All HW, Quizzes, and Exams from BCMB 311

G-protein-coupled receptors (GPCRs) all have a similar structure with __________ transmembrane domains. When a GPCR binds an extracellular signal, an intracellular G protein, composed of __________subunits, becomes activated. __________ of the G-protein subunits are tethered to the plasma membrane by short lipid tails. When unstimulated, the α subunit is bound to __________ which is exchanged for __________ on stimulation. The __________ activity of the α subunit is important for inactivating the G protein. __________ inhibits this activity of the α subunit, thereby keeping the subunit in an active state.

- seven - three - two - GDP - GTP - GTPase - cholera toxin

Adrenaline is a hormone released by the adrenal glands. It helps you face dangerous situations by causing temporary changes in your body. Your heartbeats and breathing get faster as part of the "fight or flight" response. In this situation you need a very rapid response. Choose the phrase in each pair that is likely to occur more rapidly in response to an extracellular signal and explain your choice for each. changes in protein phosphorylation or changes in proteins being synthesized changes in mRNA levels or changes in membrane potential

1. Changes in protein phosphorylation because these occur faster than protein being synthesizes. This is due to protein synthesis being involved in cell growth. 2. Changes in membrane potential because mRNA is involved in transcription.

Indicate by writing "yes" or "no" whether amplification of a signal could occur at the particular steps described below. Explain your answers. An extracellular signaling molecule binds and activates a GPCR. Adenylyl cyclase produces cyclic AMP. Protein kinase A phosphorylates target proteins.

1. No, it activates only one receptor molecule. 2. Yes, adenylyl cyclase synthesizes cyclic AMP 3. Yes, PKA has many targets and phosphorylates them

Which of these correctly orders the chemical bonds from highest bond strength to lowest?

1. covalent bonds 2. ionic bonds 3. hydrogen bonds 4. van der walls interaction

You obtain muscle cells that are defective in various components of the signaling pathway. Referring to the Figure provided below, indicate how glycogen levels would be affected in the presence of adrenaline in the following cells. Would they be higher or lower than in normal cells treated with adrenaline? 1. cells that lack adenylyl cyclase 2. cells that lack the GPCR 3. cells that lack cAMP phosphodiesterase 4. cells that have an α subunit that cannot hydrolyze GTP but can interact properly with the β and γsubunit

1. higher 2. higher 3. lower 4. lower

Biological systems _____1____ hydrocarbons in stepwise ___2____ reactions. The final product of glycolysis is _____3____which is converted into ____4____ under aerobic conditions before it can be transported across the inner mitochondrial membrane for use in the _____5______. This step results in the production of reduced cofactors such as ____6____ and ____7_____ . These are is critical for the mitochondrion's subsequent production of large amounts of _____8____.

1. oxidize 2. catabolic 3. pyruvate 4. acetyl CoA 5. citric acid cycle 6. NADH 7. FADH2 8. ATP

How many protofilaments make up a microtubule?

13 protofilaments

Based on our class discussion of the molecular properties of phospholipids, which of the following would you expect to yield the most highly mobile phospholipid (listed as number of carbons and number of double bonds, respectively)?

15 carbons with two double bonds

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)?

2 ATP, 2 NADH

What is the net ATP production from glycolysis

2 ATPs

Some G proteins activate phospholipase C and ultimately activate PKC. What event directly follows phospholipase C activation?

An inositol phospholipid is cleaved into Inositol 1,4,5-triphosphate (IP3) and diacylglycerol (DAG)

Which of the following best describes the function of Calmodulin?

An intermediary protein that senses calcium levels and relays signals to calcium-sensitive enzymes.

Sort the following events to reflect the normal order in which they occur in G-protein-coupled receptor signaling. Your answer would be a four-letter string composed of letters A to D only, e.g. ACBD. (A) α subunit releases its GDP and binds a GTP and becomes dissociated from βγ dimer (B) Ligand binds to receptor (C) Receptor conformational changes and receptor interacts with G-protein (D) α subunit binds and activates other effector proteins

BCAD

How does the use of detergents facilitate the purification of membrane-bound proteins in biochemical studies?

