requirements

    Macrominerals

    • Required in amounts greater than 100 mg/d.
    Calcium
    • Constituents of bones, teeth; regulates nerve and muscle function.
    Phosphorus
    • Constituents of bones, teeth, ATP, phosphorylated metabolic intermediates, nucleic acids.
    Sodium
    • Principal cation in extracellular fluid, regulates plasma volume, acid-base balance, nerve and muscle function.
    Potassium
    • Principal cation in intracellular fluid, regulates nerve and muscle function.
    Chloride
    • For fluid and electrolyte balance; constituent of gastric fluid.
    Magnesium
    • Constituent of bones, teeth; enzyme cofactor.

    Microminerals (Traced Elements)

    • Required in amounts less than 100 mg/d.
    Chromium
    • Trivalent chromium, a constituent of "glucose tolerance factor."
    Cobalt
    • Constituent of vitamin B12.
    Copper
    • Constituent of oxidase enzymes like cytochrome oxidase, ferroxidase.
    Iodine
    • Constituent of thyroxin, triodothyroxi.
    Iron
    • Constituent of hemoglobin, cytochromes.
    Manganese
    • Constituent of hydrolase, decarboxylase, and transferase enzymes; needed for glycoprotein and proteoglycan synthesis.
    Molybdenum
    • Constituent of oxidase enzyme, xantine oxidase.
    Selenium
    • Constituent of glutathione peroxidase.
    Zinc
    • Cofactor of many enzymes like lactate dehydrogenase, alkaline phosphatase, carbonic anhydrase, etc.
    Fluoride
    • Increases hardness of bones and teeth.

    Energy Requirement

    • Nutrients provide the energy needed by the body.
    • The energy unit is the kilocalorie, the amount of heat necessary to raise 1 kg of water from 15 to 16°C.

    Expenditure of Energy

    Basal Metabolic Rate
    • The energy expenditure necessary to maintain basic physiologic functions under standardized conditions.
    • Proportionate to mean body weight and surface area.
    • Higher in males than in females, in children, in people with fever and hyperthyroidism.
    Thermogenic Effect (Specific Dynamic of Action of Food)
    • The extra heat associated with the consumption of food equivalent to about 5-10% of total energy expenditure.
    Physical Activity
    • The range is over 10-fold between resting and maximum athletic activity.
    Environmental Temperature
    • Low environmental temperature causes increased energy expenditure, while at temperatures above body heat, extra energy is expended in cooling.

    Carbohydrates Metabolism

    • Glucose is the focal point of carbohydrate metabolism.
    • Commonly called blood sugar, glucose is supplied to the body via the circulatory system and, after being absorbed by a cell, can be either oxidized to yield energy or stored as glycogen for future use.

    Digestion and Absorption of Glucose

    • Digestion is the biochemical process by which food molecules, through hydrolysis, are broken down into simpler chemical units that can be used by cells for their metabolic needs.
    • The digestion of carbohydrates begins in the mouth, where the enzyme salivary a-amylase catalyzes the hydrolysis of a-glycosidic linkages in starch from plants and glycogen from meats to produce smaller polysaccharides and the disaccharide maltose.

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    Learn about nutrition, protein quality, and amino acid requirements. Understand the importance of essential amino acids in food for good nutrition.

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