exam 3 (cell signalling)

Question 1

what are ligands

Answer 1

chemical signals of certain cells that are secreted into the extracellular space. a particular ligand associates with the proper receptor

Question 2

how are different types of signaling distinguished

Answer 2

by the distance the ‘chemical message’ travels through the organism before it reaches the target cell.

Question 3

what is paracrine signaling

Answer 3

signaling when cells are in close proximity to one another, used by groups of cells to coordinate their activities (especially during development)

Question 4

describe paracrine signaling in spinal cord development

Answer 4

• notochord (hollow tube of cells) and floor plate (parallel column of cells) release a molecule, Sonic hedgehod (Shh)
• cells close to the notochord and floor plate receive a lot of Shh, while those farther away receive less

Question 5

what are morphogens

Answer 5

molecules with dose-dependent effects that form gradients, like Shh

Question 6

what is synaptic signaling

Answer 6

paracrine signaling in the nervous system

Question 7

explain the process of synaptic signaling

Answer 7

• when a neuron fires, an electrical impulse travels down a long tube–axon
• when the impulse reaches the synapse (area between sending and receiving neurons, it induces release of neurotransmitters
• neurotransmitters bind to receptor cells on the receiving cell and alter its physiological state

Question 8

what is autocrine signaling

Answer 8

cells talking to themselves, which helps reinforce cellular identity (important with cancer)

Question 9

what is endocrine signaling

Answer 9

cells that talk over distance to each other

Question 10

explain the process of endocrine signaling

Answer 10

molecules are produced by specialized cells in one part of the body (aka hormones) to take on a specific function, such as pituitary gland releases growth hormone to promote bone and cartilage growth

Question 11

what is cell-cell contact signaling

Answer 11

when a cell talks to another cell via physical linkage (aka juxtacrine signaling)

Question 12

explain cell-cell contact signaling in context of animals

Answer 12

• animal cells use small, water-filled gap junctions to transmit small signaling molecules (such as calcium ions)
• larger molecules like proteins can’t get through without help
• helps share info about a cell’s current state with its neighbor

Question 13

explain cell-cell contact signaling in context of the immune system

Answer 13

2 cells may communicate based on presence of complementary proteins on their surface
-important where natural killer cells recognize specific markers on the body’s own cells that are not present on pathogen cells

Question 14

what results when a ligand binds with a receptor cell

Answer 14

binding triggers a cascade of chemical events that ultimately results in cellular response

• alters gene expression
• changes metabolism
• programmed cell death (apoptosis)

Question 15

what are intracellular receptors and their function

Answer 15

• receptors that are intracellular or on cell surface
• tend to bind to hydrophobic molecules, so they can cross the hydrophobic plasma membrane
• unique that they bind directly to DNA and act as transcription factors
• example of this, steroids

Question 16

what are G protein coupled receptors (GPCRs) and their processed function

Answer 16

• cell surface receptors that recognize many different ligands
• G proteins hydrolyze GTP to GDP, making it inactive
• involved in 2 major pathways: cAMP and Phosphatidylinositol

Question 17

what are receptor tyrosine kinases (RTKs) and their process function

Answer 17

• enzyme-linked cell surface receptors
• once binded to a ligand, receptors come together (dimerize) and phosphorylate each other, beginning a signaling cascade
• involved in cellular response to growth factors and other protein ligands

Question 18

what are signaling transduction pathways

Answer 18

when a ligand binds to a extracellular receptor, it sets in motion a sequence of signaling events culminating in a specific cellular response

Question 19

what is miotgen-activated protein (MAP) kinase pathway

Answer 19

• form of phosphorylation-dependent pathway, major signal transduction mechanism
• mitogen is a signal that cells to divide via mitosis (example of one: EGF)

Question 20

non-protein signaling: lipids and calcium

Answer 20

membrane lipids can act as signaling molecules

• G protein coupled receptor (GPCR) signaling can release phosphatidylinositol from cell membrane
• this lease to release of caldium from ER, which continues signaling cascade

Question 21

non-protein signaling: cAMP

Answer 21

• GPCR signaling activates adenylyl cyclase
• this activates protein kinase A to continue signaling
• interaction with cAMP then activates lac mRNA transcription by binding to CRP

Question 22

whats the purpose of programmed cell death (apoptosis)

Answer 22

controlled process where cells die

• to form anatomical structures during development
• remove damaged cells in adult organism
• turnover of cell population in adult tissues
• organ sculpting
• about 50-70 billion cells die each day in an adult human

Question 23

what are caspases

Answer 23

proteases that are activated for apoptosis

Question 24

explain caspase activation

Answer 24

• cleavage of important cellular proteins

- after a certain point, caspase cascade is irreversible and must be tightly controlled

Question 25

what are the 2 signals for apoptosis

Answer 25

• intrinsic pathway: involves stress or damage to cells

- extrinsic pathway: involves ligand/receptor signaling