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

Hey there, future biologist! Let's make sure you're totally prepped for the AP Biology exam. This guide is designed to be your go-to resource, hitting all the key points and making those connections you need to ace this thing. Let's dive in!

The Four Giants: Macromolecules

These are the big players in the biological world. Understanding them is crucial. Let's break them down:

• Nucleic Acids 🧬: Genetic info carriers.
• Carbohydrates 🍩: Energy and structure.
• Proteins 🥩: Workhorses of the cell.
• Lipids 😁: Energy storage and membranes.

Remember, the shape of a molecule dictates what it does. The monomers (building blocks) and their arrangement are key. Think of it like LEGOs – different arrangements, different structures, different functions!

🧬 Nucleic Acids

Back to Top

• Monomers: Nucleotides (sugar, phosphate, nitrogenous base).

• Types: DNA (stores genetic info) and RNA (carries out instructions).

• Directionality: 5' to 3' (important for replication & transcription).

  • New nucleotides are added to the 3' end during polymerization.

• DNA Structure: Double helix, antiparallel strands.

  • A pairs with T (2 hydrogen bonds).

  • C pairs with G (3 hydrogen bonds).

  • This base pairing ensures stability and accurate genetic info transfer.

Image courtesy of Lumen Learning

Image courtesy of BioNinja

🥩 Proteins

Back to Top

• Monomers: Amino acids.
• Bonds: Peptide bonds (formed by dehydration synthesis).
• Functions: Structural, catalytic (enzymes), signaling, defense, transport.

Levels of Protein Structure

1. Primary: Sequence of amino acids.
2. Secondary: Alpha helices and beta-pleated sheets (hydrogen bonds).
3. Tertiary: 3D structure (interactions between R-groups).
4. Quaternary: Multiple polypeptide chains.

Image courtesy of Lumen Learning.

Denaturation

• Loss of tertiary structure due to heat, pH, etc.
• Leads to loss of function.
• Different from hydrolysis (breaking down into smaller pieces).

🍩 Carbohydrates

Back to Top

• Monomers: Monosaccharides (simple sugars).
• Functions: Energy source, structural support.
• Types: Linear or branched.

Image courtesy of ResearchGate

Disaccharides and Polysaccharides

• Disaccharide: Two monosaccharides linked by a glycosidic bond (formed by dehydration synthesis).

  • Maltose: Glucose + Glucose
  • Sucrose: Glucose + Fructose
  • Lactose: Glucose + Galactose

• Polysaccharides: Polymers of sugars.

  • Starch: Energy storage in plants.
  • Glycogen: Energy storage in animals.
  • Cellulose: Structural in plant cell walls.
  • Chitin: Structural in arthropod exoskeletons and fungal cell walls.

😁 Lipids

Back to Top

• Key Functions: Energy storage, cell membrane structure.
• Examples: Fats, oils, phospholipids.

Final Exam Focus

Back to Top

Okay, you're almost there! Here's what to really focus on:

• High-Yield Topics: Protein structure (especially denaturation), nucleic acid structure and base pairing, carbohydrate types and functions.
• Common Question Types: MCQs on identifying monomers, FRQs on relating structure to function, and questions combining multiple concepts.

Practice Question

Practice Questions

Multiple Choice Questions

1. Which of the following best describes the primary structure of a protein? a) The overall 3D shape of the protein b) The sequence of amino acids c) The alpha-helices and beta-pleated sheets d) The interactions between multiple polypeptide chains

2. What type of bond holds together the two strands of a DNA molecule? a) Peptide bonds b) Glycosidic bonds c) Hydrogen bonds d) Covalent bonds

3. Which polysaccharide is used for energy storage in animals? a) Cellulose b) Starch c) Glycogen d) Chitin

Free Response Question

Question:

Describe the four levels of protein structure. Explain how changes in the primary structure can affect the overall function of a protein. Provide an example of a disease caused by a change in protein structure.

Scoring Breakdown:

• Level 1 (1 point): Correctly identifies and describes the primary structure as the sequence of amino acids.
• Level 2 (1 point): Correctly identifies and describes the secondary structure as alpha helices and beta-pleated sheets formed by hydrogen bonds.
• Level 3 (1 point): Correctly identifies and describes the tertiary structure as the overall 3D shape formed by interactions between R-groups.
• Level 4 (1 point): Correctly identifies and describes the quaternary structure as the arrangement of multiple polypeptide chains.
• Effect of primary structure (2 points): Explains that changes in the primary structure (amino acid sequence) can alter the folding of the protein, leading to changes in secondary, tertiary, and quaternary structures, which can affect the protein's function.
• Example (1 point): Provides an example of a disease caused by a change in protein structure, such as sickle cell anemia (caused by a single amino acid substitution in hemoglobin).