advanced molecular and cell bio exam 3 class questions and kahoot

Actin filaments and microtubules have an inherent polarity, with a plus end that grows more quickly than the minus end. True or false?

true

Each intermediate filament is about 10 micrometers. True or false?

false, 10nm

All intermediate filaments are of similar diameter because

the central rod domains are similar in size and amino acid sequence

Intermediate filaments help protect animal cells from mechanical stress because filaments

in each cell are indirectly connected to filaments of a neighboring cell through the desmosome, creating a continuous mechanical link between cells

Alpha-tubulin and beta-tubulin are covalently bound to make the tubulin dimer that then assembles into profilaments. True or false?

false, held together by non-covalent interactions

Microtubules emanating from the centrosome have alternating polarity such that some have their plus ends attached to the centrosome while others have their minus ends attached to the centrosome. True or false?

false, the minus end always at centrosome, plus end grows and shrinks

Motor proteins move in a directional fashion along microtubules by using inherent structural polarity of a profilament. True or false?

true

The microtubules in a cell form a structural framework that can strengthen the plasma membrane. True or false?

false, actin filaments do

The newly freed tubulin dimers from a shrinking microtubule can be immediately captured by growing microtubules added to their plus end. True or false?

false, tubulin needs to exchange GDP for GTP first

Only the microtubule cytoskeleton is involved in organellar movement. True or false?

false, both microtubules and actin filaments involved

Kinesins and dynein often move in opposite directions to each other. True or false?

true

Microtubules within an axon are arranged such that all microtubules point in the same direction with their minus ends toward the nerve cell body. True or false?

true

For both actin and microtubule polymerization, nucleotide hydrolysis is important for decreasing the binding strength between subunits of filaments. True or false?

true

The layer of photoreceptors in the eye is an example of connective tissue. True or false?

false, epithelial tissue

In connective tissue, the extracellular matrix carries the mechanical load. True or false?

true

Cells can attach to a collagen matrix by using fibronectin, an integral transmembrane protein. true or false?

false, integrin is the transmembrane protein

Proteoglycans can resist compression in the extracellular matrix. True or false?

true

Collagen synthase organizes the mature collagen molecules into ordered collagen fibrils. True or false?

false, fibroblasts secrete and organize collagen

A cell can crawl through a tissue because of the transmembrane integrin proteins that can bind fibronectin outside of the cell. True or false?

true

Integrins use adaptor proteins to interact with the microtubule cytoskeleton. True or false?

false, integrins can only interact with actin or intermediate filaments

Proteoglycans are a major component of compact connective tissues but are relatively unimportant watery tissues such as the jellylike substance in the interior of the eye. True or false?

false, they are important in extracellular matrix

A basal lamina is a thin layer of connective tissue, cells, and matrix underlying the epithelium. True or false?

false, a thin layer of extracellular matrix only (no cells)

Tight junctions interact with the intermediate filaments inside the cell. True or false?

false, desmosomes do that. (tight junctions not involved in interactions with cytoskeleton)

Adherent junctions can be used to bend or invaginate epithelial sheets into tubes or vesicles. True or false?

true

At desmosomes, cadherin molecules are connected to actin filaments. True or false?

false, they connect to intermediate filaments like keratin

Hemidesmosomes are important for attaching epithelial cells to the extracellular matrix (or basal lamina). True or false?

true (basal lamina or extracellular matrix)

A major distinction between the connective tissues in animals and other main tissue types such as epithelium, nervous tissue, or muscle is the amount of extracellular matrix in connective tissue. True or false?

true (can find most extracellular matrix in connective tissue)

Because gap junctions only allow uncharged molecules through, they are not used to electrically coupling cells. True or false?

false, ions can pass through and be used to electrically couple cells

Adherens junction involves a connection to the actin cytoskeleton. True or false?

true

Adherens junctions contribute the most to the polarization of epithelial cells. True or false?

false, tight junctions polarize the epithelium

Cadherins mediate cell-cell attachment through homophilic interactions. True or false?

