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Phospholipids and Cell Membrane Structure

  • Phospholipids: Have hydrophilic (polar) heads and hydrophobic (nonpolar) tails.

    • Arranges in a bilayer:

    • Polar heads interact with watery environments.

    • Nonpolar tails crowd inward away from water.

  • Plasma Membrane: Fluid phospholipid bilayer surrounding cells. Essential for cell structure and function.

  • Importance: Vital to humans and other organisms.

Steroids: Structure and Function

  • Steroids: Lipids with a carbon skeleton made of four fused rings.

    • Unlike other lipids, do not contain fatty acids and are insoluble in water.

    • Types depend on functional groups attached to the carbon skeleton.

  • Cholesterol:

    • Component of plasma membranes.

    • Precursor for sex hormones like testosterone and estrogen.

  • Sex Hormones:

    • Testosterone: Formed primarily in the testes; male sex hormone.

    • Estrogen: Formed primarily in the ovaries; female sex hormone.

    • Differences in effects due to attached functional groups.

  • Anabolic Steroids:

    • Synthetic testosterone used to increase muscle mass.

    • Health risks include hormonal imbalance, atrophy of testes, potential breast development in males, facial hair growth in females, and psychological disorders.

    • Banned in professional athletics due to health risks and unfair advantages.

Nutrition Fundamentals

Learning Outcomes

  1. Distinguish among macronutrients, micronutrients, and essential nutrients.

  2. Explain why the term "empty-calorie food" is preferred over "junk food."

Importance of Nutrition

  • Proper nutrition is crucial for:

    • Immune system health.

    • Muscle and bone strength.

    • Blood circulation.

    • Growth and development.

    • Regulation of metabolism and homeostasis.

  • Nutrient deficiencies can lead to disorders. Example: Lack of Vitamin C results in weakened collagen, bleeding gums, and easy bruising.

Nutrient Characteristics

  • Essential Nutrients: Must be obtained through diet; the body cannot produce sufficient amounts. Examples include certain amino acids and most vitamins.

  • Nutrient Classes:

    • Macronutrients: Carbohydrates, lipids, proteins (needed in large quantities).

    • Micronutrients: Vitamins and minerals (needed in smaller quantities).

  • Food Composition: A slice of bread is approximately:

    • 50% carbohydrates

    • 35% water

    • 10% proteins

    • 4% lipids

Empty-Calorie Foods

  • Contain nutrients but are low in vitamins and minerals, e.g., sugar-sweetened soft drinks, cookies, pastries.

  • More accurately termed "empty-calorie foods" as they lack essential nutrients.

Dietary Guidelines

Learning Outcomes

  1. Explain the purpose of dietary guidelines.

  2. Evaluate nutrition labels.

  3. Discuss the value of dietary supplements.

  4. Summarize components of a healthy diet.

Dietary Guidelines Overview

  • Updated every 5 years to reflect nutritional science:

    • Purpose: Promote health, prevent chronic diseases, assist in weight maintenance.

    • Focuses on healthy eating patterns rather than strict nutrient limits.

Recommended Eating Patterns

  • Include:

    • A variety of vegetables and fruits.

    • Whole grains (at least half).

    • Fat-free or low-fat dairy products.

    • Lean protein sources.

    • Healthy fats (oils).

  • Limitations:

    • Added sugars < 10% of daily calories.

    • Saturated fats < 10% of daily calories.

    • Sodium < 2,300 mg per day.

    • Alcohol in moderation.

MyPlate Guidelines

  • Visual representation to assist in meal planning and proportioning food groups.

  • Emphasizes a balanced distribution of food groups throughout the day.

Nutrition Labels

Changes in Labels (2020-2021)

  • Updated to reflect realistic serving sizes and nutritional values more prominently.

  • Nutrition Facts Panel:

    • Includes serving sizes, calories, added sugars, total fat, carbs, dietary fiber, and others.

Daily Values Calculation

  • % Daily Value: Indicates how much a nutrient contributes to a daily diet based on a 2,000-calorie intake.

  • Example: For total fat, 8 g contributes to 12% if the recommended limit is 65 g.

Energy Balance

Body Mass Index (BMI)

  • Calculating BMI:

    • extBMI=racextweight(lb)extheight(in)2imes703ext{BMI} = rac{ ext{weight (lb)}}{ ext{height (in)}^2} imes 703

    • Interpreted as:

    • Underweight: < 18.5

    • Healthy: 18.5 - 24.9

    • Overweight: 25.0 - 29.9

    • Obese: 30.0 - 39.9

    • Morbidly Obese: ≥ 40.0

Energy Intake and Output

  • Caloric Values:

    • Carbohydrate and protein: 4 kcal/g

    • Fat: 9 kcal/g

    • Alcohol: 7 kcal/g

  • Energy intake must balance energy output for weight maintenance.

Estimating Daily Energy Needs

  1. Calculate metabolic function energy needs.

  2. Add energy needs based on activity level (sedentary, light, moderate, etc.).

  3. Include energy for digestion and processing (10%).

  • Example Calculation:

    • Female, 130 lbs (59 kg): metabolic needs ~ 1,274 kcal + activity ~ 701 kcal = total ~ 2,170 kcal.

Obesity Related Diseases

Health Risks

  • Type 2 Diabetes: Associated with obesity; characterized by insulin resistance and higher blood glucose levels.

  • Cardiovascular Diseases: Linked to high LDL cholesterol, affected by dietary fats (saturated and trans fats increase risk).

Eating Disorders

  • Anorexia Nervosa: Characterized by fear of weight gain and restrictive eating.

  • Bulimia Nervosa: Binge-eating followed by purging to prevent weight gain.

  • Binge-Eating Disorder: Regular episodes of overeating without purging.

  • Muscle Dysmorphia: Preoccupation with body image and muscle development, more common in males.

Important Takeaways:

  • Proper nutrition supports overall health and functioning.

  • Lifestyle and dietary choices are critical in preventing chronic diseases.

  • Awareness of dietary guidelines, nutritional content, and healthy patterns aids in maintaining health and reducing risks associated with obesity and eating disorders.