AP Biology Unit 1: Chemistry of Life

Vocabulary practice flashcards covering the properties of water, functional groups, and biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids) based on the lecture notes.

Hydrogen Bond

A weak attraction between a highly electronegative atom and a hydrogen atom that is not a true chemical bond, but gives water unique cohesive and thermal properties and stabilizes large biological molecules such as DNA and proteins.

Cohesion

The intermolecular attraction that causes water molecules to be attracted to other water molecules via hydrogen bonding.

Adhesion

The attraction of water molecules to other polar molecules, which helps draw water up from plant roots through capillary action in xylem cells.

Surface Tension

The measure of difficulty to break the surface of liquid water, resulting from hydrogen bonds between surface water molecules.

High Specific Heat

The property where water absorbs significant heat before its temperature measurably increases because hydrogen bonds restrict molecular motion compared to nonpolar substances.

Evaporative Cooling

The decrease in surface temperature that occurs as water evaporates, caused by higher kinetic energy water molecules escaping as gas and leaving cooler molecules behind to aid in temperature regulation and homeostasis.

Ice Density

The physical characteristic where solid ice is approximately $10\%$ less dense than liquid water because reduced kinetic energy allows hydrogen bonds to stabilize with fixed spacing (ice pockets), enabling ice to float and insulate underlying aquatic life.

Nonpolar Covalent Bond

A chemical bond where electrons are shared evenly between atoms, resulting in no charge.

Polar Covalent Bond

A chemical bond between atoms that produces a partial charge ($\delta^+$ and $\delta^-$) across the molecule due to unequal electronegativity.

Dehydration Synthesis

A reaction where an enzyme removes a hydroxyl group ($-OH$) from one monomer and a hydrogen ion ($H^+$) from another monomer to produce a molecule of water and form a covalent bond between the monomers.

Hydrolysis

A chemical reaction in which an enzyme splits water, adding a hydroxyl group to one monomer and a hydrogen ion ($H^+$) to another to break the covalent bond separating the polymer.

Structural Isomers

Molecules that share the same chemical formula but differ in the covalent arrangement or positioning of their atoms (for example, glucose and fructose).

Geometric Isomers

A type of stereoisomer where one part of the molecule's chemical structure is flipped across a fixed bond.

Optical Isomers

Stereoisomers whose molecular structures are non-superimposable mirror images of each other.

Hydroxyl Group

A functional group ($-OH$) that is polar and hydrophilic.

Carboxyl Group

A functional group ($-COOH$) that is polar, hydrophilic, and acts as an acid.

Sulfhydryl Group

A functional group ($-SH$) that is polar and forms covalent disulfide bonds ($S-S$) within proteins.

Amino Group

A functional group ($-NH_2$) that is polar, hydrophilic, behaves as a base, and carries a positive charge at cellular pH.

Methyl Group

A non-polar functional group represented by $-CH_3$.

Phosphate Group

A polar, hydrophilic functional group ($-OPO_4$) that is negatively charged at cellular pH.

Carbonyl - Aldehyde

A polar, hydrophilic carbonyl group ($-CHO$) located at the end of a carbon skeleton, featuring an electronegative oxygen atom bonded to carbon.

Carbonyl - Ketone

A polar, hydrophilic functional group ($R-CO-R'$) containing an internal carbonyl carbon bonded between two hydrocarbon groups.

Monosaccharide

A simple sugar monomer composed of carbon, hydrogen, and oxygen in a $1:2:1$ ratio containing between $3$ and $7$ carbons, which is highly soluble in water and functions as an energy source or structural unit.

Glycosidic Bond

The covalent linkage formed between monosaccharide monomers during a dehydration synthesis reaction.

Starch

A storage polysaccharide formed of $\alpha$-glucose in plants, which can be digested by the enzyme amylase.

Glycogen

A storage polysaccharide formed of $\alpha$-glucose located in animal muscle tissue and liver cells.

Cellulose

A structural polysaccharide made of $\beta$-glucose that forms plant cell walls, which most animals cannot digest because they lack the enzyme cellulase.

