Chapter 8 Cell-Cell Interactions Flashcards
Primary Cell Wall
The outermost layer of a plant cell wall, made of cellulose fibers and gelatinous polysaccharides, that defines the shape of the cell and withstands the turgor pressure of the plasma membrane.
Pectin
A gelatinous polysaccharide found in the primary cell wall of plant cells. Attracts and holds water, forming a gel that helps keep the cell wall moist.
Turgor Pressure
The outward pressure exerted by the fluid contents of a plant cell against its cell wall.
Secondary Cell Wall
The inner layer of a plant cell wall formed by certain cells as they mature. Provides support or protection.
Lignin
A substance found in the secondary cell walls of some plants that is exceptionally stiff and strong. Most abundant in woody plant parts.
Extracellular Mix (EMC)
A complex meshwork of proteins (e.g., collagen, fibronectin) and polysaccharides secreted by animal cells and in which they are embedded.
What is the Extracellular Mix (EMC) most important function?
Structural support
The fibrous component of animal Extracellular Mix (EMC) is dominated by _______________.
A cable like protein called collagen
Collagen
A fibrous, pliable, cable-like glycoprotein that is a major component of the extracellular matrix of animal cells. Various subtypes differ in their tissue distribution.
Integrins
Any of a class of cell-surface proteins that bind to fibronectins and other proteins in the extracellular matrix, thus holding cells in place.
Fibronectins
An abundant protein in the extracellular matrix that binds to other ECM components and to integrins in plasma membranes; helps anchor cells in place. Numerous subtypes are found in different tissues.
Why is the direct linkage between the cytoskeleton and EMC important?
In addition to keeping individual cells in place, it helps adjacent cells adhere to each other via their common connection to the EMC.
If it breaks down, cancer can develop.
Metastasis
The spread of cancerous cells from their site of origin to distant sites in the body where they may establish additional tumors.
*Happens when EMC-cytoskeleton linkage break down and cells grow uncontrollably forming a tumor, can break away and form tumors throughout the body
What is the state of being composed of many cells that adhere to each other and do not all express the same genes with the result that some cells have specialized functions.
Multicellularity
______________ organisms are made up of cells that adhere to each other and have distinctive structures and functions.
Multicellularity
A group of similar cells that function as a unit, such as muscle tissue or epithelial tissue.
Tissue
What is the middle lamella?
It connects adjacent plant cells and is made of gelatinous polysaccharides called pectins.
*It serves as glue.
Epithelium
An animal tissue consisting of sheet-like layers of tightly packed cells that lines an organ, a duct, or a body surface. Also called epithelial tissue.
Tight junction
A type of cell-cell attachment structure that links the plasma membranes of adjacent animal cells, forming a barrier that restricts movement of substances in the space between the cells. Most abundant in epithelia (e.g., the intestinal lining). Compare with desmosome and gap junction.
_____________ is a cell-cell attachment imposed of specialized proteins in the plasma membranes of adjacent animal cells.
tight joint
Why is tight joint important ?
It forms a tight barrier between organs and prevents ions from leaking in our out. Important for organs like the stomach and the intestines.
Desmosome
A type of cell-cell attachment structure, consisting of cadherin proteins, that binds the cytoskeletons of adjacent animal cells together. Found where cells are strongly attached to each other. Compare with gap junction and tight junction.
Selective adhesion
The tendency of cells of one tissue type to adhere to other cells of the same type.
Antibody
An immunoglobulin protein, produced by B cells, that can bind to a specific part of an antigen, tagging it for attack by the immune system. All antibody molecules have a similar Y-shaped structure and, in their monomer form, consist of two identical light chains and two identical heavy chains.
Cadherins
Any of a class of cell-surface proteins involved in cell adhesion and important for coordinating movements of cells during embryological development.
Synaptic signaling involves
A) endocrine signals
B) paracrine signals
C) autocrine signals
D) neurotransmitters
D) neurotransmitters
In synaptic signaling, a neurotransmitter is passed from one cell to another.
________________ provide the physical basis for selective adhesion in may cells and are a critical component of the desmosomes that join mature cells.
Cadherins
In plants, gaps in cell walls create direct connections between the cytoplasm of adjacent cells. At these connections, named _____________ the plasma membrane and they cytoplasm of the two cells are continuous.
plasmodesmata
*smooth ER runs through theses holes.
What are communication portals in plant cells?
plasmodesmata
What is the key feature of gap junctions ?
to specialize proteins that create channels between animal cells
*small molecules such as amino acids, sugars, and nucleotides move between the channels.
____________ are usually small molecules and are typically present in minute concentrations.
Hormones
In cell-cell signaling, most ____________________ signals diffuse across the plasma membrane and enter the cytoplasm of their target cell.
lipid-soluble
Large or _______________ cell-cell signals re lipid-soluble and do not cross the plasma membrane.
hydrophilic
*To affect a target cell, they have to be recognized at the cell surface.
How do cells receive and respond to signals from distant cells?
signal reception
signal processing
signal response
signal deactivation
In signal reception, the presence of an appropriate receptor dictates what?
which cells will respond to a particular hormone.
