Unit 4: Cell Communication and Cell Theory
the checkpoint in cell division:
- G1 checkpoint at the G1/S transition - G2 checkpoint at the G2/M transition - spindle checkpoint at the transition from metaphase to anaphase
what is a tyrosine kinase receptor and state breifly what it does
- an enzyme that attaches a phophate ground to ADP - transfers phosphate groups to tyrosine molecules
what are examples of molecules used as second messengers
- calcium ion - cyclic AMP
why is cell division important for both single-celled and multi cellular organisms?
- cell division is the only way single-celled organisms produce - multi cellular needs to for growth/repair
metaphase
- chromosomes are lined up - chromatids are attached to separate spindle fibers
what major events occur in teleaphase?
- chromosomes arrive at opposite poles and begin to decondense - nuclear envelope material surrounds each set of chromosomes - the mitotic spindle breaks down
what major events occur in prophase?
- chromosomes condense and become visoble - spindle fibers emerge from the chromosomes - nuclear envelope breaks down - nucleolus disappears
what major events occur in prometaphase?
- chromosomes continue to condense - kinetocores appear at the centromeres - mitotic spindle microtubles attach to kinetochores - centrosomes move toward opposite poles
prometaphase
- chromosomes finish condensing - nuclear envelope breaks down - mitotic spindle grows more and start to grab chromosomes - kinetochores develop at the centrosomes of the chromosomes
early prophase
- chromosomes start to condense - the mitotic spindle begins to form - the nucleolus disappears
what major events occur in anaphase?
- cohesin proteins binding the sister chromoatids together break down - sister chromatids are pulled toward opposite poles - non-kinetochore spindle fibers lengthen, elongating the cell
what are the most important cell cycle regulators?
- cyclins - cdks - APC/C
telephase
- cytokinesis takes place - mitotic spindle breaks down - chromosomes decondense, returning to chromatin - new nuclei form around the chromosomes
what does G2 checkpoint check?
- damages in DNA - if all DNA was copied
two types of cell signaling
- direct contract - sending signal molecules
cell signaling involves communication by:
- direct contract between cells - sending signal molecules across short/long distances between cells
when does auntocrine signaling occur?
- during development - in cancer/metastasis - regulating pain - during viral infections
when does an autocrine signaling occur?
- early development - regulates pain - programmed death if the cell is ill
what are initiation and inhibition of cell division triggered by? provide some examples
- events external to the cell when it is about to begin the replication process - death of a nearby cell and the release of a growth hormone
what are the three main components of a cell surface receptor?
- external ligand-binding domain - hydrophobic membrane spanning region - intracellular domain inside the cell
what are checkpoints and what are the three major ones in the cell cycle?
- external signals and internal controls - one at the end of G1, at the transition of G2 and M, and one during metaphase
what do we need cell division for?
- growth - tissue repair - replacement
what disorders have been known to be caused by an error in the protein structure of certain receptors?
- high blood pressue - asthma - heart disease - cancer
compare intercellular and intracellular signals
- intercellular signals are between two or more cells - intracellular signals are within the same cell
what are the two types of receptors?
- internal receptors - cell-surface receptors
3 categories of cell receptors
- ion chennel-inked - G-protein linked - enzyme-linked
metaphase
- mitotic spindle is fully developed - chromosomes lined up at the metaphase plate - each sister chromatid is attached to a spind fiber at the kinetochore from each pole
what major events occur in metaphase?
- mitotic spindle is fully developed, centrosomes are at opposite poles of the cell - chromosomes are lined up at the metaphase plate - each sister chromatid is attached to a spindle fiber originating from opposite poles
normally, proto-oncogenes stimulate the cell cycle. what are oncogenes and how do they affect the cell cycle?
- mutated proto-oncogenes - they increase stimulation with cell division
telophase
- nuclear envelope begins to form around DNA as it condenses - cytoplasm begins to pinch off - spindles disappear
mitotic spindle
- organizes the chromosomes and moves the around during mitosis - grows between chromosomes as they move apart
what are the four categories of chemical signaling found in multicellular organisms?
- paracine - endocrine - autocrine - direct signaling across gap junctions
there are four basic categories of chemical signaling found in multicellular organissms
- paracine signaling - autocrine signaling -endocrine signaling - signlaing by direct contact
water soluble ligands
- polar and therefore cannot pass through the plasma membrane unaided; sometimes, they are too large to pass through the membrane at all - most water-soluble ligands bind to the extracellular domain of cell-surface receptors
mitosis consists of four general phases
- prophase - metaphase - anaphase - telophase
what are the phases of karyokinesis (mitosis)?
- prophase - prometaphase - metaphase - anaphase - telophase
what are some examples of "cellular responses" that can result from a signaling pathway?
- protein synthesis - change in cell metabolism - cell division/growth - cell death
three stages of cell signlaing
- reception - transduction - response
there are three stages of cell signaling
- reception: the target cell's detection of a signal molecule coming from outside the cell - signal transduction: the conversion of the signal to a form that can cause a specific cellular response - response: the specific cellular response to the signal molecule
what are the two main types of cell signaling?
- signal molecules - direct contact
anaphase
- sister chromatids separate - cell elongates by spindle fibers
what internal and external conditions will the G1 checkpoint assess?
- size - nutrients - molecular signals - DNA integrity
what are examples of water-soluble ligands?
- small molecules - peptides -proteins
S Phase
- synthesizes a complete copy of DNA - duplicated the centrosome
how does the spindle checkpoint actually work?
- the cell looks for stray chromosomes - if one is misplaced, mitosis will be paused and will allow the spindle to find the chromosome
early prophase
- the mitotic spindle begins to form - DNA condenses - the nuclear envelope disappears
what is kinase and what does it do? how are kinases named?
