AP biology unit 4 test
How is this "signal" passed from outside to inside the cell?
through transduction. During transduction the signal is relayed by protein kinases and amplified by second messengers
endocrine signaling
Specialized cells release hormones into the circulatory system where they reach target cells
Explain how sun damage can potentially lead to skin cancer.
Sunlight is UV radiation, which can cause mutations in skin cells. If the skin cells accumulate 60 or more mutations, they risk becoming cancerous.
local regulators
a secreting cell will release chemical messages (local regulators/ligands) that travel a short distance through the extracellular fluid ○ The chemical messages will cause a response in a target cell
stimulus
a variable that will cause a response
List the three types of external cell regulators.
growth factors, contact inhibition, and anchorage dependence.
What does DNA associate and wrap around with?
histones
what do plants use for long-distance signaling?
hormones
growth factors
hormones released by cells that stimulate cell growth
What can signal transduction pathways influence?
how the cell responds to its environment - They can result in changes in gene expression and cell function ■ Can alter phenotypes or result in cell death
What does cellular interaction with other molecules initiate?
transduction signal
True or false: all cells in the body must have ways to maintain homeostasis.
true
True or false: slight fluctua7ons in set points is normal.
true
What can uncontrollable growth of cancer cells lead to?
tumor
homologous chromosome
two chromosomes (one from mom and one from dad) that are the same length, have the same centromere position, and carry genes controlling the same characteristics
set points
values for various physiological conditions that the body tries to maintain
How do hormones released by plants travel?
vascular tissue or though the air to reach target tissues
Cytokinesis in plants
vesicles produced by the Golgi travel to the middle of the cell and form a cell plate
metastasis
when cells separate from the tumor and spread elsewhere in the body
disease
when the body is unable to maintain homeostasis
Does cyclin concentration change during the cell cycle?
yes
is ligand an receptor binding specific? What to they resemble
yes, a key and a lock
somatic cells (list of characteristics)
● Body cells ● Diploid (2n): two sets of chromosomes, one set from each parent ● Divide by mitosis ● Humans: 2n=46 ○ 23 from each parent
metaphase
● Centrosomes are at opposite poles ● Chromosomes line up at the metaphase plate ● Microtubules are attached to each kinetochore
G2 (second gap phase)
● Checks for completion of DNA replication and DNA damage ● "Go"--cell proceeds to mitosis ● "Stop"-- cell cycle stops and the cell will attempt to repair damage ○ If damage cannot be repaired the cell will undergo apoptosis ■ Programmed cell death
prophase
● Chromatin condenses ● Nucleoli disappear ● Duplicated chromosomes appear as sister chromatids ● Mitotic spindle begins to form ● Centrosomes move away from each other
cancer cells
● Do not follow checkpoints ● Divide infinitely when in culture ○ Considered to be "immortal" ● Evade apoptosis and continue dividing even with errors
normal cells
● Follow checkpoints ● Divide on average 20-50 times in culture (in petri dishes) ● Go through apoptosis when there are significant errors
G protein coupled receptors (GPCRs)
● Largest category of cell surface receptors ● Important in animal sensory systems ● Binds to a G protein that can bind to GTP, which is an energy molecule similar to ATP
ligand-gated ion channel
● Located in the plasma membrane ● Important in the nervous system ● Receptors that act as a "gate" for ions ○ When a ligand binds to the receptor, the "gate" opens or closes allowing the diffusion of specific ions ■ Initiates a series of events that lead to a cellular response
M phase
● Mitosis: nucleus divides ● Cytokinesis: cytoplasm divides ● Mitosis results in 2 identical diploid daughter cells ● Checks for microtubule attachment to chromosomes at the kinetochores at metaphase ● "Go"--cell proceeds to anaphase and completes mitosis ● "Stop"-- cell will pause mitosis to allow for spindles to finish attaching to chromosomes
G1 (first gap phase)
● Most important checkpoint ● Checks for cell size, growth factors, and DNA damage ● Stop/Go signals ○ "Go"- cell completes the whole cell cycle ○ "Stop"- cell enters a nondividing (quiescent) state known as G0 phase
Prometaphase
● Nuclear envelope fragments ● Microtubules enter nuclear area and some attach to kinetochores
Gametes
● Reproductive cells (eggs/sperm) ● Haploid (n): one set of chromosomes ● Divide by meiosis ● Humans: n=23
Anaphase
● Sister chromatids separate and move to opposite ends of the cell due to the microtubules shortening ● Cell elongates
G0
● Some cells stay in G0 forever (muscle/nerve cells) ● Some cells can be called back into the cell cycle
Telophase and Cytokinesis
● Two daughter nuclei form ● Nucleoli reappear ● Chromosomes become less condensed
examples of responses
- Protein that can alter membrane permeability - Enzyme that will change a metabolic process - Protein that turns genes on or off
Summarize the three stages of cell signaling in one sentence each.
