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Biochemistry > Exam 3 > Flashcards

Exam 3 Flashcards

1
Q

Heterotrimeric G proteins

-function as an autoinhibitory segment
-can function as a mediator to adenylate cyclase activity
-consist of 3 subunits, Galpha, Gbeta, Ggamma
-are anchored to the cytoplasmic side of the membrane

A

-can function as a mediator to adenylate cyclase activity
-consist of 3 subunits, Galpha, Gbeta, Ggamma
-are anchored to the cytoplasmic side of the membrane

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2
Q

The transporters responsible for moving water across membranes are ______.

-aquaporins
-integrins
-receptor proteins
-aquachannels

A

aquaporins

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3
Q

Which of the following is NOT a general feature of the lipid bilayer in biological membranes?

-Individual lipid molecules are free to diffuse laterally within one leaflet of the bilayer
-The bilayer is stabilized by covalent interactions between the lipid molecules and integral membrane proteins
-The polar head groups of the membrane lipids face outwards to interact with the aqueous environment
-The thickness of the bilayer depends on the length of the fatty acids in the lipids

A

The bilayer is stabilized by covalent interactions between the lipid molecules and integral membrane proteins

(This statement is FALSE. The bilayer is stabilized by non-covalent interactions between the lipid molecule and integral membrane proteins.)

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4
Q

Facilitated diffusion requires ______.

-a channel protein to bind with its transportable substance
-a channel protein not to bind with its transportable substance
-the expenditure of energy to transport a substance across the membrane
-a receptor protein

A

a channel protein to bind with its transportable substance

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5
Q

A protein studied in the lab dissociates from the cell plasma membrane after treatment with high salt concentrations or changes in pH. What type of protein could this be?

-Integral membrane protein
-Peripheral membrane protein
-Receptor protein
-Ion channel protein

A

Peripheral membrane protein

(Peripheral membrane proteins associate with the membrane by forming electrostatic and hydrogen bond interactions. Peripheral proteins may be dissociated from the membrane by changes in pH or salt concentration.)

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6
Q

Which one of the following is a general feature of the lipid bilayer in biological membranes?

-Polar, but uncharged, compounds diffuse readily across the bilayer.
-Individual lipid molecules in one face (monolayer) of the bilayer diffuse (flip-flop) to the other monolayer
-Individual lipid molecules are free to diffuse laterally in the bilayer.
-The bilayer is stabilized by covalent bonds between neighboring phospholipid molecules.

A

Individual lipid molecules are free to diffuse laterally in the bilayer.

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7
Q

Which of the following correctly states an essential step in the function of the heterotrimeric G protein function?

-A cascade of events must occur that ultimately activate protein kinase C.
-Binding of a hormone to a receptor must signal the exchange of GDP for GTP.
-Binding of GTP to the receptor protein must induce a change in the conformation of the receptor.
-Binding of cAMP to the alpha subunit of the G protein must initiate translocation of the subunit
-All of the above are correct.

A

Binding of a hormone to a receptor must signal the exchange of GDP for GTP.

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8
Q

Activation of a G protein in response to hormone binding requires binding of the _____to the ____ subunit.

-GTP; beta
-GDP; beta
-GDP; alpha
-GTP; alpha
-GDP; gamma

A

GTP; alpha

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9
Q

If the 14-carbon saturated fatty acid myristoyl-CoA is oxidized completely to carbon dioxide and water (via the beta-oxidation pathway, the citric acid cycle, and oxidative phosphorylation), what is the yield of ATP per molecule of myristoyl-CoA? (Assume that re-oxidation of NADH via the electron transport chain yields the equivalent of 2.5 ATP, and that re-oxidation of FADH2 yields 1.5 ATP.)

-94 ATP
-100 ATP
-98 ATP
-92 ATP

A

94 ATP

(The oxidation of this activated C-14 saturated fatty acid produces 7-acetyl-CoA, 6 NADH, and 6 FADH2)

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10
Q

Beta oxidation of fatty acids includes several steps. Following initial coenzyme A activation, these steps include ______.
What is the correct order of beta-oxidation steps?

-hydration of double bond
-cleavage of carbon-carbon bond and formation of new acyl-CoA
-oxidation of beta-carbon hydroxyl to keto form
-enoyl formation at the beta carbon

A
  1. Enoyl formation at the beta carbon
  2. Hydration of double bond
  3. Oxidation of beta-carbon hydroxyl to keto form
  4. Cleavage of carbon-carbon bond and formation of new acyl-CoA
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11
Q

Like eicosanoids, endocannabinoids are derived from ____.

-NSAIDs
-anandamide
-prostaglandins
-arachidonic acid
-cyclooxygenase

A

Arachidonic acid

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12
Q

What are the characteristics of most unsaturated fatty acids found within a human cell?

-protonated carboxylic acid and trans double bonds
-deprotonated carboxylic acid and trans double bonds
-protonated carboxylic acid and cis double bonds
-deprotonated carboxylic acid and cis double bonds
-none of the above

A

Deprotonated carboxylic acid and cis double bonds

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13
Q

Which of the following forms bilayers spontaneously in water?

-Triacylglycerols
-Fatty acids
-Cholesterol
-Glycerophospholipids

A

Glycerophospholipids

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14
Q

How will the carbon atoms from an odd-numbered fatty acid enter the citric acid cycle?

-as acetyl-CoA and malate
-as acetyl-CoA and citrate
-as acetyl-CoA and propionyl-CoA
-as acetyl-CoA and succinyl-CoA

A

As acetyl-CoA and succinyl-CoA

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15
Q

What is the final product of fatty acid synthesis?

-Butyryl-CoA
-Acetyl-CoA
-Palmitate
-Palmitoyl-CoA

A

Palmitate

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16
Q

Which of the following statements about ketone bodies is FALSE?

-Ketone bodies can enter the citric acid cycle as acetyl-CoA
-Common ketone bodies are acetone, acetoacetate, and beta-hydroxybutyrate
-Ketone bodies are produced by the liver when fatty acid supplies are limited.
-The production of ketone bodies increases when acetyl-CoA levels are high
-Ketone bodies serve as alternative energy sources to glucose and fatty acids for the brain.

A

Ketone bodies are produced by the liver when fatty acid supplies are limited.

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17
Q

What is the product of fatty acid activation?

-Acyl adenylate
-Acyl-CoA
-Acyl-carnitine
-Acyl ester
-Pyrophosphate

A

Acyl-CoA

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18
Q

Glycerophospholipids _______.

-have two acyl chains
-have long chain fatty acids
-have a glycerol backbone
-are the predominant lipids in membrane
-all of the above

A

All of the above

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19
Q

Integral membrane proteins ______.

-can be monotopic
-can be ditopic
-all of the above
-none of the above

A

All of the above

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20
Q

Facilitated diffusion requires ________.

-a receptor protein
-a channel protein to bind with its transportable substance
-a channel protein not to bind with its transportable substance
-the expenditure of energy to transport a substance across the membrane

A

a channel protein to bind with its transportable substance

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21
Q

Receptors ______.

-are membrane-spanning proteins
-bind to the extracellular signals and undergo a conformational change
-are integral membrane proteins
-all of the above

A

All of the above

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22
Q

The transporters responsible for moving water across membranes are ______.

-receptor proteins
-integrins
-aquachannels
-aquaporins

A

aquaporins

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23
Q

The membrane protein that facilitates the cotransport of two ions in the same direction is called a _____.

-symporter
-antiporter
-uniporter
-mulitporter

A

symporter

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24
Q

The operation of the sodium-potassium pump in membranes is an example of _______.

-ligand gated ion channel
-voltage-gated ion channel
-a peripheral membrane protein
-all of the above

A

voltage-gated ion channel

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25
Q

Lipid rafts are structures ________.

-where sphingolipids can transiently and loosely aggregate in the plasma membrane
-that are involved in cell signaling and membrane transport
-some membrane proteins are clustered in some membrane segments
-all of the above
-none of the above

A

All of the above

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26
Q

A protein studied in the lab dissociates from the cell plasma membrane after treatment with high salt concentrations or changes in pH. What type of protein could this be?

-A peripheral membrane protein
-An integral membrane protein
-An ion channel protein
-A receptor protein

A

A peripheral membrane protein.

(Peripheral membrane proteins associate with the membrane by forming electrostatic and hydrogen bond interactions. Peripheral proteins may be dissociated from the membrane by changes in pH or salt concentration.)

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27
Q

Which one of the following statements regarding plasma membranes is TRUE?

-Carbohydrates are found only on the intracellular side of the plasma membrane.
-They are symmetric because of the symmetric nature of the lipid bilayer
-Proteins associated with the plasma membranes are always integral in nature
-They are asymmetric due to differences between lipids in either side of the lipid bilayer
-Lateral diffusion of lipids requires specific enzymes

A

They are asymmetric due to differences between lipids in either side of the lipid bilayer

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28
Q

Possible intracellular effects of insulin binding to its receptor may include _______.

