Psio exam 1

The number of mitochondria in a cell is carefully regulated. What process is most likely to increase the number of mitochondria?

Formation of new mitochondria by mitochondrial fission.

Deep down, we are cannibals. Our cells are perpetually devouring themselves, shredding their own complex molecules to pieces and recycling them for new parts. For example, at any point in time the amount of GFAP protein in an astrocyte cell reflects a balance between protein synthesis and degradation. Which of the following best describes this situation?

GFAP expression and degradation are at steady state

The extracellular space around axons generally has which of the following concentrations of ions ( relative to intracellular concentrations ) ?

Low K + , high Na + , high Cl

Mitochondria are capable of protein synthesis. Which of the following statements best describes mitochondrial protein synthesis?

Mitochondria can synthesize new proteins coded by mtDNA. However, they can synthesize only a few of the proteins they require.

Ion gradients are important. The concentration of sodium ions in cytoplasm is low compared to the concentration in extracellular fluid.

Na,K-ATPase pumps sodium ions out of the cell using energy provided by ATP hydrolysis.

Complete the statement The Equilibrium Potential of an ion represents ...

the electrical voltage required to balance the concentration difference of the specific ion across the membrane

The Nernst Equation is used to find ...

the equilibrium potential of an ion.

The lumen (interior) of the endoplasmic reticulum ...

typically has a lower calcium ion concentration than cytoplasm.

Which of the following best defines apoptosis?

Apoptosis is a form of programmed cell death

What is your best estimate for the thickness of a lysosomal membrane?

5 nm

If a change in PNa caused a hyperpolarizing graded potential, did PNa increase or decrease?

PNa decreased

Imagine a hypothetical neuron that is only permeable to K+ ions. If the EXTRAcellular K+ concentration were 10 TIMES GREATER than the INTRAcellular K+ concentration, then the resting membrane potential for this hypothetical cell would be about:

+58 mV.

What is your best estimate of the distance between two side-by-side folds in the cristae of a typical mitochondrion?

100 nm

In a typical plasma membrane the width of lipid bilayer is 5-6 nm. What is your best estimate of the width of the lipid bilayer in a typical endoplasmic reticulum (ER) membrane?

5-6 nm

Which of the following is true regarding the difference between graded and action potentials?

A graded potential's magnitude depends on the power of the stimulus, whereas action potentials are all or nothing.

A graded potential can be hyperpolarizing or depolarizing. Which of these statements is TRUE?

A hyperpolarizing graded potential is inhibitory to generation of an action potential.

Which of the following is the best definition of mitochondrial cristae?

Cristae are folds on the inner membrane of the mitochondrion.

Ca2+-ATPases are integral membrane proteins. They are active transport mechanisms that use the energy derived from ATP hydrolysis to pump calcium ions across the membrane. A specific form of Ca2+-ATPase, ERCA, is located on the endoplasmic reticulum membrane. In which direction does ERCA transport calcium ions?

ERCA transports calcium ions from the cytoplasm into the lumen of the endoplasmic reticulum.

"Proteasomes are involved with various cell processes. They break down excess or worn-out cell parts. They may be used to and destroy invading viruses and bacteria by enveloping them in a lipid membrane structure."

False

Which of the following best defines heteroplasmy?

Heteroplasmy is the presence of more than one mitochondrial DNA (mtDNA) variant within a cell, tissue, or individual.

Most of the time, DNA is wrapped around spool-like proteins that can wind up a stretch of DNA so that the cell cannot make transcripts from it. What are the spool proteins called?

Histones

Why are integral membrane proteins translated at the rough endoplasmic reticulum?

Integral membrane proteins have a hydrophobic region that can only be constructed in the interior of a lipid bilayer.

Angiotensin-converting enzyme 2 (ACE2) plays a key role in the renin-angiotensin system and also serves as a receptor for SARS-CoV-2. Researchers think alternative RNA splicing of ACE2 might generate variants that limit the entry of SARS-CoV-2 into human cells. Which of the following best describes RNA splicing?

RNA splicing involves the removal of certain sequences, referred to as introns, from pre-mRNA and exons are joined together.

Which of the following statements best describes the synthesis of secreted proteins?

Secreted proteins are typically synthesized in the rough endoplasmic reticulum and carried to the Golgi apparatus in vesicles.

In the Goldman equation what is PNa?

