AP BIO UNIT ONE TEST

What is the structure of water?

Water (H₂O) has 2 hydrogen atoms and 1 oxygen atom.

What is polarity in water?

Polarity is the unequal distribution of electrical charge, with oxygen being slightly negative (δ−) and hydrogen slightly positive (δ+).

What type of bonds exist within a water molecule?

The bonds inside a water molecule are polar covalent bonds.

What is a hydrogen bond?

A hydrogen bond forms between the slightly positive hydrogen of one water molecule and the slightly negative oxygen of another.

What are the properties of water that arise from hydrogen bonding?

1. Cohesion 2. Adhesion 3. Surface tension 4. Capillary action 5. High specific heat capacity 6. High heat of vaporization 7. High solvency 8. Density.

What is cohesion?

Cohesion is the tendency of water molecules to stick to other water molecules due to hydrogen bonding.

What is adhesion?

Adhesion is the tendency of water to stick to other substances.

How does surface tension benefit certain organisms?

Surface tension allows organisms like the basilisk lizard to move across water.

What is capillary action?

Capillary action is the movement of water through narrow spaces due to cohesion and adhesion.

What does high specific heat capacity mean for water?

Water requires a lot of energy to change its temperature, helping organisms maintain a stable body temperature.

What is high heat of vaporization in relation to water?

A lot of energy is needed to turn liquid water into gas, producing evaporative cooling.

Why is water known as a universal solvent?

Because water is polar, it can dissolve many ionic and polar substances.

What is unique about the density of ice compared to liquid water?

Ice is less dense than liquid water, allowing it to float.

What does the Law of Conservation of Energy state?

Energy cannot be created or destroyed; it can only be transformed.

What are the main elements required for living systems?

Carbon (C), Nitrogen (N), and Phosphorus (P).

Why is carbon considered the backbone of biological molecules?

Carbon can bond with other carbon atoms to create carbon skeletons, forming large and complex molecules.

What are the four major biological macromolecules?

Carbohydrates, Lipids, Proteins, and Nucleic acids.

What is dehydration synthesis?

A process that builds larger molecules by joining monomers together and removing water.

What is hydrolysis?

A process that breaks larger molecules apart by adding water.

What are monosaccharides?

Monomers of carbohydrates, also called simple sugars, like glucose and fructose.

What are polysaccharides?

Polymers made of many monosaccharides connected by covalent bonds.

What are the functions of carbohydrates in biological systems?

Energy storage and structural support.

What distinguishes saturated fatty acids from unsaturated fatty acids?

Saturated fatty acids have only single bonds between carbon atoms, while unsaturated fatty acids have at least one double bond.

What are triglycerides?

Lipids made of glycerol and three fatty acids, primarily used for energy storage.

What is the function of phospholipids?

Phospholipids form the bilayer structure of cell membranes.

What is the primary structure of a protein?

The sequence of amino acids in a polypeptide chain.

What is denaturation?

The disruption of a protein's shape and function due to changes in the environment.

What is the relationship between amino acid sequence and protein function?

Amino acid sequence determines protein shape, which in turn determines protein function.

Covalent bond

A strong intramolecular chemical attraction formed when two nonmetal atoms share one or more pairs of valence electrons to achieve stable, filled outer electron shells.

Hydrogen bond

A weak intermolecular electrostatic attraction occurring between a partially positive hydrogen atom ($\delta^+$) covalently bound to a highly electronegative atom and a neighboring electronegative atom ($\delta^-$).

Polarity

The uneven distribution of electrical charge across a molecule caused by differences in electronegativity among bonded atoms, resulting in distinct partial positive and partial negative poles.

Cohesion

The intermolecular attraction that causes identical polar molecules—such as water—to bind to one another via force networks like hydrogen bonding.

Adhesion

The attractive force causing polar or charged liquid molecules to cling to different, non-self substances or surfaces.

Surface tension

The measure of force required to stretch or break the surface layer of a liquid, produced by cohesive intermolecular hydrogen bonding among surface molecules.

Solvency

The chemical property of a fluid that enables it to dissolve hydrophilic solutes by surrounding individual ions or polar molecules with hydration shells.

Specific heat capacity

The amount of thermal energy that must be absorbed or lost for $1\,g$ of a substance to change its overall temperature by 1\,\text{^\circ C}.

Heat of vaporization

The quantity of heat energy required to transform a unit mass of a liquid into a gas at constant pressure and temperature.

Capillary action

The process where liquid spontaneously ascends through narrow spaces or tubes as a result of adhesive forces between the liquid and tube walls working alongside internal cohesive forces.