detergents solubilize and release membrane-bound proteins from the lipid bilayer

Your friend has just joined a lab that studies vesicle budding from the Golgi and has been given a cell line that does not form mature vesicles. He wants to start designing some experiments but was not listening carefully when he was told about the molecular defect of this cell line. He is too embarrassed to ask and comes to you for help. He does recall that this cell line forms coated pits but vesicle budding and the removal of coat proteins don't happen. Which of the following proteins might be lacking in this cell line?

dynamin

The advantage to the cell of the gradual oxidation of glucose during cellular respiration compared with its combustion to CO2 and H2O in a single step is that

energy can be extracted in usable amounts

Glucose transport into the cells from the blood stream requires all of the following, EXCEPT:

energy in the form of ATP

Phagocytosis is a process by which cells do which of the following?

engulf invading microorganisms

What class of cellular receptors are receptor tyrosine kinases a subset of?

enzyme-coupled receptors

During a state of fight or flight, which of the following takes place?

epinephrine binds adrenergic receptors

The lipid bilayer is a flexible and dynamic two-dimensional structure, allowing for various types of movements. Nonetheless, some types of movements require the assistance of enzymes to occur readily and frequently. Which of the following characterizes these mainly enzymatically facilitated movements?

flip-flop

___ requires the use of two sets of filters. The first filter narrows the wavelength range that reaches the specimen and the second blocks out all wavelengths that pass back up to the eyepiece except for those emitted by the dye in the sample.

fluorescence

Botulism is a potentially fatal foodborne disease caused by the bacterium Clostridium botulinum. C. botulinum produces different toxins, several of which are proteases that cleave neuronal SNARE proteins. What normal process is blocked by cleavage and inhibition of SNARE proteins?

fusion of vesicles with target membranes

In anaerobic conditions, skeletal muscle produces

lactate

Active Akt promotes the survival of many cells by activating Bcl2 which in turn signals the inhibition of apoptosis (programmed cell death). You have discovered a chemical mutagen that you suspect prevents the dissociation of Bad-Bcl2 complex and therefore, prevents the activation of Bcl2. When you add this chemical mutagen to your tissue culture cells what would you expect to observe in your treated versus control (untreated) cells?

less cells will survive in the treated versus control

Cholesterol makes membranes _______ permeable to water and small solutes and ______ rigid

less, more

The figure below shows microtubules sliding through the function of motor proteins. In cilia, the microtubules do not slide, rather they exhibit a power stroke/whipping movement. Which of the following proteins is responsible for attaching the microtubules in a way that allows for this motion to take place.

linking proteins

What unit of length would you generally use to measure a typical plant or animal cell?

micrometers

Within a plasma membrane, where are the polar head groups of the phospholipids located?

on both the inner and outer surface

Which of the following stages in metabolism generates the most amount of ATP?

oxidative phosphorylation

In the Electron Transport Chain, which of the following substances is the "final electron acceptor," and what does it generate?

oxygen, which turns into H2O

Yeast mating has served as an early model for understanding how extracellular chemical signals can be perceived and produce intracellular changes. What type of signaling is shown in the figure below that allows for yeast mating to occur?

paracrine

A molecule moves down its concentration gradient by __________ transport, but requires __________transport to move up its concentration gradient

passive, active

Which enzyme initiates protein digestion in the stomach by cleaving the large protein backbone into smaller peptides?

pepsin

Cell membranes are packed with phospholipids, which of the following is the most common type found in eukaryotic cells?

phosphatidylcholine

Which of the following are not microtubule organizing centers (MTOCs)

polar bodies

Glycolysis is an anaerobic process used to catabolize glucose. What is the final product of Glycolysis and what does it mean for this process to be anaerobic?

pyruvate; no oxygen is required

Studies show that the cholera toxin inhibits GTPase activity of the α subunit. What do you expect will happen to the G protein activity?

remain in the active site

Which of the following is FALSE regrading cAMP?

required for the activation of the alpha-subunit of the G-protein

Which of the following amino acids is/are common targets for phosphorylation by protein kinases?

serine (S) and threonine (T)

Depolarization occurs when

sodium channels open

For the reaction below, the reducing and oxidizing agents respectively are: (picture shows succinate --> fumarate)

succinate and FAD

All of the following processes take place in the mitochondria, EXCEPT:

the conversion of glucose to pyruvate

Based on your knowledge of the properties of biological membranes, what do you think will happen if a lipid bilayer is pierced?

