BIO 155 – Nutrition: Study Guide for Test 1 (Chapters 1–5)

Chapter 1 – Science of Nutrition

Factors Influencing Food Choices

Understanding why individuals choose certain foods is essential in nutrition science. Multiple factors influence these choices, impacting overall health and dietary patterns.

• Taste and Enjoyment: The primary driver for most food choices; people prefer foods that taste good to them.

• Culture and Environment: Cultural background and surroundings shape food preferences and eating habits.

• Social Life and Trends: Social gatherings, peer influence, and current trends can affect what and how much people eat.

• Nutrition Knowledge: Awareness of nutrition information can guide healthier choices.

• Advertising: Marketing strategies can influence perceptions and consumption of certain foods.

• Time, Convenience, and Cost: Busy lifestyles and budget constraints often dictate food selection.

• Habits and Emotions: Routine and emotional states (e.g., stress eating) play a role in dietary decisions.

Six Categories of Nutrients

Nutrients are substances in food that are essential for health, growth, and energy. They are classified into six main categories:

• Carbohydrates

• Lipids (Fats and Oils)

• Proteins

• Vitamins

• Minerals

• Water

Each nutrient category plays unique roles in the body, from providing energy to supporting metabolic processes.

Chapter 2 – Nutrition Resources

Nutrient Density vs. Energy Density

Understanding the difference between nutrient-dense and energy-dense foods is crucial for making healthy dietary choices.

• Nutrient-Dense Foods: High in vitamins, minerals, and other beneficial substances with relatively few calories (e.g., vegetables).

• Energy-Dense Foods: High in calories per gram, often due to high fat or sugar content (e.g., desserts).

Dietary Reference Intakes (DRIs)

DRIs are a set of reference values used to plan and assess nutrient intakes of healthy people. They are specific to age, sex, and life stage.

• Recommended Dietary Allowance (RDA): Average daily intake level sufficient to meet the nutrient requirements of nearly all (97–98%) healthy individuals.

Dietary Guidelines for Americans (DGAs)

The DGAs provide science-based advice to promote health and reduce the risk of chronic diseases. They are updated every five years. The 2026 DGAs will include new recommendations and may address controversial topics.

MyPlate

MyPlate is a visual guide to help consumers build healthy meals, illustrating the proportions of different food groups.

Nutrition Facts Panel

The Nutrition Facts Panel is required on many packaged foods, providing information on serving size, calories, and nutrient content to help consumers make informed choices.

Chapter 3 – The Digestive System

Overview of Digestion

Digestion is the process by which food is broken down into absorbable units. It involves both mechanical and chemical processes.

• Mechanical Digestion: Physical breakdown of food into smaller pieces, increasing surface area for enzymes (e.g., chewing, stomach churning).

• Chemical Digestion: Enzymatic breakdown of complex molecules into monomers (e.g., proteins into amino acids).

Absorption

Absorption is the movement of digested nutrients from the gastrointestinal (GI) tract into the bloodstream or lymphatic system.

Gastrointestinal Tract and Accessory Organs

The GI tract is a continuous tube from mouth to anus. Accessory organs secrete substances that aid digestion but do not directly contact food.

• GI Tract Organs: Mouth, pharynx, esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine, rectum, anus.

• Accessory Organs: Salivary glands, liver, gallbladder, pancreas.

Key Digestive Processes by Organ

• Mouth: Begins mechanical digestion and chemical digestion of carbohydrates (via salivary amylase).

• Stomach: Secretes gastric juice (contains HCl, pepsinogen, mucus, intrinsic factor); initiates protein digestion.

• Duodenum: First section of small intestine; regulates stomach activity and signals pancreas/gallbladder via hormones.

• Small Intestine: Completes digestion and absorbs most nutrients.

• Large Intestine: Absorbs water and forms feces; recovers about 90% of water entering it.

Digestive Secretions

• Saliva: Contains amylase for carbohydrate digestion.

• Gastric Juice: Contains HCl (acidic pH), pepsinogen (activated to pepsin for protein digestion), mucus (protects stomach lining), intrinsic factor (vitamin B12 absorption).

• Pancreatic Juice: Contains digestive enzymes and bicarbonate ions to neutralize stomach acid.

• Bile: Produced by the liver, stored in the gallbladder; contains bile salts to emulsify fats.

• Intestinal Juice: Contains digestive enzymes.

• Mucus: Protects GI tract tissues.

Digestive Hormones

• Gastrin: Stimulates stomach to secrete gastric juice.

• Secretin: Signals pancreas to release bicarbonate-rich juice to raise pH in duodenum.

• Cholecystokinin (CCK): Signals gallbladder to contract and release bile into duodenum.

Absorption and Transport of Nutrients

• Most nutrients enter the bloodstream and are first processed by the liver.

