AP Bio Unit 3: Ch 3, 7, 11

D.

Difference receptor leads to a different response

GTP is similar to ATP. How is energy generated

Loss of a phosphate group from the tail generates energy

Hypotonic solution

Lysed Turgid (normal)

Isotonic

Normal Flaccid

__________________ ______________________ through a cell membrane includes diffusion, osmosis, and facilitated transport through a protein.

Passive transport

When a signal molecule binds as a ligand to the receptor, the gate then allows specific ions, such as sodium or calcium, through

a channel in the receptor

quorum sensing

a concentration of signaling molecules allows bacteria to sense local population density in this process

glycolipid

a lipid with one or more covalently attached carbohydrates

A neurotransmitter is

a molecule released from the synaptic terminal of a neuron

Explain the term ligand. (This term is not restricted to cell signaling. You will see it in other situations during the year)

a molecule that binds specifically to another molecule, usually a larger one

define turgid

a plant in a hypotonic solution swells until the wall opposes uptake; the cell is now turgid (firm)

enzymatic actibity

a protein built into the membrane may be an enzyme with its active sire exposed to substances in the adjacent solution several enzymes in a membrane are organized as a team that carries out sequential steps of metabolic pathway

concentration gradient

a region along which the density of a chemical substance increases or decreases

Phosphorylation cascade 1:

a relay molecule activates protein kinase 1

define paracrine signaling

a secreted molecule acts on a neighboring cell

What is a signal transduction pathway

a series of steps linking a chemical, mechanical or electrical stimulus to a specific cellular response

what is often the initial transduction of a cell signal

a shape change in a receptor

define ligand

a signal molecule

aqueous solution

a solution in which the solute is dissolved in water; water in the solvent

What is a ligand

a term for any molecule that binds specifically to .a receptor site on another moleculw

what is cotransport

a transport protein (cotransporter) can couple the downhill diffusion of the solute to the uphill transport of a second substance against its own concentration gradient.

phagocytosis-

a type of endocytosis in which large substance or small organisms are taken up by a cell

Why does the red blood cell burst when placed in a hypotonic solution, but not the plant cell

because water will enter the cell faster that it leaves and the cell will burst like an overfilled water balloon

describe a carrier protein

bind to molecule and change shape to shuttle them across the membrane example is a sodium potassium pump

transduction

binding of the signaling molecule changes the receptor protein

integrins

binds to the ECM on the outside and to associated proteins on microfilaments on the inside; function mechanically

describe a peripheral protein

bound to the surface of the membrane

cells that are not recognized as self are considered foreign and will be targeted by the immune system. How are cells able to recognize one another

by binding to molecules, often containing carbohydrates on the extracellular surface of the plasma membrane covalently bonded to lipids (glycolipids) or proteins (glycoproteins) carbs vary on every species

increasing the number of saturated hydrocarbon tails

can pack closer together and they lose their fluidity quicker

why is acidification a threat to marine organisms in the oceans

carbonate ions are needed for calcification which produces calcium carbonate by many marine organisms, including reef-building corals and animals that build shells

in the breakdown of glycogen what is the first messenger and the second messenger

first: activates the G protein which activated adenlyl cyclase which catalyzes the conversion of ATP to cAMP second: the cAMP which activated another protein (protein kinase A) leading to cellular responses.

cholesterol

fluidity barrier resists changes caused by temp high temp: makes membrane less fluid by restraining movement lower temperature: required for the membrane to solidify

How is a cell response inhibited

further regulation may inhibit adenylyl cyclase. In these systems, *a different signaling molecule activates a different receptor which in turn activates an inhibitory G protein* that blocks activation of adenylyl cyclase.

ligand (step 1)

gate remains closed until a ligand binds to the receptor (a signaling molecule)

distinguish the different between glycolipids and glycoproteins

glycolipids: some carbohydrates are covalently bonded to lipids, forming these lipids with one or more covalently attached carbs glycoproteins: most are covalently bonded to proteins, which are glycoproteins; protein with one of more covalently attached carbs

Some chemical signals are received by specific target cells. What is required for receptor by a target cell?

growth factors

Give an example of local regulators

growth factors stimulate nearby target cells to grow and divide in animals

describe a channel protein

have a hydrophoilic channel that certain molecules or ions can use as a tunnel

define hydrophillic

having an affinity for water

hydrophobic

having no affinity for water; tending to coalesce and from droplets in water

bugs can walk on water due to its

high surface tension

Describe the effect of cholesterol (a steroid) at different temperatures

high temp: cholesterol restrains movements of phospholipids cool temp: maintains fluidly by preventing tight packing

substances move down their concentration gradient from ___________ to _________ concentration

high to low passive transport

water moves from an area of

higher water concentration (lower solute concentration) to lower water concentration (higher solute concentration).

list three types of cellular response often induced by calcium ions. Be sure to include a plant example

hormonal/environmental stimuli in plants, neurotransmitters, growth factors, some hormones

Long-distance signaling: Example: In long-distance signaling, plants and animals use chemicals called

hormones

what types of signal molecule bind to this protein receptor

hormones and neurotransmitters

proton pump (refer to)

hydrogen ions

Review: Describe how the hydrophobic and hydrophilic regions are oriented to make up the cell membrane.

