BSC 300 Exam 3

Which coated vesicles move materials in an anterograde direction from the ER to the ERGIC and the Golgi complex?

COPII-coated vesciles

Which of the following is a second messenger that has been found in eukaryotic cells?

Ca2+ ions, cyclic AMP, phosphoinositides, and inositol triphosphate

What mediates the interaction between membrane proteins and the COPII-coat?

ER export signals in the cytosolic tails of integral ER membrane proteins

Which of the following is (are) not characteristics of the pathways activated by second messengers?

Each protein in the pathway typically acts by altering the conformation of the pervious (upstream) protein in the series, an event that activated or inhibits the protein

GTP-binding proteins are also known as

G proteins

The interaction between the membranes of vesicles and their target compartment is mediated by which protein below?

SNAREs

What GTP-binding protein plays a regulatory role in the formation and disassembly of the COPII coat?

Sar1

What appears to be the purpose of molecular chaperones like BiP and calnexin?

They bind to unfolded and misfolded proteins and help them regain their native structure

Which of the following is associated with cilia?

a 9 + 2 pattern and microtubules

Vesicles that moves through the Golgi complex from the cis-cisternae to the trans-cisternae are said to move in a(n) direction.

anterograde

At which site do most of the signals that regulate the activities in which a cell is engaged originate?

at the cell surface

How are G proteins held at the plasma membrane?

by covalent interactions with lipid chains attached to the α- and y-subunits

How does Viagra enhance erectile function of the penis?

by inhibiting cGMP phosphodiesterase

What is the name of a calcium-binding protein that acts in conjunction with calcium to bring about the responses associated with cytoplasmic rises in calcium ion concentrations?

calmodulin

Lysosomal enzymes are transported from the TGN in vesicles coated with what protein?

clathrin

What word describes the synthesis and section of a substance from the cell in a continual, unregulated manner?

constitutive

What are the two sites within a cell at which protein synthesis is generally thought to occur?

cytosolic surface of RER and free ribosomes

Cellular microfilaments are characterized by the coexistence of randomly growing and shortening filaments, a process called

dynamic instability

Once the kinase domain of receptor protein-tyrosine kinase has been activated, what does the activated receptor protein-tyrosine kinase do?

each receptor subunit phosphorylates its partner on tyrosine residues found in regions adjacent to kinase domain

Along which pathway do materials or the membrane surface move into the cell from the outside to cytoplasmic compartments?

endocytic pathways

In what form do animal cells store glucose?

glycogen

What is the direct source of energy that powers molecular motors?

hydrolysis of ATP

What is the direct result of the action of glucagon and/or epinephrine release?

increase blood glucose levels

What determines the specificity of vesicle fusion to a target membrane?

interactions between specific combinations of interacting proteins, including tethering proteins, Rabs, and SNAREs assembles at the site in the cell

Ephinephrine

is a small molecule that is derived from the amino acid and tyrosine

To what does cAMP bind once it is made by adenylyl cyclase in response to glucagon and/or epinephrine?

it binds to the allosteric site on the regulatory subunits of protein kinase A

Which of the following molecular motors is associated with microtubules?

kinesis and dyneins

Which cell surface receptors conduct a flow of ions across the plasma membrane when bound to ligand?

ligand-gated channels

What are the recognition signals for lysosomal enzymes that allow them to be localized correctly in lysosomes?

lysosomal enzymes possess phosphorylated mannose residues on N-linked carbohydrate chains

Which type of cytoskeletal element is described as a solid structure composed of actin subunits?

microfilaments

The endomembrane system when homogenized is broken up into vesicles, which are heterogeneous but similar in size. These vesicles can be purified and after purification often retain their biological activity. They are collectively referred to as

microsomes

Which type of cytoskeleton element in characterized as a hollow, rigid cylindrical tube with walls composed of tubulin subunits?

microtubules

Which of the following serve as tracks for molecular motors?

microtubules and microfilaments

What motor is associated with microfilaments?

myosin

The slower phase of microtubule assembly in which a small portion of the microtubule is initially formed is called what?

nucleation

Genes that enable viruses to transform normal cells into tumor cells are called _________.

oncogenes

What enzyme below terminates the response to cAMP through the destruction of cAMP molecules present in the cell?

phosphodiesterase

Which enzymes hydrolyze specific ester bonds that connect the different building blocks that make up a phospholipid molecule?

phospholipases

Arrestin binding to the GPCRs

prevents further activation of additional G proteins

What enzyme does diacylglycerol (DAG) recruit and activate?

protein kinase C

What is the intermediate results once most receptor protein-tyrosine kinase bind to their ligand?

receptor dimerization

How are integral membrane proteins thought to enter the lipid bilayer?

the aqueous translocon channel appears to have a gate that continuously opens and closes, giving each nascent polypeptide segment a chance to partition itself into the lipid bilaye's hydrophobic core.

How is signaling by an activated Ga subunit terminated?

the bound GTP is hydrolyzed to GDP

What happens if the UPR is unsuccessful in relieving the stressful conditions in the cell?

the cell-death pathway is triggered

What happens to the cell if the receptors are degraded once they are internalized?

the cells lose, at least temporarily, sensitivity for the ligand in question

How do protein coats select the contents of the vesicles they help to form?

the costs have a specific affinity for the cytosolic tails of integral membrane

On what part of the receptor protein-tyrosine kinase is the protein kinase activity located?

the cytoplasmic domain

What happens to protein kinase A once cAMP binds to it?

the regulatory subunits dissociate from the catalytic subunits, activating the enzyme

Why do tumor cells die after exposure to drugs that either disrupt or stabilize the structure of microtubules?

the tumor cells attempt to complete cell division in the absence of a functional spindle, killing the cells.

The accumulation of misfolded proteins in the ER is a potentially lethal situation and thus causes the triggering of what processes?

the unfolded protein response (UPR)

What happened to COPI-coated vesicles within the cell when the cell was treated with GTP analogues that could not be hydrolyzed?

they accumulated in the cytoplasm

What are steroid receptors generally located and where do they bind the steroid hormone once it enters the cell?

they are located and bind the steroids in the cytoplasm

What is one problem created by the detoxifying of the SER?

they can cause a compound to be converted into a carcinogen

Which protein fits securely into the grooves between two thin filament actin chains?

tropomyosin

What globular protein complex contacts both the actin and tropomyosin components of the thin filament?

troponin

What are the two functional categories of SNAREs?

v-SNAREs and t-SNAREs

How do Rabs appear to associate with membranes?

via a lipid anchor