-increased glucose transport into the cell by increasing glucose transporters on the cell surface
-decreased protein kinase A signaling by lowering cAMP concentrations
-altering gene expression via MAP kinase pathway
-increased protein synthesis
-all of the above
-none of the above

A

All of the above

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29
Q

The ligand epinephrine binds to the ________. The hormone receptor complex exchanges the bound GDP for GTP allowing _______ to activate adenylate cyclase, producing ________. The activation of the catalytic subunits of _______. dissociate and phosphorylate targets in the cell.

A

-Beta-adrenergic receptor
-Galpha
-cAMP
-Protein Kinase A

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30
Q

Which of the following is (are) an advantage(s) of protein phosphorylation in regard to biochemical signaling?

-Phosphorylation is rapid and specific
-Phosphorylation is enzymatically reversible
-Phosphorylation can be amplified by cascade systems
-Phosphorylation results in covalent modification of enzymes

A

All of the above

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31
Q

Which of the following terms describes all glycerophospholipids?

-Zwitterionic
-Amphipathic
-Nonpolar
-Amphoteric
-None of the above

A

Amphipathic

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32
Q

The most notable difference between _____ and other membrane lipids is its planar nature.

-Cholesterol
-Arachidonic acid
-Ganglioside
-Plasmologen
-Triacylglycerol

A

Cholesterol

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33
Q

In a mixed bilayer at lower temperatures, cholesterol restricts the movement of nearby acyl chains, resulting in a more ______ membrane. As the percentage of cholesterol in the membrane increases past a certain point, the membrane becomes more ______.

A

fluid; solid

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34
Q

In an alpha helical protein that spans a cell membrane, ______ would likely be in the center of the membrane, ______ would likely be associated with the polar head groups, and _____ would likely be associated with the aqueous environment.

-Trp; Asn; Ala
-Leu; Gln; Asp
-Tyr; Glu; Gly
-Ille; Arg; Gln
-Val; Ser; Thr

A

Leu; Gln; Asp

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35
Q

Which of the following statements describes integral membrane proteins?

-They never completely span the lipid bilayer.
-They are easily removed by changes in pH or high salt.
-Amino acids that contact the core of the membrane are hydrophobic
-They tend to be water soluble
-Their association with the membrane is through an attached fatty acyl or prenyl group.

A

Amino acids that contact the core of the membrane are hydrophobic

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36
Q

The movement of glucose into a cell when blood sugar is high is accomplished by _____. The movement of K+ against its concentration gradient is accomplished by ______.

-simple diffusion; active transport
-passive transport; passive transport
-active transport; membrane potential
-simple diffusion; passive transport
-passive transport; active transport

A

passive transport; active transport

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37
Q

Integrins and aquaporins are examples of ______.

-uniporters
-peripheral membrane proteins
-integral membrane proteins
-signal transduction receptors
-none of the above is correct

A

integral membrane proteins

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38
Q

_______ are amphipathic molecules that constitute the major lipid components of the cell membrane.

A

Phospholipids

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39
Q

With respect to polarity, membrane lipids can be described as ______.

A

amphipathic

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40
Q

Which of the following statements describes integral membrane proteins?

-They protect the contents of the cell from chaotropic agents as urea
-They are easily dissociated from the membrane by changes in pH or high salt concentration
-They are held in place by hydrophobic effects between the membrane and hydrophobic amino acids

A

They are held in place by hydrophobic effects between the membrane and hydrophobic amino acids

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41
Q

Which of the following amino acids from an integral membrane protein would likely contact the membrane?

-Asn
-Gln
-Glu
-Ala
-Asp

A

Ala

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42
Q

Transmembrane proteins _______.

-are predominantly constructed of a single hydrophobic alpha helix that serves as a pore
-are often constructed from bundles of hydrophobic alpha helices
-are sometimes constructed from beta sheets and serve as pores
-require detergents to remove them from membranes

A

-are often constructed from bundles of hydrophobic alpha helices
-are sometimes constructed from beta sheets and serve as pores
-require detergents to remove them from membranes

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43
Q

Which of the following segments of the integral membrane protein glycophorin most likely contains the membrane-spanning sequence?

-LSTTEVAMHTTTSSSVSKSY
-SQTNDTHKRDTYAATPRA
-VSEISVRTVYPPEEETGE
-ITLIIFGVMAGVIGTILLI
-YGIRRLIKKSPSDVKPLP

A

ITLIIFGVMAGVIGTILLI

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44
Q

An example of non-mediated transport is _____

-simple diffusion
-endocytosis
-exocytosis

A

Simple diffusion

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45
Q

A transporter that moves two substances simultaneously in the same direction is an example of a _________.

A

symporter

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46
Q

D-glucose and D-mannitol are similarly soluble, but D-glucose is transported through the erythrocyte membrane 4 times as rapidly as D-mannitol. What is the most likely explanation?

-D-glucose undergoes simple diffusion more rapidly than D-mannitol because glucose is less polar
-D-glucose and D-mannitol enter the erythrocyte via an ion-gated channel
-D-glucose and D-mannitol are transported via a system that distinguishes the two sugars.
-D-glucose flux through the membrane is linear, whereas D-mannitol flux is described by a hyperbolic curve
-None of the above provides the explanation.

A

D-glucose and D-mannitol are transported via a system that distinguishes the two sugars.

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47
Q

A pore that simultaneously transports 2 different molecules in different directions is called ______.

-a symport
-a uniport
-a gap junction
-an equilibrium channel
-an antiport

A

an antiport

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48
Q

Regions of a membrane that contain tightly packed cholesterol and sphingolipids are called ________ and are thought to be important to ______.

A

lipid rafts; cell signaling

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49
Q

Which of the following is true regarding membrane asymmetry?

-Transverse diffusion occurs very quickly.
-Lateral diffusion occurs very slowly.
-A flippase causes lateral diffusion to occur very rapidly.
-Carbohydrates attached to membrane lipids are usually found on the cytosolic side of the membrane.
-None of the above

A

None of the above

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50
Q

What enzyme is activated by association with an active G protein?

-adenylate cyclase
-cAMP phosphodiesterase
-protein kinase A
-protein kinase G
-all of the above

A

adenylate cyclase

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51
Q

The second messenger _______ is produced by the enzyme ______.

-nitric oxide; arginase
-cGMP; GTP cyclase
-cAMP; adenylate cyclase
-triacylglycerol; phospholipase C
-inositol diphosphate; phospholipase C

A

cAMP; adenylate cyclase

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52
Q

For cAMP to _______ protein kinase A, cAMP binds to the _______ subunits.

A

activate; regulatory

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53
Q

cAMP binds to the ______ subunits of protein kinase A, allowing the tetramer to dissociate and release ______.

-active subunits; an active catalytic dimer
-active subunits; two active catalytic monomers
-regulatory subunits; an active catalytic dimer
-regulatory subunits; two active catalytic monomers
-regulatory subunits; two active regulatory monomers

A

regulatory subunits; two active catalytic monomers

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54
Q

Which of the following is (are) associated with cAMP binding to cAMP-dependent protein kinase A (PKA)?

-cAMP binds to the regulatory subunits
-PKA tetrameric regulatory subunits and catalytic subunits dissociate
-Catalytic subunits phosphorylate multiple targets with specific serine and threonine residues.
-cAMP is membrane-bound via phosphoinositol attachment

A

-cAMP binds to the regulatory subunits
-PKA tetrameric regulatory subunits and catalytic subunits dissociate
-Catalytic subunits phosphorylate multiple targets with specific serine and threonine residues.

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55
Q

Which of the following functions as a regulatory protein by dephosphorylating activated enzymes?

-receptor tyrosine kinase
-phosphoprotein phosphatase
-heterotrimeric G protein phosphorylase
-guanine nucleotide exchange factor
-Sos protein

A

phosphoprotein phosphatase

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56
Q

The activity of protein kinase A is affected by which of the following?

-activated adenylate cyclase
-levels of cAMP
-phosphodiesterases
-cholera toxin
-all of the above

A

All of the above

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57
Q

Which of the following correctly states an essential step in the function of heterotrimeric G protein function?

-A cascade of events must occur that ultimately activates protein kinase C.
-Binding of a hormone to a receptor must signal the exchange of GDP for GTP.
-Binding of GTP to the receptor protein must induce a change in the conformation of the receptor.
-Binding of cAMP to the alpha subunit of the G protein must initiate translocation of the subunit
-All of the above

A

Binding of a hormone to a receptor must signal the exchange of GDP for GTP.

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58
Q

Ligand binding to a receptor tyrosine kinase causes _____ of the receptor, which then ______ the next protein in the signaling pathway.

-methylation; hydrolyzes
-hydrolysis; inhibits
-phosphorylation; phosphorylates
-acylation; activates
-none of the above

A

phosphorylation; phosphorylates

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59
Q

The ______ receptor is a receptor tyrosine kinase.