the membrane reseals

If a neuron triggers an action potential, and then experiences a refractory period, what would happen if the neuron was to be stimulated yet again, immediately after the first stimuli?

the neuron would not trigger another action potential

The tertiary structure of a polypeptide is:

the overall 3D organization of the polypeptide

Citrate Synthase, Isocitrate Dehydrogenase and a-Ketogluterate Dehydrogenase are three key enzymes involved in the citric acid cycle. What do all three enzymes have in common?

they are all inhibited by ATP and NADH

Membrane-forming phospholipids have all of these properties except:

they have 1,2, or 3 fatty acid tails

What do the phosphorylated tyrosines on activated RTKs do?

they serve as binding sites and activation for a variety of intracellular signaling proteins

What is the primary purpose of the FRAP (Fluorescence Recovery After Photobleaching) technique in cell biology?

to measure the movement and diffusion rates of fluorescently labeled molecules within a cell

Transporters, in contrast to channels, work by

undergoing a cycle of conformational changes linked to substrate binding

Cell biologists employ targeted fluorescent dyes or modified fluorescent proteins in both standard fluorescence microscopy and confocal microscopy to observe specific details in the cell. Even though fluorescence permits better visualization, the resolving power is essentially the same as that of a standard light microscope because the resolving power of a fluorescent microscope is still limited by the __________ of visible light.

wavelength

Fatty acids can easily be used to generate energy for the cell. Which of the following fatty acids will yield more energy?

CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-COOH

Calmodulin is a monomeric protein with four separate binding sites for which of the following?

Ca2+

Which of the following are second messengers used in cellular signal transduction pathways?

Ca2+ and IP3

Which of the following is a major cellular strategy to avoid cross-talk of independent pathways that share the common intermediate "C" produced after the regulated committed steps?

Compartmentalizing the pathways

Where does the energy for glucose delivery through GLUT come from?

Concentration gradient of glucose across the membrane is what drives delivery

In cilia, the power stroke/whipping motion is made possible through the function of which motor protein and what source of energy is used to power its motor activity?

Dynein; ATP

All receptor tyrosine kinases are 7-pass transmembrane proteins

False

T/F: After a meal, high insulin levels activate hormone sensitive lipase (HSL)

False

T/F: All Kartagener's syndrome patients exhibit situs inversus which is the inverse arrangement of internal organs.

False

T/F: Disulfide bonds are rarely formed the cytosol but they are commonly formed in the oxidizing environment of the lysosome.

False

T/F: Extracellular binding molecules such as those that bind to GPCRs can only be protein-based.

False

T/F: Flip-flop of phospholipids across membrane leaflets happens readily and frequently without the aid of an enzyme.

False

T/F: Methionine and cysteine are the two primary sulfur-containing amino acids in mammals, as a result, both of these amino acids can potentially participate in the formation of disulfide bonds in proteins.

False

T/F: Mitochondrial precursor proteins are unfolded during import and refolded upon arrival, a process that does not require energy input.

False

T/F: One of the main roles of clathrin triskelion is the recognition of the cargo carried by the vesicle

False

T/F: The end product of glycolysis is pyruvate, a two carob sugar

False

T/F: The function of the MAP Kinase (MAPK) enzyme is to phosphorylate and activate MAP Kinase Kinase (MAPKK) enzyme.

False

T/F: The patch clamp is a laboratory technique used to measure the viscosity of a biological membranes.

False

T/F: Tight junctions act as lateral diffusion barriers to restrict membrane proteins to distinct membrane domains by forming random, spot attachments between cells.

False

T/F: When creating a fluorescent fusion protein to study protein localization, the fluorescent protein should strictly be added to the N-terminus of the protein of interest.

False

T/F: When subjected to anaerobic conditions, glycolysis in mammalian cells continues and causes a buildup of pyruvate

False

T/F: All hormones in our bodies travel through the blood stream and are lipid soluble

False; some are water soluble

Movements of organelles in cells can be directly detected and measured by which of the following microscopy techniques?

Fluorescence microscopy of living, unfixed cells containing a transgene that expresses GFP fused to a protein that localizes to the organelle of interest.

Describe how GLUT is recruited to the plasma membrane.

