Biochem Midtern 2

fetal hemoglobin

Strong form of hemoglobin found in embryos; takes oxygen from mother's hemoglobin.

mucins (mucoproteins)

predominantly carbohydrate. serve as lubricants. N-acetylgalactosamine is usually the carbohydrate moiety bound to the protein.

Which amino acids are used for the attachment of carbohydrates to proteins?

a. asparagine b. serine c. threonine

Of the three major types of membrane lipids, which is NOT found in prokaryotes? a. phospholipids b. cholesterol c. glycolipids d. phosphoglycerides

b. cholesterol

diastereomers

isomers that are not mirror images of each other.

anabolism

reactions that require energy (synthesis of glucose, fats, or DNA)

Identify the molecule. a. NADH b. FMN c. NAD+ d. FMNH2 e. FMNH+

a. NADH

Cholesterol

the most common steroid and the precursor to biochemically active steroids. A member of the sterol class of molecules (which are steroids with an alcohol functional group)

bile salts

amphipathic molecules synthesized from cholesterol in the liver and secreted from the gallbladder in response to cholecystokinin that enhance the emulsification process. They insert into the lipid droplets making triacylglycerols more readily digested.

Carbonic anhydrase

An enzyme abundant in red blood cells that assists rapid inter-conversion of carbon dioxide and water into carbonic acid, protons and bicarbonate ions. Both hydrogen ions and carbon dioxide are also transported in the blood as bicarbonate (HCO3-) formed spontaneously or through the action of carbonic anhydrase.

Name three factors that stabilize the deoxy form of hemoglobin

BPG binding; salt bridges between acidic and basic amino acids; salt bridges that include amino-terminal carbamate

amphibolic pathways

Pathways that can be anabolic or catabolic, depending on the energy conditions in the cell.

What are the three major types of membrane lipids?

Phospholipids, sphingolipids (of which glycolipids are a subclass), and cholesterol

Phototrophs

Photosynthetic organisms that obtain energy by trapping sunlight in a chemial form

The fatty acid oleate contains 18 carbons and a cis double bond after C‑9. Which designation describes the composition and structure of oleate? a. 18:9 b. 9:18 c. 0:18 d. 18:1

d. 18:1

Oncogene

the mutated form of a proto-oncogene. The mutation of these genes that regulate cell growth lead to unrestrained growth by the cell and cancer is caused as a result.

Starch

the nutritional reservoir in plants. The storage form of glucose for plants. Consists of amylopectin (the branched form) and amylose (the unbranched form)

α-amylase

the pancreatic enzyme that digests the branched homopolymer of glucose. It cleaves the α-1,4 bonds of starch but not the 1,6 bond.

Peripheral membrane proteins

Proteins bound to the head groups of lipids or the exposed portions of integral membrane proteins by electrostatic and hydrogen bond interactions. They are anchored to the lipid bilayer by a covalently attached hydrophobic chain (fatty acid) but are not embedded within it.

α subunit and β subunit

The subunits in the quaternary structure of hemoglobin. There are two of each.

trypsinogen

the pancreatic zymogen that forms active trypsin when cleaved.

Active transport

Transport that requires energy to move molecules against the concentration gradient. Moving ions or molecules from a low concentration to a higher one results in a decrease in entropy, therefore it requires the input of free energy. Protein pumps are embedded in the membrane are capable of using an energy source to move the molecule up a concentration gradient.

glycosaminoglycan

the protein component of proteoglycans is conjugated to this type of polysaccharide.

Classify the phrases based on whether they apply to oxidation or reduction. a. Oxidation b. Reduction

a. Oxidation: loss of electrons, loss of hydrogen, increase in the number of carbon-oxygen bonds, gain of oxygen b. Reduction: loss of oxygen, gain of electrons, gain of hydrogen, decrease in the number of carbon-oxygen bonds

The second messenger cyclic AMP (cAMP) is synthesized from ATP by the activity of the enzyme adenylyl cyclase. Cyclic AMP in turn activates protein kinase A (PKA), also called cAMP-dependent protein kinase, which is responsible for most of the effects of cAMP within the cell. Determine the correct steps in the activation of PKA, then place them in the correct order, starting after the adenylyl cyclase reaction

1. Cytosolic cAMP concentration increases 2. Two cAMP molecules bind to each PKA regulatory subunit 3. The regulatory subunits move out of the active sites of the catalytic subunits, and the R2C2 complex dissociates 4. The free catalytic subunits interact with proteins to phosphorylate Ser or Thr residues

phospholipids

abundant in all biological membranes. constructed from one or more fatty acids, a platform to which the fatty acids are attached, a phosphate, and an alcohol attached to the phosphate

Glucagon is a hormone that is released when the level of glucose in the blood is low. Glucagon uses a G protein signaling pathway to promote glycogenolysis. Put the steps of the signal transduction pathway in order from the releasing of glucagon into the blood to the promotion of glycogenolysis.

1. Glucagon is released into blood 2. G protein releases GDP and binds GTP 3. Activated G protein activates adenylate (adenylyl) cyclase 4. Adenylate cyclase converts ATP to cAMP 5. Cyclic AMP activates protein kinase A 6. Phosphorylase kinase phosphorylates glycogen phosphorylase 7. Glycogenolysis is promoted

Studies of oxygen transport in pregnant mammals show that the O2O2‑saturation curves of fetal (HbF) and maternal (HbA) hemoglobin are markedly different when measured under the same conditions. 1. Which hemoglobin has a higher affinity for O2 at the tissue pO2 of around 4 kPa a. cannot be determined from this data b. HbA c. HbF The allosteric inhibitory effector BPG binds to both the A form and the F form. Both forms show a lower affinity for O2O2 in the presence of BPG. However, the inhibitory effect of BPG is larger for HbA. The different O2O2 affinity indicated by the curves has been attributed to different BPG affinity for the two Hb forms. 2. BPG binds tighter to ____, which ____ its affinity for O2 3. Which statement that best explains the role of BPG in O2 transport from mother to fetus a. HbF will extract O2 from oxygenated HbA because BPG enhances O2 binding to HbF. b. In the placental circulation, HbF will load up on O2 as BPG dissociates from HbA and binds to HbF. c. HbA‑bound O2 will tend to move to HbF because HbF has a lower affinity for BPG, an allosteric inhibitor of O2 binding. d. HbA‑bound O2 will tend to move to HbF because HbA binds an additional BPG per tetramer when it enters placental circulation.

1. HbF 2. HbA, lowers 3. HbA-bound O2 will tend to move to HbF because HbF has a lower affinity for BPG, an allosteric inhibitor of O2 binding

Place all eight of these steps of the insulin signaling pathway in the correct order. The abbreviation PIP2PIP2 is used for phosphatidylinositol 4,5‑bisphosphate, and PIP3PIP3 is used for phosphatidylinositol 3,4,5‑trisphosphate.

1. Insulin is secreted 2. binding of insulin to the alpha subunit of the insulin receptor 3. activation of insulin receptor tyrosine kinase 4. phosphorylation of IRS proteins 5. phosphorylation of phosphoinositide 3-kinase (PI-3K) 6. Conversion of PIP2 to PIP3 7. activation of PIP3-dependent protein kinase B (PDK1) 8. activation of Akt 9. GLUT4 receptors transported to cell membrane 10. glucose enters cell

The table lists the standard free energies of hydrolysis (Δ⁢G∘⁢′) of some phosphorylated compounds. What is the direction of each of the following reactions when the reactants are initially present in equimolar amounts?

1. The reaction ATP + H2O ⇌ ADP + Pi proceeds to the right 2. The reaction ATP+glycerol⇌glycerol3−phosphate+ADP proceeds to the right 3. The reaction ATP+pyruvate⇌phosphoenolpyruvate+ADP proceeds to the left. 4. The reaction ATP + glucose⇌glucose6−phosphate+ADP proceeds to the right

Place the steps regarding fat digestion and absorption in the correct order. The abbreviation TAG is used for triacylglycerol (triglyceride).

1. Triacylglycerols enter stomach 2. Undigested fats enter the small intestine 3. The gallbladder secretes bile into the small intestine 4. Pancreatic lipase hydrolyzes TAGs in lipid droplets 5. Insoluble lipids, in micelles, are absorbed through the lining of the small intestine 6. TAGs in chylomicrons enter the lymph system 7. TAGs in chylomicrons enter the blood stream 8. Triacylglycerols absorbed into cells

The graph shows the hormone‑binding specificity of a hypothetical membrane receptor. The results are for three different hormones, X, Y, and Z. The graph plots the percentage binding capacity of the receptor as a function of hormone concentration for each hormone. Using the graph of percentage binding versus hormone concentration, give the estimated molar (M) concentration for each hormone that yields 50% of maximal binding. 1. [X] = 2. [Y] =

1. [X] = 1.0 x 10^-7 2. [Y] = 0.5 x 10^-5

Explain the digestion process of a complex carbohydrate by arranging the statements in the order that they occur.

1. a person takes a bite and begins to chew the complex carbohydrate into smaller pieces 2. the enzyme amylase, which is present in saliva, breaks polysaccharide chains into disaccharides 3. amylase is deactivated by the low pH in the stomach 4. other enzymes in the small intestine further break the polysaccharide into monosaccharides 5. monosaccharides are absorbed through the intestinal wall

There is a larger number of a hydrophilic molecules on the outside of a cell than on the inside. 1. Identify the conditions that could equalize the intracellular and extracellular concentrations of this molecule. a. placing intracellularly‑directed and extracellularly‑directed pumps in the membrane b. placing only intracellularly‑directed pumps in the membrane c. placing channel proteins in the membrane d. not inserting any transport proteins in the membrane 2. Which condition would be the most metabolically‑efficient way for a cell to equalize the intracellular and extracellular concentrations of this molecule? a. placing channel proteins in the membrane b. not inserting any transport proteins in the membrane c. placing intracellularly directed and extracellularly directed pumps in the membrane d. placing only intracellularly‑directed pumps in the membrane

1. a placing intracellularly‑directed and extracellularly‑directed pumps in the membrane c. placing channel proteins in the membrane 2. Which condition would be the most metabolically‑efficient way for a cell to equalize the intracellular and extracellular concentrations of this molecule? a. placing channel proteins in the membrane

The change in hemoglobin's oxygen affinity due to a change in pH is known as the Bohr effect. Physiological pH levels in tissues typically vary little, but these changes have a noticeable effect on the oxygen affinity of hemoglobin. The graph contains three oxygen dissociation curves for hemoglobin, each curve representing a different pH level. 1. Identify the pH for each oxygen dissociation curve in the graph. a. curve 1 b. Curve 2 c. Curve 3 2. What effect will hemoglobin have on the bicarbonate reaction in blood in the lungs? a. It will decrease HCO3- production b. It will decrease CO2 production c. It will decrease the amount of O2 unloaded d. It will increase the pH level

1. a. Curve 1 pH = 7.6 b. Curve 2 pH = 7.4 c. Curve 3 pH = 7.2 2. a. it will decrease the HCO3- production

Ras

Activated when Sos binds to it. A prominent signal transduction component that when activated, binds to other components of the molecular circuitry, leading to the activation of the specific protein kinases that phosphorylate specific targets that promote cell growth. Regulates cell growth through serine or threonine protein kinases.

A researcher is investigating a recombinant mutant hemoglobin (HbX) and compares its activity to that of normal myoglobin (Mb) and hemoglobin (Hb). 1. what can you deduce from the dissociation curve a. the P50 values of HbX and Hb are almost identical b. The oxygen affinity of Mb is lower than both Hb and HbX c. The oxygen affinity of HbX is higher than Hb at pO2>30 torr d. Oxygen binding by Hb follows Michaelis-Menten kinetics 2. Mb Hill coefficient = 3. HbX Hill coefficient = 4. Hb Hill coefficient 5. Given the results of the Hill plot and the dissociation curves, which of the following are true? a. HbX will load less O2 in the lungs and unload less O2 in active tissues than normal Hb b. The Hill coefficient for Hb is equal to the number of hemoglobin O2 binding sites c. Oxygen binding by Hb is less cooperative than for Mb d. Oxygen binding by HbX is less cooperative than for Hb

1. a. The P50 values of HbX and Hb are almost identical 2. Mb Hill coefficient = 1.0 3. HbX hill coefficient = 1.8 4. Hb Hill coefficient = 2.9 5. a. HbX will load less O2 in the lungs and unload less O2 in active tissues than normal Hb d. Oxygen binding by HbX is less cooperative than for Hb

1. Select the molecules that have a higher phosphoryl‑transfer potential than ATP. a. creatine phosphate b. 1,3‑bisphosphoglycerate c. pyrophosphate d. glucose 1‑phosphate 2. Under normal physiological conditions, 1,3‑bisphosphoglycerate _____

1. a. creatine phosphate b. 1,3‑bisphosphoglycerate 2. transfers a phosphate group to ADP

1. Consider the lipid shown. Identify the fatty acids incorporated in the lipid a. lauric acid b. stearic acid c. palmitic acid d. myristic acid 2. To which class of lipid does this belong? 3. Which properties are true of this lipid? a. The phosphate ester is hydrophobic. b. The lipid can form part of a cell membrane. c. The lipid has two nonpolar tails. d. The lipid has a polar head group. e. The hydrophobic chains are attracted to water due to hydrogen bonding.

1. a. lauric acid b. stearic 2. phospholipid 3. b. The lipid can form part of a cell membrane. c. The lipid has two nonpolar tails. d. The lipid has a polar head group.

The mutated form of hemoglobin (hemoglobin S, or HbS) in sickle‑cell anemia results from the replacement of a glutamate residue by a valine residue at position 66 in the β chain of the protein. Normal hemoglobin is designated HbA. Under conditions of low [O2][O2] , HbS aggregates and distorts the red blood cell into a sickle shape. See image of eight aggregated HbS molecules. Sickled red blood cells are relatively inflexible and may clog capillary beds, causing pain and tissue damage. The sickled red blood cells also have a shorter life span, leading to anemia. 1. Which amino acids would be expected to produce a similar sickling effect if substituted for Val at position a. leucine b. phenylalanine c. alanine d. arginine e. lysine Sickling occurs in deoxyhemoglobin S but not in oxyhemoglobin S. Oxyhemoglobin has a small, hydrophobic pocket in a β chain region located in the interior of the protein. In deoxyhemoglobin, however, this pocket is located on the surface of the protein. In deoxyhemoglobin S, Val 66 interacts with this surface pocket, leading to aggregation of HbS. 2. Choose two amino acids that would be reasonable candidates for the pocket-Val 66 interaction. a. phenylalanine b. glutamine c. serine d. leucine e. glutamate 3. How does HbS aggregation occur in sickle‑cell anemia? Place the steps in the correct order. Note that deoxyhemoglobin is in the T state; oxyhemoglobin is in the R state.