-alpha1-adgregenic
-beta2-adregenic
-calmodulin
-insulin
-cortisol

A

Insulin

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60
Q

True or False:

Two molecules of insulin must bind to the insulin receptor for activation to occur.

A

False

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61
Q

Assume the mass of a phospholipid is approximately 1,000 g/mol and that mass of an average protein is 50 kDa (50,000 g/mol). If the ratio of protein mass to lipid mass in a cell membrane is 1:1, what is the approximate molar ratio of lipid to protein in the membrane?

-50:1
-1:50
-1:5
-500:1
-5:1

A

50:1

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62
Q

A phospholipid contains a ______ head group which can form _______ bonds with peripheral proteins. The phosphate group on the phospholipid may interact with ______ amino acids in peripheral proteins.

A

-hydrophilic
-ionic
-polar

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63
Q

The removal of an integral membrane protein from the plasma membrane is a ______ process. Therefore, the value for delta G would be ______.

A

unfavorable; positive

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64
Q

When an organism undergoes large temperature fluctuations, it must maintain its membrane fluidity. At elevated temperatures, the membrane can become too ______ whereas, at lower temperatures, the membrane can become too _______. The addition of cholesterol to the membrane can mitigate these changes because the planar structure _______ fatty acyl tail packing at elevated temperatures and ______ their packing at lower temperatures.

A

-fluid
-rigid
-increases
-decreases

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65
Q

The perilipins (a family of lipid droplet proteins) were originally identified as proteins that stayed associated with the lipid droplet when washed with sodium carbonate (100 mM, pH 9.0). Based on this observation describe a model for the association of the perilipins with the lipid storage droplet.

-Perilipins bind to GPI anchors
-Perilipins are monotopic integral membrane proteins
-Perilipins bind to acylated proteins
-Perilipins associate with phosphatidylinositol phosphate head groups

A

Perilipins are monotopic integral membrane proteins

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66
Q

If a cell membrane is disrupted by physical or chemical methods, the hydrophobic interior of the lipid bilayer will be exposed to water, which is energetically ________. In such circumstances, a(n) ______ in delta S would occur and lead to a(n) _______ in delta G for the overall process. However, a reorganization into vesicles increases the randomness of water, which is thermodynamically ________.

A

-unfavorable
-decrease
-increase
-favorable

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67
Q

Glutaminase ________.

-is downregulated during times of starvation
-liberates ammonia from glutamate
-is important to the citric acid cycle by its importance to the production of alpha-ketoglutarate
-liberates ammonia from glutamine

A

liberates ammonia from glutamine

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68
Q

Which is NOT true of physiological ammonia?

-It can permeate the blood-brain barrier.
-It lowers blood pH, making it difficult to transport CO2
-It blocks energy production in the brain
-It shunts neuron metabolism away from the synthesis of protective neurotransmitters.

A

It lowers blood pH, making it difficult to transport CO2

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69
Q

The _____ gradient is used in the proximal tubule to drive the reabsorption of ____ via a symporter.

-Na+; water
-K+; water
-K+; glucose
-Na+; glucose
-Both A and B

A

Na+; glucose

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70
Q

In the loop of Henle, antidiuretic hormone works through cAMP and PKA to facilitate water reabsorption via ______.

-aquaporin upregulation
-aquaporin incorporation into the plasma membrane
-Na+/K+ ATPase upregulation
-Na+/glucose symporter upregulation

A

aquaporin incorporation into the plasma membrane

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71
Q

The amino acids Ala, Cys, Gly, and Ser are all degraded to the metabolic intermediate ______ and are considered ______.

-pyruvate; glucogenic
-acetyl-CoA; ketogenic
-acetyl-CoA; glucogenic
-acetoacetate; ketogenic
-pyruvate; ketogenic

A

pyruvate; glucogenic

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72
Q

Intestinal enterocytes employ transporters that ______.

-depend on active transport mechanisms
-can move individual amino acids only into the bloodstream
-rely only on the concentration gradient of nutritional amino acids in the intestinal lumen
-are also peptidases
-are symporters coupled with Na+ gradients to drive amino acid absorption

A

are symporters coupled with Na+ gradients to drive amino acid absorption

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73
Q

_______ are involved in the nonselective degradation of proteins in well-nourished cells.

A

Lysosomes

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74
Q

To provide glucose for the brain and other tissues in times of starvation, the liver transaminates ______.

-alanine
-pyruvate
-alpha-ketoglutarate
-glutamate
-glutamine

A

alanine

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75
Q

Which is NOT true of glutamine?

-It is derived directly from glutamate.
-It is the amino acid found in the highest concentration in the blood.
-Its synthesis is catalyzed by glutamate dehydrogenase.
-Alpha-ketoglutarate is a precursor.
-It assists in the detoxification of ammonia.

A

Its synthesis is catalyzed by glutamate dehydrogenase.

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76
Q

Where in the human body do the reactions of the urea cycle take place?

-adipocytes
-hepatocytes
-myocytes
-erythrocytes
-pancreas

A

hepatocytes

(In the liver)

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77
Q

Fatty acids are considered amphipathic, meaning ______.

-they are ionized at pH 7.4
-they are not part of an ester or an amide
-they contain both hydrophobic and hydrophilic groups
-they form micelles

A

they contain both hydrophobic and hydrophilic groups

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78
Q

Which of the following is NOT part of a glycerophospholipid?

-Glycerol
-Phosphate
-Fatty acid
-Triacylglycerol
-Polar head group

A

Triacylglycerol

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79
Q

Fatty acid metabolism releases significant energy because ______.

-It encourages the citric acid cycle through the production of acetyl-CoA
-through the beta-oxidation process, reduced coenzymes (NADH and FADH2) are formed and can charge the electron transport chain
-fatty acid carbons enter metabolism through anaplerotic pathways into glycolysis
-A and B

A

A and B

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80
Q

Which of the following correctly identifies the four reactions of the beta-oxidation and their sequence?

-reduction, hydration, reduction, thiolysis
-decarboxylation, dehydration, dehydration, thiolysis
-oxidation, dehydration, oxidation, thiolysis
-oxidation, hydration, oxidation, thiolysis

A

oxidation, hydration, oxidation, thiolysis

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81
Q

Why does the catabolism of fat produce more energy than an equivalent mass of carbohydrates?

-Carbohydrate is catabolized anaerobically.
-Carbohydrate catabolism involves substrate-level phosphorylation.
-Fat catabolism leads to the formation of thioesters.
-Fat catabolism produces more reduced cofactors per gram.

A

Fat catabolism produces more reduced cofactors per gram.

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82
Q

If the fatty acid 16:0 is catabolized completely, to carbon dioxide and water, the net yield of ATP per molecule of fatty acid is:

(Assume that re-oxidation of NADH via the electron transport chain yields the equivalent of 2.5 ATP, and that re-oxidation of FADH2 yields 1.5 ATP)

A

106 ATP

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83
Q

Which of the following statements about high intracellular levels of citrate is TRUE?

-It inhibits gluconeogenesis
-It depolymerizes acetyl CoA-carboxylase (ACC)
-It supplies the bicarbonate required for the synthesis of malonyl-CoA
-It activates ACC

A

It activates ACC.

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84
Q

Among the first steps in cholesterol biosynthesis is the production of acetoacetyl-CoA, which ______.

-is a product of HMG-CoA reductase
-occurs in the mitochondrion
-requires the oxidation of NADPH
-is also the first step in ketone body biosynthesis

A

is also the first step in ketone body biosynthesis

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85
Q

Which of the following statements about acetoacetate and 3-hydroxybutyrate is FALSE?

-They are fuels for the brain and skeletal muscles.
-They are synthesized in liver mitochondria
-They may be regarded as water-soluble, transportable forms of citrate in the blood
-They give rise to acetone
-They require acetyl-CoA for their synthesis

A

They may be regarded as water-soluble, transportable forms of citrate in the blood

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86
Q

In which cellular compartment does the following reaction take place:

HMG-CoA + 2 NADPH –> mevalonate + 2 NADP+ + acetyl-CoA

-cytosol of liver cells
-mitochondria of liver cells
-cells in the intestinal lumen
-lysosomal fluid
-all of the above

A

cytosol of liver cells

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87
Q

Which enzyme catalyzes the key regulatory step of cholesterol synthesis?

-Beta-ketothiolase
-HMG-CoA synthase
-HMG-CoA reductase
-mevalonate-5-phosphotransferase
-phenyltransferase

A

HMG-CoA reductase

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88
Q

Eicosanoids are 20-carbon compounds derived from _____.

A

arachidonic acid

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89
Q

________ and _______ have the appropriate geometry to form lipid bilayers whereas ______ tends to form micelles.

A

-glycerophospholipids
-sphingolipids
-fatty acids

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90
Q

Rank the melting points of the following fatty acids from highest to lowest:

  1. cis-oleic (18:1)
  2. lauric (12:0)
  3. linoleic (18:2)
  4. stearic (18:0)
  5. palmitic (16:0)
A

4 > 5 > 2 > 1 > 3

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91
Q

Unsaturated fatty acids ______.

