Cell Bio Exam 2

Cytoskeleton

A complex network of interconnected filaments and tubules that extends through the cytosol.

Modularity

A fundamental feature of the cytoskeleton in which a small number of its elements are deployed in different locations to meet the particular needs of the cell.

Electron microscopy

What tool was used in the discovery of three types of filaments?

Tubulin

Protein that makes up microtubules.

25 nm

Diameter of a microtubule.

7 nm

Diameter of microfilaments

Actin

Proteins that make up microfilaments.

8-12 nm

Diameter range of intermediate filaments.

Microtubule

Hollow tube with a wall consisting of typically 13 protofilaments.

Microfilament

Two intertwined chains of F-actin.

Intermediate filament

Eight protofilaments joined end-to-end with staggered overlaps.

Septins

“The fourth cytoskeleton,” associated with the contractile ring.

MreB Protein

Actin-like protein that forms filaments perpendicular to the long axis of rod-shaped bacteria. Important in maintaining cell shape and bacterial cell division.

FtsZ Protein

Tubulin-like protein that is involved in determining whether bacterial cells will divide.

Crescentin Protein

Intermediate filament-like protein that is an important regulator of bacterial cell shape.

X-ray crystallography

Used to show the similarity in structure between eukaryotic and bacterial cytoskeletal proteins.

Cytosolic microtubules

Used to form the mitotic and meiotic spindles to move chromosomes. Also guide the movement of vesicles and organelles.

Axonemal microtubules

Highly structured, found in subcellular structures specialized for cellular movement.

Axoneme

The central shaft of a cilium or flagellum.

Protofilaments

Linear polymers that make up the wall of a microtubule.

Lumen

Hollow center of a microtubule.

13

Most common number of protofilaments found in a microtubule.

Tubulin heterodimer

Basic subunit of a protofilament.

Guanosine triphosphate

What binds to the N-terminus of a tubulin heterodimer?

Colchicine

Microtubule poison that can bond at the center domain of a tubulin heterodimer.

C-Terminus

Terminus in a tubulin heterodimer that is capable of interacting with MT-associated proteins.

Spectraplakins

Linker proteins that connect intermediate filaments, microfilaments, and microtubules.

Singlet

Simple microtubule tube made from 13 protofilaments, found in cytoplasm.

Doublet

Microtubule with one complete protofilament cylinder and one incomplete cylinder. Found in cilia and flagella.

Triplet

Microtubule with one complete protofilament cylinder and two incomplete cylinders. Found in centrioles and basal bodies.

Plateau Phase

When the mass of microtubules reaches a point where the amount of free tubulin is diminished; the assembly is balanced by disassembly.

Plectin

Found at sites where intermediate filaments connect to microfilaments and microtubules.

Italicize

How genes are differentiated from proteins in writing.

Capitalization

How human genes and proteins are differentiated from other organisms.

TUBA1A

Gene that codes for α-tubulin.

TUBB2B

Gene that codes for β-tubulin.

Sarcomere

Alternating bands that form striations.

Muscle specific

α-actin is ___.

Apical side

Where β-actin is found on epithelial cells.

Basal side

Where γ-actin is found on epithelial cells.

Microtubule inner proteins

Proteins that stabilize doublets and triplets, lines the interior of fused microtubules.

37 C

Temperature needed for polymerizatioin of tubulin dimers.

Spectrometer

Instrument used to measure MT formation in a solution.

Oligomers

The aggregation of tubulin dimers into clusters that MTs can grow from.

Nucleation

The act of providing a small aggregate of molecules from which a polymer can grow.

Elongation

The addition of subunits at either side of a nucleated MT.

Plus end

The growing end of a microtubule.

Minus end

The non-growing end of a microtubule.

Centrosome

Where the minus end of a MT is often anchored.

Motility

Movement of a cell or organism through its environment.

Contractility

The shortening of muscle cells, a special form of motility.

Cell body

Location of Rough ER in a neuron.

Kinesin

ATP-dependent motor protein that transports towards the positive end of a microtubule (away from nucleus).

Dynein

Transport protein that moves particles away from the positive end of a microtubule.

Anterograde

Golgi Complex to cell surface.

Retrograde

Cell surface to Golgi Complex.

Centrosome

Serves as an anchor to the polarized array of microtubules with the (+) end at the cell periphery and the (-) toward the microtubule organizing center.

Mother

From which parent is the mitochondria inherited?

Cilia

Short hair-like structures that occur in large quantities. Uses oarlike motion to propel cells forward.

Myosin

Motor protein used for microfilament movement. Mostly moves to the positive end of a microfilament.

Sliding Filament Model

Muscle contraction is due to thin filaments sliding past thick filaments, with no change in length of either.

Thin filaments

Makes contact with at least three proteins: F-actin, tropomyosin, and troponin.

Thick filament

Consists of hundreds of molecules of myosin, oriented in opposite directions in the two halves of the filament.

Sarcomere

The basic contractile unit of muscle fiber.

Tropomyosin

Covers myosin-binding sites on actin.

Troponin

Binds to Ca2+ and can hold tropomyosin.

TITIN

Anchors Z-disc to M-line

Dystrophin

Links sarcomere to sarcolemma.

Fluid Mosaic Model

The membrane made up of protein molecules bobbing in a fluid bilayer of phospholipids.

Phospholipid

Most abundant lipid in cell membrane; consists of a hydrophilic head and two hydrophobic tails.

Viscous

As temperatures cool, membranes become more ___.

Unsaturated fatty acids

Membranes consisting of ___ are more fluid.

Warm

Temperature cholesterol restrains the movement of phospholipids.

Cool

Temperature cholesterol maintains fluidity by preventing tight packing.

Membrane

Defines the boundaries of a cell and its internal compartments.

Lamella

Thin sheets.

Beta barrels

Beta sheets wrapped around like a barrel. Allows hydrophilic materials to pass through the hydrophobic part of the cell membrane.

Cholesterol

Animal plasma membranes.

Phytosterol

Plant plasma membranes.

Ergosterol

Fungi plasma membranes.

Thin layer chromatography

Method to separate different kinds of lipids based on their relative polarities.

Flippase

Moves things from outer to inner membrane.

Floppase

Moves things from inner to outer membrane.

Lateral diffusion

Movement of phospholipids within the monolayer.

Electrochemical Potential

The movement of an ion by the combine effect of its concentration gradient and the charge gradient across the membrane.

Concentration Gradient

The movement of a molecule that has no net charge.

Transport protein

Allows passage of hydrophilic substances across the membrane.

Channel protein

Has a hydrophilic channel that certain molecules or ions can use as a tunnel.

Aquaporin

A channel protein that greatly facilitates the passage of water molecules.

Simple diffusion

The direct unaided movement dictated by differences in concentration of the solute on the two sides of the membrane.

Facilitated diffusion

Type of passive (energy-free) transport that moves molecules down their concentration gradient across a cell membrane with the help of transmembrane proteins, e.g. channels or carriers.

Active transport

A type of transport that requires energy such as that released by the hydrolysis of ATP or by the simultaneous transport of another solute down an energy gradient.

Isotonic

A solution has equal concentration of solvent and solute.

Hypertonic

A solution has a higher solute concentration.

Hypotonic

A solution has a lower solute concentration.