- the transfer of the phosphate is catalyzed by an enzyme - for the substrate they phosphorylate
synaptic signaling
- transmitted signals of nerve cells - this process if named for the synapse, the junction between two nerve cells where signal transmission occurs
how do cells use signaling pathways and what do they allow cells to do?
- using signaling pathways, cells detect and respond to changes in the environment - allow organisms to coordinate cellular activities and metabolic pathways
3 stages of cell signaling
1. reception - ligand binds to receptor 2. signal transduction - the intercellular signal is converted into an intracellular signals 3. cellular response
human cells have ___ chromosomes, while human gametes have ___ chromosomes each
46, 23
negative feedback
A primary mechanism of homeostasis, whereby a change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation.
kinetochore
A specialized region on the centromere that links each sister chromatid to the mitotic spindle.
somatic cells
Any cells in the body other than reproductive cells
what are cyclin-dependent kinases and what is their role in the cell cycle?
Cdks are regulating proteins that must be bound to cyclins to be activated
___ are always present in the cell but become active only when they are bound to other proteins called ___, whose concentration inside the cell fluctuates depending on the phase of the cycle
Cdks; cyclins
G1
Cellular contents, excluding the chromosomes, are duplicated
direct contact signaling
Direct signaling can occur by transferring signaling molecules across gap junctions or plasmodesmata between neighboring cells
positive feedback
Feedback that tends to magnify a process or increase its output.
___ are an example of a receptor protein in eukaryotes.
G protein-coupled receptors
A cell can enter a stage (___) where it no longer divides, but it can reenter the cell cycle in response to appropriate cues. Nondividing cells may exit the cell cycle or be held at a particular stage in the cell cycle.
G0
daughter cells may exit the G1 phase and enter a resting phase called ___
G0
if a cell doesn't get the "okay" from the G1 checkpoint, it may leave the cell cycle and enter ___
G0 phase
Rb, p53, and p21 act primary at the ___. p53 is a multi-functional protein that has a major impact on the commitment of a cell to ___ because it acts when there is damaged DNA in cells undergoing G1
G1 checkpoint
interphase phases
G1, S, G2
what are the three stages of interphase?
G1, S, G2
the GTP on the active alpha subunit of the G-protein is hydrolyzed to ___ and the beta-gamma subunit reassociates to form the inactive G-protein and the cycle beings a new
GDP
the alpha subunit of G-protein will exchange ___ for GTP, activating G-protein
GDP
when the G-protein is inactive, it will bind ___ to its alpha subunit
GDP
when the G-protein eventually becomes activated, it will bind ___ instead
GTP
___ cyclin promotes the events of M phase such as nuclear envelope breakdown and chromosome condensation
M
___ is a process that ensures the transfer of a complete genome from a parent cell to two genetically identical daughter cells
Mitosis
___ plays a role in growth, tissue repair, and asexual reproduction.
Mitosis
___ in any domain of the receptor protein or in any component of the signaling pathway may affect the downstream components by altering the subsequent transduction of the signal.
Mutations
metaphase plate
Plane midway between the two poles of the cell where chromosomes line up during metaphase.
when does DNA replicate?
S phase of interphase
paracrine signaling
Signal released from a cell has an effect on neighboring cells.
___ relay signals from receptors to cell targets, often amplifying the incoming signals, resulting in the appropriate responses by the cell, which could include cell growth, secretion of molecules, or gene expression
Signaling cascades
endocrine signaling
Specialized cells release hormone molecules into vessels of the circulatory system, by which they travel to target cells in other parts of the body.
what type of eukaryotic cells are considered a diplod?
a body cell that contains two matched sets of chormosomes
autocrine signaling
a cell signals to itself, releasing a ligand that binds to receptors on its own surface
genome
a cell's DNA, packaged as a double-stranded DNA molecule
dimer
a chemical compound formed when two molecules join together
synaptic signal
a chemical signal that travels between nerve cells
the anaphase-promoting complex/cyclosome
a complex that causes M cyclins to be destroyed starting in anaphase
positive feedback mechanism
a feedback that increases stimli
negative feedback mechanism
a feedback that reduces stimuli
Signaling begins with the recognition of a chemical messenger—___—by a receptor protein in a target cell
a ligand
what is a tumor?
a mass of cells
ligands
a molecule that binds another specific molecule, delivering a signal in the process
inhibitor
a molecule that binds to a protein and prevents it from functioning or reduces its function
what occurs when the ligand binds to the G-protein-coupled receptor>
a phosphate is added to GDP attached to the alpha unit, separating the three subunits to go off and promote cellular response
what occurs during the signal transduction stage?
a series of relay proteins inside the cytoplasm of the target cell activate target proteins, resulting in a cellular response
how does signaling by direct contact work?
a signaling cell is connected to the target cell and sends ligands trough the membranes
how does autocrine signaling work?
a signaling cell sends a lignad to itself
cyclic AMP
a small, second messenger molecule made from ATP
how do the levels of cyclins fluctuate during the cell cycle?
a specific type of cyclin increases by the phase the cell cycle is in
checkpoint
a stage in the eukaryotic cell cycle at which the cell examines internal and external cues and "decides" whether or not to move forward with division
what needs to occur in order to get a cellular response?
a stimulus by a cell signal
synaptic signaling
a type of local signaling specific to neurotransmitters in nerve cells
why is it important that cells have a wide range of receptor types?
a wide variety of receptor types allows the cell to respond to a variety of stimuli; allows the cell to carry out as many reactions/processes as possible
small molecules, such as calcium ions, are ___, but large molecules like proteins and DNA ___
able to move between cells; cannot fit though the channels without special assistance
cyclin-dependent kinases
activate when bound to cyclins
Chemicals that interfere with any component of the signaling pathway may ___ or ___ the pathway.
activate; inhibit
like all kinases, Cdks are enzymes that phophorylate other proteins. phosphorylation actives the proteins by changing its shape. the proteins phophorylated by Ckds are involved in ___
advancing the cell to the next phase
when will a cell enter G0 phase?