- Reception occurs when a receptor in the target cell receives the ligand. Transduction is the conversion of an extracellular signal to an intracellular signal - signal transduction pathway that is amplified and relayed by second messengers. - Response occurs when the signal pathway converts the signal to a response that will alter a cellular process, most commonly turning genes on and off.
example of intracellular receptors
- Steroid and thyroid hormones - Gasses like nitric oxide
How many feedback loops and what are they?
2, positive and negative
If a sperm cell contains 12 chromosomes, it comes from an animal that has ______ chromosomes.
24
How can chemicals activate or inhibit a pathway? (i.e what does "activate" mean and what does "inhibit" mean in terms of a signaling cascade?)
Activation in a signaling cascade means that protein kinases are relaying the ligand through phosphorylation. When the cascade is inhibited, protein phosphatase is preventing the relaying of the signal through dephosphorylation.
Vertebrate immune responses involve communication over short and long distances. Which of the following statements best helps explain how cell surface proteins, such as MHC proteins and T cell receptors, mediate cell communication over short distances? A. The proteins receive electrical signals from nerve cells. B. The proteins leave the cell and travel in the bloodstream to other cells. C. The proteins interact directly with proteins on the surfaces of other cells. D. The proteins bind to molec
Answer: C
Which of the following best explains a possible mechanism that would enable the hormone to efficiently reach all of the targeted cells in the body? A. The hormone interacts with the nerves at the base of the brain and directs signals to the target cells through the nervous system. B. The hormone diffuses into target cells adjacent to the anterior pituitary gland, where the hormone is degraded C. The hormone is released into the bloodstream where it can be transported to all cells with the correc
Answer: C
In flowering plants, plasmodesmata are narrow channels through cell walls that connect the cytoplasms of adjacent cells. An explanation of how plant cells communicate across cell walls will most likely refer to the diffusion through plasmodesmata of which of the following? A. Membrane-bound organelles B. Condensed, duplicated chromosomes C. Branched polysaccharides D. Small, water-soluble molecules
Answer: D
Describe what will happen to a cell if it does not pass the G2 checkpoint.
At the G2 checkpoint, the cell will check for comple5on of duplica5ng the cell and any DNA damage. If the cell is damaged, the cell cycle stops and it will try to fix the damage. If it cannot be repaired, the cell will undergo apoptosis.
How are cancer cells able to leave the original tumor site and metastasize?
Cancer cells are able to metastasize through the circulatory system or lympha5c system. They are able to do this because they no. longer have anchorage dependence.
Describe at least two ways a cancer cell differs from a normal cell
Cancer cells differ from normal cells because they do not follow checkpoints, divide infinitely under the right condi5ons, and evade apoptosis.
How is cancer an example of an inability to maintain homeostasis?
Cancer is an inability to maintain homeostasis because the body cannot regulate cell growth.
Protein Kinase
Causes Phosphorylation
Contact (density) inhibition
Cell surface receptors recognize contact with other cells ○ Initiates signal transduction pathway that stops the cell cycle in G1 phase
Describe the "response" that a cell can have to a signal.
Cells most commonly have three responses to a signal. The signal can trigger a protein that can alter membrane permeability, trigger an enzyme that will change a metabolic process, or trigger a protein that turns on or off.
CAMP
Cyclic AMP (CAMP) is a common second messenger
eukaryotic chromatin is composed of _________
DNA and proteins
normal cells become cancerous through _____ _________
DNA mutations
S (synthesis phase)
DNA replication and chromosome duplication occurs
True or false: insulin signaling is an example of local signaling.
