Comprehensive Biology Review: Biochemistry, Energetics, Genetics, Evolution, and Ecology

Comprehensive vocabulary flashcards covering foundational biology concepts: biomolecules, cellular energetics, cell signaling, cell cycle control, genetics, molecular biology, evolution, and ecology.

Ionic Bond

A chemical bond formed when electrons are transferred between atoms, typically occurring between a metal and a nonmetal.

Covalent Bond

A chemical bond formed when electrons are shared between nonmetal atoms.

Polar Covalent Bond

A covalent bond where electrons are shared unequally between atoms due to differences in electronegativity, creating a negative pole at the atom with higher electronegativity and a positive pole at the atom with lower electronegativity.

Hydrogen Bond

A weak intermolecular attraction between a slightly positive hydrogen atom in one molecule and a slightly negative atom in another molecule.

High Specific Heat

A property of water requiring a large amount of energy to increase its temperature, because the thermal energy must first be used to break intermolecular hydrogen bonds.

Cohesion

The property of water molecules sticking to each other via hydrogen bonds, resulting in high surface tension.

Adhesion

The property of water molecules sticking to other polar surfaces, allowing water to rise against gravity in narrow tubes.

Hydroxyl Group

A polar, hydrophilic functional group represented structurally as $-OH$.

Carboxyl Group

A polar, hydrophilic, weak-acid functional group represented structurally as $-COOH$.

Amino Group

A polar, hydrophilic, weak-base functional group represented structurally as $-NH_2$.

Phosphate Group

A polar, hydrophilic, acidic functional group containing phosphorus bound to four oxygen atoms, represented as $-PO_4^{2-}$.

Methyl Group

A nonpolar, hydrophobic functional group consisting of a carbon bonded to three hydrogen atoms, represented as $-CH_3$.

Hydrolysis

A chemical reaction that breaks down polymers into smaller units by the addition of a water molecule ($H_2O$).

Dehydration Synthesis

A chemical reaction that joins monomers together to form larger polymers through the removal of a water molecule ($H_2O$).

Phospholipid

The main component of cell membranes, composed of two fatty acids, one glycerol, and one phosphate group, yielding an amphipathic structure with a polar hydrophilic head and nonpolar hydrophobic tails.

Saturated Fatty Acid

A fatty acid chain with only single bonds between carbon atoms, containing maximum hydrogens; it forms a straight molecule and is solid at room temperature.

Unsaturated Fatty Acid

A fatty acid chain containing one or more double bonds between carbon atoms, carrying fewer hydrogens; this causes bends in the molecule and keeps it liquid at room temperature.

Primary Protein Structure

The linear, unfolded sequence of amino acids linked together by peptide bonds.

Secondary Protein Structure

Local recurring structures within a polypeptide chain, specifically alpha helices or beta-pleated sheets, stabilized by hydrogen bonds along the polypeptide backbone.

Tertiary Protein Structure

The overall three-dimensional folding of a single polypeptide chain, stabilized by hydrogen bonds, ionic bonds, hydrophobic interactions, covalent bonds, and disulfide bridges.

Quaternary Protein Structure

The structural conformation formed by the aggregation and interaction of more than one tertiary polypeptide subunit together.

Substrate-Level Phosphorylation

The direct synthesis of ATP by transferring a phosphate group to ADP ($\text{ADP} + P_i + 7300\,\text{cal} \rightarrow \text{ATP}$) without the requirement of an electron transport system.

Oxidative Phosphorylation

The synthesis of ATP driven by electron transfers through an electron transport system (ETS) and the resulting proton gradient across a membrane.

Reduction

The gain of electrons or hydrogen atoms ($H^+ + e^-$), characterized by an increase in $C\text{-}H$ bonds or a decrease in $C\text{-}O$ bonds (GER).

Oxidation

The loss of electrons or hydrogen atoms, characterized by a decrease in $C\text{-}H$ bonds or an increase in $C\text{-}O$ bonds (LEO).

Glycolysis

A cytosolic metabolic pathway in all organisms that breaks down one $6C$ glucose into two $3C$ pyruvate molecules, yielding a net of $2\,\text{ATP}$ and reducing $2\,\text{NAD}^+$.

Chemiosmosis

The movement of $H^+$ ions from an area of high proton concentration to low proton concentration across a membrane through ATP synthase, driving the phosphorylation of ADP to ATP.

Photolysis

The light-catalyzed breakdown of water ($4H_2O \rightarrow 4H^+ + 4OH^-$) in the non-cyclic light reaction of photosynthesis that supplies replacement electrons to Photosystem II ($\text{PS-2}$) and releases oxygen gas ($O_2$).

Calvin Cycle

The light-independent pathway occurring in the chloroplast stroma where $CO_2$ is fixed by the Rubisco enzyme and converted into glucose using ATP and $\text{NADPH}_2$ produced in light-dependent reactions.

Paracrine Signaling

A form of local cell communication in which cells secrete regulatory substances (such as growth factors) into the extracellular fluid to influence nearby target cells.

Endocrine Signaling

Long-distance hormonal communication wherein endocrine glands secrete hormones into the bloodstream to reach distant target organs bearing corresponding receptors.

Second Messenger

A small, nonprotein, water-soluble molecule or ion (such as $\text{cAMP}$, $Ca^{2+}$, $\text{IP}_3$, or DAG) that relays signals inside the cell from an activated membrane receptor.

