11,12,14,15
*Polar head groups of phospholipids are esterified to what functional group?* A) methyl B) phosphate C) ketone D) thiol E) aldehyde
B) phosphate Section: 11.2
*Acetyl CoA is eventually oxidized to carbon dioxide during which cycle?* A) phase 3 B) the citric acid cycle C) glycolysis D) oxidative phosphorylation E) None of the above.
B) the citric acid cycle Section: Intro
*The fluorescence recovery after photobleaching (FRAP) technique has been used to study:* A) membrane composition. B) the lateral diffusion in membranes. C) protein structural motifs in membranes. D) All of the above. E) None of the above.
B) the lateral diffusion in membranes. Section: 12.4
*The longer the fatty acid, the ____________ the fatty acid.* A) more oxidized B) lower the melting point of C) higher the melting point of D) more reduced E) more double-bond containing
C) higher the melting point of Section: 11.1
*The low incidence of protein or lipid flip-flop in a membrane preserves:* A) membrane fluidity. B) membrane melting temperatures. C) membrane asymmetry. D) All of the above. E) None of the above.
C) membrane asymmetry. Section: 12.4
*The energy for __________ transport comes from the gradient itself.* A) active B) facilitated C) passive D) pumped E) A TP-mediated
C) passive Section: 12.5
*Which phospholipid is enriched in neural sheath membranes?* A) phosphatidic acid B) phosphatidylcholine C) sphingomyelin D) diphophatidylglycerol (cardiolipin) E) phosphatidylinositol
C) sphingomyelin Section: 11.3
*Which of the following is NOT a main function of lipids?* A) cell signaling B) fuel source C) structural rigidity of the cytoskeleton D) membrane component E) All of the above.
C) structural rigidity of the cytoskeleton Section: Introduction
*What is the standard-state free energy (ΔG°′) for the hydrolysis of ATP to ADP?* A) +45.6 kJ/mol B) −45.6 kJ/mol C) −30.5 kJ/mol D) −14.6 kJ/mol E) +30.5 kJ/mol
C) −30.5 kJ/mol Section: 15.2
In aerobic metabolism, the product of oxidation of carbon containing fuels is/are ____________.
CO2 Section: 15.3
_______________ is the type of metabolism where useful energy is harvested.
Catabolism Section: Introduction
What is multidrug resistance?
Cells may develop a resistance to drugs that were initially quite toxic to them. When this occurs, they also develop resistance to a range of other compounds. Section: 12.5
________________ is a membrane lipid composed of sphingosine, fatty acid, and a simple sugar.
Cerebroside Section: 11.3
___________________ is a sugar-containing lipid which contains a single carbohydrate moiety.
Cerebroside Section: 11.3
____________ are organisms that obtain chemical energy from the oxidation of food stuff.
Chemotrophs Section: Introduction
_______________ inserts into lipid bilayers, disrupting interactions between fatty acids, thereby helping to maintain membrane fluidity.
Cholesterol Section: 12.2
Steroid hormones come from what lipid?
Cholesterol is the main source of steroid hormones. Section: 11.3
___________: This compound serves as an acyl carrier in metabolism.
Coenzyme A Section: 15.4
How are metabolic processes unified? How can you use this to help learn and understand biochemistry?
Common molecules and mechanisms are evident in motifs and patterns throughout metabolic pathways. Understanding the logic of catabolic and anabolic paths, and knowing common molecules (such as ATP) and mechanisms (oxidation reduction) make it simpler to understand the myriad paths of metabolism. Section: 15.4
*Which of the following enzymes activates trypsin?* A) zymogenase B) pepsin C) trypsinase D) enteropeptidase E) carboxypeptidase
D) enteropeptidase Section: 14.2
*The degree of membrane fluidity depends on:* A) the percentage of lipids that contain choline. B) the percentage of glycolipids. C) the percentage of free fatty acids. D) the percentage of unsaturated fatty acids. E) None of the above.
D) the percentage of unsaturated fatty acids. Section: 12.2
____________ is the first stage in the oxidation of foods.
Digestion Section: Introduction
Based on your knowledge of lipids, explain why some fats from plants are oils (liquid at room temperature) and animal fats are solid at room temperature.
Knowing that the longer the fatty acid chain, the higher the melting point, and that more double bonds leads to lower melting points, plant fats are likely to be shorter and be primarily unsaturated or monounsaturated, while animal fats are more often polyunsaturated. Section: 11.2
Describe a lipid raft and its potential role in a cell.
Lipid rafts are cholesterol-rich regions of the membrane that create a less fluid environment. These rafts are likely involved in cell-signaling events. Section: 12.2
What are liposomes? What are some of their current commercial applications?