after a cell divides and doesn't need to again immediently
postive feedback
amplifies the action in the body
G protein-coupled receptors
an embedded protein with three sub-units that detach to form a response
what occurs in signal transduction?
an extracellular signal is converted into an intracellular signal
cell cycle
an ordered series of events involving cell growth and cell division that produced two new daughter cells
what happens if cell cycle regulators don't function properly?
an organism can have too many or not enough cells; hair loss, warts, turmors
gap junctions can be found between the plasma membranes of neighboring ___ cells
animal
gap junctions
animal cells connected to each other
When does the G1 checkpoint occur?
at the end of G1 phase before S phase
when does the G2 checkpoint occur?
at the end of G2 phase before mitosis
how long does it take for the cell cycle to take?
average 24 hours, but cell that need to constantly divide can take up to 10
nucleosome
beadlike histone DNA complex
what does signal transduction only occur with cell-surface receptors and not internal receptors?
because internal receptors are able to interact with DNA directly
what are cell-surface receptors also called cell specific proteins or markers?
because they are specific to individual cell type
inter-
between
ion channel linked receptors
bind a ligand and open a channel through the membrane that allows specific ions to pass through
ion channel-linked receptors
bind a ligand and open a channel through the membrane that allows specific ions to pass through
what do the ligand molecules do once inside the cell?
bind to proteins that act as regulators of mRNA synthesis to mediate gene expression
before the ligand binds to the GPCR on the outer surface of the cell, the inactive G-protein is ___ specific for its binding
bound to an internal site on the receptor
what type of cells stay in G0 phase?
brain, small intestine, stomach
how do cells communicate with each other?
by sending signaling molecules or by direct contact
how do cell signaling pathways start?
by the ligand binding to a receptor
cell signaling ___ happen over both short and long distances
can
inositol phosphates
can be phosphorylation and snipped in half, releasing two fragments that both act as second messengers
small hydrophobic ligands
can directly diffuse through the plasma membrane and interact with internal receptors
errors in the regulation of the cell cycle can cause ___, which is characterized by ___ cell division
cancer; uncontrolled
water soluble ligands
cannot pass through membrane without aid; bind to extracellular domain of cell surface receptors
factors that contribute to causing cancer are termed ___
carcinogens
___ are proteins that control the progression of a cell through the cell cycle and can either stimulate or inhibit cell cycle progression
cell cycle regulators
core ___ can cause key events, such as: DNA replication, chromosome separation, and makes sure the cell cycle events take place in the right order
cell cycle regulators
Interactions between cyclins and cyclin-dependent kinases control the ___
cell cycle.
predict what would happen to the cell cycle if there was a mutation in the p53 gene
cell division would be unregulated, sharing the mutations with more cells causing cancer
G1 Phase
cell grows larger, copies organells, and makes molecular building blocks
G2 Phase
cell grows more, makes proteins and organelles, and begins to reorganize its contents in preparation for mitosis
plant cells divide in two by building a new structure down the middle of the cell. this structure, known as the ___, is made up of plasma membrane and cell wall components delivered in vesicles, and it partions the cell in two
cell plate
intracellular receptors
cell receptors located in the cytoplasm of the cell
cell-surface receptors
cell receptors located in the plasma membrane
___ makes sure that cells don't divide under unfavorable conditions
cell regulation
what occurs at G2 checkpoint?
cell size and protein reserves are assessed
cell surface receptors
cell surface, integral proteins that bind to external ligand molecules
when a lignad binds to a ___, the receptors intracellular domain changes in some way (new shape)
cell-surface receptor
what are enzyme-linked receptors?
cell-surface receptors with intracelllar domains that are associated with an enzyme
Receptor Tyrosine Kinases (RTKs)
cell-surface receptors with intracellular domains that are associated with am enzyme
receptor tyrosine kinases
cell-surface receptors with intracellular domains that are associated with an enzyme
why does cell division remain important to adult organisms even after it is fully developed?
cells need to be continuously renewed/cells need to divide to heal wounds
Cells divide, differentiate, or die. What is differentiation?
cells stop dividing to specialize in structure and function
target cells
cells that are affected by chamical signals
what type of cells spend more of their time/all their time in G0 phase?
cells that rarely/never divide such as muscle and nerve cells
Changes in signal transduction pathways can alter ___
cellular response
one or both of G-protein fragments may be able to regulate activity of other target proteins as a result. this is the ___
cellular response
response
cellular response
internal and external cues act by ___ the activity of core cell cycle regulators inside the cell
changing
ligand-gated ion channels
channels embedded in the membrane, controlled by ligands
A number of internal controls or ___ regulate progression through the cycle.
checkpoints
cells that are near one another communicate through the release of ___ (ligands that can diffuse through the space between cells)
chemical messengers
the message carried by a ligand is often relayed through a chain of ___ inside the cell. untimely, t leads to a change in the cell, thus the original ___ signal is converted into an extracellular signal within the cell that is a signal that triggers a response
chemical messengers; intercellular
Cells communicate with one another through direct contact with other cells or from a distance via ___
chemical signaling
cells communicate by generating, transmitting, receiving, and responding to ___
chemical signals
cells typically communicate using ___
chemical signals
signaling cells
chemical signals in the form of small, usually soluble molecules called ligands
cells signal one another with ___
chemicals
after replication, the chromosomes are composed of two linked ___
chromatids
anaphase
chromatids are separated and begin to get pulled to the opposite ends of the cells by spindle fibers
in mitosis, motor proteins carry ___ or ___ as they walk
chromosomes; microtubules
when a ligand binds to the extracellular region of the channel, there is a ___ in the proteins structure that allows ions such as sodium, calcium, magnesium, and hydrogen to pass through
conformational change
cdk levels remain relatively ___ across the cell cycle
constant
cells will continue to grow until they come into ___
contact with other cells
signal transduction
continuation of a signal that was transmitted through the cell membrane
in animals, cell division occurs when a band of cytoskeletal fibers called the ___ contracts inward and pinches the cell in two, a process called contractile cytokinesis
contractile ring
signal transduction
conversion of signal
cyclins drive the events of the cell cycle by partnering with a family of enzymes called the ___
cyclin-dependent kinases
the most important cell cycle regulators are the ___
cyclin-dependent kinases
___ are among the most important core cell cycle regulators
cyclins
___ regulate the timing of the cell cycle in eukaryotic cells
cyclins
what are cyclins and what is their role in the cell cycle?
