Biology quiz questions w6-9

Intermediate filaments help protect animal cells from mechanical stress because filaments remain independent of other cytoskeletal elements and keep the mechanical stress away from other cellular components. in each cell are indirectly connected to the filaments of a neighboring cell through the desmosome, creating a continuous mechanical link between cells. 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. 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.

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

A protein kinase can act as an integrating device in signaling if it catalyzes its own phosphorylation. initiates a phosphorylation cascade involving two or more protein kinases. phosphorylates more than one substrate. is activated by two or more proteins in different signaling pathways.

initiates a phosphorylation cascade involving two or more protein kinases.

The final metabolite produced by glycolysis is acetyl CoA. 3-phosphoglycerate. pyruvate. glyceraldehyde 3-phosphate.

pyruvate.

T/F Animal cells frequently power uptake of nutrients with "potassium" gradients.

sodium

Glycolysis generates more stored energy than it expends. What is the net number of activated carrier molecules produced in this process (number and type of molecules produced minus the number of those molecules used as input)? 6 ATP, 2 NADH 4 ATP, 2 NADH 4 ATP, 4 NADH 2 ATP, 2 NADH

2 ATP, 2 NADH

Water (Links to an external site.) molecules readily form hydrogen bonds with other polar molecules, and when they encounter nonpolar molecules they must form hydrogen-bonding networks with neighboring water (Links to an external site.) molecules. Which of the following molecules will cause a "cage" of water (Links to an external site.) to form? methanol urea 2-methylpropane acetone

2-methylpropane

A non-hydrolysable form of "GTP" could result in highly stabilized actin microfilaments.

ATP

High levels of oxidative metabolism produce high levels of CO2. As you recall, CO2 dissolved in water (Links to an external site.) can produce carbonic acid and lower the pH. Using this fact and your knowledge of the effect of pH on hemoglobin, explain how oxygen delivery is prioritized to actively contracting muscles.

Active muscle produces more CO2 which makes the tissue pH. Lower pH reduces hemoglobin oxygen affinity. In effect, the byproduct if increased metabolism (CO2) promotes more oxygen delivery.

Loss of calmodulin function would render a cell less responsive to changes in cytosolic "diacylglycerol."

Calcium

Explain why defects in plectin proteins cause a much more severe disorder than defects in keratin proteins.

Defects of plectin proteins result in a combination of effects such as which is much more severe than defects in keratin proteins because this defect only leads to skin to have a high vulnerability to injury. This defect of keratin being one of the defects of plectin along with muscular dystrophy and neurodegeneration.

Glycoproteins are not permitted to leave the "Golgi" until they are properly glycosylated.

ER

Which of the following statements about "redox potential" is TRUE? A molecule's redox potential is a measure of the molecule's capacity to pass along electrons to oxygen. Redox potential is a measure of a molecule's capacity to strip electrons from oxygen. For molecules that have a strong tendency to pass along their electrons, the standard redox potential is negative. The transfer of electrons from cytochrome c oxidase to oxygen has a negative redox potential.

For molecules that have a strong tendency to pass along their electrons, the standard redox potential is negative.

How might the structure of lipid bilayers be altered if phospholipid tails were shorter?

If the tails were shorter the bilayer might be reduced in depth and either the proteins incorporated within the bilayer will be shorter or they may stick out dependent on it is hydrophobic or hyrdophilic. Another possibility would be that less unsaturated lipids within the bilayer causing the membrane to be more fluid.

Inactivating mutations in the Ras GTPase domain can lead to uncontrolled cell proliferation and cancer. Explain the mechanistic relationship between the mutation and increased proliferation.

Inactivating mutations of Ras GTPase wouldn't allow for Things to turn on and off as needed if GTP is bound to Ras the pathway would be turned on always allowing for constant growth and division of the cell without stopping for checkpoints or allowing for apoptosis if needed.

Which of the following statements describes the mitochondrial matrix? It is permeable to molecules with molecular mass as high as 5000 daltons. It contains proteins that are released during apoptosis. It contains transporters for ATP molecules. It contains enzymes required for the oxidation of fatty acids.

It contains enzymes required for the oxidation of fatty acids.

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? Nuclear transport receptors would be unable to bind cargo. Nuclear transport receptors would interact irreversibly with the nuclear pore fibrils. Nuclear transport receptors would be unable to release their cargo in the nucleus. Nuclear transport receptors would be unable to enter the nucleus.

