Comprehensive Biology Review

Vocabulary practice flashcards covering fundamental concepts across biology, cellular reproduction, genetics, microbiology, and immunology.

Taxonomy

The classification of living organisms into different groupings at different levels based on similar characteristics and DNA, ordered from broadest to narrowest: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species.

Scientific Method

A cyclical or recursive process of inquiry that involves identifying a problem or posing a question, formulating a hypothesis, conducting experiments or tests, observing results, and drawing conclusions.

Polar Molecule (Water)

A molecule ($\text{H}_2\text{O}$) where two hydrogen atoms bond covalently to an oxygen atom at a $105^\bullet$ angle, creating an asymmetrical charge distribution with a positive charge on the hydrogen side and a negative charge on the oxygen side.

Specific Heat of Water

The amount of heat required to raise the temperature of a given amount of water by one degree, equal to $1\,\text{cal}/(\text{g }^\circ\text{C})$; its high value is due to the heat absorbed or released when hydrogen bonds break or form.

Density Changes in Water

The property where water reaches its maximum density as a liquid at $4^\circ\text{C}$, expanding as it cools below that point and organizing at $0^\circ\text{C}$ into a crystalline structure held by hydrogen bonding, making ice less dense than liquid water.

Cohesion-Tension Theory

The theory explaining water transport from plant roots to uppermost leaves, stating that cohesive forces among hydrogen-bonded water molecules create a continuous tension that pulls water upward as molecules exit leaf pores.

Surface Tension

The property of a liquid caused by inward-directed cohesive forces on surface molecules without an opposing external force, causing the surface to contract and behave like a stretched elastic membrane.

Homeostasis

The regulation of internal chemistry to maintain a constant internal environment, controlled through negative- or positive-feedback loops consisting of receptors, an integrator, and effectors.

Negative-Feedback Mechanism

A control mechanism that provides a decrease in response with an increase in stimulus, thereby inhibiting the stimulus and decreasing the overall response.

Positive-Feedback Mechanism

A control mechanism that provides an increase in response with an increase in stimulus, which in turn amplifies the stimulus and increases the response.

Nucleus

The defining eukaryotic organelle that regulates DNA and contains chromosomes, chromatin, nucleoplasm, a nucleolus, nuclear pores, and a lipid bilayer nuclear envelope.

Nucleolus

A small, round, non-membrane-bound structure within the nucleus that consists of protein, is involved in protein synthesis, and synthesizes and stores RNA.

Ribosomes

Cellular structures making up roughly one quarter of the cell that synthesize proteins from amino acids; they can be mobile in the cytoplasm or embedded in the rough endoplasmic reticulum.

Endoplasmic Reticulum

A tubular transport network extending from the nuclear membrane through the cytoplasm to the cell membrane, occurring as rough (studded with ribosomes) or smooth (lacking ribosomes).

Golgi Complex (Golgi Apparatus)

A stack of membranous layers located near the nucleus that synthesizes and packages materials, such as proteins, for transport out of the cell.

Lysosomes

Organelles that digest proteins, lipids, and carbohydrates, and transport undigested substances to the cell membrane for removal.

Mitochondria

Organelles containing their own DNA that generate ATP, regulate cell growth and death, and supply cellular energy in eukaryotic cells.

Selective Permeability

The characteristic of the phospholipid bilayer that allows only certain substances to pass based on molecular size, charge, and lipid solubility; small, uncharged, or lipid-soluble molecules cross most easily.

Passive Transport

The spontaneous net movement of substances across a cell membrane down their concentration gradient without cellular energy input, resulting in an increase in entropy (e.g., simple diffusion, osmosis, facilitated diffusion).

Facilitated Diffusion

A form of passive transport where large, polar, or charged substances are shielded from the hydrophobic interior of the cell membrane and transported down their concentration gradients by channel or carrier proteins.

Primary Active Transport

A membrane transport process where solute pumping against a concentration gradient is directly coupled to the hydrolysis of ATP, inducing a conformational change in the carrier protein.

Secondary Active Transport

A form of active transport that relies on an electrochemical gradient previously established by ATP hydrolysis to drive the active transport of a second solute via symport or antiport.

Glycolysis

An enzyme-controlled anaerobic catabolic pathway in the cytoplasm that breaks down one glucose molecule into two pyruvic acid molecules, yielding a net gain of $2\,\text{ATP}$ and $2\,\text{NADH}$.

Krebs Cycle

An aerobic catabolic pathway (citric acid or TCA cycle) in cellular respiration that oxidizes acetyl CoA derived from pyruvate into carbon dioxide, water, ATP, and NADH.

Electron Transport Chain

A series of oxidoreductive enzymes and coenzymes in the inner mitochondrial membrane that transfer electrons to a final acceptor ($\text{O}_2$ in aerobic respiration) while pumping protons across the membrane to drive ATP synthesis.

Photorespiration

A wasteful process occurring in photosynthetic organisms when the enzyme rubisco binds oxygen instead of atmospheric carbon dioxide, consuming energy and reducing sugar synthesis.