False; long distance signaling
GPCR
G protein coupled receptors
name the two main categories of cell membrane receptors
G protein-coupled receptors (GPCRs), Ion channels
What is G0? What types of cells are in G0?
G0 is a quiescent and dormant state that a cell enters when it does not pass the G1 checkpoint.
examples of plasma membrane receptors
GPCRs, Ligand-gated ion channels
In direct contact communication, animal cells communicate through ______ junctions and plant cells communicate through______.
Gap Plasmodesmata
Why is homeostasis oNen referred to as balance?
Homeostasis is referred to as balance because it is the stable internal condi7ons of an organism.
How many chromosomes do humans have? How many of these are from mom and how many are from dad?
Humans have 46 chromosomes. 23 are from each parent.
What does it mean if a gene is turned off vs on?
If a gene is turned on, that means that the production of a protein will occur and inversely if the gene is turned off-the production of the protein will cease.
If a receptor protein is mutated, can it receive a ligand? Why or why not?
If a protein is mutated, there is a chance that it could not receive a ligand because its the receptor may be damaged or changed.
What would happen to the signal transduction pathway if protein kinase was mutated?
If protein kinase was mutated, the signal transduction pathway would not be activated and therefore no signal would be relayed.
What would happen to the signal transduction pathway if protein phosphatase was mutated?
If protein phosphatase was mutated, the signal transduction pathway would continue to relay the message to other molecules through phosphorylation.
Describe what will happen to a cell if it does not pass the G1 checkpoint
If the cell does not pass the G1 checkpoint, it will enter the G0 phase where the cell does not divide and stays dormant.
example of direct contact
Immune cells - Antigen presenting cells (APCs) communicate to T cells through direct contact
What does the term "signal" refer to in a signal transduction cascade?
In a signal transduction cascade, the signal refers to the ligand/chemical message that will alter a cellular process.
How does cytokinesis differ in plants and animals?
In animal cells, cytokinesis takes place with the formation of a cleavage furrow due to a contractile ring of actin filaments. The cytoplasm will pinch off and the two daughter cells will separate. In plant cells, there is no cleavage furrow. Instead something called a cell plate forms from vesicles to separate the plant cells
What do animals and plants use for long distance signaling? Differentiate between animals and plants when they use this to communicate.
In long distance signaling, animal cells communicate through endocrine signaling. Specialized cells release hormones into the circulatory system where they reach target cells. Plant cells release hormones that travel throughout the plant and vascular tissue (xylem and phloem) or through the air to reach the target tissues.
Gap Junctions
Intercellular channels that permit direct cell-cell transfer of ions and small molecules.
What is the longest portion of the cell cycle?
Interphase (consists of G1, S, and G2.)
After DNA replication, what happens to chromatin?
It condenses into chromosomes
If you were given a problem on the AP exam that described a water-soluble (polar) receptor, where would it be located in the cell?
It would be located in the cell membrane.
What type of communication involves a cell secreting a substance to an adjacent target cell?
Local signaling (paracrine)
plasma membrane receptors
Most common type of receptor involved in signal pathways
What is the main difference between nega7ve and posi7ve feedback?
Negative feedback loops will reduce the effect of a stimulus while positive feedback loops increase the effect.
Neurons can participate in both local and long distance signaling. How is this possible?
Neurons participate in synaptic local signaling when they secrete neurotransmitters that diffuse across the synaptic cleft to reach the target cell. They can also participate in long distance signaling by sending a calcium wave after an axon injury.
synaptic signaling
Occurs in animal nervous systems ● Neurons secrete neurotransmitters ○ Diffuse across the synaptic cleft- space between the nerve cell and target cell
Differentiate between paracrine signaling and synaptic signaling.
Paracrine signaling releases local regulators via exocytosis to an adjacent cell. Synaptic signaling only occurs in animal nervous system cells. It occurs when neurons secrete neurotransmitters that will diffuse across the synaptic cleft.
