#AP Biology: Macromolecules - Your Night-Before-the-Exam Guide 🚀

Hey there, future AP Bio superstar! Let's get you feeling confident and ready to ace this exam. We're diving into macromolecules, the building blocks of life, with a focus on what you really need to know. Let's make this review count!

#Macromolecules: The Foundation of Life

Macromolecules are large molecules made of smaller subunits. They're the core of life, so understanding them is crucial. Let's break them down:

• Key Concept: Structure determines function. A slight change in a macromolecule's structure can drastically alter its function. 💡

#Carbohydrates: Fueling Life

#What are Carbohydrates?

• Sugars and polymers of sugars. Usually end in '-ose'.
• Contain multiple hydroxyl (-OH) groups and a carbonyl (C=O) group.
• Aldose: Carbonyl group at the end (aldehyde).
• Ketose: Carbonyl group in the middle (ketone).

Image: Sucrose, a disaccharide, formed by two monosaccharides

#Monosaccharides

• Simple sugars with a formula that's a multiple of CH2O (1:2:1 ratio).
• Glucose (C6H12O6): The most common monosaccharide, crucial in glycolysis.
• Fructose: Another common example.

#Lipids: Energy Storage and More

#What are Lipids?

• The only class of macromolecules that DO NOT form polymers. 🤯
• Non-polar and hydrophobic (avoid water).
• Mostly hydrocarbons.
• Important for energy storage (9 calories per gram) and insulation.
• Fats (triglycerides/triacylglycerols): Glycerol + 3 fatty acids joined by ester bonds.

#Saturated vs. Unsaturated Fatty Acids

• Glycerol: 3-carbon alcohol with -OH on each carbon.
• Fatty Acids: Long chains of carbon with a carboxyl group (-COOH).
  • Saturated: No double bonds between carbons, max H atoms, solid at room temp (e.g., butter).
  • Unsaturated: One or more double/triple bonds, liquid at room temp (e.g., plant oils).

#Phospholipids

• One fatty acid of a triglyceride is replaced by a phosphate group.
• Structure: 1 glycerol, 2 fatty acids, 1 phosphate group.
• Key Role: Major component of the cell membrane (phospholipid bilayer).
• Hydrophilic Head: Glycerol and phosphate group (attracts water).
• Hydrophobic Tail: Two fatty acids (avoids water), one saturated, one unsaturated.

Image: Phospholipid structure showing the hydrophilic head and hydrophobic tails

#Steroids

• Carbon skeleton with 4 fused rings.
• Hydrophobic and insoluble in water (like other lipids).
• Cholesterol: A steroid with a short tail and -OH group, important in animal cell membranes.
• Sterols: Steroids with a hydroxide (-OH) functional group.

#Proteins: The Workhorses of the Cell

#What are Proteins?

• Made of 20 different amino acids joined by peptide bonds (polypeptides).
• A slight change in the primary structure can alter both a protein's structure and function. ⚠️
• Energy content: 4 calories per gram.
• Dipeptide: Two amino acids joined.
• Polypeptide: Many amino acids joined by dehydration synthesis.
• Proteins are formed by the folding of one or more polypeptides.

#Amino Acid Structure

• Each amino acid has an amino group (-NH2), a carboxyl group (-COOH), and an R group.
• R group determines the amino acid's properties (polar, nonpolar, acidic, basic).
• Polar amino acids attract polar amino acids, and so on, which dictates protein folding.

Image: Basic amino acid structure with the R group highlighted

#Nucleic Acids: Information Storage

#What are Nucleic Acids?

• Contain C, H, O, N, and P.
• Made of nucleotide monomers.
• Carry genetic information (DNA).
• Nucleotide Structure: 5-carbon sugar, phosphate, and a nitrogen base (A, T, G, C, U).

Image: Nucleotide structure with its three main components

• Also make up RNA, which is a little different from DNA (more on this later!).

#Big Fat Summary Table

#Final Exam Focus

• High-Priority Topics:
  • Structure and function of each macromolecule.
  • The importance of the R group in amino acids.
  • Saturated vs. unsaturated fats.
  • Phospholipid bilayer structure.
  • The role of nucleic acids in genetic information.
• Common Question Types:
  • Multiple choice questions on identifying monomers, polymers, and linkages.
  • Free-response questions (FRQs) on explaining how structure impacts function.
  • Questions that combine macromolecule concepts with other units (e.g., cell membrane, enzymes).

#Practice Questions

Practice Question

#Multiple Choice Questions

1. Which of the following best describes the primary function of carbohydrates in living organisms? (A) Long-term energy storage (B) Short-term energy storage and structural components (C) Genetic information storage (D) Catalyzing biochemical reactions

2. A researcher identifies a molecule with a glycerol backbone, two fatty acids, and a phosphate group. This molecule is most likely a: (A) Triglyceride (B) Steroid (C) Phospholipid (D) Polypeptide

3. The unique properties of each amino acid are determined by its: (A) Amino group (B) Carboxyl group (C) R group (D) Peptide bond

#Free Response Question

Question:

Explain how the structure of a protein is related to its function. In your response, discuss the four levels of protein structure and how changes at each level can affect the protein's overall function. Provide a specific example of a protein and how its structure enables it to perform its biological role.

Scoring Breakdown:

• Level 1 (1 point):
  • Correctly identifies the primary structure as the sequence of amino acids.
• Level 2 (1 point):
  • Correctly describes the secondary structure as local folding patterns (alpha helices, beta sheets) stabilized by hydrogen bonds.
• Level 3 (1 point):
  • Correctly describes the tertiary structure as the overall 3D shape of a polypeptide, influenced by interactions between R groups.
• Level 4 (1 point):
  • Correctly describes the quaternary structure as the arrangement of multiple polypeptide chains.
• Changes at each level (2 points):
  • Explains that changes at any level (especially primary) can alter the protein's shape and therefore its function.
• Specific Example (2 points):
  • Provides a valid protein example (e.g., hemoglobin, enzymes) and explains how its structure enables its function (e.g., hemoglobin's quaternary structure facilitates oxygen binding, enzyme's active site binds to specific substrates).

You've got this! Go get that 5! 💪