1. a. leucine c. alanine 2. a. phenylalanine d. leucine 3. a. No aggregation b. R state Hb shifts to T state Hb c. Val interacts with the pocket of a B chain on another HbS d. Additional T state HbS interact with the growing aggregate to form an insoluble fiber e. Sickled red blood cell

In biological systems, there are several membrane transport systems responsible for the passage of ions like Na+Na+ and K+K+, or small molecules like glucose and amino acids, through biological membranes. Classify each membrane transport system as either a primary active transporter, a secondary active transporter, or a passive transporter. 1. a. primary active transporter b. secondary active transporter c. passive transporter 2. Which transport systems utilize a chemical reaction for the energy source? a. The amino acid−Na+ transporter of kidney cells b. the glucose−Na+ transporter of intestinal epithelial cells c. the Na+/K+ ATPase of plasma membranes d. the glucose transporter of erythrocytes e. the Ca2+ ATPase of the sarcoplasmic reticulum

1. a. primary active transporter the Na+/K+ATPase of plasma membranes, the Ca2+ATPase of the sacroplasmic reticulum b. secondary active transporter: the amino acid Na+ transporter of kidney cells, the glucose Na+ transporter of intestinal epithelial cells c. passive transporter: the glucose transporter of etythrocytes 2. c. the Na+/K+ATPase of plasma membranes e. the Ca2+ ATPase of the sacroplasmic reticulum

A researcher has observed that the oxygen affinity of adult hemoglobin (HbA) is higher than expected when using a purified sample rather than red blood cell lysate. She plots the oxygen affinity curves for the purified HbA, cell lysate HbA, and purified HbA in the presence of 2.5 mM2.5 mM 2,3‑bisphosphoglycerate2,3‑bisphosphoglycerate (2,3‑BPG). 2,3‑BPG is known to be an allosteric regulator of HbA in red blood cells. The researcher also compares the HbA data with data from a sample of purified recombinant fetal hemoglobin (HbF) and purified HbF in the presence of 2.5 mM2.5 mM 2,3‑BPG. All purified hemoglobin samples have the same protein concentration. The five dissociation curves are shown in the graph. 1. Given the oxygen dissociation curves, which of the following statements are correct? a. 2,3‑BPG is an allosteric activator of HbA. b. 2,3‑BPG only weakly interacts with HbF. c. The allosteric effects of 2,3‑BPG are homotropic. d. HbF loads oxygen at lower 𝑝O2 than does HbA in the presence of 2,3‑BPG. e. Purified HbA has a higher oxygen affinity than purified HbF. 2. Which residue in HbA β do you think contributes the most to the increased interaction between HbA aand 2,3‑BPG?

1. b. 2,3-BPG is an allosteric activator of HbA d. HbF loads oxygen at lower pO2 than does HbA in the presence of 2,3-BPG e. Purified HbA has a higher oxygen affinity than purified HbF 2. His-143

Phospholipase C

Activated when the binding of a hormone (vasopressin, for example which regulates water retention) to its 7TM receptor. The activated enzyme then hydrolyzes the phosphodiester linkage joining the phosphorylated inositol unit to the acylated glycerol moiety. Cleaves PIP2, which produces IP3 and DAG. IP3 is soluble and can diffuse from the membrane. DAG stays in the membrane.

2,3-biphosphoglycerate (2,3-BPG)

An allosteric regulator molecule within cells, accounts for the difference between purified hemoglobin and hemoglobin in red blood cells.

phosphorylation potential

An alternative index of the energy status. It is directly related to the free-energy storage available in the form of ATP.

Acid‑sensitive ion channels (ASICs) are a family of ligand‑gated channels that permit Na+Na+ influx in response to H+.H+. The tarantula toxin, psalmotoxin 1 (PcTX1), inhibits some ASICs. A researcher exposes four different ASIC family members in vivo to PcTX1 at a concentration of 10 nM and takes electrophysiological recordings. Changing the pH from 7.4 to the pH indicated on each recording opens the channel. The black bar above each recording shows when PcTX1 was present, after which time the researcher rapidly washed the toxin from the system. 1. Based on the electrophysiological recordings, which ASIC family member is sensitive to PcTX1? a. ASIC2a b. ASIC3 c. ASIC1b d. ASIC1a 2. Using the dose-response curve, estimate the nanomolar concentration of PcTX1 that yields 50% inhibition of the sensitive channel. 3. Based on the electrophysiological recordings, which choice describes the inhibitory effect of PcTX1 on the sensitive channel? a. The effect is pH dependent. b. The effect is PcTX1 concentration dependent. c. The effect is reversible. d. The effect is irreversible.

1. d. ASIC1a 2. IC50 = 0.8 3. c. The effect is reversible

List the means by which the B-adrenergic pathway is terminated

1. dissociation of epinephrine from the receptor 2. conversion of cAMP into AMP by phosphodiesterase and the subsequent inhibition of PKA 3. Conversion of GTP into GDP by Ga and the subsequent reformation of the inactive heterotrimeric G protein

Consider a uniport system where a carrier protein transports an uncharged substance A across a cell membrane. Suppose that at a certain ratio of [A]inside to [A]outside, the Δ𝐺 for the transport of substance A from outside the cell to the inside, Aoutside→Ainside, is −11.7kJ/mol at 25°C. 1. What is the ratio of the concentration of substance A inside the cell to the concentration outside? 2. Choose the true statement about the transport of A under the conditions described. a. Movement of Aoutside to Ainside will be spontaneous. b. Increasing [A]outside will cause Δ𝐺 for movement of Aoutside to Ainside to become a smaller negative number. c. Decreasing the concentration of the uniport protein in the membrane will cause Δ⁢G to become a larger negative number. d. Because Δ𝐺 is negative, the ratio [A]inside/[A]outside must be greater than one.

1. ratio = 0.00890 2. movement of Aoutside to Ainside will be spontaneous

The table contains the standard free energies of hydrolysis of phosphorylated compounds. Use the values in the table to answer questions about phosphorylation reactions in glycolysis. 1. Calculate the standard free energy change, Δ⁢G∘′, of the ATP+pyruvate↽−−⇀ADP+phosphoenolpyruvate reaction at 25 ∘C. 2. Calculate the standard equilibrium constant, Keq′, of the ATP+pyruvate↽−−⇀ADP+phosphoenolpyruvate reaction at 25 ∘C. 3. What is the equilibrium ratio of pyruvate to phosphoenolpyruvate if the ratio of ATP to ADP is 10? 4. Calculate Δ⁢G∘′ for the isomerization of glucose 6‑phosphate to glucose 1‑phosphate at 25 ∘C. 5. What is the equilibrium ratio of glucose 6‑phosphate to glucose 1‑phosphate at 25 degrees C

1. ∆G∘' = 31.4 2. K'eq = 3.15 x 10^-6 3. equilibrium ratio: 3.17 x 10^4 4. ∆G∘' = 7.1 5. equilibrium ratio = 17.5

The concentrations of ATP, ADP, and Pi differ with cell type. Consequently, the release of free energy from ATP hydrolysis varies with cell type. Use the table to calculate the free energy change, ∆G, of ATP hydrolysis in liver, muscle, and brain cells. The expression for free energy change is Δ𝐺=Δ𝐺∘′+𝑅𝑇 ln(𝑄) The standard free energy, ΔG°′, of ATP hydrolysis is −30.5 kJ⋅mol−1.−30.5 kJ⋅mol−1. The product of the gas constant and temperature, R⁢T, is 2.47 kJ⋅mol−1. In which cell type does ATP hydrolysis release the most energy? a. brain b. liver c. muscle

1. ∆𝐺 of ATP hydrolysis in liver cells: -45.3 kJ•mol-1 2. Δ⁢G of ATP hydrolysis in muscle cells: -47.9 kJ • mol-1 3. Δ⁢G of ATP hydrolysis in brain cells: -48.4 kJ•mol -1 4. brain

Which statement correctly describes how 2,3-bisphosphoglycerate (2,3-BPG) reduces hemoglobin's affinity for oxygen? a. 2,3‑BPG binds to the amino termini, stabilizing the R (high‑affinity) state. b. 2,3‑BPG binds to positively charged Lys and His residues in the center of the hemoglobin, stabilizing the T (low‑affinity) state. c. 2,3‑BPG binds to the heme iron and prevents oxygen from binding. d. 2,3‑BPG binds to the interface between α1β1 and α2β2, stabilizing the R (high‑affinity) state.

2,3-BPG binds to positively charged Lys and His residues in the center of the hemoglobin, stabilizing the T (low-affinity) state

G-protein-coupled receptors (GPCRs)

7TM receptors. Hundreds of Ga molecules are converted to their GTP-bound forms from their GDP-bound forms for each bound molecule of hormone, giving an amplified response.

Protein kinase A

A key enzyme that mediates the effects of cAMP in eukaryotic cells. It phosphorylates the substrate at the expense of ATP. consists of 2 regulatory (R) subunits and 2 catalytic (C) subunits. cAMP binds to the regulatory subunits which releases the catalytic subunits, and therefore activated PKA can phosphorylate specific serine and threonine residues on target molecules. The C and R subunits subsequently rejoin to form the inactive enzyme.

Thalassemia

A prevalent inherited disorder of hemoglobin, caused by the loss or substantial reduction of a single hemoglobin chain. Results in low levels of functional hemoglobin and a decreased production of red blood cells. May lead to anemia, fatigue, pale skin, and spleen and liver malfunction. The alpha chain of hemoglobin is not produced in sufficient quantity.

Activated carriers

A recurring motif in biochemistry. Many function as coenzymes. They can be carriers of electrons for fuel oxidation, or carriers of electrons for synthesis of biomolecules.

distal histidine

A second histidine that resides on the opposite side of the heme from the proximal histidine. The distal histidine prevents the oxidation of the heme iron to the ferric ion (Fe3+), which cannot bind oxygen, and also reduced the ability of carbon monoxide to bind the heme.

primary messenger

A stimulus such as a wound or a digested meal triggers the release of the signal molecule.

Selectivity filter

A stretch of 5 amino acids within the restricted part of the pore built from residues contributed by the 2 transmembrane alpha helices. It determines the preference for K+ over other ions.

Gα (G alpha)

A subunit of the G protein. It binds to the nucleotide of the G protein. When GTP binds to activate the G protein, the alpha subunit dissociates from the beta-gamma dimer

Multidrug resistance can make it difficult to treat cancer successfully with chemotherapy. What causes multidrug resistance in cancer cells? a. The immune system identifies each chemotherapy drug as foreign and develops antibodies to each drug. b. Some cancer cells phagocytize chemotherapy drugs and use the lysosomes in the cell to destroy the drugs. c. Chemotherapy drugs and other toxins are actively pumped out of cancer cells by transmembrane proteins. d. The smooth endoplasmic reticulum in some cancer cells neutralizes a variety of chemotherapy drugs.

C. Chemotherapy drugs and other toxins are actively pumped out of cancer cells by transmembrane proteins.

What properties of ATP make it an especially effective phosphoryl-transfer-potential compound?

Charge repulsion is reduced when a phosphoryl group is removed from ATP. The products of ATP hydrolysis have more resonance forms than does ATP. Entropy is increased when one molecule of ATP is converted into two product molecules, ADP and Pi. The products if ATP hydrolysis are more effectively stabilized by association with water than is ATP.

The hormonal control of digestion.

Cholecystokinin (CCK) is secreted by specialized intestinal cells and causes the secretion of bile salts from the gallbladder and digestive enzymes from the pancreas. Secretin stimulates sodium bicarbonate secretion from the pancreas, which neutralizes the stomach acid.

A triacylglycerol consists of fatty acids attached to one glycerol. two glycerol phosphates. one glycerol phosphate. three cholesterols.

Compounds that contain a fused ring system are called steroids. These have three 6‑membered rings and one 5‑membered ring. Some of these compounds are found in biological membranes. The building blocks for many lipids are fatty acids. They generally contain an even number of carbon atoms and an unbranched hydrocarbon chain. Glycolipids are formed when a carbohydrate is glycosidically linked to a hydroxyl group of a lipid. Examples include gangliosides and cerebrosides. These are also found in biological membranes. Accumulating in adipose tissue, triacylglycerols are the storage form of lipids. They can be used as metabolic fuel. These compounds have a polar part made of three ester groups and a nonpolar fatty acid tail. sphingolipids are made up of a long‑chain amino alcohol joined to a fatty acid, either by a glycosidic linkage or a phosphodiester linkage. These do not contain glycerol. They are abundant in the nervous system. When glycerol is esterified to two fatty acids and a phosphoric acid molecule, a phosphoglyceride is formed. These are found in biological membranes.

The illustration shows several oxygen‑dissociation curves. Assume that curve 3 corresponds to hemoglobin with physiological concentrations of CO2CO2 and 2,3-bisphosphoglycerate (2,3-BPG) at pH 7.

Curve 1 - a loss of quaternary structure Curve 2 - a decrease in CO2, an increase in pH Curve 3 - no perturbation Curve 4 - an increase in 2,3-BPG

Intermediary metabolism

Defined pathways in the cell that are interdependent. Activities are coordinated by exquisitely sensitive means of communication in which allosteric enzymes are predominant.

Triacylglycerols

Fatty acids required for energy generation. Formed by the attachment of three fatty acid chains to a glycerol molecule. The fatty acids are attached to the glycerol through ester linkages in a process known as esterification.

What is the molecular consequence of the hemoglobin S mutation?

Hemoglobin S forms aggregates and fibrous precipitates when oxygen is released

Arrange the substances in order of decreasing permeability through a lipid bilayer membrane.

High permeability --> low permeability: indole, glycerol, glucose, Cl-

Write equations for the hydrolysis of ATP and ADP. Use abbreviations such as ATP for adenosine triphosphate and Pi to represent inorganic phosphate.

Hydrolysis of ATP: ATP + H2O --> ADP + Pi Hydrolysis of ADP: ADP + H2O --> AMP + Pi

For the given changes in environment, choose whether the oxygen binding affinity of hemoglobin will increase, decrease, or not change. Increase in body temperature a. No change b. decrease c. increase Decrease in blood pH a. increase b. no change c. decrease Decrease in partial pressure of CO2 a. decrease b. increase c. no change

Increase in body temperature b. decrease Decrease in blood pH c. decrease Decrease in partial pressure of CO2 b. increase

Why does it make good physiological sense for insulin to increase the number of glucose transporters in the cell membrane?

Insulin signifies the fed state. Its presence leads to the removal of glucose from the blood for storage or metabolism. Increasing the number of glucose transporters available makes these biochemical processes more efficient

What determines the direction of ion flow through a channel?

Ion channels allow ion flow in either direction. By the 2nd law of thermodynamics, ions will flow down their concentration gradient.

The binding of oxygen to myoglobin and hemoglobin has what effect on the heme iron?

It causes the iron to move closer to the plane of the porphyrin ring

The structures of lactose and trehalose are shown. Compare and contrast these carbohydrates (lactose and trehalose). Label the Venn diagram. If a term describes only lactose, place it in the light blue shaded area on the left labeled lactose. If a term describes only trehalose, place it in the purple shaded area on the right labeled trehalose. If a term describes both molecules, place it in the middle, where the labeled circles overlap.

Lactose: beta --> 4, galactose Both: disaccharide, O-glycosidic bond Trehalose: a1<->a1, nonreducing

chylomicrons

Lipoprotein transport particles formed when triacylglycerols associate with specific proteins and a small amount of phospholipid and cholesterol. They are transport particles that are composed of 98% triacylglycerols with proteins and phospholipid on the surface. They are released into the lymph system and then into the blood.

secondary transporters (cotransporters)

Membrane proteins that move ions or molecules uphill by coupling the uphill flow of one species of ion/molecule to the downhill flow of a different species (transport NOT driven by ATP hydrolysis)

Gangliosides

More complex glycolipids that contain a branched chain of as many as seven sugar residues. They are orientated in an asymmetric fashion in membranes with the sugar residues always on the extracellular side of the membrane.

Chemotrophs

Obtain energy through the oxidation of carbon fuels (including humans)

multidrug-resistance protein (P-glycoprotein)

S protein that acts as an ATP-dependent pump that extrudes a wide range of small molecules from cells that express it. It provides multidrug resistance. When cells are exposed to a drug, the MDR protein pumps the drug out of the cell before the drug can exert its effects. The protein comprises four domains: 2 membrane spanning domains, and 2 ATP-binding domains

Match the features to either the sequential or concerted model of allosteric regulation.