Liposomes are spherical structures of lipid bilayers, similar to miniature organelles. They are extremely useful as models of cell systems. They can be used to contain or transport molecules such as drugs for therapy, and are commonly used in cosmetics such as skin creams. Section: 12.1
____________ activation is a mechanism of permanently activating a protease by covalent modification.
Zymogen Section: 14.2
____________: A term applied to molecules that have both hydrophilic and hydrophobic moieties.
amphipathic Section: 11.2
Membranes are said to be ____________ because their two faces always differ from each other.
asymmetric Section: Intro
____________: The process by which lipids and proteins move in the membrane bilayer.
lateral diffusion Section: 12.2
Snake venom contains ____________, which cause hydrolysis of red blood cells.
lipases Section: 14.4
The ____________ enzymes are responsible for the hydrolysis of acyl chains from the glycerol backbone.
lipases Section: 14.4
____________: A complex between cholesterol and membrane phospholipids.
lipid raft Section: 12.2
_______________ are bilayer lipid vesicles with an aqueous compartment.
liposomes Section: 12.1
The reduction in tight packing due to cis double bonds ________________ the melting temperature of a fatty acid.
lowers Section: 11.1
Dietary fat is primarily transported from the gut to the ______________.
lymphatic system Section: 14.4
Most cell membranes are electrically polarized, the inside being _______________ relative to the outside.
negative Section: Intro
The electron carrier, NADH, is derived from the ____________ vitamin.
niacin Section: 15.4
α amylase begins the digestion of ____________ in the gut.
carbohydrates Section: 14.3
Fatty acids are ionized at physiological pH and so are referred to in their ______________ form.
carboxylate Section: 11.1
In addition to phospholipids and glycolipids, ____________ is a major type of membrane lipid.
cholesterol Section: 11.3
____________ is a flat polycylic molecule that is absent in prokaryotic membranes.
cholesterol Section: 11.3
Bile salts are produced from a ______________ precursor?
cholesterol Section: 14.4
Micelles are important for lipid absorption across the plasma membrane, but lipids are assembled into ______________ for transport through the lymph system.
chylomicrons Section: 14.4
Inactive chymotrypsinogen will be hydrolyzed to become an active enzyme called ______________.
chymotrypsin Section: 14.2
The configuration of most fatty acids is ________________.
cis Section: 11.1
A lipid is defined as a compound soluble in ________________.
organic solvent Section: Introduction
The shorthand notation indicating that there are two cis double bonds between carbons 9 and 10 and again between 12 and 13 is ________________.
cis, cis ∆9, 12 Section: 11.1
Lipid biolayers spontaneously form ____________.
closed biomolecular sheets Section: Introduction
A thermodynamically unfavorable reaction can be driven by a thermodynamically favorable reaction to which it is _________________.
coupled Section: 15.1
In vertebrate muscle, _________________ serves as a reservoir of high-potential phosphoryl groups that can be readily transferred to ADP to regenerate ATP.
creatine phosphate Section: 15.2
The three stages of catabolism result in a ______________ chemical transformation of the food.
oxidation Section: Introduction
The common name of hexadecanoic acid is ________________.
palmitic acid Section: 11.1
The _______________ of small molecules is correlated with their relative solubilities in water and nonpolar solvents.
permeability Section: 12.1
ATP is considered an "energy rich" compound because it contains two ______________ bonds.
phosphoanhydride Section: 15.2
Snake venom has a high concentration of ______________ that digest(s) the cell membrane.
phospholipases Section: 14.4
____________: A type of lipid with two acyl chains, a glycerol backbone, and a polar head group.
phospholipid Section: 11.3
FAD is an electron carrier that is derived from the vitamin _________________.
riboflavin Section: 15.4
A(n) ______________ is an inactive enzyme that must be partially digested to attain full enzymatic activity.
zymogen Section: 14.2
Amylase digests carbohydrates by cleaving the ______________ bonds of starch.
α-1,4 glycosidic bonds Section: 14.3
The limit dextrin is material not digested by amylase due to the ______________.
α-1,6 glycosidic bonds Section: 14.3
One important ________________ is EPA (eicosapentaenoic acid), which is found in shellfish.
ω-3 fatty acid Section: 11.1
The rate of lateral diffusion is such that a phospholipid molecule can travel from one end of a bacterium to the other in _______________ of time.
1 second Section: 12.4
What are the two criteria that must be satisfied by a biochemical pathway?