Ligand-gated ion channels
Plasma Membrane Receptor. Integral membrane proteins that contain a pore which allows the regulated flow of selected ions across the plasma membrane
Differentiate between the role of protein kinase and protein phosphatase in cells.
Protein kinases phosphorylates the signal, or relays it, inside the cell while protein phosphatase shuts off the pathways through dephosphorylation, stopping the signal.
Enzyme protein phosphatase
Relays signal inside cell for dephosphorylation
What do second messengers do, and why is this role so important in some cells?
Second messengers relay and amplify the message and the response.
How is it possible that a single signal molecule can elicit massive cellular responses?
Signal transduction pathways can influence how a cell responds to its environment, this most often is seen when the result changes gene expression and cell function.
How are signals passed from outside of the cell to inside of the cell?
Signals are passed from the outside of the cell to the inside of the cell through a signal transduction pathway, or a sequence of changes in a series of molecules.
differentiate between somatic and gametic cells
Somatic cells are normal body cells and are diploid, meaning in humans they contain 46 chromosomes. Gametes are reproductive cells that are haploid, and only contain 23 chromosomes.
Receptors that bind to estrogen, a hormone would be found where the cell?
They would be found in the cytoplasm.
What is transcription and translation (as it pertains to DNA)?
Transcription is the first step in gene expression and involves copying a gene's DNA sequence to make an RNA molecule. DNA translation is the process by which the genetic code within a messenger RNA molecule is decoded to produce a specific protein.
True or false: the final molecule in a signal transduction pathway can act as a transcription factor, meaning that it can turn genes off or on.
True
What do mutations to receptor proteins result in?
a change to the transduction signal
cytokinesis in animals
a cleavage furrow appears due to a contractile ring of actin filaments
What is the actual "signal" being transduced in a signal transduction pathway?
a ligand
Ligand
a molecule that binds to another (usually larger) molecule.
Plasmodesmata
a narrow thread of cytoplasm that passes through the cell walls of adjacent plant cells and allows communication between them. Plant cells in direct contact with each other can diffuse substances through these structures to communicate.
what filaments are involved in cytokinesis?
actin filaments
genome
all of a cell's genetic information (DNA)
What do all receptors have?
an area that interacts with the ligand and an area that transmits a signal to another protein
Protein Phosphate
an enzyme that removes a phosphate group from a protein.
common second messenger
cAMP
What kind of ligands do intracellular receptors bind to?
can pass through the plasma membrane, hydrophobic molecules
What do activated CDKs lead to?
cell cycle progression
What is an integral part of life?
cell division
What is critical for the function and survival of cells?
cell-to-cell communication
benign tumor
cells are abnormal, but not considered to be cancerous (yet) ● Cells remain at only the tumor site and are unable to spread elsewhere in the body
anchorage dependence
cells rely on attachment to other cells or the extracellular matrix to divide
response
changes (decreases or increases) the effect of the stimulus
DNA mutations
changes in DNA
What are there throughout the cell cycle?
checkpoints
Hormones
chemical substances that act like messenger molecules in the body.
name 3 examples of positive feedback
child labor, blood clotting, fruit ripening
What do strings of nucleosomes form?
chromatin
How do the cells of multicellular organisms work together to maintain homeostasis?
communication
Direct contact
communication through cell junctions
direct contact
communication through cell junctions - Signaling substances and other materials dissolved in the cytoplasm can pass freely between adjacent cells
Concentration of CDK remains ________ through each phase of the cell cycle
constant
Regulation of the cell cycle involves an internal control system that consists of:
cyclins and cyclin-dependent kinases
Where are intracellular receptors found?
cytoplasm or nucleus
What can organisms do to a stimulus?
detect and respond to it
Name the three general ways that cells communicate with each other.
direct contact, local signaling, long-distance signaling
What happens if the body cannot regulate homeostasis?
disease
What happened after DNA replication?
each chromosomes has a duplicated copy
Why are chromosomes densely packed?
easier division
How do animals use hormones in long-distance signaling?
endocrine signaling (endocrine system)
True or false: the concentra5on of cyclins remains constant throughout the cell cycle
false
What does the body maintain homeostasis through?
feedback loops
How do animal cells communicate through direct contact?
