Unit 3 Answer Key • Human Health, Nutrition & Digestion Page 1 of 4
Teacher Resource • Grading Reference
Page 2 of 4 • Nutrients
Biochemistry of Fuel, Fiber, and Cardiovascular Health Complete Model Answers & Criteria
2 pts each
7. Carbohydrates vs. Proteins: Immediate energy vs. structural & cellular roles:
Model Answer: Carbohydrates are the body's primary and preferred source of immediate cellular energy (broken down into glucose). Proteins are essential structural builders and functional molecules used for tissue repair, muscle growth, enzyme synthesis, hormone signaling, and immune antibody formation.
8. Heart Health & Dietary Fats: Most effective fat adjustment for cardiovascular health:
Model Answer: Replacing saturated fats and trans fats with unsaturated fats (monounsaturated and polyunsaturated fats, including omega-3s) alongside increasing soluble dietary fiber. Saturated and trans fats elevate LDL ("bad") cholesterol and arterial plaque, whereas unsaturated fats support healthy blood lipid levels.
2 pts each
9. Whole Fruits vs. 100% Fruit Juice: Why whole fruit is recommended:
Model Answer: Whole fruits provide intact dietary fiber along with vitamins. Fiber slows gastric emptying and carbohydrate absorption, preventing sharp blood sugar and insulin spikes while promoting satiety. Fruit juice has stripped fiber, delivering rapidly absorbed liquid fructose that causes blood glucose fluctuations.
10. Whole Grains vs. Refined Grains: Structural differences and key nutrients:
Model Answer: Whole grains (e.g., brown rice, whole oats) keep all three kernel components: the bran, germ, and endosperm. They are the principal provider of complex carbohydrates and dietary fiber, plus B vitamins and minerals. Refined grains (white bread) strip the fibrous bran and germ, leaving only starchy endosperm.
2 pts
11. Nutritional Application: Boosting protein using whole foods without powder supplements:
Model Answer: A student can substitute or add whole-food protein sources such as cottage cheese, Greek yogurt, chia or hemp seeds, natural peanut butter, or silken tofu. Protein enhances meal satiety, slows digestion, stabilizes blood sugar levels, and provides the essential amino acids needed for muscle synthesis and cellular repair throughout the day.
Unit 3 Answer Key • Human Health, Nutrition & Digestion Page 2 of 4
Teacher Resource • Grading Reference
Page 3 of 4 • Digestion
Gastrointestinal Anatomy, Motility, Villi & Secretions Complete Key & Solutions
6 pts (1 pt/step)
Step 1 Mouth (Oral Cavity)
Mastication (chewing) & salivary amylase start starch digestion.
Step 2 Esophagus
Rhythmic muscular peristalsis propels swallowed food bolus.
Step 3 Stomach
Gastric acid & pepsin churn food into acidic liquid chyme.
Step 4 Small Intestine
Primary site: 90%+ of all nutrient absorption across villi.
Step 5 Large Intestine (Colon)
Reabsorbs water & electrolytes; compacts indigestible waste.
Step 6 Rectum / Anus
Stores compacted feces prior to controlled defecation/elimination.
8 pts (1 pt/item)
G 1. Produces bile to break down dietary fats. (Liver)
D 5. Site of 90%+ nutrient absorption. (Small Intestine)
E 2. Microscopic projections expand area. (Villi)
C 6. Churns food with acid into chyme. (Stomach)
H 3. Wave-like muscular contractions. (Peristalsis)
A 7. Chewing occurs; saliva breaks starch. (Mouth)
F 4. Reabsorbs water & compacts stool. (Large Intestine)
B 8. Tube from throat to stomach. (Esophagus)
2 pts each
12. Chewing (Mastication) & Saliva:
Model Answer: Mastication mechanically breaks large food items into smaller pieces, vastly increasing the surface area for enzymes to act upon. Chemically, saliva moistens food and introduces salivary amylase to begin starch breakdown. Thorough chewing creates a lubricated bolus, preventing choking and easing esophageal transport.
13. Liver, Gallbladder & Fat Digestion:
Model Answer: The liver produces bile; bile is stored and concentrated in the gallbladder. When fats enter the duodenum of the small intestine, bile is released. Bile acts as an emulsifier, breaking large hydrophobic fat globules into tiny droplets so pancreatic lipases can efficiently digest them.
14. Small Intestine vs. Large Intestine Functions:
Model Answer: The small intestine absorbs 90%+ of all macro- and micronutrients. The large intestine reabsorbs water and electrolytes, turning liquid residue into firm stool. If transit is too fast, inadequate water is reabsorbed, resulting in diarrhea and dehydration; if transit is too slow, excessive water is reabsorbed, causing constipation.
Unit 3 Answer Key • Human Health, Nutrition & Digestion Page 3 of 4
Teacher Resource • Grading Reference
Page 4 of 4 • Evaluation
Food Label Literacy, %DV Rules & Ingredient Transparency Complete Model Answers & Criteria
Teacher Comparison Reference
Product A (Ultra-Processed Snack):
Product B (Minimally Processed Bowl):
2 pts each
15. Defining "Processed Food": Definition and why "processed" doesn't equal unhealthy:
Model Answer: A processed food is any food changed from its natural state through methods like cooking, freezing, milling, canning, or adding ingredients. Processing exists on a spectrum; minimally processed foods (like frozen spinach, canned tuna in water, or rolled oats) retain vitamins and fiber and are highly nutritious.
16. Nutrient Red Flags & The 5/20 Rule: 5% DV low vs. 20% DV high analysis:
Model Answer: On Product A, two major red flags are Added Sugars at 32% DV and Saturated Fat at 23% DV (both exceed the 20% high benchmark for nutrients to limit). On Product B, two nutrient-dense highlights are Dietary Fiber at 18% DV (near 20% benchmark for nutrients to get more of) and 0% Added Sugars.
17. Added Sugars vs. Dietary Fiber: Metabolic and digestive impacts:
Model Answer: Added sugars deliver empty calories that absorb rapidly into the bloodstream, triggering sharp insulin spikes, energy crashes, and increased fat storage. In contrast, dietary fiber forms a gel matrix in the gut, slowing carbohydrate breakdown, maintaining steady blood glucose, lowering LDL cholesterol, and signaling fullness.
18. Decoding Ingredient Lists: Order of weight and identifying Product A red flags:
Model Answer: Ingredients are listed in descending order by weight. Reviewing ingredients exposes hidden sugars, saturated fats, and artificial additives masked by deceptive packaging claims. On Product A, key red flags include high-fructose corn syrup listed second by weight, palm oil (high in saturated fat), and artificial color Red 40.
Unit 3 Answer Key • Human Health, Nutrition & Digestion Page 4 of 4
