Cell Biology- Exam 4

Cell cycle checkpoints

are critical points that determine whether or not the cell cycle proceeds to the next phase of cell division

The signaling molecules called steroid hormones

are made in one location of the body but have their effects some distance away

G-protein, tyrosine kinase-, and ion channel-coupled receptors are similar in that they

are transmembrane proteins and change their confirmation when bound to a signaling molecule

G-protein-coupled, enzyme-couples, and ion channel-coupled receptors are similar in that they

are transmembrane proteins that specifically interact with hydrophilic signaling molecules

Which of the following precede the cytokinesis in animal cells? a) decondensation of chromosomes b) assembly of the contractile ring c) cell junction formation d) spindle fiber formation

assembly of the contractile ring

Which of the following events directly leads to the cytokinesis in animal cells?

assesmebly of the contractile ring

When a signal needs to be transmitted a synapse, the signaling molecule most suited for this will be a

neurotransmitter

Protein phosphorylation is involved in all of the following signal pathways except a) neurotransmitter activated ion channels b) epinephrine mediated signaling c) gap junction mediated signaling d) insulin mediated cell signaling

neurotransmitter activated ion channels

A signaling molecule can bind to and disassociate from its receptor quickly. This is usually mediated by

noncovalent interactions

The binding of a signaling molecule to its receptor is mediated by

noncovalent interactions

During which stage of the cell cycle is the chromosome content of a mammalian liver cell 1n (Haploid)? a) S b) G1 c) G2 d) none of the above

none of the above

A mutated gene contributes to uncontrolled cell growth. What term best describes this gene?

oncogene or tumor suppressor gene

Unipotent neural stem cells from the brain can differentiate into which types of cells?

only specialized brain cells

A fibroblast secretes bFGF that binds to receptors of nearby endothelial cells causing them to proliferate. This is an example of

paracrine signaling

This organelle participates actively in apoptosis

mitochondria

A proto-oncogene is

a normal gene that helps cells grow

Severe damage to the inner membrane of mitochondria can cause

apoptosis and malfunction of cellular response

Cells in the G0 state

do not divide

What process best explains how muscle cells and nerve cells can develop from the same embryonic stem cells?

differentiation

Cancer cells are said to "break the rules" because they

- can evade apoptosis -lost contact-inhibition -lost anchorage-dependent growth property

What are the roles of stem cells in the growth and development of an organism?

- to produce new cells for tissue and organ formation in the fetus -to produce new specialized cells in the body to replace old cells or damaged cells

Which of the following genetic changes cannot convert a proto-oncogene into an oncogene? a) A mutation that introduces a stop codon immediately after the codon for the initiator methionine b) An amplification of the # of copies of the proto-oncogene, causing overproduction of the normal protein c) A mutation in the coding region of the proto-oncogene, causing increased stability of the protein d) A mutation within the coding sequence that makes the protein constitutively active

A mutation that introduces a stop codon immediately after the codon for the initiator methionine

Which of the following statements about cancer is FALSE? a) Human cancers are related to exposure of carcinogens b) It is characterized by uncontrolled cell division c) It is caused by an accumulation of mutations d) All cancers involve genetic changes that are passed from parent to offspring

All cancers involve genetic changes that are passed from parent to offspring

Which of the following statements about apoptosis is TRUE? a) Cells that constitutively express cdks to undergo apoptosis b) The caspases are constitutively active as soon as they are synthesized c) Growth factors promotes apoptosis by binding to death receptor on the cell surface d) Apoptosis can be promoted by the release of cytochrome C in the cytosol from the mitochondria

Apoptosis can be promoted by the release of cytochrome C in the cytosol from the mitochondria

In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated? a) When cells enter G0 b) At the end of G2 c) During mitosis d) at the transition between G1 and S

At the end of G2

A cell at the interphase of cell division does not undergo dramatic change morphologically as in the M phase, but it is biochemically active because it is actively engaged in

DNA synthesis

induced pluripotent stem cells (iPSCs)

Derived from adult cells that have been reprogrammed back into an embryonic-like cells

What is the role of the caspases in apoptosis?

Caspases are proteases that carry out the controlled destruction of the cell's components during apoptosis.

