Chapter 3: The Organic Molecules of Life

Practice flashcards covering key concepts from Chapter 3: The Organic Molecules of Life, including organic vs inorganic molecules, isomers, functional groups, carbohydrates, lipids, proteins, nucleic acids, and the relationship between DNA and proteins.

What elements do organic molecules contain?

Carbon and hydrogen.

What distinguishes organic molecules from inorganic ones?

Organic molecules contain carbon and hydrogen; inorganic molecules do not.

What is an isomer?

Two molecules with the same molecular formula but different arrangements of atoms.

What is a constitutional (structural) isomer?

An isomer with the same formula but different connectivity of atoms.

What is a stereoisomer?

An isomer with the same connectivity but different spatial arrangement.

What are enantiomers?

Non-superimposable mirror-image stereoisomers.

What are diastereomers?

Stereoisomers that are not mirror images and differ at one or more stereocenters.

What is a conformer?

A spatial arrangement that can be interconverted by rotation about a single bond.

What are cis–trans isomers?

Stereoisomers around a double bond where substituents are on the same side (cis) or opposite sides (trans).

What functional group is -OH and where is it common?

Hydroxyl; found in alcohols and sugars.

What functional group is -COOH and where is it found?

Carboxyl; found in fatty acids and amino acids.

What functional group is -NH2 and where is it found?

Amino group; found in amino acids and proteins.

What functional group is -SH and where is it found?

Sulfhydryl; found in cysteine and can form disulfide bonds.

What functional group is -PO4H2 and where is it found?

Phosphate; found in ATP and nucleic acids.

What are monosaccharides?

Single sugar molecules; 3–7 carbon backbone; include glucose, fructose, galactose; ribose and deoxyribose are in RNA and DNA.

Which monosaccharides are hexoses and what are common examples?

Hexoses are six-carbon monosaccharides; examples include glucose, fructose, and galactose.

What are ribose and deoxyribose used for?

Ribose is the sugar in RNA; deoxyribose is the sugar in DNA.

What are disaccharides?

Two monosaccharides bonded together; examples: maltose (glucose+glucose), sucrose (glucose+fructose), lactose (galactose+glucose).

What are polysaccharides?

Polymers of monosaccharides with storage or structural roles (starch in plants, glycogen in animals, cellulose in plant cell walls, chitin in exoskeletons).

What are lipids generally like in water?

Insoluble in water; long nonpolar hydrocarbon chains; diverse structures and functions.

What are fats and oils used for?

Long-term energy storage; fats and oils; oils can waterproof skin, hair, and feathers.

What is a triglyceride?

A glycerol molecule bonded to three fatty acids; formed by dehydration synthesis; energy-dense storage molecule.

What is a fatty acid? Distinguish saturated vs unsaturated and trans fats.

A long hydrocarbon chain with a carboxyl group at one end; saturated has no double bonds; unsaturated has double bonds; trans fats have trans double-bond geometry.

What is a phospholipid and where is it found?

A lipid with a polar phosphate head and nonpolar fatty acid tails; forms the lipid bilayer of cell membranes.

What are steroids?

Lipids with four fused rings derived from cholesterol; differ by functional groups; examples: cholesterol, testosterone, estrogen.

What are the major classes of proteins and what do they do?

Proteins perform support, metabolism, transport, defense, regulation, and motion; built from amino acid monomers.

What is a peptide?

Two or more amino acids covalently linked by a peptide bond formed by dehydration synthesis.

What is a polypeptide?

A chain of many amino acids joined by peptide bonds.

How is a protein's final 3D shape determined?

By its amino acid sequence and interactions among R groups; structure determines function.

What are the four levels of protein structure?

Primary (amino acid sequence), Secondary (alpha helix and beta pleated sheet), Tertiary (3D shape), Quaternary (more than one polypeptide).

What are nucleic acids and what are their monomers?

DNA and RNA; polymers of nucleotides; nucleotide composed of a phosphate, a five-carbon sugar, and a nitrogen-containing base.

What bases are in DNA and RNA?

DNA: A, T, C, G; RNA: A, U, C, G (T is replaced by U in RNA).

What is the structure of DNA?

Double helix; complementary base pairing A–T and C–G; sugar–phosphate backbone.

What is the structure of RNA?

Single-stranded; ribose sugar; bases A, G, C, U; backbone.

How are DNA sequence and protein sequence related?

DNA sequence determines amino acid sequence in a protein; sequence of amino acids determines protein structure and function; small DNA changes can cause large changes in proteins.

What is sickle-cell disease and its molecular cause?

A single amino acid substitution (valine replaces glutamate) in the beta chain of hemoglobin; causes red blood cells to become sickle-shaped.

What is dehydration synthesis?

Joining monomers by removing a water molecule to form a polymer.

What is hydrolysis?

Breaking bonds in polymers by adding water; OH attaches to one monomer and H to the other.

What are the storage and structural polysaccharide examples mentioned?

Starch (plants storage), glycogen (animals storage), cellulose (plant cell walls), chitin (exoskeletons of crustaceans and insects).