CH11 BIO MO2A

communication of cells

communication of cells

in order to coordinate their activities, respond to environmental changes, and maintain proper functioning within a multicellular organism

responses when cells detect change in environment

altering gene expression, changing their shape or movement, initiating cell division or differentiation, producing specific proteins, releasing signaling molecules, and adjusting their metabolic activity depending on the specific environmental cue and the type of cell involved; essentially, they adapt to maintain homeostasis within the changing conditions.

Receptor

a molecule that receives a signal and causes a specific effect in a cell.

Protein (structure) that detects conditions in environment

Ligand

a molecule that binds to another specific molecule, usually a larger protein called a receptor, to initiate a cellular response by delivering a signal within or between cells

G Protein

a type of protein within a cell that acts as a molecular switch, transmitting signals from external stimuli to the cell's interior by binding to guanine nucleotides like GTP (active state) and GDP (inactive state), essentially turning a signal "on" or "off" depending on its bound nucleotide

involved in signal transduction

Kinase

an enzyme that adds phosphate groups to other molecules, such as proteins, lipids, or nucleic acids

A type of enzyme (a protein that speeds up chemical reactions in the body) that adds chemicals called phosphates to other molecules, such as sugars or proteins

Second messenger

a small molecule produced inside a cell that relays a signal received by a cell surface receptor from an extracellular signaling molecule (the "first messenger") to intracellular targets, triggering specific cellular responses by activating various signaling pathways within the cell

examples of ligand

hormones like insulin, estrogen, and cortisol, neurotransmitters like dopamine and serotonin, growth factors like epidermal growth factor (EGF), and small molecules like nitric oxide

examples of second messengers

a small molecule produced inside a cell that relays a signal received by a cell surface receptor from an extracellular signaling molecule (the "first messenger") to intracellular targets, triggering specific cellular responses by activating various signaling pathways within the cell

responses to signal transduction pathways

changes in gene expression (transcription and translation), protein activity through phosphorylation or conformational changes, cell growth, differentiation, migration, apoptosis (programmed cell death), metabolism alterations, and even changes in cellular behavior depending on the specific signal received and the cell type involved

function of the alpha and a mating factors

act as chemical signals to initiate the mating process by binding to specific receptors on the surface of the opposite cell type, ultimately leading to cell fusion and the formation of a diploid cell

quorum sensing

a cell-to-cell communication process that allows bacteria to sense their population density and adjust their gene expression accordingly

gap junctions

clusters of channels that connect the cytoplasm of adjacent cells, allowing small molecules to pass directly between them

plasmodesmata

microscopic channels that traverse the cell walls of plant cells

cell-cell recognition

the process by which cells identify and communicate with each other through specific molecular interactions. This typically involves proteins on the cell surface, such as glycoproteins and glycolipids, which allow cells to recognize similar or different cell types, facilitating processes like tissue formation, immune response, and cellular signaling.

paracrine signaling

a form of cell communication where a cell produces signals (such as hormones or neurotransmitters) that affect nearby target cells within the same tissue. This type of signaling is crucial for local cellular responses and plays a significant role in processes like tissue repair, immune responses, and development. The signals typically act over short distances, influencing neighboring cells without entering the bloodstream.

synaptic signaling

a form of communication between neurons where neurotransmitters are released from the presynaptic neuron and bind to receptors on the postsynaptic neuron. This process allows for the transmission of signals across synapses, facilitating rapid communication within the nervous system.

hormonal signaling

refers to the process by which hormones, which are chemical messengers produced by glands in the endocrine system, are released into the bloodstream and travel to target organs or tissues. These hormones bind to specific receptors on target cells, triggering a response that regulates various physiological processes, including growth, metabolism, and mood. This communication system is crucial for maintaining homeostasis in the body.

Sutherland’s experiment

epinephrine regulates glycogen phosphorylase activity in the liver by activating a "second messenger" molecule, later identified as cyclic AMP (cAMP), which in turn activates phosphorylase kinase, leading to the phosphorylation and activation of glycogen phosphorylase, thus initiating glycogen breakdown

isolating liver cell fractions and demonstrating that epinephrine, when added to the cell debris, produced a heat-stable "factor" which, when added back to the cell supernatant, activated glycogen phosphorylase, thus identifying this factor as cyclic AMP (cAMP) and establishing the concept of a second messenger in hormone signaling

reception

the process by which a cell detects a signal from its environment

transduction

the process where a virus transfers genetic material (DNA) from one bacterium to another

response

the way an organism changes its behavior or physiology in response to a stimulus

structure of G-protein coupled receptors

a single polypeptide chain that spans the cell membrane seven times, forming seven transmembrane alpha helices, with an extracellular amino terminus and an intracellular carboxyl terminus

where the ligand binds and what happens to the receptor

binds to a specific site on a receptor protein, usually located on the cell membrane, which triggers a conformational change in the receptor's structure, allowing it to initiate a cellular response by activating downstream signaling pathways within the cell

how ligand-binding is transduced to the G protein. What happens to the G protein?