-are commonly found in plants
-usually contain a double bond with cis stereochemistry
-sometimes contain multiple double bonds
-have lower melting points than the analogous saturated fatty acids
-all of the above

A

all of the above

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92
Q

Which of the following is composed primarily of fatty acids and other single-tailed amphiphiles?

-lipid bilayers
-two-dimensional membranes
-liposomes
-micelles
-solvent-filled vesicles

A

micelles

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93
Q

Which of the following statements describes one reason that plant oils are generally healthier for human consumption than animal fats?

-Plant oils usually contain more unsaturated fatty acids than animal fats.
-Plant oils usually contain more trans fatty acids than animal fats.
-Plant oils usually have more saturation than animal fats.
-Plant oils are glycerol based rather than phospholipid based.
-Plant oils have shorter chain fatty acids than animal fats.

A

Plant oils usually contain more unsaturated fatty acids than animal fats.

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94
Q

A type of lipid that commonly forms a waterproof barrier and is composed of a fatty acid and a fatty alcohol is called a _____.

-terpenoid
-ganglioside
-capsaicin
-steroid
-wax

A

wax

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95
Q

Which of the following lipid types is the least polar?

-triacylglycerols
-glycerophospholipids
-sphingolipids
-gangliosides
-glycolipids

A

triacylglycerols

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96
Q

The major lipid component of cell membranes are ______.

-triacylglycerols
-cholesterols
-glycerophospholipids
-plasmalogens
-gangliosides

A

glycerophospholipids

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97
Q

Triglycerides contain more metabolic energy per unit weight glycogen because ______.

-glycogen has greater polarity than fatty acids
-fatty acids predominate in an anhydrous form
-fatty acids are less oxidized than carbohydrates
-triglycerides have a higher average molecular mass

A

-glycogen has greater polarity than fatty acids
-fatty acids predominate in an anhydrous form
-fatty acids are less oxidized than carbohydrates

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98
Q

What is the product of fatty acid activation?

-acyl adenylate
-pyrophosphate
-acyl-CoA
-acyl ester
-acyl-carnitine

A

acyl-CoA

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99
Q

What coenzyme is required for the complete beta-oxidation of a polyunsaturated fatty acid?

-NADPH
-NADP+
-NADH
-FADH2
-All of the above

A

NADPH

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100
Q

Each round of beta-oxidation of a saturated fatty acyl-CoA produces ________.

-1 NADH, 1 FADH2, 1 CO2, 1 acetyl-CoA
-1 NADH, 1 FADH2, 1 acetyl-CoA
-1 NADH, 1 FADH2, 2 acetyl-CoA
-1 NADH, 1 FADH2, 1 H2O, 1 acetyl-CoA
-2 NADH, 1 FADH2, 1 acetyl-CoA

A

1 NADH, 1 FADH2, 1 acetyl-CoA

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101
Q

What is the net production of ATP from complete catabolism of the following fatty acid to CO2 and H2O?

  • <50
  • 51-90
  • 91-120
    -121-150
  • 151+
A

51-90

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102
Q

What are the beta-oxidation products of stearic acid, a saturated fatty acid with 18 carbons?

-9 NADH, 9 FADH2, 9 acetyl-CoA
-9 NADH, 8 FADH2, 9 acetyl-CoA
-8 NADH, 9 FADH2, 9 acetyl-CoA
-8 NADH, 8 FADH2, 9 acetyl-CoA
-8 NADH, 7 FADH2, 9 acetyl-CoA

A

8 NADH, 8 FADH2, 9 acetyl-CoA

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103
Q

Fatty acid oxidation occurs in the ______.; Fatty acid synthesis occurs in the _______.

-mitochondria; cytosol
-mitochondria; lysosome
-lysosome; Golgi apparatus
-cytosol; Golgi apparatus
-mitochondria; endoplasmic reticulum

A

mitochondria; cytosol

104
Q

Which enzyme is the rate-determining step for fatty acid synthesis?

-ATP-citrate lyase
-trans acylase
-3-ketoacyl-ACP reductase
-3-hydroxyacyl-ACP dehydrate
-acetyl-CoA carboxylase

A

acetyl-CoA carboxylase

105
Q

The activation of acetyl-CoA for fatty acid synthesis is achieved by converting the acetyl-CoA into _____.

-propionyl-CoA
-malonyl-CoA
-acetoacetyl-CoA
-HMG-CoA
-Beta-hydroxybutryl-CoA

A

malonyl-CoA

106
Q

Which of the following statements are TRUE regarding fatty acids?

-Fatty acids with fewer than 14 carbons are the most common
-Synthesis of fatty acid occurs in 2 carbon units
-Fatty acids with conjugated double bonds are the most common type of fatty acid.
-In higher plants and animals, C16 and C18 species predominate

A

-Synthesis of fatty acid occurs in 2 carbon units
-In higher plants and animals, C16 and C18 species predominate

107
Q

Whereas fatty acids are most often formed by the condensation of _____ -carbon units, isoprenoids are assembled from ______-carbon units.

-5, 3
-4, 2
-2, 3
-2, 5
-3, 4

A

2, 5

108
Q

If a reaction that included all of the enzymes involved in fatty acid synthesis was supplied with excess ATP, NADPH, acetyl-CoA, and 14CO2 (where the carbon was a 14C-label), where would the labeled carbon appear in the finished fatty acid?

-odd-numbered carbons
-even-numbered carbons
-every third carbon
-every fifth carbon
-no carbons would be labeled

A

no carbons would be labeled

109
Q

Ketone bodies are produced in the ____ and used by the _____ only under conditions such as a prolonged fast.

-liver; heart
-liver; brain
-liver; skeletal muscle
-kidneys; heart
-kidneys; brain

A

liver; brain

110
Q

In which location listed below does the following reaction take place?

HMG-CoA –> acetoacetate + Acetyl-CoA

-cytosol of cardiomyocytes
-mitochondria of cardiomyocytes
-cytosol of liver cells
-mitochondria of liver cells
-all of the above

A

mitochondria of liver cells

111
Q

Which of the following diets would most likely promote the formation of ketone bodies?

-high simple carbohydrates, low fat
-high complex carbohydrates, high fructose
-high fat, high protein, low carbohydrate
-low fat, high protein, high complex carbohydrates
-high fructose, high whole-grain carbohydrates

A

high fat, high protein, low carbohydrate

112
Q

Which of the following is the starting metabolite in ketone body biosynthesis?

-Acetyl-CoA
-malonyl-CoA
-propionyl-CoA
-acetyl-CoA and propionyl-CoA
-acetyl-CoA and malonyl-CoA

A

Acetyl-CoA

113
Q

Which of the following is the primary building block for the synthesis of molecules such as cholesterol or ubiquinone?

-phosphatidylcholine
-palmitic acid
-choline
-isoprene
-sphingosine

A

isoprene

114
Q

What class of lipid is squalene, the precursor to cholesterol?

-isoprenoid
-fatty acid
-steroid
-wax
-triacylglycerol

A

isoprenoid

115
Q

If one molecule of stearic acid (18:0) was catabolized by beta-oxidation, how many molecules of the following would be produced?

  1. Acetyl-CoA
  2. FADH2
  3. NADH/H+
A
  1. Acetyl-CoA: 9 molecules
  2. FADH2: 8 molecules
  3. NADH/H+: 8 molecules
116
Q

Beta-oxidation and fatty acid biosynthesis are conserved pathways among many organisms. How have these organisms evolved to ensure both pathways do not occur at the same time?

-Both pathways occur in the cytosol. The cell can therefor recognize the activation of enzymes specific to each pathway and can prevent the activation of the opposing pathway.
-Both pathways occur in the mitochondria. The cell can therefore utilize energy from the Krebs cycle to inhibit the opposing pathway.
-Beta-oxidation occurs in the mitochondria and fatty acid biosynthesis occurs in the cytosol. This compartmentalization prevents activation of both pathways simultaneously.
-Beta-oxidation occurs in the cytosol and fatty acid biosynthesis occurs in the mitochondria. This compartmentalization prevents activation of both pathways simultaneously.
-Rapid energy depletion promotes beta-oxidation in the cytosol. If there is not sufficient energy stored at that time, fatty acid biosynthesis will be promoted in the mitochondria. This compartmentalization allows activation of both pathways during such extreme circumstances.

A

Beta-oxidation occurs in the mitochondria and fatty acid biosynthesis occurs in the cytosol. This compartmentalization prevents activation of both pathways simultaneously.

117
Q

Phospholipases are important to

-Sphingomyelin head group exchange
-eicosanoid biosynthesis
-generation of some second messengers
-fatty acid liberation

A

-eicosanoid biosynthesis
-generation of some second messengers
-fatty acid liberation

118
Q

______ are a class of amphipathic molecules that comprise the major lipid components of the cell membrane.

A

Glycerophospholipids

119
Q

Lingual and gastric lipases ________.

