AP Biology Unit 4

target cell

cell that receives a signal

local signaling

signaling to a cell close by

signal transduction pathways

series of steps in which cells convert internal or external signals into specific internal responses

reception

detection of an external signal molecule

transduction

signal conversion to a form that elicits a cellular response

response

specific cellular response to the signal molecule

phosphorylation cascade

enhances and amplifies signals to cells via protein kinases adding phosphate groups to other kinases, so on and so forth

ligand

binds to a specific receptor protein in a 1:1 relationship

secondary messengers

ions or non-protein molecules like cAMP, Ca²⁺, and DAG that relay and amplify intracellular signals

quorum sensing

signal mechanism used by bacteria to communicate with other bacteria to detect population density and act as a group in response to environmental changes

feedback mechanisms

used by organisms to maintain internal environments and respond to changes in the environment

homeostasis

maintenance of a stable internal environment

negative feedback loops

return a system back to its target set point after a disruption occurs

positive feedback loops

amplify a response to a stimulus until a cell response occurs

interphase

growth and preparation process of cell cycle

mitosis phase

point in the cell cycle where the nucleus divides

cytokinesis

point in the cell cycle where the cytoplasm divides; ensures equal distribution of cytoplasm to each daughter cell

G1

cell growth, synthesis of new organelles, production of DNA replication building blocks

S-phase

the cell’s DNA is copied

G2

growth continues, synthesis of organelles (ex. microtubules), duplication of centrosomes, checking for DNA replication errors from previous phase

mitosis steps

prophase, metaphase, anaphase, telophase

mitosis

functions for growth, tissue repair, and asexual reproduction; transfers a full genome from 1 parent cell to 2 genetically identical daughter cells

G0

the state of a cell when it is not growing and dividing in the cell cycle

prophase

nuclear envelope begins to disappear; DNA coils into visible chromosomes; fibers move chromosomes towards cell center

metaphase

fibers align chromosomes across cell center

anaphase

fibers separate chromosomes into chromatids at the centromere; chromatids migrate to opposite sides of the cell

telophase

nuclear envelope reappears, establishes 2 separate nuclei; chromosomes begin to uncoil

G1 checkpoint

end of G1; checks cell size, nutrient availability, growth factor, and damage to DNA

G2 checkpoint

end of G2; checks accuracy of DNA replication and damage to DNA

M-spindle checkpoint

between metaphase and anaphase; checks that fibers have properly attached to chromosomes

cyclins

related proteins associated with specific phases of the cell cycle; used to activate cyclin-dependent kinases; promote cell cycle progression

cyclin-dependent kinases

enzymes involved in the regulation of the cell cycle; require cyclin binding for activation; phosphorylate substrates, promote cell cycle activities

autocrine

when a cell signals itself to start a reaction (ex. embryo development, pain sensation)

juxtacrine

signaling via the movement of ligands through junctions from the cytosol of one cell to the cytosol of another cell (ex. stem cell differentiation, immune response)

paracrine

signal molecules travel short distances to nearby target cells (ex. growth factor)

synaptic signaling

similar to paracrine signaling, but involves a specialized structure called a _____

endocrine

specialized cells release hormones or other signaling molecules that travel via the bloodstream to target cells (ex. hormones, electric nerve signals)

protein kinases

transfer phosphate from ATP to proteins

protein phosphatases

enzymes that remove phosphate from proteins

apoptosis

agents chop up DNA and organelles, parts are packaged in vesicles and digested by scavengers

G-protein coupled receptor

ligand binds to a G protein, which binds GTP; involved with vision and smell

tyrosine kinase receptors

surface protein that triggers a chain reaction in the cell that regulates functions like growth, cell division, and survival

ion channel

opens and allows or blocks ion flows when ligand binds to receptor protein