1) The reactions must be specific, in that only one set of products is formed from a specific set of reagents. 2) As a whole, the pathway must be spontaneous; that is, it must be thermodynamically favored. Section: 15.1
In the cell, the hydrolysis of an ATP molecule in a coupled reaction changes the equilibrium ratio of products to reactants by a factor of _________________.
108 Section: 15.2
The number of carbons in most common fatty acid is ____________.
16 or 18 Section: 11.1
How are dietary proteins, carbohydrates, and lipids digested?
3 steps: 1st food is absorbed 2nd broken down into smaller, usable monomer components 3rd converted to intermediate forms for transport to their final metabolic site. Sections: Introduction, 14.1, 14.5
What is a chylomicron?
A complex mixture of lipid and protein formed in the lumin of the gut to transport nascent lipids through the lymph system. Section: 14.4
Describe the effect of introducing a sodium ion pore into a membrane containing the Na+- glucose symporter.
A high extracellular concentration of sodium is used to drive the symport transport of glucose against it's gradient. Intracellular sodium is pumped against its gradient by active transport. An Na+ pore will cause the pumped Na+ ions to cross back into the membrane without the transport of glucose. A secondary and devastating effect would be the loss of ATP as the Na+-K+ ATP transporter would continue to work using ATP. Section: 12.5
How much ATP is used daily by a typical human? How is it regenerated?
A human uses 40 kg of ATP per day. There are only about 100 g ATP available; thus the ATP is used and regenerated rapidly. ATP is regenerated from ADP and Pi, using the energy from catabolic processes. Section: 15.3
What is the difference between a sphingolipid and a glycerolipid?
A sphingolipid has an alcohol such as a serine for the backbone and only one fatty acid tail, while a glycerolipid uses glycerol as the backbone and has two acyl chains esterified to the hydroxyl groups of the glycerol. Section: 11.3
*How many molecules thick are membranes?* A) 2 B) 1 C) infinite D) they are of varying thickness, depending on their structure E) None of the above.
A) 2 Section: Intro
*The notation 12:2 indicates which of the following about a fatty acid?* A) There are 12 carbons in the chain with 2 double bonds. B) There are two 12-carbon chains for this fatty acid. C) The second carbon has a fatty acid double bond. D) The double bond on the 12th carbon has a double bond. E) There are 2 trans double bonds on this 12-carbon fatty acid.
A) There are 12 carbons in the chain with 2 double bonds. Section: 11.1
*Snake venom's poison is actually:* A) a collection of digestive enzymes. B) respiratory toxins. C) paralysis toxins and red-blood-cell poisons. D) All of the above. E) None of the above.
A) a collection of digestive enzymes. Section: 14.4
*The metabolic pathways that require energy and are often biosynthetic processes are:* A) anabolic. B) catabolic C) ametabolic. D) All of the above.
A) anabolic. Section: 15.1
*Which energy source is used to regenerate ATP from ADP and Pi?* A) oxidation of carbon to CO2 B) electrochemical potential of stored glycogen C) reduction of pyruvate to lactate D) All of the above. E) None of the above.
A) oxidation of carbon to CO2 Section: 15.2
*All of the following are pancreatic proteases except:* A) pepsin B) chymotrypsin C) trypsin D) carboxypeptidases E) elastase
A) pepsin Section: 14.2
*A digestible proton-pump inhibitor would likely have the following effect:* A) protein not being digested B) nucleic acid hydrolysis C) loss of ATP production D) pepsin activation E) decreasing levels of bile salts
A) protein not being digested Section: 14.1
*Digitalis is a cardiotonic steroid that does not act like a steroid. Instead, its function is to inhibit:* A) the Na+-K+ pump. B) fatty acid intake. C) calcium channels. D) potassium and sodium pores. E) dropsy channel.
A) the Na+-K+ pump. Section: 12.5
*Digestion is:* A) the process of breaking down large molecules in food. B) the salvage of metabolic intermediates. C) creating energy from foodstuff . D) the set of reactions that degrades small molecules into a few simple units. E) a pathway activated by steroid hormones
A) the process of breaking down large molecules in food Section: Introduction
*The most common motif found in membrane-spanning proteins is:* A) α helices of nonpolar amino acids that pass through the membrane. B) α helices of charged amino acids that form channels via extensive hydrogen bonding. C) a triple helix of α helices. D) a helix-turn-helix arrangement of the peptide strands. E) None of the above.
A) α helices of nonpolar amino acids that pass through the membrane. Section: 12.3
The ____________ is the "chemical currency" of metabolism.
ATP Section: 15.2
____________ is the mechanism by which the stomach maintains a pH of around 1-2 pH units.
ATP-dependent proton pump Section: 14.1
What is an activated carrier? Provide two examples.