Which of the following statements about tumor suppressor genes is FALSE? a) Individuals with only one functional copy of a tumor suppressor gene are more prone to cancer than individuals with two copies of a tumor suppressor gene b) Cells with a defective tumor suppressor gene will proliferate slower than normal cells c) Inactivation of tumor suppressor genes leads to enhanced cell proliferation d) Gene amplification of tumor-suppressor gene is likely less dangerous than gene amplification of an oncogene.

Cells with a defective tumor suppressor gene will proliferate slower than normal cells

Which best explains why muscle cells are different from blood cells?

Different genes are activated and expressed in muscle cells and blood cells

What is a major difference between embryonic stem cells and adult stem cells?

Embryonic stem cells can differentiate into more cell types than adult stem cells

Which of the following statements about cancer is FALSE? a) Even a single gene mutation is sufficient to convert a normal cell into cancer cells. b) Tobacco use us responsible for certain types of lung cancers c) Viruses can cause some cancers d) Chemical carcinogens cause cancer by changing the nucleotide sequence of DNA

Even a single gene mutation is sufficient to convert a normal cell into cancer cells.

Which of the following statements is TRUE? a)Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor to elicit a response in the target cell

Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor to elicit a response in the target cell

Which of the following statements is false? a) Both G-protein-linked receptors and tyrosine kinase-linked receptors are expressed on the plasma membrane b) G-protein linked receptors span the plasma membrane seven times, tyrosine kinase-linked receptors span the membrane once per polypeptide chain c) G protein-linked receptors form dimers when activated, tyrosine kinase-linked receptors do not d) G protein-linked receptors activate adenylate cyclase signaling pathways, tyrosine-linked receptors do not

G protein-linked receptors form dimers when activated, tyrosine kinase-linked receptors do not

Which signaling molecule is composed of alpha, beta, and gamma subunits?

G-protein

Which of the following statements about G-protein-coupled receptors (GPCRs) is FALSE? a) GPCRs are widely used cell surface receptors for cell signaling b) GPCRs are cell-surface receptors in humans c) GPCRs transduce signals for hydrophilic hormones d) GPCRs have different numbers of transmembrane domains (segments)

GPCRs have different numbers of transmembrane domains (segments)

Acetylcholine is a signaling molecule that elicits responses from heart muscle cells, salivary gland cells, and skeletal muscle cells. Which of the following statements is false? a) Heart muscle cells decrease their rate and force of contraction when they receive acetylcholine whereas skeletal muscle cells contract b) Acetylcholine receptors on salivary gland cells and heart muscle cells activate different intracellular signaling pathways c) Heart muscle cells, salivary gland cells, and skeletal muscle cells have different rate of acetylcholine metabolism d) Heart muscle cells, salivary gland cells and skeletal muscle cells all respond to acetylcholine

Heart muscle cells, salivary gland cells, and skeletal muscle cells have different rate of acetylcholine metabolism

Where are the stem cells that renew the skin epithelium?

In the basal layer of the epidermis

A cell is known to respond to a particular signaling molecule. Which of the following must be true of this cell?

It contains the receptor for the signaling molecule

How does a somatic cell that has just completed the S phase of its cell cycle compare in respect to its number of chromosomes and amount of DNA with a gamete of the same species?

It has twice the number of chromosomes and dour times the amount of DNA

Which of the following statements about a G-protein-coupled receptor is FALSE? a) It is an integral membrane protein with 7-pass transmembrane domains b) It interacts with a G-protein c) It is a receptor with GTPase activity d) It transduces signals for signaling molecules that cannot pass through cell membrane

It is a receptor with GTPase activity

Synaptic signaling between adjacent neurons is like hormone signaling in which of the following ways?

It requires binding of a signaling molecule to a receptor

Which of the following statements regarding the G1 phase of the eukaryotic cell cycle is NOT true? a) Cells that are terminally differentiated may exit the G1 phase and enter the G0 phase b) If the environmental conditions are favorable during the G1 phase, the cell will prepare to replicate its DNA c) Most cells spend the majority of their lives in the G1 phase of the cell cycle d) Most organelles are duplicated at the G1 phase.

