Unit 1-3 Biology: Cell Theory, Structures, Cell Cycle, and Transport Mechanisms

Comprehensive vocabulary flashcards covering cell discovery, cell theory, microscopy, eukaryotic and prokaryotic organelles, the cell cycle, mitosis, meiosis, and membrane transport mechanisms based on the lecture notes.

Robert Hooke

English scientist who published Micrographia in 1665 and coined the term 'cell' after observing cork tissue under a microscope.

Anton van Leeuwenhoek

Dutch scientist who discovered single-celled organisms, which he named 'animalcules', using his handcrafted microscopic lenses in the 1670s.

Matthias Schleiden

German botanist who concluded in the 1830s that all plants are composed of cells.

Theodor Schwann

German zoologist who concluded in the 1830s that all animals are composed of cells.

Rudolf Virchow

Pathologist who proposed 'Omnis cellula e cellula' in 1855, stating that new cells arise from pre-existing cells through cell division.

Cell Theory

Fundamental biological principle stating that all living organisms are composed of one or more cells, the cell is the basic unit of structure and function, and all cells arise from pre-existing cells.

Light Microscope

An optical instrument that uses visible light ($400\,nm$ to $700\,nm$) and glass lenses to magnify living or dead specimens up to $1,000\times$ to $1,500\times$ (maximum practical magnification up to $2,000\times$).

Electron Microscope

A high-resolution microscope that uses a beam of high-speed electrons and electromagnetic coils instead of light, capable of magnifications up to $1,000,000\times$ to examine strictly dead or fixed specimens in a vacuum.

Transmission Electron Microscope (TEM)

An electron microscope where electrons pass through a thin specimen to produce detailed 2D internal images of cellular ultrastructure at magnifications up to $2,000,000\times$.

Scanning Electron Microscope (SEM)

An electron microscope that bounces electrons off the specimen's surface to produce detailed 3D images of surface topography at magnifications up to $100,000\times$ to $500,000\times$.

Prokaryotic Cell

A small, simple cell lacking a membrane-enclosed nucleus and membrane-bound organelles, containing single circular DNA within a nucleoid region.

Eukaryotic Cell

A complex cell containing a membrane-bound nucleus and numerous specialized membrane-bound organelles, with linear DNA organized into chromosomes.

Cell Membrane

A thin, flexible, selectively permeable boundary composed of a phospholipid bilayer and embedded proteins that regulates the movement of substances into and out of the cell.

Phospholipids

Amphipathic lipid molecules forming the structural backbone of cell membranes, composed of hydrophilic glycerol-phosphate heads and hydrophobic fatty acid tails.

Cell Wall

A nonliving, rigid outer layer surrounding the cell membrane in plants, fungi, and bacteria that provides structural support and protection.

Cytoplasm

The jelly-like fluid substance enclosed within the cell membrane that provides a medium for chemical reactions and suspends organelles.

Nucleus

The control organelle of a eukaryotic cell, enclosed by a porous double nuclear envelope, which stores genetic material (DNA) and directs cell activities.

Chromatin

The uncoiled, thread-like complex of DNA and histone proteins present in the eukaryotic nucleus during interphase.

Chromosomes

Condensed, rod-like structures of DNA and histone proteins formed during cell division that carry genetic information.

Nucleolus

A dense structure inside the nucleus that disappears during cell division and is responsible for producing ribosomes.

Mitochondrion

A double-membrane organelle, known as the powerhouse of the cell, that performs cellular respiration to generate cellular energy ($ATP$).

Cristae

The inner membrane folds of a mitochondrion that increase surface area for chemical reactions involved in ATP production.

Rough Endoplasmic Reticulum

A network of membrane tubules studded with ribosomes that synthesizes membrane proteins and proteins intended for export out of the cell.

Smooth Endoplasmic Reticulum

A ribosome-free network of membrane tubules that synthesizes lipids (steroids), regulates calcium levels in muscle cells, and neutralizes toxic substances in the liver.

Ribosomes

Non-membrane-bound cellular structures that serve as protein factories, existing either free in the cytoplasm or attached to the rough ER.

Golgi Apparatus

A stack of flattened membrane sacs featuring a receiving side (cis face) and a shipping side (trans face) that modifies, packages, and routes proteins and lipids.

Lysosomes

Membrane-bound organelles containing digestive enzymes that break down food, foreign invaders, and worn-out cell parts, and execute programmed cell death.

Cytoskeleton

An internal protein framework comprising threadlike microfilaments (actin) and tubelike microtubules (tubulin) that maintains cell shape and enables organelle movement.

