BIO211 Exam 2

Bacteria are approximately _____ in diameter; eukaryotic cells are typically at least _____ times this size.

1µm; 10x

In the free energy diagram for a reaction above, the activation energy is:

A-B(value of A minus value of B)

The endosymbiotic theory explains the evolution of:

All Eukaryotes

Which of the following is NOT an ATPase?

All of the above are ATPases

Some neurodegenerative diseases appear to be caused in part by disordered vesicle transport along axons. Imagine you discover a case in which transport of vesicles from the cell membrane back to the Golgi complex is specifically impaired. Which protein(s) is/are likely affected?

Dynein

Is the reaction in the previous question exergonic or endergonic?

Endergonic

Which of the following is an advantage of multicellularity?

Greater mobility

Which of the following is a DISADVANTAGE of endocrine signaling?

It is relatively slow.

Differential centrifugation separates particles based on _______ by applying different _______.

Mass; Spin speeds

Which of the following is found in eukaryotes BUT NOT in bacteria?

Membrane-bound organelles

What do Eukaryotes have that bacteria do not?

Membrane-enclosedorganelles

Which of these pathways happen in the mitochodria in eukaryotes

The PDH, Krebs cycle, electron transfer system

True or False: The concentration of Ca++ inside the cell is higher than it is outside.

false

What is the second messenger in the receptor tyrosine kinase signaling pathway?

none of the above

What do microtubules and actin have in common?

they are both enzymes

True (A) or False (B): If you treated a cell like a pancreatic acinar cell with a compound that causes holes to form in the membranes of peroxisomes, highly reactive or toxic compounds would leak out, potentially causing damage to biological molecules in the cytoplasm.

true

True (A) or False (B): The fluid mosaic model states in part that proteins can diffuse laterally in the membrane.

true

True (A) or False (B): True (A) or False (B): If you treated pancreatic acinar cells with a compound that causes smooth ER membranes to become permeable, Ca++ would leak out into the cytoplasm causing digestive enzymes to be secreted.

true

What percentage by mass of the membrane fraction would you expect to be protein? (assume these are typical cells)

50%

During glycolysis the compound Glucose-6-phosphate (G6P) is converted to its isomer Fructose-6- phosphate (F6P). If the standard equilibrium concentrations are: [G6P] = 1.63 M, and [F6P] = 0.37 M, what are Keq' and DG°' for this reaction? Glucose-6-P ó Fructose-6-P

<1(Keq');>0(DG°')

Consider the reaction: A <=> B. Under standard conditions at equiliubrium, the concentrations of the compounds are [A] = 0.1 M, and [B] = 1.1 M. Keq' for this reaction is ____ and ∆G°' is _____. (You do not need a calculator for this.)

> 1; < 0

In 60 words or fewer, explain the similarities and differences between the three motor proteins.

All motor proteins interact with the cytoskeleton and require ATP. Kinesin and dynein are both microtubule motors, while myosin is an actin motor. Kinesin and dynein are mainly used for transport of stuff, while myosin is used for contraction. Both kinesin and myosin are +-end directed, while dynein is minus-end directed.

Activation of the enzyme Phospholipase C in question 19 is an example of:

Allosteric activation

For the reaction network shown below, imagine that both compounds E and H are useful to the cell, but that the concentration of E must not drop below a certain threshold concentration, let's say 0.1 mM. What is the best way to regulate the pathway to ensure that production of E is prioritized, but that the cell produces H as long as E is at or above its threshold concentration? (20- word limit) (SEE Practice exam Q44)

Allosteric activation of enzyme E5 by E.

In 60 words or fewer, describe how actin polymerization works.

An actin monomer binds to ATP becoming sticky and therefore sticks (binds) to the plus end of an existing actin filament (or to another ATP-bound actin monomer). Eventually, actin catalyzes hydrolysis of the ATP to which it's bound and become less sticky, and therefore eventually unbinds from the minus end of the filament.

Which of the following IS CONSISTENT with or TRUE regarding the endosymbiotic theory for the origins of mitochondria and chloroplasts?

An anaerobic cell engulfed an aerobic bacterium.

The ancestor to all Eukaryotes was likely a/an ______ that ingested but did not digest a/an _____ .