-produce glycerol + free fatty acids
-may produce either diacyl- or monoacyl-glycerol + free fatty acids
-require metallic cofactors
-are more efficient than pancreatic lipases
-are optimally catalytic at alkaline pH

A

produce glycerol + free fatty acids

120
Q

Which of the following terms is used to describe the breakdown of triacylglycerol into free fatty acids and glycerol?

-Lipolysis
-Lipogenesis
-Beta oxidation
-A and B
-A and C

A

Lipolysis

121
Q

Most important to efficient passage of dietary lipids into lymphatic circulation is ______.

-enterocyte plasma membrane patency
-pancreatic lipase efficiency
-transporters
-the presence of bile

A

the presence of bile

122
Q

High-density lipoprotein (HDL) is produced in the _____ and has a very high _____ ratio of the lipoproteins.

-liver; protein-to-lipid
-liver; lipid-to-protein
-blood; protein-to-lipid
-intestine; lipid-to-protein
-blood; lipid-to-protein

A

liver; protein-to-lipid

123
Q

Chylomicrons ______.

-are direct precursors to VLDLs
-deliver fatty acids directly to liver
-deliver fatty acids directly to adipose tissue and muscle
-are coated in amphipathic phospholipids
-are built in hepatocytes

A

deliver fatty acids directly to adipose tissue and muscle

124
Q

Excess dietary carbohydrates and amino acids _____.

-travel through the bloodstream attached to proteins
-are converted to phospholipids in the liver
-are packaged with phospholipids and triacylglycerols into chylomicrons
-are converted into triacylglycerols in the liver
-make up VLDLs

A

are converted into triacylglycerols in the liver

125
Q

Your patient has low serum albumin. The physician should NOT be concerned about…

-blood osmotic pressure
-thyroid hormone transport through the bloodstream
-protein and cell membrane denaturation due to free fatty acids circulating unaided
-the possibility that drug concentrations are no longer effective
-liver issues that may have resulted in lowered albumin biosynthesis

A

thyroid hormone transport through the bloodstream

126
Q

The chylomicra enter the _____ tissues by passing through capillary beds in those tissues. The endothelial cells in these beds contain ______, which degrade triacylglycerols found in chylomicra.

A

-muscle and adipose
-lipoprotein lipase

127
Q

When excess carbohydrates and amino acids are consumed in the diet, what occurs?

-Carbohydrates are the primary energy source and so are broken down for energy in processes such as glycolysis. Amino acids are stored as long peptides until required for energy.
-Excess carbohydrates enter glycolysis, and excess amino acids enter the urea cycle.
-Excess carbohydrates and amino acids are converted into triacylglycerols.
-Excess carbohydrates and amino acids are converted into cholesterol.

A

Excess carbohydrates and amino acids are converted into triacylglycerols.

128
Q

What is the primary purpose of high-density lipoproteins (HDLs)?

-HDLs package triacylglycerols into their core and transport them to the muscle and adipose tissue for breakdown by lipoprotein lipase.
-HDLs become remnants after depositing triacylglycerols and go on to bind to the liver remnant receptors.
-HDLs become LDLs, then bind to LDL receptors on the liver as they transport cholesterol.
-HDLs package cholesterol into their core and transport them to the muscle and adipose tissue for breakdown by lipoprotein lipase.
-HDLs transport excess cholesterol from circulation back to the liver for recycling and to prevent buildup in arteries.

A

HDLs transport excess cholesterol from circulation back to the liver for recycling and to prevent buildup in arteries.

129
Q

Which of the following lipoprotein particles has the greatest relative content (percent weight) of TAGs?

-CM
-VLDL
-LDL
-HDL

A

CM

(CM contains approximately 80-90% of TAGs.)

130
Q

What are the steps involved in receptor-mediated endocytosis?

A
  1. Ligand binds to the receptor.
  2. Ligand-bound receptors cluster together.
  3. Binding of a structural protein forms a pit.
  4. Motor proteins bind to the complex.
  5. The complex is now considered a vesicle.
  6. The structural protein coat is removed.
  7. Early endosome enters the endocytic pathway.
131
Q

True or False:

Triacylglycerols are synthesized in the liver and adipose tissue using 2-monoacylglycerol as the source of the glycerol backbone.

A

False

132
Q

True or False:

In enterocytes, 2-monoacylglycerol is the source of the glycerol backbone for triacylglycerol synthesis.

A

True

133
Q

True or False:

Liver tissue synthesizes triacylglycerols de novo using acetyl-CoA from glycolysis as the starting molecule.

A

True

134
Q

True or False:

Adipose tissue contains substantial amounts of glycerol kinase, which promotes the production of glycerol-3-phospahte, an intermediate in triacylglycerol synthesis.

A

False

135
Q

True or False:

Liver tissue contains substantial amounts of glycerol kinase, which promotes the production of glycerol-3-phospahte, an intermediate in triacylglycerol synthesis.

A

True

136
Q

A phospholipid monolayer coating a core of triacylglycerols or cholesteryl esters describes ______.

-lipid storage droplets
-adipocyte structure
-micelles
-coated vesicles
-chylomicrons

A

lipid storage droplets

137
Q

Important to hormonal control of lipolysis is/are…

-G protein-coupled receptors
-cholesterol
-perilipin
-PKA

A

-G protein-coupled receptors
-perilipin
-PKA

138
Q

Which of the following statements about lipolysis in adipocytes is TRUE?

-Its rate is determined by the supply of substrate.
-Its rate is increased when the rate-limiting enzyme is dephosphorylated
-It results in the release of triacylglycerols into the bloodstream.
-It is increased in response to glucagon signal.

A

It is increased in response to glucagon signal.

139
Q

Where are triacylglycerols stored in humans under normal conditions?

-Myocytes
-Adipocytes
-Hepatocytes
-Liver cells

A

Adipocytes

140
Q

Which is NOT important to the decreased fluidity of lipid rafts?

-They are enriched in cholesterol.
-The fatty acids that makeup sphingomyelin are saturated.
-They are mostly comprised of phosphatidylcholine with unsaturated fatty acids.
-Cholesterol and membrane lipids facilitate close molecular packing.
-Polar head groups strongly interact through hydrogen bonding.

A

They are mostly comprised of phosphatidylcholine with unsaturated fatty acids.

141
Q

Caveolar rafts and coated pits are similar in that both ______.

-form plasma membrane invaginations
-form intracellular vesicles
-incorporate the same plasma membrane proteins
-maybe involved in cell signaling via membrane proteins

A

-form plasma membrane invaginations
-maybe involved in cell signaling via membrane proteins

142
Q

Which of the following lipids would NOT likely be found in a lipid raft?

-glycosphingolipids
-glycerophospholipids
-cholesterol
-palmitoleic acid

A

-glycerophospholipids
-palmitoleic acid

143
Q

Which of the following alcohols is esterified to the phosphate group of glycerophospholipids?

-choline
-ethanolamine
-glycerol
-serine
-all of the above

A

all of the above

144
Q

Which two molecules are used in the synthesis of sphingosine?

-arachidonic acid and serine
-stearic acid and isoprene
-palmitoyl-CoA and choline
-linoleoyl-CoA and isoprene
-palmitoyl-CoA and serine

A

palmitoyl-CoA and serine

145
Q

Sphinganine is an intermediate in the synthesis of which of the following?

-ceramides
-sphingomyelins
-cerebrosides
-prostaglandins

A

-ceramides
-sphingomyelins
-cerebrosides

146
Q

To oxidize the fatty acids in a triacylglycerol, what must occur first?

-fatty acid activation
-lipolysis
-transport into the mitochondria
-oxidation of a carbon-carbon single bond to an alkene
-none of the above

A

lipolysis

147
Q

Digestion of triacylglycerols is aided by the cholesterol derivatives synthesized by the liver known as _____.

-bile acids
-lipoproteins
-lanosterols
-chylomicrons
-colipases

A

bile acids

148
Q

Which of the following would result in a net increase in uptake of LDL by the liver?

-increased availability of HDL receptors
-high levels of cholesterol synthesis
-increased availability of clathrin triskelions
-all of the above
-none of the above

A

high levels of cholesterol synthesis

149
Q

Accurately rank the lipoproteins from highest to lowest density.

A

HDL > LDL > IDL > VLDL > chylomicrons

150
Q

Pepsinogen _______.

-catalyzes the catabolism of peptides
-is an aspartyl protease
-is activated by the high pH of the duodenum
-is categorized as a zymogen

A

-is an aspartyl protease
-is categorized as a zymogen

151
Q

Omeprazole and Lansoprazole treat excess stomach acid by ______.

-inhibiting zymogens
-stimulating the secretion of mucus
-inhibiting proton pumps in the stomach
-neutralizing stomach acids
-decreasing histamine synthesis

A

inhibiting proton pumps in the stomach

152
Q

What is a zymogen?

-Cofactor necessary for enzyme synthesis
-Factor that promotes the expression of an enzyme
-Particle that delivers an enzyme to its active location
-Cofactor necessary for enzyme function
-Inactive enzyme precursor

A

Inactive enzyme precursor

153
Q

Which is NOT true of physiological ammonia?

