Cell Structure and FunctionChapter 6-10AP Biology

Warm Up Exercise

• Define phagocytosis and pinocytosis.• What does it mean for a cell to have a

concentration gradient?

Cell Signaling• Signal Transduction Pathway- a specific

cellular response as a result of a received cellular signal.

Local Signaling• Local Regulators- influence cells in the nearby

vicinity.• Paracrine Signaling- broad range- can communicate

with many cells.• Synaptic Signaling- occurs in the nervous system

(more specific)

Long Distance Signaling• Hormones- chemicals that

aide in long distance signaling- released by specialized cells and travel in the blood stream.

Three Stages of Cell Signaling• Reception- the target cell’s detection of a

chemical signaling molecule. (when the molecule binds to the receptor protein).

• Transduction- the change that occurs on the protein due to the receptor binding.

• Response- transduced signal triggers a specific cellular response.

Cell Surface Transmembrane Receptors• G Protein Coupled Receptors (GPCRs)-

signaling molecule binds to GPCR which activates it and changes its shape. GPCR then binds an inactive G protein causing GDP to convert to GTP, activating the G protein. Protein binds to enzyme, activating it- triggering the next step in a cellular response.

Cell Surface Transmembrane Receptors• Receptor Tyrosine Kinases (RTKs)- transfer

phosphates from ATP to the amino acid tyrosine.

Cell Surface Transmembrane Receptors• Ion Channel Receptors- includes a region that

acts as a fate when the receptor changes shape. Gate can open or close to allow flow of specific ions.

Intracellular Receptors• Intracellular Receptors-

found in the cytoplasm or nucleus of target cells.

Warm Up Exercise• What are the three stages of cell signaling?• What are the two types of local signaling? Which

is the strongest? • Hint: When a signal is transmitted to numerous

molecules, it is more amplified because it activates more than one molecule at the end of a pathway.

• How are long-distance signals sent?• What are the three main types of transmembrane

receptors?

Signal Transduction• Protein Kinase- enzyme that transfers

phosphate groups from ATP to a protein.• Phosphorylation- adding a phosphate (which many

times activates the protein)

Phosphorylation Cascade

Signal Transduction• Protein Phosphatase- enzyme that rapidly

remove phosphate groups from proteins, a process called dephosphorylation. • Usually inactivates protein kinases and help turn off signal

transduction pathway. Makes protein kinases available for reuse.

Second Messengers• Second Messengers- small, water-soluble, non-

protein molecules/ions involved in signaling pathways. • Cyclic AMP (cAMP)- (cyclic adenosine monophosphate)-

ATP is converted to cAMP by an enzyme (adenylyl cyclase) in the plasma membrane in response to an extracellular signal (usually a hormone).• Phosphodiesterase- reduces cAMP to AMP

Second Messengers• cAMP usually

activates protein kinase A which phosphorylates other molecules in the signal transduction pathway.

Second Messengers• Calcium (Ca2+) Ion- calcium pumps actively

transport calcium ions from the cytoplasm out of the cell or into the ER.

Warm Up Exercise

Signal Response• Signaling pathway

may regulate protein activity or synthesis.