ap biology | cell communication + cell cycle [UNFINISHED]

ligand

a chemical signal that triggers a specific cellular response

three main steps of signal transduction

reception, transduction, response

autocrine signaling

the cell that secreted the ligand binds to a receptor + triggers a response on the same cell

juxtacrine signaling

direct contact between the cell sending the ligand and the cell receiving the ligand

paracrine signaling

ligand travels a short distance

effects cells in the immediate area

endocrine signaling

ligands (hormones) travel a long distance between the sending and receiving cells

ligands that travel a long distance are

hormones

hydrophilic ligands ___ cross the phospholipid bilayer

cannot

hydrophilic ligands bind to the

cell membrane receptors

target cells

cells that respond to the presence of the ligand

hydrophobic ligands bind to

intracellular receptors in the cytosol

reception

ligand binds to a specific receptor on or in the target cell

(receptor must be specific to the ligand)

receptor changes shape upon binding

transduction

series of chemical reactions that help the cell choose the appropriate response

possible components of transduction

signal amplification

kinases

phosphatases

secondary messengers

signal amplification

a series of chemical reactions where one molecules activates multiple molecules, amplifying the cell’s response to a signal

kinases

enzyme that transfer phosphate groups to other molecules (activates those molecules)

phosphatases

enzymes that remove phosphate groups from other molecules (inactivates those molecules)

secondary messangers

other molecules that relay signals

produced by enzymes

adenylyl cyclase

producesthe secondary messenger cyclic AMP (cAMP) from ATP

response

final stage of signal transduction and ultimate result generated by the ligand

signal transduction pathways

series of chemical reactions that mediate the sensing and processing of stimuli

feedback mechanisms

help living organisms respond to changes in the environment while maintaining homeostasis

homeostasis

the maintenance of an organism’s stable stae

negative feedback

returns a system to its original condition

cell signaling causes a person to release sweat when they become to hot, which helps them cool back down. what kind of feedback mechanism is this?

negative

the pancreas releases insulin when blood levels are too high. insulin is a ligand that triggers a series of chemical reactions upon binding that causes cells to absorb glucose from the blood. what kind of feedback mechanism is this?

negative

the pancreas releases glucagon when blood levels are too low. insulin is a ligand that triggers a series of chemical reactions upon binding that causes liver cells to break down glycogen into glucose, releasing glucose into the blood. what kind of feedback mechanism is this?

negative

positive feedback

magnifies cell processes

the hormone oxytocin stimulates contraction of the uterine muscle in labor interaction during childbirth. the contractions triggers production of even more oxytocin, which increases the contracts of the uterine muscles further. what kind of feedback mechanism is this?

positive

positive feedback ____ deviation from homeostasis

increases

negative feedback ___ deviation from homeostasis

decreases

three phases of the cell cycle

interphase

mitosis

cytokinesis

what are the stages of interphase?

g1, s, g2

what is stage g0?

the stage nondividing cells enter after leaving the cell cycle

what’s the longest phase of the cell cycle?

interphase

what happens during interphase?

the cell grows so that it has enough material to divide between two daughter cells

(replicates dna)

what happens during g1?

the cell grows and prepares for dna replication

some cell organelles are replicated

what happens during the s (synthesis) stage?

dna is replicated

contains double the dna but the same amount of chromosomes

each chromosome ; one chromatid → two identical chromatids held together by one centromere

what happens during the g2 stage?

the cell continues to grow and prepares the materials needed for mitosis