-It can permeate the blood-brain barrier.
-It lowers blood pH, making it difficult to transport CO2
-It blocks energy production in the brain.
-It shunts neuron metabolism away from the synthesis of protective neurotransmitters.

A

It lowers blood pH, making it difficult to transport CO2

154
Q

In the glucose-alanine shuttle, _______ is released from muscle cells, which travels to the _______. It is then converted to glutamate by a process of ______. The glutamate is then converted to ______ by ______ and used for gluconeogenesis. The resulting glucose can then be taken up by the muscle and converted to ______ by glycolysis.

A
  1. alanine
  2. liver
  3. transamination
  4. pyruvate
  5. oxidative deamination
  6. pyruvate
155
Q

What is the major metabolic problem associated with the catabolism of amino acids?

-Amino acids are difficult to transport in the bloodstream.
-Catabolism of amino acids produces ammonia, which is toxic.
-The breakdown of amino acids requires the removal of the side chains, which are all different.
-Catabolism results in the production of excess ketone bodies, and thus ketoacidosis.

A

Catabolism of amino acids produces ammonia, which is toxic.

(All amino acids contain an alpha-amino group which must be removed and disposed of during their catabolism.)

156
Q

During the urea cycle, which two intermediates must both be transported across the inner mitochondrial membrane?

-citrulline and ornithine
-carbamoyl phosphate and ornithine
-ornithine and arginine
-citrulline and arginine
-carbamoyl phosphate and citrulline

A

citrulline and ornithine

157
Q

Which of the following amino acids is/are NOT directly involved in the urea cycle?

-Asparagine is not involved.
-Aspartate and arginine are not involved.
-Aspartate is not involved.
-Arginine is not involved.
-Asparagine and arginine are not involved.

A

Asparagine is not involved.

158
Q

In which cellular location listed below does the following reaction take place:
Arginine to urea + ornithine

-cytosol
-mitochondrial matrix
-lysosome
-either A or B
-none of the above

A

cytosol

159
Q

In which cellular location listed below does the following reaction take place:
ornithine + carbamoyl phosphate to citrulline

-cytosol
-mitochondrial matrix
-lysosome
-either A or B
-none of the above

A

mitochondrial matrix

160
Q

What species are combined to produce carbamoyl phosphate?

A

-NH3
-PO4 -3
-HCO -3

161
Q

With regard to amino acid skeleton scavenging, indicate whether the following amino acid is glucogenic, ketogenic, or both:

Lysine

A

Ketogenic

162
Q

With regard to amino acid skeleton scavenging, indicate whether the following amino acid is glucogenic, ketogenic, or both:

Phenylalanine

A

Both

163
Q

With regard to amino acid skeleton scavenging, indicate whether the following amino acid is glucogenic, ketogenic, or both:

Threonine

A

Both

164
Q

With regard to amino acid skeleton scavenging, indicate whether the following amino acid is glucogenic, ketogenic, or both:

Alanine

A

Glucogenic

165
Q

With regard to amino acid skeleton scavenging, indicate whether the following amino acid is glucogenic, ketogenic, or both:

Glycine

A

Glucogenic

166
Q

With regard to amino acid skeleton scavenging, indicate whether the following amino acid is glucogenic, ketogenic, or both:

Leucine

A

Ketogenic

167
Q

Glutamate is converted to alpha-ketoglutarate and NH4+ by a process described as…

-deamination
-hydrolysis
-oxidative deamination
-reductive deamination
-transamination

A

oxidative deamination

(This reaction results in both deamination and oxidation of the alpha-carbon atom in glutamate.)

168
Q

Xenobiotic metabolism _____.

-converts molecules to more lipid-soluble metabolites
-employs enzymes that are not used in the metabolism of endogenous molecules
-creates more hydrophilic molecules
-give rise to mainly reduced metabolites

A

creates more hydrophilic molecules

169
Q

The _____ gradient is used in the proximal tubule to drive the reabsorption of ______ via a symporter.

-Na+; water
-K+; water
-K+; glucose
-Na+; glucose
-both A and B

A

Na+; glucose

170
Q

What type of reaction is used to deaminate amino acids, resulting in a new amino acid and a new alpha-keto acid?

-ATP-dependent ligation
-Transamination
-Oxidation
-Condensation
-Reduction

A

Transamination

171
Q

Glutamate undergoes a(n) ______, catalyzed by glutamate deydrogenase, to yield alpha-ketoglutarate, NADH, and ______.

-reductive deamination; water
-oxidative deamination; ammonia
-reductive amination; water
-oxidative amination; ammonia
-none of the above

A

oxidative deamination; ammonia

172
Q

Oxidative deamination of glutamate

-generates alpha-ketoglutarate
-is inhibited by glutamate
-is activated by GTP
-eliminates the keto group from alpha-keto acids

A

generates alpha-ketoglutarate

173
Q

In high levels, ammonia is toxic to _____ cells.

-kidney
-cardiac
-liver
-nerve
-intestinal

A

nerve

174
Q

Which of the following citric acid cycle intermediates can be converted to aspartate via transamination?

-succinate
-fumarate
-alpha-ketoglutarate
-citrate
-oxaloacetate

A

oxaloacetate

175
Q

Which of the following contains the correct sequence of reactants for carbamoyl phosphate synthetase?

-ATP and ammonia, then bicarbonate, then ATP
-ATP and ammonia, then ATP, then bicarbonate
-ATP and bicarbonate, then ammonia, then ATP
-ATP and bicarbonate, then ATP, then ammonia
-ammonia and bicarbonate, then 2 ATP molecules

A

ATP and bicarbonate, then ammonia, then ATP

176
Q

Which urea cycle intermediate reacts with carbamoyl phosphate?

-citrulline
-aspartate
-argininosuccinate
-arginine
-ornithine

A

ornithine

177
Q

Degradation to pyruvate makes an amino acid ______; degradation to acetoacetate makes an amino acid ________.

-glucogenic; glucogenic
-glucogenic; glucogenic and ketogenic
-glucogenic; ketogenic
-ketogenic; glucogenic
-ketogenic; ketogenic

A

glucogenic; ketogenic

178
Q

Which of the following reaction sequences could result in glucose synthesis?

-fumarate –> arginine –> urea
-fumarate –> malate –> oxaloacetate
-citrulline –> urea –> aspartate
-urea –> arginine –> ornithine
-none of the above

A

fumarate –> malate –> oxaloacetate

179
Q

Which of the following statements about phenylalanine is(are) true?

-The enzymatic degradation of phenylalanine requires the tetrahydrobiopterin cofactor
-Individuals with defects in phenylalanine catabolism requires tyrosine in their diet.
-An inability to hydroxylate phenylalanine results in increased blood levels of phenylalanine, causing mental disability.
-A and C
-A, B, and C

A

A and C

180
Q

Attacks the N-terminus

A

Aminopeptidase

181
Q

Uses proteins as substrates

A

Aminopeptidase

182
Q

Trypsin is an example

A

Serine protease

183
Q

Breaks down short peptides

A

Peptidase

184
Q

Cleaves C-terminal amide bonds

A

Aspartyl protease

185
Q

Pepsin is an example

A

Aspartic protease

186
Q

In the course of a hypothetical meal, the stomach expands from 0.25 liters to 1.25 liters. If we assume that no buffering occurs, and no acid is produced from the stomach contents, how much acid must be secreted to maintain pH=10?

How many grams of ATP would be consumed in the production of that acid?

A

0.1 mole and 507 grams of ATP

187
Q

The pKa of the amino and carboxyl groups on alanine are 9.9 and 2.4, respectively. Under physiological conditions (pH 7.4), what percentage of alanine is ionized?

A

100%

188
Q

Alanine has a hydrophobic side chain. Would you anticipate the solubility of this amino acid in plasma to be a problem?

-Yes, hydrophobic groups like methyl groups are insoluble in water.
-Yes, the other components of plasma (ions and proteins) decrease the solubility of amino acids.
-No, the methyl group is small compared to the size of water.
-No, all amino acids have charged amino and carboxyl groups at physiological pH.

A

No, all amino acids have charged amino and carboxyl groups at physiological pH.

189
Q

In obligate carnivores, are carbon skeletons truly scavenged? What is the fate of these carbons? Select all that apply.

-New protein synthesis
-Oxidation via citric acid cycle
-Fatty acid biosynthesis
-Gluconeogenesis

A

-Oxidation via citric acid cycle
-Gluconeogenesis

190
Q

Many humans are vegetarians or vegans whereas others eat large quantities of meat or fish. Can those people adapt their nitrogen metabolism to their specific diet, as other species discussed in this chapter have?

