Cell: The Unit of Life and Structural Foundations

These flashcards provide a comprehensive review of the vocabulary and key concepts from the lecture on cell biology, covering cell theory, prokaryotic and eukaryotic structures, and various organelle functions.

Reductionist Biology

A physico-chemical approach to studying living organisms that applies the concepts and techniques of physics and chemistry to explain biological processes in molecular terms.

G.N. Ramachandran

A prominent figure in structural biology who discovered the triple helical structure of collagen in $2026-27$ and developed a eponymous plot for analyzing the allowed conformations of proteins.

Cell

The fundamental structural and functional unit of all living organisms; anything less than a complete structure of this unit does not ensure independent living.

Antonie Von Leeuwenhoek

The scientist who first saw and described a live cell.

Robert Brown

The scientist credited with the discovery of the nucleus in the year $1831$.

Cell Theory

A theory formulated by Schleiden and Schwann, later refined by Rudolf Virchow, stating that all living organisms are composed of cells and their products, and all cells arise from pre-existing cells.

Omnis cellula-e cellula

A Latin phrase used by Rudolf Virchow in $1855$ to explain that new cells are formed through the division of pre-existing cells.

Mycoplasmas

The smallest known cells, which are only $0.3\,\mu m$ in length.

Plasmids

Small circular DNA molecules found in many bacteria outside the genomic DNA that confer unique phenotypic characters, such as antibiotic resistance.

Mesosome

A specialized differentiated form of the prokaryotic cell membrane formed by internal extensions like vesicles, tubules, and lamellae; it aids in functions like cell wall formation, DNA replication, and respiration.

Gram Positive and Gram Negative

Classifications of bacteria based on the chemical complexity of their cell envelopes and their reaction to a specific staining procedure developed by Gram.

Fluid Mosaic Model

An improved model of plasma membrane structure proposed by Singer and Nicolson in $1972$, describing the quasi-fluid nature of lipids which enables the lateral movement of proteins within the bilayer.

Active Transport

An energy-dependent process in which ions or molecules move across a membrane against their concentration gradient using ATP, such as the $Na^+/K^+$ Pump.

Middle Lamella

A layer in plant cell walls made primarily of calcium pectate that functions to glue adjacent cells together.

Endomembrane System

A collection of membrane-bound organelles with coordinated functions, including the endoplasmic reticulum, golgi complex, lysosomes, and vacuoles.

Rough Endoplasmic Reticulum ($RER$)

A type of endoplasmic reticulum bearing ribosomes on its outer surface that is involved in protein synthesis and secretion.

Golgi Apparatus

A system of flat disc-shaped sacs called cisternae, first observed by Camillo Golgi in $1898$, which packages materials into vesicles for intracellular delivery or secretion.

Lysosomes

Membrane-bound vesicular structures containing hydrolytic enzymes such as lipases and proteases that are active at acidic $pH$ for digesting macromolecules.

Mitochondria

Double membrane-bound organelles known as the 'power houses' of the cell, which serve as sites for aerobic respiration and produce $ATP$.

Thylakoids

Organized flattened membranous sacs present in the stroma of chloroplasts that are arranged in stacks called grana.

Svedberg’s Unit ($S$)

A unit used as the sedimentation coefficient for ribosomes, serving as an indirect measure of their density and size.

Cytoskeleton

An elaborate network of filamentous proteinaceous structures in the cytoplasm, including microtubules and microfilaments, that provides mechanical support and motility.

Axoneme

The core of eukaryotic cilia and flagella, typically showing a $9+2$ array of microtubules consisting of nine peripheral doublets and two central microtubules.

Centromere

The primary constriction on a chromosome where sister chromatids are held together and disc-shaped kinetochores are attached.

Nucleolus

A non-membrane bound spherical structure in the nucleus where active ribosomal $RNA$ synthesis occurs.