Bio 314 Final Exam Practice

Which of the following best describes an oncogene? A gain of function mutation in a gene whose normal function is to promote cell division or perform some other "pro-cancer" activity. A loss of function mutation in a gene whose normal function is to promote cell division or perform some other "pro-cancer" activity. A gain of function mutation in a gene whose normal function is to block cell division or perform some other "anti-cancer" activity. A loss of function mutation in a gene whose normal function is to block cell division or perform some other "anti-cancer" activity.

A gain of function mutation in a gene whose normal function is to promote cell division or perform some other "pro-cancer" activity.

A particular enzyme is regulated by phosphorylation. If phosphorylation decreases its Km by a factor of 3, but does not change its Vmax, what effect does phosphorylation have on the enzyme activity? Inhibits Activates Has no effect on enzyme activity

Activates

Which of the following statements is true about active transport? Active transport is required only for the transport of macromolecules - small molecules can diffuse across membranes passively Active transport cannot be performed by transporters Active transport is required for movement of molecules down a concentration gradient Active transport requires an input of energy

Active transport requires an input of energy

Which of the following is true about ion channels? Their activities can be measured by the patch clamp technique They are transmembrane proteins They are selective for one type of ion They exist in open and closed conformations All are true about ion channels

All are true about ion channels

For a reaction to occur spontaneously: The reaction is energetically favorable ∆G is negative Products have a lower energy than reactants All of the above Free energy must be released

All of the above

Why might you choose to use the nematode C. elegans as a model organism for studying a human genetic defect? All of the genes in humans are also present in C. elegans. Any drugs discovered to act in C. elegans can be used in humans without further testing. The C. elegans genome is sequenced and the human genome is not. C. elegans reproduces faster and is easier to work with in the lab.

C. elegans reproduces faster and is easier to work with in the lab.

When Ca++ is released into a muscle fiber cell, muscle contraction is initiated through the following mechanism: Ca++ depolarizes the sarcoplasmic reticulum membrane causing ATP to be released into the myofibril where it can be used to drive the power stroke. Ca++ binds actin, changing its conformation so it can be bound by the myosin head domain. Ca++ binds to troponin, which causes tropomyosin to uncover myosin binding sites on the actin filaments. Ca++ activates the ATPase activity necessary to drive the myosin power stroke.

Ca++ binds to troponin, which causes tropomyosin to uncover myosin binding sites on the actin filaments.

Which of the following is NOT a characteristic of cancer? Cancer cells show reduced dependency on extracellular signaling. Cancer cells have a higher propensity to undergo programmed cell death. Cancer cells display uncontrolled cell division. Cancer cells have the ability to invade healthy tissues. Cancer cells have the ability to migrate to other parts of the body.

Cancer cells have a higher propensity to undergo programmed cell death.

Imagine you identify a mutant that is defective in endocytosis. You examine the mutant by electron microscopy and see that it can still produce clathrin-coated vesicles, but your favorite endocytic protein cargo is not inside them. Which component might you suspect is mutated? Cargo receptor SNARE Dynamin Clathrin

Cargo receptor

Which of the following statements related to cell cycle checkpoint regulation is FALSE? p53 is a transcription factor that induces expression of CKI genes. DNA damage activates protein kinases that phosphorylate p53 and activate it. p53 protein binds to Bax on the mitochondria and activates apoptosis. p21 protein can bind to Cdk/cyclin complexes and inhibit their activity. Caspase activation can trigger cell cycle checkpoints by activating p21.

Caspase activation can trigger cell cycle checkpoints by activating p21.

Which of the following statements about collagen is FALSE? Procollagen is secreted from the cell, then proteolytically cleaved to allow assembly into fibers. Collagen in an animal ECM consists of protein monomers, wound into triple stranded helices, that are then assembled into fibers. Collagen fibers can be rapidly disassembled and reassembled during cell division by phosphorylating their protein subunits. Collagen fibers can be realigned (remodeled) by fibroblast cells.

Collagen fibers can be rapidly disassembled and reassembled during cell division by phosphorylating their protein subunits.

Which of the following statements about cell cycle regulation is NOT true? Cdk requires dimerization with a cyclin for activity. Cdks can be inactivated by phosphorylation. Cdk activity can be blocked by inhibitory proteins called CKIs (Cdk Inhibitors). Cyclins activate Cdks by phosphorylating them. Cyclin protein levels vary according to rates of gene transcription as well as proteolytic degradation.