hydrophilic heads face out toward watery regions hydrophobic tails face each other

___________________ molecules, including ions and polar molecules, do not cross the membrane easily

hydrophillic

phospholipids are amphipathic molecules that contain ________________ and _____________ regions

hydrophobic and hydrophillic

Phosphorylation cascade 5:

enzymed called protein phosphatases (PP) catalyze the removal of the phosphate groups from the proteins, making them inactive for available reuse

protein phosphatases

enzymes that can rapidly remove phosphate groups from proteins, a process called dephosphorylation

the same small set of cell signaling mechanisms shows up in diverse species and processes. This provides additional evidence for the

evolutionary relatedness of all life

give examples of second messengers

ex: cycling AMP and cations

The sodium potassium pump labeling

exchanges Na+ for K+ across the plasma membrane of animal cells

describe a g protein coupled receptor

extremely widespread and diverse; include embryonic development, vision, smell, and taste Cell surface transmembrane receptor that works with the help of a G protein (binds GTP)

ion channel

facilitate the diffusion of ions.

aquaporin

facilitate the diffusion of water

describe an aquaporin

facilitate the passage of water

Phosphorylation cascade 4:

finally active protein kinase 3, phosphorylates a protein that brings about the cells response to the signal

cell membrane structure results in selective permeability. What types of molecules are able to move easily through the lipid regions of the cell membrane (Co2 and oxygen)

hydrophobic molecules

diffusion-

hydrophobic molecules and (at a slow rate) very small uncharged polar molecules can diffuse through the lipid bilayer

why types of molecules can serve as signals, give examples

hydrophobic/small molecules; steroids, thyroid and nitric ocide

define flaccid

if a plant cell is isotonic and there is no net movement of water into the cell, the cell becomes flaccid (limp)

flaccid

if a plants cells and their surrounding are isotonic, there is no net tendency for water to enter and the cells become flaccid (limp)

where are intracellular receptor proteins located

in the cytoplasm/nucleus of target ells

Cell signaling in the microbial world continued

many bacterial species secrete small signaling molecules that can be detected by other bacterial cells.

Facilitated diffusion

many hydrophilic substances diffuse through membrane with the assistance of transport proteins wither channel proteins (left) or carrier proteins (right)

Explain what happens in step 1

many receptor tyrosine kinases have the structure depicted schematically here. Before the signaling molecule binds , tyrosine the receptors exists as individual units referred to as monomers

cascade

many relay molecules in a signal transduction pathways are protein kinases, creating a phosphorylation cascade

Second messengers

many signaling pathways involve second messengers

small molecule leave through

membrane

intercellular joining

membrane proteins of adjacent cells may hook together in various kinds of junctions, such as gap junctions or tight junctions. This type of binding is more long-lasting than cell-cell recognition

What happens to the cell membrane as temperatures cool

membrane switches from a fluid state to a solid state. Temp depends on the type of lipids

Which membranes are more fluid

membranes rich in unsaturated fats

attachment to the cytoskeleton and extracellular matrix

microfilaments or other elements of the cytoskeleton may be non-covalently bound to membrane proteins, a function that helps maintain cell shape and stabilized the location of certain membrane proteins proteins that can binds to ECM molecules can coordinate extracellular and intracellular changes

hyper means

more solute

membrane proteins are the __________ part of the model.

mosaic

phospholipids can move within the plasma membrane. What can shift laterally

most of the lipids and some proteins (move from side to side)

how is glucose moved across the membrane

moved with the carrier protein in red blood cells

receptor mediated endocytosis

movement of a specific molecule into a cell by the in folding of vesicles containing protein with receptor site specific to the molecule being taken in

The cytoplasmic side of the cell membrane is _____________ charged and the extracellular side of the cell membrane is _______________ charged

negatively//positively

give an example

neurotransmitters across the synapse

does passive transport require energy

no

passive transport across a cell membrane requires

no energy

describe three examples of apoptosis, including normal as well as abnormal function

normal: apoptosis in C. elegans and Ced-9 abnormal functions: webbed fingers and toes, cancer

Peripheral proteins

not embedded in the lipid bilayer; they are appendages loosely bound to the surface of the membrane, exposed to parts of integral proteins

Synaptic signaling is another example of local signaling. Describe synaptic signaling

occurs in the animal nervous system when a neurotransmitter is released in responsed to an electrical signal (a nerve impulse)

describe cotransport

occurs when active transport of a solute indirectly drives transport of other substances

G proteins act as an

off and on switch for the cell signals

gated channels

open or close in response to stimulus

Where are the signals for apoptosis initiated? Briefly explain the process

outside the cell: signaling molecules released from other cells can initiate a signal transduction pathway that activates the genes and proteins responsible for carrying out cell death within a cell: in a cell whose DNA has been damaged, a series of protein-protein interactions can pass along a signal that similarly triggers cell death.

the signal for apoptosis can come from outside or inside the cell. Give one example when the signal comes from outside the cell and two examples of cellular occurrences that would prompt an apoptosis signal from inside the cell

outside: cell surface receptor; signaling molecules released from other cells can initiate a signal transduction pathway that activates the genes and proteins responsible for carrying out cell death inside: from the nucleus when DNA is damaged and from the ER when excessive protein misfolding occurs

