03: Biological Molecules

Why is carbon important in biology?

It can form 4 covalent bonds, allowing diverse, complex organic molecules.

What percentage of cells is water vs. carbon compounds?

~70–90% water; most of the rest is carbon-based.

What are hydrocarbons?

Organic molecules made only of C and H; nonpolar, hydrophobic.

How do functional groups affect hydrocarbons?

They replace H and give molecules distinct properties.

Hydroxyl group (-OH): properties & examples? Hydroxy Has One Hug

Polar, hydrophilic; found in alcohols (names end in -ol).

Carbonyl group (C=O): properties & examples?

Polar, hydrophilic; found in sugars.

Carboxyl group (-COOH): properties & examples?

Acidic, hydrophilic; found in amino acids & fatty acids; can release H⁺.

Amino group (-NH₂): properties & examples? Amino Always Needs Hydrogen Too (–NH₂).”

Basic, hydrophilic; found in amino acids; can accept H⁺.

Phosphate group (-OPO₃²⁻): properties & examples?

Acidic, hydrophilic; found in ATP, nucleic acids, phospholipids.

Methyl group (-CH₃): properties & examples?

Nonpolar, hydrophobic; found in DNA methylation (gene regulation).

What is a macromolecule?

A very large molecule made of thousands of atoms.

What is a polymer?

A macromolecule made of repeating monomers.

What is dehydration synthesis?

A reaction that removes water to form bonds between monomers (polymer building).

What enzyme type catalyzes dehydration synthesis?

Dehydrogenases.

What is hydrolysis?

A reaction that adds water to break bonds between monomers (polymer breakdown).

What enzyme type catalyzes hydrolysis?

Hydrolases.

Which biological macromolecules are polymers?

Carbohydrates, proteins, nucleic acids (lipids are NOT polymers).

General formula for carbohydrates?

(CH₂O)ₙ.

What are the main functions of carbohydrates?

Energy (fuel) and structure.

What is a monosaccharide? Example?

A single sugar monomer, e.g., glucose (C₆H₁₂O₆).

What is a polysaccharide?

A polymer of many monosaccharides linked by glycosidic bonds.

Storage polysaccharides?

Starch (plants), glycogen (animals).

Structural polysaccharides?

Cellulose (plant cell walls), chitin (fungi & arthropod exoskeletons).

Are lipids polymers?

No, they are hydrophobic macromolecules but not polymers.

General property of lipids?

Hydrophobic, dissolve in nonpolar solvents.

3 main types of lipids?

Fats, phospholipids, steroids.

What are fats made of?

Glycerol + 1–3 fatty acids (linked via ester bonds).

Energy yield of fats vs. carbs/proteins?

Fats = 9 Cal/g; carbs/proteins = 4 Cal/g.

What are phospholipids made of?

Glycerol + 2 fatty acid tails + phosphate group.

Why are phospholipids amphipathic?

They have hydrophobic fatty acid tails and hydrophilic phosphate heads.

What are steroids made of?

3 six-carbon rings + 1 five-carbon ring with variable functional groups.

Roles of steroids?

Membrane structure and signaling (hormones).

What are proteins made of?

Polymers of amino acids linked by peptide bonds.

General structure of an amino acid?

Central C bonded to H, amino group (-NH₂), carboxyl group (-COOH), and R group.

How many amino acids are common in life?

20.

Types of amino acid side chains?

Nonpolar, polar, charged (acidic or basic).

What is a polypeptide?

A linear chain of amino acids linked by peptide bonds.

When does a polypeptide become a protein?

When folded into its correct 3D shape.

What are the four levels of protein structure?

Primary (sequence), Secondary (localized folding via H-bonds), Tertiary (3D folding via side chains), Quaternary (multiple polypeptides together).

Example of quaternary protein?

Hemoglobin.

What is denaturation?

Loss of a protein’s native structure (and function) due to pH, salt, or heat.

Functions of proteins?

Structure, communication/signaling, enzymes, defense, transport (not heredity).

What are the two main nucleic acids?

DNA and RNA.

Function of nucleic acids?

Store and transmit genetic information.