In signal reception, what are two critical points?
Receptors are dynamic: the sensitivy of a cell to a particular hormone may change over time.
receptors can be blocked: that’s why beta blockers are prescribed
A protein that changes it shape and activity after binding to a signaling molecule.
signal receptor
In signal reception, receptors that respond to lipid-soluble signals are locate where?
inside the cell, because the signals readily diffuse through the plasma membrane.
In signal reception, the majority of signals are located where?
in the plasma membrane.
*they can bind to signals that cannot or do no cross the plasma membrane
When lipid-soluble signals enter a cell, how is the information processed?
directly, w/o any intermediate steps
Lipid-soluble signals are processed directly, what are the steps?
1) arrival of signal: steroid hormone diffuses across plasma membrane into cells
2) signal reception: Hormone binds to receptor, including conformational change
3) Direct signal response: Hormone-receptor complex binds to DNA, including change in gene expression
Explain some cell-cell signals that enter the cell and bind to receptors in the cytoplasm.
Because they are lipids, steroid hormones can diffuse across the plasma membrane and bind to signal receptors inside the cell. The hormone-receptor complex is transported to the nucleus and binds to genes, changing their activity.
When a signal binds at the cell surface it triggers ___________, the conversion of the signal from one form to another.
signal transduction
*A long and often complex series of events ensues, collectively called a signal transduction pathway.
In a cell, signal transduction converts an extracellular signal to an _____________.
intracellular signal
Lipid-insoluble signals require transduction. What is the process?
1) signal reception
Hormones
Any of numerous different signaling molecules that circulate throughout the body in blood or other body fluids and can trigger characteristic responses in distant target cells at very low concentrations.
Signal Receptor
Any cellular protein that binds to a particular signaling molecule (e.g., a hormone or neurotransmitter) and triggers a response by the cell. Receptors for water-soluble signals are transmembrane proteins in the plasma membrane; those for many lipid-soluble signals (e.g., steroid hormones) are located inside the cell.
Signal transduction
The process by which a stimulus (e.g., a hormone, a neurotransmitter, or sensory information) outside a cell is amplified and converted into a response by the cell. Usually involves a specific sequence of molecular events, or signal transduction pathway.
In a cell, signal transduction converts an extracellular signal to an _____________.
intracellular signal
Lipid-insoluble signals require transduction. What is the process?
1) Signal reception (1st it’s a intercellular signal)
2) Signal transduction from intercellular signal to intracellular signal
3) Signal amplification (in most cases)
4) Signal response. (For example, specific genes ore proteins are activated or deactivated)
____________ are present in minuscule concentrations but trigger large responses from cells. Why?
Hormones; via signal amplification
How does signal amplification work?
When a hormone arrives a the cell surface, the message it transmit may be amplified as it changes form. (like a radio speaker)
In cells, signal transduction begins ____________; amplification occurs inside.
at the plasma membrane
What are two types of signal transduction and amplification systems?
(1) G proteins
(2) enzyme-linked receptors
______________ initiate the productionof a n intracellular or “second” messenger
G proteins
_________________ receptors trigger the activation of series of proteins inside the cell, through the addition of phosphate groups.
Enzyme-linked
Many signal receptors span the plasma membrane and are closely associated wit the peripheral membrane proteins inside the cell called _______________.
G proteins
What happens when G proteins are activated by a signal receptor?
they trigger the key steps in signal transduction: the production of a messenger inside the cell. They link the receipt of an extracellular signal to the production of an intracellular signal.
How did G protein get its name?
they bind to guanosine triphosphate (GTP) and guanosine diphosphate (GDP).
*GTP is a nucleoside triphosphate that is similar in structure to adenosine triphosphate (ATP).
**nucleoside triphosphate have high potential energy b/c their three phosphate groups have four negative charges close together. The cluster of charges result in electrons repulsing each other and moving father from nearby nuclei.
What happens when GTP binds to a protein?
the addition of the negative charges alter the proteins shape.
- Changes in shape produce changes in activity
- G proteins are turned on or activated when they bind GTP; they are turned off or inactivated when a phosphate group drops away to form GDP.
a nonprotein signaling molecule that elicits a response to the first messenger (the signal that arrived at the cell surface)
second messenger
The arrival of a single hormone molecule can stimulate the production of many _______________ molecules, the signal transduction even amplifies the original signal.
second messenger
______________ are enzymes that activate or inactivate other proteins by adding a phosphate group to them.
protein kinases
Name two important notes about second messengers
1) They aren’t restricted to a single role or single cell type~the same second messenger can initiate dramatically different events in different cell types
2) It is common for more than one second messenger to be involved in triggering a cell’s response to the same extracellular signal.
Name two important notes about second messengers
1) They aren’t restricted to a single role or single cell type~the same second messenger can initiate dramatically different events in different cell types
2) It is common for more than one second messenger to be involved in triggering a cell’s response to the same extracellular signal.
A nonprotein signaling molecule produced or activated inside a cell in response to stimulation at the cell surface. Commonly used to relay the message of a hormone or other extracellular signaling molecule.