cyclins are cell cycle regulating proteins
what is the relationship between cyclins and Ckds?
cyclins regulate the cell cycle only while they are tightly bound to Ckds
two groups of proteins, called ___ and ___, are responsible for the progress of the cell through the various checkpoints
cyclins; cyclin-dependent kinases
in ___, the cytoplasm of the cell is split in two, making two new cells
cytokinesis
what occurs at G1 checkpoint?
determines whether all conditions are favorable for cell division to proceed
each endocrine gland releases one or more types of hormones, many of which are master regulators of ___ and physiology
development
paracrine signaling is especially important during ___, when they allow one group of cells to tell a neighboring group of cells what cellular identity to take on
development
because of their form of transport, hormones get ___ and are present in low concentrations when they act on their target cells
diluted
small hydrophobic ligands
directly diffuse through the plasma membrane and interact with internal receptors
what can occur if there is an error in signaling pathways?
disease
the alpha subunit will ___ from the beta and gamma subunits of the G-prtein complex and triggers a cellular response
dissociate
the main difference between the different categories of signaling is the ___ that the signal travels through the organism to reach the target cell
distance
signals from ___ cells are called endocrine signals, and they originate from endocrine cells
distant
at the G1 checkpoint, the cell decides whether or not to ___
divide
cytokinesis
division of the cytoplasm to form two separate daughter cells
mitosis
division of the nucleus
DNA synthesis checkpoint
during S'; checks DNA was replicated properly
describe what occurs during cytokinesis
during cytokineses, the two daughter cells begin to form by the cytoplasm pinching off till they separate. this can start to begin all the way to anaphase
when does the spindle checkpoint occur?
during mitosis (metaphase)
s
each chromosome is duplicated
how are receptors specific?
each ligand is recognized by a different receptor
cell growth checkpoint
end of G1; checks is cell is big enough to divide
Signal transduction pathways influence how the cell responds to its ___.
environment
paracine signals usually elicit quick responses that last only a short amount of time, in order to keep the response localized, paracrine ligand molecules are normally quickly degraded by ___ or removed by neighboring cells
enzymes
kinases
enzymes that add a phosphate to active/inhibit a proteins function
kinases
enzymes that phophorylate specific target proteins
the ligand binding domain is also called the ___
extracellular domain
what type of receptors do most water-soluble ligands bind with?
extracellular domain of cell-surface receptor
when a ligand binds to the ___ of the ion channel, there is a conformational change in the proteins structure that allows ions such as sodium, calcium, magnesium, and hydrogen to pass through
extracellular region
all G-protein-linked receptors have seven transmembrane domains, but each receptor has its down specific ___ and ___
extracelular domain; G-protein-binding site
Positive feedback mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved ___ from the initial set point. Amplification occurs when the stimulus is further activated, which, in turn, initiates an additional response that produces system change.
farther away
what are examples of small hydrohobic ligands?
female sex hormone, male sex hormone, cholesterol
why do cells divide via mitosis?
for growth, repair, replacement, and reproduction
integral receptors
found in the cytoplasm of the cell and respond to hydrophobic ligand molecules that are able to travel across the plasma membrane
intracellular receptors
found in the cytoplasm or nucelus of the cell
cyclins are a group of related proteins, and there are ___ basic types found in humans: G1 cyclins, G1/S cyclins, S cyclins, and M cyclins
four
___ bind a ligand and activate a membrane protein called a G-protein
g-protein-linked receptors
what types of eukaryotic cells are considered haploid?
gametes, which contains one set of chormosomes
___ in animals and ___ in plants are tiny channels that directly connect neighboring cells
gap junctions; plasmodesmata
Signal transduction may result in changes in ___ and ___, which may alter phenotype or result in programmed cell death (apoptosis).
gene expression; cell function
internal receptors can directly influence ___ without having to pass to signal on to other receptors or messengers
gene exprression
___ is a gene that codes for a protein that regulates the cell cycle and hence functions as a tumor suppression
gene p53
cells communicate by ___, ___, ___, and responding to chemical signals
generating; transmitting; receiving
what do homologous chromosomes contain?
genes
In eukaryotes, cells divide and transmit ___ via two highly regulated processes.
genetic information
malignant
grow uncontrollably and can migrate throughout the body in a process called metastasis
a checkpoint is one of several points in the eukaryotic cell cycle at which the progression of a cell to the next stage in the cycle can be ___ until conditions are ___
halted; favorable
what is normal functioning p53 responsible for?
halting the cell cycle if damaged DNA is present; enzymes will either repair DNA or signal cell death
centrosome
helps separate DNA during M phase
in humans, endocrine glands that release ___ include they thyroid, the hypothalamus, and the pituitary, as well as the gonads and the pancreas
hormones
signals that are produced in one part of the body and travel through the circulation to reach far-away targets are known as ___
hormones
what is the ligand called that is used in endocrine signaling?
hormones
each daughter cell has an ___ set of chromosomes
identical
what role does autocrine signaling play in viral infections of cells?
if a cell is infected with a virus, the cell can send an autocrine signal to kill itself, along with the virius
what does the spindle checkpoint check?
if all sister chromatids are correctly attached to the spindle microtubules
which factors determine whether a cell enters G0?
