CM Bio Exam 2

Phase separation

The formation of distinct regions or phases within a mixture, often because components interact differently.

Sol

A colloidal mixture in which solid particles are dispersed in a liquid.

Colloid

A mixture with dispersed particles larger than molecules but small enough to remain suspended.

Universal cell components

All cells have a plasma membrane, cytosol, DNA, and ribosomes.

Coccus

A spherical or round bacterial cell shape.

Bacillus

A rod-shaped bacterial cell.

Vibrio

A curved, comma-shaped bacterial cell.

Spirochaete

A flexible, spiral-shaped bacterium.

ParA

A bacterial protein involved in positioning or segregation of DNA and cellular structures.

FtsZ

A tubulin-like protein that forms a division ring during bacterial cell division.

MreB

An actin-like bacterial protein that helps maintain cell shape.

CreS

A bacterial intermediate-filament-like protein that helps establish curved cell shape.

Bacterial membrane lipids

Typically glycerol linked to fatty acids by ester bonds.

Archaeal membrane lipids

Typically isoprenoid chains linked to glycerol by ether bonds.

Bacterial cell wall

Usually contains peptidoglycan.

Archaeal cell wall

Does not contain bacterial peptidoglycan; some archaea have pseudomurein or other wall materials.

Gram-positive bacteria

Have a thick peptidoglycan layer and generally stain purple in Gram staining.

Gram-negative bacteria

Have a thin peptidoglycan layer and an outer membrane that contains lipopolysaccharide (LPS).

Glycocalyx

A carbohydrate-rich coating outside some prokaryotic cells; can aid protection and attachment.

Capsule

A well-organized outer coating that can protect a bacterial cell and help it adhere.

Fimbriae

Short, numerous surface structures that help bacteria attach to surfaces or host cells.

Conjugating pilus

A pilus involved in transferring DNA between bacterial cells.

Contractile pilus

A pilus that can extend and retract to help a cell interact with or move across surfaces.

Bacterial flagellum

A rotating motility structure commonly powered by a proton gradient.

Archaeal flagellum (archaellum)

An archaeal motility structure powered by ATP rather than the bacterial proton-driven rotary mechanism.

Endosymbiotic theory

The idea that mitochondria and chloroplasts originated from bacteria living inside ancestral eukaryotic cells.

Evidence for endosymbiosis

Mitochondria and chloroplasts have their own DNA, bacterial-like ribosomes, divide by fission, and have double membranes.

Primary endosymbiosis

A eukaryotic cell engulfs a prokaryote, giving rise to an organelle such as a primary plastid.

Secondary endosymbiosis

A eukaryotic cell engulfs another eukaryotic cell that already contains a plastid.

Endomembrane system

A network including the nuclear envelope, ER, Golgi, lysosomes, vesicles, and plasma membrane that makes, modifies, and transports cellular materials.

Cytosol

The fluid portion of the cytoplasm in which many metabolic reactions occur.

Catabolism

Metabolic reactions that break molecules down and often release energy.

Anabolism

Metabolic reactions that build complex molecules and require energy.

Actin filaments

Thin cytoskeletal filaments involved in cell shape, movement, contraction, and cytokinesis.

Microtubules

Tubulin-based hollow cytoskeletal tubes involved in transport, chromosome movement, cilia, and flagella.

Intermediate filaments

Strong cytoskeletal fibers that provide mechanical support.

Kinesin

A motor protein that generally moves cargo toward the plus end of microtubules.

Dynein

A motor protein that generally moves cargo toward the minus end of microtubules and powers cilia/flagella bending.

Myosin

A motor protein that moves along actin filaments.

Nucleus

Membrane-enclosed compartment containing most eukaryotic DNA.

Rough ER

ER with ribosomes; synthesizes proteins entering the secretory pathway or membranes.

Smooth ER

ER involved in lipid synthesis, detoxification, and calcium storage.

Golgi apparatus

Modifies, sorts, and packages proteins and lipids for delivery.

Lysosome

An acidic, enzyme-containing compartment that digests and recycles cellular materials.

Vacuole

A membrane-bound compartment for storage, digestion, and water balance; plant central vacuoles also help maintain turgor.

Peroxisome

An organelle that carries out oxidative reactions, including fatty-acid breakdown, and detoxifies hydrogen peroxide.

Mitochondrion

Organelle that carries out much of aerobic cellular respiration and ATP production.

Chloroplast

A photosynthetic plastid that converts light energy into chemical energy.