Most organelles are duplicated at the G1 phase

Which of the following statements regarding the G1 phase of the eukaryotic cell cycle is NOT true? a) Determining if the internal and external conditions are suitable for cell division b) Cells that are terminally differentiated may exit the G1 phase and enter the G0 phase c) G1 checkpoint allows cell enter S phase only is the external environment is right for cell division d) Most organelles are duplicated at the G1 phase before DNA replication

Most organelles are duplicated at the G1 phase before DNA replication

Which of the following statements about the cell cycle is FALSE? a) once a cell decides to enter the cell cycle, the time from start to finish is the same in all eukaryotic cells. b) The DNA content is duplicated during S phase c) A cell has more DNA during G2 than it did in G2 d) An unfavorable environment can cause cells to arrest in G1

Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eukaryotic cells

Which of the following statements is FALSE? a) Phosphatases remove the phosphate from GTP on GTP binding proteins, turning them off. b) Serine, threonine, and tyrosine are the three amino acid residues that are commonly phosphorylated by protein kinases c) A GTP-protein exchanges its bound GDP for GTP to become activated d) Protein kinases transfer the terminal phosphate from ATP onto a protein

Phosphatases remove the phosphate from GTP on GTP binding proteins, turning them off.

The insulin pathway includes which of the following steps

Phosphorylation of insulin receptor substrate-1 insulin-induced dimerization of the receptors inducing the translation of glucose transporter to the cell membrane

The lab you work in has discovered a previously unidentified extracellular signal molecule called QGF, a 75,000-dalton protein. You add purified QGF to different types of cells to determine its effect on these cells. When you add QGF to heart muscle cells, you observe an increase in cell contraction. When you add it to fibroblasts, they undergo cell division. When you add it to nerve cells, they die. When you add it to glial cells, you do not see any effect on cell division or survival. Given these observations, which of the following statements is most likely to be true?

QGF activates different intracellular signaling pathways in heart muscle cells, fibroblasts, and nerve cells to produce the different responses observed

Which of the following statements is FALSE concerning sister chromatids? a) Sister chromatids separate during G2 phase. b) Sister chromatids are formed during the S phase of the cell cycle c) Sister chromatids consist of two identical copies of a single homologue d) The formation of sister chromatids doubles the amount of DNA in a cell

Sister chromatids separate during G2 phase

The following happens when a G-protein-coupled receptor activates a G protein.

The alpha subunit exchanges its bound GDP for GTP

Name two defining features of stem cells

The capacity to differentiate into specialized cell types and self-renewal

Which of the following statements about cancer is NOT accurate? a) Escaped cell cycle control b) Divide excessively even in the absence of growth factors c) They always form a solid tumor d) Defective in apoptosis

They always form a solid tumor

induced pluripotent stem cells (iPSCs)

are created from differentiated somatic cells by forced expression of a set of key genes that control pluripotency

Which of the following statements is true? a) The contractile ring is made largely of microtubules and actin filaments. b) The mitotic spindle is largely made of intermediate filaments c) The mitotic spindle helps segregate the chromosomes to the two daughter cells d) The contractile ring divides the nucleus in two

The mitotic spindle helps segregate the chromosomes to the two daughter cells

What is the role of stem cells with regard to the function of adult tissues and organs?

They are undifferentiated cells that divide asymmetrically, giving rise to one daughter that remains a stem cell and one daughter that will differentiate to replace damaged and worn out cells in the adult tissue or organ.

Which of the following is NOT an accurate description of a checkpoint that controls the progression of the cell cycle? a) Timing the cytokinesis to separate daughter cells b) The G1 checkpoint determines if conditions are favorable for cell division c) The G2 checkpoint checks for DNA damage and determines if all of the DNA is replicated d) The metaphase checkpoint determines if all chromosomes are attached to the spindle apparatus

Timing the cytokinesis to separate daughter cells

What are adult stem cells?

Undifferentiated cells found in different parts of the body that divide to replenish dying cells and regenerate damaged tissues

Which of the following statements about the cell cycle is correct? a) The phases of the cell cycle are G1, S, and M phases. b) When the S phase of the cell cycle is finished, a cell has twice as much DNA as it did during the G1 phase. c) During G2 phase, the cell grows and copies its chromosomes in preparation for cell division d) In actively dividing cells, the S and G2 phases are collectively known as interphase

When the S phase of the cell cycle is finished, a cell has twice as much DNA as it did during the G1 phase