Cyclins activate Cdks by phosphorylating them.

You have created a mutant yeast strain with defective mitochondria. What effect do you predict this would have on the cells? Decreased ATP production Larger size No change from the wild type Increased ATP production Weak cell walls

Decreased ATP production

In a given organism, exposure to a hormonal signal (e.g. epinephrine) triggers different responses in different tissues, and some tissues show no response at all. Which of the following is NOT a possible explanation for this phenomenon (except in rare exceptions)? Different cell types might contain different genes that control different responses. Different cells might express different signal transduction proteins. Different cell types might express different (or no) receptors for the hormone. Activation of the same effector protein in different cells might cause different responses depending on what other proteins are expressed in the cells.

Different cell types might contain different genes that control different responses

Imagine you identify a mutant that is defective in endocytosis. You examine the mutant by electron microscopy and see that it contains clathrin-coated vesicles budding inward from the plasma membrane, but still attached to the membrane via a narrow neck. Which component might you suspect is mutated? Dynamin SNARE Cargo receptor Clathrin Adaptin

Dynamin

Which statement about reproductive cloning is correct? In artificial twinning, all the embryos are genetically identical to each other but different from the parents. In somatic cell nuclear transfer, a nucleus is removed from a fertilized egg cell and transferred into an enucleated somatic cell from an adult. In somatic cell nuclear transfer, all the embryos are genetically identical to each other but different from the parent donor. In artificial twinning, all the embryos are genetically identical to each other and identical to the parent.

In artificial twinning, all the embryos are genetically identical to each other but different from the parents.

After generation of an action potential in a nerve cell, how does the membrane repolarize again? Inactivation of sodium channels and opening of voltage-gated potassium channels Release of neurotransmitter into the cell Opening of voltage-gated calcium channels Opening of sodium channels and closing of voltage-gated potassium channels

Inactivation of sodium channels and opening of voltage-gated potassium channels

All of the following factors could contribute to the genome instability commonly observed in cancers, EXCEPT which one? decreased propensity to undergo apoptosis. defects in cell cycle checkpoints. increased activity in the Retinoblastoma (Rb) protein. decreased expression/activity of p53 protein.

Increased activity in the Retinoblastoma (Rb) protein.

A particular enzyme is regulated by phosphorylation. If phosphorylation increases its Km by a factor of 3, but does not change its Vmax, what effect does phosphorylation have on the enzyme activity? Activates Has no effect on enzyme activity Inhibits

Inhibits

Which of the following statements is true about endocytosis? COP-coated vesicles internalize material from the plasma membrane It can be used to internalize molecules from the plasma membrane for degradation in lysosomes proteins are transported directly across the plasma membrane into the cytosol through a channel in the membrane

It can be used to internalize molecules from the plasma membrane for degradation in lysosomes

Which type of somatic cell mutation would most likely to give rise to cancer? Gain-of-function mutations in a DNA damage surveillance protein Loss-of-function mutations in a mitogen receptor Loss-of-function mutation in a Cdk Loss-of-function mutation in an activator of apoptosis Gain-of-function mutation in a checkpoint protein

Loss-of-function mutation in an activator of apoptosis

Which of the following statements is true? Malignant cells with gain-of-function mutations in p53 show decreased sensitivity to radiation therapy. Malignant cells with loss-of-function mutations in p53 show increased sensitivity to chemotherapy. Malignant cells with loss-of-function mutations in p53 show increased sensitivity to radiation therapy. Malignant cells with loss-of-function mutations in p53 show decreased sensitivity to radiation therapy.

Malignant cells with loss-of-function mutations in p53 show decreased sensitivity to radiation therapy.