Following a meal, insulin levels in the blood go up, insulin binds to insulin receptors on the cell membrane, which recruits GLUT to the plasma membrane.

What is responsible for holding together alpha helices and beta strands?

Hydrogen bonding formed between different positions of the protein backbone

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant inside a typical mammalian cell?

K+

Examine the reaction below. Which of the following is the oxidizing agent? (picture is of isocitrate and a-ketoglutarate)

NAD+

Microtubules are found in all the following structures except: - Neurons - None, mictorubules are found in all of these structures - Cilia and Flagella - Mitotic spindle

None, mictorubules are found in all of these structures

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 release their cargo in the nucleus.

What is the final result of the electron transfer of the membrane-based process that drives ATP synthesis in the mitochondria?

O2 is reduced to H2O

In the process of oxidative phosphorylation, which component(s) undergo oxidation and phosphorylation, respectively?

Oxidation - NADH and FADH2; Phosphorylation - ADP

____ requires coating a sample with a thin layer of a heavy metal to produce three- dimensional images of the sample surface.

SEM

In the final stage of the oxidation of food molecules, a gradient of protons is formed across the inner mitochondrial membrane. If cells were exposed to an agent that causes the membrane to become freely permeable to protons, which of the following effects would you expect to observe?

The levels of ATP will drop relative to those of ADP

In the case of Angina Pectoris, as activity is increased so does the demand for oxygen. However, the narrowing of the coronary arteries in these individuals prevents proper supply of oxygen from reaching the heart. As a result, the individual suffers pain in the cardiac muscle. In light of our class discussion of metabolism, describe how the state of low oxygen influences glycolysis, the levels of NAD, the fate of pyruvate, and the cause of pain.

The result of glycolysis is the production of 2 pyruvates. For every one pyruvate produced, there is 1 NADH and 2 ATPs made. Pyruvate has to be oxidized in order to allow the NADH produced from glycolysis to re-convert to NAD+. And NAD+ is what regulates lactate levels. Therefore, without any oxygen present, NADH cannot re-convert into NAD+. This results in increased lactate levels, which cause pain in the muscles.

For an individual with Kartagener syndrome which of the following is true?

They experience chronic sinusitis due to immotile cilia that line the respiratory tract

MAP kinase kinase kinase (MAPKKK) phosphorylates and activates MAPKK, which does the same for MAPK

True

T/F: A glucose-Na+ symporter uses the electrochemical Na+ gradient to drive the active import of glucose, while GLUT (Glucose transporter) does not require energy input for glucose delivery.

True

T/F: IP3 and DAG are both examples of second messengers.

True

T/F: If red blood cells (RBSs) are added to a hypotonic solution, you would expect that water will enter into the cells causing swelling and eventually hemolysis.

True

T/F: The administration of an epinephrine auto-injector (such as an EpiPen) combats anaphylactic shock by inducing sympathetic system activation.

True

T/F: There are normally a high cytosolic concentration of RanGDP and high nuclear concentration of RanGTP

True

T/F: Triton X100 and SDS are examples of detergents used to purify membrane proteins.

True

Which of the following scientists coined the term "mitosis"?

Walther Flemming

What property of a triacylglycerol would prevent it from becoming incorporated into the plasma membrane? (Hint: What are they lacking when you compare their structure to that of any of the three classes of membrane lipids?)

When their structure is compared to that of any of any of the three classes of membrane lipids, triacylglycerols lack a hydrophilic head. This means that they are entirely hydrophobic.

Examine the image below. Which of the following is most likely true of the signaling molecule shown. (shows a signal molecule binding to an intracellular receptor and then binding to DNA)

a lipid soluble steroid hormone

The figure below shows the pathway through which nitric oxide (NO) triggers smooth muscle relaxation in a blood vessel wall. Which of the following situations would lead to relaxation of the smooth muscle cells in the absence of acetylcholine?

a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP

In breast tumor cells, estrogen receptors may or may not be present. When estrogen receptors are detected in the tumor cells, this is considered better prognosis than if they were absent. a. You have received biopsy results for one of your patients that is positive for estrogen receptor, would you recommend the use of hormone therapy or taxol to control the growth of the tumor? b. Explain your choice stating the benefit of the one you chose and the potential disadvantage (or potential harm) of the one you did not choose.

a. Hormone therapy would be recommended to control the growth of the tumor. b. Hormone therapy can be regulated more, giving it an advantage. Whereas, Taxol is an anti-breast cancer drug that targets all cells, meaning it is not selective.

