Biology Lecture Series: Lectures 1 to 8

Vocabulary practice flashcards covering fundamental concepts in biology, biological chemistry, water properties, carbon diversity, macromolecules, proteins, and nucleic acids from Lectures 1 through 8.

Biology

The scientific study of life, derived from the Greek words bios (life) and logos (science).

Eukaryotic Cell

A cell type that is subdivided by internal membranes into various membrane-enclosed organelles, including a nucleus that contains DNA.

Prokaryotic Cell

A cell type that lacks the kinds of membrane-enclosed organelles found in eukaryotic cells and has DNA located without a nucleus.

Reductionism

The approach of reducing complex biological systems to simpler components to make them more manageable to study or to understand the molecular basis of macroscopic processes.

Compound

A substance consisting of two or more elements combined in a fixed ratio that exhibits characteristics different from those of its constituent elements.

Essential Elements

The chemical elements required by life—primarily carbon, hydrogen, oxygen, and nitrogen—which together make up $96\%$ of living matter.

Atomic Number

The number of protons in the nucleus of an atom, which is unique to each chemical element.

Mass Number

The total sum of protons plus neutrons in an atom's nucleus, serving as an approximation of its atomic mass.

Isotopes

Different atomic forms of a given element that have the same number of protons but differ in the number of neutrons in the nucleus.

Valence Electrons

The electrons located in the outermost, or valence shell, of an atom that determine its chemical behavior.

Polar Covalent Bond

A covalent bond formed between atoms of differing electronegativities, resulting in an unequal sharing of electrons and partial electrical charges on the bonded atoms.

Hydrogen Bond

A weak chemical bond that forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom.

Cohesion

An emergent property of water resulting from hydrogen bonding between water molecules that causes them to stick to one another.

Acid

Any chemical substance that increases the hydrogen ion ($H^+$) concentration of a solution.

Base

Any chemical substance that reduces the hydrogen ion ($H^+$) concentration of a solution.

pH Scale

A measurement scale determined by the relative concentration of hydrogen ions in a solution, where acids measure less than $7$ and bases measure greater than $7$.

Vitalism

The disproved idea that organic compounds arise exclusively within living organisms, refuted when organic molecules were synthesized abiotically in laboratory experiments.

Hydrocarbons

Organic molecules consisting entirely of carbon and hydrogen atoms.

Isomers

Molecules that share identical molecular formulas but possess different structural configurations and properties.

Structural Isomers

Isomers that differ in the covalent arrangement of their component atoms.

Geometric Isomers

Isomers that feature identical covalent partnerships but differ in their spatial arrangements around a double bond.

Enantiomers

Isomers that are non-superimposable mirror images of each other due to the presence of an asymmetric carbon atom.

Polymer

A long biological molecule made up of many similar or identical building blocks called monomers connected by covalent bonds.

Monomer

A small repeating structural unit that functions as the building block of a polymer.

Dehydration Reaction

A condensation reaction that joins monomers into a polymer by removing a water molecule to create a new bond.

Hydrolysis

A chemical process that disassembles polymers into individual monomers by breaking covalent bonds through the addition of a water molecule.

Monosaccharides

Simple single sugar units with the general formula $(CH_2O)_n$ that serve as building blocks for carbohydrates.

Cellulose

An unbranched polysaccharide composed of $\beta$ glucose monomers bound by hydrogen bonds that forms the major architectural component of plant cell walls.

Lipids

A diverse collection of hydrophobic biological molecules that do not form strict polymers.

Triacylglycerol

A fat molecule formed by linking three fatty acid chains to a single glycerol molecule via ester linkages.

Phospholipid

A lipid composed of a hydrophilic head group attached to two hydrophobic fatty acid tails, forming the primary structural unit of biological membranes.

Steroids

Lipids characterized by a carbon skeleton composed of four fused rings, such as cholesterol and steroid hormones.

Polypeptide

A polymer constructed from amino acids connected in a specific sequence by peptide bonds.

Peptide Bond

The covalent bond linking the carboxyl group of one amino acid to the amino group of another formed via a dehydration reaction.

Primary Structure

The linear sequence of amino acids in a polypeptide chain held together by covalent peptide bonds.

Secondary Structure

The localized, repetitive coiling or folding of the polypeptide backbone caused by hydrogen bonding between backbone atoms, including $\alpha$ helices and $\beta$ pleated sheets.

Alpha Helix

A delicate helical secondary structure formed by hydrogen bonding between every fourth amino acid in a polypeptide backbone.

Beta Pleated Sheet

A secondary structure consisting of extended $\beta$ strands lying side-by-side held together by hydrogen bonds between parallel or antiparallel regions of the backbone.

Tertiary Structure

The overall three-dimensional shape of a polypeptide chain resulting from hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges among amino acid side chains ($R$ groups).

Quaternary Structure

The overall protein architecture resulting from the association and aggregation of two or more individual polypeptide subunits.

Sickle-Cell Disease

A genetic disease caused by a single amino acid substitution in the primary structure of hemoglobin (valine replacing glutamic acid), causing abnormal hemoglobin molecules to aggregate and distort red blood cells.

Nucleic Acids

Biological macromolecules, including DNA and RNA, that store, transmit, and express hereditary genetic information.

Polynucleotide

A polymer consisting of nucleotide monomers joined in a chain by phosphodiester bonds.

Nucleotide

The fundamental monomer of nucleic acids, consisting of a pentose sugar, a nitrogenous base, and one or more phosphate groups.

Pyrimidines

Nitrogenous bases consisting of a single six-membered carbon-nitrogen ring, including cytosine, thymine (in DNA), and uracil (in RNA).

Purines

Nitrogenous bases featuring a six-membered ring fused to a five-membered ring, including adenine and guanine.

Double Helix

The structural conformation of cellular DNA, consisting of two antiparallel polynucleotide strands spiraling around an imaginary axis.