Sequential model a. ligand affinity of protein varies with number of bound ligands b. hybrid conformations between subunits allowed c. ligand affinity of empty subunits affected by ligand-bound subunits d. negative homotropic effects allowed Concerted model a. conformational states always reach equilibrium between proteins b. symmetry rule dictates subunits all in the same conformation c. ligand affinity dependent only on quaternary structure

The graph represents the adult hemoglobin binding curve (in green) at pH 7.4 in the presence of 2,3‑bisphosphoglycerate. The hemoglobin binding curve has a sigmoidal shape, due to four interacting oxygen‑bound sites. For comparison, the myglobin binding curve has only one oxygen‑bound site and has a hyperbolic curve. For each of the six scenarios, determine whether the hemoglobin binding curve would shift left or shift right.

Shifts left a. The adult hemoglobin (HbA) is replaced by an infant's fetal hemoglobin b. Hemoglobin is isolated from red blood cells and stripped of 2,3-biphosphoglycerate c. Tetrameric hemoglobin is dissociated into its subunits Shifts right a. The blood pH drops from 7.2 to 7.2 b. The CO2 concentration in the blood increases c. The concentration of 2,3-biphosphoglycerate increases during acclimation to high altitude

Determine whether each phrase describes starch, glycogen, or cellulose.

Starch: plant polysaccharide that is easily digested by humans, made up of two glucose polysaccharides: amylose and amylopectin Glycogen: major storage form of carbohydrates in animals Cellulose: structural support for plants

ATP-binding cassettes (ABCs)

The ATP-binding domains of MDRs. Include ABC transporters.

P-type ATPase

The Na+-K+ ATPase that forms a key phosphorylated intermediate. In formation of this intermediate, a phosphoryl group obtained from ATP is linked to the side chain of a specific conserved aspartate residue in the pump to form phosphorylaspartate. Helps the Na+-K+ ATPase function by forming this key phosphorylated intermediate.

Cooperative effect

The binding of oxygen to hemoglobin isolated from red blood cells displays marked sigmoidal behavior, whereas myoglobin shows a hyperbolic curve. Allosteric proteins exhibit the cooperative effect.

What factors determine the melting point of fatty acids?

The chain length and the degree of cis unsaturation

Facilitated diffusion (passive transport)

The crossing of a molecule across the membrane facilitated by a channel. The energy driving the ion movement originates in the ion gradient itself, without any contribution by the transport system. Channels have substrate specificity to only let some ions into the cell, and not others.

Proximal histidine

The imidazole ring of the histidine residue in hemoglobin and myoglobin that occupies the fifth and sixth coordination sites

Predict the effect on membrane lipid composition if the temperature of a bacterial culture is raised from 37 degrees C to 42 degrees C

The increase in temperature will increase the fluidity of the membrane. To prevent the membrane from becoming too fluid, the bacteria will incorporate longer-chain fatty acids into the membrane phospholipids. This alteration will increase Van Der Waals interactions among the chains and decrease fluidity.

Energy charge

The index of the energy status. A fraction of all of the adenine nucleotide molecules in the form of ATP plus half the fraction of adenine nucleotides in the form of ADP, given that ATP contains two phosphoanhydride linkages, whereas ADP contains one. Ranging form 0 to 1, is buffered.

Protoporphyrin

The organic component of a heme group that contains a central iron atom. Made up of four pyrrole rings linked by methine bridges to form a tetrapyrrole ring. Four methyl groups, two vinyl groups, and two propionate side chains are attached.

Gβγ (G beta-gamma)

The other subunit of the G protein coupled receptor. Dissociation of the subunits transmits the signal that GTP has been bound.

sphingosine

The platform on which phospholipids are built may be glycerol, a three-carbon alcohol, a more complex alcohol.

Heme

The prosthetic group of myoglobin and hemoglobin as well as other proteins; consists of an organic constituent, protoporphyrin, and an iron atom. Has the ability to bind an oxygen.

Bohr effect

The regulation of oxygen binding by hyrdogen ions and carbon dioxide. Hemoglobin's oxygen binding affinity is inversely related both to acidity and to the concentration of carbon dioxide. Lowering the pH results in the release of O2 from oxyhemoglobin.

ligand

The signal molecule that binds to a binding site on the extracellular domain and triggers a particular pathway.

G protein

The singnal-coupling protein. Stimulates the activity of adenylate cyclase, an enzyme that increases the concentration of second messenger cAMP by forming it from ATP. In the unactivated state, the guanyl nucleotide bound to the G protein is GDP (G protein exists as a heterotrimer consisting of alpha, beta, and gamma subunits). The alpha and gamma subunits are anchored to the membrane by covalently attached fatty acids. The exchange of the bound GDP for GTP is catalyzed by the ligand-bound receptor. GTP binds and the protein becomes active.

Na+-K+ pump (Na+-K+ ATPase)

The specific transport system that maintains a high intracellular concentration of K+ and a low intracellular concentration of Na+. The hydrolysis of ATP by the pump provides energy needed for the active transport of 3Na+ ions out of the cell and 2K+ ions into the cell, thus generating an ion gradient that can power simple diffusion. The Na+-K+ ATPase is an ATP-driven pump

phosphoryl-transfer potential

The standard free energy of hydrolysis A means of comparing the tendency of organic molecules to transfer a phosphoryl group to an acceptor molecule. ATP has a higher phosphoryl-transfer potential than glycerol 3-phosphate.

Na+/K+ATPase (sodium potassum adenosine triphosphatase) is found in the plasma membrane and catalyzes the exchange of sodium and potassium ions across the membrane. Classify the statements about the transport system as either true or false.

True: pumps Na+ ions out of the cell, pumps K+ ions into the cell, exchanges 3Na+ ions for 2K+ ions, creates a membrane potential that is negative on the inside False: Pumps Na+ ions into the cell, pumps K+ ions out of the cell, exchanges 3K+ ions for 2Na+ ions, the transport protein becomes adenylated by ATP during the transport cycle

Explain why a person who has trypsinogen deficiency will suffer from more digestion difficulties than will a person lacking most other zymogens.

Trypsin, which is formed from trypsinogen, activates most of the other zymogens. Hence, a deficiency in trypsinogen would lead to a loss of activity of virtually all of the enzymes required for digestion. On the other hand, loss of a zymogen for lipase, for instance, would impair only lipid digestion, without affecting the digestion for other molecules.

Label blood types O and A with the correct monosaccharides. The defining monosaccharide is noted by the gray and orange bond. Each monosaccharide may be used more than once. 1. Type O 2. Type A

Type O: N-acetyl-D-glucosamine, D-galactose, L-fucose Type A: N-acetyl-D-glucosamine, D-galactose --> N-acetyl-D-galactosamine, L-fucose

Simple diffusion

When molecules can pass through the membrane in their path of movement without using any energy. Molecules spontaneously move from a high to low concentration, and in this case the molecule can pass directly through the membrane because they dissolve in the lipid bilayer. Molecules that can do this are typically small and nonpolar.

The standard free energy (Δ𝐺∘′)(Δ⁢G∘⁢′) of the creatine kinase reaction is −12.6 kJ⋅mol−1. The Δ𝐺 value of an in vitro creatine kinase reaction is −0.1 kJ⋅mol−1. At the start of the reaction, the concentration of ATP is 6 mM, the concentration of creatine is 12 mM, and the concentration of creatine phosphate is 25 mM. Using the values given, calculate the starting concentration of ADP in micromolar. [ADP] =

[ADP] = 18.5 µM

Calmodulin (CaM)

a 17 kDa protein with four calcium binding sites that serves as a calcium sensor in nearly all eukaryotic cells. It is activated by binding of Ca2+ when the cytoplasmic calcium level is raised. A member of the EF-hand protein family. The Ca2+ - calmodulin complex stimulates a wide array of enzymes, pumps, and other target proteins.

EF hand

a Ca2+ binding motif that consists of a helix, a loop, and a second helix. It was initially discovered in the parvalbumin protein and was named because the helices designated E and F that form the calcium-binding motif are positioned like the forefinger and thumb of the right hand.

glycosidic bond

a bond formed between the anomeric carbon atoms of glucose and the oxygen atom of an alcohol

lectin

a class of glycan-binding proteins that interact with carbohydrate partners to guide biological processes. The diverse carbohydrate structures displayed on cell surfaces are well suited to serving as sites of interaction between cells and their environments. They promote interactions between cells by facilitating cell-cell contact.

selectins

a class of lectins that consists of proteins which bind immune-system cells to sites of injury

sphingomyelin

a common sphingolipid found in membranes. the amino group of the sphingosine backbone is linked to a fatty acid by an amide bond. In addition, the primary hydroxyl group of sphingosine is attached to phosphorylcholine through an ester linkage. Found in the plasma membrane of many cells but is especially rich in the myelin sheath of nerve cells

sickle-cell anemia

a disease caused by a single amino acid substitution in one hemoglobin chain. Comes from the abnormal sickle shape of red blood cells deprived of oxygen. symptoms include weakness, shortness of breath, dizziness, headaches, palpitations, and shortness of breath. Caused by sickle-cell hemoglobin (HbS) when valine is substituted for glutamate at position 6 of the beta chains. This alteration reduces the solubility of the deoxygenated but not the oxygenated form of hemoglobin.

Cholecystokinin (CKK)

a hormone released by intestinal cells in response to the polypeptide products of pepsin digestion. The pancreas responds to CCK by releasing a host of digestive enzymes into the intestine, where the digestion of proteins continues and the digestion of lipids and carbohydrates begins.

secretin

a hormone released by the cells of the small intestine in response to the low pH of food coming from the stomach. It promotes the release of NaHCO3 from pancreatic cells, which neutralizes the pH of the food as it exits the stomach.

cholesterol

a key modulator of membrane fluidity. Contains a bulky steroid nucleus with a hydroxyl group at one end and a flexible hydrocarbon tail at the other end. The molecule inserts into bilayers with its long axis perpendicular to the plane of the membrane. Its shape disrupts the regular interactions between fatty acid chains and helps maintain membrane fluidity.

Metabolism

a linked series of chemical reactions that begins with a particular biomolecule and converts it into some other required biomolecules in a carefully defined fashion. Metabolic pathways process a biomolecule from a starting point to an end point without the generation of wasteful or harmful side products

emulsion

a mixture of lipid droplets and water created by the grinding and mixing that takes place in the stomach. Any mixture of lipids and water (salad dressing, mayonnaise, etc.)

ketose

a monosaccharide with a keto group

aldose

a monosaccharide with an aldehyde group

Action potential

a nerve impulse. An electrical signal produced by the flow of ions across the plasma membrane (Na+ and K+ typically). The fundamental means of communication in the nervous system.

enteropeptidase (enterokinase)

a zymogen that is anchored to the epithelial cells of the small intestine, activates the pancreatic zymogen trypsinogen to form trypsin.

The molecular weight of sperm whale myoglobin is 17.8 kDa.17.8 kDa. The myoglobin content of sperm whale muscle is about 80 g · kg−1.80⁢ g · kg−1. In contrast, the myoglobin content of some human muscles is about 8 g · kg−1.8⁢ g · kg−1. Compare the amounts of O2O2 bound to myoglobin in human muscle and in sperm whale muscle. Assume that the myoglobin is saturated with O2,O2, and that the molecular weights of human and sperm whale myoglobin are the same. How much O2O2 is bound to myoglobin in human muscle? a. O2 bound in human muscle: How much O2 is bound to myoglobin in whale muscle? b. O2 bound in whale muscle: The amount of oxygen dissolved in tissue water at 37°C37°C is about 3.5×10−5 M.3.5×10−5 M. What is the ratio of myoglobin‑bound oxygen to dissolved oxygen in the tissue water of sperm whale muscle? c. Ratio of bound oxygen to dissolved oxygen

a. 0.0144 b. 0.144 c. 128

What is the difference between docosahexaenoate (DHA) and 19,20-dihydroxydocosapentaenoate (19,20-DHDP)? a. 19,20-DHDP is more polar than DHA. b. DHA has a higher melting point than 19,20-DHDP. c. Only DHA is a an 𝜔ω-3 fatty acid. d. Only DHA is a polyunsaturated fatty acid.

a. 19,20-DHDP is more polar than DHA.

The average volume of a red blood cell is 87μm3.87⁢μ⁢m3. The mean concentration of hemoglobin in red blood cells is 0.34 g⋅ml−1.0.34 g⋅ml−1. What is the weight of the hemoglobin contained in an average red blood cell? a. hemoglobin weight: How many hemoglobin molecules are there in an average red blood cell? Assume that the molecular weight of the human hemoglobin tetramer is 65 kDa b. number of hemoglobin molecules:

a. 2.958 x 10^-11 b. 2.741 x 10^8

About how many grams per day of protein is sloughed off the cells of the intestine through the wear and tear of digestion? a. 50-100 b. 100-200 c. 5 d. >200

a. 50-100

Suppose Gina climbs a high mountain where the oxygen partial pressure in the air decreases to 80 torr.80 torr. Assume that the pH of her tissues and lungs is 7.47.4 and the oxygen concentration in her tissues is 20 torr.20 torr. The 𝑃50P50 of hemoglobin is 26 torr.26 torr. The degree of cooperativity of hemoglobin, 𝑛,n, is 2.8.2.8. Estimate the percentage of the oxygen‑carrying capacity that she utilizes. Calculate your answer to one decimal place. a. capacity: Why does increasing the concentration of 2,3‑BPG in Gina's blood cells help her function well at high altitudes? a. Her oxygen‑binding curve shifts to the right, promoting oxygen delivery to tissues. b. Her hemoglobin P50 decreases, causing more blood‑to‑tissue oxygen offloading. c. The extra 2,3‑BPG stabilizes the relaxed, or R, state of hemoglobin, increasing oxygen binding. d. Excess 2,3‑BPG binds oxygen when hemoglobin becomes saturated, acting as an oxygen transporter.

a. 63.5% b. Her oxyen-binding curve shifts to the right, promoting oxygen delivery to tissues

Arrange the fatty acids from highest melting point to lowest melting point. Select the statements about fatty acid melting points that are true. a. A saturated fatty acid with a greater molar mass has a higher melting point than a saturated fatty acid with a lower molar mass. b. A saturated fatty acid with a greater molar mass has a lower melting point than a saturated fatty acid with a lower molar mass. c. A saturated fatty acid has a higher melting point than an unsaturated fatty acid. d. A saturated fatty acid has a lower melting point than an unsaturated fatty acid.

a. A saturated fatty acid with a greater molar mass has a higher melting point than a saturated fatty acid with a lower molar mass. c. A saturated fatty acid has a higher melting point than an unsaturated fatty acid.

ABC transporters and P‑type ATPase transporters are membrane pumps that move ions and molecules across membranes. Classify each phrase as a descriptor of ABC transporters, P‑type ATPases, or both. Note that membrane pumps containing ATP‑binding cassette domains are referred to as ABC transporters. a. ABC transporters b. P-type ATPase transporters c. Both

a. ABC transporters: the multidrug resistance protein (P-glycoprotein) is an example, two ATP-binding domains, catalytic cycle begins with neither substrate nor ATP bound with the transporter able to convert between closed and open forms b. P-type ATPase transporters: an aspartate residue in the membrane pump is phosphorylated, the sacroplasmic reticulum Ca2+ ATPase (SERCA) is an example, catalytic cycle begins with substrate bound but ATP not bound (for example, the conformation E1-(Ca2+)2) c. Both: ATP-dependent, substrate and ATP may be bound at the same time

Which three of the statements are true? a. Amphipathic (amphiphilic) lipids are the structural basis of biological bilayer membranes. b. Hydrophobic molecules are individually hydrated in water, increasing the entropy of the system. c. Polar molecules are capable of forming micelles. d. The tendency of water to minimize its contact with nonpolar substances is called the hydrophobic effect. e. Hydrophobic molecules clump together in water because fewer water molecules are required to surround them, which results in a smaller decrease in entropy than if the molecules were individually hydrated.

a. Amphipathic (amphiphilic) lipids are the structural basis of biological bilayer membranes. d. The tendency of water to minimize its contact with nonpolar substances is called the hydrophobic effect. e. Hydrophobic molecules clump together in water because fewer water molecules are required to surround them, which results in a smaller decrease in entropy than if the molecules were individually hydrated.

