Unit 4 Ap Biology

Describe the ways that cells can communicate with one another.

with one another through direct contact with other cells or from a  distance via chemical signaling.

over short distances by using local regulators that target cells in the  vicinity of the signal-emitting cell.

Signals released by one cell type can travel long distances to target cells of another  cell type.

Autocrine 

self

Juxtacrine

beside, next to, touching

Paracrine

nearby

Endocrine (hormonal Signaling)

within

Synaptic

neurotransmitter, specific to nervous system

Reception

Cell membrane and receptor v.s. receptors. Ligand attaches to receptor 

Transduction

may result in changes in gene expression and cell function, which  may alter phenotype or result in programmed cell death (apoptosis). 

Changes in signal transduction pathways can alter cellular responses. Mutations in any domain of the receptor protein or in any component of the signaling pathway may affect the downstream components by altering the subsequent transduction of the signal.

Chemicals that interact with any component of the signaling pathway may activate or inhibit the pathway

GPCR

large family of cell receptors that respond to variety of external signals

G-protein activation

binding of a molecule to GPCR. Triggers the production of any numbers of second messengers.

Response

signaling pathways lead to response in the cell. Regulation of transcription, turning off or off a protein of in the cytoplasm

Second messengers

Ca+2 and cAMP. Phosphorylation cascades(protein kinase which adds phosphates to molecules and phosphatases which removes phosphates from molecules)

Signaling cascades

relay signals from receptors to cell targets, often amplifying  the incoming signals, resulting in the appropriate responses by the cell, which could include cell  growth, secretion of molecules, or gene expression—

Steps in signaling

After the ligand binds, the intracellular domain of a receptor protein changes shape  initiating transduction of the signal.  

b.Enzymes and second messengers such as cyclic AMP (cAMP) relay and amplify the intracellular signal.

c. Hormones are an example of a signaling messenger that can travel long distances in the bloodstream.

d. Binding of ligand-to-ligand-gated channels can cause the channel to open or close.

Negative feedback

mechanisms maintain homeostasis by reducing the initial stimulus to regulate physiological processes. If a system is perturbed or disrupted, negative feedback mechanisms return the system back to its target set point. These processes operate at the molecular, cellular, and organismal levels

Postive 

mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved further away from the initial set point. Amplification occurs when the stimulus is further intensified, which, in turn, initiates an additional response that produces system change.

G1

The cell is metabolically active, duplicating organelles and cytosolic components.

S-phase 

DNA is in the form of chromatin and replicates to form two sister chromatids connected at a centromere.

G2

Protein synthesis occurs, ATP is produced in large quantities, and centrosomes replicate

G0

where it no longer divides, but it can reenter the cell cycle  in response to appropriate cues. Nondividing cells may exit the cell cycle or be held at a  particular stage in the cell cycle

Prophase

Sister chromatids condense, mitotic spindle begins to form, and centrosomes move to opposite poles of the cell

Metphase

Spindle fibers align chromosomes along the equator of the cell.

Anaphase

Paired sister chromatids separate as spindle fibers pull chromatids toward poles.

Telophase

Mitotic spindle breaks down, a new nuclear envelope develops, and then the cytoplasm divides.

Cytokinesis

A cleavage furrow forms in animal cells or a cell plate forms in plant cells, resulting in two new daughter cells.

Checks through out cell cycle

A number of internal controls or checkpoints regulate progression through the cycle.  Interactions between cyclins and cyclin dependent kinases control the cell cycle

CDK

Enzymes that, when activated by cyclins, phosphorylate target proteins to trigger cell cycle regulation. are present at constant levels but require cyclin binding to become active

Cyclins

Proteins that regulate the progression of the cell cycle

Apoptosis 

programmed cell death