This type of local signaling is called

paracrine signaling

two common second messengers are cyclic AMP and calcium ions. Explain the role of the second messenger cAMP Figure 11.12 in the text

participate in pathways. The second messenger activates another protein, leading to a cellular response

how is H2O moved across the membrane

passes between the lipids

facilitated diffusion

passive transport aided by proteins

B

pathway branches, leading to two responses

A.

pathway leads to a signal response

describe an integral protein

penetrate the hydrophobic core

integral proteins

penetrate the hydrophobic interior of the lipid bilayer. Majority are transmembrane proteins

Label and describe what happens in step 3

the activated G protein dissociates from the receptor diffuses along the membrane and then binds to the enzyme, altering the enzymes shape and activity once activated, the enzyme can lead to a cellular response

what is the function of phosphorylation and dephosphorylation

regulate protein activity acts as a molecular switch, turning activities up or down or on and off as required

decreasing temperature

remain fluid as temp decreases until the membrane solidifies

phospholipids with unsaturated hydrocarbon chains

remains fluid to a lower temperature with these because of the kinks in the tails so they can't pack together as closely

dephosphorylation

removing a phosphate, protein phosphates rapidly remove the phosphate from proteins in this process

What normally happens in a nuclear response

the activation of a specific gene by a growth factor the initial signaling molecule, a growth factor triggers a phosphorylation cascade once phosphorylated, the last kinase int he sequence enters the nucleus and activate a gene-regulating protein, a transcription factor which stimulated the transcription of genes. the mRNAs direct the synthesis of a particular protein in the cytoplasm steps: reception, transduction, response

reception

the binding between a signal molecule (ligand) and receptor is highly specific

Step 2

the binding of signaling molecules causes two receptor monomers to associate closely with each other forming a dimer

describe transduction

the binding of the signaling molecule alters the receptor and initiates a signal transduction pathway, series of steps

steroid 4; this is also the function of transcription factors in the cell

the bound protein acts as a transcription factor stimulating the transcription of the gene into mRNA

pinocytosis-

the cell ingests extracellular fluid and its dissolved solutes.

osmosis-

the diffusion of free water across a selectively membrane

two combined forces, collectively called the electrochemical gradient, drive

the diffusion of ions across a membrane

describe an electrical force

the effect of the membrane potential on the ion's movement

When the ligand moves away,

the gate closes

cytoskeleton microfilaments

support to the cell; stabilize the shape

ECM fibers

support/protection

Describe reception

target ells detects a signaling molecule that binds to a receptor protein on the cells surface

What is a key difference between receptor tyrosine kinases and G protein coupled receptors

the ability of a single ligand binding event to trigger multiple pathways in RTKs

define tonicity

the ability of a surrounding solution to cause a cell to gain or lose water

Most water soluble signal molecules bind to specific sites on receptor proteins that span the plasma membrane

(transmembrane proteins)

apoptosis process

*During this process, cellular agents chop up the DNA and fragment the organelles and other cytoplasmic components.

How is cellular debris removed from the cell

*The cell shrinks and becomes lobed and the cells parts are packaged up in vesicles that are engulfed and digested by specialized scavenger cells, leaving no trace. *apoptosis protects neighboring cells from damage that they would otherwise suffer if a dying cell leaked out all of its contents, including many digestive enzymes.

Define apoptosis and describe the process

*apoptosis: a type of programmed cell death, which is brought about by activation of enzymes that break down many chemical components in the cell.

Using figure 11.20 and information on page 228, describe the process of apoptosis in the worm, C. elegans

*in the worms, apoptosis occurs 121 times during normal development which is triggered by a cascade of suicide proteins in the cells. -ced-3 and 4 encode the proteins essential for apoptosis -Ced-9 serves as the master regulator for apoptosis which breaks the signal promoting apoptosis no death signal: As long as Ced-9, located in the outer mitochondrial membrane, is active, apoptosis is inhibited and the cell remains alive death signal: when a cell received a death signal, Ced-9 is inactivated relieving its inhibition of Ced-3 and Ced-4. Active Ced-3, a protease, triggers a cascade of reactions leading to activation of nucleases and other proteases. The action of these enzymes causes the changes seen in apoptotic cells and eventual cell death.

Discuss the evolutionary links between other organisms and mammals

*similarties between apoptosis genes in nematodes, mammals, fungi, and yeast show that this evolved early in eukaryotes *essential for normal development in vertebrates *the level of apoptosis between the developing digits is lower in the webbed feet of ducks and other water birds than in the non webbed feet in land birds, such as chickens. In humans, the failure of apoptosis can result in webbed fingers and toes.

describe a hypertonic solution

*solute concentration is greater outside than that inside the cell (less water); cell loses water *more solute, less water

Summarize the effects of apoptosis in the mouse paw during development. Fig 11,21, Does this process also take place in humans

-In mice, humans, other mammals, and land birds; the embryonic region that develops into feet or hands initially has a solid, platelike structure -Apoptosis eliminates the cells int he interdigital regions, thus forming the digits. -Apoptosis of cells begins at the margin of each interdigital region, peaks as the tissue in these regions in reduced, and is no longer visible when the interdigital tissue has been eliminated (right)

What are the two forces that drive the diffusion across the membrane? What is the combination of these forces called?

