7.4 Metabolism and Energy Balance

Metabolism is the body's engine, converting food into energy for life. It's a complex dance of breaking down nutrients and building up essential compounds, all regulated by hormones and enzymes to keep your body running smoothly.

Energy balance is key to maintaining a healthy weight. When you eat more calories than you burn, you gain weight. When you burn more than you eat, you lose weight. Understanding this balance helps you make smart food and exercise choices.

Metabolism and Energy Balance

Definition and Role in Energy Production

Top images from around the web for Definition and Role in Energy Production

• 

  Overview of Metabolic Reactions | Anatomy and Physiology II View original

  Is this image relevant?

• 

  Functions of Human Life | Anatomy and Physiology I View original

  Is this image relevant?

• 

  Diet, Digestion, and Energy Storage Regulation | Boundless Anatomy and Physiology View original

  Is this image relevant?

• 

  Overview of Metabolic Reactions | Anatomy and Physiology II View original

  Is this image relevant?

• 

  Functions of Human Life | Anatomy and Physiology I View original

  Is this image relevant?

1 of 3

Top images from around the web for Definition and Role in Energy Production

• 

  Overview of Metabolic Reactions | Anatomy and Physiology II View original

  Is this image relevant?

• 

  Functions of Human Life | Anatomy and Physiology I View original

  Is this image relevant?

• 

  Diet, Digestion, and Energy Storage Regulation | Boundless Anatomy and Physiology View original

  Is this image relevant?

• 

  Overview of Metabolic Reactions | Anatomy and Physiology II View original

  Is this image relevant?

• 

  Functions of Human Life | Anatomy and Physiology I View original

  Is this image relevant?

1 of 3

• Metabolism the sum of all chemical reactions occurring within an organism to maintain life
  • Includes breakdown of molecules to obtain energy (catabolism)
  • Involves synthesis of compounds needed by cells (anabolism)
• Essential for energy production converts nutrients into usable energy in the form of adenosine triphosphate (ATP)
• Regulated by hormones, enzymes, and other factors to maintain homeostasis and ensure efficient energy utilization

Basal Metabolic Rate (BMR)

• Represents the minimum energy required to maintain vital functions at rest
• Influenced by factors such as age, sex, body composition, and genetics

Catabolism vs Anabolism

Catabolism

• Breakdown of complex molecules into simpler ones, releasing energy in the process
  • Examples: breakdown of glucose during glycolysis, oxidation of fatty acids during beta-oxidation
• Catabolic processes are exergonic, meaning they release energy

Anabolism

• Synthesis of complex molecules from simpler ones, requiring an input of energy
  • Examples: synthesis of proteins from amino acids, formation of glycogen from glucose
• Anabolic processes are endergonic, meaning they require energy input

Energy Balance

• Maintained when energy consumed through food equals energy expended through basal metabolism, physical activity, and thermogenesis
• Positive energy balance occurs when energy intake exceeds expenditure, leading to weight gain and potential health issues (obesity)
• Negative energy balance occurs when energy expenditure exceeds intake, resulting in weight loss and potential malnutrition if prolonged

Metabolic Pathways for Macronutrients

Carbohydrate Metabolism

• Glycolysis: breakdown of glucose into pyruvate, generating ATP and NADH in the cytoplasm
• Citric acid cycle (Krebs cycle): oxidation of acetyl-CoA derived from pyruvate, fatty acids, and amino acids in the mitochondrial matrix, producing NADH, FADH2, and ATP
• Electron transport chain and oxidative phosphorylation: generation of ATP through the transfer of electrons from NADH and FADH2 to oxygen in the mitochondrial inner membrane
• Gluconeogenesis: synthesis of glucose from non-carbohydrate precursors (amino acids, glycerol) in the liver and kidneys

Lipid Metabolism

• Beta-oxidation: breakdown of fatty acids into acetyl-CoA in the mitochondrial matrix, generating NADH and FADH2 for ATP production
• Ketogenesis: formation of ketone bodies (acetoacetate, beta-hydroxybutyrate, acetone) from acetyl-CoA in the liver during periods of low carbohydrate availability or prolonged fasting
• Lipogenesis: synthesis of fatty acids from excess acetyl-CoA, primarily in the liver and adipose tissue, and their storage as triglycerides
  • Occurs when energy intake exceeds expenditure

Protein Metabolism

• Transamination: transfer of an amino group from an amino acid to an alpha-keto acid, forming a new amino acid and alpha-keto acid
• Deamination: removal of the amino group from an amino acid, generating ammonia (converted to urea) and an alpha-keto acid that can enter the citric acid cycle
• Glucogenic amino acids: amino acids that can be converted to glucose through gluconeogenesis (alanine, glutamine)
• Ketogenic amino acids: amino acids that can be converted to ketone bodies (leucine, lysine)

Factors Influencing Energy Balance

Dietary Factors

• Macronutrient composition (carbohydrates, proteins, fats) and caloric content of food influence energy intake and balance
• High-fat and high-sugar diets can lead to excessive energy intake and weight gain

Physical Activity and Exercise

• Regular exercise increases energy expenditure, helps maintain a healthy body weight, and improves overall metabolic health
• Sedentary lifestyle contributes to reduced energy expenditure and increased risk of obesity

Hormonal Regulation

• Hormones such as insulin, glucagon, leptin, and ghrelin play crucial roles in regulating appetite, energy storage, and utilization
  • Insulin promotes glucose uptake and storage, while glucagon stimulates glucose release from the liver
  • Leptin signals satiety, while ghrelin stimulates hunger
• Hormonal imbalances can contribute to obesity and metabolic disorders (type 2 diabetes)

Genetic and Environmental Factors

• Variations in genes involved in metabolism, appetite regulation, and energy expenditure can influence an individual's susceptibility to weight gain or obesity
• Environmental and social factors (access to healthy food options, socioeconomic status, cultural influences) can impact dietary choices and energy balance
• Imbalances in energy metabolism can lead to increased risk of cardiovascular disease, certain cancers, and other health problems
• Maintaining a healthy energy balance through a balanced diet, regular physical activity, and managing stress is crucial for optimal health and disease prevention