true

cells that are terminally differentiated can undergo cell division. true or false?

false, unless you introduce transfusion factors to induce stem cell production

when a terminally differentiated cell in an adult body dies, it can typically be replaced in the body by a stock of proliferating precursor cells. true or false?

true

an adult hemopoietic stem cell found in the bone marrow can undergo self-renewing divisions for the lifetime of a healthy animal. true or false?

true

a multipotent cell can give rise to all the tissues and cell types in the body. true or false?

false, only totipotent or omnipotent stem cells can

mouse embryonic stem (ES) cells come from inner cell mass of early embryos. true or false?

true

induced pluripotent stem (iPS) cells can be create by the expression of a set of key hormones in most somatic cell types, including cells derived from adult tissues. true or false?

false; for hormones, for new genes introduced in cells

organoids are self-assembling, can be produced from ES and iPS cells, and can come from multilayered structures. true or false?

true

a malignant tumor is more dangerous than a benign tumor because its cells invade other tissues. true or false>

true

a metastasis is a part of the primary tumor that has invaded the surrounding tissue. true or false?

false; metastasis is when cancer cells break away and travel through the body to start new tumors in distant parts of the body

a mutation in even a single cancer-critical gene is sufficient to convert a normal cell into a cancer cell. true or false?

false; a single mutation is not enough (multi step process)

a mutation that introduces a stop codon immediately after the codon for the initiator methionine can convert a proto-oncogene into an oncogene. true or false?

false; it would terminate translation

cells with one functional copy of a tumor suppressor gene will usually proliferate faster than normal cells. true or false?

false; tumor suppressor gene would act to stop cell division

Ras is a GTP-binding protein that is defective in cancer cells. a common mutation found in cancer cells causes Ras to behave as though it were bound to GTP all the time, which will cause cells to divide inappropriately. from this description, the normal Ras gene is a/an oncogene. true or false?

false; the normal unmutated Ras gene is a proto-oncogene

radiotherapy kills dividing cancer cells directly by damaging them with high energy beams of photons, protons, electrons... true or false?

true

CTLA-4 antibodies work mainly by preventing antigen-presenting cells from priming T cells to recognize tumors. true or false?

true

angiogenesis inhibitors do not harm most normal dividing cells because they directly attack cancer cells. true or false?

false; they block angiogenesis and starve cancer cells (don't attack them directly)

CAR T-cell therapy includes collection and growth of the patient T cells in the laboratory, addition of an engineered chimeric agent receptor that recognizes cancer cells and giving the engineered T cells back to the patient. true or false?

true

high estrogen levels help estrogen receptor-positive breast cancer grow and spread. thus an anti-estrogen drug should be able to block growth of breast cancer. true or false?

true

actin filaments and microtubules have an inherit polarity, with a minus end that grows more quickly than the plus end. true or false?

false, the plus end grows faster

all intermediate filaments are of similar diameter because their central rod domains are similar. true or false?

true

microtubules help protect animal cells from mechanical stress. true or false?

false, intermediate filaments

motors move in a directional fashion along microtubules by using the inherent structural polarity of a protofilament. true or false?

true

actin filaments in a cell form a structural framework that can strengthen the plasma membrane. true or false?

true

the newly freed tubulin dimers from a shrinking microtubule can be immediately added to their plus end. true or false?

false; have to first exchange GDP for GTP

the hydrolysis of GTP to GDP on tubulin molecules allows the behavior of microtubules called dynamic instability. true or false?

true

both microtubules and actin filaments are involved in intracellular movement of organelles. true or false?

true

All eukaryotic cells have cytoplasmic intermediate filaments. true or false?

false; all animal cells do

Nucleotide hydrolysis is important for decreasing their binding strength between subunits on actin filaments. true or false?