Match each characteristic to the appropriate process a. anabolic process b. catabolic process

a. Anabolic process: requires energy inputs, such as ATP, uses NADPH as the electron carrier, synthesizes macromolecules b. Catabolic process: transforms fuels into cellular energy, such as ATP or ion gradients, uses NAD+ as the electron carrier, breaks down macromolecules

Which statement does NOT describe a difference between archaeal membrane lipids and those of bacteria and eukaryotes? a. Archeal membrane lipids use a backbone other than glycerol. b. Archaeal membrane lipids use ether linkages instead of ester linkages. c. Archaeal membrane lipids have long hydrophobic tails that are branched rather than linear. d. Archaeal membrane lipids have long‑chain alcohol esters rather than fatty acid esters attached to the glycerol.

a. Archeal membrane lipids use a backbone other than glycerol.

Classify the phrases. Does each phrase describe a kinase, a phosphatase, neither, or both? a. kinases b. phosphatases c. neither d. both

a. Kinases: catalyze phosphorylation reactions, may use ATP as a phosphoryl group donor, PKA (protein kinase A) is an example b. Phosphatases: remove phosphoryl groups from proteins, turn off signaling pathways triggered by kinases c. Neither: in eukaryotes, transfer phosphoryl groups to acidic amino acids, catalyze reactions that are the reverse of dephosphorylation reactions d. both: regulate the activity of other proteins

Select all the statements that correctly describe hemoglobin and myoglobin structure a. Both hemoglobin and myoglobin contain a prosthetic group called heme, which contains a central iron b. By itself, heme is not a good oxygen carrier. It must be part of a larger protein to prevent oxidation of the iron. c. Molecular oxygen binds irreversibly to the Fe(II)Fe(II) atom in heme. d. Hemoglobin and myoglobin are heterotetramers. e. Each hemoglobin molecule can bind four oxygen molecules; each myoglobin can bind one oxygen molecule. f. Each iron atom can form six coordination bonds. One of these bonds is formed between iron and oxygen. g. The heme prosthetic group is entirely buried within myoglobin.

a. Both hemoglobin and myoglobin contain a prosthetic group called heme, which contains a central iron b. By itself, heme is not a good oxygen carrier. It must be part of a larger protein to prevent oxidation of the iron. c. Each hemoglobin molecule can bind four oxygen molecules; each myoglobin can bind one oxygen molecule. d. Each iron atom can form six coordination bonds. One of these bonds is formed between iron and oxygen.

The steroid lipid cholesterol is a component of membranes. Identify true statements about cholesterol and its role in membrane fluidity. a. Cholesterol decreases membrane fluidity in areas called rafts, which contain large amounts of sphingolipids and cholesterol. b. Cholesterol is generally buried in the bilayer, with its planar rings oriented toward the solvent and its hydroxyl group aligned with the fatty acid tails of the bilayer. d. Cholesterol increases membrane fluidity in a membrane that otherwise contains mostly long‑chain saturated fatty acids. e. Cholesterol inhibits the crystallization that would otherwise occur in membranes rich in unsaturated fatty acids.

a. Cholesterol decreases membrane fluidity in areas called rafts, which contain large amounts of sphingolipids and cholesterol. c. Cholesterol increases membrane fluidity in a membrane that otherwise contains mostly long‑chain saturated fatty acids.

Coenzyme A, NAD+, and FAD are coenzymes that are necessary for energy production. Determine whether the phrases describe coenzyme A, NAD+, or FAD. a. Coenzyme A b. NAD+ c. FAD

a. Coenzyme A: forms part of acetyl-S-CoA (acetyl CoA) which is part of the citric acid cycle b. NAD+: derived from the vitamin nicotinamide, accepts two electrons and one proton when it is reduced c. FAD: accepts two hydrogen atoms when it is reduced, derived from the vitamin riboflavin (B2)

The trisaccharide raffinose is a minor constituent of sugar beets and is composed of ______. Treatment of raffinose with B-galactosidase produces _____. Raffinose is a _____ sugar.

a. D-galactose, D-glucose, and D-fructose b. D-galactose and sucrose c. nonreducing sugars

G protein‑coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) are two basic receptor types by which cells transduce signals. Classify each statement as describing GPCRs, RTKs, both types of receptors, or neither. a. GPCRs b. RTKs c. Both d. Neither

a. GCPRs: structure contains seven transmembrane helices, activate heterotrimeric G proteins directly, an example is the epinephrine receptor, phosphorylation of receptor can terminate signal or desensitize receptor b. RTKs: receptor activation causes phosphorylation of its cytosolic subunits, an example is the insulin receptor, autophosphorylation of receptor can initiate signal c. Both: ligand binding induces conformational change in receptor d. Neither: transports some ligands through the membrane

Match the descriptions to the type of G protein. a. heterotrimeric G proteins b. both c. small G proteins

a. Heterotrimeric G proteins: activated by 7TM receptors, active form dissociates to Gα and Gβγ b. Both: inactive form binds GDP, active form binds GTP c. small G proteins: activated by dimerized growth factor receptors, monomeric in both active and inactive forms

Cellulose could provide an abundant and cheap form of glucose for humans. Why is cellulose not a source of nutrients for humans? a. Humans, and most vertebrates, lack the enzyme cellulase. b. Humans cannot absorb the hydrolyzed form of cellulose. c. Vertebrate enzymes are unable to hydrolyze (β 1-4) linked glucose monomers. d. Animals use starch and glycogen as an energy source, whereas plants use cellulose for energy. e. Cellulose digestion must occur in a basic environment, but the human gut is acidic.

a. Humans, and most vertebrates, lack the enzyme cellulase. c. Vertebrate enzymes are unable to hydrolyze (β 1-4) linked glucose monomers.

People with achlorhydria suffer from an abnormal composition of gastric fluid. Why does a person who has achlorhydria have difficulty digesting proteins? a. Hydrochloric acid is absent in gastric juice, so pepsin cannot become active. b. the low volume of gastric fluid limits the physical breakdown of nutrients c. there are high amounts of hydrochloric acid in the gastric juice, so the stomach is too acidic d. the gastric juice does not contain amylase, so proteins are not digested properly

a. Hydrochloric acid is absent in gastric juice, so pepsin cannot become active.

Some G-protein coupled receptors are sensitive to hormones such as angiotensin II and oxytocin and act through compounds such as phospholipase C and IP3. Complete the flowchart showing the cleavage of a membrane lipid to form compounds that ultimately cause the phosphorylation of specific proteins. The abbreviations used are phosphatidylinositol 4,5-biphosphate, PIP2; protein kinase C, PKC; diacylglycerol, DAG; inositol 1,4,5-triphosphate, IP2; and phospholipase C, PLC. Which of the compounds can be considered second messengers? a. IP3 b. Ca2+ c. PIP2 d. Ser e. PKC f. DAG g. PLC

a. IP3 b. Ca2+ f. DAG

Choose all the true statements about protein digestion and hydrolysis. a. in the small intestine, chymotrypsin attacks peptide bonds. b. pepsin causes the hydrolysis of some of the peptide bonds in proteins c. Pancreatic juices are more acidic than gastric juices. d. Absorption of free amino acids occurs through the wall of the stomach. e. Enzymes present in saliva initiate the process of protein digestion.

a. In the small intestine, chymotrypsin attacks peptide bonds. b. Pepsin causes the hydrolysis of some of the peptide bonds in proteins.

Integral membrane proteins have different characteristics and functions than peripheral membrane proteins. Identify the statements that are properties of integral membrane proteins and those that are properties of peripheral membrane proteins. a. integral membrane proteins b. peripheral membrane proteins

a. Integral membrane proteins can extend through the cell membrane, can move laterally (sideways) in the hydrophobic part of the membrane, act as tunnels through the cell membrane b. Peripheral membrane proteins attach at the cell membrane surface

Select the molecules that contains sphingosine. a. Molecule A b. sphingomyelins c. phosphatidylserine d. Molecule C e. Molecule B

a. Molecule A b. sphingomyelins d. molecule C

Proto‑oncogenes are genes that have the potential to become oncogenes through either mutation or an increase in expression. Classify the statements as describing proto‑oncogenes or tumor suppressor genes. a. Proto-oncogenes b. Tumor suppressor genes

a. Proto-oncogenes: the genes code for proteins that normally promote cell division, mutations that increase activity of these genes may lead to cancer b. Tumor suppressor genes: these genes code for proteins that normally prevent uncontrolled cell division, mutations that decrease activity of these genes may lead to cancer, some products of these genes normally function in repairing damaged DNA

Sort the descriptions into properties that describe either saturated phospholipids or unsaturated phospholipids. a. saturated phospholipids b. unsaturated phospholipids

a. Saturated phospholipids: fatty acid tails are straight, have no double bonds in the fatty acid carbon chains, fatty acid tails pack tightly together, make the membrane somewhat rigid at low temperatures b. Unsaturated phospholipids: have bent fatty acid tails, contain one or more double bonds within the fatty acid tails, contain one or more double bonds within the fatty acid tails, maintain some space between adjacent phospholipids, allow the membrane to remain fluid and flexible at low temperatures

Tetrodotoxin is a poison found in pufferfish and some other animals. Most cases of human tetrodotoxin poisoning occur when a person eats cooked or uncooked pufferfish. The most strongly toxic parts are the liver and ovaries; muscle and testes are weakly toxic. The lethal dose (LD50)(LD50) for humans is less than 10𝜇 g/kg10⁢μ g/kg (1‑2 mg total for most people). There is no known antidote, and death can occur from respiratory failure if the diaphragm is unable to contract. Tetrodotoxin acts by blocking sodium channels. How does it lead to a loss of excitatory conduction in neurons? a. The membrane cannot depolarize. b. It blocks Na+ions from flowing out of the cell. c. Membrane repolarization is slowed. d. The membrane cannot repolarize. e. Membrane potential approaches +20mV.

a. The membrane cannot depolarize.

Which of the outcomes could potentially result if a mutation in the gene encoding the Gα subunit eliminates its GTPase activity? Choose three outcomes. a. The signaling pathway could be activated for an extended period, possibly resulting in undesirable cell proliferation. b. The concentration of cAMP in the cell would be continuously elevated. c. Gα would be activated for an extended period. d. The rate of GTP hydrolysis would increase. e. Gα would be ineffective as a signal molecule (that is, it could not activate other proteins). f. The cell would be unresponsive to molecules that act via cAMP.

a. The signaling pathway could be activated for an extended period, possibly resulting in undesirable cell proliferation. b. The concentration of cAMP in the cell would be continuously elevated. c. Gα would be activated for an extended period.

Adenosine triphosphate (ATP) is the main energy currency used in cells. ATP hydrolysis is coupled with unfavorable reactions, making the net change in energy for the set of reactions less than 0, which is favorable. Although ATP is the main energy currency, other molecules can fulfill this role and take part in coupled reactions. Determine whether each of the phrases or examples describes a thioester, reduced cofactor, or phosphorylated compound. a. Thioesters b. Reduced cofactors c. Phosphorylated compounds

a. Thioesters: the sulfur-carbon bond is hydrolyzed, acetyl-CoA b. Reduced cofactors: these compounds accept electrons during the oxidation of substrates. Energy is released when they are oxidized, NADH c. Phosphorylated compounds: these compounds yield HPO42- upon hydrolysis, phosphoenolpyruvate

Which of the statements are true? a. Triacylglycerols (triglycerides) are composed of fatty acid residues and glycerol. b. Saturated fats are more likely than unsaturated fats to be solid at room temperature. c. Fats that contain more saturated fatty acid residues than unsaturated fatty acid residues are more likely to be solid at room temperature. d. Saturated fats have lower melting points than unsaturated fats. e. Triacylglycerols (triglycerides) always contain three identical fatty acids.

a. Triacylglycerols (triglycerides) are composed of fatty acid residues and glycerol. b. Saturated fats are more likely than unsaturated fats to be solid at room temperature. c. Fats that contain more saturated fatty acid residues than unsaturated fatty acid residues are more likely to be solid at room temperature.

Which of the statements are true? a. Yeast cells that produce more unsaturated fatty acids than saturated fatty acids in response to cold have greater cold tolerance. b. Cell membranes in cold tolerant winter wheat plants have a higher ratio of unsaturated fatty acids to saturated fatty acids than do cold intolerant wheat varieties. c. Cell membranes in reindeer legs (near the hooves) are kept flexible because they have a large number of saturated fatty acids. d. A plant that produces more monounsaturated fatty acids than polyunsaturated fatty acids in its membranes in winter has an increased resistance to freeze damage.

a. Yeast cells that produce more unsaturated fatty acids than saturated fatty acids in response to cold have greater cold tolerance. b. Cell membranes in cold tolerant winter wheat plants have a higher ratio of unsaturated fatty acids to saturated fatty acids than do cold intolerant wheat varieties.

The graph shows how the free‑energy change for the hydrolysis of ATP varies as a function of Mg2+ concentration. Note that pMg = -log[Mg2+] What does the graph tell you about the relationship between Mg2+ concentration and ATP hydrolysis? a. a decrease in [Mg2+] increases the free‑energy change of ATP hydrolysis. b. An increase in [Mg2+] increases the entropy of ATP hydrolysis. c. An increase in [Mg2+] increases the phosphoryl‑transfer potential of ATP. d. A decrease in [Mg2+] increases the rate of ATP hydrolysis.

a. a decrease in [Mg2+] increases the free‑energy change of ATP hydrolysis.

What is a zymogen? a. a protein that is the inactive form of an enzyme b. a protein that digests lipids c. a protein that emulsifies dietary lipids d. a protein that is a precursor to vitamin D

a. a protein that is the inactive form of an enzyme

How do cells use energy? a. active transport b. cellular movement c. biosynthesis of more complex molecules d. ATP hydrolysis

a. active transport b. cellular movement c. biosynthesis of more complex molecules

Identify the factors that directly favor the unloading of oxygen from hemoglobin in the blood near metabolically active tissues. a. an increase in blood acidity near the issues b. an exchange of ions in the erythrocytes c. an increase in blood temperature near the tissues d. the presence of a pressure gradient for oxygen

a. an increase in blood acidity near the tissues c. an increase in blood temperature near the tissues d. the presence of a pressure gradient for oxygen

Odorant receptors and β-adrenergic receptors are 7TM receptors that initiate a signal cascade through G proteins. Which of the following steps is common between the signal-transduction cascade mediated by the odorant receptor and the signal-transduction cascade mediated by the β-adrenergic receptor? a. an increase in intracellular levels of cAMP b. activation of protein kinase A c. an increase in intracellular levels of IP3 d. an influx of cations into the cell

a. an increase in intracellular levels of caMP

Which of the molecules are used as second messengers in signal transduction pathways? a. calcium ions b. caMP c. IP3 d. adenyl cyclase e. insulin

a. calcium ions b. caMP c. IP3

Select the molecules that can form the polar head group of phospholipids. a. choline b. cyclopentanol c. leucine d. inositol

a. choline d. inositol

In fetal hemoglobin (HbF), the two α subunits are replaced with two γ subunits. As a result, fetal hemoglobin has a higher affinity for oxygen than does the mother's adult hemoglobin. The higher oxygen affinity of HbF is due to a. decreased binding of 2,3-BPG b. a decreased amount of cooperativity between the α and β subunits. c. a different mode of binding between the heme and the γ subunits. d. Decreased binding of CO2 to the γ subunits

a. decreased binding of 2,3-BPG

Which factors are associated with sickling of red blood cells in sickle cell disease? a. dehydration b. high temperature c. low pH d. high O2 concentration

a. dehydration b. high temperature c. low pH

The hydrolysis of phosphatidylinositol bisphosphate (PIP2) by phospholipase C generates what two secondary messengers? a. diacylglycerol and inositol 1,4,5‑triphosphate b. diacylglycerol and inositol 4,5‑bisphosphate c. phosphatidylinositol 3,4,5‑triphosphate and cAMP d. free fatty acids and a molecule in which inositol 4,5‑diphosphate is linked via a phosphate to glycerol e. diacylglycerol phosphate and inositol 4,5‑diphosphate

a. diacylglycerol and inositol 1,4,5‑triphosphate

Analyze the pair of compounds. Which of the terms explains the relationship between the two compounds? a. diastereomers b. epimers c. enantiomers d. anomers

a. diastereomers b. epimers

Human blood groups (ABO) are the result of a. differing glycosyltransferases. b. different amino acid sequences found on a protein in the red blood cell membrane. c. the same oligosaccharides being attached to different proteins. d. differing amylases.

a. differing glycosyltransferases.

