Quiz 8 Biology Lecture 11-13

Notch

receptor, transmembrane proteins, Delta's receptor, Cells become glial cells

Delta

signaling molecule

Receptor

protein receives & interprets info. carried by signaling molecule ligand

Ligand

Binds to ligand-binding sit on receptor

Intracellular Receptors

- Receptor + Ligand
- non-polar signaling molecules

Cell Surface Receptors aspects

- Use polar signaling molecules
- G Protein-Couple Receptors

G-protein + GTP

active

G-protein + GDP

inactive

G-Protein Subunits

alpha, beta, gamma

Termination of G protein signal

Amount of time a signaling molecule remains bound to its receptor depends on how tightly the receptor hold on to it, its binding affinity for the signaling molecule

Kinase

an enzyme that catalyzes the transfer of a phosphate group from ATP to a specified molecule.

Ras + GDP

inactive

Ras + GTP

active

ion channels

channel proteins that transport ions

Signaling Molecule

The carrier of information transmitted when the signaling molecule binds to a receptor; also referred to as a ligand.

Responding Cell

the cell that receives information from the signaling molecule

ignaling Steps

receptor activation, signal transduction, termination

Receptor Activation

signaling molecule binds to receptor

signal transduction

A series of molecular changes that converts a signal on a target cell's surface to a specific response inside the cell.

G-protein coupled receptors

A special class of membrane receptors with an associated GTP binding protein; activation of a G protein-coupled receptor involves dissociation and GTP hydrolysis

termination

cellular response is stopped

Pneumococcal Cells

peptide binds to and activates a receptor on the cell surface

distance between cells: far

the signaling molecule is transported by the circulatory system.

what is the distance for endocrine signaling and where does it travel

far & the bloodstream

distance between cells: short

signaling molecule simply moves by diffusion

what is the distance for paracrine signaling and where does it travel

short & nearest neighboring cell to bind its receptor and deliver its message

Neurotransmitters

released from neuron, short range signlaing

autocrine signaling

Signaling between different parts of one cell; the signaling cell and the responding cell are one and the same.

Direct Cell-Cell Contact

the signal and the receptor are both surface molecules

Ligand Binding Site

the specific location on the receptor protein where a signaling molecule binds, bond is noncovalent & specific, causes a conformation change

Growth Factors

Small & polar proteins cannot pass through hydrophobic core of plasma membrane, located on the otuside

Nonpolar Signaling Molecules

pass easily through the hydrophobic core of the phospholipid bilayer and into the target cell

Cell Surface Receptors

G-protein, kinase, ion channels

G Protein

A protein that binds to the guanine nucleotides GTP and GDP.

Phosphatases

An enzyme that removes a phosphate group from another molecule (dephosphorylation occurs and becomes inactive & switches off)

Ligand-Gated Ion Channels

ion channels open when bound by their ligand

Adenylyl Cyclase

GTP-bound α subunit then binds to and activates an enzyme in the cell membrane, converts the nucleotide ATP into cyclic AMP (cAMP)

Second Messenger

An intermediate cytosolic signaling molecule that transmits signals from a receptor to a target within the cell (ex: cyclic AMP)

Signaling Pathways

a series of protein interactions that initiate a cellular response

PDGF

platelet derived growth factor, binds to the extracellular portion of two receptors at once, causing the receptors to partner, or dimerize, with each other.

PKA

protein kinase A, activated by the G protein-coupled receptor pathway

Which of the following best describes the extracellular matrix?

A network of proteins & polysaccharides outside the cell that play a role in structural support

Some cytoskeletal elements are more permanent than others. Which components of the cytoskeleton are dynamic structures?

Both microtubules & microfilaments.

What would happen in a cell if its 𝛼-tubulin was mutated & unable to bind to is 𝛽-tubulin?

the cell would have no microtubules.

Dynamic instability is the rapid assembly & disassembly of which of the following?

Microtubules.

If intermediate filaments were capable of dynamic instability, which of the following outcomes would be most likely?

Cell adhesion would be affected.

Which one of the following pairs includes cell junctions that perform similar functions?

plasmodesmata & gap junctions

Animals - 4 Tissues

Epithelial, Connective, Nervous, Muscle

Cytoskeleton

eukaryotes, an internal protein helps cells maintain their shape & serves as a network of tracks for the movement of substances within cells.

Cell Junctions

A complex of proteins in the plasma membrane where a cell makes contact with another cell or the extracellular matrix.

Extracellular Matrix

A meshwork of proteins and polysaccharides outside the cell; the main constituent of connective tissue.