if the cell needs to be constantly dividing or not
cell-cell signaling is important in the ___ to help recognize "self" cells and infected cells
immune system
cancer results from an ___ regulated cell cycle. as a result, cells replicate indefinitely and form tumors
improperly
cell surface receptors
in plasma membrane
alone cdks are ___, but the binding of a cyclin ___ it
inactive; activates
negative feedback
inhibts orignial stimulus
when the lignad binds to the internal receptor, a conformational change is triggered that exposes a DNA-binding site on the protein. the ligand-receptor complex moves into the nucleus, then binds to specific regulatory regions of the chromosomal DNA and promotes the ___ of transcription
initation
intra-
inside
regulators of the cell cycle transitions respond to cues from ___ and ___ the cell
inside; outside
cell surface receptors
integral proteins that bind to external ligand molecules
___ and ___ cues trigger signaling pathways inside the cell that activate, or inactivate, a set of core proteins that move the cell cycle foward
interal; external
what is the communication between cells called?
intercellular signaling
Organisms use feedback mechanisms to maintain their ___ and respond to internal and external environmental changes.
internal environments
cyclins & CDKs
internal molecular signals that regulate cell transitions through various checkpoints
what type of receptors do small hydrophobic ligands interact with? how is this possible?
internal receptors because these types of molecules are able to pass through the membrane
to regulate the cell cycle, cells use information about their own ___ state and cues from the ___ around them
internal; environment
Mitosis alternates with ___ in the cell cycle.
interphase
during ___, the cell grows and makes a copy of its DNA
interphase
what are the two main phases of the cell cycle?
interphase - the cell grows and DNA is replicated mitotic phase - the cell divides
The cell cycle consists of sequential stages of ___ (G1, S, G2), ___, and ___.
interphase; mitosis; cytokinesis
in eukaryotic cells, or cells with a nucleus, the stages of the cell cycle are divided into two major phases: ___ and the ___
interphase; mitotic (M) phase
in eukaryotic cells the stages of the cell cycle are divided into two major phases: ___ and the ___
interphase; mitotic phase
the G1, S, and G2 phases together are known as ___. the prefix of inter- means between, reflecting that interphase takes place between one ___ and the next
interphase; mitotic phase
these cell connectors, water-filled channels allow small signaling molecules, called ___, to diffuse between the two cells
intracellular mediators
receptors come in many types, but they can be divided into two categories: ___ and ___
intracellular receptors; cell surface receptors
the chains of molecules that relay signals inside a cell are known as ___
intracellular signal transduction pathways
what is the communication within a cell called?
intracellular signaling
the activated G-protein then interacts with either an ___ or an ___ in the membrane
ion channel; enzyme
ligand-gated ion chaannels
ion channels that can open in response to the binding of a ligand
because the separation of the sister chromatids during anaphase is an ___ step
irreversible
what happens to the daughter cell of a parental cell that has a mutated p53 gene?
it accumulates oncogenes and faulty tumor suppressors, leading to a tumor growth
what occurs when a ligand binds the G-protein-inked receptors?
it activates a membrane protein called G-protein
what is it important that cells have a wide range of receptor types?
it allows the cell to respond to a variety of stimuli
when a signal binds to the receptor ___
it alters the shape
when a signal binds to the receptor ___
it alters the shape of it, triggering change in the cell
when a signaling molecule binds to its receptor, ___, triggering a change inside of the cell
it alters the shape or activity of the receptor
what occurs at the M checkpoint?
it determines whether all the sister chromatids are correctly attached to the spindle microtubules
what occurs when a ligand binds to an ion channel linked receptor?
it opens a channel through the membrane that allows specific ions to pass through
normally, tumor suppressor genes inhibit the cell cycle. how do mutated tumor suppressor genes affect the cell cycle?
it stops the regulation of cell division
a ___ of HGH can inhibit cell division, resulting in dwarfism, whereas ___ HGH can result in giganticism
lack; too much
G-protein-coupled receptors
large family of cell surface receptors that share a common structure and method of signaling
what type of ligand molecules will interact with cell surface receptors?
large hydrophilic
when does cytokinesis start in animal cells that lack a cell wall?
late into anaphase
signaling molecules are often called ___, a general term for molecules that bind specifically to other molecules (such as receptors)
ligands
Cells communicate over short distances by using ___ that target cells in the vicinity of the signal-emitting cell
local regulators
when cells need to transmit signals over ___, they often use the circulatory system as a distribution network for the messages they send
long distances
___ was discovered to be a cdk bound to its M cyclin partner
maturation-promoting factor
cell-surface receptors
membrane-anchored proteins that bind to ligands on the outside surface of the cell
before proceeding at anaphase, the cell will check to make sure that all the chromosomes are at the ___ with their kinetochore correctly attached to microtubules
metaphase plate
mitosis checkpoint
metaphase; checks chromosomes
why is it essential that daughter cells be exact duplicates of the parent cell?
mistakes in duplication of chromosomes can lead to mutations that will be passed to every new cell that is produced
cells go through periods of growth and division. cell division occurs during ___
mitosis
cytokinesis usually begins just as ___ is ending, with a little overlap
mitosis
during the ___, the cell separates its DNA into two sets and divides its cytoplasm, forming two new cells
mitotic (M) phase
during the ___, the cell separates its DNA into two sets and divides its cytoplasm, forming two new cells
mitotic phase
what are cell cycle regulator?
molecular signals that may stimulate or halt cell division, instruct to differentiate, or initiate cell death
regulator molecules
molecules that either promote progress of the cell cycle or halt it
Cdk inhibitors
molecules that prevent the full activation of cdks
second messengers
molecules that relay and amplify the intracellular signal
all of these processes are driven by ___, molecular machines that can "walk" along microtuble tracks and carry a cargo.
