Cell Biology, Membrane Transport, and Cell Division

Comprehensive vocabulary flashcards covering cell theory, cellular ultrastructure, membrane transport mechanisms, mitotic cell division, and meiotic cell division based on lecture concepts.

Cell theory

A foundational biological principle stating that every living organism consists of one or more cells, the smallest organisms are single cells, cells are the functional units of multicellular organisms, and all cells arise from preexisting cells.

Light microscope

An instrument that uses lenses to focus visible light to allow scientists to view cells.

Electron microscope

A microscope that uses magnets to focus beams of electrons, capable of resolving much smaller structures than light microscopes.

Prokaryotic cells

Generally small cells with a simple internal structure that lack membrane-enclosed organelles, comprising all members of the domains Archaea and Bacteria.

Eukaryotic cells

Generally larger cells that contain a variety of membrane-enclosed structures called organelles, including a nucleus.

Peptidoglycan

The material that makes up the cell wall surrounding most bacteria.

Attachment pili

External protein strands that allow bacteria to attach to surfaces.

Sex pili

Structures that draw bacteria together to allow the transfer of plasmids between cells.

Plasmids

Small rings of DNA in bacteria that confer features such as antibiotic resistance.

Nucleoid region

The cellular area in a bacterium where most bacterial DNA is located in a single chromosome.

Extracellular matrix (ECM)

A supportive external structure secreted by cells; composed of proteins and polysaccharides in animal cells and composed primarily of cellulose as the supportive and porous cell wall in plant cells.

Nuclear envelope

A double membrane surrounding the eukaryotic nucleus containing pores that regulate the movement of molecules between the nucleus and cytoplasm.

Nucleolus

A specialized region within the eukaryotic nucleus that serves as the site of ribosome synthesis.

Ribosomes

Workbenches of the cell composed of rRNA and protein that serve as the sites of protein synthesis within the cytoplasm.

Mitochondria

Powerhouses of the eukaryotic cell that extract energy from food and store it in the high-energy bonds of ATP.

Plastids

A family of organelles found in plants and photosynthetic protists that include chloroplasts, as well as forms that store pigments or starch.

Chloroplasts

Specialized plastids in which photosynthesis captures solar energy and stores it in sugar molecules.

Endosymbiont hypothesis

The hypothesis stating that mitochondria and chloroplasts, as well as other plastids, originated from independently living prokaryotic cells.

Rough endoplasmic reticulum

A series of interconnected membranous compartments continuous with the outer nuclear envelope that bears ribosomes where proteins are manufactured, modified, folded, and transported.

Smooth endoplasmic reticulum

Membranous ER channels lacking ribosomes that manufacture lipids such as steroid hormones, detoxify drugs and metabolic wastes, and store calcium.

Golgi apparatus

A series of flattened membranous sacs that processes, modifies, sorts, and packages materials synthesized in the rough ER into vesicles for transport.

Lysosomes

Specialized membranous sacs containing digestive enzymes that merge with food vacuoles to break down food particles and digest defective organelles.

Central vacuoles

Large vacuoles in plant cells used to provide cellular support and to store nutrients, pigments, wastes, and toxic materials.

Contractile vacuoles

Organelles found in some freshwater protists that collect and expel excess water from the cell.

Fluid mosaic model

The structural representation of cell membranes as a bilayer of phospholipids in which a variety of proteins are embedded.

Enzymes (membrane)

Membrane proteins that promote biochemical chemical reactions on or near the cell membrane.

Recognition proteins

Membrane glycoproteins that label the cell and facilitate recognition by other cells, such as those of the immune system.

Transport proteins

Membrane-spanning proteins, such as carrier or channel proteins, that regulate the movement of most water-soluble substances across the plasma membrane.

Receptor proteins

Membrane proteins that bind specific molecules and trigger corresponding changes and biochemical responses within the cell.

Connection proteins

Membrane proteins that anchor the plasma membrane to the cytoskeleton and extracellular matrix or bind cells to one another.

Diffusion

The slow physical movement of substances from regions of higher concentration to regions of lower concentration down a concentration gradient.

Osmosis

The diffusion of water across a selectively permeable membrane down its concentration gradient through the phospholipid bilayer or through aquaporins.

Aquaporins

Specialized membrane channel proteins that facilitate the rapid diffusion of water molecules across the plasma membrane.

Simple diffusion

The passive transport mechanism by which water, dissolved gases, and lipid-soluble molecules move directly through the phospholipid bilayer down concentration gradients.