What is the primary function of ATP synthase in oxidative phosphorylation?

allowing protons to flow back and using energy to generate ATP

If a cell targets itself, as in the case of T-Cell proliferation by Cytokines, then the signaling is known as _____________

autocrine

The image below displays data obtained through a technique known as single-particle tracking (SPT) for four different kinds of membrane receptors (Adapted from Bacher et al.,2004) Your task is to identify the receptor among these four that exhibits the least movement on the cell membrane's surface. Please choose the color associated with this particular receptor.

blue

Microtubules exhibit a property known as dynamic instability both in vitro and in vivo. However, in the cell these dynamics are influenced by different proteins. One particular class of proteins is important for stabilizing the plus ends, these proteins are known as:

capping proteins

Which of the following solutes would you expect to have the highest rate moving across the plasma membrane through simple diffusion?

carbon dioxide

Ras is activated by a Ras-activating protein (Ras-GEF) that does what?

causes Ras to exchange GDP for GTP

Microtubules are important cytoskeletal components found in all the following structures except:

cell membranes

During which metabolic process is the majority of the CO2 that we exhale released?

citric acid cycle (Krebs cycle)

Which of the following choices BEST describes the role of the lysosome?

clean-up, recycling, and disposal of macromolecules

__ scans the specimen with a focused laser beam to obtain a series of two- dimensional optical sections. The laser excites a fluorescent dye molecule, and the emitted light from each illuminated point is captured through a pinhole and recorded by a detector.

confocal

Which of the following steps or processes in aerobic respiration include the production of carbon dioxide?

conversion of pyruvate to acetyl CoA

Which part of the cell is made up of a network of filaments that maintains the cell shape and structure?

cytoskeleton

____ has the ability to resolve cellular components as small as 2 nm.

TEM

What is one piece of evidence supporting the theory that eukaryotic cells were once strictly anaerobic and later formed a symbiotic relationship with aerobic bacteria that became mitochondria?

The discovery of DNA in mitochondria, similar to bacterial DNA

____ employs a light microscope and requires that samples be fixed and stained in order to reveal cellular details.

conventional light /bright-field

In a ____ microscope, the light source is below the specimen and the light rays that pass through the specimen without being scattered are collected, magnified and focused by the lens system without further manipulation.

conventional light microscope

Cells that are specialized for the secretion of proteins are likely to have which of the following features?

enlarged ER

Consider the apical location of a particular protein expressed in epithelial cells, illustrated in part A of the figure below. Which type of defect described below is the most likely to cause the redistribution of that protein around the entire cell, shown in part B.

improper functioning of tight junction protein

Where does most new membrane synthesis take place in a eukaryotic cell?

in the ER

Lidocaine is used as topical local anesthetic to block the signal propagation of skin neurons involved in pain perception. This drug works by

inhibiting voltage-gated Na+ channels

If Na+ channels are opened in a cell that was previously at rest, how will the resting membrane potential be affected?

it becomes more positive

Alanine is an amino acid with the structure below. Choose the correct statement about the role of alanine in stabilizing the tertiary structure of a protein?

it is most likely found in the interior of a protein

When levels of insulin are high in the blood stream

Hormone sensitive lipase (HSL) are inhibited

Your friend has purified a membrane associated protein that contains a seven transmembrane helices, with a width of approx. 40 Å. Knowing that you are studying similar topics in your Cell Biology course, your friend asks if you can help identify to which class of proteins this one might belong. What would you suggest?

GPCRs

Which of the following correctly matches the number of carbon atoms with the respective molecule in glucose metabolism?

Glucose - 6 carbons, Pyruvate - 3 carbons, Acetyl-CoA - 2 carbons

What type of G-Protein is used in the signal transduction cascade shown below? (has IP3 and DAG)

Gq

During oxidative phosphorylation, ATP synthesis is powered by movement of __________ through the __________.