Law of Conservation of Energy

A fundamental physical principle dictating that the total energy within an isolated system remains constant; energy cannot be created or destroyed, only converted from one form to another.

Living systems

Complex, highly organized biological units that continuously import matter and energy from their environment to maintain homeostasis, drive metabolic work, and sustain life processes.

Biological macromolecules

Large organic polymers—specifically carbohydrates, lipids, proteins, and nucleic acids—assembled from monomer units through covalent bonding to perform vital cellular functions.

Chemical bond

An attractive force formed between atoms or ions through electron sharing or transfer that holds them together in stable chemical compounds and stores potential energy.

Carbon skeleton

The structural backbone of carbon atoms linked together in chains, branches, or rings that forms the foundational architecture of organic biological compounds.

Exchange of matter

The dynamic process through which organisms absorb necessary chemical elements and nutrients from their surroundings and eliminate metabolic wastes back into the ecosystem.

Amino acid

The monomer subunit of proteins, consisting of a central carbon atom covalently bonded to an amino group ($-NH_2$), a carboxyl group ($-COOH$), a hydrogen atom, and a unique functional side chain ($R$ group).

R group (Side chain)

The variable portion of an amino acid that defines its chemical behavior—such as polar, nonpolar, acidic, or basic—and dictates the three-dimensional folding pattern of a polypeptide.

Peptide bond

The covalent bond established between the carboxyl group ($-COOH$) of one amino acid and the amino group ($-NH_2$) of another through a dehydration synthesis reaction.

Polypeptide

An unbranched polymer chain consisting of amino acids covalently linked together by sequential peptide bonds.

Primary structure of a protein

The linear sequence of amino acids within a polypeptide chain, strictly determined by genetic coding in nucleic acids.

Secondary structure of a protein

Repetitive localized spatial arrangements—namely $\alpha$-helices and $\beta$-pleated sheets—formed by hydrogen bonding between atoms along the polypeptide backbone.

Tertiary structure of a protein

The overall three-dimensional folding conformation of a single polypeptide chain, driven by interactions among variable $R$ groups including hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.

Quaternary structure of a protein

The complex three-dimensional arrangement resulting from the interaction and assembly of two or more distinct polypeptide subunits into a single functional protein.

Denaturation

The structural unfolding of a protein's native three-dimensional conformation caused by external stressors like elevated temperature or extreme pH, leading to a complete loss of biological function.

Lipid

A diverse group of nonpolar, hydrophobic biomolecules constructed predominantly of carbon and hydrogen hydrocarbons, including fats, oils, phospholipids, and steroids.

Hydrophobic

The property of nonpolar molecules that causes them to be insoluble in water and repel polar solvents due to an inability to form favorable interactions such as hydrogen bonds.

Fatty acid

A structural component of many lipids, consisting of an unbranched hydrocarbon chain attached to a terminal polar carboxyl functional group ($-COOH$).

Saturated fatty acid

A fatty acid hydrocarbon chain containing only single covalent bonds between carbon atoms ($C-C$), maximizing hydrogen content and resulting in a straight molecular shape that packs tightly at room temperature.

Unsaturated fatty acid

A fatty acid hydrocarbon chain containing one or more double covalent bonds between carbon atoms ($C=C$), reducing bound hydrogen atoms and creating bends that prevent dense molecular packing.

Triglyceride

A lipid macromolecule composed of three fatty acid chains covalently linked to a single glycerol molecule via ester bonds, serving primarily as long-term energy storage.

Phospholipid

An amphipathic lipid featuring a hydrophilic phosphate head and two hydrophobic fatty acid tails, which spontaneously forms cellular membranes in aqueous environments.

Steroid

A lipid characterized by a structural backbone of four interconnected carbon rings, functioning as signaling molecules, hormones, and structural membrane regulators.

Cholesterol

A crucial animal cell membrane steroid that buffers membrane fluidity across varying temperatures, preventing excessive fluid dynamics at warm temperatures and solidification at cold temperatures.

Lipid bilayer

A double-layered sheet of phospholipids where hydrophobic tails face inward away from water while hydrophilic phosphate heads face outward toward aqueous cellular environments.

Kink (in fatty acids)

A physical bend introduced into an unsaturated fatty acid chain by a carbon-carbon double bond ($C=C$), which increases molecular spacing and enhances membrane fluidity.

Thermal insulation

A physiological adaptation provided by specialized adipose tissue containing stored lipids, which minimizes heat loss and protects internal core body temperatures in homeothermic animals.