Biochem Exam 1
The number of hydrogen bonds formed between A and T are _________. A. 1 B. 2 C. 3 D. 4
2
____________ are the number of hydrogen bonds formed between G and C. A. 1 B. 2 C. 3 D. 4
3
In addition to phospholipids and glycolipids, which of the following is a major type of membrane lipid? A. cholesterol B. vitamin E C. triacylglycerol D. free fatty acids E. None of the answers is correct.
A
What is the [H+] concentration in a urine sample that has a pH of 6? Correct! A. 10-6 M B. 10-8 M C. 106 M D. 8 M
A. 10-6 M
What pairs of atoms in bases are involved in hydrogen bonds? A. N—H and O—H B. N—H and S—H C. O—H and P—O D. All of the above.
A. N—H and O—H
Why does DNA denature when the pH is raised above 9? A. Protons dissociate from guanine bases disrupting the hydrogen bonding to the other strand. B. Protons bind to guanine residues giving them additional positive charges which disrupt the hydrogen bonding to the other strand. C. Protons bind to functional groups that serve as hydrogen-bond acceptors, thus disrupting the hydrogen bonding to the other strand. D. Protons dissociate from the phosphate groups in the backbone, which disrupts the hydrogen-bonding pattern between strands.
A. Protons dissociate from guanine bases disrupting the hydrogen bonding to the other strand.
Hydrogen bonds are usually weaker than covalent bonds (true/false). A. True B. False
A. True
Glycoform refers to A. a single protein type that can have forms that differ only in their glycosylation. B. glycoproteins from the same gene family. C. a common core of sugars that can be found on many different proteins. D. All of the answers are correct. E. None of the answers is correct.
A. a single protein type that can have forms that differ only in their glycosylation.
The most common motif found in membrane spanning proteins is A. alpha helices of nonpolar amino acids that pass through the membrane. B. alpha helices of charged amino acids that form channels via extensive hydrogen bonding. C. a triple helix of alpha helices. D. a helix-turn-helix arrangement of the peptide strands. E. None of the answers is correct.
A. alpha helices of nonpolar amino acids that pass through the membrane.
Fehling's solution is used to differentiate between reducing and nonreducing sugars. Which type of ion in Fehling's solution allows for this differentiation? A. cupric B. sodium C. iodide D. hydroxide E. bicarbonate
A. cupricg
Which of the following is the storage form of glucose in animals? A. glycogen B. amylose C. amylopectin D. cellulose E. chitin
A. glycogen
What property is used to determine the probability that a segment of a protein will be found embedded in a membrane? A. hydropathy B. polarity C. acidity D. entropy E. solvation
A. hydropathy
The Second Law of Thermodynamics states A. the total entropy of a system and its surrounding always increases for a spontaneous process. B. temperatures will always decrease. C. the total energy of a system and its surroundings are constant. D. diversity is the result of gradual evolution.
A. the total entropy of a system and its surrounding always increases for a spontaneous process.
The enzyme that digests amylopectin is A. α-amylase. B. amylopectinase. C. cellulase. D. invertase. E. None of the answers is correct.
A. α-amylase.
The fundamental groups of organisms include Eukarya, Bacteria, and ____________. A. Drosophila B. Archaea C. Homo sapiens D. Arabidopsis thalia
Archaea
What is the [A-]/[HA] ratio when the weak acid is in a solution one pH unit below its pKa? A. 1:1 B. 1:10 C. 10:1 D. 2:1
B. 1:10
Typical van der Waals energies are about A. 4-20 kJ/mol B. 2-4 kJ/mol C. 200kJ/mol D. None of the above.
B. 2-4 kJ/mol
____________ bonds are the strongest bonds in molecules. A. Hydrogen B. Covalent C. Noncovalent D. Ionic
B. Covalent
For spontaneous reactions the G must be positive (true/false). A. True B. False
B. False
_________ is the class of glycoproteins with predominantly N-acetylgalactosamine moieties. A. Glycosaminoglycans B. Mucoproteins C. Starch D. Lectins E. Proteoglycans
B. Mucoproteins
Inhibitors against which viral enzyme have potential as anti-influenza agents? A. Calnexin B. Neuraminidase C. Selectin D. All of the answers are correct. E. None of the answers is correct.