H+; ATP synthase

You go camping in the Smokies and set up your tent and a campfire and cook a big hearty stew of beef and potatoes and eat it. You then rest on your hammock with your favorite book (Essential Cell Biology, of course). Right now, the levels of insulin in your blood are elevated, therefore:

HSL are inhibited

Acetylcholine acts at a GPCR on heart muscle to make the heart beat more slowly. It does so by ultimately opening K+ channels in the plasma membrane, which decreases the cell's excitability by making it harder to depolarize the plasma membrane. Indicate whether the following condition would increase or decrease the effect of acetylcholine. Modification of the Gα subunit by the cholera toxin (Cholera toxin inhibits the GTPase activity of the Gα subunit, keeping the subunit in an active state for a longer time).

Increase

Which of the following enzymes in the citric acid cycle determines the rate-limiting step in the entire process?

Isocitrate Dehydrogenase

You decide to examine the fate of your GFP fusion protein in these yeast strains and engineer the mutant strains to express your GFP fusion protein. You realize that you did not label the mutant yeast strains and no longer know which strain is defective in what process. You end up numbering your strains with the numbers 1 and 2, and then you carry out the experiment anyway, obtaining the results shown in the figure below (the black dots represent your GFP fusion protein). Describe the process that is defective in each of these strains and indicate which one is your wildtype control.

Strain A has protein accumulating in the ER, which means that this cell has a mutation that blocks transport from the ER to the Golgi apparatus. Strain B has secreted protein, and therefore is the wild-type control. Strain C has protein accumulating in the Golgi apparatus, and thus has a mutation that blocks exit of proteins from the Golgi apparatus.

Signaling molecules are responsible for transmitting information between cells in your body. The function of different types of signaling molecules can vary greatly. a. The same signal molecule can induce different responses in different target cells, provide at least two ways in which this can be accomplished. b. Signaling of cyclin-dependent kinases at the transition from interphase to mitosis induces important changes in microtubule dynamics. Upon entry of mitosis (cell division), would you expect that microtubules will be more dynamic or less dynamic and why?

a. This can be done by using different GPCRs or second messengers. For example, epinephrine in the skeletal muscle has a different response than epinephrine in other target organs. b. I would expect them to be more dynamic because that would allow them to move to the opposite ends during metaphase and other steps. This would allow them to have less dynamic instability (more stabilized). Dynamic instability is where they are moving growing and shrinking randomly.

Which of the following protein families are NOT involved in directing transport vesicles to the target membrane?

adaptins

Assuming that the second messenger produced (depicted as blue circles in the image below) is cAMP, what is the name of the activated enzyme?

adenylyl cyclase

A transmembrane polypeptide chain usually crosses the lipid bilayer as an α helix such as the one shown below. What type of amino acid side chains would you expect to project outward and interact with the lipid tails?

hydrophobic

Akt promotes the survival of many cells by affecting the activity of Bad and Bcl2, as diagrammed in the Figure provided. Which of the following statements is FALSE?

in the absence of a survival signal, Bad is phosphorylated

where does oxidative phosphorylation take place in the cell

inner mitochondrial membrane

What is the smallest distance two points can be separated and still resolved using light microscopy?

0.2 um

If you are looking through the eye piece of a conventional light microscope with an eyepiece with 10X magnification and the objective lens you are using is 60X, what is the total magnification of the image?

600x

Which of the following cellular structures possess a double membrane? A) Nucleus B) Mitochondria C) Endoplasmic reticulum

A and B

Fluorescence has become an important tool in microscopy. Which of these describes the action of a fluorophore?

Absorbs light of specific wavelengths, converts a portion of the energy to heat and re-emits a lower energy, longer wavelength photon

In a negative feedback loop cycle, testosterone released from the testes affects the release of Gonadotropin-releasing hormone (GnRH) from the Hypothalamus and the Gonadotropins, Luteinizing Hormone (LH) and Follicle Stimulating Hormones (FSH) from the pituitary. In an individual with Klinefelter syndrome, testosterone levels are significantly reduced. Refer to the diagram to explain how you would expect the levels of GnRH and LH and FSH in an individual with Klinefelter syndrome to be affected?

Based on the diagram, the testosterone has a direct negative affect on GnRH (the presence of testosterone decreases the release of Hypothalamus GnRH). This decreased release, however, increases the release of pituitary LH and FSH. Therefore, if an individual has decreased levels of testosterone, the release of Hypothalamus GnRH will be increased. And the amount of Pituitary LH and FSH will be decreased.