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

Inactivating mutations to "Rac" would most strongly impair contractile ring formation.

RhoA

Dinitrophenol is a proton ionophore that has been used (unwisely) as a weight-loss aid. The effective and lethal doses of this drug are fairly close, and individuals that have died from overdosing on dinitrophenol often had body temperatures in excess of 40o C. What happened in the mitochondria of these individuals?

The mitochondria of these individuals were being over worked to the point of using up all resources and constantly expending energy. the reason we know that the mitochondria was continually processing at an unhealthy level was the fact that body temperatures were raised to abnormal levels at resting because the mitochondria leaks heat from uncoupling agents allowing protons to bypass ATP synthase.

How is virus entry into a cell similar to receptor-mediated endocytosis? How is it different?

Virus entry is similar to receptor-mediated endocytosis by capsids having that ability to interact with the plasma membrane to "virus receptors" similar to normal endocytosis. They are different by viruses having that ability to escape the clathrin-coated vesicles.

Explain the paradox of observed cancer rates among animals of different sizes and what it suggests about different sized animals' ability to regulate the cell cycle.

You would expect to see rates of cancer to increase with size and age, but as it turns out there are more selection to suppress cancer via the cell cycle as animals increase size and age. So instead of the increase we actually see a constant rate between different animals of about 11-25% of a lifetime risk.

Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found? a sodium channel a calcium channel an aquaporin a proton channel

an aquaporin

Protein kinase C activation depends on an increase in cytosolic "cAMP."

calcium

The flow rate of solutes through a "transporter" is theoretically limitless.

channel

During nervous-system development in Drosophila, the membrane-bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in __________ signaling. paracrine contact-dependent endocrine neuronal

contact-dependent

Which of the following substances is most commonly used to help purify a membrane protein? detergent sucrose ethanol high saltLinks to an external site. solutio

detergent

Uncoupling agents turn the energy of the mitochondrial proton gradient into "ATP."

heat

Lamellipodia are apparent at the "lagging" edge of a migrating cell.

leading

Gluconeogenesis performed by "muscle" cells ensures a steady supply of glucose for the rest of the body.

liver

T/F "Integral" membrane proteins associate with membranes via non-covalent interactions with membrane-embedded molecules.

peripheral

Kinesins and dyneins derive their energy from GTP hydrolysis. move along both microtubules and actin filaments. have tails that bind to the filaments. often move in opposite directions to each other.

often move in opposite directions to each other.

"Negative" feedback ensures that once M-Cdk is permitted to function, activity is quickly maximized.

positive

Ca2+-pumps in the plasma membrane and endoplasmic reticulum are important for maintaining osmotic balance. providing enzymes in the endoplasmic reticulum with Ca2+ ions that are necessary for their catalytic activity. maintaining a negative membrane potential. preventing Ca2+ from altering the activity of molecules in the cytosol.

preventing Ca2+ from altering the activity of molecules in the cytosol.

Sister chromatid separation occurs because __________ are destroyed by the APC/C. condensins kinetochores cohesins securins

secruins

Explain why sodium-solute symporters would be a more efficient approach to nutrient uptake than potassium-solute antiporters.

sodium-solute symporters would be more efficient because there would be one direction of ion flow and no back flow where as the potassium-solute antiporters would have back flow decreasing its efficiency.

Progression through the cell cycle requires a cyclin to bind to a Cdk because cyclin binding inhibits Cdk activity until the appropriate time in the cell cycle. the cyclins are the molecules with the enzymatic activity in the complex. the binding of a cyclin to Cdk is required for Cdk enzymatic activity. without cyclin binding, a cell-cycle checkpoint will be activated.

the binding of a cyclin to Cdk is required for Cdk enzymatic activity.

Proteins that are fully translated in the cytosol do not end up in the mitochondria. transport vesicles. the interior of the nucleus. the cytosol.

transport vesicles.

"NADPH" is the activated carrier produced by photosystem I in the chloroplasts.

true

Investment of some ATP can produce "oxaloacetate" from pyruvate in instances where citric acid cycle intermediates are low.

true

Stop-transfer sequences in ER-synthesized proteins are rich in "hydrophobic" amino acids.

true

T/F "Diffusion barriers" can divide a cell's membrane into separate domains.

true