motor proteins
metastasis
movement of cancer from one body part to another
oncogenes
mutated proto-oncogenes
cancer is generally the result of a ___ in a cell that "turns off" its response to internal and external call regulators
mutation
by ensuring that cells don't divide when their DNA is damaged, p53 prevents ___ from being passed on to daughter cells
mutations
changes in signal transduction pathways can alter cellular response - ___ in any domain of the receptor protein or in any component of the signaling pathway may affect the downstream components by altering the subsequent transduction of the signal
mutations
when does M checkpoint occur?
near the end of the metaphase stage
___ feedback reverses changes in a system, while ___ feedback amplifies changes in a system
negative; positive
cells can detect whats going on around them, and they can respond in real time to cues from their ___ and ___
neighbors; environment
in plants, plasmodesmata are ubiquitous, making the entire plant into a grant communication ___. pretty cool
network
then the impulse reaches the synapse, it triggers the release of ligands called ___, which quickly cross the small gap between the nerve cells
neurotransmitters
what are the ligands called that are involved in nerve signaling?
neurotransmitters
dissolved gasses like ___ can be used as signals
nitric oxide
is cytokinesis the same for both plant and animal cells?
no, because in plant cells a cell plate is made to form a cell wall while animal cells have a cleavage furrow as they separate
in order for cells to communicate with each other, do they always need to be next door neighbors?
no, signals can travel long distance through the blood stream
the level of Cdks remains stable throughout the cell cycle. is this true for cyclins?
no, the concentrations of cyclin fluctuate and determined when Cdks/cyclin complexes form
what type of molecules can diffuse across the membrane to bind to internal receptors?
non-polar molecles
second messenegers
non-protein molecules that pass along a signal initiated by the binding of a lignad to its receptor
contact inhibition
normal cells will reproduce until they come into contact with other cells
each copy of a homologous pair of chromosomes originates from a different parent, therefore, the genes themselves are ___ always identical
not
what are cells doing during G0 phase?
nothing, the cell exits the cycle
karyokinesis
nuclear division
after DNA wrap around the eight histones, ___ will then begin to coil together themselves until they are tightly compacted into a chromosome
nucleosome
what are the levels of cyclin present in a cell dependent on?
on the phase of the cell cycle
where can a receptor be found?
on/in a target cell
mutated versions of proto-oncogeses, called ___ are analogous to putting the foot on the accelerator, increasing stimulation
oncogenes
chromatids
one-half of a chromosome; each chromatid carries identical information, capable of replicating to form a new chromosome
Binding of ligand-to-ligand-gated channels can cause the channel to ___ or ___
open; close
many cancer cells have been found to have a defect in gene ___, tumor suppressor gene
p53
explain the importance of p53
p53 can stop any mutations
describe the role of the p53 protein on the cell cycle?
p53 detects damaged DNA and calls for correction or apoptosis
homologous chromosomes
pairs of chromosomes in a diploid organism
examples of water soluble ligands
peptides, proteins
chemicals used to signal to cells can include ___, ___, ___, ___, ___, and ___
peptides; proteins; amino acids; nucleotides; steroids; other lipids
one of the most common chemical modifications that occurs in signaling pathways is the addition of a ___ to a molecule such as a protein in a process is called phophorylation
phosphate group
kinases are enzymes that add a ___ to other proteins to activate or inhibit their function - a process called ___
phosphate; phosphorylation
what is the function of phosphorylation in cell signaling pathways?
phosphorlyation changes the shape of proteins
a kinase is an enzyme that transfers phosphate groups from ATP to other protein (___)
phosphorylyation
plasmodesmata can be found between the plasma membranes of neighboring ___ cells
plant
plasmodesmata
plant cells connected to each other
in plants, there are ___ between almost all cells, making the entire plant into one giant network
plasmodesmata
what types of molecules bind to receptors embedded in the cell membrane?
polar ligands
receptor proteins form a ___, which is opened a closed by ___
pore; chemical signals
inside the cell, proteins often help control cell growth whereas hormones often ___
preform this action from outside the cell
autocrine signals
produced by signaling cells that can also bind to the ligand that is released
apoptosis
programmed cell death
What is apoptosis? what is its purpose?
programmed cell death; get rid of unnecessary or damaged cells
these internal and external cues determine whether the cell ___ in the cell cycle or not
progresses
what types of organisms divide using binary fission?
prokaryotes
mitosis phases
prophase, metaphase, anaphase, telophase, cytokinesis
Mitosis occurs in a sequential series of steps (___, ___, ___, ___).
prophase; metaphase; anaphase; telophase
Many signal transduction pathways include ___ modification and phosphorylation cascades.
protein
the ___ of the kinetochore attacks and bind mitotic spindle microtubles
protein
what occurs during G2 phase?
proteins check for any damaged DNA
what occurs during the spindle checkpoint?
proteins check that all cromatids are attached to spindle fibers
what occurs during G1 checkpoint?
proteins check to make sure the cell can go through cell division
receptors
proteins on target cells
ligands come in many different varieties. some are ___, others are ___ and others yet are ___
proteins; hydrophobic molecules; gases
these chemical signals, which are ___ or other molecules produced by a sending cell, are often ___ from the cell and released into the___. there, they can float over to neighboring cells
proteins; secreted; extracellular space
proteins that normally stimulate the cell cycle are encoded by ___
proto-oncogenes
stimulating proteins are encoded by ___
proto-oncogenes
genes that encodes cell cycle regulators are referred to as ___ and ___, respectively, and mutations in these genes can lead to cancer
proto-oncogenes; tumor suppressors
Signal transduction pathways link signal ___ with cellular responses.
reception
three stages of cell signaling
reception, transduction, response
a specific ligand will have a specific ___ that typically binds only that ligand
receptor
in order to get a signal a target cell must have the correct ___
receptor
in order to get a signal, a target cell must have the correct ___
receptor
intracellular receptors
receptor proteins found on the inside of the cell, typically in the cytoplasm or nucleous
with internal receptors, the ___ moves to the nucleus and interacts with cellular DNA. this changes how a gene is expressed
receptor-ligand complex
cyclins
regulate the timing of the cell cycle
Second messengers (such as cyclic AMP) are molecules that ___ and ___ the intracellular signal.
