Biological Molecules (Macromolecules)

Why This Matters for Nursing: These molecules make up your body and the food you eat. Understanding carbohydrates, proteins, lipids, and nucleic acids helps you understand nutrition, diabetes, metabolism, and many disease processes.

What You Need to Know

Macromolecules are large molecules essential for life. There are four main types:

🧠 Memory Trick

"CPLNK" — Carbs, Proteins, Lipids, Nucleic acids are the Key molecules

What they're made of: - Carbs = "saccharides" (sugars) - Proteins = "amino acids" (there are 20) - Lipids = "fatty acids" (fats and oils) - Nucleic acids = "nucleotides" (DNA and RNA)

Carbohydrates

Function: Quick energy source; structural support

Types:

Key Facts:

• Glucose = primary energy source for cells
• Glycogen = storage form in humans (liver, muscles)
• Starch = storage form in plants
• Cellulose = plant fiber (we can't digest it)

Chemical formula: (CH₂O)ₙ — "hydrate of carbon"

Proteins

Function: Structure, enzymes, transport, immunity, movement

Structure Levels:

Key Facts:

• Made of 20 different amino acids
• Amino acids linked by peptide bonds
• Enzymes are proteins that speed up reactions
• Hemoglobin = protein that carries oxygen in blood
• Antibodies = proteins of the immune system
• Shape determines function — denatured proteins don't work

Lipids

Function: Long-term energy storage, cell membranes, hormones, insulation

Types:

Key Facts:

• Saturated fats = no double bonds (solid at room temp, "bad" fats)
• Unsaturated fats = has double bonds (liquid at room temp, "good" fats)
• Phospholipids make up the cell membrane (hydrophilic head, hydrophobic tails)
• Cholesterol is needed for cell membranes and making hormones
• Lipids are hydrophobic (don't mix with water)

Nucleic Acids

Function: Store and transmit genetic information

Types:

Structure:

• Made of nucleotides
• Each nucleotide = sugar + phosphate + base
• Bases: A, T (U in RNA), G, C

✏️ Worked Examples

Example 1: Identify the Macromolecule

Question: A patient is diabetic and monitors glucose levels. Glucose is what type of macromolecule?

Step 1 — Know what glucose is. Glucose is a simple sugar. "Sugar" = carbohydrate territory. More specifically, glucose is a monosaccharide — the prefix "mono" means one, so a monosaccharide is a single sugar unit. It's the smallest carbohydrate.

Step 2 — Connect glucose to diabetes. In diabetes, the body either doesn't make enough insulin or doesn't respond to it properly. Insulin's job is to take glucose out of the blood and move it into cells. Without working insulin, glucose piles up in the bloodstream — which is why diabetics monitor blood glucose (blood sugar) levels.

Answer: Carbohydrate (specifically, a monosaccharide)

🏥 Nursing connection: When you check a patient's blood glucose with a finger stick, you're measuring how much of this monosaccharide is floating in their blood. Normal fasting glucose is 70–100 mg/dL. Higher = hyperglycemia. Lower = hypoglycemia. Both are emergencies.