Diabetics can be given insulin which binds to receptors on cells throughout the body increasing glucose uptake. The receptor that medicates the effect of insulin is an example of

a cell surface receptor with tyrosine kinase activity

The growth factor Superchick stimulates the proliferation of cultured chicken cells. The receptor that binds Superchick is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation? (a) a mutation that prevents dimerization of the receptor (b) a mutation that destroys the kinase activity of the receptor (c) a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor (d) a mutation that prevents the binding of the normal extracellular signal to the receptor

a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor

A somatic cell is

any cell of a living organism other than the reproductive cells

In paracrine signaling, the signaling molecule

acts on cells in close proximity to the secreting cell

Which of the following statements is true? a) Because endocrine signaling are carried by blood, all cells in the body will respond to the signals b) Paracrine signaling is part of the endocrine signaling c) acts on the same cells that secreted the signaling molecule d) acts on cells in close proximity to the secreting cell

acts on cells in close proximity to the secreting cell

When epinephrine binds to its G-protein linked receptor

adenylyl cyclase is activated producing cAMP

Autocrine signaling is involved in which of the following cell communication mechanisms?

local signaling

When a signal is released from neuron and it moves to another neuron or to a muscle cell, the signal

binds to a cell surface receptor

Embryonic stem cells are isolated from

blastocyst

Programmed cell death occurs

by means of an intracellular suicide program

The hydrolytic enzymes involved in necrosis are likely released from

lysosomes

The process by which haploid cells are produced from diploid cells is called

meiosis

Which of the following is an intracellular second messenger?

cAMP

Which of the following is an intracellular second messenger? a) glucose b) cAMP c) ATP d) Insulin

cAMP

A hemopoietic stem cell found in the bone marrow

can differentiate into all types of blood cells

Which protein is directly involved in apoptosis?

caspase

Apoptosis differs from necrosis in that necrosis

causes cells to swell and burst, whereas apoptotic cells shrink and condense.

G-protein-coupled receptors, RTKs, and ion channel-coupled receptors are similar in that they

change their conformation when bound to a signaling molecule

Cell signaling through a gap junction is an example of

contact-dependent signaling

Cell signaling through gap junction is an example of

contact-dependent signaling

Cell signaling via gap junction is a form of

contact-dependent signaling

Sodium ions move from one cardiac muscle cell to an adjacent cell via gap junction causing them to contract in unison. This is an example of

contact-dependent signaling

When cancer cells have the ability to migrate to other parts of the body, they are said to be

metastatic

The local mediator nitric oxide stimulates the intracellular enzyme guanylyl cyclase by

diffusing into cells and stimulating the cyclase directly

A cell that lacks Cdk activity in M phase will be unable to a) form a contractile ring b) disassemble its nuclear lamina at prometaphase c) begin to assemble a mitotic spindle d) condense its chromosomes at prophase

disassemble its nuclear lamina at prometaphase

Insulin is secreted from the pancreas and acts on muscle cells to increase glucose uptake. This is an example of

endocrine signaling

Dimerization induced receptor activation is a mechanism commonly utilized by

enzyme-coupled receptors

Which of the following signaling molecules pass through the plasma membrane of cells and have receptor molecules in the cytoplasm? a) insulin b) epinephrine c) cAMP d) estrogen

estrogen

Many growth factors are

extracellular signals that stimulate cell division

Mitotic cyclin (M cyclin) a) is highest in G1 phase b) activates Cdk essential for all phases of the cell cycle c) is activated by phosphorylation d) falls in concentration at the end of M phase as a result of degradation

falls in concentration at the end of M phase as a result of degradation

Which of the following is the best evidence that cell communication evolved early in the history of living things?

from bacteria to humans, different organisms share some common signaling mechanisms at the cellular level

Which of the following is not a type of signaling molecule? a) insulin b) testosterone c) acetylcholine d) glucose

glucose

Apoptosis is

highly controlled; cells digest themselves by activating a caspase cascade without eliciting any immune response

When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a ___________.

hormone

A cell that is terminally differentiated (at G0 phase) will a) inactivate its cell-cycle control system b) arrest after S phase c) replicate its DNA d) reenter the cell cycle only once a year

inactivate its cell-cycle control system

After being fed glucose a cell increases its intracellular glucose concentration by

increasing membrane glucose transporters

Levels of cyclin-dependent kinase (CDK) activity change during the cell cycle due to

interaction with cyclins

Autocrine signaling

is a cell releasing a signaling molecule that binds to receptors on its own surface

