Biology Quiz 5

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what are signals and how do cells respond

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what are signals and how do cells respond

signals can come from information from the environment surrounding the organism. It can be a chemical or a physical stimulus like a touch or smell signal.

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a successful signal results in

activation of cellular response by the target cell

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steps of a successful signal = response

  1. binding of signal (ligand) to receptor (specific to ligand)

  2. cascade of events inside the cell: signal transduction

  3. cellular response

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4

signal transduction

pathway involves a signal, a receptor, transduction of signal, and responses

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transduction of signal occurs through many

effector molecules

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allosteric changes

how effectors activate each other via phosphorylation

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short term

enzyme activation; cell movement it can happen right away

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long term

altered DNA transcription like produce proteins that aren’t in the cell and they can change their behavior to change the cell

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4 types of cell’s + their delivery

juxtacrine, paracrine, autocrine, endocrine

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juxtacrine

requires direct contact between signaling cell and receiving cell

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paracrine

“near by,” any cells near by that have a receptor to that signal (specific) can bind to it

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autocrine

the signaling cell is releasing a ligand and that cell itself can respond to its own signal because it has it’s own receptor

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endocrine

the signaling molecule gets into the circulatory system and is released throughout the body so any cell with the receptor can respond

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two types of receptors

intracellular receptors, membrane receptors

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types of intracellular receptors

steroid receptors

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types of membrane receptors

gated ion channels, protein kinase receptors, G protein-linked receptors

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intracellular receptors

within the cytoplasm, small or nonpolar ligands can diffuse across the cell membrane because phospholipic bilayer is hydrophobic

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membrane receptors

large or polar ligands can’t pass through the membrane instead it binds to the ligand outside the cell and relays the signal into the cell but the ligand doesn’t move

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protein kinase receptors

catalyze phosphorylation of themselves and/or other proteins

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gated ion channels

channel proteins that allow ions to enter or leave a cell (or not enter), ligand-gated, voltage-gated

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how are ligand-gated ion channel receptors and G protein-coupled receptors different from each other

only G protein coupled receptors use enzymatic reactions (causes change in substrate) to transmit a signal

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signal pathways can be _ meaning ----

short, the bound receptor directly causes the cellular response likes steroid hormones

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signal transduction

signals sometimes initiate a cascade of events

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what are two important features of signal transduction

the initial signal can be amplified and distributed and result in several responses, a particular signal may lead to different responses in different cells

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what is an example of signal transduction

a mitogen is a small molecule that induces a cell to begin cell division, a series of enzymes are activated by a preceding enzyme, the signal is amplified at each step

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second messangers

small non-protein molecules that relay signals from receptors on the cell surface to target molecules

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second messengers allow the cell to

respond to a single event at the plasma membrane with many events within the cell and there is an amplification and diversification of responses

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what are four second messengers

cAMP, Ca2+, Lipid-derived molecules, NO

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what are the steps for protein kinase receptors (insulin receptor example)

  1. the PKC receptor binds insulin (produced by pancreas)

  2. conformational change and dimerization

  3. phosphorylation of receptor itself, autophosphorylation

  4. phosphorylation of target proteins

  5. initiation of cellular responses

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steps for GPCRs

  1. ligand binding to GPCR leads to conformational change and GTP association/activation of the G-protein

  2. GTP-binding subunit separates from G protein and moves through plasma membrane until it encounters an effector protein

  3. binding activates the effector, which causes a change in cell function

  4. GTP is hydrolyzed to GDP, and G-protein is inactive again

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signal transduction pathways are

not permanent

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what are the three components of signal transduction

receptor recycling, loss of signal, revert to inactive form of transduction molecules

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receptor recycling

receptor proteins can be broken down

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loss of signal

some signals are short lived, stop that signaling pathway from being active

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enzymatic inactivation means

revert to inactive form of transduction molecules

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when ligands bind to receptors

reversibly, receptors are recycled, membrane receptors are used again after ligands leave

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3 ways to stop signaling

phosphatase, GTPase, Phosphodiesterase inactivates cAMP

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phosphatase

removes phosphate groups from target protein

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GTPase

removes phosphate group from GTP converting it to GDP

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Phosphodiesterase

inactivates cAMP which results in cAMP becoming AMP which is not part of signaling pathway

