Exam II Study Guide: Nutrition Core Concepts (Chapters 6, 8, 14, 15, 16)

Chapter 6: Proteins and Amino Acids

General Structure and Function of Amino Acids

Amino acids are the building blocks of proteins, each containing a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a unique side chain (R group). Understanding their structure is essential for grasping protein synthesis and metabolism.

• General Chemical Structure: Amino acids differ from lipids and sugars by containing both an amino group (-NH2) and a carboxyl group (-COOH).

• Side Chains: The R group determines the properties and classification of each amino acid.

• Essential vs. Non-Essential Amino Acids: Essential amino acids cannot be synthesized by the body and must be obtained from the diet; non-essential amino acids can be synthesized internally.

• Peptide Bonds: Amino acids connect via peptide bonds to form polypeptides and proteins.

• Protein Structure: Proteins have four levels of structure: primary, secondary, tertiary, and quaternary. The 3D shape (tertiary structure) is crucial for biological function.

• Protein Denaturation: Physical or chemical factors can disrupt protein structure, affecting function.

• Energy Content: Proteins, carbohydrates, and fats provide energy; proteins yield 4 kcal/g.

• Protein Digestion: Digestion begins in the stomach and continues in the small intestine, involving enzymes like pepsin and trypsin.

• Protein Quality: Complete proteins contain all essential amino acids; incomplete proteins lack one or more.

• Nitrogen Balance: Indicates protein status; positive balance suggests growth, negative balance indicates breakdown.

• Recommended Protein Intake: The Recommended Dietary Allowance (RDA) for protein is typically 0.8 g/kg body weight.

• Urea Cycle: The process by which the body disposes of excess nitrogen from amino acid breakdown.

Example: Animal proteins (e.g., eggs, meat) are complete proteins, while most plant proteins are incomplete.

Additional info: The formula for calculating protein requirement: $\text{Protein (g)} = \text{Body weight (kg)} \times 0.8$

Chapter 8: Energy Metabolism and Carbohydrates

Metabolic Pathways and Energy Production

Energy metabolism involves the breakdown of carbohydrates, fats, and proteins to produce ATP, the energy currency of the cell. Key metabolic pathways include glycolysis, Krebs cycle, and electron transport chain.

• Anaerobic vs. Aerobic Processes: Anaerobic metabolism occurs without oxygen (e.g., glycolysis), while aerobic metabolism requires oxygen (e.g., Krebs cycle, electron transport chain).

• Glycolysis: The breakdown of glucose to pyruvate, yielding ATP. Occurs in the cytoplasm.

• Krebs Cycle (Citric Acid Cycle): Occurs in mitochondria; processes acetyl-CoA to produce NADH, FADH2, and ATP.

• Electron Transport Chain: Uses electrons from NADH and FADH2 to generate ATP.

• Catabolic vs. Anabolic Pathways: Catabolic pathways break down molecules for energy; anabolic pathways build complex molecules.

• Fuel Prioritization: The body uses carbohydrates first, then fats, and finally proteins for energy.

• Glycogen Storage: Excess glucose is stored as glycogen in liver and muscle; excess energy can be stored as fat.

• Energy Storage: Glycogen stores are limited; fat stores are more extensive.

Example: During high-intensity exercise, the body relies more on anaerobic glycolysis; during prolonged, moderate exercise, aerobic metabolism predominates.

Additional info: Glycogen can be converted to glucose via glycogenolysis; glucose can be converted to fat via lipogenesis.

Chapters 14 & 15: Energy Balance and Body Composition

Energy Expenditure and Regulation

Energy balance is the relationship between energy intake and energy expenditure. Maintaining energy balance is crucial for healthy body weight and composition.

• Components of Energy Expenditure: Basal Metabolic Rate (BMR), Thermic Effect of Food (TEF), and Thermic Effect of Exercise (TEE).

• BMR: The energy required for basic physiological functions at rest.

• TEF: The energy used to digest, absorb, and metabolize food.

• TEE: The energy expended during physical activity.

• Adipose Tissue: Stores excess energy as fat; involved in hormone regulation.

• Leptin: A hormone produced by adipose tissue that regulates appetite and energy balance.

• Weight Gain/Loss: Occurs when energy intake exceeds/exceeds energy expenditure.

• Extreme Obesity: May require medical interventions such as bariatric surgery.

Example: A person with a high BMR burns more calories at rest than someone with a low BMR.

Additional info: The formula for BMR (Mifflin-St Jeor Equation): $\text{BMR} = 10 \times \text{weight (kg)} + 6.25 \times \text{height (cm)} - 5 \times \text{age (years)} + 5$ (men) $\text{BMR} = 10 \times \text{weight (kg)} + 6.25 \times \text{height (cm)} - 5 \times \text{age (years)} - 161$ (women)

Chapter 16: Exercise, Energy, and Weight Management

Physical Activity and Energy Use

Physical activity increases energy expenditure and is a key factor in weight management. Understanding the relationship between exercise, energy use, and body composition is essential for nutrition students.

• Maximal Heart Rate: The highest heart rate an individual can achieve during maximal exercise. Formula: $\text{Max HR} = 220 - \text{age}$

• Glycogen Reserves: Glycogen is the primary storage form of carbohydrate in muscle and liver; reserves are depleted during prolonged exercise.

• Aerobic vs. Anaerobic Exercise: Aerobic exercise uses oxygen and is sustained over longer periods; anaerobic exercise is high-intensity and short-duration.

• Oxygen Debt: The amount of oxygen required to restore normal metabolic conditions after exercise.

• Energy Equivalent of Activity: 1 mile of jogging burns approximately 100 kcal; 1 pound of body fat equals about 3,500 kcal.

• Training Plateaus: Occur when progress stalls due to adaptation; overcoming plateaus requires changes in intensity or type of exercise.

• Calculating Weight Loss: To lose 1 pound of fat, a deficit of 3,500 kcal is needed. For example, running 35 miles (at 100 kcal/mile) would burn 3,500 kcal.

Example: If a person wants to lose 2 pounds, they need a total deficit of 7,000 kcal, which could be achieved by running 70 miles.

Additional info: Slow, sustained movements use aerobic pathways; fast, explosive movements use anaerobic pathways.

Summary Table: Key Concepts in Nutrition and Energy Metabolism

Concept	Definition	Key Formula	Example/Application
Protein RDA	Recommended daily protein intake	$\text{Protein (g)} = \text{Body weight (kg)} \times 0.8$	60 kg person: 48 g protein/day
BMR	Basal Metabolic Rate	$\text{BMR} = 10 \times \text{weight (kg)} + 6.25 \times \text{height (cm)} - 5 \times \text{age (years)} + 5$ (men)	Calculates daily energy needs at rest
Max HR	Maximal Heart Rate	$\text{Max HR} = 220 - \text{age}$	30-year-old: 190 bpm
Energy Equivalent of Fat	Calories in 1 lb body fat	3,500 kcal	To lose 1 lb, burn 3,500 kcal
Glycogen Storage	Storage form of glucose	—	Liver and muscle