Molec cell test 3 iclickers

Which mutation would reduce the amount of Ca2+ released from the ER to the cytosol? a) a mutant PIP2 that cannot be hydrolyzed b) a mutant beta/gamme G protein complex c) a mutant DAG d) a mutant CaM kinase

a) A mutant PIP2 that cannot be hydrolyzed

When acetylcholine binds to a GPCR on heart muscle, the activated receptor stimulates a G protein, which opens a k+ channel in the plasma membrane. Which of the following would enhance this effect of the acetylcholine? a) addition of a high concentration of a non-hydrolyzable analog GTP b) addition of a drug that prevents the alpha subunit from exchanging GDP for GTP c) mutations in the acetylcholine receptor that weaken the interactions between the receptor and acetylcholine d) mutations in the acetylcholine receptor that weaken the interaction between the receptor and the G protein

a) addition of a high concentration of a non-hydrolyzable analog of GTP

Which statement about secretion is true? a) the membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents into the cells exterior b) vesicles for regulated exocytosis will not bud off the trans Golgi network until the appropriate signal has been received from the cell c) the signal sequences of proteins destined for constitutive exocytosis ensure their packaging into the correct vesicles d) proteins destines for the constitutive exocytosis accumulate in the trans Golgi network until a signal is received

a) the membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents into the cells exterior

Which if the following statements is true about the smooth endoplasmic reticulum? a) it is associated with ribosomal complexes b) is its the site of cholesterol synthesis c) it is where proteins are synthesized and processed d) disulfide bond formation occurs in the smooth ER e) lipids and proteins are glycosylated in the smooth ER

b) It is the site of cholesterol synthesis

Which of the following statement is true? a) MAP kinase is important for phosphorylating MAP kinase kinase b) PI 3-kinase phosphorylates an inositol phospholipid component of the plasma membrane c) Ras become activated when an RTK phosphorylates its bound GDP to create GTP d) STAT proteins phosphorylate JAK proteins, which then enter the nucleus and activate gene transcription

b) PI 3-kinase phosphorylates an inositol phospholipid component of the plasma membrane.

The action of neurotransmitters can be regulated in any of the ways below, except: a) Enzymatic degradation of neurotransmitters. b) Re-uptake by the post-synaptic membrane. c) Modulation of the post-synaptic receptors. d) Balance between excitatory and inhibitory neurotransmitters. e) All of the above

b) Re-uptake by the post-synaptic membrane.

Where does this dehydration synthesis in the formation of a peptide bond occur? a) cytosol b) ribosome c) nucleus d) mitochondira e) stroma

b) Ribosome

All of the proteins below should be retained by the ER instead of being sent to the Golgi, except a) SRP receptor b) SRP c) translocation channel d) signal peptidase e) hormone receptor

b) SRP / e) hormone receptor

The growth factor RGF stimulates proliferation of cultured rat cells. It is bound by a receptor tyrosine kinase called RGFR. Which of the following types of alteration to RGFR. Which of the following types of alteration to RGFR would be most likely to prevent receptor dimerization? a) a mutation that increases the affinity of RGFR for RGF b) a mutation that prevents RGFR from binding to RGF c) changing the tyrosine that are normally phosphorylated on RGFR dimerization to alanine

b) a mutation that prevents RGFR from binding to RGF.

Which molecule has the most free energy? a) tRNA3 b) tRNA3-AA3 c) AA3-AA4 d)AA4

b) tRNA3-AA3

Both excitatory and inhibitory neurons from junctions with muscles. By what mechanism do inhibitory neurotransmitters prevent the post synaptic cell from firing an action potential?

by opening Cl- channels

Your friend works in a biotechnology company and has discovered a drug that blocks the ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport? a) nuclear transport receptors would be unable to bind cargo b) nuclear transport receptors would be unable to enter the nucleus c) nuclear transport receptors would be unable to release their cargo in the nucleus d) nuclear transport receptors would interact irreversibly with the nuclear power fibrils

c) Nuclear transport receptors would be unable to release their cargo in the nucleus

In the chloroplast, the thylakoid space is more acidic than the intermembrane space during photosynthesis. Why? a) there is an increase in H+ due to the ATP synthase activity b) ferrodoxin converts NADP+ to NADPH c) the cytochrome b-f complex pumps electrons into the lumen of the thylakoid space d) the cytochrome b-f complex pumps protons into the thylakoid space e) none of the above

c) The cytochrome b-f complex pumps protons into the thylakoid space.