Sodium permeability

The SARS-CoV-2 spike (S) protein and its sugars have been the subject of much scientific investigation. S protein, the main focus of SARS-CoV-2 vaccine development, is heavily glycosylated. In fact, it contains 22 N-linked, and at least two O-linked, glycosylation sites. Which of the following statements is most likely to describe this glycosylation process?

The SARS-CoV-2 spike protein is probably glycosylated in both the endoplasmic reticulum and Golgi apparatus of cells in the respiratory tract of an infected subject.

Human samples collected for the SARS-CoV-2 Quantitative PCR test deteriorate quickly unless they are refrigerated. This is because

The assay measures RNA and RNA is unstable.

What is the cellular location of glycolysis?

The cytosol

Which of the following best describes the pH of the lysosomal interior?

The interior of a lysosome generally has a lower pH than cytoplasm.

The process of endocytosis involves the formation of vesicles called endosomes. Which of the following best describes the pH of the endosomal interior?

The interior of an endosome generally had a lower pH than cytoplasm.

Which is true about the difference between graded and action potentials?

The magnitude of a graded potential depends on the magnitude of the stimulus, whereas action potentials are all or none.

Proton gradients occur in mitochondria. Proton gradients also are found between the cytoplasm and the interior of lysosome and endosomes. Which of the following statements is NOT true?

The proton gradient in a mitochondrion is created by an ATPase ion pump.

Endothelin-1 (ET-1) is a potent endogenous vasoconstrictor, mainly secreted by endothelial cells. It acts by binding to an extracellular ligand-binding site on ETA and ETB receptors. Because the ETA and ETB receptors are integral membrane proteins, they are translated at the rough endoplasmic reticulum (ER). Which of the following statements describes the orientation of the receptor polypeptides in the ER membrane?

The receptor polypeptides are orientated with the extracellular ligand-binding site facing the ER lumen (interior).

The race is on to develop treatments for Covid-19. RNA vaccines are the frontrunners. RNA vaccines consist of messenger RNA strands. They are injected intramuscularly, usually within lipid nanoparticles that merge with the patient's cells. Once inside, the mRNA sequence is used by ribosomes to make a protein or parts of a protein. Rather than generating proteins in a manufacturing plant and purifying them, you are getting the subject's muscle cell to do the job and make the protein itself. What is the name of the process when mRNA is used by ribosomes to make a protein?

Translation

Is the following statement TRUE or FALSE ? " The Nernst equation cannot be used to calculate the membrane potential because it tells you only what the equilibrium potential for an individual ion is , not what the summed effect of all ions is on the membrane potential . "

True

Is this true or false: "Synthesis of phospholipids and cholesterol occur in the endoplasmic reticulum."

True

There are several different mechanisms of endocytosis. Some mechanisms are selective, some are not selective. Is clathrin-mediated endocytosis selective?

Yes, clathrin-mediated endocytosis is selective.

When voltage-gated ion channels open, ions move through these channels under the influence of the ...

combined influence of the electrical field of the membrane potential and the concentration gradients of the ions.

Complete the sentence: Human subjects are tested for SARS-CoV-2 by means of a PCR test that quantifies the presence of a particular mRNA in a nasal swab because ...

mRNA is used as a template in the process of translation. Therefore the presence of the mRNA indicates cells in the subject's nasal passage are actively manufacturing SARS-CoV-2 protein.

Complete the statement Depolarization of the resting membrane potential can be brought about by ...

increasing Na + permeability

Depolarization of the resting membrane potential can be brought about by ...

increasing the external K+ concentration.

Human subjects are tested for SARS-CoV-2 by means of a PCR test that quantifies the presence of a particular mRNA in a nasal swab because ...

mRNA is used as a template in the process of translation. Therefore the presence of the mRNA indicates cells in the subject's nasal passage are actively manufacturing SARS-CoV-2 protein.

Which of the following statements makes the most sense?

mtDNA is thought to be evolved from the circular genomes of the bacteria that were incorporated into the early ancestors of today's eukaryotic cells. This explains why mtDNA is circular.

Which statement makes the most sense?

mtDNA is thought to be evolved from the circular genomes of the bacteria that were incorporated into the early ancestors of today's eukaryotic cells. This explains why mtDNA is circular.

Which statement best completes the following sentence? mtDNA contains ...

only a few of genes that mitochondria need.

If you experimentally increase the permeability of an axonal membrane to sodium ions, the equilibrium potential for sodium in the cell will ...

remain unchanged.