T/F Photobleaching is a reversible process where a fluorophore temporarily loses its ability to fluoresce due to photon-induced chemical damage.

False

The FRAP technique occurs in a series of steps. Select the statement that incorrectly describes a step in the FRAP procedure.

Fluorescent molecules in the cell are reversibly bleaches

In one experiment, investigators create a liposome—a vesicle made of phospholipids—that contains a solution of 1 mM glucose and 1 mM sodium chloride. If this vesicle were placed in a beaker of distilled water, what would happen the fastest?

H20 would diffuse in

You have discovered a new virus and suspect that it has width of approximately 20 nm. Based on results from your biochemical assays, you believe that this virus has a spherical capsid. You are now ready to visualize the 3d capsid structure to confirm its shape and you have all types of microscopes at your disposal. Your friend suggests that you use TEM, would you agree? and if so why would you and if not, what type of microscope would you used instead and why?

I would not agree. TEM gives a 2D image. Whereas, SEM gives a 3D image which is what you ned to visualize and confirm the 3D capsid structure.

Your friend is attempting to study the function of the Na+ K+ pump and has created spherical liposomes that contain only the Na+ K+ pump. She has inserted the pumps properly in the liposome. She has added different ions and energy sources to the beaker with the liposomes, but no pumping of ions occurs. You explain that components must be in the proper location inside or outside the liposome for the pump to work. Assuming she has already added ATP to the lysosome, which of the four items listed below would you suggest for her to add and where? Help her by adding the proper components inside or outside of the liposome so that proper pumping occurs. Also, indicate if any of these components are unneeded. Cl- K+ Na+ Glucose

I would tell her to add Na+ inside of the liposome and K+ outside of the liposome. This is due to the Na+/K+ pump functioning to move 3 Na+ out of an area and then move 2 K+ in to an area. Glucose would not be needed because it needs Na+ to be entered into the liposome. In addition, Cl- is unneeded.

How does confocal microscopy differ from standard fluorescence microscopy?

In confocal microscopy, instead of illuminating the entire specimen, only a very thin "optical section" within the field of the specimen is illuminated at each point in time.

Which one of the following is involved in maintaining a resting membrane potential?

Na+/K+ ATPase pump moves 3Na+ out for every 2K+ in

Most sports drinks contain both carbohydrates and salts. The carbohydrates replace glucose burned during exercise and the salts replace salts lost in sweat. The salt also helps the small intestine absorb glucose. Pick the answer that accurately describes which salt is most beneficial for glucose absorption.

NaCl, because Na+ is needed for glucose entry

With regards to the source of energy utilized, what is the difference between primary and secondary active transport?

Primary - Energy derived directly from ATP Secondary - Energy from coupling the transport of another solute down its concentration gradient

Who is credited with coining the term "cell" in 1665 and is known for his early observations of plant cells under a microscope?

Robert Hooke

In reference to the protein structure-function relationship: Protein _____ dictates protein ______, which dictates its ________.

Sequence, Structure, Function

Your friend now has the pumps successfully pumping ions. She added an equal concentration of both ions to the correct sides of the liposomes along with an excess of the energy source. She is surprised when the pumps stop working after a short time. Explain why the transporter stopped pumping ions?

She added equal concentration of both ions to the correct side but the pump expels 3 Na+ for every 2 K+ it brings in so the starting concentration of Na+ inside should be 1.5X concentration of K+ on the outside.

Rough Endoplasmic Reticulum (rough ER) is found at high levels in plasma cells. What is the main difference between rough and smooth ER? What is the role of plasma cells that is facilitated by having high levels of rough ER?

The main difference between rough ER and smooth ER is the presence of ribosomes. Rough ER contains ribosomes, whereas, smooth ER does not contain ribosomes. The role of plasma cells that is facilitated by having high levels of rough ER is for the transport of antibody proteins. This is good for the immune system.

State one of the main 2 main features of a confocal microscope discussed in class that reduce photo-bleaching and chemical damage of the sample imaged generating thin optical sections?

The pinhole is a feature by only allowing certain light through

With regards to phospholipids, what are two factors that have an effect on membrane fluidity?