Analyze the following pair of compounds. Which of the terms explains the relationship between the two compounds a. enantiomers b. diastereomers c. epimers d. anomers

a. enantiomers

Which lipid or lipids must be obtained in the diet? a. essential fatty acids b. endogenous phospholipids c. essential monosaccharides d. endogenous glycogen

a. essential fatty acids

Examine the pairs of molecules and identify the more reduced molecule in each pair. 1. ethanol vs. acetylaldehyde 2. lactate vs. pyruvate 3. succinate vs. fumarate 4. oxalosuccinate vs. isocitrate 5. malate vs. oxaloacetate

a. ethanol b. lactate c. succinate d. isocitrate e. malate

Monosaccharides can be classified based on the number of carbons they contain and the type of group attached to the molecule. Select all the monosaccharides that are correctly paired with their class. a. fructose : hexose ketose b. erythrose : tetrose ketose c. glyceraldehyde : triose aldose d. erythrulose : tetrose aldose e. ribose : hexose aldose d. dihydroxyacetone : triose ketose Epimers are monosaccharide diastereoisomers that have a single asymmetric carbon. Anomers are diastereoisomers in which the hemiacetal carbon of a cyclic monosaccharide is asymmetric. Determine whether each pair of monosaccharides consists of epimers, anomers, or an aldose‑ketose pair. a. epimers b. anomers c. aldose-ketose pair

a. fructose : hexose ketose c. glyceraldehyde : triose aldose f. dihydroxyacetone : triose ketose epimers a. D-glucose and D-mannose b. D-galactose and D-glucose Anomers a. alpha-D-glucose and beta-D-glucose Aldose-ketose pair a. D-glyceraldehyde and dihydroxyacetone b. D-glycose and F-fructose c. D-ribose and D-ribulose

bile salts, which aid in lipid absorption, are synthesized from cholesterol in the liver and released into the small intestine from the a. gall bladder b. large intestine c. pancreas d. stomach

a. gall bladder

Why does glucose yield a positive test with cupric ions, such as those found in Fehling's solution, whereas sucrose does not? a. Glucose is a reducing sugar in equilibrium with its free aldehyde form, whereas sucrose is not. b. Glucose contains a five‑sided ring structure, which is necessary for reaction with cupric ions. c. Glucose is an aldose, whereas sucrose is a dimer of an aldose and a ketose. d. Glucose is a monomer, whereas sucrose is a dimer.

a. glucose is a reducing sugar in equilibrium with its free aldehyde form, whereas sucrose is not

Complete the sentences about the digestion of carbohydrates, triacylglycerols (triglycerides), and proteins. hydrolysis of the ____ bonds of carbohydrates yields ____. Hydrolysis of ___ bonds in triacylglycerols yield products including ____. Hydrolysis of the ____ bonds of proteins produces _____.

a. glycosidic b. monosaccharides c. ester d. fatty acids e. peptide f. amino acids

complete the sentences about heme a. The prosthetic group of hemoglobin and myoglobin is: b. The organic ring combinent of heme is: c. Under normal conditions, the central atom of heme is: d. In ______, the central atom is displaced 0.4 A out of the plane of the porphyrin ring system e. The central atom has _____ bonds: ____ to nitrogen atoms in the porphyrin, one to a _____ residue, and one to oxygen

a. heme b. porphyrin c. Fe2+ d. deoxyhemoglobin e. six, four, histidine

Symporters, such as sodium-glucose linked transporter (SGLT), transport both Na+ and glucose. Na+-K+ATPase uses ATP to transport Na+ ions out of the cell. What is the result of SGLT inhibition? a. inhibition of the Na+-K+ATPase b. increased intracellular K+ c. increased intracellular glucose d. activation of the Na+-K+ATPase

a. inhibition of the Na+-K+ATPase

Once formed, the alpha and beta forms of D-glucose are a. interconvertible only through a linear, noncyclic intermediate with which they are both in equilibrium b. interconvertible directly with no intermediate and are in equilibrium with one another c. found in an equal ratio d. not capable of interconversion

a. interconvertible only through a linear, noncyclic intermediate with which they are both in equilibrium

The energy for the phosphorylation of ADP to ATP can come from molecules with a higher phosphoryl‑transfer potential or from a. ion gradients across membranes b. the energy derived directly from electron carriers giving up electrons. c. the energy released from the interaction between molecules. d. heat

a. ion gradients across membranes

Determine whether each phrase describes ligand‑gated ion channels, voltage‑gated ion channels, or both. a. Ligand-gated ion channels b. voltage-gated ion channels c. both

a. ligand-gated ion channels: an example is the acetylcholine receptor, change conformation in response to a signal molecule binding b. Voltage-gated ion channels: change conformation in response to changing membrane potential c. Both: is a form of passive transport, may participate in an action potential

Select all the organs that play a role in lipid emulsification. a. liver b. gallbladder c. small intestine d. pancreas

a. liver b. gallbladder c. small intestine

The process of digestion in the stomach is carried out in two main ways. One way involves the environment that exists in the stomach. What environmental condition within the stomach promotes digestion? a. low pH b. high pH c. neutral pH d. nonpolar

a. low pH

Select the products of the hydrolysis of each carbohydrate a. maltose b. lactose c. sucrose d. cellulose

a. maltose - glucose b. lactose - glucose + galactose c. sucrose - glucose _ fructose d. cellulose - glucose

Membrane‑associated proteins can be distinguished by the types of interactions they have with the lipid bilayer and their structural motifs. Match each statement to the category of membrane‑associated protein it describes. a. membrane-spanning alpha helix b. membrane-spanning beta strands c. lipid-anchored membrane protein d. peripheral membrane protein

a. membrane-spanning alpha helix is composed of about 20 hydrophobic residues b. membrane-spanning beta strands is an amino acid sequence pattern: nonpolar R group, polar R group (repeats) c. Lipid-anchored membrane protein often contain a residue with covalently attached glycosyl phosphatidylinositol d. Peripheral membrane protein can usually be released from membrane by concentrated salt solutions, often tethered to membrane via a membrane-embedded protein

Complete the sentences about chemical digestion with the appropriate terms. Some of the terms may be used more than once. Carbohydrate digestion begins in the ____ with the enzyme ______. Protein digestion begins in the ____ with the enzyme ______. Nucleic acid digestion begins in the _____ with the enzyme _______. Fat digestion begins in the _____ with the enzyme ______.

a. mouth b. salivary amylase c. stomach d. pepsin e. small intestine f. pancreatic nuclease g. small intestine h. pancreatic lipase

The graph shows the oxygen‑binding curves for myoglobin and hemoglobin. Label the graph and answer the questions. a. use the curves to determine the partial pressure of oxygen at 50% saturation for myoglobin b. use the curves to determine the partial pressure of oxygen at 50% saturation for hemoglobin c. Which protein has a higher affinity for oxygen?

a. myoglobin P50 = 2 b. hemoglobin P50 = 30 c. Myoglobin has a higher affinity for oxygen

A triacylglycerol consists of fatty acids attached to a. one glycerol. b. two glycerol phosphates. c. one glycerol phosphate. 3. three cholesterols.

a. one glycerol

The mKO mice lack an enzyme necessary for the synthesis of the coenzyme NAD. Which type of reaction will be affected in muscles of the mKO mice? a. oxidation-reduction b. carboxyl-group transfer c. intramolecular rearrangements d. acyl-group transfer

a. oxidation-reduction

Determine which statements apply to hemoglobin, myoglobin, or neither: neither

a. oxygen binds irreversibly to this molecule b. carbon monoxide binds at an allosteric site, lowering oxygen binding affinity

Fatty acids are carboxylic acids with a long, unbranched hydrocarbon chain. There are three main classes of fatty acids. Classify the fatty acids as saturated, monounsaturated, or polyunsaturated. a. saturated b. monounsaturated c. polyunsaturated

a. palmitic acid, stearic acid b. oleic acid c. linoleic acid, arachidonic acid

Match the structures and common names of the three fatty acids to their systematic names. a. cis‑Δ9‑Hexadecenoate palmitoleic acid b. n‑Dodecanate lauric acid c. cis, cis‑Δ9, Δ12‑Octadecadienoate linoleic acid

a. palmitoleic acid b. lauric acid c. linoleic acid

The Na+-K+Na+-K+ pump is an active transport system that a. pumps Na+ out of the cell and K+ into the cell. b. pumps both Na+ and K+ into the cell. c. pumps Na+ into the cell and K+ out of the cell. d. provides energy such that Na+ and K+ can move freely in either direction.

a. pumps Na+ out of the cell and K+ into the cell

Select the fundamental properties of all ion channels. a. rapid transport b. voltage-gated c. selectivity d. use active transport

a. rapid transport c. selectivity

What would be expected to lower the 𝑇m for a phospholipid bilayer? a. replacing a lipid containing C18 fatty acids with one containing C16 fatty acids b. replacing a lipid containing unsaturated fatty acids with one containing saturated fatty acids c. decreasing the concentration of phospholipids d. adding ions that bind to charged groups in the polar head groups

a. replacing a lipid containing C18 fatty acids with one containing C16 fatty acids

Complete the passage to describe carbohydrate digestion. Carbohydrate digestion begins with _____ in the ______. This enzyme hydrolyzes ____ to producce maltose, oligosaccharides, and glucose for around 1-2 hours before it is deactivated in the ____. When chyme reaches the duodenum, the _____ is stimulated to produce even larger quantities of this enzyme to continue digestion.

a. salivary amylase b. oral cavity c. starch d. stomach e. pancreas

Characterize each term as pertaining to either simple or facilitated diffusion. a. simple diffusion b. facilitated diffusion

a. simple diffusion: directly through membrane, O2, lipophilic molecules b. facilitated diffusion: via channel, Na+, polar molecules

Calmodulin-dependent protein kinase (CaM kinase)

activates the kinase and enables it to phosphorylate target proteins. Regulate the metabolism of fuel, ionic permeability, neurotransmitter synthesis, and neurotransmitter release through the action of the Ca2+-calmodulin complex.

Monosaccharides

aldehydes or ketones that have two or more hydroxyl groups. The monomers of carbohydrates.

Biological membranes are selectively permeable, allowing certain molecules to cross the membrane, but not others. Classify the molecules or ions depending on how they cross a biological membrane. Note that some of these examples may also utilize active transport to traverse a membrane. However, this question is limited to passive transport processes only. a. simple diffusion b. facilitated diffusion

a. simple diffusion: steroid hormones, CO2 b. Facilitated diffusion: fatty acids, nucleosides, K+

Increased levels of cholecystokinin (CKK) lead to a feeling of satiety. CKK is a family of peptide hormones released from the a. small intestine b. pancreas c. gall bladder d. liver

a. small intestine

Classify each structural feature as characteristic of a sphingolipid or phosphoglyceride a. sphingolipid b. phosphoglyceride

a. sphingosine backbone, one fatty acid chain attached to backbone by an amide b. glycerol backbone, phosphorylated alcohol attached to backbone at C-3

Place the factors, cells, organs, and actions according to whether they stimulate the release of secretin, produce secretin, are a target of secretin, or are an effect of secretin. Four of the choices will not be placed. a. stimulate secretin release b. produce secretin c. target of secretin d. effect of secretin

a. stimulate secretin release: acidic chyme entering the duodenum b. produce secretin: s cells of duodenum c. target of secretin: pancreas d. effect of secretin: stimulates secretion of bicarbonate rich fluid

Select the biochemical roles of cholecystokinin, or CCK. a. stimulates the secretion of bile salts by the gall bladder b. activates pancreatic zymogens to form active enzymes c. stimulates the secretion of digestive enzymes by the pancreas d. stimulates the secretion of sodium bicarbonate by the pancreas

a. stimulates the secretion of bile salts by the gall bladder c. stimulates the secretion of digestive enzymes by the pancreas

Select the scenarios which, according to the Bohr effect, result in hemoglobin's release of bound oxygen a. The concentration of hydrogen ions in the blood increases b. The pH of blood increases c. Oxygen levels in the blood increase d. Carbon dioxide levels in the blood increase

a. the concentration of hydrogen ions in the blood increases d. Carbon dioxide levels in the blood increase

ATP is a source of free energy that drives unfavorable reactions. Which of the processes are coupled to the dephosphorylation of ATP? a. the endergonic reaction forming glucose‑6‑phosphate b. reversible isomerization of glucose‑6‑phosphate to fructose‑6‑phosphate during glucose catabolism c. ion transport with the concentration gradient d. myosin action during muscle contraction e. de novo (from scratch) anabolism of nucleotides One reason that ATP is a source of energy is that the products of ATP hydrolysis have less free energy than the reactants. Why? a. formation of ion pairs involving ATP b. hydrogen bonding between free phosphate and water c. resonance stabilization of free phosphate d. electrostatic repulsion in ATP

a. the endergonic reaction forming glucose‑6‑phosphate d. myosin action during muscle contraction e. de novo (from scratch) anabolism of nucleotides b. hydrogen bonding between free phosphate and water c. resonance stabilization of free phosphate d. electrostatic repulsion in ATP

Determine which statements apply to hemoglobin, myoglobin, or neither: myoglobin

a. the oxygen dissociation curve is hyperbolic in shape b. this molecule has a greater affinity for oxygen

Determine which statements apply to hemoglobin, myoglobin, or neither: hemoglobin

a. the oxygen dissociation curve is sigmoidal in shape (S shaped) b. As oxygen binds to this molecule the shape of the molecule changes, enhancing further oxygen binding c. The binding pattern for this molecule is considered cooperative d. This molecule delivers oxygen more efficiently to tissues

Although salts of fatty acids form micelles, phospholipids and glycolipids form bimolecular sheets due to a. the presence of two fatty acyl chains. b. the differing interaction between polar head groups and water. c. the differing interaction of hydrophobic fatty acyl chains. d. the differing interaction between polar head groups with one another.

a. the presence of two fatty acyl chains.

