Chapter 04 Evolutionary Origin of Cells - Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering the origin of life, cell structure, endomembrane system, organelles, protein sorting, and microscopy concepts from the notes.

Cell Theory

All living organisms are composed of one or more cells; cells are the smallest units of life; new cells arise only from pre-existing cells by division (Schleiden, Schwann; Virchow).

Prokaryote

Simple cells without a membrane-bound nucleus; include Bacteria and Archaea; typically 1–10 μm in diameter.

Eukaryote

Cells with a membrane-bound nucleus and internal membranes that form membrane-bound organelles.

Protobiont

An aggregate of prebiotically produced molecules with a boundary (lipid bilayer) that maintains a distinct internal environment.

Liposome

A vesicle enclosed by a lipid bilayer that can encapsulate biochemicals, model protobionts, and enclose RNA.

Nucleotides

Monomers that polymerize to form DNA and RNA.

Polymers (DNA/RNA/Proteins)

Long chains formed by polymerization of monomers (nucleotides for nucleic acids; amino acids for proteins).

Prebiotic Soup

A mixture of organic molecules on early Earth from which polymers and biopolymers could form.

Reducing Atmosphere Hypothesis

Early Earth atmosphere rich in H2, CH4, NH3 with little O2 that could drive abiotic synthesis of organic molecules (Miller–Urey experiments).

Extraterrestrial Hypothesis

Organic molecules delivered to Earth by meteorites, comets, or interplanetary dust.

Deep-Sea Vent Hypothesis

Biologically important molecules could form in temperature gradients at hydrothermal vents; vent ecosystems powered by chemical energy.

Stage 2: Organic Polymers

Prebiotic synthesis of nucleic acids and polypeptides; polymerization favored on surfaces like clay; aqueous polymer formation can occur under certain conditions.

Stage 3: Protobiont Boundaries

Protobionts formed boundaries (lipid membranes) that separate internal chemistry from the environment.

Four Characteristics of Protobionts

(1) Boundary separating environment from interior; (2) Polymers inside contain information; (3) Polymers can have catalytic function; (4) Protobionts capable of self-replication.

Liposomes (as Protobionts)

Vesicles formed from lipid bilayers that can enclose RNA and other molecules, modeling early cellular compartments.

Stage 4: RNA World

Hypothetical early period where RNA stored information, catalyzed reactions (ribozymes), and mediated early protein synthesis before DNA/proteins dominated.

Ribozyme

RNA molecule with catalytic ability, enabling biochemical reactions such as peptide bond formation or nucleotide synthesis.

Chemical Selection

A process where certain molecules with advantageous properties increase in frequency, driving chemical evolution.

RNA World → DNA/RNA/Protein World

Transition from an RNA-centric world to one where DNA stores information and proteins perform most catalytic roles.

DNA/RNA/Protein World Advantages

DNA stores information more stably; proteins offer greater catalytic efficiency and diverse functions.

Microscopy

Study of cells using instruments that magnify or illuminate samples to reveal structure.

Resolution

Ability to distinguish two adjacent objects as separate; higher resolution reveals finer detail.

Contrast

Difference in appearance that helps distinguish structures; enhanced by dyes or special optics.

Magnification

Ratio of image size to actual size produced by a microscope.

Light Microscope

Uses visible light to illuminate specimens; typical resolution around 0.2 μm.

Electron Microscope

Uses electron beams to image specimens; much higher resolution (about 0.1 nm) than light microscopes.

Endomembrane System

Network of membranes including the nuclear envelope, ER, Golgi, lysosomes, vacuoles, peroxisomes, and plasma membrane; coordinates protein and lipid trafficking.

Nucleus

Organelle housing most genetic material; site of transcription; contains chromatin, nucleolus, and nuclear envelope.

Nuclear Envelope

Double membrane surrounding the nucleus with nuclear pores for transport.

Chromatin

Complex of DNA and proteins that forms chromosomes; becomes visible during cell division.

Nucleolus

Nuclear substructure where ribosomal RNA synthesis and ribosome subunit assembly occur.

Rough Endoplasmic Reticulum (Rough ER)

ER region studded with ribosomes; synthesizes and sorts proteins destined for ER, Golgi, lysosomes, membranes, or secretion; involved in glycosylation.

Smooth Endoplasmic Reticulum (Smooth ER)

ER region lacking ribosomes; functions in detoxification, carbohydrate metabolism, calcium storage, and lipid synthesis.

Golgi Apparatus

Stack of flattened membranes where proteins/lipids are modified, sorted, and packaged for secretion or delivery to other organelles; contains cis, medial, and trans regions.

Lysosome

Organelle containing acid hydrolases that degrade macromolecules; involved in autophagy.

Vacuole

Membrane-bound compartment with varied functions; central vacuole in plants; contractile and phagocytic vacuoles in other organisms.

Peroxisome

Organelle that breaks down toxic molecules; contains catalase; glyoxysomes in plants convert fats to sugars.

Semiautonomous Organelles

Organelles that grow and divide but depend on the cell for some components (mitochondria and chloroplasts).

Mitochondrion

Organelle that generates ATP; contains cristae; mitochondrial matrix; has its own genome; divides by binary fission.

Chloroplast

Organelle for photosynthesis; contains thylakoids (grana) and stroma; has chloroplast genome.

Endosymbiosis Theory

Mitochondria and chloroplasts originated from engulfed bacteria (proteobacteria and cyanobacteria) living inside a host cell.

Mitochondrial/Chloroplast Genomes

Small, circular DNA genomes in these organelles; resemble bacterial genomes and can be transmitted maternally in many species.

Protein Sorting

Targeting of newly synthesized eukaryotic proteins to their correct destinations using sorting signals.

Sorting Signals

Amino acid sequences that direct proteins to cytosol, ER, Golgi, lysosomes, mitochondria, chloroplasts, or nucleus.

Cotranslational Sorting

Proteins with ER targeting signals are directed to the ER during translation via SRP.

Post-translational Sorting

Proteins are fully synthesized in the cytosol and then imported into organelles such as nucleus, mitochondria, chloroplasts, or peroxisomes.

SRP (Signal Recognition Particle)

Ribonucleoprotein that binds ER signal sequences and pauses translation to direct ribosome to the ER membrane.

Proteome

The entire complement of proteins expressed by a cell, varying by cell type and conditions, even with identical genomes.

Cytosol

Region of the cytoplasm outside organelles; central coordinating region for metabolism.

Cytoskeleton

Network of protein filaments (microtubules, intermediate filaments, actin) that supports cell shape and enables movement.

Microtubules

Long hollow tubes of tubulin with plus and minus ends; undergo dynamic instability; nucleated at MTOC; organize chromosomes.

Actin Filaments (Microfilaments)

Flexible filaments essential for cell shape, movement, and membrane support; grow/shrink at plus/minus ends.

Pseudopodia

Temporary, finger-like projections of the plasma membrane used for movement and engulfing particles.

Flagella and Cilia

Motile structures with a 9+2 microtubule array; dynein motors; used for movement and sensory functions.