• Lipids: Not water-soluble; absorbed into intestinal cells, packaged into chylomicrons, and transported via lymphatic system (lacteals) before entering the bloodstream.

Chapter 4 – Carbohydrates

Types of Carbohydrates

• Monosaccharides: Single sugar units (glucose, fructose, galactose). Glucose is the primary energy source for the body.

• Disaccharides: Two monosaccharides bonded together (sucrose, maltose, lactose). Lactose intolerance results from insufficient lactase enzyme.

• Oligosaccharides: 3–10 monosaccharide units; found in plant cell walls, not digestible by humans but fermented by gut bacteria (causing gas and bloating).

• Polysaccharides: Long chains (10+ units); includes starch (digestible), glycogen (animal storage form), and fiber (mainly cellulose, indigestible).

Functions and Importance

• Starch: Main digestible polysaccharide in plants.

• Glycogen: Short-term energy storage in liver and muscles.

• Fiber: Promotes digestive health; soluble fiber helps remove cholesterol, insoluble fiber aids bowel movement.

Blood Glucose Regulation

The body maintains steady blood glucose levels through hormonal regulation and glycogen storage/release.

• Insulin: Produced by pancreas when blood glucose is high; promotes glucose uptake by cells.

• Glucagon: Produced by pancreas when blood glucose is low; stimulates glycogen breakdown and gluconeogenesis in the liver.

Dietary Recommendations and Glycemic Index

• RDA for Carbohydrates: 130 grams per day for most adults (higher for pregnant/lactating women).

• Whole Grains: Preferred over refined grains due to higher fiber and nutrient content.

• Glycemic Index (GI): Ranks foods by how quickly they raise blood glucose; high-GI foods cause rapid spikes and are less suitable for diabetics.

Added Sugars and Sugar Substitutes

• Added Sugars: Excessive intake (especially from sweetened beverages) is a major dietary concern.

• Sugar Substitutes: Used to sweeten foods without adding calories.

Chapter 5 – Lipids

Types and Structure of Lipids

• Fatty Acids: Basic monomers of lipids; can be saturated (no double bonds) or unsaturated (one or more double bonds).

• Triglycerides: Main form of fat in the diet and body; composed of three fatty acids attached to a glycerol backbone.

• Phospholipids: Similar to triglycerides but with two fatty acids and a phosphate group; key components of cell membranes.

• Sterols (e.g., Cholesterol): Complex ring structures; cholesterol is essential but excess intake is linked to heart disease.

Physical Properties and Health Implications

• Saturated Fats: Solid at room temperature; found in animal products (e.g., butter, lard).

• Unsaturated Fats: Liquid at room temperature; found in plant oils; generally healthier and easier to digest.

• Essential Fatty Acids: Linoleic acid (omega-6) and alpha-linolenic acid (omega-3); precursors to eicosanoids (signaling molecules).

Lipid Digestion and Absorption

• Lipases: Enzymes that digest fats; lingual lipase (infants), gastric lipase (stomach), pancreatic lipase (small intestine).

• Bile: Emulsifies fats, increasing surface area for enzyme action.

• Absorption: Lipids are packaged into chylomicrons, transported via lymphatic system before entering the bloodstream.

Lipoproteins

Lipoproteins transport lipids in the blood. There are four main types, each with distinct roles (see figures 5.14 and 5.15 for details):

• Chylomicrons: Transport dietary lipids from intestines to tissues.

• Very-Low-Density Lipoproteins (VLDL): Carry triglycerides from liver to tissues.

• Low-Density Lipoproteins (LDL): Deliver cholesterol to cells; high levels associated with heart disease.

• High-Density Lipoproteins (HDL): Remove excess cholesterol from tissues and transport it to the liver for excretion.

Cholesterol and Heart Disease

• Cholesterol: Essential for cell membranes and hormone synthesis; excess dietary cholesterol can contribute to atherosclerosis (hardening of arteries).

• Atherosclerosis: Build-up of cholesterol-rich plaques in arteries, increasing risk of heart attack and stroke.

Lipid Type	Main Function	Health Impact
Saturated Fat	Energy storage, insulation	Increases LDL, risk of heart disease
Unsaturated Fat	Cell membrane structure, hormone synthesis	May reduce LDL, beneficial for heart health
Cholesterol	Cell membranes, precursor for hormones	Excess linked to atherosclerosis
Phospholipids	Cell membrane structure	Generally neutral

Example: Olive oil is rich in unsaturated fats and is considered heart-healthy, while butter is high in saturated fats and should be consumed in moderation.

Additional info: Where figures or pages are referenced (e.g., Fig. 5.12, 5.13, 5.14, 5.15, 5.22), students should consult their textbook for visual diagrams of lipid absorption, lipoprotein transport, and atherosclerosis development.