Why are membrane receptor proteins often used to transfer information from the cell's environment to its interior? a. the signal molecule is too large or too polar to pass through the cell membrane b. The molecular signal is not soluble in the interior of the cell c. The molecular signal would overstimulate the signaling pathway if it were internalized d. The signal molecule is transported into the cell by the receptor

a. the signal molecule is too large or too polar to pass through the cell membrane

Classify the characteristics of triacylglycerols and phosphoglycerides. a. triacylglucerols b. phosphoglycerides

a. three fatty acid chains, energy storage b. membrane component, two fatty acid chains c. alcohol group d. phosphate group

The oxygen-hemoglobin dissociation curve describes the percent oxygen saturation of hemoglobin as a function of the partial pressure of oxygen (PO2) in the surrounding fluid. As the PO2 increases on the horizontal axis, the oxygen saturation percentage also increases on the vertical axis. In comparison to that of adult hemoglobin, how is the fetal oxygen-hemoglobin dissociation curve shifted? a. to the left of the adult curve, indicating a higher oxygen affinity of fetal hemoglobin b. to the left of the adult curve, indicating a lower oxygen affinity of fetal hemoglobin c. to the right of the adult curve, indicating a higher oxygen affinity of fetal hemoglobin d. to the right of the adult curve, indicating a lower oxygen affinity of fetal hemoglobin

a. to the left of the adult curve, indicating a higher oxygen affinity of fetal hemoglobin

The proteolytic enzyme trypsin is produced in the pancreas as the zymogen trypsinogen. Trypsinogen is cleaved to yield the active form. Trypsin, in turn, activates other pancreatic zymogens. Select every enzyme that is used in the activation of trypsinogen. a. trypsin b. enteropeptidase (enterokinase) c. chymotrypsin d. fibrin Select every pancreatic zymogen that is directly activated by trypsin. a. proteolastase b. prolipase c. procarboxypeptidase d. chymotrypsinogen

a. trypsin b. enteropeptidase (enterokinase) a. proteolastase b. prolipase c. procarboxypeptidase d. chymotrypsinogen

Transient changes in the permeability of the neuron membrane to sodium and potassium ions leads to action potentials. Which membrane protein moves sodium ions into the cell in response to neuron membrane depolarization? a. voltage-gated sodium channel b. Na+-K+antiporter c. Na+-K+ ATPase d. ligand-gated sodium channel

a. voltage-gated sodium channel

anomer

an additional asymmetric center created when a cyclic hemiacetal is formed, generating yet another diasteromeric form of sugars. The designation means that the hydroxyl group attached to C-1 is below the plane of the ring; β means that it is above the plane of the ring.

Fatty acid is shown. Which of the designations are accurate for the fatty acid? a. 4,7,10,13-nonadecatetraenoic acid b. 20:4(Δ5,8,11,1420:4(Δ5,8,11,14) c. 20:4(Δ6,9,12,1520:4(Δ6,9,12,15) d. ω‑6 fatty acid e. ω-3 fatty acid

b. 20:4(Δ5,8,11,1420:4(Δ5,8,11,14) d. ω‑6 fatty acid

Signal transduction is part of a cell's response to an external signal. Although signal transduction pathways can differ in their details, there are some common elements. Select the six statements that accurately describe signal transduction pathways. a. A ligand phosphorylates protein residues, ending the signaling cascade inside the cell. b. A receptor may pass on a signal by interacting with another protein or by acting as an enzyme. c. A ligand, such as a hormone, binds to a specific cell surface receptor on a target cell. d. Phosphatases remove phosphoryl groups from polypeptides, regulating a cell's response. e. A second messenger carries a signal from a tissue or organ to a target cell. f. A receptor changes conformation upon binding, transmitting a signal across the cell membrane. g. Signal transduction cascades directly transmit a single stimulus to a single target. h. Signal transduction cascades, often involving protein kinases, amplify a signal intracellularly. i. A second messenger may carry a signal from the cell membrane to an organelle.

b. A receptor may pass on a signal by interacting with another protein or by acting as an enzyme. c. A ligand, such as a hormone, binds to a specific cell surface receptor on a target cell. d. Phosphatases remove phosphoryl groups from polypeptides, regulating a cell's response. f. A receptor changes conformation upon binding, transmitting a signal across the cell membrane. h. Signal transduction cascades, often involving protein kinases, amplify a signal intracellularly. i. A second messenger may carry a signal from the cell membrane to an organelle.

Sucrose, a disaccharide, is often added as a sweetener, but it is not as sweet as its constituent monosaccharides D‑glucose and D‑fructose. Besides enhancing sweetness, fructose has hygroscopic properties that improve the texture of foods, reducing crystallization and increasing moisture. In the food industry, hydrolyzed sucrose is called invert sugar, and the yeast enzyme that hydrolyzes it is called invertase. The hydrolysis reaction is generally monitored by measuring the specific rotation of the solution, which is positive (+66.4∘)(+66.4∘) for sucrose, but becomes negative (inverts) with the formation of D‑glucose (specific rotation=+52.7∘)(specific rotation=+52.7∘) and D‑fructose (specific rotation=−92∘).(specific rotation=−92∘). Consider the chemistry of the glycosidic bond. Which methods could be used to hydrolyze sucrose to invert sugar nonenzymatically in your kitchen at home? a. Add water to the solution and cool in an ice bath. b. Add lemon juice to the solution in a warm water bath. c. Boil the sucrose solution in water. d. Add baking soda solution (pH≈9) to the solution in a water bath.

b. Add lemon juice to the solution in a warm water bath. c. Boil the sucrose solution in water.

Which statements about reducing sugars are true? a. A reducing sugar will not react with the Cu2+ in Benedict's reagent b. D‑Glucose (an aldose) is a reducing sugar. c. A disaccharide with its anomeric carbons joined by the glycosidic linkage cannot be a reducing sugar. d. Reducing sugars contain ketone groups instead of aldehyde groups. e. The oxidation of a reducing sugar forms a carboxylic acid sugar.

b. D‑Glucose (an aldose) is a reducing sugar. c. A disaccharide with its anomeric carbons joined by the glycosidic linkage cannot be a reducing sugar. e. The oxidation of a reducing sugar forms a carboxylic acid sugar.

Consider the structure of calmodulin. Identify the correct statements about calmodulin. a. Calmodulin contains two Ca2+ binding sites b. Each calcium‑binding domain in calmodulin is formed from a helix‑loop‑helix motif. c. Calmodulin is a structural subunit of proteins such as CaM kinase. d. A calcium ion is bound in the loop of an EF hand. e. Binding of Ca2+ activates calmodulin f. Calmodulin contains a central, flexible β sheet that enables it to wrap around another protein, inhibiting the protein's activity.

b. Each calcium‑binding domain in calmodulin is formed from a helix‑loop‑helix motif. d. A calcium ion is bound in the loop of an EF hand. e. Binding of Ca2+ activates calmodulin

Which step occurs immediately after epinephrine binds to the β‑adrenergic receptor? a. β‑arrestin binds to the receptor. b. GTP displaces GDP in Gαs. c. cAMP binds to protein kinase A d. Gαs diffuses to adenylate cyclase. e. Gαs diffuses away from Gβγ.

b. GTP displaces GDP in Gαs.

Which of the following statements about Ngb-H64Q is true? a. Ngb-H64Q has a higher affinity than hemoglobin for carbon monoxide, whereas hemoglobin has a higher affinity than Ngb-H64Q for oxygen. b. Ngb-H64Q has a higher affinity than hemoglobin for both carbon monoxide and oxygen. However, Ngb-H64Q binds to carbon monoxide with a higher affinity than to oxygen. c. Ngb-H64Q binds to oxygen and carbon monoxide with equal affinity. d. Ngb-H64Q has a higher affinity for oxygen than it does for carbon monoxide.

b. Ngb-H64Q has a higher affinity than hemoglobin for both carbon monoxide and oxygen. However, Ngb-H64Q binds to carbon monoxide with a higher affinity than to oxygen.

select the statements that accurately describe receptor tyrosine kinases (RTKs) a. The α subunit contains seven α helices that span the membrane. b. RTKs are usually monomeric in the absence of a ligand. c. The structure includes a transmembrane helix. d. The intracellular domain has kinase domains. e. A ligand binds to the extracellular domain. f. GTPase activity is required for autophosphorylation (cross‑phosphorylation).

b. RTKs are usually monomeric in the absence of a ligand. c. The structure includes a transmembrane helix. d. The intracellular domain has kinase domains. e. A ligand binds to the extracellular domain.

Which three statements accurately describe the blood buffering systems in humans? a. The blood buffering system utilizes the acetic acid/acetate conjugate acid/base pair. b. The blood buffering system maintains the pH of blood near 7.4. c. The blood buffering system is facilitated by the enzyme carbonic anhydrase, which interconverts carbon dioxide and water to carbonic acid, ionizing into bicarbonate and H+ d. The blood buffering system utilizes the H2CO3/HCO3- conjugate acid/base pair. e. The blood buffering system depends on the ionization of H2PO4-

b. The blood buffering system maintains the pH of blood near 7.4 c. The blood buffering system is facilitated by the enzyme carbonic anhydrase, which interconverts carbon dioxide and water to carbonic acid, ionizing into bicarbonate and H+ d. The blood buffering system utilizes the H2CO3/HCO3- conjugate acid/base pair

Which statement is NOT true of P‑type ATPases? a. Their widespread presence in living organisms suggests an early evolutionary origin for P‑type ATPases. b. They lack specificity, and a given P‑type ATPase can often transport different ions or molecules. c. All P‑type ATPases convert between different conformational states to transport ions or molecules. d. All P‑type ATPases use a similar mechanism of action involving a phosphorylated intermediate.

b. They lack specificity, and a given P‑type ATPase can often transport different ions or molecules.

Unsaturated fatty acids have double bonds that are in the cis configuration. One of the consequences of this configuration is a. enhanced flexibility of the molecule b. a bend in the molecule c. an alteration in the number of carbons in the molecule d. an alteration in the charge of the molecule

b. a bend in the molecule

On the graph, the curve labeled No Cholesterol shows the fluidity of the fatty acids of a phospholipid bilayer as a function of temperature. The curve labeled ++ Cholesterol shows the fluidity in the presence of cholesterol. The transition temperature, Tm,Tm, is the temperature at which membranes transition between a rigid state and a more fluid state. What is the effect of cholesterol in the cell membrane? a. Cholesterol enables a sharp increase in fluidity at the transition temperature. b. Cholesterol moderates membrane fluidity at low and high temperatures. c. Cholesterol reduces permeability to polar molecules over a wide temperature range. d. Cholesterol increases membrane fluidity at all temperatures.

b. cholesterol moderates membrane fluidity at low and high temperatures

Acyl groups generated during metabolic processes involving carbohydrates and fatty acids are activated by attachment to a. glyceraldehyde 3‑phosphate. b. coenzyme A c. biotin d. pyruvate

b. coenzyme A

Hemoglobin is a protein in red blood cells that binds to oxygen. Which physiological changes that naturally occur in the body reduce hemoglobin's affinity for oxygen? a. accumulation of nitrogen b. decrease in pH c. decrease in temperature d. accumulation of carbon dioxide

b. decrease in pH d. accumulation of carbon dioxide

D-glucose and L-glucose are a. epimers b. enantiomers c. anomers d. diastereoisomers

b. enantiomers

Which of the terms explain the relationship between the two compounds? a. enantiomers b. epimers c. anomers d. diastereomers

b. epimers c. anomers d. diastereomers

Pancreatic lipases hydrolyze triacylglycerols (triglycerides) that have been emulsified by bile. Select the products of the pancreatic lipase digestion of a triacylglycerol. a. acyl-CoA b. fatty acids c. triacylglycerol d. glycerol e. monoacylglycerol f. diacylglycerol

b. fatty acids d. glycerol e. monoacylglycerol f. diacylglycerol

Glycoproteins are proteins to which carbohydrates have been covalently attached. The amino acid R groups that serve as the sites for carbohydrate attachment include a. carboxyl groups b. hydroxyl groups c. thiol groups d. aromatic groups

b. hydroxyl groups

Identify factors that account for the high phosphoryl‑transfer potential of the nucleoside triphosphates, NTPs. a. low standard free energy of hydrolysis b. increase in entropy c. decrease in entropy d. resonance stabilization e. stabilization by hydration

b. increase in entropy d. resonance stabilization e. stabilization by hydration

Select the structural features common to all membrane-bound receptors a. seven transmembrane helices b. intracellular domain undergoes structural changes upon extracellular ligand binding c. signal molecule binding site on the extracellular domain d. kinase domain

b. intracellular domain undergoes structural changes upon extracellular ligand binding c. signal molecule binding site on the extracellular domain

In the lungs, oxygen diffuses into the blood and is loaded onto hemoglobin for transport. In the tissues, oxygen is unloaded from hemoglobin and diffuses from the blood into nearby cells. What drives the diffusion of oxygen? a. Body temperature b. Partial pressure of oxygen c. blood pH d. partial pressure of carbon dioxide e. concentration of nitric acid

b. partial pressure of oxygen

Glycolysis is the process by which energy is harvested from glucose by living things. Several of the reactions of glycolysis are thermodynamically unfavorable (nonspontaneous), but proceed when they are coupled with other reactions. Reaction A: Pi+glucose⟶glucose-6-phosphate+H2OΔ𝐺=13.8 kJ/mol Reaction B: Pi+fructose-6-phosphate⟶fructose-1,6-bisphosphate+H2OΔ𝐺=16.3 kJ/mol Reaction C: ATP+H2O⟶ADP+PiΔ𝐺=−30.5 kJ/mol Select every unfavorable reaction. a. Reaction C b. Reaction A c. Reaction B Select every set of coupled reactions where the overall reaction is favorable. a. reactions B and C b. reactions A and C c. reactions A and B What is the net change in free energy if one set of reactions from the previous question is coupled so that the overall reaction is favorable? Note that if you selected more than one set of coupled reactions as favorable in the previous question, you may enter the net change for any one of your selected sets.

b. reaction A c. reaction C a. reactions B and C b. reactions A and C ∆G = -14.2 kJ/mol

The hydrolysis of ATP drives metabolism by a. providing energy in the form of heat. b. shifting the equilibrium of coupled reactions. c. providing part of the activation energy for a key reaction. d. altering the conformation of metabolic reactants.

b. shifting the equilibrium of coupled reactions.

Rapidly metabolizing tissues generate large amounts of protons and carbon dioxide. The result of this increase in proton and carbon dioxide is that the oxygen-binding curve of hemoglobin a. shifts to the left, meaning more binding of O2 at lower O2 levels b. Shifts to the right, meaning lower saturation at higher O2 levels c. Changes shape from sigmoidal to hyperbolic d. remains the same

b. shifts to the right, meaning lower saturation at higher O2 levels

Starch is a common carbohydrate that is found in vegetables and grains. Which statement describes the structure of starch? a. starch is a monomer of glucose b. starch is a polymer of glucose c. Starch is a polymer of mannose. d. Starch is a polymer of cellulose. Which of the statements is true regarding the digestion of starch and cellulose by humans? a. Humans are able to digest both starch and cellulose. b. Humans have the enzymes required to hydrolyze the beta linkages in starch. c. Humans lack the enzymes required to hydrolyze the beta linkages in cellulose. d. Cellulose contains alpha linkages, which humans lack the enzymes required to hydrolyze.

b. starch is a polymer of glucose c. Humans lack the enzymes required to hydrolyze the beta linkages in cellulose.