Second messenger
Protein Kinases
An enzyme that catalyzes the addition of a phosphate group to another protein, typically activating or inactivating the substrate protein.
receptor tyrosine kinases (RTKs)
Any of a class of cell-surface signal receptors that undergo phosphorylation after binding a signaling molecule. The activated, phosphorylated receptor then triggers a signal-transduction pathway inside the cell.
Instead of activating a nearby G protein, enzyme-linked receptors transduce the signal from a hormone by directly catalyzing a reaction inside the cell. This is called?
receptor tyrosine kinases (RTKs)
______________________ trigger a phosphorylation cascade.
enzyme linked receptors
G proteins trigger _________________ and some ____________ result in the production of second messengers.
phosphorylation cascades; phosphorylation cascades
the signal transduction event has two results, what are they?
1) It converts an easily transmitted extracellular message into an intracellular message
2) in many cases it amplifies the original message many times over.
In signal response, second messengers or cascade or proteins phosphorylation events may:
1) change which genes are being expressed in the target cell
2) or activate or deactivate a particular target protein that already exists in the cell; an enzyme, a membrane channel, or a protein that activates certain genes.
Phosphorylation Cascade
A series of enzyme-catalyzed phosphorylation reactions commonly used in signal transduction pathways to amplify and convey a signal inward from the plasma membrane.
What is cross-talk
Interactions among signaling pathways that modify a cellular response.
What is quorum sensing?
Cell-cell signaling in bacteria, in which cells of the same species communicate via chemical signals. It is often observed that cell activity changes dramatically when the population reaches a threshold size, or quorum.
In bacteria, cell-cell communication is called ______________.
quorum sensign
_____________ are hard, polysaccharide-rich substances that encases the cells and attach them to a surface
biofilm
______________, which bind cells together, are found predominantly in epithelial tissues, such as the lining of the intestines. _________________ form a barrier that prevents fluids from moving between the intestinal space and the space between cells.
tight junctions; tight junctionsDesmosomes
________________, or anchoring junctions, appear as thickened patches in the cell membrane region between two cells. ________________ contain specialized proteins, such as keratin (the same protein found in fingernails and hair), that increase the rigidity of tissues. ___________________— such as those found in epithelium, smooth muscle, and many other animal tissues— are button like junctions that bind cells together and also function as anchors for fibers in the ____________________.
Desmosomes; Desmosomes; Desmosomes; cycoskeleton
In _______________, or communicating junctions, two cells are separated by a small gap, which is bridged by specialized channels that allow the passage of water and small molecules. ________________ help coordinate the activities of adjacent cells. For example, a hormone that stimulates one cell will often activate adjacent cells as well by the passage of intracellular signals through ________________.
gap junctions; gap junctions; gap junctions
Which of these cell junctions form a barrier to the passage of materials?
desmosomes (anchoring junctions) plasmodesmata keratin fibers gap (communicating) junctions tight junctions
Tight junctions form a barrier that prevents fluids from moving between cells.
The primary role of _____ is to bind animal cells together.
The primary role of _____ is to bind animal cells together.
tight junctions gap (communicating) junctions the cytoskeleton plasmodesmata desmosomes
The primary role of desmosomes (anchoring junctions) is to bind cells together
_____ aid in the coordination of the activities of adjacent animal cells.
_____ aid in the coordination of the activities of adjacent animal cells.
Tight junctions Keratin fibers Desmosomes Plasmodesmata Gap (communicating) junctions
Gap junctions allow for the passage of material between cells, thus facilitating communication between these cells.
An open channel in the cell wall of a plant through which strands of cytosol connect from an adjacent cell.
plasmodesma
Like gap junctions in animal cells, ______________ allow the free exchange of small molecules and help coordinate the activities of neighboring cells.
plamodesmata
Membrane protein complexes that strengthen the adhesion between adjacent cells, like rivets, to protect against pulling forces
desmosomes found in animal cells
Small channels that from across the plasma membranes of adjacent cells; especially important in intercellular communication
gap junctions; animal
Membrane proteins that create a watertight seal between cells
tight junctions; animals
Small channels between cells that are otherwise surrounded by walls; enabled movement of water and solutes between cells
plasmodesmata; plant
Polysaccharides that is used to synthesize cell walls, which protect cells and help maintain their shape
cellulose; plant
Long fibers of protein found in extracellular matrix that provide structural support for cells
collagen; animal
For the receiving cell, there are three stages in the signaling process:
reception, transduction, and cell response.
A signal transduction pathway is initiated when a _____ binds to a receptor.
G protein tyrosine kinase cyclic AMP signal molecule calmodulin
The binding of a signal molecule to a receptor initiates a signal transduction pathway.
Which of these is the second of the three stages of cell signaling?
gene activation reception binding of a neurotransmitter to a plasma membrane receptor transduction cell response
Transduction is the second of the three stages of cell signaling.
Which of these is the second of the three stages of cell signaling?
gene activation reception binding of a neurotransmitter to a plasma membrane receptor transduction cell response
Transduction is the second of the three stages of cell signaling.