Epidermis

ater-resistant, protective barrier, contains melanocytes

dermis

supports the epidermis both physically and by supplying it with nutrients and provides a cushion surrounding the body

Connective Tissue

tissue characterized by few cells and substantial amounts of extracellular matrix

Epithelial Cells

skin cells that cover the outside of the body and line the internal surfaces of organs

Epithelial Tissue

A body tissue that covers the surfaces of the body, inside and out

Epidermal Layer

composed of keratinocytes (epithelial cells)

Keratinocytes

protect the underlying tissues and organs due to their cytoskeletal filaments

what does the cell junction connect?

bottom layer of keratinocytes to basal lamina

Basal Lamina

specialized form of extracellular matrix that underlies and supports all epithelial tissues; also called a basement membrane.

The most likely reason(s) a metastatic tumor cell might lose its connection to the basal lamina would be:

a change in the integrin proteins from the cell's surface.

Imagine that you are examining a mouse that does not produce basal lamina in the skin. How will this mouse be different from a normal, wild-type mouse?

The cells of the epidermis would not be properly connected to form a water-resistant barrier.

Microtubules

A hollow, tubelike polymer of tubulin dimers that helps make up the cytoskeleton, maintain cell shape & internal structure

Microfilaments

helical polymer of actin monomers, present in various locations in the cytoplasm, that helps make up the cytoskeleton, form strong, cable-like filaments that provide animal cells with mechanical strength.

Polymers of protein dimers

𝛼-tubulin (alpha) & 𝛽-tubulin (beta)

Centrosome

A structure in animal cells containing centrioles from which the spindle fibers develop.

Cell Cortex

area of the cytoplasm just beneath the plasma membrane

Cortical Microfilaments

maintaining the shape of a cell: biconcave shape of red blood cells

Protein Subunit added Rate; high concentration

microtubules and microfilaments can become longer at both ends and subunits assemble more quickly on one end than the other

Dynamic Instability

Cycles of polymerization and depolymerization in microtubules.

Motor Proteins

Any of various proteins that are involved in intracellular transport or cause muscle contraction by moving the actin microfilaments inside muscle cells

Two Motor Proteins

kinesin and dynein

Kinesin

similar in structure to myosin, that transports cargo toward the plus end of microtubules.

Dynein

carries cargo away from the plasma membrane toward the minus ends of microtubules.

Which motor protein(s) participate in the movement of melanin granules in melanophores?

both kinesin & dynein

What is true about myosin & kinesin?

both use energy of ATP

Melanophores

specialized skin cells

Lamins

The type of intermediate filament found inside the nucleus.

Microfilaments subunits

actin

A researcher is studying a population of mutant fibroblasts that fail to flatten and attach to extracellular matrix proteins on a flat surface. This is likely the result of mutations in genes encoding:

components of cell junctions.

Cell Adhesion Molecules

A cell-surface protein that attaches cells to one another and to the extracellular matrix.

Cadherins

A calcium-dependent adherence protein, important in the adhesion of cells to other cells in animals.

Cadherins bind to which type of cytoskeleton element?

both intermediate filaments & microfilaments

Integrins

A transmembrane protein, present on the surface of virtually every animal cell, that enables cells to adhere to the extracellular matrix.

Anchoring Cell Junctions

adherens junction, desmosome, hemidesmosome

Adherens Junctions

A beltlike junctional complex composed of cadherins that attaches a band of actin to the plasma membrane.

Desmosomes

A buttonlike point of adhesion that holds the plasma membranes of adjacent cells together.

Hemidesmosome

A type of desmosome in which integrins are the prominent cell adhesion molecules.

Tight Junctions

A junctional complex that establishes a seal between animal cells so that the only way a substance can travel from one side of a sheet of epithelial cells to the other is by moving through the cells by a cellular transport mechanism.

Which cell junction creates a barrier between cells?

tight junctions

tight junction Two Distinct Regions

Apical Membrane & Basolateral Membrane

Apical Membrane

portion of the plasma membrane in contact with the lumen, or the inside of any tubelike structure such as the gut

Basolateral Membrane

defines the bottom ("baso") and sides ("lateral") of the cell

gap junctions

ring of connexin proteins connects to similar rings on adjacent cell to from channel between the cells, allows movement of substances from cell to cell

Plasmodesmata

are passages through the cell walls of adjacent plant cells

extracellular matrix

provides the molecular framework that helps determine the structural architecture of plants and animals.

Plant Cell Wall

extracellular matrix forms the cell wall, main component = polysaccharide cellulose, maintain the shape and turgor pressure

cell wall layers

primary cell wall, middle lamella, secondary cell wall

Collagen

structural protein found in the skin and connective tissue

How many somatic cells do humans have?

46