Activated carriers are molecules that are used as the carrier molecules of a particular molecule, atom, electron, or of protons. One example would be ATP, which is the activated carrier of phosphoryl groups. Flavin derivatives (FAD) and nicotinamide derivatives (NAD+) are examples of activated carriers of electrons. Sections: 15.2 and 15.4
How is metabolism controlled?
Amounts of enzymes Enzymes catalytic activity Substrate accessibility Section: 15.5
____________ pathways can be either anabolic or catabolic, depending on the energy conditions of the cell.
Amphibolic Section: 15.1
_________________ is the process of building larger molecules from smaller ones.
Anabolism Section: Introduction
*Which of the following is the electron donor used for reductive biosynthesis?* A) NADH B) NADPH C) FADH2 D) CoA-SH E) ATP
B) NADPH Section: 15.4
*The reaction pathways that transform fuels into cellular energy are:* A) anabolic. B) catabolic. C) ametabolic. D) All of the above. E) None of the above.
B) catabolic. Section: 15.1
*Which of the following helps regulate membrane fluidity in animals?* A) protein B) cholesterol C) ATP D) magnesium ion E) None of the above.
B) cholesterol Section: 12.2
*Unsaturations ____________ melting points of fatty acids and their derivatives.* A) maintain B) decrease C) increase D) are unrelated to E) None of the above.
B) decrease Section: 11.2
*The result of lipase activity in digestion is:* A) phospholipid head group hydrolysis. B) monoacylgycerol and two free fatty acids. C) bile-salt formation. D) hydrolysis of membrane proteins. E) emulsion formation.
B) monoacylgycerol and two free fatty acids. Section: 14.4
*Which is the proper order of permeability of molecules across a membrane, from the most permeable to the least?* A) water, glucose, urea, sodium ion B) water, indole, glucose, sodium ion C) water, indole, sodium ion, glucose D) indole, glucose, urea, sodium ion E) indole, water, glucose, sodium ion
B) water, indole, glucose, sodium ion Section: 12.1
Draw a cross-section of a membrane bilayer and a liposome.
Bilayers have two lipid layers in which the heads are on the outside and the tails are arranged on the inside in two rows. Liposomes are small aqueous compartments surrounded by a lipid bilayer. Figures 12.1 and 12.2 in the textbook provide examples of this. Section: 12.1
How are lipid bilayers formed? What is the driving force?
Bimolecular sheets of lipids form spontaneously by self-assembly. Hydrophobic interactions are the driving force. Van der Waals attractive forces between the hydrocarbon tails favor the close packing of the tails. The polar heads are attracted to each other by electrostatic and hydrogen-bonding attractions. Section: 12.1
Compare ATP to acetyl CoA.
Both are activated carriers and are common to several pathways. Acetyl CoA carries acetyl groups with high acetyl-transfer potential. ATP carries phosphate groups with high phosphoryl-transfer potential.
Why might a protein be covalently attached to a lipid?
By attaching to a lipid, the protein is able to associate with a hydrophobic environment such as a membrane. In these attachments, the lipid part is inserted into the hydrophobic interior of the membrane and anchors the protein to the membrane surface. Section: 11.4
*Palmitate has how many carbons in its chain?* A) 12 B) 14 C) 16 D) 20 E) 24
C) 16 Section: 11.1
*The polar head group of phospholipids is found at which carbon of glycerol?* A) C1 B) C2 C) C3 D) C1 and C2 E) C2 and C3
C) C3 Section: 11.2
*The pancreas releases ___________ to buffer the pH of the stomach juices.* A) a strong base to counter the strong acid B) HCl C) NaHCO3 D) pepsin E) ATPase-activating protein
C) NaHCO3 Section: 14.1
*The third state of digestion involves:* A) sugars. B) fatty acids. C) acetyl CoA. D) All of the above. E) None of the above.
C) acetyl CoA. Section: Intro
*Carbohydrate residues attached to the membrane lipids are:* A) always positioned on the intracellular side of the membrane. B) always positioned on the inside center of the bilayer. C) always positioned on the extracellular side of the membrane. D) always positioned equally on both sides of the membrane. E) also covalently attached to membrane proteins.
C) always positioned on the extracellular side of the membrane. Section: 12.1
*Complex carbohydrates are absorbed:* A) as acetyl CoA. B) as starch or glycogen. C) as they are converted to glucose and simple sugars. D) as short four glucose residue s. E) after the digestion of α 1,6 bonds by α amylase.