Chitin

A structural polysaccharide containing $\beta$-glucose found in the exoskeletons of fungi, insects, and shellfish.

Peptidoglycan

A structural carbohydrate-protein polymer found in the cell walls of bacteria.

Fatty Acids

Simple organic lipid subunits composed of a carboxyl group head attached to a nonpolar hydrocarbon backbone containing $4$ to $36$ carbon atoms.

Saturated Fatty Acid

A fatty acid having only single covalent bonds in its hydrocarbon tail, containing the maximum number of hydrogen atoms per carbon, forming flexible tails that stack into soft solids at room temperature.

Unsaturated Fatty Acid

A fatty acid containing one or more carbon-to-carbon double bonds, which causes bent, less flexible hydrocarbon tails that remain liquid at room temperature.

Ester Bond

The covalent bond connecting a fatty acid's carboxyl group to a hydroxyl group of glycerol in lipids.

Steroids

Hydrophobic lipids characterized by a rigid backbone of $4$ carbon rings and no fatty acid tail, serving as hormonal regulators (such as estrogen and testosterone) and membrane components.

Cholesterol

A four-ring steroid lipid embedded in cell membranes that stabilizes fluidity across temperature variations and acts as a precursor to bile salts and Vitamin D.

Amino Acid

The monomer of proteins, containing a central $\alpha$-carbon bonded to an amino group, a carboxyl group, a hydrogen atom, and one of $20$ variable side chains ($R$ groups).

Peptide Bond

The covalent bond formed between the amino terminus ($-NH_2$) of one amino acid and the carboxyl terminus ($-COOH$) of another during protein synthesis.

Primary Protein Structure

The linear sequence of amino acids in a polypeptide chain connected by covalent peptide bonds, determined directly by genetic code.

Secondary Protein Structure

Local folding and coiling of the polypeptide backbone into elements like $\alpha$-helices and $\beta$-pleated sheets via hydrogen bonding between backbone atoms.

Alpha-Helix

A secondary protein structure stabilized by hydrogen bonds between the $N-H$ group of one amino acid and the $C=O$ group located four residues earlier in the polypeptide chain.

Tertiary Protein Structure

The overall three-dimensional shape of a single polypeptide chain formed through interactions between variable $R$ groups, including hydrophobic clustering, hydrogen bonds, ionic bonds, and disulfide bridges.

Quaternary Protein Structure

The multi-subunit assembly formed when two or more separate polypeptide chains (subunits) interact to assemble a single functional protein complex (such as hemoglobin).

Disulfide Bridge

A covalent bond formed between the sulfhydryl groups of two cysteine residues that stabilizes tertiary protein conformation.

Denaturation

The process wherein extreme shifts in temperature or pH disrupt non-covalent interactions (such as hydrogen bonds), causing a protein to lose its native three-dimensional conformation and biological activity.

Point of Saturation

The state on an enzyme reaction rate curve where all catalytic active sites are occupied by substrate, resulting in a maximum rate of reaction that plateaus into a flat horizontal line.

Nucleotide

The monomer of nucleic acids, consisting of a five-carbon pentose sugar (ribose or deoxyribose), a phosphate group, and a nitrogenous base.

Phosphodiester Bond

The covalent bond that links adjacent nucleotides in DNA and RNA, connecting the $3'$ hydroxyl group of one sugar to the $5'$ phosphate group of the next.

Antiparallel

The directional arrangement in double-stranded DNA where the two complementary nucleotide strands run in opposite orientations (one runs $5' \rightarrow 3'$ and the other runs $3' \rightarrow 5'$).

Pyrimidines

Single-ring nitrogenous bases comprising cytosine (C), thymine (T in DNA), and uracil (U in RNA).

Purines

Double-ring nitrogenous bases comprising adenine (A) and guanine (G).

Adenosine Triphosphate (ATP)

A ribonucleotide derivative composed of an adenine base, a ribose sugar, and three phosphate groups (alpha, beta, and gamma) that serves as the major energy currency of cells.