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