C) as they are converted to glucose and simple sugars. Section: 14.3
*Which of the following is released by the upper intestine and increases zymogen secretion?* A) secritin B) pepsin C) cholecystekinin D) bile salts E) enteropeptidase
C) cholecystekinin Section: 14.5
*Which is the correct coenzyme-carrier pair?* A) NADH: acyl B) tetrahydrofolate: electrons C) coenzyme A: acyl D) lipoamide: aldehyde E) thiamine pyrophosphate: glucose
C) coenzyme A: acyl Section: 15.4
*The second step for an organism to utilize food is to:* A) activate A TP for digestion. B) hydrolyze the complicated macromolecules for transport. C) degrade numerous small units to a few simple units. D) phagocytose the food into the cell. E) None of the above.
C) degrade numerous small units to a few simple units. Section: Intro
*Eating ____________ increases the ω-3 fatty acids, decreasing ____________.* A) arachidonic acid, heart attacks B) a low-fat diet, heart attacks C) fatty fish, heart attacks D) shellfish, lung cancer E) vegetable oils, blood pressure
C) fatty fish, heart attacks Section: 11.1
*Octadecatrienoic acid has how many double bonds?* A) 0 B) 1 C) 2 D) 3 E) 4
D) 3 Section: 11.1
*Membranes lipids are primarily comprised of:* A) phospholipids B) glycolipids C) cholesterol D) A and B E) A, B, and C
D) A and B Section: 11.3
*The electron carrier(s) that include(s) ATP is/are:* A) NAD+ B) FAD C) FMN D) A and B E) A, B, and C
D) A and B Section: 15.2
*Pantothenate kinase associated degeneration:* A) is a predominantly neurological disorder. B) can cause anemia. C) effects tissues that are dependent on aerobic metabolism. D) A and C. E) A, B, and C.
D) A and C. Section: 15.4
*Which of the following is true?* A) Membranes are lipid bilayers. B) Membrane lipids have both hydrophobic and hydrophilic properties. C) Many membranes are electrically polarized. D) All of the above. E) None of the above.
D) All of the above Section: Intro
*Pepsin requires ____________ to become active.* A) low pH B) partial denaturation of protein C) zymogen activation D) All of the above. E) None of the above.
D) All of the above. Section: 14.2
*The reduced form of flavin adenine dinucleotide is:* A) FADH B) FAD C) FADH++ D) FADH2 E) None of the above
D) FADH2 Section: 15.4
*Which of the following statements is consistent with the structure of biological membranes?* A) All membrane proteins are integral and associate with the hydrophobic region of the membrane. B) Both proteins and lipids readily undergo transverse ("flip-flop") diffusion from the inside to the outside of the membrane. C) Membranes are symmetric. D) The membrane lipids self-assemble to form the lipid bilayer. E) A biological membrane consists of proteins sandwiched between two layers of lipids, which is referred to as a lipid bilayer.
D) The membrane lipids self-assemble to form the lipid bilayer. Section: 12.1
*Which of the following membranes would be the most fluid?* A) a bilayer made of lipids with polyunsaturated 18-carbon fatty acids B) a bilayer made of lipids with saturated 18-carbon fatty acids C) a bilayer made of lipids with saturated 16-carbon fatty acids D) a bilayer made of lipids with polyunsaturated 16-carbon fatty acids E) All of the above are equivalent in fluidity.
D) a bilayer made of lipids with polyunsaturated 16-carbon fatty acids Section: 12.2
*The transport of lipids in the lymph is carried out by:* A) lipases. B) micelles. C) cholesterol bile-salt binding. D) chylomicrons. E) None of the above.
D) chylomicrons. Section: 14.4
*What force(s) stabilize(s) the lipid bilayers?* A) van der Waals interactions B) electrostatic and hydrogen bonding between the polar heads and surrounding water C) covalent bonds between the lipid tails D) covalent bonds between the lipids and membrane proteins E) A and B
E) A and B Section: 12.1
*Which of the following molecules has a higher phosphoryl-transfer potential than ATP?* A) phosphoenolpyruvate B) creatine phosphate C) 1,3-bisphosphoglycerate D) A and B E) A, B, and C
E) A, B, and C Section: 15.2
*Metabolic processes are regulated by:* A) transcriptional regulation of the amount of enzyme. B) allosteric control of enzyme activity. C) the accessibility of substrates by compartmentalization. D) A and B. E) A,B, and C.