Facilitated diffusion

The movement of water and water-soluble molecules across a membrane down their concentration gradients through carrier or channel proteins without cellular energy expenditure.

Active transport

An energy-requiring transport mechanism in which carrier proteins use cellular energy ($\text{ATP}$) to move molecules across the plasma membrane against concentration gradients.

Endocytosis

An energy-requiring transport process by which cells engulf interstitial fluid, large molecules, or food particles into membrane-enclosed vesicles.

Pinocytosis

A form of endocytosis in which a cell takes in small droplets of extracellular or interstitial fluid.

Receptor-mediated endocytosis

A highly selective form of endocytosis that takes up specific molecules through coated pits on the plasma membrane.

Phagocytosis

A form of endocytosis in which large food particles or entire microorganisms are ingested, such as an Amoeba feeding on a Paramecium.

Exocytosis

An energy-requiring cellular transport process where membrane-enclosed sacs fuse with the plasma membrane to secrete substances or expel particulate cellular wastes.

Interstitial fluid

The extracellular fluid that bathes animal cells and is normally isotonic relative to the cytosol.

Prokaryotic fission

The cell cycle division process in prokaryotes where the single circular chromosome replicates and the cell divides into two genetically identical daughter cells.

Gene

A distinct segment of DNA found at a specific location on a chromosome that encodes genetic instructions.

Interphase

The prolonged phase of the eukaryotic cell cycle during which the cell grows and duplicates its chromosomes, partitioned into $G_1$, S, and $G_2$.

$G_1$ phase

The first growth phase of interphase during which the cell grows and may differentiate to perform a specialized function.

S phase

The synthesis phase of eukaryotic interphase during which the cell's DNA is replicated.

$G_2$ phase

The second growth phase of interphase occurring between DNA synthesis and the onset of mitosis.

Mitosis

The process of eukaryotic nuclear division consisting of prophase, metaphase, anaphase, and telophase.

Sister chromatids

Two identical copies of a duplicated chromosome that remain attached to each other at the centromere during early mitotic division.

Centromere

The specialized attachment region holding two identical sister chromatids together before their separation in cell division.

Kinetochore

The specialized protein structure on a duplicated chromosome where spindle microtubules bind during cell division.

Polar microtubules

Spindle microtubules that do not attach to chromosomes, but overlap along the equator and push the cell poles apart to cause cell elongation.

Prophase

The first phase of mitosis, characterized by chromosome condensation and kinetochore attachment to newly forming spindle microtubules.

Metaphase

The second phase of mitosis during which kinetochore microtubules align duplicated chromosomes along the equatorial plane of the cell.

Anaphase

The third phase of mitosis in which sister chromatids separate into independent chromosomes and move to opposite poles while polar microtubules elongate the cell.

Telophase

The final stage of mitosis during which chromosomes decondense and nuclear envelopes re-form around each newly segregated set of daughter chromosomes.

Cytokinesis

The division of the cytoplasm into approximately equal halves, occurring by microfilament pinching in animal cells and Golgi vesicle fusion in plant cells.

Cyclin-dependent protein kinases (Cdks)

Key regulatory enzymes that interact with cyclins to drive and control eukaryotic cell cycle progression.

Cell cycle checkpoints

Three major regulatory feedback points (between $G_1$ and S, $G_2$ and mitosis, and metaphase and anaphase) that verify DNA integrity and chromosome alignment before division proceeds.

Stem cell

A cell that retains the capacity to divide throughout an organism's life and produces daughter cells that can differentiate into various mature cell types.

Homologues (Homologous chromosomes)

Pairs of chromosomes in diploid eukaryotic cells that carry the same genes with similar, though usually not identical, nucleotide sequences.

Alleles

Slightly different nucleotide sequences of a gene found at corresponding chromosomal locations.

Diploid

A eukaryotic cell containing paired homologous chromosomes (two copies of each type of chromosome).

Haploid

A cell possessing only a single copy of each type of chromosome, characteristic of gametes produced by meiotic division.

Polyploid

A cell condition characterized by having three or more copies of each type of homologous chromosome.

Meiotic cell division

A specialized division sequence consisting of meiosis followed by cytokinesis that separates homologous chromosomes to yield four genetically variable haploid daughter cells.

Crossing over

The reciprocal exchange of DNA between chromatids of homologous chromosomes during prophase I of meiosis, creating novel combinations of alleles.

Prophase I

The opening stage of meiosis I in which duplicated homologous chromosomes pair up and undergo crossing over.

Autosomes

Chromosomes that are found in every cell of both males and females, distinct from sex chromosomes.