AP Biology Unit 4

homeostasis

“steady state“; maintaining near constant body conditions

negative feedback

control mechanisms that reduces the stimulus (maintain homeostasis)

positive feedback

control mechanisms that amplifies the stimulus (deviate from homeostasis)

thermoregulation

process of maintaining an internal temperature within a normal range

ectotherms

gain heat from surroundings, body temperature changes as environmental temperature changes

endotherms

generate body heat via metabolism; maintain a near constant body temperature

osmoregulation

process of keeping homeostasis in solutions

paramecium

fresh water protists (fish)

contractile vacuole

actively pumps water out of the cell (parameciums)

marine fish

lose lots of water (drink constantly, rarely pee)

freshwater fish

gain lots of water (rarely drink, constantly pee)

autocrine signaling

secreted molecules trigger a response in the cells that secret them

juxtacrine signaling

cells communicate via direct contact

gap junctions

cytoplasmic channels between animal cells

plasmodesmata

cytoplasmic channels between plant cells

paracrine signaling

secreted molecules trigger a response in nearby cells

endocrine

molecules secreted into the blood stream; affect cells anywhere in the body

steroid hormones

affect DNA expression to initiate long-term changes in the target cell

water-soluble hormones

affect enzyme activity to initiate short-term changes in the target cell

signal transduction pathway

series of steps whereby binding of a signaling molecules results in a cellular response

g-protein

protein that is activated when bound to GTP but inactivated when bound to GDP

g-protein coupled receptor

when activated by a ligand, it binds to an inactivated g-protein that activates it

second messenger

small molecule or ion that acts as an intermediary between the activated receptor and the activation of other proteins

protein kinase

enzyme that transfers phosphate groups from ATP to a protein

reception

signal molecule binds to recepetor

transduction

bound receptor stimulates another

response

specific changes occur in the cell

amplification

each enzyme in the pathway activated many enzymes in the next step

ion channel receptors

binding of ligand causes ion channel to open, allowing ions to enter or exit the cell

cell division

process where a cell reproduces, producing two identical daughter cells

binary fission

method of cell division used by bacteria, mitochondria, and chloroplasts

packaging DNA

DNA wraps around histone proteins to form chromatin

histones

help in condensing DNA (packaging DNA)

chromatin

relatively loose network of DNA and proteins

chromosomes

highly coiled, tightly packed network of DNA and proteins

diploid cells (2n)

cells with TWO non-identical versions of each chromosome

haploid cells (n)

cells with ONE version of each chromosome

somatic cells

diploid, contain 23 pairs of chromosomes (46 total), almost all body cells

gametes

haploid, contain 23 total chromosomes, egg and sperm cells

spindle

network of microtubules; helps move chromosomes around

centrosomes

“anchor“ microtubules at ends of the cell

interphase

resting phase, between divisions

G0 phase

non-dividing phase; cell does it’s “job“

G1 phase

cell grows in size (phospholipids added to membrane, new organelles produced)

S phase

DNA, as chromatin, is copied

sister chromatids

two identical copies of DNA, linked together on the same chromosomes

centromere

condensed region of DNA that connects sister chromatids

G2 phase

cell prepares for division, centrosomes replicate

mitosis

process where sister chromatids separate

prophase

chromosomes condense, spindle forms, nuclear envelope breaks down

metaphase

chromosomes line up down the center of the cell

anaphase

sister chromatids separate at the centromere and move to opposite ends of the cell

telophase

cell begins to split

cytokinesis

process where the cytoplasm divides

cleavage furrow

mechanism for cytokinesis in animal cells

cell plate

mechanism of cytokinesis in plant cells

cancer

uncontrolled cell division

tumor

mass of undifferentiated cells

benign

cells that remain at the point of origin

malignant

cells that spread, invading other tissues

metastis

spread of cancer cells into the blood stream and other cells

cell cycle clock

rhythmic fluctuations in cell cycle control molecules; regulates timing of cell cycle

cyclins

proteins; levels fluctuate during cell cycle

cyclin-dependent kinases

protein that joins with cyclin to form MPF

maturation promoting factor (MPF)

stimulates mitosis

checkpoints

“go“ or “no-go“ signals at G1, G2, or M

growth factors

proteins that stimulate cell division

density-dependent inhibition

crowded cells stop dividing

anchorage dependence

cells must be attached to an appropriate surface to divide

apoptosis

programmed cell death; occurs if cell has damage