E) A, B, and C Section: 15.4
*Which activated carrier(s) contain(s) adenosine phosphate units?* A) NADH B) FADH2 C) coenzyme A D) A and B E) A, B, and C
E) A, B, and C Section: 15.4
*What are the major purpose(s) for which organisms require energy?* A) the performance of mechanical work B) active transport C) the synthesis of biomolecules D) A and C E) A, B, and C
E) A, B, and C Section: Intro
*Some of the mechanisms by which enzyme catalytic activity is controlled are:* A) allosteric control. B) feedback inhibition. C) covalent modification. D) A and C. E) A,B,andC. Ans: E Section: 15.4
E) A,B, and C. Section: 15.4
*A phosphatidate lipid (phosphatidic acid) has which of the following components?* A) phosphate B) glycerol C) ester linkage D) acyl chain E) All of the above.
E) All of the above. Section: 11.1
An ω-3 fatty acid: A) has a methyl group at the carboxyl end of the fatty acid. B) has a methyl group on the third carbon of the chain. C) has a double bond on the third carbon in from the carboxyl group. D) has a triple bond on the third carbon from the methyl end of the fatty acid. E) None of the above.
E) None of the above Section: 11.1
*An antiporter and a symporter are examples of:* A) passive diffusion. B) primary active transporters. C) entropy-driven pores. D) an ABC transporter. E) a secondary transporter.
E) a secondary transporter. Section: 12.5
*The backbone of a phospholipid is which of the following?* A) glucose B) cholesterol C) fatty acid chain D) triacylglycerol E) glycerol
E) glycerol Section: 11.2
*Glucose transport takes place by:* A) active transport using the sodium gradient. B) active transport using ATP as the energy source. C) passive transport using the glucose gradient. D) secondary active transport using the potassium gradient. E) secondary active transport using the sodium glucose cotransporter.
E) secondary active transport using the sodium glucose cotransporter. Section: 14.3
What are some molecules that form the polar head group of phospholipids? Provide several examples.
Examples of head groups include serine, ethanolamine, choline, glycerol, and inositol. Section: 11.2
What does the notation 18:2 for fatty acids imply?
In this fatty acid, there are 18 carbons, with 2 double bonds. Section: 11.1
How do proteins function to make membranes selectively permeable?
Many of the proteins found in a membrane are transporters, each with a specific mechanism to select for a single class or kind of molecule to allow through the cell. Section: 12.5
What is a limit dextrin?
Material not digested by amylase due to the α 1,6 bonds Section: 14.3
____________ are lipid vesicles that act to transport fats across the intestinal epithelium.
Micelle Section: 14.4
The electron donor in most reductive biosyntheses is ____________.
NADPH Section: 15.4
In aerobic organisms, the ultimate acceptor of electrons is/are ____________.
O2 Section: 15.3
____________is a protease released by the stomach for the digestion of protein.
Pepsin Section: 14.2
_______________ membrane proteins are bound primarily by electrostatic and hydrogen-bond interactions with the head groups of lipids.
Peripheral Section: 12.3
___________ are organisms that use energy from sunlight and convert it to chemical energy.
Phototrophs Section: Introduction
What is the function of prostaglandin H2 synthase-1? How does its position in the membrane facilitate its activity?
Prostaglandin H2 synthase-1 converts arachidonic acid into prostaglandin H2. The protein is embedded in the membrane, with a hydrophobic channel submerged about halfway through the bilayer. The arachidonic acid is a product of membrane lipid hydrolysis, and enters the protein channel from within the membrane, successfully avoiding any interaction with aqueous environments. Section: 12.3
What general factors contribute to the high phosphoryl-transfer potential of ATP?
Resonance stabilization, electrostatic repulsion, and stabilization due to hydration are important. Section: 15.2
List five activated carriers in metabolism, and give the vitamins that are the precursors of these carriers. *Activated carrier* NADH and NADPH FADH2 acetyl-coenzyme A biotin tetrahydrofolate *Vitamin* niacin riboflavin pantothenate biotin folic acid
Section: 15.4 and Table 15.2
Define the different chemical characteristics for these phospholipids: phosphatidylserine, phosphatidylcholine, and phosphatidylinositol.
See Figure for each phospholipid and focus on the head group. Look for charge and hydrophobicity. Section: 11.3
Nonfat substitutes often come with a warning of runny or watery stool. What metabolic condition is similar?
Steatorrhea, runny stool due to excess lipids when the bile salts necessary for emulsification and transport of lipids are inadequate. Section: 14.4
How is the release of pancreatic enzymes coordinated with digestion in the stomach ?
Stretching of the upper intestine leads to the endocrine cells releasing the hormone cholecystokinin (CCK). CCK acts on the pancreas, causing it to release a host of digestive enzymes. Section: 14.2
What is the role of cholesterol in digestion?
