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Amphipathic

def: molecules (like lipids) which have both hydrophobic and hydophilic properties

useful for aqueus environments.


Adaptation (chapter 16)

def: Adjustment of sensitivity of a cell or organism following repeated stimulation. Can allow a response even when there is a high background level in stimulation.

what do:
Basically it allows cells to respond to messages whispered and messages that are shouted.


Adenylyl cyclase (chapter 16)

def: Enzyme that catalyzes the formation of cyclic AMP (cAMP) from ATP. An important component of some intracellular signaling pathways.

what do:
when the adenylyl cyclase is turned on (ooh la la) via the activated G-protein alpha subunit, it causes a sudden spike increase in the synthesis of cAMP from ATP.

/Translation: Adenylyl cyclase increases the level of cAMP (which is a second messenger responsible for transferring the effects of hormones, which cannot pass through the cell membrane) from energy inside the cell (the ATP).


Actin filament (chapter 17)

def: Protein filament about 7nm wide, formed from a chain of globular actin molecules. A major constituent of the cytoskeleton of all eukaryotic cells and especially abundant in muscle cells.

what do:
they are responsible for cell movements. Many of them are unstable, but can have a stable structure by associating with other proteins.

Physical Description:
Each filament is a twisted chain of identical globular actin molecules, all of which "point" in the same direction along that axis of the chain. They are also polar (+ end and - end).
They are thinner and more flexible than microtubules, but there's also more of them within the cell.


Alternative Splicing (chapter 7)

def: Splicing of RNA transcripts from the same gene in different ways, each of which produces a distinct protein.

what do:


Aminoacyl-tRNA Synthase (chapter 7)

def: Enzyme that attaches the correct amino acid to a tRNA molecule to form aminoacyl-tRNA.

what do:


Anticodon (chapter 7)

def: Sequence of three nucleotides in a transfer RNA molecule that is complementary to the three-nucleotide codon on a messenger RNA molecule; each anticodon is matched to a specific amino acid covalently attached elsewhere on the transfer RNA molecule.

what do:


Activator (chapter 8)

def: A protein that binds to a specific regulatory region of DNA to permit transcription of an adjacent gene.


Anaphase (chapter 18)

def: Stage of mitosis during which the two sets of chromosomes separate and move away from each other. Composed of anaphase A (chromosomes move toward the two spindle poles) and anaphase B (spindle poles move apart).


Anaphase-promoting Complex (APC) (chapter 18)

def: A protein complex that promotes the destruction of specific proteins, by catalyzing their ubiquitylation. It is a crucial component of the cell-cycle control system.


Apoptisis (chapter 18)

def: Normal, benign type of programmed cell death in which a cell shrinks, fragments its DNA and alters its surface so as to activate the phagocytosis by macrophages.


Aster (chapter 18)

def: Star-shaped system of microtubules emanating from a centrosome or from a pole of a mitotic spindle.


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