Bio 1511 Exam 1

speciescape

size of organism proportional to how many species have been described for that organism

what is “the unity of life”

at basic level, all living organisms are made of cells and rely on same mechanisms; organisms descend from common ancestor

what are two unifying theories of biology

cell theory, theory of evolution

cell theory

all living organisms composed of cells, cells arise from other cells

theory of evolution

genetic composition of population changes over time; evolution driven by natural selection

natural selection

descendants live in various habitats and adapt to fit ways of life; favorable traits accumulate as adapted organisms reproduce

what explains both the unity of life and the diversity of life

natural selection

how does genetic diversity arise

mutations, recombinations, genetics of mates (for sexual organisms)

____ evolve over time

populations

what is the evidence supporting evolution

direct observations, homology, fossil record, biogeography

examples of direct observation

darwin’s finches and their diets changed beak types, mantids change external appearance based on environment

artificial selection

humans select for characteristics from species to develop new species

homology

state of having the same or similar relation, relative position, or structure

examples of homology

forelimbs of mammals share same arrangement of bones but different functions, comparing embryos of different species, genes and biochemical pathways the same

convergent evolution

not homology; unrelated organisms develop similar features due to environmental pressures

analogous (in terms of evolution)

similar function

homologous (in terms of evolution)

similar origin

biogeography

accounts for geographic distance and continental drift

in a phylogenetic tree, what does a branch point represent?

the common ancestor of the lineages diverging from point

in phylogenetic tree, what does a hatch mark represent

homologous characteristic shared by all the groups to the right

where do cells receive signals from?

physical environment, other cells

epinephrine in liver cell

adrenal gland sends epinephrine

liver cell receives epinephrine in Beta receptor

triggers glycogen deposits to break down and release glucose out of cell into blood

blood glucose level increases

epinephrine in smooth muscle cell in blood vessel of skeletal muscle

adrenal gland sends epinephrine

smooth muscle cell receives epinephrine in beta receptor

triggers cell in blood vessel to relax

blood vessel increases in size and increases blood flow to muscle

cell signaling occurs in _____ and ____ organisms

unicellular, multicellular

interstitial fluid

fluid between cells

direct contact cell communication

local signaling; from cytoplasm to cytoplasm via cell junctions (gap junctions, plasmodesmata) or receptor-ligand interaction on cell surfaces

paracrine signaling

local signaling in animal cells; signaling cell sends molecules that are local regulators to nearby receiver cells

synaptic signaling

local signaling in animal cells; electrical signal in neuron induces release of neurotransmitters which diffuse across synaptic cleft into nearby receiver cell

endocrine (hormone) signaling

long-distance signaling in animal cells; endocrine sender cell secretes hormone into fluid, hormone travels via circulator system, hormone reaches all cells but is only received by receptor cells

autocrine signaling

local signaling; cell secretes molecule and receives it itself, can also be paracrine signaling

neuroendocrine signaling

long-distance signaling; nerve cell releases neurohormones that diffuse across synaptic cleft into bloodstream and are circulated to receiver cells

what are signals that cannot cross the plasma membrane

water soluble hormones; leave sender cell via exocytosis, travel via blood, received by receptors on cell membrane which carry messenger into nucleus/cytoplasm

what are signals that can cross the plasma membrane

lipid soluble hormone; leave sender cell, travel via blood on transport proteins to stay soluble in blood, received by intracellular receptor in nucleus/cytoplasm

transcription factor

activator of transcription to create gene that does necessary cellular response/function

what are the three main kinds of cell surface receptors

G protein coupled receptors, receptor tyrosine kinases, ion channel receptors

what are the two kinds of ion channel receptors

ligand-gated: require first messenger to open, voltage-gated: nervous system, require change in voltage to open

G protein coupled receptors

contains seven transmembrane domains; signal molecule binds to outside, intracellular segment is activated when first messenger binds