-a chemical force (ions concentration gradient) and an electrical force -the effect of the membrane potential on the ion's movement -combination of chemicals is called the electrochemical gradient

signal transduction

-a membrane protein (receptor) may have a binding site with a specific shape that fits the shape of a chemical messenger, such as a hormone -the external messenger (signaling molecule) may cause the protein to change shape, allowing it to relay the message to the inside of the cell, usually by binding to a cytoplasmic protein

plasmolysis

-a phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall -occurs when the cell loses water to a hypertonic environment

transport protein

-a protein that spans the membrane may provide a hydrophilic channel across the membrane that is selective for a particular solute -other transport proteins shuttle a substance from one side to the other by changing shape. Some of these proteins hydrolyze ATP as an energy source to actively pump substances across the membrane

Describe receptor tyrosine kinases (RTKs)

-associated with cell growth and cell reproduction; membrane receptors that attach phosphates to tyrosines -major class of receptors that have enzymatic activity

Signal transduction usually involves multiple steps. What is the benefit

-can greatly amplify a signal -provide more opportunities for coordination and regulation of a cellular response

passive transport

-diffusion of a substance across a biological membrane with no expenditure of energy

membrane carbohydrates are important in cell-cell recognition. What are two examples of this?

-distinguish one type of neighboring cell from another, crucial to the functioning of an organism -basis for the rejection of foreign cells by the immune system -sorting of cells into tissues and organs in an animal embryo

examples of facilitated diffusion

-hydrophilic passageways allow water molecules to diffuse quickly -aquaporins facilitate massive amount of diffusion that occur in plant and animal cells -ion channels serve as gated channel- open, close in response to a stimulus

what is facilitated diffusion and is it passive or active

-many polar molecules/impeded by the lipid bilayer diffuse passively with the help of transport proteins that span the membrane -it is passive

membrane fluidity

-membranes are not static sheets of molecule -they can shift laterally or move across the cell membrane

describe facilitated diffusion

-no energy required -transport protein speed the passive movement of molecules across the plasma membrane

What roles does apoptosis play in vertebrates

-normal development of the nervous system, immune system, and for nonmorphogenesis of hands and feet in humans and paws in other mammals.

Sutherland studied that hormone epinephrine. He suggested that cells receiving signals undergo three process- list the processes

-processes convert glycogen to glucose -reception, transduction, response

Evolution of cell signaling

-signal transduction pathways convert signals received at a cell's surface into cellular responses -the yeast, Saccharomyces cerevisiae, has two mating types, a and alpha -Each mating type secretes a specific signaling molecule, a factor and an alpha factor. -The factors bind to receptor proteins on the other mating type. The cells grow toward each other and fuse together

what is a second messenger

-small, nonprotein water soluble molecules that spread through a cell by diffusion -participate in GPCR and RTK pathways

Describe endocrine signaling

-specialized cells release hormones which travel to target cells via the circulatory system -the ability of a cell to response to a signal depends on whether or not it has a receptor specific to that signal

Water has a high specific heat. Describe this property

-the ability of water to stabilize temperature stems from its relatively high specific heat -the amount of heat that must be absorbed or lost for 1 gram of a substance to change its temperature by 1 degree celcius

define adhesion

-the clinging of one substance to another -the clinging of one substance to another, such as water to plant cell walls by means of hydrogen bonds

describe osmoregulation and give an example

-the control of solute concentrations and water balance; a necessary adaptation for life in such environments -ex: protist paramedium, is hypertonic to its pond water, environment has a contractile vacuole that acts as a pump

define cohesion

-the hydrogen bonds hold the substance together -linking together of like molecules, often by hydrogen bonds

Describe active transport. What type of transport proteins are involved, and what is the role of ATP is the process

-the movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins are requiring an expenditure of energy -to pump a solute across a membrane against a gradient requries work and the cell must expend energy. This membrane traffic is called active transport -carrier proteins are involved. -Enabled a cell to maintain internal concentration of small solute that differ from concentration in its environments -ATP supplies the energy; transfers its terminal phosphate group directly to the transport protein which can changed its shape in a manner that translocate a solute bound to the protein across the membrane

diffusion:

-the movement of particles of any substance so that they spread out into the available space. -the random motion of particles of liquids, gases, or solids -high to lower concentration

high heat of vaporization

-the quantity of heat a liquid must absorb for 1 gram of it to be converted from the liquid to the gaseous state -water's high heat of vaporization is another emergent property resulting from the strength of its hydrogen bonds, which must be broken before the molecules can exit from the liquid in the form of water vapor

Compare and contrast a channle protein to a carrier protein

-these are examples of facilitated diffusion

What are the six major functions of membrane proteins *diagram in book*

-transport -enzymatic activity -signal transduction -cell-cell recognition -intercellular joining -attachment to the cytoskeleton and extracellular matrix (ECM)

Distinguish between channel proteins and carrier proteins

-transport proteins -channel: have hydrophilic channels that molecules can use as a tunnel through the membrane -carrier: hold onto their passengers and change in a way that shuttles them across the membrane

turgid

-very firm -swollen or distended, as in plant cells -a walled cell become turgid if it has a lower water potential that its surrounding, resulting in entry of water