Centrioles

Paired barrel-shaped microtubule structures located near the nucleus in animal cells that organize spindle fibers during cell division.

Cilia

Short, hair-like projections on the cell surface that move in coordinated beats to propel cells, move fluids across surfaces, or provide sensory perception.

Flagella

Long, whip-like appendages that move in an undulating motion to enable cell locomotion (such as in sperm cells or bacteria).

Vacuoles

Fluid-filled storage sacs within cells; plant cells typically contain a single large central vacuole that maintains cell turgor.

Chloroplasts

Double-membrane plant organelles containing chlorophyll, thylakoids stacked into grana, and stroma, which convert solar energy into glucose via photosynthesis.

Cell Cycle

An organized series of events in which a cell grows, replicates its DNA, passes checkpoints, and divides to form new cells.

Interphase

The longest period of the cell cycle, comprising G1, S, and G2 phases, during which the cell grows, performs metabolic functions, and duplicates its DNA.

G1 Phase

The first gap phase of interphase where the cell expands in size, increases its organelle count, and synthesizes enzymes needed for DNA replication.

S Phase

The synthesis phase of interphase during which nuclear DNA replicates, converting single chromosomes into pairs of sister chromatids joined at the centromere.

G2 Phase

The second gap phase of interphase where the cell continues growing, synthesizes proteins and microtubules, and repairs DNA errors before mitosis.

Mitosis

A nuclear division process in somatic cells consisting of prophase, metaphase, anaphase, and telophase that results in two identical diploid daughter cells.

Prophase

The initial stage of mitosis where chromatin condenses into distinct chromosomes, the nucleolus and nuclear envelope break down, and centrosomes form the spindle.

Metaphase

The stage of mitosis where duplicated chromosomes align single file along the cell's equatorial plane (metaphase plate).

Anaphase

The mitotic stage where centromeres divide and sister chromatids are pulled apart by spindle fibers toward opposite poles of the cell.

Telophase

The final stage of mitosis where chromosomes arrive at opposite poles, uncoil into chromatin, and nuclear envelopes reform around each set.

Cytokinesis

The division of the cytoplasm following mitosis, occurring via a cleavage furrow in animal cells or a cell plate in plant cells to form two daughter cells.

Binary Fission

A simple, rapid asexual reproduction process in prokaryotes where single circular DNA replicates, segregates, and the cell splits via a central septum.

Apoptosis

A regulated process of programmed cell death that systematically removes damaged, old, unneeded, or dangerous cells.

Necrosis

Uncontrolled cell death caused by physical injury, infection, or toxins, leading to cell swelling, lysis, and inflammation in surrounding tissue.

Meiosis

A two-stage cell division process in germ line cells that halves the chromosome number from diploid ($2n$) to haploid ($n$), producing four unique gametes.

Synapsis

The side-by-side pairing of homologous chromosomes during Prophase I of meiosis to form a bivalent or tetrad structure.

Crossing Over

The physical exchange of genetic material between non-sister chromatids of homologous chromosomes during Prophase I, producing recombinant DNA.

Passive Transport

The movement of substances across a biological membrane down their concentration gradient without consuming cellular energy ($ATP$).

Simple Diffusion

The net movement of solute particles from an area of higher concentration to lower concentration directly through the phospholipid bilayer.

Osmosis

The diffusion of water molecules across a selectively permeable membrane from a region of lower solute concentration to higher solute concentration.

Facilitated Diffusion

Passive transport of large or lipid-insoluble molecules across the cell membrane down a concentration gradient using specific transmembrane carrier or channel proteins.

Filtration

The passage of water and solutes across a semi-permeable membrane driven by mechanical or hydrostatic pressure down a pressure gradient.

Active Transport

The movement of ions or molecules across a cell membrane against their concentration gradient requiring energy expenditure ($ATP$) and membrane carrier pumps.

Exocytosis

An active transport process in which intracellular vesicles fuse with the plasma membrane to secrete or expel materials outside the cell.

Endocytosis

An active transport mechanism where the plasma membrane invaginates to engulf extracellular materials inside newly formed vesicles.

Phagocytosis

A form of endocytosis ('cell eating') in which large solid particles, bacteria, or cellular debris are engulfed into a phagosome vesicle for enzymatic breakdown.

Pinocytosis

A form of endocytosis ('cell drinking') where droplets of extracellular fluid containing dissolved nutrients are non-selectively internalized into small vesicles.

Receptor-Mediated Endocytosis

A highly specific endocytic process where target extracellular ligands bind to designated cell-surface receptors before being internalized in coated vesicles.