G proteins

interacts with intracellular component of GPCR, composed of alpha, beta, gamma subunits

GPCR and G protein Pathway

inactive: GDP in alpha subunit

active: GPCR binds to G protein turning GDP to GTP

activated alpha subunit removes from the beta and gamma unit

moves along the plasma membrane to bind to an enzyme

inactivate pt 2: alpha subunit of G protein hydrolyzes GTP back to GDP to inactivate enzyme

alpha subunit rejoins with beta and gamma subunit

hydrolyzes

break bond by adding water

receptor tyrosine kinases

monomers with ligand binding site, alpha helix in membrane, intracellular tail with tyrosine residue; plasma membrane receptors with enzymatic activity; catalyze transfer of phosphate groups from ATP to tyrosine residue

RTKs pathways

inactive: two monomers

active: signaling molecule binds to alpha helixes on monomers

monomers dimerize

dimerized kinases activate kinases to add phosphate from an ATP to tyrosine on tail of partner monomer (6 ATP to 6 ADP)

intracellular relay protein recognize activated receptor and binds to phosphorylated tyrosine causing conformational change to activate protein

signal transduction pathway activated leading to response

in RTK pathway, different ______ induce different cellular responses

conformational changes that occur once phosphorylated

in RTK pathway, once phosphorylated protein ____

becomes hydrophillic

dimerize

join together from one to two

ion channel receptors: ligand gated ion channel

ionotropic receptors; transmembrane receptor contains pore that opens and closes in response to signaling molecule

ion channel receptors: voltage gated ion channel

transmembrane receptor contains pore that opens or closes in response to changes in membrane potential (electrical current)

ligand gated ion channel pathway

inactive: receptor in plasma membrane, channel closed, ions of high concentration on one side

active: ligand binds to receptor

gate channel opens

ions flow from high concentration to low concentration

cellular response induced

inactive pt 2: ligand removes from receptor, gate channel closes, ions no longer move

signal transduction cascade pathway

active: first messenger activates relay molecule

relay molecule activates protein kinase 1

adds phosphate group from ATP to activate protein kinase 2

activate a protein to bring about cellular response

inactive: protein phosphatases (PP) catalyze removal of phosphate groups from proteins to make proteins inactive

signal transduction functions by activated proteins by ____ or ____

adding/removing phosphate groups, release 2nd messenger molecules

what are the advantages of signal transduction

amplification of responses so few molecules trigger huge response, tight regulation because specific components are needed for pathway, additional pathways

RAS/MAPK pathway

normal: growth factor binds to receptor in plasma membrane

signal relayed to alpha subunit of G protein called Ras

activated Ras has GTP bound to it

Ras passes signal to series of protein kinases

last kinase activates transcription factor to turn on genes for protein to stimulate cell division/cycle

mutation: Ras retains GTP with or without growth factor binded to receptor in plasma membrane

phosphorylation cascade never deactivates

transcription factor turning on genes stimulating cell division never deactivates

second messengers

water soluble molecules that activate cellular response, not proteins w

what is the benefit of second messengers

small so easy to make, destroy, and diffuse in cell

what pathways to second messengers participate in

GPCRs and RTKs because those pathways result in production/release of second messenger; intracellular receptors are transcription factors so second messengers aren’t involved

second messenger: cyclic amp pathway

activates: epinephrine (first messenger) binds to GPCR receptor

Gs protein activates by converting GDP to GTP and altering shape

Gs activate adenylyl cyclase to convert ATP to cAMP

cAMP (second messenger) binds to R (regulatory) subunit of protein kinase A which kicks out C (catalytic) subunits of protein kinase A

protein kinase A phosphorylates other proteins and its C subunits induce cellular response

inactivates: inhibitory GPCRs and G proteins block adenylyl cyclase activity so ATP is not converted to cAMP

example of second messenger pathway: cholera

B subunit of cholera toxin binds to ganglioside receptor in cell membrane of cells in small intestine