Anaerobic Archaeum; Aerobic bacterium

If you were attempting to identify natural product inhibitors of kinesin activity, which of the following would be a good assay for screening them?

Anterograde transport in cells

Which adaptation specific to becoming multicellular compensates for the destabilizing effect of increased size? (Think carefully about answer choices!)

Both ECM and tight junctions

Consuming very large amounts of certain foods/drinks can affect the digestive system in profound ways. Which of the following would LEAST likely cause some sort of osmotic shock to your stomach and intestinal cells if you consumed a very large amount of it in a short period of time?

Butter

In the free energy diagram for a reaction at right, DG is:

C-B

Which of the following statements is true? A.)Decreasing entropy requires energy. B.)Entropy decreases when energy is converted from one form to another. C.)IfDH<0, the reaction is favorable. D.)A spontaneous reaction is always fast.

Decreasing entropy requires energy.

If you used Pulse-Chase to follow the path of a protein after ENDOCYTOSIS, what organelle most likely corresponds to X in the graph at right?

Endosome

Growth factors binding to their receptor tyrosine kinases on the surfaces of cells is similar to epinephrine signaling in that:

Enzymes are activated through phosphorylation

Which of the following is/are NOT an enzyme?

Epinephrine

One of the main differences between growth factor signaling (receptor tyrosine kinase receptors) and epinephrine signaling (G-protein coupled receptors) is that:

Epinephrine signaling is more likely to have a short-term, reversible effect.

Osmosis occurs because of the universe's tendency to:

Equilibrate solute concentrations

The cytoskeleton is an adaptation specific to:

Eukaryotes

Oligosaccharides, which attract water, provide cushioning in:__________________.

Extracellular matrix

Soon after eating, how is glucose transported into your cells?

Facilitated diffusion

Which of the following is/are required in order for an endosome to be transported from the plasma membrane to the Golgi complex? (Select all that apply!)

GTP Microtubules ATP dynein

Which of these pathways happen in the cytoplasm in eukaryotes

Glycolysis

Many vascular smooth muscle (i.e. blood vessel) cells contract during the fight or flight response. This is because the receptors on those cells activatethe alpha subunit of a G-protein through GTP-GDPexchange similar to the mechanism in liver cells. Ga:GTP then binds to the membrane-bound enzyme Phospholipase C (PLC), inducing a conformational change and thereby activation. PLC then catalyzes the hydrolysis of a membrane phospholipid PIP2 to produce the lipid DAG, which stays in the membrane, and the molecule IP3, which diffuses to the smooth ER to bind Ca++ channels, which causes them to open. The resulting Ca++ influx stimulates contraction. The second messenger in this pathway is:

IP3

Something that is likely to decrease a smooth muscle cell's response to epinephrine is: (see previous question)

Increased G-alpha GTPase activity.

In 40 words or fewer, describe one characteristic of multicellularity that is both an advantage and a disadvantage. Include in your explanation, both why it is advantageous and why it is disadvantageous.

Increased size increases the potential mobility, strength, power, reach, among other things, of an organism. It is also destabilizing and makes nutrient absorption and waste excretion, among other things, more difficult.

ras, a small GTPase, hydrolyzes GTP slowly on its own, but its enzymatic activity is increased significantly in the presence of GTPase activating proteins (GAPs). Imagine you discovered a novel mutation that prevents GAP from binding to ras. This mutation would have the effect of:

Increasing cell proliferation

What happens to GTP in response to epinephrine binding to its receptor on liver cells?

It binds to G-alpha

Which of the following statements is correct regarding the activation energy of a reaction?

It determines whether a reaction is likely to need a catalyst in order to take place.

For solutes that cannot diffuse through the cell membrane, water moves across the membrane from a region of ______ solute concentrations to a region of ______ solute concentration.

Low to high

Which of the following is/are found in eukaryotes but not bacteria?

Mitochondria

Liver cells respond to epinephrine by: Producing cAMP. A.)Increasing the activity of Protein Kinase A. B.)Increasing the activity of glycogen phosphorylase. C.)All of the above D.)None of the above

None of the above

Shown in the plot at right are the data from two fluorescence recovery after photobleaching (FRAP) experiments. Which of the following could explain the difference between the data? A.)The cell indicated by the solid line was assayed at a lower temperature than the cell indicated by the dashed line. B.)The phospholipids in the membrane of the cell indicated by the solid line has more saturated fatty acids than the cell indicated by the dashed line. C.)The phospholipids in the membrane of the cell indicated by the solid line has longer fatty acid chains than the cell indicated by the dashed line. D.)None of the above

None of the above

What do bacteria have that Eukaryotes do not?