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do signal pathways act independently

no they do not

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different pathways can

have the same targets

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crosstalk

pathways can affect with one another

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is predicting effects of multiple signals challenging

yes it is challenging

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45

cells have

multiple receptors for multiple molecules

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46

type I diabetes is characterized by a pancreas that cannot produce its own insulin. If a person with type I diabetes misses an injection, there will be

an increase in blood glucose levels

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nervous system

sends signals out and can receive signals at very high speeds

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what are the two parts of the nervous system

central nervous system, peripheral nervous system

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central nervous system involves

brain and spinal cord

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peripheral nervous system

all of the other parts of the nervous system

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how does information travel in the nervous system

information goes through PNS and then into the CNS where it is processed then a response is sent by the CNS and pushed through the PNS to result in a response/decide if a response is necessary

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types of information sent to the nervous system

conscious, autonomic

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conscious

sensory information like sight, sound, smell

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autonomic

physiological information like blood pressure or maintaining homeostasis

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types of responses

voluntary, autonomic

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voluntary response

commands to skeletal muscles (behavior) like running away

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autonomic response

physiological controls like heart rate, sweating, salivation (also called autonomic nervous system)

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autonomic divisions for response

sympathetic, parasympathetic

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sympathetic is a

fight or flight response

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parasympathetic is a

rest and digest response

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sympathetic and parasympathetic divisions

need to balance each other out

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the components of the nervous system

sensors and effectors, neurons, sensory/afferent neurons, interneurons, efferent neurons

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sensors

can be conscious or autonomial and provide information about external environment and internal status

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effectors

cells or tissues that carry out the orders from the control system

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neurons

a cell that carry the signals of the nervous system

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nerves

neurons are packaged into bundles called

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what do neurons do with carrying signals

some neurons carry signals to the nervous system, some carry signal from the nervous system

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sensory/afferent

carry signals from sensor to CNS

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interneurons

confined to the CNS, integrate and coordinate signals between CNS and PNS

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efferent neurons

convey signal from CNS to effectors, an example is motor neurons convey signal to skeletal muscles

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what is the anatomy of a neuron

dendrites, cell body, axon, axon terminals, synapse

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dendrites

receive information from other neurons

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cell body

nucleus and organelles

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axon

conducts action potentials away from cell body

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axon terminals

carry information as action potentials away from the presynaptic cell (before synapse) to the postsynaptic cell (after synapse)

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synapse

point of contact between two cells, where we send the signal to the next cell

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neurons are _

excitable

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excitable

meaning they can generate and transmit electrical signals called action potential

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direction of propagation

the direction/movement of the signal traveling down the axon

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membrane potential

the electrical charge difference across the membrane

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resting membrane potential

the charge difference when a cell is at rest, a neuron not carrying a signal, -60 to -70 milivolts

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why is the resting potential negative

the inside of the cell is negative compared to the outside of the cell, ions can’t pass through the membrane on their own so this can be maintained

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how are charged created

charges are created by different amounts by ions on either side of the membrane

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how is resting potential established and maintained

4 ion channels allow us to pass through the membrane but they are selective

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active transport (ion channel system)

energy required, move molecules against the concentration gradient

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what is an ion channel that requires active transport

sodium-potassium (Na+ - K+) pump

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passive transport

no outside required (diffusion), molecules move down their concentration gradient (high to low)

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what ion channels require passive transport

K+ leak channel, voltage-gated Na+ channel, voltage-gated K+ channel

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sodium-potassium pump

use 1 ATP, 2K+ in cell, and 3Na+ out of cell back and forth to create a difference in ions

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voltage

electric potential difference between two points, positive charges in one place and negative charges in a different place, there can be an electrical potential across cell membrane

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potassium (K+) leak channels

the resting membrane potential is established mainly by K+ leak channels, passive transport K+ diffuses out of the cell, down its concentration gradient from inside to outside of the cell (this creates move negative charges within the cell)

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92

the resting membrane potential

is negative because the inside of the cell is more negative than the outside of the cell

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depolarization

a change in a cell’s membrane potential in which the interior becomes less negative; RMP moves toward zero. positive charges come into the cell

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hyperpolarization

a change in a cell’s membrane potential in which the interior becomes more negative; RMP moves away from zero. there is a large change in charge across the membrane

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ions

can open, allowing ions to flow through, changing the membrane potential

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voltage-gated channel

open or close in response to changes in membrane potential

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what does change in membrane potential mean for a voltage-gated channel

change in voltage, move away from resting potential, membranes sense this change and open up in response to this change

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ligand-gated channel

open or close in response to a ligand binding to the channel, then ions flow through, once the concentration inside the cell is a certain amount, the ligand removes itself from channel and the channel closes

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dendrites and cell body

receive signals from other sources, which trigger an influx of sodium ions, the change in membrane potential triggers the opening of a few voltage gated Na+ channels

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action potential

a sudden, rapid reversal in the voltage across a portion of the plasma membrane causes voltage-gated Na+ channels to open

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