Metabolism and Energy Balance Quiz

Metabolism and Energy Balance

• Metabolism encompasses all biochemical reactions in the body
• Catabolism breaks down molecules, releasing energy (ATP)
• Anabolism builds up molecules, using energy (ATP)
• Hormones regulate these processes
• Food intake provides energy, used for work and body functions
• Excess energy can be stored as fat

Objectives

• Define metabolism
• Understand energy balance
• Explain feeding regulation
• Define metabolic rate and measurement
• Identify factors affecting metabolic rate

Metabolism

• Proteins, fats, carbohydrates, nucleic acids are broken down
• Food is digested, catabolism occurs, ATP is produced
• Catabolism fuels anabolism, body uses ATP produced
• Anabolism builds up body tissues and components
• Hormones regulate the process, balancing the body

Nutrient Pools and Metabolism

• Dietary fats, carbohydrates, and proteins are broken down
• Fats are stored as fat stores, excess glucose is stored as glycogen
• Glucose pool is used for energy, and glycogen stores
• Glycogenolysis (breaking down glycogen) and gluconeogenesis (producing glucose)
• Metabolism in most tissues is mainly for ATP
• Excess nutrients are generally converted/stored as fats

Food Intake and Energy

• Food intake is energy, including internal work (like blood pumping, cycling)
• Excess protein can be converted into excess glucose, eventually stored as fat
• Most ingested materials can be turned into fat

Fate of Nutrients in Fed/Fasted State

• Fed state uses glucose for energy, glycolysis, citric acid cycle
• Fed state stores glucose as glycogen, excess as fat
• Amino acids used for protein synthesis (after deamination), excess stored as fat
• Fasted state breaks down glycogen to glucose, producing more energy
• Proteins broken down, amino acids converted to glucose
• Triglycerides are broken into fatty acids and glycerol for production of energy

Energy Balance

• Anabolism and catabolism result in maintenance, growth, and use of nutrient stores
• Anaerobic catabolism in the cytosol produces limited amounts of ATP
• Aerobic metabolism in the mitochondria produces significant amounts of ATP
• Body uses ATP for various functions such as movement, transport and also endocytosis and exocytosis

Organic Material Consumption

• Creating ATP and heat through aerobic metabolism
• When consuming high nutrient amounts, anabolic activity is triggered, resulting in maintenance and storage.

Appetite and Satiety

• Hypothalamus controls eating, with feeding and satiety centers
• Hormones (ghrelin, leptin, CCK, Insulin, etc.) signal hunger and fullness
• Various peptides contribute to food intake regulation.
• Ghrelin is released from an empty stomach, stimulating food intake
• Satiety hormones like PYY and GLP-1 produce opposite effects

Energy Balance (Detailed)

• Energy intake matches energy output (work and heat)
• Input includes diet and psychological needs
• Output includes thermo-regulation plus work to support bodily processes

Metabolic Rate

• Metabolic rate (kcal/day) = (L O2 consumed/day) × (kcal/L O2)
• RQ (Respiratory Quotient): CO2 produced/O2 consumed
  • Carbohydrates: 1
  • Fats: 0.7
  • Proteins: 0.8

Factors Affecting Metabolic Rate

• Exercise increases metabolic activity due to muscle contraction heat generation
• Age decreases metabolic rate from birth to old age
• Thyroid hormones increase metabolic rate
• Sympathetic stimulation increases metabolic activity of cells (e.g. glycogenolysis)
• Gonadal hormones (e.g. testosterone) and growth hormone increase metabolic rate
• Fever increases all chemical reactions, increasing metabolism
• Climate has an effect (people in hot climates have lower metabolic rates)
• Sleep is associated with decreased metabolic rate
• Malnutrition decreases metabolic rate with prolonged fasting

This quiz explores the concepts of metabolism, energy balance, and the biochemical processes involved in catabolism and anabolism. You'll learn about how hormones regulate these processes and the impact of food intake on energy utilization and storage. Test your understanding of metabolic rates and the factors influencing them.