Imagine you are studying the transport of proteins into peroxisomes. You engineer a peroxisomal protein to remove its predicted sorting signal and see that it is now found in the cytosol. This tells you that the sorting signal is: Both necessary and sufficient for targeting to peroxisomes Sufficient for targeting to peroxisomes Necessary for targeting to peroxisomes

Necessary for targeting to peroxisomes

The amino acid side chains on the outside of a transmembrane β-barrel are likely to be: negatively charged hydrophobic positively charged hydrophilic

hydrophobic

You have generated a mutation in a mouse gene that causes a defect in formation of lysosomes. What effect would you predict this will have on the cells? Improper cellular division Problems degrading proteins No change from the wild type Larger size Increased ATP production

Problems degrading proteins

You have created a mutation in a Drosophila melanogaster gene that has a deleterious effect on one of the proteins forming the Golgi apparatus. What effect would you predict this will have on the cells? No change from the wild type Increased ATP production Improper cellular division Larger size Problems secreting proteins

Problems secreting proteins

Lysozyme lowers the activation energy for its reaction by: Phosphorylating its substrate to cause a conformational change Binding its two substrates and orienting them to favor a reaction Putting strain on bonds in the bound substrate molecule Hydrolyzing ATP to make the reaction energetically favorable

Putting strain on bonds in the bound substrate molecule

By what mechanism(s) can an enzyme can lower the activation energy of a reaction? Hydrolyzing ATP to make the reaction energetically favorable Increasing the temperature to make the reaction more likely Hydrolyzing ATP to make the reaction energetically unfavorable Rearrangement of electrons in the substrate

Rearrangement of electrons in the substrate

Imagine you identify a mutant that is defective in endocytosis. You examine the mutant by electron microscopy and see that it contains uncoated vesicles accumulated near the plasma membrane. Which component might you suspect is mutated? Adaptin Clathrin Cargo receptor Dynamin SNARE

SNARE

Which of the following statements about the process of tissue renewal in the gut lining is FALSE? Stem cells rapidly proliferate so daughter cells quickly leave the crypt as a means to minimize the chances of developing a tumor. Cell signaling directs which cells proliferate vs. which cells differentiate. Mutations in transit amplifying cells usually don't matter (unless they block the cells from exiting the crypt). As cells exit the crypt, they stop dividing, differentiate and then are eliminated by apoptosis.

Stem cells rapidly proliferate so daughter cells quickly leave the crypt as a means to minimize the chances of developing a tumor.

Which of the following statements about microtubules is TRUE? Microtubules display the property of "treadmilling" where they tend to assemble at their plus ends and disassemble at their minus ends. Because microtubules are subject to dynamic instability, they are used only for transient structures in a cell. The inherent GTPase activity of tubulin contributes to dynamic instability because polymers of GDP-bound tubulin dimers are less stable than GTP-bound tubulin. Microtubule dynamic instability drives extension and retraction of filipodia.

The inherent GTPase activity of tubulin contributes to dynamic instability because polymers of GDP-bound tubulin dimers are less stable than GTP-bound tubulin.

Which of the following does NOT describe properties of induced pluripotent stem cells? They can potentially circumvent ethical and histoincompatibility issues associated with other types of stem cells. They are produced by expressing a particular combination of transcription factors. They are totipotent and can develop complete embryos. They can be generated from several adult tissues.

They are totipotent and can develop complete embryos.

Which of the following is NOT an example of a function performed by epithelia? They can have secretory functions such as mucus or hormones. They provide cushioning such as in bone joints. Actin networks contract in a coordinated manner to drive morphogenetic movements. They control the transport of solutes into or out of a lumen or organ. They provide protection against pathogens or other environmental factors.

They provide cushioning such as in bone joints.

What advantage is there in transporting a molecule via a transporter rather than an ion channel? Transport through a transporter is faster than by a channel Transport through transporters can be controlled, transport via channels cannot, they are always open Transporters can perform active transport, channel proteins can only perform passive transport Channels are much more specific than transporters

Transporters can perform active transport, channel proteins can only perform passive transport

True or false: smoking is responsible for about 30% of all cancer deaths in the U.S.

True

Which of the following represents the correct sequence of events for a quiescent G0 (G-zero) cell to enter the cell cycle and begin to divide? an initiator caspase activates p21, S-cdk phosphorylates helicase, APC ubiquitylates S-cyclin, cdc25 phosphatase dephosphorylates M-cdk. an oncogenic signal activates MAPK, APC ubiquitylates G2 cyclin, Wee1 kinase phosphorylates M-Cdk, Rb is degraded. an extracellular signal activates G1-cdk, Wee1 kinase phosphorylates Rb, ORCs (origin of replication complexes) get activated, centrosomes duplicate a mitogenic signal activates transcription of G1-cyclin, Rb protein gets phosphorylated and inactivated, the S-cyclin gene is transcribed, helicase gets phosphorylated and activated.

a mitogenic signal activates transcription of G1-cyclin, Rb protein gets phosphorylated and inactivated, the S-cyclin gene is transcribed, helicase gets phosphorylated and activated.