The emulsification of lipids is required for digestion and transport of fats. Crucial to this process are the bile salts, formed from cholesterol. Section: 14.4
Flip-flopping of lipids take place once in several hours. This is evidence for what?
That the transverse diffusion of lipids is allowed but the slow pace is evidence that the membranes are able to achieve and hold asymmetry for a long period of time. Section: 12.3
What are the key biochemical elements for transmembrane-spanning proteins?
The amino acids that cross the membrane are typically in a helical conformation and are hydrophobic. There are some proteins, typically pores, which have β pleated sheets that form the membrane spanning core of the pore. The extracellular portion of these pores are typically glycosylated and are in random order. Section: 12.3
Draw the resonance structures of orthophosphate and explain why these structures are not significant in ATP.
The answer would be as shown in Figure 15.5 in the textbook. Each resonance structure would have an overall −2 charge. These structures do not contribute to the stabilization of ATP because the positively charged oxygen is next to a positively charged phosphorus. Section: 15.2
What would happen if an enzyme mutation occurred that seriously inhibited the activity of amylase?
The carbohydrates would not be shortened to smaller simple sugars. The result would be an inability of the lumen to transport the sugars to the blood. Osmotic changes in the gut would lead to very watery stool. Section: 14.3
If many compounds are common to both anabolic and catabolic paths, how can metabolism be controlled?
The enzymes and their activities can be controlled by the energy charge in the cell. The biosynthetic and catabolic paths are different from each other and may even be located in different compartments in the cell. Thus the two opposing processes can be controlled independently. Section: 15.5
How does the structure of cholesterol give it a unique structural quality among the lipids?
The flat double-bonded fused ring creates a bulky hydrophobic moiety for several potential modifications. Section: 11.3
Explain how a metabolic pathway can contain an energetically unfavorable reaction yet still occur.
The free-energy changes of the individual steps in a pathway are summed to determine the overall free-energy change. Thus, a step that might not normally occur can be driven if it is coupled to a thermodynamically stable reaction. Section: 15.1
Why are membranes impermeable to most substances?
The hydrophobic core of the membrane makes crossing of polar molecules difficult due to water associated with the polar molecule known as the solvation shell. To cross a membrane, a polar molecule must first shed its solvation shell, which is not energetically favorable for highly polar species. Section: 12.1
Draw a bilayer membrane that has both an integral and peripheral protein present.
The membrane should be depicted as a bilayer, with the head groups indicated by small balls, and the alkyl chains represented by long tails. The peripheral membrane proteins would be loosely attached to the outside of the membrane, and the integral proteins would be shown traversing the membrane. Figure 12.8 in the textbook provides an example of this. Section: 12.3
What is oxidative phosphorylation?
The process by which ATP is formed by the phosphorylation of ADP using the energy of the proton gradient that was generated by the transfer of electrons from reduced coenzymes to oxygen. Section: 15.3
Why is the acidification of the stomach juices important for the digestion of proteins?
The proteases involved in the initial digestion of proteins into oligopeptides are most active at low pHs. For the proteases to bind to their substrate, the digested protein must be partially denatured by the acidic condition of the stomach. Section: 14.2
How do secondary transporters drive the transport of a substance up its concentration gradient?
The thermodynamically uphill flow of one molecule is coupled to the downhill flow of another. Section: 12.5
Why do most phospholipids preferentially form sheets instead of micelles?
The two tails in phospholipids makes it sterically unstable for them to form micelles. Section: 12.1
Describe the selectivity of the potassium ion channel.
There are critical amino acids on helical domains in the pore of the channel that face the center. These residues point a carboxyl group inward, which binds potassium ions, creating a selective filter for the K+ ions. composed of two parts: the filter, which selects and allows potassium but not sodium to pass, and the gate, which opens and closes the channel based on environmental signals. Section: 12.5
A person who is prescribed a phospholipase C (PLC) inhibitor for an inflammatory problem now has digestive issues and is suffering from symptoms of malnourishment. What is the likely cause of the malnourishment?
There may be an off-target effect or side effect of the drug. If the PLC activity in pancreas is altered, there will be little or no zymogen granule release. This will result in a loss of active protease activation and ultimately no digestion of the larger foodstuffs. Section: 14.5
Explain why fats are an efficient way to store biochemical energy.
This has to do with the anhydrous nature of fat (less water means more mass of fat per gram) and with the fact that fatty acid tails are more reduced than carbohydrates or amino acids. We will learn later that the transfer of electrons through redox reactions leads to ATP production. Section: 11.2
Explain the mechanism of snake bite poisons.