All of the cells in the body need oxygen. Hemoglobin molecules in red blood cells transport oxygen through the bloodstream. Oxygen is loaded onto hemoglobin molecules in the lungs and unloaded from the hemoglobin molecules in the tissues. What drives the unloading of oxygen from hemoglobin molecules in the tissues? a. the low partial pressure of carbon dioxide in the tissues b. the low partial pressure of oxygen in the tissues c. the high partial pressure of carbon dioxide in the tissues d. the high partial pressure of oxygen in the tissues

b. the low partial pressure of oxygen in the tissues

In the movement of small molecules across a lipid bilayer, the permeability coefficient can be correlated with a. the size of the molecule. b. the solubility of the molecule in a nonpolar solvent. c. the flexibility of the molecule. d. the interaction of the molecule with the polar head groups.

b. the solubility of the molecule in a nonpolar solvent

Which is the best definition of chylomicrons? a. enzymes synthesized in the intestines that transport cholesterol and fat‑soluble vitamins into epithelial cells b. water‑soluble lipoproteins synthesized from triglycerides in epithelial cells and transported to the lymphatic system c. fatty droplets removed from large globules of triglycerides by bile salts and transported to the lymphatic system d. fatty droplets containing lecithin that transport cholesterol and fat‑soluble vitamins into epithelial cells

b. water‑soluble lipoproteins synthesized from triglycerides in epithelial cells and transported to the lymphatic system

Linking together one glucose, one mannose, and one galactose molecule can form how many different trisaccharides? a. 18 b. 1 c. 12,288 d. 216 e. 6

c. 12,288

Acarbose and miglitol are competitive inhibitors of 𝛼-glucosidase. Identify the statement that describes how acarbose and miglitol decrease glucose absorption after a meal. a. Acarbose and miglitol bind to a regulatory site on 𝛼-glucosidase and inhibit the digestion of oligosaccharides in the small intestine. b. Acarbose and miglitol bind to a regulatory site on 𝛼-glucosidase and change the conformation of the enzyme to the inactive T state. c. Acarbose and miglitol bind to the 𝛼-glucosidase active site and prevent the enzyme from binding to oligosaccharides in the small intestine and breaking them down to glucose. d. Acarbose and miglitol bind to the 𝛼-glucosidase active site and prevent the enzyme from releasing the glucose formed from oligosaccharide breakdown in the small intestine.

c. Acarbose and miglitol bind to the 𝛼-glucosidase active site and prevent the enzyme from binding to oligosaccharides in the small intestine and breaking them down to glucose.

The furanose form of fructose is generated by the formation of a hemiketal, involving the attack of the hydroxyl group on a. C-2 by C-6 b. C-6 by C-1 c. C-5 by C-2 d. C-6 by C-2

c. C-5 by C-2

In addition to transporting oxygen from the lungs to the tissues, hemoglobin is also involved in transporting CO2 from the tissues to the lungs. How does hemoglobin transport CO2 from the tissues to the lungs? a. Carbon dioxide competes for the 2,3‑BPG‑binding site. b. Carbon dioxide binds to the carboxy terminus of hemoglobin. c. Carbon dioxide reacts with an amino group, stabilizing the R state. d. Carbon dioxide competes for the oxygen‑binding site on the heme.

c. Carbon dioxide reacts with an amino group, stabilizing the R state

You prepare a cell line that overexpresses a mutant form of epidermal growth factor receptor, or EGFR, in which the entire intracellular region of the receptor has been deleted. Predict the effect of overexpression of this construct on epidermal growth factor (EGF) signaling in this cell line. What will be the effect of the overexpression of this truncated receptor? a. EGFR will not bind growth factor, resulting in cell proliferation. b. EGFR will activate other proteins without dimerization, causing uncontrolled cell growth. c. EGFR will dimerize but will not cross‑phosphorylate, inhibiting normal cell growth. d. EGFR will not form a dimer in the presence of EGF, stopping normal cell growth.

c. EGFR will dimerize but will not cross‑phosphorylate, inhibiting normal cell growth.

Identify the parts of the G protein shown in the image. Which of the subunits, when activated, associates with adenylyl cyclase (adenylate cyclase) and enables it to assume a more catalytically active conformation? a. Gβγ b. Gβ c. Gα d. Gγ

c. Gα

What is a consequence of enteropeptidase deficiency? a. The hormone cholecystokinin is not released. b. The hormone secretin is not released. c. Peptidases are not activated in the small intestine. d. Pepsinogen is not converted to pepsin.

c. Peptidases are not activated in the small intestine.

A glycolipid is: a. a lipid molecule that contains a phosphate group b. a lipid molecule produced during glycolysis c. a lipid molecule that contains at least one carbohydrate unit d. a molecule produced during the breakdown of glycogen

c. a lipid molecule that contains at least one carbohydrate unit

The most common way in which integral membrane proteins span the membrane is in a. single strands with no secondary structure b. beta-sheet structures c. alpha-helical segments d. paired alpha-helical and beta-sleep segments

c. alpha-helical segments

How does cAMP regulate protein kinase A? a. cAMP binds to the regulatory subunits of protein kinase A, promoting the exchange of bound GDP for GTP, which releases the catalytic subunits to carry out phosphorylation. b. cAMP binds to the catalytic subunits, causing a conformational change that leads to increased activity. c. cAMP binds to the regulatory subunits of protein kinase A, causing a conformational change that releases the catalytic subunits to carry out phosphorylation. d. cAMP increases the transcription of the genes for protein kinase A. e. cAMP phosphorylates protein kinase A, causing a conformational change that leads to increased activity.

c. cAMP binds to the regulatory subunits of protein kinase A, causing a conformational change that releases the catalytic subunits to carry out phosphorylation.

What material in vertebrate muscle serves as a reservoir for high‑energy phosphate groups? a. phosphoenolpyruvate b. glucose 6‑phosphate c. creatine phosphate d. glycogen

c. creatine phosphate

Synthesis of some disaccharides relies on the activation of glucose by UTP to form UDP‑glucose. First, UDP‑glucose is converted to UDP‑galactose. Then, UDP‑galactose is combined with another glucose unit to form a disaccharide. Identify the disaccharide. a. UDP-galactose + glucose --> ____ + UDP

lactose

Sodium and potassium ion channels have several negatively charged residues at the entry to the channel. Identify the bases on which K+ channels specifically select for K+ ions, in other words, why do K+ channels not enable Na+ ions to cross the membrane? a. charge, Na is slightly less electronegative than K and does not interact with the channel carbonyl groups b. charge, Na is slightly more electronegative than K and does not interact with the channel carbonyl groups c. energy cost, it is too energetically costly to dehydrate Na+ d. ionic radius, Na+ is too small e. ionic radius, Na+ is too big

c. energy cost, it is too energetically costly to dehydrate Na+ d. ionic radius, Na+ is too small

In biological systems, fatty acids usually contain an even number of carbon atoms. Which fatty acids are MOST common in biological systems? a. fatty acids with 12 and 14 carbons b. fatty acids with 14 and 16 carbons c. fatty acids with 16 and 18 carbons d. fatty acids with 18 and 20 carbons

c. fatty acids with 16 and 18 carbons

Is the molecule shown hydrophilic, hydrophobic, or amphipathic (amphiphilic)? a. hydrophobic b. amphipathic c. hydrophilic

c. hydrophilic

Chylomicrons are a. transported from the intestinal lumen to mucosal cells b. micelles c. lipoprotein transport particles d. comprised of disaccharides and protein

c. lipoprotein transport particles

Which molecules are bound to hemoglobin when hemoglobin is in the R state a. CO2 b. 2,3-biphosphoglycerate c. oxygen d. Fe3+ e. Fe2+

c. oxygen e. Fe2+

Advanced glycation end products are a. solely composed of long carbohydrate polymers on free amino groups. b. products of a reaction between sucrose and proteins. c. products of reactions between reducing sugars and free amino groups. d. two or more sugars joined together in a covalent bond.

c. products of reactions between reducing sugars and free amino groups

Which factor does NOT contribute to the high phosphoryl‑transfer potential of ATP? a. the ability of water to interact more favorably with the products of ATP hydrolysis than with ATP itself b. charge repulsion c. the adenine ring structure d. resonance stabilization

c. the adenine ring structure

Draw the product of the reaction between a ketone and an alcohol. Include all hydrogen atoms in the product. How would you classify the product of the reaction? Note that a hemiacetal formed from a ketone is also called a hemiketal; an acetal formed from a ketone is also called a ketal. a. the product is an alcohol b. the product is a ketone c. the product is a hemiketal d. the product is a ketal

c. the product is a hemiketal

The standard free energy, Δ𝐺∘′, value for an enzymatic reaction with several components is the sum of the Δ𝐺∘′ values for each component. Creatine kinase catalyzes the transfer of a phosphate group from creatine phosphate to ADP to form ATP. creatine phosphate+H2O⟶creatine+Pi ADP+Pi⟶ATP+H2O The Δ𝐺∘′ of hydrolysis for each phosphate‑containing compound appears in the table. a. −43.1 kJ⋅mol−1 and −30.5 kJ⋅mol−1 b. 43.1 kJ⋅mol−1 and 30.5 kJ⋅mol−1 c. −43.1 kJ⋅mol−1 and 30.5 kJ⋅mol−1 d. 43.1 kJ⋅mol−1 and −30.5 kJ⋅mol−1 Which component of the creatine kinase reaction supplies the free energy for the overall reaction? a. creatine+Pi⟶creatine phosphate+H2O b. ATP+H2O⟶ADP+Pi c. creatine phosphate+H2O⟶creatine+Pi d. ADP+Pi⟶ATP+H2O

c. −43.1 kJ⋅mol−1 and 30.5 kJ⋅mol−1 c. creatine phosphate+H2O⟶creatine+Pi

The specific rotations of the α and β anomers of D-glucose are +112∘+112∘ and +18.7∘,+18.7∘, respectively. Specific rotation, [𝛼]D,[α]D, is defined as the observed rotation of light of wavelength of 589 nm589 nm (the D line of a sodium lamp) passing through 10 cm10 cm of a 1 g⋅mL−11 g⋅mL−1 solution of a sample. When a crystalline sample of α‑D‑glucose is dissolved in water, the specific rotation decreases from 112∘112∘ to an equilibrium value of 52.7∘.of 52.7∘. On the basis of this result, calculate the proportions of the α and β anomers at equilibrium. Assume that the concentration of the open‑chain form is negligible. What are the proportions of the α and β anomers at equilibrium? a. 𝛼=0.64, 𝛽=0.36 b. 𝛼=0.59, 𝛽=0.34 c. 𝛼=0.36, 𝛽=0.64 d. 𝛼=0.50, 𝛽=0.50

c. 𝛼=0.36, 𝛽=0.64

micelles

carry the final digestion products (free fatty aids and monoacylglycerol) to the plasma membrane of the intestinal epithelial cells where they will be absorbed. Globular structures formed by small lipids in aqueous solutions. The polar head groups of the fatty acids and monoacylglycerol are in contact with the aqueous solution and the hydrocarbon chains are sequestered in the interior of the micelle. Micelle formation is also facilitated by bile salts.

fatty acids

chains of hydrogen-bearing carbon atoms, called hydrocarbons, that terminate with carboxylic acids. They vary in length and may have one or more double bonds, depending on the fat. Two key roles for fatty acids are as fuels and as building blocks for membrane lipids. Can be saturated (composed entirely of single bonds) or unsaturated (contain one or more double or triple bonds)

lipid bilayer

closed bimolecular sheets formed in an aqueous media that serve as a barrier against the flow of molecules. Hydrophilic heads of phospholipids interact with the aqueous intracellular and extracellular environments and hydrophobic tails are oriented within the bilayer facing each other.

lipid rafts

complexes formed with cholesterol, fatty acid components of lipids , and specific proteins that concentrate within small and highly dynamic regions inside membranes. These structures moderate membrane fluidity by making membranes less fluid but also less subject to phase transitions. They play a role in concentrating proteins for signal-transduction pathways, regulate membrane curvature and budding, and facilitate the interaction between the extracellular matrix and the cytoskeleton.

Phosphoinositide cascade

converts extracellular signals into intracellular ones. The intracellular messengers formed by activation of this pathway arise from the cleavage of PIP2

Assume that the complete combustion of one mole of glucose to carbon dioxide and water liberates 2870 kJ/mol (Δ⁢G°′=−2870 kJ/mol). If one contraction cycle in muscle requires 65 kJ, and the energy from the combustion of glucose is converted with an efficiency of 43% to contraction, how many contraction cycles could theoretically be fueled by the complete combustion of one mole of glucose? Round your answer to the nearest whole number.

cycles per mole glucose = 19

Which statement correctly describes metabolic reactions? a. Intermediary metabolism breaks down material and transforms fuels into cellular energy, whereas metabolism requires energy for biosynthesis. b. Anabolic processes break down material and transform fuels into cellular energy, whereas catabolic processes require energy for biosynthesis. c. Metabolism breaks down material and transform fuels into cellular energy, whereas intermediary metabolism requires energy for biosynthesis. d. Catabolic processes break down material and transforms fuels into cellular energy, whereas anabolic processes require energy for biosynthesis.

d. Catabolic processes break down material and transforms fuels into cellular energy, whereas anabolic processes require energy for biosynthesis.

in phosphoglycerides, fatty acids are esterified at a. C‑1 and C‑3 of glycerol. b. any two of the three glycerol carbons. c. a glycerol carbon and the phosphate group. d. C‑1 and C‑2 of glycerol.

d. C‑1 and C‑2 of glycerol.

How does hemoglobin function as a pH buffer? a. Hemoglobin releases hydrogen ions when oxygen exits the red blood cell. b. Hemoglobin binds hydrogen ions when carbon dioxide exits the red blood cell. c. Hemoglobin releases hydrogen ions after carbon dioxide enters the red blood cell. d. Hemoglobin binds hydrogen ions after carbon dioxide enters the red blood cell.

d. Hemoglobin binds hydrogen ions after carbon dioxide enters the red blood cell

Identify the property of lipids that makes their digestion more complicated than that of carbohydrates and proteins. a. Lipids cannot be digested by hydrolases. b. Lipases are soluble in lipids. c. Lipids are unaffected by mixing in the stomach. d. Lipids are not water soluble. Select the processes that make lipids accessible for the digestion. a. Lipases degrade triacylglycerols into fatty acids. b. Micelles carry fatty acids to the intestinal membrane. c. The low pH of the stomach breaks down fatty acids. d. Lipid droplets and water mix into an emulsion in the stomach.

d. Lipids are not water soluble a. Lipases degrade triacylglycerols into fatty acids. b. Micelles carry fatty acids to the intestinal membrane. d. Lipid droplets and water mix into an emulsion in the stomach.

Each chain of hemoglobin can be viewed as existing in either the R state or the T state. What is the relationship between these two hemoglobin states and oxygen binding? a. Oxygen binds with greater affinity to the T state, and oxygen binding converts hemoglobin to the R state. b. The conversion between the R and T states is not directly related to oxygen binding. c. The conversion between the R and T states takes place only when 2,3‑BPG is bound. d. Oxygen binds with greater affinity to the R state, and oxygen binding converts hemoglobin to the R state.

d. Oxygen binds with greater affinity to the R state, and oxygen binding converts hemoglobin to the R state

Secondary transporters, or cotransporters, can be divided into symporters and antiporters. What distinguishes symporters from antiporters? a. Symporters use the energy from one molecule moving down its concentration gradient to drive the movement of a second molecule in the opposite direction against its concentration gradient. Conversely, antiporters drive the movement of molecules in the same direction. b. Symporters use the energy from one molecule moving down its concentration gradient to drive the movement of a second molecule, whereas antiporters use the energy from both molecules for transport. c. Symporters allow the same molecule to be moved in both directions, whereas antiporters allow it to move in only one direction. d. Symporters use the energy from one molecule moving down its concentration gradient to drive the movement of a second molecule in the same direction against its concentration gradient. Conversely, antiporters drive the movement of molecules in opposite directions.

d. Symporters use the energy from one molecule moving down its concentration gradient to drive the movement of a second molecule in the same direction against its concentration gradient. Conversely, antiporters drive the movement of molecules in opposite directions.

What do micelles and chylomicrons have in common? a. they both contain protein b. they both contain carbohydrate c. they both contain triacylglycerol d. they both contain fatty acids

d. They both contain fatty acids.