-Nitrogen metabolism is relatively fixed. They cannot alter gene expression to up-or-down-regulate pathways, cannot change the architecture of their kidneys, or change the fundamental properties of enzymes.
-Nitrogen metabolism is somewhat flexible. They can alter gene expression to up-or-down-regulate pathways, but cannot change the architecture of their kidneys or change the fundamental properties of enzymes.
-Nitrogen metabolism is somewhat flexible. They cannot alter gene expression to up-or-down-regulate pathways, but can gradually change the architecture of their kidneys or change the fundamental properties of enzymes.
-Nitrogen metabolism is highly adaptable. Over time they alter gene expression to up-or-down-regulate pathways and can change the architecture of their kidneys and change the fundamental properties of enzymes.

A

Nitrogen metabolism is somewhat flexible. They can alter gene expression to up-or-down-regulate pathways, but cannot change the architecture of their kidneys or change the fundamental properties of enzymes.

191
Q

Which reactions of phase I and phase II metabolism require energy, and where does this energy come from (in what molecular form)?

-Phase I: ATP, Phase II: Activated carriers
-Phase I: ATP, Phase II: Reactions are energetically favorable
-Phase I: NADPH, Phase II: Activated carriers
-Phase I: NADH, Phase II: Glucuronic Acid

A

Phase I: NADPH, Phase II: Activated carriers

192
Q

Cells with large numbers of Na+ pumps often have more mitochondria. Why might this be the case?

-Pumps are encoded by mitochondrial genes.
-Pumps require cytochrome for activity
-Pumps require ATP for activity
-Mitochondria use Na+ as a counterion in many reactions

A

Pumps require ATP for activity

193
Q

About 70% of a small molecule is cleared in one pass of the kidney. What does this tell us about how this molecule is being treated in the kidney?

-The kidney is likely employing active transport to resorb this molecule.
-The kidney is likely employing passive transport to resorb this molecule.
-The molecule is probably being excreted in the filtrate and not reabsorbed.
-This molecule is probably resorbed in the proximal convoluted tubule.
-The small molecule is trapped in Bowman’s capsule.

A

The molecule is probably being excreted in the filtrate and not reabsorbed.

194
Q

What is the primary role of lysosomes in protein degradation?

-To degrade rapidly turning-over proteins
-To degrade proteins from vesicles that have fused with the lysosome, such as during endocytosis.
-To degrade proteins with the KFERQ sequence
-To degrade proteins tagged by ubiquitin

A

To degrade proteins from vesicles that have fused with the lysosome, such as during endocytosis.

195
Q

The major metabolic reactions are almost evenly divided between _______. Two pathways, the ______, and _______, take place in both locations. _______ occurs in the cytosol, while fatty acid elongation and desaturation happen in the endoplasmic reticulum.

A
  1. the cytosol and the mitochondria
  2. urea cycle
  3. gluconeogenesis
  4. Fatty acid biosynthesis
196
Q

True or False:

Lactate is generated anaerobically in exercising muscle to reduce NAD+ to NADH.

A

False

197
Q

True or False:

Pyruvate can be oxidized into acetyl-CoA for the citric acid cycle and oxidized to generate reducing equivalents for the electron transport chain.

A

True

198
Q

True or False:

Ketone bodies are formed from acetyl-CoA in times of low glucose availability. These molecules are made by the skeletal muscle providing an alternative energy source to the muscles and brain.

A

False

199
Q

True or False:

Alanine is made in muscle from pyruvate. It shuttles ammonia to the liver for detoxification by the urea cycle and transfers carbon atoms to the liver for gluconeogenesis.

A

True

200
Q

True or False:

Glycerol forms the backbone of triacylglycerol molecules. It is released from adipose tissue and transported to the liver for gluconeogenesis or triacylglycerol formation.

A

True

201
Q

In an attempt to lose weight, many people follow a high-fat, high-protein, low-carbohydrate diet. Which of the following substances would NOT have an increased concentration in the blood after two weeks on this diet?

-urea
-insulin
-amino acids
-fatty acids
-ketone bodies

A

insulin

(A low-carbohydrate diet can decrease the concentration of glucose in the bloodstream. This would decrease the secretion of insulin and so the concentration of insulin in the bloodstream would NOT increase.)

202
Q

In a well-fed state, brain cells use which one of the following compounds circulating in the bloodstream almost exclusively as an energy source?

-amino acids
-glucose
-insulin
-fatty acids
-ketone bodies

A

glucose

203
Q

Steroid hormones ____.

-act as transcription factors
-also include the catecholamine–type hormones
-work through transmembrane protein receptors
-are most important to energy mobilization from stores
-typically act over seconds to minutes

A

act as transcription factors

204
Q

Amino acids catabolized in muscle generate _____.

-leucine
-glycine
-glutamine
-glutamate
-alanine

A

alanine

205
Q

Which of the following does NOT correctly describe insulin’s role in human metabolism?

-Insulin results in fatty acids being stored as fat in adipocytes.
-Insulin activates glycogenolysis
-Insulin is released in response to high blood glucose
-Insulin activates phosphatases.

A

Insulin activates glycogenolysis

(Insulin is released when blood glucose levels are high. It signals that glucose is available in the blood for use as fuel and for storage as glycogen. Glycogenolysis is the breakdown of stored glycogen and it is, therefore, not activated by insulin.)

206
Q

Mice lacking the protein _____ are genetically obese.

A

leptin

207
Q

In type 2 diabetes ______.

-intracellular signal pathways are defective
-there is a lack of insulin
-target cell receptors are defective
-target cell receptors are inadequate in number
-genetics seems to be the most important to disease development

A

intracellular signal pathways are defective

208
Q

Which of the following metabolic pathways occurs exclusively in the cytosol?

-citric acid cycle
-amino acid degradation
-ketogenesis
-urea cycle
-fatty acid synthesis

A

fatty acid synthesis

209
Q

Which is NOT true of metabolic pathways?

-Metabolic pathways occur in the cytosol and mitochondria.
-Most metabolic pathways do not require metabolic oxygen.
-Carbohydrate, amino acid, and lipid metabolism overlap through acetyl-CoA and the citric acid cycle
-The endoplasmic reticulum is important to amino acid metabolism.

A

The endoplasmic reticulum is important to amino acid metabolism.

210
Q

Glycolysis _____.

-occurs in the cytosol of all known cells
-describes the metabolism of glucose to pyruvate
-requires reduction of NAD+ to NADH
-can yield lactic acid under anaerobic conditions
-all of the above

A

all of the above

211
Q

Pyruvate _____.

-yields alanine following transamination from other amino acids
-can be oxidized to acetyl-CoA
-can be carboxylated to produce oxaloacetate
-gives rise to lactate during anaerobic conditions
-all of the above

A

All of the above

212
Q

Muscle is fueled by _____.

-carbohydrates through glycolysis/citric acid cycle/electron transport
-chylomicrons, VLDLs, and free fatty acids
-amino acid skeletons
-both A and B
-All of the above

A

both A and B

213
Q

Which is NOT true of peptide hormones?

-In their active form, they all comprise fewer than 4 amino acids.
-They are often synthesized as a prohormone.
-Their active form is processed and secreted through the endomembrane system.
-They work through transmembrane protein receptors.
-They are similar to neuronal signaling peptides.

A

In their active form, they all comprise fewer than 4 amino acids.

214
Q

Thyroid and steroid hormones work by binding to a nuclear hormone receptor in the _____. Binding of the hormone to the receptor ____ the receptor. This facilitates translocation to the _____, binding of _____, and _____ regulation of specific genes.

A
  1. Cytosol
  2. Activates
  3. Nucleus
  4. DNA
  5. Transcriptional
215
Q

What hormone is affected by Diabetes insipidus?

Symptoms: Decreased sodium reabsorption and excessive urination

A

Vasopressin

216
Q

What hormone is affected by Diabetes mellitus?

Symptoms: Inability of cells to uptake glucose

A

Insulin

217
Q

What hormone is affected by Addison’s disease?

Symptoms: Mineral imbalance and hypoglycemia

A

Corticosteroids

218
Q

What hormone is affected by Cushing’s disease?

Symptoms: Elevated corticosteroids and weight gain

A

ACTH

219
Q

What hormone is affected by Hashimoto’s disease?

Symptoms: Autoimmune attack resulting in weight gain

A

Thyroid hormone

220
Q

What hormone is affected by Grave’s disease?

Symptoms: Weight loss and increased metabolic rate

A

Thyroid hormone

221
Q

The endocrine glands secrete _____ which results in numerous cellular responses.

A

hormones

222
Q

Which of the following proteins stimulates the appetite?

-leptin
-ghrelin
-adiponectin
-insulin
-PYY3-36

A

ghrelin

223
Q

Among treatments for diabetes, _____.

-insulin can be used for any type of diabetes
-sulfonylureas can encourage insulin secretion
-metformin can regulate genes involved in lipid metabolism
-thiazolidinediones activate AMPK, which inhibits glycolysis

A

insulin can be used for any type of diabetes

224
Q

Which is NOT true of the Warburg effect?

