molecular exam 2

Cytoskeleton

Network of filaments and tubules in cytosol.

Cell shape

Maintained by cytoskeletal structures.

Cell movement

Driven by cytoskeletal dynamics.

Cell division

Cytoskeleton aids in chromosome separation.

Organelle trafficking

Transport of organelles via cytoskeletal pathways.

Cell signaling

Cytoskeleton involved in signal transduction.

Cell-cell adhesion

Cytoskeleton supports intercellular connections.

Cytoskeletal proteins

Polymers formed from protein monomers or dimers.

Microtubules

Hollow cylinders aiding in cell shape and movement.

αβ-tubulin dimers

Subunits that polymerize to form microtubules.

GTP

Nucleotide required for microtubule polymerization.

+ end

Growth end of microtubules.

- end

Anchored end of microtubules.

Protofilaments

Linear polymers of αβ-tubulin dimers.

Treadmilling

Dynamic process of assembly and disassembly at ends.

Catastrophe

Rapid disassembly of microtubules.

Microtubule drugs

Agents affecting microtubule dynamics in treatments.

Colchicine

Inhibits microtubule assembly by binding β-tubulin.

Nocadazole

Prevents polymerization by binding β-tubulin.

Vinblastine

Aggregates αβ-tubulin heterodimers, stabilizing microtubules.

Paclitaxel (Taxol)

Stabilizes microtubules, preventing disassembly.

Microtubule Organizing Centers (MTOCs)

Sites for microtubule nucleation and anchoring.

Centrosome

Primary MTOC in animal cells.

Basal bodies

MTOCs for cilia and flagella.

Golgi

Involved in vesicle/organelle trafficking.

Microtubule-binding proteins

Stabilize or destabilize microtubules.

MAPs

Microtubule-associated proteins that stabilize microtubules.

Tau protein

A MAP essential for neuronal structure.

Microfilaments

Thin filaments made of actin involved in movement.

G-actin

Monomeric form of actin.

Microfilament polymerization

G-actin binds ATP to form filaments.

+ end (microfilaments)

Barbed end of actin filaments.

- end (microfilaments)

Pointed end of actin filaments.

Actin binding proteins

Regulate actin filament dynamics.

Stress fiber

Rigid actin structure for stability.

Cortical fiber

Flexible actin structure for shape.

Lamellipodium

Crawling structure formed by actin.

Filopodium

Thin, protruding actin structure.

GTPases

Regulate actin remodeling via GTP binding.

Listeria monocytogenes

Bacteria utilizing host actin for movement.

Intermediate filaments

Stable filaments formed from protein dimers.

Dimers

Two proteins joined to form intermediate filaments.

Staggered pattern

Arrangement of intermediate filament subunits.

Membrane function

Separates cell interior from exterior environment.

Membrane proteins

Regulate movement of molecules across membranes.

Receptor proteins

Bind chemical signals and transmit messages.

Cell-to-cell interactions

Facilitate adhesion and communication between cells.

Energy storage

Creates voltage by separating charges.

Fluid Mosaic Model

Describes membrane structure with lipids and proteins.

Phospholipids

Most common membrane lipid, forms bilayer.

Sterols

Four-ringed hydrocarbons, stabilize membrane fluidity.

Glycolipids

Lipids with carbohydrate heads, determine blood types.

Membrane fluidity

Movement of phospholipids affects membrane state.

Transition temperature (Tm)

Temperature where membrane changes from gel to fluid.

Desaturase enzymes

Modify fatty acids by adding double bonds.

Membrane asymmetry

Different lipids on inner and outer leaflets.

Flippase

Protein that moves phospholipids between membrane sides.

Integral proteins

Span the membrane, involved in transport.

Peripheral proteins

Loosely attached to membrane, provide structural support.

Lipid-anchored proteins

Tethered to the membrane via lipid tails.

Lipid raft

Membrane section rich in cholesterol and sphingolipids.

Selectively permeable

Controls passage of ions and small molecules.

Concentration gradient

Difference in substance concentration across a membrane.

Electrochemical potential

Charge and concentration difference across a membrane.

Membrane potential (Vm)

Electrical potential difference maintained around -60 mV.

Simple diffusion

Molecules pass freely following concentration gradient.

Facilitated diffusion

Polar molecules move via channel or carrier proteins.

Active transport

Requires energy to move substances against gradient.

Channel proteins

Transmembrane proteins allowing specific ion passage.

Carrier proteins

Bind and transport specific substances across membranes.

Antiporter

Moves two molecules in opposite directions.

Symporter

Moves two molecules in the same direction.

Aquaporins

Channel proteins specifically for water transport.

Sodium-potassium pump

Active transport mechanism for Na+ and K+.

Membrane protein mobility

Variable movement, can be anchored or free.

Fluid state

Membrane condition allowing lateral lipid movement.

Rigid state

Membrane condition restricting lipid movement.

High temperature effect

Increases membrane fluidity, may destabilize structure.

Low temperature effect

Decreases membrane fluidity, may solidify structure.

Glycerol backbone

Structural component of phospholipids.

Sphingosine backbone

Alternative backbone for some membrane lipids.

Blood type determination

Based on glycolipid composition on cell membranes.

Membrane signaling

Communication initiated by receptor protein activation.

Chemical signals

Molecules that trigger cellular responses.

Cellular adhesion

Process by which cells stick to each other.

Membrane transporters

Proteins that facilitate movement across membranes.

Hydrophobic core

Barrier preventing polar molecules from passing.

Phospholipid bilayer

Basic structural unit of cell membranes.

Membrane structure

Composed of lipids, proteins, and carbohydrates.

Central Dogma

Flow of genetic information: DNA → RNA → protein.

Translation

Process of converting RNA into polypeptides.

Codon

Three RNA nucleotides encoding an amino acid.

Stop Codon

Signals termination of protein synthesis.

Start Codon

Initiates translation; usually AUG (Methionine).

Amino Acid

Building blocks of proteins; 20 types exist.

tRNA

Transfer RNA; connects mRNA codon to amino acid.

Aminoacyl-tRNA Synthetase

Enzyme linking amino acids to tRNA; requires ATP.

Ribosome

Complex of rRNA and proteins; site of translation.

mRNA

Messenger RNA; carries genetic information from DNA.

Peptide Bond

Covalent bond linking amino acids in a protein.