A subunit releases from cholera toxin and enters the cell to cause sustained activation of G protein (GTP cannot break into GDP)

G protein continuously activates adenylyl cyclase which catalyzes ATP into uncontrolled production of cAMP

cAMP activates protein kinases

phosphorylation cascade leads to chloride channel opening so Cl and Na ions leave

osmolarity of cell decreases so water flows out into intestine, results in watery diarrhea and dehydration

second messenger: Ca2+

in GPCR and RTK pathways; involved in muscle contraction, secretion of molecules, cell division; Ca2+ concentration in cytosol is low relative to outside of cell/ER; ion pump uses ATP to move Ca ions out of cells and into ER and mitochondria

second messengers: Ca2+, triphosphate (IP3) pathway

active: signaling molecule binds to GPCR and G protein is activated by turning GDP to GTP

phospholipase C is activated by G protein

phospholipase C cleaves phospholipid called PIP2 into DAG and IP3

DAG is a second messenger that activates protein kinases

IP3 binds to Ca2+ channels in the ER and opens them

Ca2+ flows out of the ER and raises calcium levels in cytosol

calcium ions activate proteins in signaling pathways

calmodulin

protein activated by calcium ions that triggers cellular response

example of second messenger: Ca2+, Nitric oxide, cGMP and the blood vessel

endothelial cell: acetylcholine is first messenger that binds to GCPR

G protein activates and leads to IP3 activating ER to release second messenger Ca2+

Ca2+ activates calmodulin protein

calmodulin activates nitric oxide synthase

smooth muscle cell: NO crosses plasma membrane and activates guanylyl cyclase

guanylyl cyclase adds GTP to activate second messenger cyclic GMP

cGMP activates protein kinase

triggers cellular response of relaxing muscles and dilating blood vessels

example of cell signaling regulating transcription

growth factor binds to GPCR, triggers phosphorylation cascade, final kinase in cascade enters nucleus, kinase activates transcription factor (CREB), CREB binds to CRE in DNA to activate transcription, resulting mRNA synthesizes particular protein in cytoplasm

scaffolding proteins

large relay proteins for which several other relay proteins attach; increase speed and accuracy because proteins right next to each other

specificity

same signal can induce different responses in different cells because different cells have different proteins

specificity in cell signaling

1. one first messenger, one response

2. one first messenger, two proteins, two responses

3. two first messengers, two proteins, cross talk occurs so one response

4. one first messenger, one protein changes shape, one response that is different from response first messenger may normally produce

scaffolding proteins pathway

first messenger binds to receptor

activates conformational change in receptor

scaffolding protein docks to receptor and activates

protein kinases attached to scaffolding protein activate and induce responses

what are the ways a signal can be terminated

concentration of first messenger decreases - destroy outside cell, diffuse away

in GPCRs, G protein breaks down GTP to GDP

second messenger degraded via phosphodiesterase which break down cyclic nucleotides (cAMP, etc)

protein phosphatases inactivate kinases by removing phosphate groups

receptors become desensitized via phosphorylation

receptors are intracellular and cannot catch first messenger

endocrine system

communicates via hormones, mostly long distance chemical signaling; slower but sustainable

nervous system

communicates via long distance electrical signals, mostly short distance chemical signaling; faster but unsustainable

hormone

chemical signal secreted into circulatory system that communicates regulatory messages in body

pheromone signaling

pheromone molecules release into external environment and function in communication between members of same species

what kind of signaling is pheromone signaling

chemical signaling but NOT hormonal signaling because hormonal communication is between cells

chemical regulators: local regulators

modified fatty acids, polypeptides, amines, gases; travel short distances, autocrine and paracrine signaling

chemical regulators: hormones

polypeptides, cholesterol-derived steroids, amines; travel long distances, endocrine signaling

which chemical regulators are hydrophilic (water-soluble)

insulin (polypeptides), epinephrine (amines)

