Quiz 3

Question 1

Which of these is true for lipid molecules that move from one leaflet to another?

Answer 1

The process requires energy and the flippase enzyme.

Question 2

The rate of diffusion of a molecule across a membrane will be inversely proportional to:

Answer 2

Thickness of the membrane.

Question 3

By which process do oxygen molecules cross membranes?

Answer 3

Diffusion across the lipid bilayer.

Question 4

If there is a rise in sodium concentration outside of a cell with open chloride channels, in what direction are the chloride ions and water expected to move across the plasma membrane?

Answer 4

Both chloride ions and water will move out of the cell.

Question 5

The inhibition of the enzyme phosphofructo kinase-1 by citrate is an example of

Answer 5

allosteric regulation.

Question 6

uses an organic molecule as a final electron acceptor.

Answer 6

fermentation

Question 7

What is the purpose of CoA?

Answer 7

To form an unstable molecule Acetyl-CoA that readily donates its 2C-acetyl group to oxaloacetate.

Question 8

Which of these produces carbon dioxide?

Answer 8

TCA cycle

Question 9

_____________ is a small vesicle that is derived from fragmented ER produced when cells are homogenized.

Answer 9

Microsome

Question 10

The Sec61 complex forms _____________ within the ER membrane.

Answer 10

translocon

Question 11

Precursor proteins destined for this organelle retain their targeting signal after transport across the organelle’s two membranes:

Answer 11

nucleus

Question 12

Posttranslational glycosylation of proteins is inhibited specifically by:

Answer 12

tunicamycin.

Question 13

Perioxisomal matrix proteins

Answer 13

undergo post-translational import into perioxisomes

Question 14

Transmembrane proteins of which of these organelles is synthesized on cytosolic ribosomes:

Answer 14

peroxisome

Question 15

The _________ protein forms general import pore which is a large passive channel through the outer mitochondrial membrane.

Answer 15

Tom 40

Question 16

Plastocyanin is a thylakoid lumen protein. Consider a scenario wherein, through genetic engineering, you replace the first 40 resides of Plastocyanin with a stretch of 40 Alanines. What can you predict about targeting or localization of this newly synthesized mutated protein?1

Answer 16

It will remain in the cytoplasm

Question 17

Which of the following amino acids are most frequently phosphorylated by protein kinases in the cytoplasm during signal transduction?

Answer 17

Tyrosine, serine and threonine

Question 18

Calcium ion

Answer 18

concentration in the cytosol is increased by activation of phospholipase C.
concentration in the cytosol is increased by activation of membrane calcium channels.
release from the endoplasmic reticulum may trigger influx of calcium ions from the extracellular fluid.

Question 19

What type of signaling occurs when insulin is secreted from the pancreas and acts on muscle cells to increase glucose uptake?

Answer 19

Endocrine signaling

Question 20

Which of the following statements is true of signal molecules?

Answer 20

Protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors.

Question 21

A ligand for a membrane-bound receptor is chemically linked to beads that form an affinity chromatography column. When a solubilized preparation of membrane proteins is passed over this column, only the receptor binds to the beads. Later, an excess of the ligand is poured through the column after the receptor binding step. What do you expect will occur?

Answer 21

The ligand will cause the receptor to be displaced from the beads and eluted out.

Question 22

Which of the following are common means by which binding of a chemical messenger to a cell’s receptor brings about an intracellular response?

Answer 22

Opening or closing of specific ionic channels in the plasma membrane
Activation of an intracellular second-messenger system
Promoting or inhibiting the transcription of genes that code for the synthesis of cellular proteins

Question 23

Activation of a receptor that is coupled by G proteins to adenylyl cyclase

Answer 23

may increase the intracellular concentration of cyclic AMP.
may decrease the intracellular concentration of cyclic AMP.
may result in stimulation or inhibition of DNA transcription.

Question 24

Activation of a receptor by a chemical messenger

Answer 24

occurs when the messenger binds to the ligand-binding site of the receptor
is the first step leading to the ultimate response of a cell to the messenger.
requires a change in receptor conformation.

Question 25

Oxytocin is a peptide hormone that causes the smooth muscle of the uterus to contract, but it has no effect on the smooth muscle cells of the small intestine. This difference in responsiveness exists because

Answer 25

uterine smooth muscle cells contain specific receptors for oxytocin

Question 26

Amplification during a second messenger cascade is beneficial because amplification

Answer 26

allows small amounts of hormones to produce large responses in target cells.

Question 27

Nuclear pore complex is made up of multiple copies of some 30 different proteins called ______________.

Answer 27

nucleoporin

Question 28

TCA cycle occurs in the ______________ region of the mitochondria.

Answer 28

matrix

Question 29

Chemicals such as DNP uncouple ______________________ from electron transport.

Answer 29

oxidative phosphorylation

Question 30

In the technique of _______________, cell surface molecules are labeled with a fluorescent tag and then a portion of them are bleached with a laser beam followed by quantification of the lateral movement of proteins and lipids within the membrane.

Answer 30

Florescence Recovery After Photobleaching

FRAP

Question 31

The anaerobic catabolism of glucose called _________________ is the basis of beer and wine production.

Answer 31

fermentation