relay; amplify
quorum sensing
release of signal molecules that allows bacteria to respond to changes in the environment; single-celled organisms communicated with one another
if errors are detected by the G2 checkpoint, the cycle will pause to allow ___
repairs
The cell cycle is a highly regulated series of events for the growth and ___ of cells
reproduction
internal receptors
respond to hydrophobic ligand molecules that are able to travel across the membrane
tumor suppressor genes
segments of DNA that code for negative regulator proteins that can prevent the cell from undergoing uncontrolled cell division
all G-protein-linked receptors have ___ transmembrane domains, but each receptor has its own specific extracellular domain and G-protein-binding site
seven
After the ligand binds, the intracellular domain of a receptor protein changes ___ initiating transduction of the signal.
shape
when the proteins bind to one another, this interaction changes the ___ of one or both proteins, transmitting a signal
shape
cells communicate over relatively ___ distances
short
how is DNA organized in the first level of compaction?
short stretches of the DNA double helx wrap around a core of eight histone proteins at regular intervals along the entire length of the chromosomes, and DNA connecting the nucleosomes is called linker DNA
cell signaling pathways vary a lot. signals and receptors come in many varieties, and binding can trigger a wide range of ___ inside the cell, from short and simple to long and complex
signal relay cascades
once the signaling molecule and receptor interact, a cascade of events called ___ usually amplifies the signal inside the cell
signal transduction
the GPCR-pecific ligand will bind to the GPCR on the outer surface of the cell, causing a conformational shape change to the GPCR. this binding triggers a complex chain of events (___)
signal transduction
where can a ligand be found?
signaling cell, extracellular fluid, target cell/receptor
___ secrete molecules called ___ that bind to target cells and initiate a chain of events within the ___
signaling cells; ligands; target cell
ligand
signaling molecule
ligands
signaling molecules
the transfer of ___ transmits the current state of one cell to its neighbor. this allows a group of cells to coordinate their ___ to a signal that only one of them may have received
signaling molecules; response
paracine signaling
signals that act locally between cells that are close together
binary fission
simplified cell division in prokaryotic cells
the change in the receptor sets off a series of ___
singaling events
endocrine signals usually produce a ___ response, but have a longer-lasting effect
slower
what type of ligand molecules will interact with internal receptors?
small hydrophobic
second messengers
small molecules that propagate a signal after it has been initiated by the signaling molecule to the receptor
what type of molecules are allowed to pass through gap junctions and plasmodesmata, diffusing between cells?
small signaling molecules
ligands that can enter the cell
small, hydrophobic ligands can pass through the plasma membrane and bind to intracellular receptors in the nucleus or cytoplasm
cells reproduce in order to maintain a ___ size and a smaller surface area to volume ratio
smaller
DNA plasmid
smaller loops of DNA in some prokayotes that are non essential for normal growth
cells reproduce to maintain a ___ size and a ___ surface area to volume ratio
smaller; smaller
what types of cells undergo mitosis?
somatic cells
what happens to the two daughter cells produced in one round of the cell cycle?
some daughter cells may immediately undergo another round, it depends on the type of cell, or it can rest
in long-distance endocrine signaling, signals are produced by ___ and released into the ___, which carrier them to target cells in distant part of the body
specialized cells; blood-stream
The ligand-binding domain of a receptor recognizes a ___, which can be a peptide, a small chemical, or protein, in a specific one-to-one relationship.
specific chemical messenger
prometaphase
spindle fibers attach to the kinechores of the chromosomes
cancer cells may break loose from tumors and ___, disrupting normal activities and causing serious medical problems
spread throughout the body
examples of small hydrophobic ligands
steroid hormones, sex hormones, cholesterol, thyroid hormone, vitamin D
some proteins activate CDK-cyclin complexes, ___ the cell cycle. others inactivate CDK-cyclins or prevent their activation, which ___ cell cycle progression
stimulating; inhibts
receptor
structure that binds to a lignad to trigger a response in the target cell
some signaling molecules are attached to the ___ of the signaling cells
surface
two cells many bind to one another because they carry complementary proteins on their ___
surfaces
example of paracrine signaling
synaptic signaling
not all cells can "hear" a particular chemical message. in order to detect a signal (the ___), a neighboring cell must have the right ___ for that signal
target cell; receptor
Negative feedback mechanisms maintain homeostasis for a particular condition by regulating physiological processes. If a system is perturbed, negative feedback mechanisms return the system back to its ___. These processes operate at the molecular and cellular levels.
target set point
some cells enter G0 ___ until an ___ triggers the onset of G1
temporarily; external signal
what is the G0 phase of the cell cycle?
the "resting" phase
What is a clevage furrow?
the actin filaments pull the equator of the cell inward to form a fissure
phosphorylation
the addition of a phosphate group to one or more sites on the protein
phophorylation
the addition of a phosphate group to one or more sites on the protein which then activates the protein
what is the difference between the amino acids that make up the membrane-spanning region and the amino acids that line the inside of the channel?
the amino acids in the membrane spanning region are hydrophobic while the amino acids that line the inside of channel are hydrophilic
how do ligands allow for the movement of ions through a ligand gated ion channel?
the binding of the ligand triggers the channel to open, allowing ions to pass through
what happens to a cell if it does not pass the G1 checkpoint requirements?
the cell can halt and attempt to fix the problem or go into G0 and await further signal
G2
the cell continues to grow an prepare for division
S phase
the cell copies its DNA
what happens to a cell if it does not pass the G2 checkpoint requirements?
the cell cycle will be halted, then attempt to solve it
G2 phase
the cell grows and prepares to divide
G1
the cell increases in size and prepares to replicate its DNA
what occurs during G1 phase?