In a metabolic pathway, a. a reaction with a positive ∆G can occur if there is an increase in the concentration of the reaction's products. b. It is ∆G°, not ∆G that determins whether a reaction can occur c. a reaction with a positive ∆G cannot occur d. a reaction with a positive ∆G can occur if it is coupled to a reaction with a more negative ∆G

d. a reaction with a positive ∆G can occur if it is coupled to a reaction with a more negative ∆G

Saliva is an aqueous solution of which ion? a. Na+ b. K+ c. HCO3- d. all three ions

d. all three ions

What factor enables Ca2+ to regulate many biochemical processes a. its ability to block Na+ and K+ channels b. The large concentration of calcium ions in the cell c. competition with other divalent cations such as the magnesium ion d. binding to calmodulin e. the requirement of divalent cation cofactors in the hydrolysis of ATP

d. binding to calmodulin

Which molecules bind to receptors that have intracellular tyrosine kinase domains? a. Ras b. caMP c. epinephrine d. epidermal growth factor (EGF) e. calcium ion f. insulin

d. epidermal growth factor (EGF) f. insulin

some lipid molecules are said to be amphipathic, meaning that they a. have asymmetric carbons and can exist in left and right handed forms b. carry a positive charge on one end and a negative charge on the other end c. are capable of moving rapidly from one side of a lipid bilayer to the other d. have a dual nature with part of the molecule being hydrophobic and the other part being hydrophilic

d. have a dual nature with part of the molecule being hydrophobic and the other part being hydrophilic

GTPase activity of G proteins is important because a. hydrolysis of the phosphoric anhydride bond provides energy for signal transduction. b. the phosphate released is an important secondary messenger. c. the phosphate is used by downstream kinases to phosphorylate target enzymes. d. it provides a method whereby the initial signal can be terminated. e. the G proteins are active only when GDP is bound to them

d. it provides a method whereby the initial signal can be terminated

polysaccharide

large polymeric oligosaccharides, formed by the linkage of multiple monosaccharides. They play vital roles in energy storage and in maintaining the structural integrity of an organism.

Glucose is mobilized for ATP generation in muscle in response to epinephrine, which activates Gαs. Cyclic AMP phosphodiesterase is an enzyme that converts cyclic AMP (cAMP) into AMP. How would an inhibitor of cAMP phosphodiesterase affect glucose mobilization in muscle? a. It would reduce cAMP levels and inhibit glucose mobilization. b. It would increase AMP concentration, thereby increasing glucose mobilization. c. It would decrease AMP concentrations, reducing glucose mobilization. d. It would maintain high cAMP levels and elevate glucose mobilization

d. it would maintain high cAMP levels and elevate glucose mobilization

Select the statement that best describes homeostasis. a. internal mechanisms that decrease physiological variables b. spontaneous induction of changes to alter the internal state of the body c. prevention of changes from happening within the human body d. maintenance of a dynamic state of equilibrium within the human body

d. maintenance of a dynamic state of equilibrium within the human body

Hemoglobin S, the abnormal form of hemoglobin responsible for sickle‑cell anemia, is the result of a mutation in the gene for the β subunit. The hemoglobin S mutation changes a a. negatively charged amino acid R group to a positively charged amino acid R group b. Hydrophobic amino acid R group to a positively charged amino acid R group c. Positively charged amino acid R group to a negatively charged amino acid R group d. Negatively charged amino acid R group to a hydrophobic amino acid R group

d. negatively charged amino acid R group to a hydrophobic amino acid R group.

Imagine that Rebecca was diagnosed with severe gallstones and had a cholecystectomy. After the removal of her gallbladder, Rebecca's doctor advised her to limit her dietary intake of certain types of food. Which type of food did the doctor likely suggest that she limit? a. poultry b. vegetables c. bread d. oil

d. oil

What is the digestive function of the liver? a. production of proteases b. storage of bile c. filtration of blood d. production of bile

d. production of bile

Trypsin inhibitor is a pancreatic polypeptide that binds trypsin with very high affinity. Trypsin inhibitor deficiency can cause pancreatitis (inflammation of the pancreas). In normal digestion, trypsin activates several zymogens or proenzymes in which organ? a. stomach b. mouth c. pancreas d. small intestine What are the effects of trypsin inhibitor? a. Trypsin inhibitor prevents zymogen activation in the pancreatic ducts. b. Trypsin inhibitor blocks trypsinogen's catalytic activity. c. Trypsin inhibitor blocks the proteolytic activity of trypsin. d. Trypsin inhibitor blocks zymogen activation at very low pH levels.

d. small intestine a. Trypsin inhibitor prevents zymogen activation in the pancreatic ducts. c. Trypsin inhibitor blocks the proteolytic activity of trypsin.

The formation of pyranose and furanose forms of sugar generates a new asymmetric carbon, giving rise to α- and β‑forms. If the resulting anomeric alcohol group is above the plane of the sugar, the structure is known as a. the epimeric stereoisomer b. the alpha-anomer c. the D-anomer d. the beta-anomer e. the L-enantiomer

d. the beta-anomer

In passive transport, the energy driving the movement of materials across a membrane is provided by a. nothing because there is no energy requirement for passive transport. b. ATP c. the membrane transporter d. the concentration gradient across the membrane

d. the concentration gradient across the membrane.

Enzymes that are activated by specific proteolytic cleavage are called a. allosteric b. isozymes c. heterozymes d. zymogens

d. zymogens

Calculate the distance olive oil (a lipid) could move in a membrane in 15 seconds15 seconds assuming the diffusion coefficient is 1 𝜇m2/s1 μ⁢m2/s . Use the equation S=(4Dt)1/2S=(4Dt)1/2 where S is distance traveled, 𝑡t is time, and D is the diffusion coefficient.

distannce = 7.745966

Receptor tyrosine kinases (RTKs)

domains that have extracellular and intracellular domains. When the ligand binds to the extracellular domain, the receptor dimerizes (intracellular domains move together) and undergo cross-phosphorylation and activation (phosphorylate each other)

Why does calmodulin bound with calcium interact with target proteins, whereas free calmodulin does not? a. Calcium binding to regulatory subunits results in the release of the active catalytic subunits. b. Calcium ions serve to bridge negatively charged groups on calmodulin and the target protein. c. Calcium binding results in a conformational change in calmodulin, producing a structure that can be activated by protein kinase A‑dependent phosphorylation. d. Calcium ion binding neutralizes negative charges on calmodulin such that electrostatic repulsion between it and negative charges on the target protein do not occur. e. Calcium binding results in a conformational change in calmodulin, producing a structure that can bind to target proteins.

e. Calcium binding results in a conformational change in calmodulin, producing a structure that can bind to target proteins.

During catabolic processes, the oxidation of energy‑rich molecules often results in the reduction of NAD+ to NADH. What comparable molecule is the most commonly used reductant for reductive steps in anabolic processes? a. FMNH2 b. coenzyme A c. ATP d. FAD e. NADPH

e. NADPH

After a period of time, Gα ceases to stimulate adenylate cyclase. What is the consequence of Gα ceasing to stimulate adenylate cyclase? a. Adenylate cyclase converts Gα GTP to cGMP, allowing Gα to diffuse back to Gβγ. b. Gα is phosphorylated, enabling it to return to Gβγ. c. Gβγ binds to Gα, promoting its GTPase activity. d. GDP binds to the G protein. e. The G protein's GTPase activity removes a phosphate, allowing Gα to diffuse back to Gβγ.

e. The G protein's GTPase activity removes a phosphate, allowing Gα to diffuse back to Gβγ.

lipases

enzymes secreted by the pancreas that degrade triacylglycerols into free fatty acids and monoacylglycerol.

Proteolytic enzymes (proteases)

enzymes secreted by the stomach and pancreas that degrade proteins into amino acids.

glycoproteins

formed when a carbohydrate group can is covalently attached to a protein

Lipids are broken down by bile and digestive enzymes before absorption into the body. Where does absorption take place? a. stomach b. colon c. mouth d. esophagus e. gallbladder f. large intestine g. small intestine

g. small intestine

Glycogen

the most common homopolymer in animal cells. The storage form of glucose.

Oligosaccharide residues on cell surfaces provide recognition sites for a variety of functions, including cell-cell adhesion, movement of immune cells through capillary walls, viral attachment and infection of cells, and targeting of red blood cells and serum proteins for destruction. ________ are the proteins involved in recognition of specific oligosaccharide structures.

lectins

Oligosaccharide

linkages of two or more monosaccharides by O-glycosidic bonds. Includes disaccharides like maltose (two D-glucose residues are joined by a glycosidic linkage between the alpha-anomeric form of C-1 on one sugar and the hydroxyl oxygen atom on the C-4 of the adjacent sugar.

liposome

lipid vesicles. Aqueous compartments enclosed by a lipid bilayer that form by suspending a membrane lipid in an aqueous medium and then sonicating (agitating by high-frequency sound waves) to give a dispersion of closed vesicles that are quite uniform in size.

Suppose that each β-adrenergic receptor bound to epinephrine converts 100 molecules of the Gα subunit to the GTP-bound form, Gαs. If each molecule of activated adenylate cyclase produces 1000 molecules of cAMP per second, how many molecules of cAMP are produced in 10 seconds after the formation of a single complex between epinephrine and the β-adrenergic receptor? Assume the pathway is fully responsive.

molecules of cAMP = 10 x 10^5

enantiomer

molecules that are mirror images of each other

Amphipathic molecules

molecules that contain both a hydrophilic and hydrophobic moiety. Characteristic of membrane lipids!

Assume that the complete combustion of one mole of glucose, a monosaccharide, to carbon dioxide and water liberates 2870 kJ of energy (Δ𝐺°′=−2870 kJ/mol. If the energy generated by the combustion of glucose is entirely converted to the synthesis of a hypothetical compound X, calculate the number of moles of the compound that could theoretically be generated. Use the value Δ⁢G°′compound X=−34.1 kJ/mol. Round your answer to two significant figures.

moles = 84

carbamate

negatively charged groups formed when carbon dioxide stabilizes deoxyhemoglobin by reacting with the terminal amino groups

glycosyltransferases

oligosaccharides are synthesized through the action of specific enzymes, which catalyze the formation of glycosidic bonds

Vitamins

organic molecules needed in small amounts in the diets of many higher animals. Some act as coenzymes. In all cases, it must be modified before it can serve its function.

ion channel

other membrane proteins that facilitate passive transport. They facilitate ion-transport. The closer they can transport ions to the actual rate of diffusion through aqueous solution, the more effective the channel is. These channels are highly sophisticated and respond to chemical and physical changes in the environment by undergoing conformational changes to regulate when ions flow in and out of the cell. They can be voltage-gated and open in response to changes in membrane potential, or ligand-gated and open in response to the binding of a small ligand (like a neurotransmitter)

phosphoglycerides

phospholipids derived from glycerol, composed of a glycerol backbone to which are attached two fatty acid chains and a phosphorylated alcohol.

Integral membrane proteins

proteins that are embedded in the hydrocarbon chains of membrane lipids and are released only when the membrane is physically disrupted. Most span the entire lipid bilayer.

Catabolism

reactions that transform fuel into cellular energy

Antiporters

secondary transporters that couple the downhill flow of one species to the uphill flow of another in the opposite direction across the membrane. Transports two substrates in opposite directions.

Symporters

secondary transporters that use the flow of one species to drive the flow of a different species in the same direction across the membrane. Transports two substrates in the same direction.

second messengers

small molecules that are used to relay information form the receptor-ligand complex. They amplify signals. cAMP, IP3, Ca2+, DAG are the most common

Glycolipids

sugar-containing lipids. Ubiquitous in all cell membranes, where they play a role in cell-cell interactions. In animal cells, they are derived from sphingosine. The amino group of the sphingosine backbone is acylated by a fatty acid

epimers

sugars that are diastereomers differing in configuration at only a single asymmetric center

Reducing sugar

sugars that react with solutions of cupric ion

αβ dimers

the 3D structure of hemoglobin is best described as a pair of dimers that associate to form the hemoglobin tetramer.

trypsin

the activated form of the enzyme, formed when trypsinogen is cleaved. It activates the remaining pancreatic zymogens.

Digestion

the biochemical set of reactions by which food is converted into molecules that will be further manipulated to yield biologically useful energy and biosynthetic building blocks

adenosine triphosphate (ATP)

the common energy currency. A nucleotide consisting of adenine, a ribose, and a triphosphate unit. Energy rich due to the phosphoanydride

adenylate cyclase

the enzyme activated by the B-adrenergic signaling pathway. A membrane protein containing 12 membrane spanning helices. It increases caMP production, therefore amplifying the signal of the ligand binding. The net result is that the binding of epinephrine to the receptor on the cell surface increases the rate of cAMP production inside the cell.

zymogens (proenzymes)

the inactive form of a digestive enzyme. They are activated by proteolytic cleavage. Before secretion, thet exist in granules near the cell membrane and fuse with the cell membrane in response to cell signals

Cellulose

the major structural polysaccharide of glucose. Serves a structural rather than nutritional role. Very abundant organic compound in the biosphere.

proteoglycans

the second class of glycoproteins. A compound consisting of a protein bonded to glycosaminoglycan groups, present especially in connective tissue. Carbohydrates make up a larger percentage of the weight. Can function as structural components and lubricants.

cerebrosine

the simplest glycolipid. It contains a single sugar residue (either glucose or galactose)

pepsin

the stomach enzyme. secreted as a zymogen called pepsinogen. Active pepsin activates the remaining pepsinogen.

Seven-transmembrane-helix (7TM) receptors

transmit information initiated by signals (photons, odorants, tastants, hormones, and neurotransmitters). Spans the membrane 7 times, the binding of a ligand on the outside of the cell induces a conformational change in the 7TM receptor that can be detected inside the cell.

disaccharide

two sugars joined by an O-glycosidic bond. 3 most common ones are sucrose (a glucose unit joined to a fructose unit, cleaved by sucrase), lactose (galactose joined to glucose, hydrolyzed by lactase), maltose (glucoses linked, hydrolyzed by maltase)

proto-oncogenes

unmutated, routinely expressed versions of genes that normally regulate cell growth. Causes cancer when mutated.

Suppose a sprinter's muscle tissue contains creatine phosphate at a concentration of 100 mM100 mM after dietary supplementation. The sprinter's muscle tissue also contains 4 mM ATP, 0.013 mM ADP, and 13 mM creatine. Use the table of the standard free energies of hydrolysis of phosphorylated compounds and the given concentrations to calculate the free energy change, Δ𝐺, of the creatine kinase reaction in this sprinter at 25 °C.

∆G = -3.487 kJ•mol-1

Synthesis of the activated form of acetate (acetyl‑CoA) is carried out in an ATP‑dependent process. Acetate+CoA+ATP⟶Acetyl−CoA+AMP+PPi The Δ⁢G′∘ for the hydrolysis of acetyl‑CoA to acetate and CoA is −32.2 kJ/mol, and that for hydrolysis of ATP to AMP and PPi is −30.5 kJ/mol. Calculate Δ⁢G′∘ for the ATP‑dependent synthesis of acetyl‑CoA shown in the equation. Almost all cells contain the enzyme inorganic pyrophosphatase, which catalyzes the hydrolysis of PPi to Pi. What effect does the presence of this enzyme have on the synthesis of acetyl‑CoA? a. Hydrolysis of pyrophosphate decreases the rate of the reaction. b. Hydrolysis of pyrophosphate has no effect on the reaction. c. Hydrolysis of pyrophosphate shifts the equilibrium of the reaction to the left, making the formation of acetyl‑CoA energetically less favorable. d. Hydrolysis of pyrophosphate shifts the equilibrium of the reaction to the right, making the formation of acetyl‑CoA energetically more favorable. e. Hydrolysis of pyrophosphate increases the rate of the reaction.

∆G'∘ = 1.7 kJ/mol d. Hydrolysis of pyrophosphate shifts the equilibrium of the reaction to the right, making the formation of acetyl‑CoA energetically more favorable.