Unit I: Chemistry of Life - Water, Macromolecules, and Nucleic Acids (AP Biology)

A set of practice flashcards covering key concepts from water chemistry, macromolecules, and nucleic acids as taught in Unit I of AP Biology.

What are the four emergent properties of water that support life?

Cohesion and adhesion, temperature moderation, expansion upon freezing, and water’s role as a versatile solvent.

Why is water a polar molecule and how does this enable hydrogen bonding?

Water has an uneven distribution of charge with partial negative on oxygen and partial positive on hydrogens, allowing hydrogen bonds between molecules.

What is a hydration shell?

A layer of water molecules surrounding dissolved ions in solution, stabilizing them.

What is the difference between hydrophilic and hydrophobic substances?

Hydrophilic substances dissolve in water; hydrophobic substances do not dissolve in water due to nonpolar nature.

What are the four major biological macromolecules?

Carbohydrates, proteins, lipids, and nucleic acids.

What is dehydration synthesis?

A reaction that links monomers by removing a hydrogen from one and a hydroxyl from another, forming a covalent bond and water.

What is hydrolysis?

The breakdown of polymers by adding water to break covalent bonds.

Which macromolecules are polymers?

Carbohydrates, proteins, and nucleic acids are polymers; lipids are not.

What determines the properties of a biological polymer?

The monomer sequence and the type of covalent bonds connecting monomers.

What are the monomers of nucleic acids?

Nucleotides, consisting of a phosphate group, a sugar, and a nitrogenous base.

What are the two types of nucleic acids and their sugar bases?

DNA uses deoxyribose and bases A, T, C, G; RNA uses ribose and bases A, U, C, G.

How do A-T and C-G pair in DNA?

A pairs with T via two hydrogen bonds; C pairs with G via three hydrogen bonds.

What is the directionality of nucleic acid synthesis?

Nucleic acids grow in the 5′ to 3′ direction; synthesis uses the 3′ end for new nucleotide addition.

What are the primary structural levels of proteins?

Primary (amino acid sequence), Secondary (α-helix and β-pleated sheets), Tertiary (3D folding), Quaternary (multiple polypeptides).

Name common protein functions with examples.

Enzymatic (digestive enzymes), Defensive (antibodies), Storage (casein), Transport (hemoglobin), Hormonal (insulin), Receptor (membrane receptors), Contractile/Motor (actin/myosin), Structural (collagen, keratin).

What is dehydration synthesis in proteins?

Amino acid C-terminus loses OH and N-terminus loses H to form a peptide bond, creating a polypeptide (primary structure).

What are the monomers of carbohydrates and how are they linked?

Monosaccharides linked by covalent glycosidic bonds; polymers (polysaccharides) form energy storage or structural materials.

Name storage and structural carbohydrates and examples.

Storage: starch (plants), glycogen (animals). Structural: cellulose (plants), chitin (arthropods).

What is the difference between saturated and unsaturated fatty acids?

Saturated: single bonds, linear; Unsaturated: one or more double bonds, kinked structure.

What is the structure of a phospholipid and what does it form?

Glycerol + two fatty acids + a phosphate head; polar head, nonpolar tails; in water, form a lipid bilayer with heads outward and tails inward.

What is a steroid and give an example and function?

Steroids are nonpolar lipids with four fused rings; cholesterol modulates membranes and serves as a hormone precursor.

What are the monomeric units of proteins and how are they categorized?

Amino acids; R groups determine polarity/charge; proteins have N-terminus and C-terminus; directionality.

What stabilizes a protein’s secondary structure?

Hydrogen bonds between the backbone carbonyl and amide groups (within the polypeptide).

What are the functions of nucleic acids beyond encoding proteins?

mRNA serves as a template for protein synthesis; tRNA transfers amino acids; rRNA forms ribosomes.

What is chitin and where is it found?

A structural carbohydrate in arthropod exoskeletons; used to make biodegradable surgical thread.

What is a gene and how does it relate to DNA?

A gene is a section of DNA that encodes a functional product; DNA is the polymer of nucleotides encoding genetic information.

Which elements are present in all four macromolecules and which are additional in certain ones?

All have C, H, O; N is in proteins and nucleic acids; P is in nucleic acids and some lipids.

How do monosaccharides vary and affect function?

Different glycosidic linkages and branching patterns (linear vs branched) affect storage versus structural roles.

What are the differences between DNA and RNA in terms of structure and function?

DNA is typically double-stranded with deoxyribose and thymine; RNA is usually single-stranded with ribose and uracil; DNA stores genetic information, RNA participates in protein synthesis and other roles.

What is the concept of a hydration shell in solution chemistry?

Water molecules arranged around an ion in solution, stabilizing the ion and facilitating transport.