Cell Biology Lecture Notes

Vocabulary flashcards covering key terms from lecture notes on cell structure, cell theory, microscopy, mitosis and meiosis, prokaryotic and eukaryotic organelles, plant and bacterial cell features, and related biological concepts.

Cell

Smallest structural and functional unit of life, capable of carrying out all vital processes.

Unicellular Organism

Living thing composed of a single cell, e.g., bacteria or protozoa.

Multicellular Organism

Living thing composed of many specialized cells, e.g., plants and animals.

Cell Theory

Principle stating that all living things are made of cells, cells are the basic units of life, and all cells arise from pre-existing cells.

Spontaneous Generation

Discredited idea that life can arise from non-living matter; disproved by cell theory.

Microscope

Instrument that magnifies small objects so they can be observed in detail.

Compound Microscope

Microscope with two or more lenses that provides higher magnification than a single lens.

Zacharias Janssen

Dutch spectacle maker credited with building the first compound microscope (~1595).

Robert Hooke

English scientist who coined the term “cell” after observing cork under a microscope (1665).

Anton van Leeuwenhoek

Dutch scientist who crafted powerful single-lens microscopes and first observed bacteria and protists.

Matthias Schleiden

German botanist who concluded that all plants are made of cells (1838).

Theodor Schwann

German physiologist who concluded that all animals are made of cells (1839).

Rudolf Virchow

German physician who stated "Omnis cellula e cellula"—all cells come from pre-existing cells (1858).

Robert Remak

Jewish scientist who provided earlier evidence for cell division (1855).

Omnis cellula e cellula

Latin for “every cell from a cell,” expressing the concept that cells originate only from existing cells.

Mitosis

Eukaryotic cell division producing two genetically identical diploid daughter cells for growth and repair.

Meiosis

Specialized cell division producing four genetically diverse haploid gametes for sexual reproduction.

Diploid (2n)

Cell containing two complete sets of chromosomes—one from each parent.

Haploid (n)

Cell containing a single set of chromosomes, typical of gametes.

Chromosome

Condensed threadlike DNA structure carrying genetic information during cell division.

Sister Chromatid

One of two identical DNA strands formed by replication and joined at a centromere.

Tetrad

Pair of homologous chromosomes (four chromatids) aligned during meiosis I.

Crossing-Over

Exchange of genetic material between homologous chromatids during meiosis, increasing variation.

Prokaryote

Cell without a nucleus or membrane-bound organelles; includes bacteria and archaea.

Eukaryote

Cell with a true nucleus and membrane-bound organelles; includes plants, animals, fungi, and protists.

Cell Membrane (Plasma Membrane)

Semipermeable phospholipid bilayer that encloses the cytoplasm and regulates material passage.

Phospholipid Bilayer

Two-layer arrangement of phospholipids forming the fundamental structure of cell membranes.

Cytoplasm

Cellular region between nucleus and plasma membrane containing cytosol and organelles.

Cytoskeleton

Network of protein filaments (microfilaments, intermediate filaments, microtubules) giving cell shape and movement.

Microfilament

7-nm actin filament involved in cell movement and muscle contraction.

Intermediate Filament

10-nm stable filament providing tensile strength to cells.

Microtubule

25-nm tubulin cylinder that shapes cells and guides organelle movement; forms spindle fibers.

Centriole

Pair of microtubule structures at right angles that organize spindle apparatus during animal cell division.

Nucleus

Membrane-bound organelle housing DNA and controlling cellular activities.

Nuclear Envelope

Double membrane surrounding the nucleus, containing nuclear pores for transport.

Nucleolus

Dense nuclear region that synthesizes ribosomal RNA and assembles ribosome subunits.

Chromatin

DNA-protein complex in the nucleus that condenses to form chromosomes during division.

Ribosome

RNA-protein complex that synthesizes proteins; found free in cytosol or bound to rough ER.

Endoplasmic Reticulum (ER)

Membranous network of cisternae continuous with nuclear envelope; rough and smooth types.

Rough ER

ER studded with ribosomes; synthesizes and transports proteins for secretion or membranes.

Smooth ER

ER lacking ribosomes; synthesizes lipids, detoxifies chemicals, and stores calcium.

Golgi Apparatus

Stack of flattened sacs that modifies, sorts, and packages proteins and lipids for delivery.

Vesicle

Small membrane-bound sac that transports or stores substances within a cell.

Lysosome

Digestive organelle containing hydrolytic enzymes that break down macromolecules and pathogens.

Mitochondrion

Double-membrane organelle producing ATP through cellular respiration; contains its own DNA.

ATP (Adenosine Triphosphate)

Primary energy currency of the cell produced mainly in mitochondria.

Flagellum

Long whip-like appendage composed of microtubules that propels certain cells, e.g., sperm.

Cilium

Short hair-like projection that beats rhythmically for cell movement or fluid transport.

Axoneme

9+2 microtubule core structure within cilia and flagella responsible for bending motion.

Basal Body

Microtubule organizing structure anchoring cilia or flagella, structurally similar to a centriole.

Cell Wall

Rigid outer layer external to plasma membrane providing support and protection in plants, fungi, bacteria, and algae.

Cellulose

Structural polysaccharide forming the primary component of plant cell walls.

Chitin

Nitrogen-containing polysaccharide forming fungal cell walls and arthropod exoskeletons.

Peptidoglycan

Polymer of sugars and amino acids forming bacterial cell walls; thickness distinguishes Gram type.

Plasmodesmata

Cytoplasmic channels through plant cell walls that enable transport and communication between cells.

Root Hair

Thin extension of a root epidermal cell that increases surface area for water and mineral absorption.

Chloroplast

Double-membrane plant organelle containing chlorophyll and site of photosynthesis.

Thylakoid

Flattened membrane sac inside chloroplast where light-dependent reactions occur.

Stroma

Fluid matrix of chloroplast surrounding thylakoids; site of Calvin cycle.

Granum

Stack of thylakoids within a chloroplast.

Vacuole

Membrane-bound sac for storage and maintaining osmotic balance; large central vacuole in plants.

Tonoplast

Membrane surrounding the central vacuole in plant cells.

Turgor Pressure

Pressure of vacuolar contents against the cell wall, keeping plant cells rigid.

Capsule (Bacterial)

Sticky polysaccharide or protein layer outside some bacteria that aids in protection and adherence.

Plasmid

Small circular DNA molecule in bacteria carrying genes such as antibiotic resistance.

Pili (Fimbriae)

Hair-like bacterial surface structures aiding in attachment; sex pili transfer DNA during conjugation.

Inclusion Body

Cytoplasmic granule storing nutrients like glycogen, sulfur, or phosphate in bacteria.

Endospore

Dormant, highly resistant bacterial cell formed to survive extreme conditions.

Good Bacteria

Beneficial microbes that aid digestion, produce vitamins, or enrich soil.

Lactobacillus

Genus of probiotic bacteria that ferments lactose and supports gut health.

Binary Fission

Asexual reproduction in prokaryotes where one cell divides into two identical cells.

Svedberg Unit (S)

Unit describing sedimentation rate of particles like ribosomal subunits during centrifugation.

70S Ribosome

Prokaryotic ribosome composed of 50S and 30S subunits.

80S Ribosome

Eukaryotic ribosome composed of 60S and 40S subunits.