lecture 8 & 9 bio 202

what cellular responses are induced by cAMP?

• enzyme activation, gene expression change, & ion channel regulation

what is Calmodulin? where is calmodulin found in the cell? what happens following the binding of Ca2+ to calmodulin?

• a small calcium-binding regulatory protein that helps control many cellular processes.

• Ca2+ bind to calmodulin in the cytosol → produces shape change in calmodulin.

what are the two types of competitors? what effect does each have?

• agonists: activates a response

• antagonist: blocks a response

how do receptors that activate/ phosphorylate a docking protein function?

• bind to ligand→ receptors

• phosphorylates itself→ docking

• protein attach → triggers

• intracellular signaling pathways

how does Janus Kinase function?

• first messenger binds the receptors→ changes shape of receptors and phosphorylates target proteins

how is cAMP produced?

• when ligands activate a G-protein→ adenylyl cyclase converts ATP to cAMP

what does cAMP do once activated in the cell?

• activates protein Kinase A(PKA) which phosphorylates proteins to change cell activity.

what is signal amplification? why is this important within the cell?

• one messenger bind activates many molecules.

• it is important because it allows a small signal to produce a large cellular response efficiently.

what is a signal transduction pathway?

• the diverse sequence of events that follow receptor activation.

what are lipid soluble messengers? where do they bind? what effect do they have on the cell?

• they are signaling molecules like steroid hormones that can diffuse through the cell membrane.

• they bind inside the cell.

• gene expression by turning specific genes on or off leading to change in protein synthesis.

what are water soluble messengers? where do they bind?

• they are signaling molecules like peptide hormones that cannot pass through the cell membrane.

• bind to receptors on the cell surface membrane.

be able to identify types of water soluble messengers.

• peptide/ protein hormones

• amino acids derived hormones neurotransmitters

where do first messengers bind? where are second messengers found?

• first: bind to receptors on the cell membrane surface.

• second: are found inside the cell cytoplasm and carry the signal further.

know the function of protein Kinases.

• function: turn proteins on or off helping pass along and regulate cell signals.

how do ligand gated ion channels function?

• they function by binding channel-changes shape ion flow in or out of the cell.

what activates phospholipase C? what does phospholipase C do in the cell? what are the effects of IP3? what are the effects of DAG?

• Gq activates Phospholipase C.

• catalyzes the breakdown of (PIP2)→ DAG & IP3

• IP3: Ca2+ moves down its concentration gradient into the cytosol & triggers a cascade of events.

• DAG: activates protein kinase C Phosphorylates other protein in the cell( similar to cAMP).

what are 3 ways the activity of signal transduction pathways can be ceased?

1. elimination of first messenger

2. inhibitory phosphorylation

3. receptors undergoes endocytosis and is taken into the cell.

where are receptors found? what happens after the ligand binds?

• found in the messenger/ligand bind.

• it activates the receptors and triggers a cellular response, starting a signal transduction pathway that leads to a specific change in the cell.

where does the ligand bind on plasma membrane receptor?

• specific binding site on the extracellular side of the plasma membrane receptor.

where are intracellular receptors?

• found within the cytosol or nucleus

what is saturation? how can saturation be increased and decreased?

• percent of available binding sites that are bound to their ligand.

• increase: by increasing the concentration of ligand

• decrease: by lowering the concentration of ligand

what is down-regulation? when would down-regulation occur?

• removal of receptors

• occurs by following high extracellular messengers concentration.

what is up-regulation? when would up-regulation occur?

• addition of receptors.

• occurs by following prolonged to extracellular messenger concentration

how do G-protein coupled receptors work? know the general structure of G-protein. what does each subunit do? how is this signal transduction pathway inactivated?

• GPCR works when a ligand activates the receptor, causing GDP on the G-protein alpha subunit to be replaced with GTP.

• subunits and what each do

  • Alpha subunit: binds guanosine

    diphosphate (GDP) and guanosine

    triphosphate (GTP)

  • Beta and gamma subunits: anchor alpha subunit in the membrane

• The pathway stops when the alpha subunit breaks down GTP into GDP. This makes the alpha subunit inactive, and it rejoins the beta and gamma subunits, turning the signal off.