C4 Photosynthesis

A photosynthetic adaptation that minimizes photorespiration by using PEP carboxylase in mesophyll cells to fix carbon dioxide into oxaloacetate, which is converted to malate and transferred to bundle sheath cells where rubisco operates.

Crassulacean Acid Metabolism (CAM)

A temporal adaptation to arid conditions where leaf stomata open at night to fix carbon dioxide into malate via PEP carboxylase, storing it in vacuoles until daytime when it is decarboxylated inside chloroplasts for the Calvin cycle.

Cell Differentiation

The process driven by gene regulation in which a less-specialized cell transforms into a more-specialized cell type, such as during gastrulation when cells form ectoderm, mesoderm, and endoderm.

Mitosis

A form of eukaryotic cell division that duplicates a parent cell into two genetically identical daughter cells through prophase, metaphase, anaphase, telophase, and cytokinesis.

Meiosis

A two-stage specialized cell division in gametes that involves crossing over and reduction division, resulting in four genetically distinct haploid daughter cells containing half the parent's genetic material.

Purines and Pyrimidines

The two structural classes of nitrogenous bases: pyrimidines (cytosine, thymine, uracil) feature a single six-sided ring, while purines (adenine, guanine) consist of a six-sided ring fused to a five-sided ring.

Codon

A sequence of three nucleotides on messenger RNA that codes for a specific amino acid; there are $64$ codons for $20$ amino acids, including the start codon AUG and stop codons UAA, UGA, and UAG.

Helicase

The enzyme that initiates DNA replication by deforming hydrogen bonds between base pairs to unwind and separate the two strands, beginning at adenine-thymine-rich origins of replication.

Transcription

The cellular process in which RNA polymerase copies a specific unwound segment of DNA into a complementary strand of RNA.

Translation

The process in which cytoplasmic ribosomes and transfer RNA (tRNA) read messenger RNA transcripts to assemble amino acids into polypeptides.

Mendel's Law of Segregation

Mendel's first law of inheritance, which states that an organism possesses two alleles for each gene, and each parent contributes half of the total alleles to its offspring.

Mendel's Law of Independent Assortment

Mendel's second law, which states that alleles for different traits are passed to offspring independently and randomly, except when traits are genetically linked.

Co-Dominance

A non-Mendelian inheritance pattern where both alleles for a trait are fully and simultaneously expressed in the phenotype, as seen in the human ABO blood group system or red-and-white hair coats in cattle.

Incomplete Dominance

A non-Mendelian inheritance pattern where neither allele is fully dominant, resulting in a heterozygous phenotype that is an intermediate blend of both alleles (e.g., pink snapdragons produced from red and white parents).

Bacterial Growth Phases

The four phases of bacterial culture growth: lag phase (environmental adjustment), log phase (rapid exponential multiplication), stationary phase (division equals death rate due to nutrient depletion/toxins), and death phase (population declines).

Viruses (Virions)

Sub-microscopic, non-living parasitic packages consisting of a DNA or RNA genome enclosed within a protein coat called a capsid (sometimes enveloped in a lipid membrane), requiring host cellular machinery to replicate.

Lytic Cycle vs. Lysogenic Cycle

The two modes of viral replication: in the lytic cycle, the virus actively directs the host cell to assemble new virions until the cell lyses; in the lysogenic cycle, the viral genome integrates into the host DNA and replicates silently until induced into lysis.

Fomite

Any inanimate object—such as doorknobs, medical instruments, toys, or water glasses—that harbors a pathogen and facilitates indirect disease transmission between hosts.

Vector-Borne Transmission

The transmission of pathogens between living organisms by intermediate carriers, commonly arthropods such as mosquitoes, ticks, or fleas, through either mechanical or biological mechanisms.

Protists

A diverse grouping of small, eukaryotic, predominantly single-celled organisms categorized into plantlike forms (algae), animal-like forms (protozoa), and fungus-like forms (slime and water molds).

Helminths

Multicellular parasitic worms, such as roundworms, tapeworms, pinworms, and flukes, that inhabit human digestive tracts and can be treated clinically with vermifuge medications.

Innate Immunity

The nonspecific, antigen-independent defense system present at birth that relies on mechanical barriers, chemical defenses (such as lysozyme and gastric acid), phagocytes, and natural killer cells, without conferring immunological memory.

Adaptive Immunity

The antigen-specific branch of the immune system that develops over time, mediated by B and T lymphocytes, which produces targeted cellular and humoral defenses and establishes immunological memory.

T-Lymphocytes (T Cells)

Adaptive immune cells that mature in the thymus and mediate cell-mediated immunity; subtypes include cytotoxic T cells (kill infected cells), helper T cells (secrete cytokines to activate B and T cells), and regulatory T cells (suppress immune responses).

B-Lymphocytes (B Cells)

Adaptive immune cells that differentiate in the bone marrow and, upon activation by circulating antigens, develop into plasma cells that secrete antigen-specific antibodies or into long-lived memory B cells.

Mucosa-Associated Lymphoid Tissue (MALT)

Clusters of lymphoid tissue containing T cells, B cells, and macrophages located in the tonsils, appendix, and Peyer's patches of the small intestine to defend mucosal surfaces against invading pathogens.