Biology Quiz 5

what are signals and how do cells respond

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.

a successful signal results in

activation of cellular response by the target cell

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

signal transduction

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

transduction of signal occurs through many

effector molecules

allosteric changes

how effectors activate each other via phosphorylation

short term

enzyme activation; cell movement it can happen right away

long term

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

4 types of cell’s + their delivery

juxtacrine, paracrine, autocrine, endocrine

juxtacrine

requires direct contact between signaling cell and receiving cell

paracrine

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

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

endocrine

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

two types of receptors

intracellular receptors, membrane receptors

types of intracellular receptors

steroid receptors

types of membrane receptors

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

intracellular receptors

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

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

protein kinase receptors

catalyze phosphorylation of themselves and/or other proteins

gated ion channels

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

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

signal pathways can be _ meaning ----

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

signal transduction

signals sometimes initiate a cascade of events

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

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

second messangers

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

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

what are four second messengers

cAMP, Ca2+, Lipid-derived molecules, NO

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

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

signal transduction pathways are

not permanent

what are the three components of signal transduction

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

receptor recycling

receptor proteins can be broken down

loss of signal

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

enzymatic inactivation means

revert to inactive form of transduction molecules

when ligands bind to receptors

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

3 ways to stop signaling

phosphatase, GTPase, Phosphodiesterase inactivates cAMP

phosphatase

removes phosphate groups from target protein

GTPase

removes phosphate group from GTP converting it to GDP

Phosphodiesterase

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

do signal pathways act independently

no they do not

different pathways can

have the same targets

crosstalk

pathways can affect with one another

is predicting effects of multiple signals challenging

yes it is challenging

cells have

multiple receptors for multiple molecules

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

nervous system

sends signals out and can receive signals at very high speeds

what are the two parts of the nervous system

central nervous system, peripheral nervous system

central nervous system involves

brain and spinal cord

peripheral nervous system

all of the other parts of the nervous system

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

types of information sent to the nervous system

conscious, autonomic

conscious

sensory information like sight, sound, smell

autonomic

physiological information like blood pressure or maintaining homeostasis

types of responses

voluntary, autonomic

voluntary response

commands to skeletal muscles (behavior) like running away

autonomic response

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

autonomic divisions for response

sympathetic, parasympathetic

sympathetic is a

fight or flight response

parasympathetic is a

rest and digest response

sympathetic and parasympathetic divisions

need to balance each other out

the components of the nervous system

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

sensors

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

effectors

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

neurons

a cell that carry the signals of the nervous system

nerves

neurons are packaged into bundles called

what do neurons do with carrying signals

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

sensory/afferent

carry signals from sensor to CNS

interneurons

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

efferent neurons

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

what is the anatomy of a neuron

dendrites, cell body, axon, axon terminals, synapse

dendrites

receive information from other neurons

cell body

nucleus and organelles

axon

conducts action potentials away from cell body

axon terminals

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

synapse

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

neurons are _

excitable

excitable

meaning they can generate and transmit electrical signals called action potential

direction of propagation

the direction/movement of the signal traveling down the axon

membrane potential

the electrical charge difference across the membrane

resting membrane potential

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

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

how are charged created

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

how is resting potential established and maintained

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

active transport (ion channel system)

energy required, move molecules against the concentration gradient

what is an ion channel that requires active transport

sodium-potassium (Na+ - K+) pump

passive transport

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

what ion channels require passive transport

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

sodium-potassium pump

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

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

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)

the resting membrane potential

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

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

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

ions

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

voltage-gated channel

open or close in response to changes in membrane potential

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

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

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

action potential

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