Lipids, Membrane Dynamics, and Evolution Vocabulary

Vocabulary flashcards covering lipid chemistry, membrane transport dynamics, and evolutionary principles based on the lecture transcripts.

Triglyceride

A dietary lipid molecule composed of one glycerol molecule linked to three fatty acid chains by ester linkages ($-C-O-C-$).

Ester Linkage

The covalent bond formed between a hydroxyl group of glycerol and a carboxyl group of a fatty acid, represented as $-C-O-C-$.

Phospholipid

An amphipathic lipid molecule consisting of a hydrophilic head (glycerol, phosphate, and choline) and two hydrophobic fatty acid tails, forming the primary structure of cell membranes.

Amphipathic

Describing a chemical compound that contains both hydrophilic (polar) and hydrophobic (nonpolar) properties within its structure.

Micelle

A spherical aggregate of amphipathic lipid molecules formed in water, where hydrophobic tails sequester inward away from water and hydrophilic heads point outward.

Lipid Bilayer

A double-layered sheet formed by phospholipids in aqueous solutions, with hydrophobic tails shielded in the interior and hydrophilic heads facing the external water environment.

Cholesterol

A sterol lipid composed of four fused carbon rings with variable functional groups that resides in cell membranes to regulate membrane fluidity and resist freezing.

Low Density Lipoprotein (LDL)

A blood-transport particle that packages insoluble cholesterol and can deposit cholesterol into artery walls to form plaque.

High Density Lipoprotein (HDL)

A blood-transport particle that scavenges excess cholesterol from tissues and artery walls for transport back to the liver.

Transmembrane Protein

An integral membrane protein that completely spans the hydrophobic interior of the cell membrane, usually anchored by an odd number of $\alpha$ helices.

Simple Diffusion

Unassisted passive transport of membrane-permeable (penetrating) solutes across a membrane down their concentration gradient from high to low concentration without external energy.

Osmosis

The passive movement of water across a semi-permeable membrane down its concentration gradient to equilibrate concentrations of nonpenetrating solutes.

Osmolarity

The total concentration of all solutes (both penetrating and nonpenetrating) present in a solution.

Tonicity

The capability of an extracellular solution to alter cell volume via osmosis, determined strictly by the concentration of nonpenetrating solutes relative to the cytoplasm.

Contractile Vacuole

A specialized organelle found in freshwater protists that collects and expels excess water to prevent cell lysis in a hypotonic environment.

Facilitated Diffusion

Passive transport of solutes across a membrane down their concentration gradient assisted by specific transmembrane proteins, such as channels or carriers.

Active Transport

Energy-dependent movement of solutes across a biological membrane against their concentration gradient, requiring ATP or electrochemical gradients.

Sodium-Potassium Pump ($Na^+/K^+$ ATPase)

A primary active transport protein that uses ATP hydrolysis to pump sodium ions ($Na^+$) out of the cell and potassium ions ($K^+$) into the cell.

Cotransport

A transport mechanism in which the downhill diffusion of one solute provides the energy to pump another solute uphill against its concentration gradient.

Symport

A cotransport process in which two different molecules or ions are moved across the cell membrane in the exact same direction.

Antiport

A cotransport process in which two different molecules or ions are moved across the cell membrane in opposite directions.

Microevolution

Evolutionary change on a small scale, specifically generation-to-generation shifts in allele frequencies within a population.

Macroevolution

Evolutionary change on a large scale over evolutionary time, resulting in broad phenotypic changes and the origin of new taxonomic groups.

Descent with Modification

Darwin's principle that all organisms are descended from ancestral species, accumulating structural and functional modifications over generations as they adapt to diverse environments.

Darwinian Fitness

A quantitative measure of reproductive success, defined by the total number of offspring produced and genes contributed to the next generation's gene pool.

Artificial Selection

The selective breeding of domesticated plants and animals by humans to encourage the expression of specific desirable traits.

Natural Selection

The mechanism of evolution in which individuals possessing certain heritable traits survive and reproduce at higher rates than other individuals because of those traits.

Somatic Mutation

A genetic mutation occurring in non-reproductive body cells, which affects only the individual organism and cannot be passed to offspring.

Gametic Mutation

A genetic mutation occurring in reproductive germ cells or gametes, which can be inherited by offspring and introduce new variations into a population's gene pool.

Directional Selection

A mode of natural selection in which conditions favor individuals expressing one extreme phenotype, shifting the overall population trait distribution in that direction.

Disruptive Selection

A mode of natural selection in which conditions favor individuals at both extremes of a phenotypic spectrum over individuals with intermediate traits.

Stabilizing Selection

A mode of natural selection that acts against extreme phenotypes, favoring intermediate variants and reducing trait variation in a population.

Sexual Selection

A form of natural selection in which individuals with specific inherited physical or behavioral characteristics are preferred as mates, often leading to sexual dimorphism.

Homologous Structures

Anatomical structures present in different species that are shared due to common ancestry, even though they may serve different functions in present-day organisms.

Vestigial Homology

A historical anatomical feature with reduced size and function compared to its functional counterpart in an organism's evolutionary ancestors.

Developmental Homology

Structural similarities observable in the embryos of different species that reflect shared ancestry, which may disappear as the organism matures.

Analogous Structures

Structures in different species that share similar form and function due to convergent evolution under similar environmental pressures rather than shared inheritance from a common ancestor.

Convergent Evolution

The independent evolution of similar features in distinct evolutionary lineages that do not share a recent common ancestor.

Biological Species Concept

A definition of a species as a group of natural populations whose members have the potential to interbreed and produce viable, fertile offspring.

Morphological Species Concept

A definition of a species based solely on measurable physical and structural traits, commonly applied to fossil organisms.

Ecological Species Concept

A definition of a species in terms of its ecological niche, defined by the specific set of environmental resources and interactions it utilizes.

Mass Extinction

A geologically brief event during which Earth loses greater than $50\%$ of its total biological species, vacating ecological niches and driving subsequent evolutionary radiation.