it triggers a conformational change in the receptor, which then acts as a guanine nucleotide exchange factor (GEF) to facilitate the exchange of GDP for GTP on the G protein's alpha subunit; this exchange causes the G protein to dissociate into its alpha and beta-gamma subunits, allowing them to activate downstream signaling pathways within the cell.

target of the active G protein. Where does the active G protein go and what does it do?

travels within the cell membrane to reach its target, which is typically an enzyme or an ion channel, where it directly interacts to trigger a specific cellular response by activating the enzyme or modulating the ion channel activity

how the G protein is inactivated

when its alpha subunit hydrolyzes the bound GTP molecule back to GDP, causing it to dissociate from the effector protein and reassociate with the beta and gamma subunits, returning to its inactive heterotrimeric state

agonist

a chemical substance that binds to a receptor on a cell and activates it, causing a biological response

molecule that mimics or enhances response

antagonist

A substance that acts against and blocks an action

effects of epinephrine

is a hormone released by the adrenal glands in response to stressful situations, triggering the "fight or flight" response by causing a range of effects including increased heart rate, blood pressure, blood sugar levels, dilated pupils, and rapid breathing

epinephrine antagonist

can lower blood pressure and slow heart rate by dilating blood vessels

epinephrine agonist

a substance that mimics the action of epinephrine (adrenaline) by binding to and activating adrenergic receptors. This can lead to effects such as increased heart rate, bronchodilation, and enhanced blood flow to muscles, commonly used in treatments for conditions like asthma and anaphylaxis.

mechanism of cholera toxin

binding to receptors on intestinal epithelial cells, then entering the cell and activating an enzyme that significantly increases the production of cyclic AMP (cAMP), leading to massive secretion of fluids and electrolytes into the intestinal lumen, causing the characteristic watery diarrhea of cholera

kinase (Phosphorylation)

an enzyme that attaches a phosphate group to a protein or other molecule, such as a sugar

protein phosphorylation cascade

a series of reactions that involves the addition of phosphate groups to proteins, which can lead to changes in the cell. This process is a key part of many biological processes, including signal transduction and developmental decisions

importance of phosphatases

they play a vital role in regulating cellular processes by removing phosphate groups from molecules, a process called dephosphorylation, which is essential for controlling protein activity and signaling pathways within a cell; essentially acting as an "off switch" to counter the actions of kinases that add phosphate groups (phosphorylation) to proteins, thus maintaining a dynamic balance in cellular function.

second messenger

a small molecule or ion that relays signals from cell-surface receptors to target proteins within the cell

where cyclic AMP is produced, its effect and how it is broken down

within the cell membrane, specifically by the enzyme adenylyl cyclase, which converts ATP into cAMP; its primary effect is to activate protein kinase A (PKA) by binding to its regulatory subunit, leading to downstream cellular responses like changes in gene expression, metabolism, and cell behavior; cAMP is broken down back into AMP by phosphodiesterase enzymes, effectively terminating the signal

where calcium ions are normally found in a resting cell and the effect when they are released into the cytoplasm

primarily stored within specialized compartments called the sarcoplasmic reticulum (SR) in muscle cells, and the endoplasmic reticulum (ER) in other cell types; meaning the highest concentration of calcium is found within these internal storage structures, not in the cytoplasm itself. When calcium ions are released into the cytoplasm, it acts as a critical signaling molecule, triggering various cellular processes depending on the cell type, most notably muscle contraction in muscle cells

the role of IP3

acts as a crucial intracellular second messenger, primarily responsible for triggering the release of calcium ions from intracellular stores like the endoplasmic reticulum (ER) by binding to specific IP3 receptors, thereby initiating a wide range of cellular processes including muscle contraction, cell proliferation, fertilization, and neuronal signaling

differences between monomer and dimer

Monomer units are single units of sugars called monosaccharides. Dimer units are double units of sugars called disaccharides

What is the form of the inactive receptor and what is the form after ligand binding?

typically in a "closed" or "folded" conformation before ligand binding, while after ligand binding, the receptor transitions to an "open" or "activated" conformation due to a conformational change, allowing it to interact with downstream signaling molecules

signal transduction

process of communicating changes in environment to interior of cell

dimerization

the process of two molecules joining together to form a new compound, or dimer, with a new metallic coordination number

the substrate for active receptor tyrosine kinase. What is meant by autophosphorylation?