This is a problem of digestion from the inside out. For example, rattlesnake venom contains a host of digestive enzymes that begin the digestive process before the prey has reached the snake's stomach. Examples include phospholipases that cause hemolysis and collagenase and hyaluronidase that digest components of connective tissue. Section: 14.4
Explain the biochemical nature of why trans bonds do not have the same effect as cis bonds on the melting point of fatty acids.
This is due to the order or disorder when a double bond is introduced. A trans double bond maintains the linear shape of the fatty acid, while a cis double bond creates a kinked or bent shape. The latter reduces the number of contact points, thus reducing the amount of energy needed to melt the fatty acid lattice. Section: 11.1
The temperature at which a phospholipid membrane transitions from a rigid to a fluid state is referred to as _______________.
Tm, or melting temperature Section: 12.2
What are the two systems for naming the positions of the double bonds? Provide examples.
Two systems are used. One system refers to the double bond relative to the last, or omega (ω), carbon. (An example would be ω-3 fatty acids.) The other system uses notation that indicates the position of the double bond relative to the carboxyl carbon, and indicates if the bond is cis or trans. (An example would be cis-Δ9.) Section: 11.1
Why are fats a more efficient fuel source than carbohydrates?
When any fuel molecule is oxidized, the free energy released is used to generate ATP. In that carbohydrates are already more oxidized than fats, less energy is released in the complete oxidation to CO2. Section: 15.3
What is the relationship between the energy charge of a cell and control of the ATP-generating pathway?
When the energy charge is high, ATP-generating pathways are inhibited and visa versa. Section: 15.5
The ______________ pH of the stomach is important for the denaturation of proteins.
acidic Section: 14.1
The ______________ molecule brings breakdown products of proteins, sugars, and fats to the citric acid cycle in the third state of catabolism.
acetyl CoA Section: Introduction
____________: This substance inhibits prostaglandin H2 synthase-1 by blocking the channel through which the substrate, arachidonate, travels.
acetylsalicylic acid (aspirin) Section: 12.3
The emulsification of lipids requires that the ______________ amphipathic molecule be released from the gall bladder.
bile salts Section: 14.4
An increase in the ratio of saturated to unsaturated fatty acid chains in a membrane _______________ the fluidity of the membrane.
decreases Section: 12.2
In phosphoglycerides, the fatty acids are linked to the glycerol backbone by the ________________ linkages.
ester Section: 11.3
____________ lipids are less resistant to hydrolysis, potentially because of the way the acyl chain is linked to the glycerol backbone.
ether-linked lipid Section: 11.3
Protein digestion leads to the release of ______________ by intestinal mucosal cells into the blood for use by other tissues.
free amino acids Section: 14.2
Cholecystokinin is a hormone which activates ____________ signaling pathways.
g-protein Section: 14.5
Both CCK and ______________ induce feelings of satiety and inhibit eating.
glucagon-like peptide 1 Section: 14.5
Lipids which contain carbohydrates is/are ____________.
glycolipid Section: Introduction
____________: These membrane components contain carbohydrates.
glycolipids Section: 12.1
Cells maintain a ____________ concentration of intracellular potassium as compared to the extracellular concentration.
high Section: 12.5
ATP-generating (catabolic) pathways are inhibited by a _________________ energy charge.
high Section: 15.5
In digestion, proteins are ____________ into their individual 20 amino acids.
hydrolyzed Section: Introduction
____________: The type of amino acid found in the transmembrane helix of an integral protein.
hydrophobic Section: 12.2
The driving force for the formation of membrane bilayers is/are the:
hydrophobic effect Section: 12.1
____________ membrane proteins are embedded in the hydrocarbon chains of membrane lipids.
integral Section: 12.3
The pancreas releases ______________ to neutralize the acid produced in the stomach.
sodium bicarbonate Section: 14.1
____________: A complex amino alcohol backbone for membrane lipids.
spingosine Section: 11.3
One way that metabolism is regulated is through control of the accessibility of _________________.
substrates Section: 15.5
The acetyl group is attached to coenzyme A by a(n) _________________ bond.
thioester Section: 15.4
____________: The storage form of fatty acids.
triacyglycerol Section: Introduction
The presence of double bonds in fatty acids limits tight packaging and the number of ________________ interactions.
van der Waals Section: 11.1
________________ is the noncovalent force which favors close packing of the tails of the lipids in a membrane.
van der Waals Section: 12.1
The small organic compounds, ____________, are required in the diet of higher organisms and are components of coenzymes.
vitamins Section: 15.4
____________ has a high permeability through lipid bilayers.
water Section: 12.1 and Figure 12.4