Autocrine signaling

is a form of local signaling

Autocrine signaling is

is a form of local signaling

A mutated malignant tumor is more dangerous than a benign tumor because

its cells invade other tissues

A cell with nuclear lamins that cannot be disassembled in M phase is likely due to

lacking Cdk activity

When a cell releases a signal molecule into the environment and a group of different cells in the immediate vicinity respond, this type of signaling is

paracrine signaling

In mitosis and cytokinesis, the main difference between plant and animal cells is that

plants produce a cell plate to segregate the daughter nuclei, while animals form a cleavage furrow

Cells that are capable of developing into most, but not all, of the body's cell types, are defined as ___________. These cells are represented by ______________.

pluripotent stem cells; embryonic stem cells

What is the property of a signal molecule that is most likely to bind to a receptor on the cell membrane?

polar, hydrophilic

A 48-year-old woman has a malignant lymphoma involving lymph nodes in the para-aortic region. She is treated with a chemotherapeutic agent which results in the loss of individual neoplastic cell nuclei and cytoplasm. Over the next 2 months, the lymphoma decreases in size, as documented on abdominal CT scans. By which of the following mechanisms has her neoplasm primarily responded to therapy?

programmed cell death

Which of the following molecules is a critical signaling component that mediates the effect of adrenaline (epinephrine)?

protein kinase A

You identify a new hormone, and wish to characterize its mechanism of action. You find that when it is added to health cells, cyclic AMP levels quickly rise. What type of signaling molecule is likely being activated by this hormone?

protein kinase A

Which of the following plasma membrane receptors activate signaling pathways usually by forming molecular dimers that result in protein phosphorylation reactions upon binding of their specific ligand?

receptor tyrosine kinases

Which of the following mechanisms is NOT directly involved in inactivating an activated receptor tyrosine kinase (RTK)? a) phosphorylation by protein kinase b) dimerization of RTK c) recruiting of adapter proteins to the cell membrane d) dephosphorylation by protein tyrosine phosphatases

recruiting of adapter proteins to the cell membrane

From the perspective of the cell receiving the message, the three stages of cell signaling are

signal reception signal transduction cellular response

Which of the following statements is true? a) the paracrine, local, and synaptic stages b) signal reception, signal transduction, and cellular response c) signal reception, gene expression, and cellular response d) signal reception, cellular response, and cell division

signal reception, signal transduction, and cellular response

Diabetics can be given insulin which binds to receptors on cells throughout the body increasing glucose uptake. Insulin is an example of

signaling molecule

Which type of signaling system sends neurotransmitter from signaling cell to the target cell?

synaptic signaling

Cell proliferation is the process of increasing the cell number through cell division while cell differentiation is the process of cells gaining specialized functions. These two processes are often mutually exclusive during development. Based on this information, you would expect that a cell at the interphase of the cell cycle would be actively engaged in the following activities except a) DNA synthesis b) synthesis of steroid hormones c) replication of organelles d) synthesis of cyclins

synthesis of steroid hormones

Levels of cyclin-dependent kinase (cdk) activity change during the cell cycle as a result of

the Cdks binding different cyclins to become active

What does "self-renewal" mean?

the ability of stem cells to go through numerous cycles of cell division while maintaining the undifferentiated state. Can only divide and make one cell type

Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to

the active site of an allosteric enzyme that binds to a specific substrate

A receptor protein in a membrane that recognizes a chemical signal is most similar to

the active site of an enzyme that binds to a specific substrate

Progression through the cell cycle requires a cyclin to bind to a cdk because

the binding of a cyclin to Cdk is required for Cdk enzymatic activity

Levels of Cdk activity change during the cell cycle, in part, because ________________.

the levels of cyclins change during the cycle

Which of the following statements is true?

the regulation of inflammatory responses at the site of an infection is an example of paracrine signaling

A germ cell or gamete is

the reproductive cells of an organism

After estrogen binds to its intracellular receptor, the activated estrogen receptor acts as a

transcription factor

The artificial introduction of 4 ________ into an adult cell can convert the adult cell into a cell with the properties of embryonic stem cells.

transcription factors

A blastocyst has a _________, which will become and placenta and an ___________ which will become the rest of the embryo

trophectoderm, inner cell mass

When signal molecule binding results in dimerization of receptors and phosphorylation at the cell membrane, the receptors involved are more likely

tyrosine-kinase receptors

Stem cells are defined as

undifferentiated cells that can reproduce themselves and can differentiate into other types of cells