true

Microtubules, dynein, and ATP are critical for ciliary and flagellar movements. true or false

true

The layer of auditory hair cells in the ears is an example of an epithelial tissue. true or false

true

Tissues are organized assemblies of cells, held together by extracellular matrix and/or cell-cell adhesions. true or false

true

Collagen provides tensile strength in animal connective tissues. true or false

true

Procollagen precursors are cleaved to form mature collagen inside the cell. true or false

false; procollagen is cleaved outside the cell

Fibroblasts organize the collagen by pulling the collagen into sheets or cables after it has been secreted. true or false

true

Fibronectin and transmembrane integrin proteins help attach a cell to the extracellular matrix . true or false

true

An integrin protein switches to an active conformation when it binds to molecules on either side of the plasma membrane. true or false

true

Proteoglycans are composed of a core protein to which the highly negatively charged GAGs are attached . true or false

true

A cell can crawl through a tissue because of the integrin proteins that can directly bind to extracellular collagens. true or false

false; bind indirectly through fibronectin

Integrins use adaptor proteins to interact with the actin cytoskeleton. true or false

true

Aggrecan-hyaluron aggregates are formed by attaching proteoglycans to hyaluronan through linker proteins. true or false

true

The majority of cells in a vertebrate are organized into epithelia. true or false

true

Epithelial sheets are polarized and rest on a basal lamina. true or false

true

A basal lamina is a thin layer of extracellular matrix underlying an epithelium. true or false

true

Desmosomes use adaptor proteins to interact with the actin filaments inside the cell. true or false

false; connect intermediate filaments

Hemidesmosomes link the intermediate filaments of one epithelial cell to those of another. true or false

false; link intermediate filaments to basal lamina/ECM

Cadherin proteins, by joining adherens junctions or desmosomes, mediate physical attachment of one cell to another. true or false

true

At desmosomes, cadherin molecules are directly connected to intermediate filaments. true or false

false; connected to intermediate filaments indirectly through adaptor/plaque proteins

Laminins and transmembrane integrins are important for hemidesmosomes to attach epithelial cells to the basal lamina. true or false

true

Gap junctions provide neighboring cells with a direct channel of intercytosolic communication. true or false

true

Tight junctions contribute most to the polarization of epithelial cells. true or false

true

When a terminally differentiated cell in an adult body dies, it can typically be replaced by a stock of stem cells. true or false

true

An adult hemopoietic stem cell found in bone marrow can only undergo self-renewing divisions for about 2 months. true or false

false; for life

A pluripotent cell can differentiate into almost all cell types but not extraembryonic cells. true or false

true

Embryonic stem cells can be induced to differentiate into specific cell types in culture. true or false

true

An artificial introduction of four key genes can convert an adult cell with the properties of ES cells. true or false

true

Unlimited replicative potential and genome instability are the only major hallmarks of cancer cells. true or false

false; multiple major hallmarks

The normal Wnt gene is an oncogene because it promotes proliferation of stem cells. true or false

false; proto-oncogene

Loss-of-function mutations in oncogenes generally act in a dominant manner. true or false

false; recessive

Activation of proto-oncogenes and inactivation of tumor suppressor genes can only happen by a specific point mutation. true or false

false; multiple mechanisms

Tumors evolve by repeated rounds of mutation, proliferation, and natural selection. true or false

true

Metastasis is a process by which tumor cells leave the primary tumor and establish secondary tumors in other sites . true or false

true

Loss of heterozygosity (LOH) of the WT allele can cause BRCA1 biallelic inactivation and thus breast cancer development . true or false

true

The APC protein keeps the Wnt signaling pathway active by stabilizing β-catenin that triggers gene transcription. true or false

false; pathway inactive by promoting beta-catenin degradation

Radiation therapy uses high-energy X-rays, gamma rays, electron beams, or protons to damage cancer cells. true or false

true

PD-L1 binds to PD-1 and inhibits our immune system from killing tumor cells. true or false

true

Inhibitors of vascular endothelial growth factor can block angiogenesis and starve cancer cells to death. true or false

true

Androgen suppression therapy reduces level of a male hormone and stop prostate cancer development . true or false

true

The ability of chemotherapy to kill cancer cells depends on its ability to halt cell division. true or false

true