Nutrition and Energy Production

Nutrition and Energy Production

Learning Objectives

  • Explain why an animal’s diet should be balanced and meet the needs of the body.

  • Define the primary components of food.

  • Describe the essential nutrients required for cellular function that cannot be synthesized by the animal body.

  • Explain how energy is produced through diet and digestion.

  • Describe how excess carbohydrates and energy are stored in the body.

Overview of Animal Diet

  • The diversity of animal life results in substantial variation in animal diets.

  • Diet serves as the source of materials for:

    • Building DNA and complex molecules required for:

    • Growth

    • Maintenance

    • Reproduction (biosynthesis)

    • Producing ATP in cells.

    • The diet must be balanced to provide essential minerals and vitamins needed for cellular function.

Food Requirements

  • Fundamental Requirements of the Animal Diet:

    • A balanced diet must provide:

    • Nutrients required for bodily function

    • Minerals and vitamins necessary for maintaining health and reproductive capability.

  • The balance of nutrients can be graphically represented (See Figure 34.14).

  • Awareness of food groups and their nutrients is the first step in meeting dietary requirements.

Every Day Connection

  • Obesity Epidemic:

    • The rate of obesity, especially in children, is rising rapidly in the United States.

    • The Let’s Move! Campaign, launched by first lady Michelle Obama, aims to combat childhood obesity by:

    • Educating parents and caregivers on healthy nutrition.

    • Encouraging active lifestyles in children and ensuring access to healthy foods.

    • Promoting physical activity to combat sedentary lifestyles.

Organic Precursors in Diet

  • Organic Molecules:

    • Required for building cellular materials and tissues must come from food.

  • Carbohydrates:

    • Serve as the primary source of organic carbon in the animal body.

    • Digestible carbohydrates are broken down into glucose for energy.

    • Complex carbohydrates can also be converted to glucose (e.g., polysaccharides).

  • Cellulose:

    • Humans cannot derive glucose from cellulose due to lack of the enzyme cellulase; instead, it provides necessary fiber for digestion.

  • Storage of Excess Sugars:

    • Excess sugars are converted into glycogen and stored in the liver and muscles for energy.

    • Glycogen stores help during prolonged exertion and food shortages.

    • Excess glycogen can be converted into fats stored under the skin for insulation and energy.

Nitrogen Requirement

  • Proteins as Nitrogen Source:

    • Protein catabolism provides organic nitrogen.

    • Amino acids serve as building blocks for proteins and nucleic acids.

  • Excretion of Excess Nitrogen:

    • Excess nitrogen is toxic and must be excreted.

Fats and Their Role in Diet

  • Flavors and Satiety:

    • Fats add flavor and promote feelings of fullness.

  • Energy Content:

    • Fats provide a significant energy source, yielding nine calories per gram.

    • Necessary for absorbing fat-soluble vitamins and for the production of hormones.

Essential Nutrients

  • Definition:

    • Essential nutrients are those that must be consumed through food as the body cannot synthesize them.

  • Essential Fatty Acids:

    • Omega-3 (alpha-linolenic acid) and Omega-6 (linoleic acid) are vital for membrane phospholipid formation.

  • Vitamins:

    • Required in small amounts for enzyme function; act as coenzymes.

    • Two classes:

    • Fat-soluble: Vitamins A, D, E, and K.

    • Water-soluble: Includes Vitamin C and B-complex vitamins.

  • Minerals:

    • Inorganic essential nutrients crucial for various bodily functions.

  • Essential Amino Acids:

    • Humans cannot synthesize all amino acids; thus, some must come from dietary sources.

    • A total of 20 amino acids exist, and 9 are essential in the diet (Table 34.4).

Essential Vitamins Table (Water-soluble)

  • Vitamin B (Thiamine):

    • Function: Process lipids, proteins, and carbohydrates.

    • Deficiency: Muscle weakness, Beriberi.

    • Sources: Milk, meat, dried beans, whole grains.

  • Vitamin B (Riboflavin):

    • Function: Active in metabolism, energy conversion.

    • Deficiency: Cracks/sore lips; inflammation.

    • Sources: Meat, eggs, enriched grains, vegetables.

  • Vitamin B (Niacin):

    • Function: Energy release from carbohydrates.

    • Deficiency: Pellagra (dermatitis, diarrhea, dementia).

    • Sources: Meat, eggs, grains, nuts.

  • Vitamin B (Pantothenic acid):

    • Function: Energy production.

    • Deficiency: Fatigue.

    • Sources: Meat, whole grains, milk.

  • Vitamin B (Pyridoxine):

    • Function: Processes amino acids and lipids, nutrient conversion to energy.

    • Deficiency: Irritability, confusion.

    • Sources: Meat, dairy, whole grains.