Receptor Tyrosine Kinase (RTK)

A transmembrane enzyme-linked receptor that forms a dimer upon ligand binding and activates via autophosphorylation to initiate multiple intracellular signaling cascades.

Ced-9 / Ced-4 / Ced-3 Apoptosis Pathway

A programmed cell death pathway in which active Ced-9 normally inhibits Ced-4; death signaling inactivates Ced-9, freeing Ced-4 to activate Ced-3 and trigger a cascade of nucleases and proteases.

Cyclin-Dependent Kinases (CdKs)

Enzymes that phosphorylate specific target proteins to regulate cell cycle transitions; they remain catalytically inactive until bound by their corresponding cyclin partners.

Anchorage-Dependence

The requirement that most normal animal cells must be attached to an external substratum or surface in order to divide.

Density-Dependent Inhibition

The regulatory phenomenon where normal cells stop dividing once they form a single confluent monolayer and the cell density reaches a specific threshold.

Metastasis

The migration and spread of malignant cancer cells away from their primary site of origin to invade other tissues in the body.

Angiogenesis

The physiological process through which cancer cells stimulate the formation and growth of new blood vessels to supply nutrients to tumors.

Nondisjunction

An error during meiosis wherein homologous chromosomes fail to separate during Anaphase I, or sister chromatids fail to separate during Anaphase II, yielding abnormal gametes with $n+1$ or $n-1$ chromosomes.

Crossing Over

The reciprocal exchange of genetic material between non-sister chromatids of homologous chromosomes during Prophase I of meiosis, creating recombinant chromosomes.

Incomplete Dominance

An inheritance pattern in which the dominant allele does not completely mask the recessive allele, resulting in a blended, intermediate heterozygous phenotype.

Codominance

An inheritance pattern wherein both distinct alleles are fully, simultaneously, and independently expressed in heterozygous individuals (such as AB blood type or roan coat color).

Pleiotropy

A genetic condition in which a single gene locus influences multiple distinct phenotypic traits.

Epistasis

A genetic interaction where the phenotypic expression of one gene masks, alters, or directly influences the phenotypic expression of a second independent gene.

Avery, MacLeod, and McCarty Experiment

An experimental protocol demonstrating that DNA is the transforming principle, confirmed because the transformation of living R-cells into pathogenic S-cells was prevented only when DNase destroyed the DNA.

Semiconservative Replication

The mechanism of DNA synthesis demonstrated by Meselson and Stahl, where each replicated double helix contains one conserved original parental strand and one newly synthesized complementary strand.

Okazaki Fragments

Short, discontinuously synthesized segments of DNA formed on the lagging strand during replication, which are subsequently joined into a continuous strand by DNA ligase.

Telomeres

Repetitive non-coding nucleotide sequences capping the ends of eukaryotic chromosomes that buffer and protect essential coding genes from progressive shortening over repeated cell divisions.

Alternative Splicing

A post-transcriptional process in which different combinations of exons from the same pre-mRNA are spliced together, producing multiple distinct mature mRNAs and protein isoforms from a single gene.

Operon

A functional unit of genomic DNA in prokaryotes comprising a promoter, an operator, and a regulated cluster of structural genes that function together under coordinate control.

Stabilizing Selection

A type of natural selection that favors the intermediate or average phenotype in a population while selecting against extreme variations.

Directional Selection

A mode of natural selection that favors phenotypes at one extreme of the phenotypic spectrum, causing allele frequencies to systematically shift in that direction over time.

Diversifying Selection

A type of natural selection that simultaneously favors individuals at both extreme phenotypic ends over intermediate or average phenotypes.

Allopatric Speciation

The formation of new biological species occurring when ancestral populations become geographically separated by a physical barrier that prevents gene flow.

Sympatric Speciation

Speciation that occurs in populations that occupy the same geographic region without physical separation, driven by polyploidy, habitat divergence, or balanced polymorphism.

Adaptive Radiation

The rapid diversification of an ancestral species into a variety of different ecological forms and niches when introduced to novel environmental conditions.

Homologous Structures

Anatomical structures found across different species that share a common ancestral origin, even if they have evolved divergent appearances or functions.

Analogous Structures

Body parts in unrelated organisms that perform similar biological functions and evolved independently through convergent evolution, lacking a common ancestral design.

Carrying Capacity (K)

The maximum population size of a species that a specific ecosystem can sustainably support given available resources.

Competitive Exclusion Principle

Gause's ecological principle stating that two competing species utilizing the identical niche cannot sustainably coexist; one will inevitably outcompete and displace the other.

Resource Partitioning

The division of limited environmental resources by coexisting species through specialized behavioral, temporal, or spatial niche shifts to minimize direct interspecific competition.

Keystone Species

A species that exerts an exceptionally large and disproportionate influence on community structure, trophic dynamics, and overall biodiversity relative to its abundance.

Biomagnification

The progressive bioaccumulation and increase in concentration of environmental toxins at sequentially higher trophic levels throughout a food web.

Eutrophication

The excessive enrichment of aquatic ecosystems with nutrients (especially nitrogen and phosphorus), triggering explosive algal blooms whose decomposition depletes dissolved oxygen and creates hypoxic dead zones.