Unit 1: Carbon and the Molecular Diversity of Life

What makes carbon able to form large, complex molecules?

Carbon has 4 valence electrons and can form up to 4 covalent bonds.

What types of bonds can carbon form?

Single, double, or triple covalent bonds.

What shapes can carbon-based molecules form?

Chains, branched molecules, or rings.

What elements are most commonly found in living organisms?

C, H, O, N, S, P

What must all organic molecules contain?

Carbon and hydrogen.

What are isomers?

Molecules with the same molecular formula but different structures.

Example of isomers in biology?

Glucose and fructose (C₆H₁₂O₆)

Why are isomers important biologically?

Different structures result in different functions.

What determines the chemical behavior of organic molecules?

Their functional groups.

What does the hydroxyl group (-OH) do?

Found in alcohols; helps dissolve molecules like sugars.

What does the carboxyl group (-COOH) do?

Acts as an acid; donates H⁺ ions.

What does the carbonyl group (>CO) do?

Found in ketones and aldehydes (like sugars).

What does the amino group (-NH₂) do?

Acts as a base; found in amino acids.

What does the phosphate group (-PO₄) do?

Important in ATP, DNA, phospholipids.

What does the sulfhydryl group (-SH) do?

Forms disulfide bridges in proteins (in cysteine).

What does the methyl group (-CH₃) do?

Affects gene expression when added to DNA.

What are polymers?

Long molecules made of repeating subunits (monomers).

What reaction builds polymers?

Dehydration synthesis (removal of water).

What reaction breaks down polymers?

Hydrolysis (addition of water).

What are carbohydrates used for?

Fuel and structural support.

What is the general formula for carbohydrates?

CH₂O (1:2:1 ratio of C:H:O)

What are monosaccharides?

Simple sugar monomers (e.g., glucose, ribose).

What are polysaccharides?

Carbohydrate polymers made of many monosaccharides.

Examples of polysaccharides?

Starch, glycogen, cellulose, chitin.

What is starch?

A storage polysaccharide in plants; digestible (alpha linkages).

What is glycogen?

A storage polysaccharide in animals; stored in liver/muscles.

What is cellulose?

Structural polysaccharide in plant cell walls; indigestible (beta linkages).

What is chitin?

Structural polysaccharide in exoskeletons and fungi.

Why can humans digest starch but not cellulose?

Different glycosidic linkages (alpha vs beta).

Are lipids polymers?

No; they are assembled from different components.

What makes lipids hydrophobic?

Nonpolar hydrocarbon chains.

What is a fat (triglyceride) made of?

Glycerol + 3 fatty acids.

What are saturated fatty acids?

No double bonds; solid at room temp; linked to heart disease.

What are unsaturated fatty acids?

Have double bonds (C=C); liquid at room temp; plant-based.

Examples of saturated fats?

Butter, lard.

Examples of unsaturated fats?

Olive oil, corn oil.

What is the main function of fats?

Long-term energy storage.

What other roles do fats play?

Insulation and cushioning of organs.

What are phospholipids made of?

Glycerol, 2 fatty acids (hydrophobic), and a phosphate group (hydrophilic).

How are phospholipids arranged in membranes?

Bilayer with hydrophilic heads out, hydrophobic tails in.

What is the structure of a steroid?

Four fused carbon rings.

Examples of steroids?

Cholesterol, estrogen, testosterone.

What is the function of cholesterol?

Maintains fluidity in animal cell membranes.

What are proteins made of?

Amino acid monomers.

What bonds link amino acids?

Peptide bonds (formed by dehydration synthesis).

What are the four parts of an amino acid?

Central carbon, amino group, carboxyl group, hydrogen, and R group.

What is a protein’s primary structure?

Its sequence of amino acids.

What is a protein’s secondary structure?

Alpha helices and beta pleated sheets (from H-bonds).

What is a protein’s tertiary structure?

3D shape from R group interactions.

What is a protein’s quaternary structure?

When multiple polypeptides combine (e.g., hemoglobin).

What determines a protein’s function?

Its shape.

What can cause a protein to denature?

Heat, pH changes, or other environmental factors.

What happens if a protein changes shape?

It may lose its function (e.g., sickle cell hemoglobin).