gap junctions
Name three reasons why the body might not be able to regulate homeostasis
genetic disorders, drugs or alcohol abuse, intolerable conditions (extreme heat or cold)
What do cells receive with checkpoints?
go/stop signals
The GPCR, enzyme, and G protein are _______ until ligand binding to GPCR on the extracellular side
inactive
positive feedback
increases effect of stimulus
what does receptor activation allow?
interaction with other cellular molecules
The body must be able to monitor its _________ ____________ at all times
internal conditions
What alternating phases does the cell cycle contain?
interphase and mitosis
What happens when the ligand binds to the receptor?
it activates
receptor
macromolecule that binds to a signal molecule (ligand)
Receptor
macromolecule that binds to a signal molecule (ligand)
malignant tumor
mass of cancerous cells that lose their anchorage dependency and can leave the tumor site
effector
muscle or gland that will respond
Does every eukaryote have the same number of chromosomes?
no
What do set points have that can fluctuate?
normal range
Wat do histones form?
nucleosomes
eukaryote genome
one or more linear chromosomes
What must cells do before they divide?
organize and package their DNA
What type of communication involves a cell secreting a substance to an adjacent target cell?
paracrine signaling
examples of local regulators
paracrine signaling and synaptic signaling
How does the signal transduction pathway regulate protein activity?
phosphorylation and dephosphoylation
Where are receptors located?
plasma membrane or inside the cell (intracellular)
How do plant cells communicate through direct contact?
plasmodesmata
Plant cells in direct contact with each other can diffuse substances through these structures to communicate. What are they?
plasmodesmata
Checkpoints ________
points that regulate the cell cycle
What kind of ligands do plasma membrane receptors bind to?
polar, water-soluble, large
Name the 5 phases of mitosis. in order
prophase, prometaphase, metaphase, anaphase, telophase
phosphorylation by the enzyme ______ __________
protein kinase
dephosphorylation by the enzyme ______ __________
protein phosphatase
kinetochore
proteins attached to the centromere that link each sister chromatid to the mitotic spindle
cell-to-cell stages
reception, transduction, response
what does negative feedback do?
reduces effect of stimulus
What does phosphorylation do?
relays signal inside the cell
insulin
released by the pancreas into the bloodstream where it circulates through the body and binds to target cells
What does cell division allow?
reproduction of cells, growth of cells, and tissue repair
paracrine signaling
secretory cells release local regulators (ie growth factors) via exocytosis to an adjacent cell
receptor/sensor
sensory organs that detect a stimulus. This information is sent to the control center (brain)
Movement of the chromosomes during anaphase would be most affected by a drug that prevents ________
shortening of microtubules
What does dephosphorylation do?
shuts off pathways
What is initiated with growth factors?
signal transduction pathway
what does transduction require?
signal transduction pathway
How does communication occur in cells of multicellular organisms?
signal transduction pathways
prokaryote genome
singular, circular DNA
What do the joined copies of chromosomes form?
sister chromatids
Second messengers
small, non-protein molecules and ions help relay the message and amplify the response
second messenger
small, non-protein molecules and ions help relay the message and amplify the response
Does mitosis occur in soma5c or gametic cells?
somatic
name 3 examples of negative feedback
sweat, blood sugar, breathing rate
Cyclins are _________ and ____________ at specific stages of the cell cycle
synthesized, degraded
diabetes
the body cannot regulate blood glucose levels
cancer
the body cannot regulate cell growth
Transduction
the conversion of an extracellular signal to an intracellular signal that will bring about a cellular response
transduction
the conversion of an extracellular signal to an intracellular signal that will bring about a cellular response
Reception
the detection and receiving of a ligand by a receptor in the target cell
reception
the detection and receiving of a ligand by a receptor in the target cell
Response
the final molecule in the signaling pathway converts the signal to a response at will alter a cellular process
response
the final molecule in the signaling pathway converts the signal to a response that will alter a cellular process
What is cell-to-cell communication responsible for?
the growth and development of multicellular organisms
cell cycle
the life of a cell from its formation until it divides
centromere
the region on each sister chromatid where they are most closely attached
What is amplified during transduction?
the signal
Homeostasis
the state of relatively stable internal conditions