which chemical regulators are hydrophobic (lipid-soluble)

cortisol (steroids), thyroxine (amines)

exocytosis

membrane bound vesicle binds to plasma membrane and secretes into intercellular space

example of cellular response pathways: epinephrine in liver

epinephrine is water-soluble hormone

binds to GPCR

activates G protein to activate adenylyl cyclase

to produce cAMP

to activate protein kinase to stimulate cellular response

cellular response: inhibit glycogen synthesis OR promote glycogen breakdown

example of cellular response pathways: estradiol in liver

estradiol is lipid soluble hormone; binds to intracellular receptor which crosses into nucleus and acts as transcription factor

feedback regulation: simple endocrine pathway

negative feedback; endocrine cells directly respond to stimulus by secreting hormone

hormone travels via bloodstream to target cell

hormone interacts with receptor and triggers response

response tells cell to slow down response

feedback regulation: simple neuroendocrine pathway

positive feedback; sensory neuron receives stimulus

neuron stimulates neurosecretary cell in hypothalamus

cell secretes neurohormone into bloodstream

neurohormone circulates to reach target cells

response tells cell to continue response

response doesn’t stop until stimuli stops

feedback regulation: hormone cascade pathway

multiple hormones are released; stimulus received by sensory neuron

neuron stimulates neurosecretary cell in hypothalamus to release neurohormone

neurohormone travels via bloodstream to endocrine cell’s receptor

activation of receptor triggers release of hormone

hormone interacts with receptor on target cell to trigger cellular response

hormone pathways involved in homeostasis are typically ____

negative feedback

the _____ and ____ systems can coordinate responses

nervous, endocrine; combine hormone cascade pathways and simple pathways

in what ways are hormonal signals terminated?

intracellular termination at site of reception (degradation of hormone, inhibition of transduction), extracellular degradation (in liver, spleen, etc), removal of hormone (excretion via kidneys)

most endocrine cells are aggregated in ______

glands

endocrine glands

ductless organs that secrete hormones into interstitial fluid then into blood stream

exocrine glands

secrete substances through ducts into cavities or surface of body

what glands are endocrine glands?

hypothalamus, pineal, pituitary, thyroid, parathyroid, adrenal, pancreas, ovaries, testes

tropic hormone

hormone with an endocrine gland/cell as target receptor because endocrine gland/cell will release another hormone; triggers hormone cascade pathway

non tropic hormone

hormone with non endocrine cell as target receptor; receptor cell activates direct response

in vertebrate animals, coordination of endocrine signaling relies on _______

hypothalamus

hypothalamus

neurosecretory gland located in brain; receives info from nerves and then sends hormonal signals to pituitary

pituitary

at base of hypothalamus; made up of posterior and anterior

posterior pituitary

axons from hypothalamus extend to posterior pituitary and secrete neurohormones into circulatory system to be sent to receptor cells

posterior pituitary: hormone 1

oxytocin; regulates milk secretion by mammary glands, triggers uterine contractions during birthing, influences maternal behaviors

posterior pituitary: hormone 2

antidiuretic hormone/vasopressin; increase water retention in kidneys

antidiuretic hormone in kidneys pathway

simple pathway and negative feedback;

blood osmolarity increases (too salty, neural impulse that your thirsty)

hypothalamus releases antidiuretic hormone into blood

kidney cells triggered to reuptake water

blood osmolarity normalizes and stops response

anterior pituitary

neurosecretory cells of hypothalamus secretes releasing or inhibiting hormone into the bloodstream via portal vessels, hormone reaches anterior pituitary via blood, triggers anterior pituitary to release or stop release of a hormone

anterior pituitary hormones

follicle stimulating and lutenizing - reproduction in testes/ovaries

thyroid stimulating - metabolism

adrenocorticotropic - manage long term stress

melanocyte stimulating - make melanin

growth hormone

prolactin - make milk