Peptidoglycan

What is the identity of a small, spherical organelle that contains such high concentrations of detoxifying enzymes that the protein forms crystals inside the organelle? (shown below)

Peroxisomes

In the original Pulse-Chase experiment of Palade and colleagues, what was does the radioactivity (% or # of grains on the y axis) represent?

Proteins

In the original Pulse-Chase experiment of Palade and colleagues, what can we conclude from the fact that radioactivity in the Golgi complex is initially very low, increases to its highest levels in 15 minutes, and then the radioactivity in Golgi decreases again to near zero by two hours?

Proteins are not made in the Golgi complex, but are transported in after they are synthesized and then eventually exit.

In the graph at right from the original Pulse-Chase experiment, trace B corresponds to:

Rough ER

Pancreatic acinar cells were selected for the original original Pulse-Chase experiment of Dr. Palade and his colleagues because almost all of the proteins they produce are:

Secreted

In 60 words or fewer, explain how a protein destined to be secreted gets from the Golgi complex to the plasma membrane, including how it knows when it's time to be secreted.

The protein is packaged into a vesicle that buds off the Golgi complex. Kinesin on the vesicle binds to a microtubule and transports the vesicle to the + end of the microtubule. If Ca++ levels increase in the cytoplasm, the vesicle fuses with the plasma membrane and the protein is release to the outside world.

Cellular responses to steroid hormone signaling tend to be irreversible (or less reversible than other types of responses) because:

Their cellular responses include gene transcription.

A major function of the epithelium in animals is to prevent entry of pathogens and toxins from the environment. Which of the following is common to all epithelial cells?

They are held together by tight junctions.

Which of the following is a nearly-impermeable boundary between an organism and its environment, acting as the "glue" that holds epithelial cells together?

Tight junctions

A compound that specifically inhibits the activity of the Na+/K+ ATPase would most likely prevent which of the following?

Transport of glucose into cells when blood glucose levels are low.

The Na+/K+ ATPase transports Na+ up its concentration gradient and K + ______ its concentration gradient. This is an example of ______ .

Up; Direct active transport

Which of the following statements is NOT CONSISTENT with Cell Theory?

Viruses are living organisms.

Which of the following mechanisms for enzyme regulation is NEVER reversible?

Zymogen activation

Chloride ion (Cl-) concentrations are approximately 10x higher outside of cells than inside. Imagine you discovered a novel protein that is required in liver cells for transporting Cl- out of the cell up its concentration gradient, and further found that this protein only functions if the Na+/K+ ATPase is active. Which of the following might you reasonably conclude about the Cl- transport protein?

a K+/Cl- symporter.

Enzymes ALWAYS: A.)Change the path(i.e.mechanism)of the reaction. B.)Decrease the activation energy of the reaction. C.)Increase the rate of the reaction. D.)All of the above

all of the above

True (A) or False (B): The common ancestor to plants acquired chloroplasts before the common ancestor to all Eukaryotes acquired mitochondria.

false

ATP hydrolysis is:

favorable because it's exergonic

Imagine you discover a novel peptide hormone, which you name 'Noho.' If you were interested in how cells respond to Noho, you might study its effects in cultured cells, which are generally homogeneous and do not have any extracellular matrix or other confounding variables. If you wanted to determine whether the Noho receptor is a cell surface receptor or an intracellular cytoplasmic receptor you would want to use differential centrifugation to separate membranes from cytoplasm. If you homogenized your cells and centrifuged the homogenate, where would the membranes end up?

in the pellet

Factors that increase membrane fluidity have the effect of _______ membrane permeability:

increasing

For the hypothetical reaction pathway shown below, both compounds D and E are useful to the cell, but D is toxic to cells if its concentration gets too high. What is the best way to regulate the pathway to ensure that both D and E produced, but that D doesn't reach toxic levels?

inhibition of enzyme E2 by Compound D

The name of the protein dimer that multimerizes to form the cytoskeleton "railroad tracks" in the cell is ___.

tublin