An organoid is: an organ surgically removed from a fetal embryo, that can be transplanted into an adult and grow to adult size. the site within an organ where stem cells reside, allowing the organ to remain healthy by cell and tissue renewal. a structure, formed from stem cells grown in culture, that differentiates cell types in patterns appropriate for tissues of a particular organ. a metastatic tumor that is able to establish in a secondary organ by developing cellular characteristics of that organ, thereby avoiding the body's defenses.

a structure, formed from stem cells grown in culture, that differentiates cell types in patterns appropriate for tissues of a particular organ.

Which of the following statements is true about endocytosis: clathrin-coated vesicles internalize material from the plasma membrane It can be used to internalize molecules from the plasma membrane for degradation in the Golgi proteins are transported directly across the plasma membrane into the cytosol through a channel in the membrane

clathrin-coated vesicles internalize material from the plasma membrane

A yeast mutant is defective in secretion of proteins. If the mutation is in a gene required for transport from the endoplasmic reticulum to Golgi, where would the secretory proteins most likely accumulate? plasma membrane cytosol vacuole endoplasmic reticulum Golgi

endoplasmic reticulum

Intermediate filaments help protect animal tissues from mechanical stress because ____________. filaments in each cell are indirectly connected to the filaments of a neighboring cell through the desmosome, creating a continuous mechanical link between cells. filaments make up the desmosome junctions that connect cells; these junctions are more important than the internal network of filaments for protecting cells against mechanical stress. filaments remain independent of other cytoskeletal elements and keep the mechanical stress away from other cellular components. filaments directly extend from the interior of the cell to the extracellular space and into the next cell, linking one cell to the next, helping to distribute locally applied forces.

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

The amino acid side chains that line an aqueous pore formed by transmembrane α-helices are likely to be: alternating hydrophobic and hydrophilic hydrophobic hydrophilic

hydrophilic

Which of the following statements about metastasis is FALSE? expression of extracellular matrix proteases is required for metastatic cells to cross epithelia to enter or exit blood vessels. changes in cell adhesion properties are involved with a tumor cell becoming metastatic. adhesion between metastatic cells and blood vessel walls helps determine which organs are colonized by secondary tumors metastatic cells invade new sites by inducing angiogenesis so the cells can follow the new blood vessels to a new site.

metastatic cells invade new sites by inducing angiogenesis so the cells can follow the new blood vessels to a new site.

A protein that, upon interaction with an extracellular stimulus, undergoes a conformational change which alters its properties such that a change in cell behavior occurs, is called a: receptor. heterotrimeric G-protein. Ras. effector protein. second messenger.

receptor.

Small molecules, such as cyclic AMP or calcium, that are released or produced inside a cell in response to an external signal, and which regulate cellular activities, are known as: effector proteins. kinases. second messengers. autocrine signals.

second messengers.

For a reaction to occur spontaneously: ∆G must be positive an input of energy is required the reaction must be energetically unfavorable the products must have a lower energy than the reactants

the products must have a lower energy than the reactants

Embryonic stem cells (ESCs) are of interest for research and potential therapeutic applications because: they are not yet expressing major histoincompatibility antigens so they do not elicit tissue rejection responses. they are the only stem cell capable of producing muscle, which is the most common tissue to be injured. they are pluripotent and can therefore be directed to differentiate into many different cell types. they are so readily available from fertility clinics. they can divide indefinitely without the need for any external signals.

they are pluripotent and can therefore be directed to differentiate into many different cell types.

Which events are triggered by the arrival of an action potential at a nerve terminal? voltage-gated calcium channels open, synaptic vesicles fuse with the plasma membrane and neurotransmitter is released sodium ions diffuse into the cell, preventing the signal from being propagated further sodium channels are inactivated, so neurotransmitter cannot be released neurotransmitter receptor is taken up by exocytosis and degraded in the lysosome

voltage-gated calcium channels open, synaptic vesicles fuse with the plasma membrane and neurotransmitter is released