Steps of the sodium potassium pump

1. Cytoplasmic Na+ binds to the sodium potassium pump. The affinity for Na+ is high when the protein has this shape 2. Na+ binding stimulates phosphorylation by ATP 3. Phosphorylation leads to a change in protein shape, reducing its affinity for Na+, which is released outside 4. The new shape has a high affinity for K+, which binds on the extracellular side and triggers release of the phosphate group 5. Loss of the phosphate group restores the proteins original shape, which has a lower affinity for K+ 6. K+ is released; affinity for Na+ is high again and and the cycle repeats

An individual tyrosine-kinase protein consists of three parts. List the parts

1. an extracellular signal molecule binding site 2. a signal alpha helix that spans the entire cell membrane 3. an intracellular tail with several tyrosines

Steps of Tyrosine-Kinase receptors

1. the signaling molecule binds to the receptor tyrosine kinase molecule 2. two receptor monomers associate closely with one other forming a dimer 3. dimerization activates the tyrosine kinase region of each monomer and each tyrosine kinase adds a phosphate from an ATP molecule to a tyrosine tail 4. The receptor is fully activated and is recognized by specific relay proteins inside the cel 5. Each protein binds to a specific phosphorylated tyrosine. A structural change takes place and the fully bound protein is activated 6. Each activated protein triggers a transduction pathway leading to a cellular response

One receptor tyrosine-kinase (RTK) can activate

10 or more different transduction pathways and cellular responses

A single molecule of epinephrine results in the formation of how many molecules of glucose-1 phosphate

10^8 molecules of G protein

How many capsases carry out apoptosis in humans and other mammals

15 different caspases can carry out apoptosis

How does a yeast mating serve as an example of a signal transduction pathway?

2 mating types secrete a specific factor that binds to receptors only one the other type of cell

How many daltons are in one gram?

6.022 x 10^23 *this measurement is also called a mole or the molar mass*

How many alpha helices are in the G-protein linked receptor

7

peripheral protein

A protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer.

glycoprotein

A protein with one or more carbohydrates covalently attached to it.

integral protein

A transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on one or both sides of the membrane (or lining the channel in the case of a channel protein).

a ________________ protein is specific for the substance it moves

A transport protein

active transport usually uses _______ as a source of energy.

ATP

What are two benefits of multistep pathways?

Amplification of signal, and better regulation/more opportunities for coordination

The binding of a signaling molecule receptor triggers the first step in a chain of molecular interactions. Like falling dominoes, the receptor activates another protein, which activated another, and so on until the protein producing response is activated. What takes place at each step of the process

At each step, the signal is tranduced into a different form, usually a shape change in a protein

Summarize the information in the second paragraph of page 229 (at key gateways...)

At key gateways into the apoptotic program, relay proteins integrate signals from several different sources and can send a signal down a apoptotic pathway. The signal originates outside the cell and occupies a cell-surface receptor which leads to the activation of caspases and other enzymes that cause apoptosis. This is a process of signal reception, transduction, and response. Apoptosis can also occur from the inside of the cell and the signals come from the nucleus and from the endoplasmic reticulum. Mammalian cells make life or death decisions by integrating the death signals and life signals they receive from these external and internal sources.

What happens to the cytoplasmic concentration of calcium when it is used as a second messenger

Ca2+ concentration of cytosol is much lower than the concentration outside the cell. The level of calcium ions is more than 10,000 times higher than that in the cytosol. Calcium concentration in the ER is usually much higher than that in the cytosol - because of the cytosolic calcium level is low, a small change in absolute numbers of ions represents a relatively large percentage change in calcium concentration

Transduction

Cascades of molecular interactions relay signals from receptor to target molecules in the cell

C.

Cross-talk occurs between two pathways

what is the difference between a first messenger and second messenger

First messenger is the ligand second messenger is any small, non-protein components of a signal transduction pathway.

The text explains the three major types of membrane receptors in figure 11.8/ This material is of fundamental importance, so we will work through the specific figures for each type of membrane receptor. The first example is a G protein coupled receptor. What are the three components and then describe the role

G protein coupled receptor: signal receptor that responds to the binding of a signaling molecule G protein: molecular switch GDP: when bound to the GDP protein, the G protein is inactive

Further regulation of cell metabolism is provided by

G protein systems that inhibit adenylyl cyclase

There are three main types of plasma membrane receptors:

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

figure 11.8 How does a G protein receive a signal? Why are cells able to respond to many different signals

G-protein functions as a switch the receptor and G protein work together with another proteins

Main difference between receptor kinase receptors and GPCRs

GPCRs only activates a single transduction pathway

Briefly describe how Alzheimers disease and cancer are related to problems with cell signaling

In alzheimers disease, an accumulation of aggregated proteins in neuronal cells activates an enzymes that triggers apoptosis, resulting in the loss of brain function seen in these patients. Cancer can result from the failure of apoptosis. For example, melanoma has been linked to faulty forms of the human version of the C. elegans Ced-4 protein.