its primary substrate is itself; meaning the receptor protein itself acts as the target for phosphorylation on specific tyrosine residues, a process called autophosphorylation where the kinase domain of the receptor phosphorylates its own tyrosine residues, typically upon dimerization induced by ligand binding, which activates the kinase domain and allows it to phosphorylate other tyrosine residues on the receptor molecule

Define relay protein and explain the effect of active receptor tyrosine kinase on relay proteins.

a protein within a signal transduction pathway that receives a signal from an upstream molecule and transmits it to a downstream molecule, essentially acting as a middleman to pass the signal along the chain of events within a cell; when an active receptor tyrosine kinase (RTK) is present, it can phosphorylate these relay proteins on tyrosine residues, which typically activates them and allows them to further propagate the signal downstream in the signaling cascade.

processes regulated by RTKs

Cell growth, Cell differentiation, Cell survival, Cell migration, Cell cycle control

effect of overactive RTK

uncontrolled cell growth, proliferation, and differentiation, often associated with cancer development, as abnormal RTK signaling disrupts normal cellular processes like growth, motility, and survival, resulting in increased aggressiveness and poor prognosis in various cancers; essentially

ion channel

a specialized protein embedded within a cell membrane that acts as a pore, allowing specific ions to pass through, thereby regulating the movement of electrical charge across the cell membrane and playing a crucial role in various cellular processes like nerve impulse transmission and muscle contraction

gating

the process by which an ion channel protein changes its conformation, opening or closing its ion conduction pathway

the effect of ligand binding to ion channel receptor

it causes a conformational change in the protein structure, which opens the channel pore, allowing specific ions to flow across the cell membrane, effectively triggering a cellular response by altering the membrane potential

processes regulated by opening of Calcium ion channels

Calcium channels are membrane proteins that regulate the flow of calcium ions into and out of cells, and the opening of these channels triggers a number of cellular processes

Muscle contraction, Gene transcription, Neurotransmitter release, Synaptic transmission, Immune system activation

processes regulated by opening of sodium channels

depolarization in a cell, which is the rapid increase in membrane potential due to the influx of positively charged sodium ions, initiating electrical signals like action potentials in excitable cells like neurons and muscle fibers.

which types of receptors are located inside the cell and why?

intracellular or cytoplasmic receptors, are primarily found in the cytoplasm or nucleus and are designed to respond to small, hydrophobic signaling molecules that can readily diffuse across the cell membrane, like steroid hormones (e.g., testosterone, estrogen), thyroid hormone, and vitamin D, which directly influence gene expression by binding to DNA once inside the nucleus; this is why they are situated inside the cell as opposed to on the cell surface.

the effect of ligand binding to intracellular receptor

it triggers a conformational change in the receptor protein, which then allows it to translocate to the nucleus where it interacts with DNA, ultimately leading to changes in gene expression by activating or inhibiting transcription of specific genes depending on the ligand and receptor involved

apoptosis

a process of programmed cell death, where a cell actively self-destructs in a controlled and orderly manner, eliminating unwanted or damaged cells from an organism, often occurring during development and as part of normal tissue turnover; it is characterized by cell shrinkage, membrane blebbing, nuclear fragmentation, and the formation of apoptotic bodies that are readily engulfed by phagocytes

role of caspases in apoptosis

act as the primary executioners of apoptosis (programmed cell death), essentially initiating and carrying out the cellular dismantling process by cleaving specific proteins within the cell, leading to the orderly breakdown and removal of apoptotic cells

the importance of apoptosis in development

is crucial for proper development in organisms as it allows for the selective elimination of unwanted cells, shaping organs and tissues by removing excess cells, and ensuring the correct formation of structures like digits by carving out spaces between them

B adrenergic receptor

one hormone receptor that binds epinephrine

autophosphorlate

self add phosphate groups

what happens when nutrient availability is low in myxobacteria

the vegetative spread of the myxobacteria is constrained and the population initiates a developmental program that culminates with the formation of multicellular, spore-filled fruiting bodies. Fruiting body formation requires a solid surface to allow motility, a threshold population density, recognition at the cellular level of the nutrient downshift, and a complex series of inter- and intracellular signaling that proceeds in distinct morphological stages separated in time and space

the response to secretion of signaling molecule in myxobacteria

involves cell-to-cell contact signaling, allowing cells to sense the population density and initiate developmental processes like movement, aggregation, and sporulation, with the C-signal playing a key role in coordinating cell behavior and patterning the fruiting body structure

what happens when the mating factors bind to corresponding receptor

When mating factors bind to their corresponding receptors, a series of events is triggered that initiates the mating response in yeast cells