-It may cause changes in gene expression in cancer cells.
-Cancer cells ferment pyruvate to CO2 and ethanol, even in the presence of oxygen.
-It may have evolved to allow cancer cells to grow under reduced oxygen conditions.
-Glycolysis does not result in acetyl-CoA production in cancer cells.
-By silencing mitochondria, cancer cells may avoid apoptosis.

A

Cancer cells ferment pyruvate to CO2 and ethanol, even in the presence of oxygen.

225
Q

Obesity can have hormonal causes, but it is generally the result of overnutrition and lack of exercise. Elevated plasma fatty acids have been implicated in the development of type 2 diabetes. How does this affect metabolism?

-The influx of fatty acids to muscle cells shifts metabolism in that tissue toward glycolysis and away from beta-oxidation. In addition, the liver is also increasing glycolysis and beta-oxidation due to elevated fatty acids.
-The influx of fatty acids to muscle cells shifts metabolism in that tissue toward beta-oxidation and away from glycolysis. In addition, the liver is also increasing beta-oxidation and gluconeogenesis due to elevated fatty acids.
-The influx of fatty acids to muscle cells shifts metabolism in that tissue toward amino acid metabolism and away from gluconeogenesis. In addition, the liver is also increasing beta-oxidation and gluconeogenesis due to elevated fatty acids.

A

The influx of fatty acids to muscle cells shifts metabolism in that tissue toward beta-oxidation and away from glycolysis. In addition, the liver is also increasing beta-oxidation and gluconeogenesis due to elevated fatty acids.

226
Q

What is the correct type of insulin-signaling disease according to the statement below:

The disease progresses as a result of the inability of cells to respond to insulin. This defect usually lies not at the level of the insulin receptor but is a post-receptor defect in signaling.

A

Type 2 diabetes

227
Q

What is the correct type of insulin-signaling disease according to the statement below:

This arises from elevated levels of pregnancy hormones influencing insulin signaling.

A

Gestational diabetes

228
Q

What is the correct type of insulin-signaling disease according to the statement below:

When the immune system of a patient recognizes the pancreatic beta cells as foreign and destroys them, this results in the loss of insulin. The causes of this are not clear.

A

Type 1 diabetes

229
Q

What is the correct type of insulin-signaling disease according to the statement below:

When plasma insulin concentrations become higher and higher, the pancreas can no longer keep up and the subject goes into beta cell failure, resulting in type 2 diabetes.

A

Insulin resistance

230
Q

Which of the following are characteristics of metabolic syndrome? Select all that apply.

-insulin resistance
-inflammation
-increased risk for type 1 diabetes
-hypersensitivity to insulin

A

-insulin resistance
-inflammation

231
Q

Which of the following metabolic pathways occurs exclusively in the cytosol?

-citric acid cycle
-ketogenesis
-urea cycle
-amino acid degradation
-fatty acid synthesis

A

fatty acid synthesis

232
Q

Animals lack the ability to produce glucose from _____.

-other sugars
-fatty acids
-pyruvate
-amino acids
-starches

A

fatty acids

233
Q

After several days of fasting, the liver begins producing relatively large amounts of ketone bodies. Which type of tissue is highly dependent upon this as its sole energy source in the absence of glucose?

-heart
-kidney
-skeletal muscle
-brain
-all of the above

A

brain

234
Q

Following prolonged starvation, ____ are used as fuel by the brain.

A

ketone bodies

235
Q

During starvation, the _____ generates as much as 50% of the body’s glucose supply.

A

kidney

236
Q

Which of the following metabolic pathways is carried out only in the liver?

-glycogen storage
-ketogenesis
-fatty acid synthesis
-triacylglycerol synthesis
-pentose phosphate pathway

A

ketogenesis

237
Q

Adipocytes convert glucose into fatty acids and ____.

-glycerol
-cholesterol
-ketone bodies
-lactate
-ribose-5-phosphate

A

glycerol

238
Q

The kidney has a small amount of glucogenic activity. Which of the following explains the source of carbon for gluconeogenesis?

-conversion of aspartate into oxaloacetate
-conversion of citrate into acetyl-CoA and oxaloacetate
-conversion of odd-chain fatty acids into succinyl–CoA
-conversion of alanine into pyruvate
-conversion of glutamine into glutamic acid, then to alpha-ketoglutarate

A

conversion of glutamine into glutamic acid, then to alpha-ketoglutarate

239
Q

In a variation of the Cori cycle, what amino acid is transported from the muscle to the liver?

-glycine
-glutamate
-aspartate
-alanine
-glutamine

A

alanine

240
Q

Aerobic activity in response to stress results in which of the following? Select all that apply.

-Glycolysis occurs in the muscle.
-Glycolysis occurs in the liver.
-Glycogenolysis occurs in the muscle.
-Glycogenolysis occurs in the liver

A

-Glycolysis occurs in the muscle.
-Glycogenolysis occurs in the muscle.
-Glycogenolysis occurs in the liver

241
Q

Which of the following can generate glucose? Select all that apply.

-kidney
-liver
-adipose tissue
-muscle

A

-kidney
-liver

242
Q

Which of the following occurs during starvation? Select all that apply.

-The kidney generates approximately half the glucose required for the body.
-The brain uses ketone bodies as a fuel source.
-The adipose tissue releases fatty acids.
-Gluconeogenesis occurs in the liver.

A

-The kidney generates approximately half the glucose required for the body.
-The brain uses ketone bodies as a fuel source.
-The adipose tissue releases fatty acids.

243
Q

During a long-term fast, which of the following is a major source of carbon for gluconeogenesis?

-lactate
-acetoacetate
-3-hydroxybutyrate
-acetone
-glycerol

A

glycerol

244
Q

Which of the following are the effects of insulin secretion? Select all that apply.

-Muscle and adipose tissue are stimulated to take up glucose.
-Glycogen synthesis increases in the liver.
-Gluconeogenesis is inhibited in the liver and kidney.
-Lipolysis increases in the adipose tissue.

A

-Muscle and adipose tissue are stimulated to take up glucose.
-Glycogen synthesis increases in the liver.
-Gluconeogenesis is inhibited in the liver and kidney.

245
Q

The beta cells of the pancreas secrete ____ in response to _____ glucose levels in the muscle and/or adipose tissue.

-insulin; low
-insulin; elevated
-glucagon; low
-glucagon; elevated
-somatostatin; elevated

A

insulin; elevated

246
Q

Pancreatic cells secrete _____ in response to ____ glucose levels in the liver.

-insulin; low
-insulin; elevated
-glucagon; low
-glucagon; elevated
-somatostatin; elevated

A

glucagon; low

247
Q

What hormone that is produced in adipose tissue signals satiety?

-adiponectin
-cholecystokinin
-leptin
-ghrelin
-amylin

A

leptin

248
Q

In a diabetic liver, which of the following pathways would be constantly active?

-glycogen synthesis
-gluconeogenesis
-fatty acid synthesis
-ketone body oxidation
-glycolysis

A

gluconeogenesis

249
Q

Which of the following statements is true regarding the blood glucose level of non-insulin-dependent diabetics compared with that of normal individuals?

Blood glucose levels of diabetics tend to be very stable, but at a higher level.
-Blood glucose levels of diabetics tend to be variable and higher.
-Blood glucose levels average the same level in diabetics, but reach higher peaks for shorter periods.
-None of the above is true.

A

Blood glucose levels of diabetics tend to be variable and higher.

250
Q

What metabolite is used in unusually high amounts by cancerous tumors?

-lactate
-glutamine
-glucose
-ketone bodies
-very long chain fatty acids

A

glucose

251
Q

The brain can use ketone bodies for fuel in times of fasting. What can muscle use in place of ketone bodies?

-glycogen
-fatty acids
-proteins
-All of the above
-None of the above

A

All of the above

252
Q

After periods of fasting, why does the liver undergo gluconeogenesis when in the re-fed state?

-In the re-fed state, glucose levels will spike, therefore gluconeogenesis will metabolize glucose to produce pyruvate and release ATP.
-In the re-fed state, excess glucose intake will promote the replenishing of glycogen stores in preparation for times when there is a lack of immediate energy sources.
-Gluconeogenesis is promoted when fatty acids are low and cannot be used as a fuel source.
-Gluconeogenesis is promoted when fatty acids accumulate in the re-fed state.

A

In the re-fed state, excess glucose intake will promote the replenishing of glycogen stores in preparation for times when there is a lack of immediate energy sources.

253
Q

Thyroid follicular cells use a sodium transporter to bring iodide ions into the cell. What type of transport mechanism is this?

-Uniporter
-Symporter
-Antiporter

A

Symporter

254
Q

What are the symptoms of hypothyroidism?

A

-Weight gain
-Low energy
-Decreased metabolic rate

255
Q

Only 5% of people with diabetes currently have type 1 diabetes. 15 years ago, 10% had it. Why is the number dropping?

-better treatments for type 1
-increased numbers of type 2 diabetics
-increased mortality rates in people with type 1
-better diagnostics

A

increased numbers of type 2 diabetics

Biochemistry (5 decks)

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