Hypertonic solution

Shriveled Plasmolyzed

Steps of g protein coupled receptor

Step 1 the G protein is located on the cytoplasmic side of the cell membrane Step 2 When GDP (guanosine diphosphate) is bound to the G protein, the protein is active Step 3 When a signaling molecule binds to the protein receptor, the receptor is activated and the shape changes Step 4 the inactive GDP binds to the G protein receptor (transmembrane protein) Step 5 This causes a GTP to displace the GDP and activates the G protein Step 6 the activated G protein dissociates (moves away) from the receptor protein Step 7 The G protein diffuses along the cell membrane and binds to an enzyme, altering the enzymes shape and leading to a cellular response Step 8 The enzyme triggers the next cellular response and these actions take place many times Step 9 The G protein now functions as a GTPase enzyme and hydrolyzes GTP (adds water to break bonds) to produce GDP and p(1). This inactivates the pathway.

although ice is a solid, it is less dense than water. Explain why

Water expands hen it solidifies due to hydrogen bonding

why is water such a good solvent

Water's polarity gives it the ability to dissolve both ionic compounds and other polar compounds

What happens in step 2 of G protein coupling

When the appropriate signaling molecule binds to the extracellular side of the receptor, the receptor is activated and changes shape. Its cytoplasmic side then binds an inactive G protein, causing a GTP to displace the GDP. This activates the G protein.

the ligand attachment to the receptor is . In step 3, the ligand dissociated. Label and explain what occurs

When the ligand dissociates from this receptor, the gate closes and ions no longer enter the cell

are the process you described the question 26 active or passive transport? Explain your response

active because the cell uses energy to move particles

Phosphorylation cascade 2:

active protein kinase 1 transfers a phosphate from ATP to an inactive molecule of protein kinase 2, thus activating this second kinase

Phosphorylation cascade 3:

active protein kinase 2 then catalyzes the phosphorylation (and activation) of protein kinase 3

channel and carrier protein diagram

active transport requires energy

A ligand gated protein ion channel

acts as a gate when the receptor protein changes shape

How is ATP converted to cAMP

adenylyl cyclase, an enzyme in the plasma membrane converts ATP to cAMP in response to an extracellular signal

active transport moves substances ______________ their concentration gradients

against

steroid 2

aldosterone binds to a receptor protein int he cytoplasm activating it

quorum sensing

allows bacteria to coordinate their behaviors. Ex: formation of a biofilm; cells in the film generally derive nutrition from the surface

A g protein is also a GTPase enzyme Why is this important

allows the pathway to shut down rapidly when the signaling molecule molecule is no longer present

Tyrosine is an

amino acid

Kinase

any enzyme that catalyzes the transfer of a phosphate group

evolution: Why are there variations in lipid composition of cell membranes in different species

appear to be adaptations to specific environmental conditions. Ability to response to temp changes evolved in organisms that live where temperatures vary

Describe a ligand-gated ion channel receptor

associated with the nervous system; acts as a gate when a signal molecule binds and the receptor changes shape

List two methods in which cells in multicellular organisms can communications using signaling molecules

cell junctions: directly connects the cytoplasm of adjacent cells > allows signaling substances in the cytosol to pass freely local signaling: animal cells may communicate direct contact

________ _____________ is crucial to the normal functioning of a cell within an organism.

cell recognition

how is H+ moved across the membrane

cell regulates concentration of this ion by shutting them across the membrane

proton gradients are used in the

cells of animals, plants, etc to produce ATP during cellular respiration

exocytosis

cells secrete molecules by the fusion of vesicles with the plasma membrane ex: cells in the pancreas that make insulin secrete it into the extracellular fluid by exotytosis

endocytosis

cells take in molecules and particulate matter by forming new vesicles from the plasma membrane

what specifically happens to a cell during apoptosis

cellular agents chip up the DNA, the cell shrinks and becomes lobed, and the cells parts are packaged up and it leaves no trace

Equally important to starting a signal is stopping a signal. Step 4 stops the signal. How is the signal halted

changes in the enzyme and G protein are only temporary because the G protein hydrolyzes its bound GTP to GDP and Pi. Now inactive again, the G protein leaves the enzyme which returns to its original state

Cell-to-cell communication: Cells can signal each other and interpret the signals they receive from other cells and the environment. The signals are most often?

chemicals

what is the most common type of signal

chemicals

The high surface tension is due to

cohesion

water from the root of a tree can reach the highest branches due to

cohesion

Local signaling in plants is not well understood beyond

communication between plasmodesmata

channel protein provides

corridors that allow a specific molecule or ion to cross the membrane

define voltage

created by differences int he distribution of positive and negative ions across a membrane

Where are intracellular receptors found? This means the signaling molecules must be able to pass through the plasma membrane

cytoplasm or nucleus

what side of the membrane is positive/negative

cytoplasmic side: negative extracellular side: positive

How is a cytoplasmic response different from a nuclear response

cytoplasmic: signal molecule is hormone that controls enzyme activity nuclear: signal molecule is a growth factor that controls gene expression

