Biology Preparation Guide: Cells, Genetics, Immunity, and Ecology

Comprehensive vocabulary flashcards covering key concepts in cell biology, molecular genetics, biotechnology, human immunology, ecological cycles, and natural selection based on the lecture preparation guide.

Osmosis

The movement or diffusion of water across a semipermeable membrane from a region of higher water concentration to a region of lower water concentration.

Turgor pressure

The internal hydrostatic pressure developed within plant cells as water enters them when exposed to a hypotonic solution, resisted by the rigid cell wall.

Semipermeable membrane

A biological membrane (also called selectively permeable) that regulates what enters and exits the cell, permitting certain molecules like water to cross while blocking solutes.

Phospholipids

The primary structural lipid molecules that compose the plasma membrane.

Nucleic acids

Carbon-based macromolecules that store and carry genetic information within the cell.

Mitochondrion

The eukaryotic organelle responsible for producing the majority of cellular $ATP$ through cellular respiration.

Chloroplast

The specialized organelle found in plant cells where photosynthesis takes place.

Monosaccharides

Simple sugars that serve as the fundamental building blocks for many carbohydrates.

S phase

The stage of the eukaryotic cell cycle during which $DNA$ replication takes place prior to $G_2$ and mitosis.

Helicase

The enzyme that separates double-stranded $DNA$ during replication by breaking the hydrogen bonds between paired nitrogenous bases.

Metaphase

The stage of mitosis during which duplicated chromosomes line up along the equator of the cell.

Anaphase

The stage of mitosis during which sister chromatids separate and begin moving toward opposite spindle poles.

Cytokinesis

The division of the cytoplasm that follows nuclear division during cell division.

Homologous chromosomes

A pair of maternal and paternal chromosomes that carry the same types of genes, potentially with different alleles.

Sister chromatids

Identical replicated copies of a single chromosome joined together prior to cell division.

Restriction endonuclease

An enzyme used in recombinant $DNA$ technology that cuts $DNA$ molecules at specific recognition sites.

DNA ligase

An enzyme that seals, joins, or pastes the ends of $DNA$ fragments together when cloning into a vector.

Bacterial plasmid

A small circular $DNA$ molecule used as a vector to carry inserted foreign $DNA$ fragments into bacterial cells for replication.

Transcription

The process by which genetic information from a $DNA$ template is copied into an $RNA$ molecule.

Translation

The biological process of assembling amino acids into a polypeptide chain according to the sequence of codons on an $mRNA$ molecule.

RNA splicing

The post-transcriptional modification process of removing non-coding introns and joining coding exons together within pre-$mRNA$.

Alternative RNA splicing

A regulatory mechanism where different combinations of exons from the same pre-$mRNA$ are spliced together to form distinct mature $mRNA$s, enabling one gene to produce multiple protein forms.

Codon

A sequence of three consecutive nucleotides on an $mRNA$ molecule that codes for a specific amino acid or a stop signal.

Anticodon

A complementary three-base sequence located on a $tRNA$ molecule that pairs with a corresponding $mRNA$ codon during translation.

Degenerate genetic code

The redundancy in the genetic code whereby more than one codon can specify the same amino acid, reducing the harmful consequences of some point mutations.

Crossing over

The reciprocal exchange of genetic material between non-sister chromatids of homologous chromosomes during meiosis, creating new allele combinations.

Independent assortment

The random distribution of maternal and paternal homologous chromosomes into gametes during meiosis, generating genetic diversity in offspring.

Alleles

Alternative functional forms or sequence variants of the same gene.

Genotype

The complete genetic makeup or specific allele combination possessed by an organism.

Phenotype

The observable physical, biochemical, or physiological characteristics of an organism produced by the interaction of its genotype with the environment.

X inactivation

The epigenetic process in individuals with two $X$ chromosomes wherein one $X$ chromosome is randomly and largely silenced in each somatic cell to equalize dosage of $X$-linked genes.

Macrophage

A large phagocytic white blood cell belonging to the innate immune system that engulfs and digests cellular debris and foreign pathogens.

Lytic cycle

A viral replication pathway in which the virus synthesizes new viral particles inside the host cell, ultimately causing the host cell to rupture and lyse.

Lysogenic cycle

A viral pathway in which viral $DNA$ is integrated into and stably maintained within the host genome without immediate lysis, remaining capable of later entering the lytic cycle.

Interferons

A group of cytokine signaling proteins released by virus-infected host cells that trigger an early innate immune defense to suppress viral spread.

Natural killer cells

Innate immune lymphocytes that destroy infected target cells by releasing pore-forming molecules into target cell membranes and initiating apoptosis.

Perforin

A pore-forming cytotoxic protein secreted by cytotoxic $T$ cells that creates channels in the membranes of targeted infected cells.

Memory cells

Long-lived lymphocytes formed during a primary immune response that facilitate a faster and stronger secondary adaptive immune response upon re-exposure to the same antigen.

Active immunity

Acquired immunity that develops when an individual's own adaptive immune system is stimulated to produce antibodies and memory cells following exposure to an antigen or vaccination.

Passive immunity

Short-term immunity that results from the transfer of pre-formed antibodies produced by another organism rather than the recipient's own immune system.

Plasma B cells

Effector $B$ lymphocytes that actively synthesize and secrete large quantities of specific antibodies.

Helper T cells

A class of $T$ lymphocytes that direct, activate, and coordinate the activities of other immune cells during adaptive immune responses.

Opsonization

The immunological process of coating an antigen or pathogen with antibodies or other molecules to facilitate recognition and engulfment by phagocytes.

Antigen

Any molecule or molecular structural feature that is recognized by the immune system and can bind specific receptors or antibodies.

Herd immunity

The indirect epidemiological protection of susceptible individuals in a population that occurs when a high threshold of individuals have developed immunity, hindering infectious spread.

Nitrogenase

The specialized enzyme complex that catalyzes biological nitrogen fixation, reducing atmospheric nitrogen ($N_2$) into ammonia ($NH_3$).

Transpiration

The physiological process by which water vapor evaporates from inside plant tissues through open stomata into the surrounding atmosphere.

Denitrification

The microbial conversion of soil nitrates into gaseous nitrogen compounds, primarily returning molecular nitrogen gas ($N_2$) back into the atmosphere.

Ten percent ($10\%$) rule

The ecological principle that approximately $10\%$ of chemical energy stored as biomass transfers from one trophic level up to the next, with the remainder dissipating largely as heat.

Constrictive population pyramid

An age-structure diagram characterized by a narrower base than middle, indicating lower proportions of younger individuals and projecting potential future population decline.

Antibiotic resistance

The evolved ability of a bacterial population to withstand previously lethal antibiotic concentrations through natural selection driven by variation, heritability, and differential survival.