  • Vitamin B (Biotin):

    • Function: Involved in metabolism and blood sugar utilization.

    • Deficiency: Hair loss.

    • Sources: Meat, eggs, legumes.

  • Vitamin B (Folic acid):

    • Function: Normal development of cells; nucleic acid metabolism.

    • Deficiency: Birth defects in pregnancy.

    • Sources: Leafy greens, whole wheat, fruits.

  • Vitamin B (Cobalamin):

    • Function: Nerve health; blood cell formation.

    • Deficiency: Anemia.

    • Sources: Meat, eggs.

  • Vitamin C (Ascorbic acid):

    • Function: Connective tissue maintenance.

    • Deficiency: Scurvy.

    • Sources: Citrus fruits, broccoli.

Essential Vitamins Table (Fat-soluble)

  • Vitamin A (Retinol):

    • Function: Development of bones and teeth; vision maintenance.

    • Deficiency: Night blindness.

    • Sources: Green leafy vegetables, milk.

  • Vitamin D:

    • Function: Calcium absorption.

    • Deficiency: Rickets.

    • Sources: Cod liver oil, milk.

  • Vitamin E (Tocopherol):

    • Function: Reduces oxidative damage.

    • Deficiency: Rare, but may cause anemia.

    • Sources: Wheat germ oil.

  • Vitamin K (Phylloquinone):

    • Function: Essential for blood clotting.

    • Deficiency: Bleeding disorders.

    • Sources: Green leafy vegetables.

Minerals and Their Functions

  • Calcium:

    • Function: Muscle and neuron function; bone health.

    • Deficiency: Osteoporosis.

    • Sources: Milk, yogurt.

  • Chlorine:

    • Function: Production of hydrochloric acid in the stomach.

    • Deficiency: Muscle cramps.

    • Sources: Table salt.

  • Copper (trace):

    • Function: Required for enzymes.

    • Deficiency: Rare.

    • Sources: Liver.

  • Iodine:

    • Function: Synthesis of thyroid hormones.

    • Deficiency: Goiter.

    • Sources: Seafood, iodized salt.

  • Iron:

    • Function: Essential for hemoglobin.

    • Deficiency: Anemia.

    • Sources: Red meat, leafy greens.

  • Magnesium:

    • Function: ATP formation cofactor.

    • Deficiency: Mood disturbances.

    • Sources: Whole grains.

  • Sodium:

    • Function: Electrolyte necessary for functions.

    • Deficiency: Muscle cramps.

    • Sources: Table salt.

Food Energy and ATP Production

  • Animals require food to obtain energy and maintain homeostasis.

  • Homeostasis Definition:

    • The ability of a system to maintain stable internal conditions despite external changes.

    • Example: Normal body temperature for humans is maintained at 37°C (98.6°F).

  • Primary Energy Source:

  • Carbohydrates, chiefly glucose, known as the body’s fuel.

  • During digestion, carbohydrates are converted to glucose via catabolic reactions.

  • Adenosine Triphosphate (ATP):

    • The main energy currency in cells.

    • Stores energy in phosphate ester bonds.

    • Breaks down to release energy converting to ADP and phosphate.

  • Cellular Respiration:

    • ATP is produced in the cytoplasm and mitochondrion through metabolic reactions.

  • Glycolysis Process:

    • Conversion of glucose into pyruvic acid and transfer of energy into NADH and ATP.

  • ATP is essential for various cellular functions including:

    • Building organic molecules.

    • Muscle contraction.

    • Electrical signal transmission in the nervous system.

Energy Storage and Conversion

  • When excess ATP and glucose are present:

    • The liver transforms these into glycogen, which is stored in the liver and muscles.

    • Glycogen:

    • A polymer form of glucose utilized when blood sugar falls.

    • In skeletal muscles, glycogen converts to glucose during physical activity.

  • This storage strategy is vital for dealing with mobility, food shortages, and famine.

Everyday Connection: Obesity

  • Health Issue:

    • Obesity significantly impacts health, linked to type-2 diabetes, cancers, and cardiovascular diseases.

  • Caloric Density of Foods:

    • Fatty foods provide higher energy per gram (9 calories) compared to carbohydrates and proteins (4 calories each), leading to preference and potential obesity.

  • Hunger and Satiety Signals:

    • Controlled by the hypothalamus where fatty foods enhance satiety more effectively than carb-rich foods.

  • Fat Storage in the Body:

    • Excess carbohydrates and ATP lead to the synthesis of fatty acids from pyruvate through metabolic processes.

    • Stored in adipose cells, which play a critical role during shortages, providing energy and insulation for mammals, especially in harsh climates.

    • Stored body fat acts as a reserve in times of food scarcity, whereby significant energy is accessed when needed.