Macromolecules: The Big Guns of Biology (Module 5 Study Guide )

Part 1: Building Big from Small (Monomers & Polymers)

• Macromolecule Mania: Carbohydrates, lipids, proteins, and nucleic acids – these are the four main types of macromolecules. They're built from smaller, simpler units.

• Polymers: Chains of Goodness: Carbs, proteins, and nucleic acids are polymers – long chains of repeating units called monomers. Think of it like a train made of individual cars.

• Dehydration: Building Bonds: Monomers link together through dehydration reactions – losing a water molecule in the process. It's like gluing the train cars together. This requires energy!

• Hydrolysis: Breaking Bonds: Hydrolysis is the reverse – adding water to break the bonds between monomers. It's like taking the train cars apart. This happens during digestion.

• Enzymes: The Catalysts: Enzymes are special proteins that speed up these reactions (both dehydration and hydrolysis). They're like the train conductors, making sure everything runs smoothly.

• Variety is the Spice of Life: Even with only 40-50 different monomers, you can make tons of different polymers. It's like having a box of LEGOs – endless possibilities!

Part 2: Carbohydrates: Energy & Structure

• Carbs: Sugars & Their Friends: Carbohydrates are all about sugars and their polymers. Monosaccharides are simple sugars (like glucose), disaccharides are double sugars (like sucrose), and polysaccharides are complex carbs (like starch).

• Monosaccharides: Sweet Simplicity: Monosaccharides have the formula (CH2O)n. They have a carbonyl group (C=O) and hydroxyl groups (-OH). They can be aldoses (aldehyde sugars) or ketoses (ketone sugars).

• Glucose: The Fuel of Life: Glucose is the most important monosaccharide. Cells use it for energy in cellular respiration.

• Disaccharides: Double the Fun: Two monosaccharides join together through a glycosidic linkage (another dehydration reaction). Maltose, sucrose, and lactose are examples.

• Polysaccharides: Storage & Structure: Polysaccharides are the big guys. Starch (in plants) and glycogen (in animals) store glucose. Cellulose (in plant cell walls) and chitin (in insect exoskeletons and fungi cell walls) provide structure.

• Starch: Plant Energy: Plants store glucose as starch. We can digest it because we have enzymes that can break the alpha (α) linkages.

• Glycogen: Animal Energy: Animals store glucose as glycogen, which is like a branched version of amylopectin (a branched form of starch).

• Cellulose: Plant Power: Cellulose is a tough polysaccharide in plant cell walls. We can't digest it because it has beta (β) linkages. It’s the “fiber” in our diet.

• Chitin: Tough Stuff: Chitin is similar to cellulose, but with a nitrogen-containing group. It's in insect exoskeletons and fungal cell walls.

Part 3: Lipids: Hydrophobic Heroes

• Lipids: Water-Fearing: Lipids are hydrophobic (water-fearing) because they're mostly hydrocarbons. They include fats, phospholipids, and steroids.

• Fats (Triglycerides): Energy Storage: Fats are made of glycerol and three fatty acids. They're great for storing energy.

• Fatty Acids: Saturated vs. Unsaturated: Saturated fatty acids have no double bonds (straight chains, solid at room temperature). Unsaturated fatty acids have double bonds (kinks in the chain, liquid at room temperature).

• Phospholipids: Cell Membrane Masters: Phospholipids have a hydrophilic (water-loving) head and hydrophobic tails. They form the lipid bilayer of cell membranes.

• Steroids: Ring Leaders: Steroids have four fused rings. Cholesterol is a steroid that's important in cell membranes and is a precursor to other steroids (like hormones).

Part 4: Proteins: The Workhorses of Life

• Proteins: Do It All: Proteins are involved in everything – structure, storage, transport, communication, movement, defense, and especially catalysis (as enzymes).

• Amino Acids: Protein Building Blocks: Proteins are made of amino acids. There are 20 different amino acids, each with a different R-group (side chain).

• Polypeptides: Amino Acid Chains: Amino acids link together through peptide bonds to form polypeptide chains.

• Protein Conformation: Shape Matters: A protein's shape determines its function.

• Protein Structure: Four Levels:

  • Primary: The amino acid sequence.

  • Secondary: Coils (alpha helix) and folds (beta pleated sheet) due to hydrogen bonds.

  • Tertiary: Overall 3D shape due to interactions between R-groups (hydrophobic/hydrophilic interactions, ionic bonds, disulfide bridges).

  • Quaternary: Two or more polypeptide chains come together.

• Denaturation: Unfolding Trouble: If a protein's environment changes (pH, temperature, etc.), it can unfold (denature) and lose its function.

• Chaperonins: Folding Helpers: Chaperonins are proteins that help other proteins fold correctly.

Part 5: Nucleic Acids: Information Central

• Nucleic Acids: DNA & RNA: Nucleic acids store and transmit genetic information. DNA is the blueprint, and RNA helps carry out the instructions.

• Nucleotides: Nucleic Acid Building Blocks: Nucleic acids are made of nucleotides. Each nucleotide has a sugar (deoxyribose in DNA, ribose in RNA), a phosphate group, and a nitrogenous base.

• Nitrogenous Bases: A, T, G, C, U: Adenine (A) and guanine (G) are purines. Cytosine (C), thymine (T), and uracil (U) are pyrimidines. DNA uses A, T, G, and C. RNA uses A, U, G, and C.

• DNA: Double Helix: DNA is a double helix – two strands of nucleotides twisted together. Pairs with T, and G pairs with C.

• RNA: Single Strand: RNA is usually a single strand. mRNA carries genetic information from DNA to ribosomes.

• Gene Expression: DNA → RNA → Protein: DNA's information is used to make RNA (transcription), and RNA's information is used to make protein (translation)