The two factors that have an effect on membrane fluidity are: length of hydrocarbon tails (range from 14-24) and number of double bonds (saturated vs unsaturated).

Considering the variations in saturated fat content per tablespoon among the substances listed below, what would be your anticipation regarding the melting temperature?

There would likely be a direct correlation, with higher saturated fat content corresponding to a higher melting temperature.

Which of the following is FALSE about molecular chaperones?

They interact with unfolded polypeptides and remain associated with the protein after proper folding is achieved.

T/F: A hypotonic solution is likely to cause hemolysis in red blood cells due to osmosis.

True

T/F: Direct immunofluorescence involves the use of labeled antibodies to detect specific antigens in a sample, while indirect immunofluorescence uses unlabeled antibodies and a secondary labeled antibody to detect the bound primary antibody.

True

Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called

active transport

A kinase is an enzyme that is important for

addition of a phosphate group to another protein

All of the following are true statements about hydrogen bonding except:

all of these statements are true: - Hydrogens bound to a sufficiently electronegative atom act as donors, while another electronegative atom is the acceptor - They are noncovalent interactions that can play important roles in the interactions of biomolecules - Individually, they are stronger than a Van der Waals interaction

A series of enzymes catalyze the reaction X > Y> Z > A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding deceased the activity of the enzyme. What is substance A?

an allosteric inhibitor

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?

an aquaporin

In Bacteria, which of the following statements regarding ribosomes is accurate?

bacteria possesses ribosomes for protein synthesis

The electrochemical gradient across a cell membrane is crucial for various cellular processes. Which of the following best defines an electrochemical gradient?

it is the sum of the forces from the concentration gradient of the solute and the charge of the solutes..

The stimulation of auditory nerves depends on the opening and closing of channels in the auditory hair cells. Which type of gating mechanism do these cells use?

mechanically-gated

Which of the following statements is TRUE? - Membrane lipids frequently flip-flop between one monolayer and the other. - Membrane lipids diffuse within the plane of a single leaflet. - In eukaryotes, all membrane-enclosed organelles are surrounded by one lipid bilayer. - Phospholipids will spontaneously form liposomes in nonpolar solvents.

membrane lipids diffuse within the plane of a single leaflet

Cholesterol serves several essential functions in mammalian cells. Which of the following is NOT influenced by cholesterol?

membrane thickness

Sodium ions, oxygen (O2), and glucose pass directly through lipid bilayers at dramatically different rates. Which of the following choices presents the correct order, from fastest to slowest?

oxygen, glucose, sodium ions

____ uses a light microscope with an optical component to take advantage of the different refractive indices of light passing through different regions of the cell.

phase contrast

A ______________ is composed of a phosphate and glycerol head and 2 fatty acid chain tails.

phospholipid

Which statements are TRUE about the differences between phospholipids and detergents?

phospholipids form bilayers in water, whereas detergents tend to form micelles

The figure below illustrates changes in membrane potential during the formation of an action potential. What membrane characteristic or measurement used to study action potentials is indicated by the arrow? (arrow is at the bottom)

resting membrane potential

Bacterial cells share which of the following structures with eukaryotic cells?

ribosomes

In an animal cell, the membrane-bound organelles include all of the following except:

ribosomes

Lipid synthesis is largely catalyzed by enzymes at the cytosolic side of the smooth ER, which facilitate the insertion of these new lipids into the cytosolic leaflet of the ER membrane. However, these lipids cannot sustainably be added to just one leaflet; they must be able to get to the inner leaflet as well. What is primarily responsible for this movement between leaflets?

scramblase

Some cells express aquaporin proteins—they are channel proteins that facilitate the flow of water molecules through the plasma membrane. What regulates the rate and direction of water diffusion across the membrane?

solute concentration on either side of the membrane

The primary structure of a polypeptide is:

the precise sequence of amino acids in the polypeptide

Which of the following statements about resting membrane potential is TRUE?

the resting membrane potential for most animal cells is negative, because the inside of the cell is more negatively charged

Prions become pathogenic (disease causing) when:

their structure is converted from a-helices into a beta-pleated isoform

An ionic bond between two atoms is formed as a result of the

transfer of electrons from one atom to another

Which of the following would not be found in a plasma membrane?

triacylglycerols (TAGs)

Which of the following lipids is the most hydrophobic?

triglycerol