the cell is accumulating the building blocks of chromosomal DNA and the associated proteins as well as accumulating sufficient energy reserves too replicate the chromosomes in the nucleus
G1 phase
the cell is growing and preparing to copy DNA
passage through G1 checkpoint makes sure that ___ in the S stage of interphase; passage through G2 checkpoint ___
the cell is ready for DNA replication; triggers the separation of chromatids during mitosis
G2
the cell prepares to divide
what occurs during G2 phase?
the cell replenishes its energy stores and synthesizes proteins needed for chromosome manipluation
S
the cell replicates its DNA
what occurs during interphase?
the cell undergoes normal growth processes while also preparing for cell divison
describe the outcome to the cell when apoptosis occurs and explain why this process is necessary
the cell will program its death if not the cell can divide with a mutation, passing it along
centromere
the central point of a chromosome where chromatids attach
signaling pathway
the chain of events caused by the activation of the receptor's interacellular components
centromere
the connection between the sister chromatids is closeted in a region
what happens to a cell if it does not pass the M checkpoints requirements?
the cycle will not proceed until all the kinetochores are attached
where are internal receptors found?
the cytoplasm
what is unique about the daughter cells of unicellular divison?
the daughter cells are not identical to the parent cell
reception
the detection of the signal
what is the man difference between the four types of chemical signals?
the distance the signal travels
the division of the cytoplam, to form two new cells, overlaps with ___
the final stages of mitosis
what occurs during S phase?
the formation of identical pairs of DNA molecules that are firmly attached to the centimeter region
proto-ocogenes
the genes that code for the positive cell cycle regulators
describe the genome of a prokaryote?
the genome is composed of a single, double stranded DNA molecule in the form of a loop or circle
clevage furrow
the indention in the cell when cytokinesisi is happening
what are growth factors?
the lignads that promote cell growth
what occurs when there is a p53 mutation?
the mutated p53 protein will fail to stop cell division if DNA is damaged
describe what amplification is and explain its importance
the number of signaling molecules that are produced or activated increases with each step of the pathway as several enzymes area activated. this results in the response being carried out multiple times instead of once
cytokinesis
the physical separation of the cytoplasmic components into the two daughter cells
if a chromosome is not properly aligned or attached, the cell will halt division until ___
the problem is fixed
cytokinesis
the second main stage of the mitotic phase, during which cell division is completed via the physical separation of the cytoplasmic components into the daughter cells
what is unique about the signaling and target cells in autocrine signaling?
the signaling cell and the target cell are the same/similar cells
how does paracrine signaling work?
the signaling cell sends a lignad to a close by cell
how does endocrine signaling work?
the signaling cell sends lignads to distant cells using the bloodstream
what occurs once the ligand binds to its specific receptor?
the transduction stage will begin
what does it mean that cyclins and Ckds are positive regulators?
they allow the cell to move to the next stage
why can't watersoluble ligands bind with internal receptors?
they are polar, so they cannot pass through the membrane
what happens to the tyrosine molecules once the ligand binds to the receptor?
they bind together to add a phosphate group to tyrosine
what do negative regulators do to the cell cycle?
they halt the cell cycle?
what are negative regulator molecules and what is an example?
they monitor cellular conditions and can pause the cycle; tumor suppressors
what happens to the two daughter cells produced in one round of the cell cycle?
they will either enter G0 phase or start the cell division process
g-proteins are specialized proteins made up of ___, which have the ability to bind with GTP and GDP
three subunits
where can you find endocrine cells in the human body?
thyroid gland, hypothalamus, and pituitary gland
why is cell communication important?
to know whats going on around the and respond to their environemtns
in general, what is the purpose of a checkpoint in the cell cycle?
to make sure there are no errors that would lead to a mutation
despite differences, signaling pathways share a common goal:
to produce some kind of cellular response
cancer is the result of an improperly regulated cell cycle. describe two reasons why cells can form tumors
too much or too little cell division
what is an examples of paracine signaling?
transfer of signals across synapses between nerve cells
cell-cell signaling involves the ___ of a signal from a signaling cell to a receiving/target cell. however, not all sending and receiving cells are next-door neighbors, nor do all cell pairs exchange signals in the same way
transmission
what promotes an increase in the concentration of cyclin proteins?
triggered by external and internal signals
___ produce proteins that normally inhibit the cell cycle
tumor suppressor genes
inhibitory proteins are encoded by ___
tumor suppressor genes
cancer cells divide uncontrollably and form masses of cells called __ that can damage the surrounding tissues
tumors
for the cell to move past each of the checkpoints, all positive regulators must be "___", and all negative regulators must be "___"
turned on; turned off
dimerization
two receptors bind to each other to form a stable complex called a dimer
most growth factors bind to cell-surface receptors that are linked to ___. these cell surface receptors are called receptor tyrosine kinases
tyrosine kinase
the ___ transfers phosphate groups to tyrosine molecules
tyrosine kinase receptor
what causes cancer?
unchecked cell division caused by a breakdown of the mechanisms that regulate the cell cycle
benign
usually not deadly, grow within a controlled area and removed surgically
what needs to occur for a plant cell to divide?
vesicles from the golgi are fused from the center toward the cell walls, this structure is a cell plate. then enzymes use glucose to build a new cell wall
hormones are the signaling molecules in endocrine signaling that are produced in one part of the body but affect other body regions some distance away. how do these hormones travel the large distances between endocrine cells?
via the bloodstream
why does cancer occur?
when regulators are mutated and no longer properly control cell divison
when does G0 phase occur?
when the cell has completed division
CDKs are always present in the cell. when do they become active?
when they are bound to cyclins
calcium ions
widely used type of second messenger
Can cells leave G0?
yes
are receptors found on target cells ligand specific?
yes, because ligands can only bind to certain receptors?