Synaptic signaling

description: neurotransmitter triggers segregation ex: muscle/nerve cell

Paracrine signaling description and example

description: numerous cells stimulate molecules ex: a growth factor

cell membranes contain many different proteins. What general roles do proteins play

determine the membranes specific functions

how is it that some cells do not respond to specific signaling molecules and for the cells that do respond, it is often in different ways

different cells have different proteins and the response of a cell to its *signal depends* on its receptor protein, relay proteins, and proteins needed for the response signals trigger different responses

osmosis

diffusion of water across a selectively permeable membrane

passive transport includes diffusion, osmosis, and facilitated transport by proteins. Give a brief overview of each type of transport

diffusion: osmosis: facilitated transport:

how are receptors activated in step 3

dimerization activates the tyrosine kinase region of each monomer, each tyrosine kinase adds a phosphate from an ATP to a tyrosine

how can chemical signals pass between animal cells and plant celles

direct contact animals: gap junctions plants: plasmodesmata

Solvent

dissolve agent of a solution

how is O2 moved across the membrane

dissolve in bilayer and cross without the need of a membrane

how is CO2 moved across the membrane

dissolve in the lipid bilayer and cross it easily

Using step 4, explain how the activated receptor can stimulate multiple cellular response pathways. Each activated protein shown in this step triggers a different signal transduction pathway, leading to a different cellular response

each such protein binds to a specific tyrosine change that activates the bound protein

G-protein coupled receptors play roles in

embryonic development, vision, and smell

Hormonal signaling in animals is called

endocrine signaling

transport across the plasma membrane can also take place through

endocytosis (In) and exocytosis (out)

endo and exo cytosis both require

energy

large molecules need

energy

the sodium potassium pump requires

energy

protein kinases

enzyme that transfers phosphate groups from ATP to a protein, phosphorylating the protein

membrane proteins are the mosaic part of the model. What are the main two categories

integral proteins peripheral proteins

What processes in human depend on GPCR's? What are examples of errors in GPCR signaling

involved in embryonic development and sensory reception errors can cause cholera, whooping cough, and botulism

The second type of receptor describe is the receptor tyrosine kinases. Explain what a kinase enzyme does

it catalyzes the transfer of a phosphate group

How does the tyrosine kinase function in the membrane receptor

it catalyzes the transfer of a phosphate group from ATP to the amino acid tyrosine on a substance protein

why could glycogen phosphorylase be activated only when epinephrine was added to intact cells?

it does not work with just the enzyme and susbstrate because the plasma membrane helps transmit the epinephrine signal and there are intermediate steps

phospholipids are amphipathic. what does this mean

it has both a hydrophilic region and a hydrophobic one hydrophilic tails and hydrophobic head

________________ is an enzyme that catalyzes the transfer of a phosphate group

kinase

How do scaffolding proteins enhance a cellular response

large relay proteins to which several other relay proteins are simutaneously attached which increases the efficiency of signal transduction

G protein coupled receptors are the

largest family of cell-surface receptors

hypo means

less solute

Role of three molecules in first step of ion channel receptors

ligand, ligand-gated ion channel receptor, ions

What are three examples of signals that cells may receive?

light, touch, chemicals

Local Signaling: In many other cases, animal cells communicate using secreted messenger molecules that travel only short distances. What are these molecules called?

local regulators

the transmission of neurotransmitters across the synapse is considered a local signal while the transmission of a nerve signal through the body is considered a

long distance signal

active transport moves from

low to high

cholesterol:

maintain membrane permeability and fluidity

A ___________________ _____________ can exist as a stable boundary between two aqueous solutions

phospholipid bilayer

most signal receptors are

plasma membrane proteins

Tyrosine-Kinase receptors are

plasma membrane receptors that have enzymatic activity

A water molecule is held together by *polar covalent bonds* (intramolecular bonding). What does this mean

polar covalent bond: a bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive. This makes it a *polar molecule* meaning thats its overall change in unevenly distributed

Hydrogen has a positive/negative charge and oxygen has a positive/negative charge.

positive//negative *note*: hydrogen can bond to other things too like nitrogen

Phosphorylation and dephosphorylation of proteins is a widespread cellular mechanism for regulating

protein activity

what does cAMP usually activate

protein kinase A, which phosphorylates various other proteins

Phosphorylation

protein kinases transfers phosphates from ATP to a protein, a process called phosphorylation

the main electrogenic pump in planta, fungi, and bacteria is a

proton pump

What is quorum sensing? How is it related to biofilms

quorum sensing: a concentration of signaling molecules that allow bacteria to sense local population density, A biofilm is formed by quorum sensing

the fluid mosaic model states that a membrane is a fluid structure with a mosaic of various proteins embedded in it. Proteins are not

randomly distributed in the membrane

Small or hydrophobic chemical messengers can

readily cross the membrane and activate receptors

A signal transduction pathway has three stages. What are they in order

reception transduction response

isotonic

referring to a solution that, when a surrounding cell, causes no net movement of water into or out of the cell

hypertonic

referring to a solution that, when surrounding a cell, will *lose water*

hypotonic

referring to a solution that, when surrounding a cell, will cause the cell to *take up water*

Often, more than one signal transduction pathway can be triggered at once, helping the cell

regulate and coordinate many aspects of cell growth and reproduction

how does cell signaling provide evidence to justify the claim that all life is related

scientists have found evidence for evolutions since the same set of cell signaling show up in all species

The plasma membrane exhibits ________________ ___________________ allowing some substances to cross more easily than others

selective permeability

Communication among microorganisms provides insight into how cells?