What happens when a cell-surface receptor activates a G protein? a) the beta subunit exchanges its bound GDP for GTP b) the GDP bound to the alpha subunit is phosphorylated to form bound GTP c) the alpha subunit exchanges its bound GDP for GTP d) it activates the alpha subunit and inactivated the beta/gamma complex

c) the subunit exchanges its bound GDP for GTP

How would you order the different types of cell signaling from the type in which the signal molecule travels the shortest distance to the type in which the signal molecule travels the greatest distance?

cell-cell, synaptic, paracrine, endocrine

If a lysosome breaks, what protects the rest of the cell from the released lysosomal enzymes?

cytosolic pH

Which could be the activated intermediate in the dehydration synthesis forming a phosphodiester bond? a) Pi b) AMP c) ADP d) ATP

d) ATP

All are examples of proteins that are transported into the nucleus through nuclear pores except: a) DNA and RNA polymerases b) transcription factors c) chromatin assembly proteins d) ATP synthase e) lamins

d) ATP synthase

Akt promotes the survival of many cells. It is activated by an intracellular signaling pathway that is triggered by an RKT that activates PI 3-kinase. Which of the following statements is false? a) in the presence of a survival signal, Akt localizes to the plasma membrane by binding to PIP3 b) in the absence of the survival signal, Bad inhibits the cell death inhibitor protein Bcl2 c) in the presence of the survival signal, the cell death inhibitory protein Bcl2 is active d) In the absence of survival signal, Bad is phosphorylated

d) In the absence of survival signal, Bad is phosphorylated.

Which of the following statements is true for G-protein-coupled receptors? a) the receptor and catalytic functions are present in a protein in the membrane b) the signal binds to the receptor, activating an enzyme protein that activates G protein c) once the signal binds to the receptor, the G protein is activated and send a message outside of the cell d) the signal binds to the receptor, activating a cytoplasmic messenger (G protein) that activates an enzymatic target cell

d) The signal binds to the receptor activating a cytoplasmic messenger (G protein) that activates an enzymatic target.

Adrenaline stimulates glycogen breakdown in skeletal muscle cells by ultimately activating glycogen phosphorylase. Consider skeletal muscle cells which have a constitutively active mutant form of PKA (=remains constantly ON). Which of the following is false? a) this would lead to a decrease in the amount of unphosphorylated phosphorylase kinase b) this would not increase the affinity for adrenaline for the receptor c) this would lead to an excess in the amount of glucose available d) this would lead to an excess in the amount of glycogen available

d) This would lead to an excess in the amount of glycogen available

You are interested in Fuzzy, a soluble protein that functions within the ER lumen. Given that information, which of the following statements must be true? a) fuzzy has a C-terminal signal sequence that binds to SRP b) only one ribosome can be bound to the mRNA encoding fuzzy during translation c) fuzzy must contain a hydrophobic stop-transfer sequence d) once the signal sequences from fuzzy has been cleaved, the signal peptide remains in the ER membrane while fuzzy is released

d) once the signal sequences from fuzzy has been cleaved, the signal peptide remains in the ER membrane while fuzzy is released

Action potentials are usually mediated by voltage-gated Ca2+ channels. (true/false)

false

Heart muscle cells, salivary gland cells, and skeletal muscle cells all express an acetylcholine receptor that belongs to that transmitter-gated ion channel family. (true/false)

false

How is the action of dopamine regulated in response to excessive stimulation due to the presence of cocaine?

modulation of the post-synaptic receptors

Where do you find an electron to give to the original low-energy electron donor (the first one in the row?)

take a low energy electron from water

In the light reactions of photosynthesis, a proton gradient is generated which drives ATP synthesis. Where do protons become concentrated in the chloroplast?

thylakoid space

Ribulose 1,5-bisphosphate is similar to oxaloacetate in the citric acid cycle in that they are both regenerated at the end of their respective cycles. (true/false)

true