JC HBHD 2 Week 4 Chapter19

Nutrition & Metabolism

• This chapter covers nutrition and metabolism
• Learning objectives include: the liver's role in metabolism, metabolic functions of carbohydrates, fats, proteins, vitamins and minerals, mechanisms regulating food intake and basal metabolic rate, conditions associated with eating or metabolism and mechanisms regulating body temperature.

Definitions

• Nutrition: Food, vitamins, and minerals ingested and assimilated into the body
• Metabolism: Process of using nutrient molecules as energy and building blocks for body molecules.
• Catabolism: Breaks down food molecules, releasing stored energy. Oxygen is involved
• Anabolism: Builds nutrient molecules into complex chemical compounds

Food Guide

• ChooseMyPlate.gov is a US Department of Agriculture guide

Metabolic Function of the Liver

• Secretes bile for lipid digestion
• Processes blood after leaving the gastrointestinal tract, helping maintain blood glucose levels
• Is the site of protein, carbohydrate and fat metabolism
• Removes toxins from the blood
• Synthesizes proteins, including albumins, fibrinogens, and clotting factors
• Stores vitamins

Macronutrients

• Carbohydrates, lipids, and proteins are the "big three" macronutrients in the diet
• Vitamins and minerals are micronutrients

Carbohydrate Metabolism

• Carbohydrates are the body's preferred energy source
• Glucose Metabolism involves a series of chemical reactions in a precise order:
  • Glycolysis: Occurs in the cytoplasm, is anaerobic (does not use oxygen), converts glucose to pyruvic acid then to acetyl CoA and produces a small amount of energy (transferred to ATP).
  • Energy from ATP diffuses from nutrient molecules and is almost instantly used for cellular function.
  • Glycogenesis, a series of chemical reactions, converts glucose to glycogen. This mainly happens in liver cells where glycogen is stored.

Metabolism of Glucose

• Shows the process of glucose storage and metabolism through pathways.

Citric Acid (Krebs) Cycle

• Occurs in the mitochondria
• Is an aerobic process (requires oxygen)
• Converts acetyl CoA to carbon dioxide
• Yields a small amount of energy
• Most of the energy released in the form of high-energy electrons

Adenosine Triphosphate (ATP)

• ATP is a high-energy molecule composed of adenosine and three phosphate groups.
• Release of energy from ATP converts it to ADP and phosphate.
• Energy from nutrient catabolism is stored as ATP and then released to drive cellular processes.

Blood Glucose

• Normal blood glucose levels stay between 80-110mg per 100 mL of blood when fasting
• Insulin moves glucose from blood to cells, lowering blood glucose and increasing glucose catabolism

Fat and Protein Metabolism

• Fats are a primary energy nutrient, converted into glucose by catabolism
• Excess fat is converted to adipose tissue.
• Proteins are catabolized for energy only when carbohydrate and fat stores are exhausted.
• Gluconeogenesis breaks down amino acids to convert them to glucose.

Catabolism of Nutrients

• Summary diagram showing the catabolism process of nutrients (carbohydrates, fats, and proteins), breaking down into smaller units, entering the citric acid cycle, yielding energy and releasing carbon dioxide

Vitamins

• Vitamins are organic molecules needed in small amounts for normal metabolism
• Avitaminosis: Deficiency of a vitamin, can lead to severe problems, examples include scurvy, associated with vitamin C deficiency
• Hypervitaminosis: Excess of a vitamin, can be just as serious as avitaminosis
• Vitamins attach to enzymes or coenzymes to help make them active, without the appropriate vitamin, the enzymes won't work
• Vitamin A plays a role in light detection in sensory cells of the retina.
• Vitamin D converts to a hormone that regulates calcium balance in the body
• Vitamin E is an antioxidant that prevents damage to DNA

Minerals

• Minerals are inorganic molecules found in the earth.
• Required for normal body functions, including nerve conduction
• They can attach to enzymes to facilitate their work.

Regulating Food Intake

• Appetite center stimulates hunger
• Satiety center triggers the feeling of fullness or satisfaction

Metabolic Rates

• Basil metabolic rate (BMR): Metabolism rate when resting and not digesting food in a comfortably warm environment
• Total metabolic rate (TMR): The total amount of energy used by the body per day

Basal and Total Metabolic Rates

• Factors that affect basal and total metabolic rates include:
  • size (surface area)
  • sex
  • body composition (lean/fat ratio)
  • age
  • amount of thyroid hormone
  • miscellaneous factors (fever, drugs, emotions)
  • exercise and activity
  • food intake amount and thermic effect of food

Metabolic Conditions

• Disruptions or imbalances of normal metabolism can arise due to different factors including:
  • Inborn errors of metabolism: Genetic conditions with deficient or abnormal enzymes.
  • Complications from other conditions and hormonal imbalances.

Eating Conditions

• Anorexia nervosa: Chronic refusal to eat
• Bulimia: Alternating between craving and self-denial/self-induced vomiting
• Obesity: Abnormally high fat proportion in the body

Protein-Calorie Malnutrition (PCM)

• Results from a general deficiency of calories/proteins -Marasmus: Advanced PCM, overall lack of calories and protein
  • Kwashiorkor: Advanced PCM, lack of protein -Distinguishing features: Tissue wasting, fluid/electrolyte imbalances, ascites, flaking dermatitis for each type

Body Temperature

• Hypothalamus regulates body temperature (thermoregulation) through various processes -Blood flow to skin increase when body is overheated, to lose heat by radiation, conduction, convection, and evaporation.

• Abnormal body temperature consequences which include: -Fever (febrile state): Unusually high body temperature, associated with inflammation (systemic response) -Malignant hyperthermia (MH): Inherited condition that elevates body temperature and causes muscle rigidity

• Heat exhaustion & Heatstroke: Results from fluid loss and body overheating due to the failure of thermoregulatory mechanisms, in warm environments

• Hypothermia and frostbite: Reduced body temperature due to the failure of thermoregulatory mechanisms in very cold environments causing local tissue damage and potentially necrosis or gangrene.