send, receive, and respond to signals

step 1

shows a ligand gated ion channel receptor in which the gate remains closed until a ligand binds to the receptor

example of active transport

sodium-potassium pump

the prefix refers to the amount of

solute

describe a hypotonic solution

solute concentration is less outside than that inside the cell (more water); cell gains water

describe an isotonic solute

solute concentration is the same as that inside the cell; no net water movement across the plasma membrane

cell-cell recognition

some glycoproteins serve as identification tags that are specifically recognized by membrane proteins of other cells. This type of binding is short-lived

active transport

some transport proteins act as pumps, moving substances across a membrane against their concentration (or electrochemical) gradients. Energy for this work is usually supplied by ATP.

what is the function of GTP (guanosine triphosphate)

source of cellular energy

How does a hormone qualify as a long-distance signaling example

specialized endocrine cells secrete hormones into the body, often blood

give examples of hydrophobic messengers and their functions

steroid/thyroid hormones of animals an activated hormone receptor complex can act as a transcription factor and turn on specific genes

what happens when a ligand molecule (a signaling molecule) binds to the receptor protein

the gate opens/closes allowing a specific ion, Na+ or Ca2+ through a channel in the receptor. ex: neurotransmitter across the synapse

ions

the gate opens/closes, allowing of blocking the flow of specific ions through a channel in the receptor

steroid 3

the hormone receptor complex enters the nucleus and binds to specific genes

describe the hydrophobic regions of an integral protein

the hydrophobic regions of an integral protein consists of one or more stretches of non polar amino acids, often coiled into alpha helices.

What is the important relationship between the second messneger and protein kinase A

the immediate effect of cAMP is the activation of serine/threonine kinase usually called protein kinase A and it phosphorylates other proteins

describe a chemical force

the ion's concentration gradient

steroid 5

the mRNA is translated into a specific protein

What is a capsase

the main proteases of apoptosis

the current accepted model is the fluid mosaic model. Describe this model

the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids

define plasmolysis

the membrane pulls away from the cell wall causing the plant to wilt

In what body system are ligand-gated ion channels and voltage hated ion channels of particular importance

the nervous system

define molarity

the number of moles of solute per liter of solution unit concentration used for aquarous solutions

what are aquaporins

the passage of water molecules through the membrane in certain cells is greatly facilitated by these channel proteins

example of an electrogenic pump

the sodium potassium pump in animal cells

Steroid - 1

the steroid hormone aldosterone passed through the plasma membrane

solute

the substance that is dissolved

reception

the target cells detection of a signaling molecule

diffusion

the tendency for molecules to spread out evenly into the availble space; directional

response:

the transduced signal triggers a specific response in the target cell

What is membrane potential

the voltage across the membrane

define membrane potential

the voltage difference across a membrane

Eventually,

the water/solute concentration will be at equilibrium.

G-protein Coupled Receptor

thee receptor are extremely widespread and diverse.

Tyrosine-kinase receptors

they are especially effective when the cell needs to be trigger several signal transduction pathways and cellular responses at once. This system also helps the cell regulate and coordinate many aspects of cell growth and reproduction

ion channel receptors:figure

this figure shows the flow of ions into the cell. Ion channel receptors can also stop the flow of ions. These simple membrane receptors are explained in three steps.

membranes must be fluid to

to work properly usually as fluid as salad oil

are transport proteins specific? Cite an example that supports your response

yes they are specific to the substance it moves, allowing only a certain substance to cross the membrane specific carrier protein in the plasma membrane of red blood cells transport glucose across the membrane 50,000 times faster than glucose can on its own It is so selective that it rejects fructose, an isomer of glucose

signal transduction pathway

transduced signal triggers a specific response in the target cell different pathway

an integral protein that spans the membrane is called a

transmembrane protein

ligand gated ion channel receptor

transmembrane protein containing a pore that opens or closes as it changes shape

the differences in charges results in the

transmission of nerve impulses

study figure 7.7 in your text. Use it to briefly describe the following major function of membrane proteins

transport enzymatic activity signal transduction cell-cell recognition intercellular joining attachment to cytoskeleton and ECM

describe an electrogenic pump and give an example

transport protein that generates voltage across a membrane

hydrophilic molecules must pass through the cell membrane using?

transport proteins

what types of proteins are associated with facilitated diffusion

transport: channel and carrier

a receptor tyrosine kinase can

trigger multiple signal transduction pathways at once

the neurotransmitter binds to the receptor site on the target cell,

triggering a response

The cytoplasmic side of these receptors function as

tyrosine kinases, transferring a phosphate group from ATP to tyrosine on a protein

carrier protein

undergo a subtle change in shape that translocates the solute binding site across the membrane

What do ligands have to do with receptor mediated endocytosis

used when cholesterol travels in the blood in particles called LDL's which binds to LDL receptors on plasma membranes and enter the cell by endocytosis. The LDL's act as ligands.

Describe the resposne

very specific

cell wallas in plants help maintain

water balance

step 2: show what has happened with the binding of the ligand to the receptor

when the ligand binds to the receptor and the gate opens, specific ions can flow through the channel and rapidly change the concentration of the ion inside the cell