AP Bio Signal Transduction Quiz

Communication involves…

• transduction of stimulatory or inhibitory signals from other cells, organisms or environment.

Signal transduction pathways include…

• protein modification

• phosphorylation cascades

Correct and appropriate signal transduction are…

• under strong selective pressure (intense environmental factors that heavily favor one trait over another, drastically increasing survivor and reproduction rates)

Signal transmission within and between cells…

• mediate cell function

  • mating phermones in yeast triggering mating genes

  • morphogens stimulate cell differentiation and development

Intercellular and intracellular signal transmisions…

• mediate gene expression

  • cytokines regulate gene expression to allow for cell replication and division

Three stages of cell signaling…

• reception:

  • signaling cells release signal molecule, ligand, to bind to target cell receptor.

• transduction:

  • message is transmitted via a series of relay molecules (proteins) to the interior of the cell.

• response:

  • transduction results in a specific cellular action.

Signaling…

• begins with recognition of a chemical messenger, a ligand, by a receptor protein in or on a target cell

• ligand binding domain of a receptor recognizes a specific chemical messenger

• different receptors recognize different, specific ligands

• reception causes change in shape of receptor protein’s intracellular domain and this initiates transduction of signal.

Reception…

• ligand - receptor interaction “lock and key”

• as soon as message is relayed, ligand and receptor interaction is terminated to get new signals.

Types of receptors…

• Intracellular receptors:

  • ligands are hydrophobic, small, non-poplar (steroids), can easily cross cell membrane.

• Transmembrane receptors:

  • lignads are hydrophilic, large, polar, charged (proteins), can not easily pass through membrane.

Signalling cascasdes…

• relay signals from receptors to cell targets

• often amplify the incoming signals

• results in appropriate response by cell

Receptors…

• G protein coupled receptors

• ligand gated channels

• receptor tyrosine kinases

Conversion to a cellular response…

• signaling cascades relay signals from receptors to cell targets, often amplifying the incoming signals with an appropriate response.

• second messengers are molecules that relay and amplify the intracellular signal

  • cGMP, cAMP, calcium ions, inositol triphosphate

Transduction (phosphorylation)…

• domino effect on relay proteins

• change in one protein triggers change in the next protein and that one for the next one

• usually accomplished by adding or removing phosphates.

Phosphorylation cascades…

• series of steps in which protein kinase add a phosphate group to the next protein in the cascade sequence

Response…

• pathways influence how a cell responds to its environment

• cell responds by changes in gene expression or cell function.

• may alter phenotype

• result in apoptosis

Cell function…

• secreting/transcribing a protein

• closing or opening a channel

• breaking down glycogen

• elongating hair molecules

• ripening fruit

• proceeding into the mitotic phase

Changes in signal pathways…

• can alter cellular response

• changes in pathway can be due to

  • mutations in any domain of the receptor protein

  • mutations in any component of the signaling pathway

• affect the downstream components by altering the subsequent transduction of the signal

Timing and coordination of events…

• timing and coordination of specific events are necessary for normal development of an organism and regulatory mechanisms

  • differential gene expression

  • activation of transcription factors during development results in sequential gene expression

  • apoptosis plays an important role in development and differentiation.

Sequential gene expression (result of activating transcription factors)…

• homeotic genes are involved in developmental patterns and sequences

• embryonic induction in development results in the correct timing of events

• temperature and availability of water determines seed germination.