Stroma

Fluid-filled region inside a chloroplast surrounding the thylakoids.

Thylakoid

Membrane sac in chloroplasts where light-dependent reactions occur.

Plastid

A plant/algal organelle family that includes chloroplasts and storage or pigment plastids.

Signal sequence

A short amino-acid sequence that directs a protein to a particular cellular destination.

Signal recognition particle (SRP)

Recognizes ER-targeting signal sequences and helps direct a translating ribosome to the ER.

Fluid mosaic model

Model describing membranes as fluid lipid bilayers with proteins and other components embedded or associated.

Phospholipid

An amphipathic membrane lipid with a hydrophilic head and hydrophobic tails.

Amphipathic

Having both hydrophilic and hydrophobic regions.

Integral membrane protein

A protein embedded in the lipid bilayer; many span the membrane.

Peripheral membrane protein

A protein loosely associated with a membrane surface or another membrane protein.

Membrane fluidity: tail length

Shorter fatty-acid tails generally increase membrane fluidity.

Membrane fluidity: unsaturation

More cis double bonds create kinks and generally increase fluidity.

Cholesterol

A membrane component that buffers fluidity: restrains phospholipid movement at higher temperatures and prevents tight packing at lower temperatures.

Lateral diffusion

Movement of membrane lipids or proteins within the same leaflet of the bilayer.

Flip-flop

Movement of a lipid from one membrane leaflet to the other; usually slow without enzymes.

Glycosylation

Addition of carbohydrate groups to proteins or lipids, often important for recognition, stability, and sorting.

Selective permeability

A membrane's ability to allow some substances to cross more easily than others.

Simple diffusion

Net movement of a substance down its concentration gradient without transport proteins or direct energy input.

Concentration gradient

A difference in concentration across space or a membrane that can drive net movement.

Facilitated diffusion

Passive movement down a gradient through a channel or carrier protein.

Active transport

Movement of substances against a gradient using energy directly or indirectly.

Channel protein

A membrane protein that provides a passageway for specific ions or molecules.

Carrier protein

A protein that binds a solute and changes shape to move it across a membrane.

Pump

A transport protein that uses energy to move substances, often against their gradients.

Uniporter

A transporter that moves one type of solute in one direction.

Symporter

A transporter that moves two or more solutes in the same direction.

Antiporter

A transporter that moves solutes in opposite directions.

Osmosis

Net movement of water across a selectively permeable membrane toward the side with higher effective solute concentration.

Hypertonic solution

A solution with higher effective solute concentration than the cell; water tends to leave the cell.

Hypotonic solution

A solution with lower effective solute concentration than the cell; water tends to enter the cell.

Isotonic solution

A solution with equal effective solute concentration; no net water movement.

Plasmolysis

In plant cells, the plasma membrane pulls away from the cell wall after water loss in a hypertonic environment.

Endocytosis

Uptake of material by inward budding of the plasma membrane into vesicles.

Phagocytosis

Endocytosis of large particles or cells; often called cell eating.

Pinocytosis

Endocytosis of extracellular fluid and dissolved substances; often called cell drinking.

Exocytosis

Vesicle fusion with the plasma membrane to release contents outside the cell or add membrane components.

Transcytosis

Transport of material across a cell by endocytosis on one side and exocytosis on the other.

Cell signaling

Communication in which a signal is detected by a target cell and triggers a response.

Autocrine signaling

A cell releases a signal that acts on itself or similar nearby cells.

Paracrine signaling

Local signaling to nearby cells.

Endocrine signaling

Hormonal signaling over longer distances, typically through circulation.

Synaptic signaling

Neurons release neurotransmitters across a synapse to a target cell.

Pheromone

A chemical signal released by an organism that affects members of the same species.

Allomone

A chemical signal that benefits the sender and affects another species.

Kairomone

A chemical cue that benefits the receiver, often at a cost to the sender.

Synomone

A chemical signal that benefits both sender and receiver.

Quorum sensing

Microbial communication in which cells detect population density through signaling molecules and coordinate gene expression.

Biofilm

A community of microbes attached to a surface and embedded in a self-produced matrix.

Ligand

A molecule that binds specifically to a receptor.

G protein-coupled receptor (GPCR)

A membrane receptor that activates an associated G protein after ligand binding.

Receptor tyrosine kinase (RTK)

A receptor that commonly dimerizes and phosphorylates tyrosines to initiate signaling.

Ligand-gated ion channel

A channel that opens or closes when a ligand binds.