B. Neuraminidase
What happens to nonpolar molecules in water? A. They dissolve independently B. They aggregate together C. They precipitate D. All of the above
B. They aggregate together
Which of the following helps regulate membrane fluidity in animals? A. proteins B. cholesterol C. ATP D. magnesium ions E. None of the answers is correct.
B. cholesterol
The simplest carbohydrates are the 3-carbon molecules: A. D- and L-glyceraldehyde. B. dihydroxyacetone and D- and L-glyceraldehyde. C. dihydroxyacetone and glycerate. D. dihydroxyacetone and glycerol E. None of the answers is correct.
B. dihydroxyacetone and D- and L-glyceraldehyde.
Two monosaccharides that differ in stereochemistry at only a single asymmetric carbon are called______. A. aldoses B. epimers C. anomers D. pentoses E. enantiomers
B. epimers
Which of the following is considered a metabolite, a substance that is chemically transformed in a biochemical process? A. deoxyribonucleic acid B. glycerol C. protein D. ribonucleic acid
B. glycerol
Which is the correct order of increasing bond energies? A. hydrogen bonds, covalent bonds, van der Waals interactions B. hydrogen bonds, electrostatic interactions, covalent bonds C. van der Waals interactions, covalent bonds, hydrogen bonds D. covalent bonds, hydrogen bonds, van der Waals interactions
B. hydrogen bonds, electrostatic interactions, covalent bonds
Which of the following membrane-bound organelles is thought to have evolved from bacteria by endosymbiosis? A. peroxisomes B. mitochondria C. cell walls D. nuclei E. endoplasmic reticulum
B. mitochondria
What important property is conferred on membranes by transport systems? A. asymmetry B. selective permeability C. bilayer D. amphiphatic nature E. None of the answers are correct.
B. selective permeability
Sugars are commonly linked to which amino acid residues in glycoproteins? A. tyrosine and asparagine B. serine, threonine, and asparagine C. serine, tyrosine, and asparagine D. serine and glutamine E. threonine and glutamine
B. serine, threonine, and asparagine
How many molecules thick are membranes? A. one B. two C. infinite D. varying thickness, depending on structure. E. None of the answers are correct.
B. two
____________ represents Gibbs-free energy. A. ΔH B. ΔG C. pH D. ΔS
B. ΔG
What is the number of carbons found in the most commonly observed fatty acids? A. 12 or 14 B. 14 or 16 C. 16 or 18 D. 18 or 20 E. 20 or 22
C. 16 or 18
The energies for hydrogen bonds are approximately A. 400 kJ/mol B. 100-240 kJ/mol C. 4-20 kJ/mol D. None of the above.
C. 4-20 kJ/mol
Which of the following is NOT correct concerning the structure given? A. It is a component of biological membranes. B. It is amphipathic. C. It is a sphingolipid. D. It is a phosphoglyceride. E. It is phosphatidyl choline.
C. It is a sphingolipid.
What did Watson and Crick suggest to be significant about the base pairing found in the helix? A. It allowed the DNA to twist in a helix. B. The DNA could be circular. C. It was a mechanism for copying. D. All of the above
C. It was a mechanism for copying.
If a particular reaction has a negative ΔG, is it likely to occur? A. Not unless energy is added to the system. B. Yes, if it is coupled to another reaction. C. Yes, it is spontaneous. D. No, it is not spontaneous
C. Yes, it is spontaneous.
Selectins are proteins that A. selectively bind proteins destined for lysozomes. B. aid in selection of proteins bound for the Golgi complex. C. bind immune-system cells as part of the inflammatory response. D. All of the answers are correct. E. None of the answers is correct.
C. bind immune-system cells as part of the inflammatory response.
Fructose can cyclize to (a) A. pyranose ring. B. furanose ring. C. both pyranose and furanose ring forms D. All of the answers are correct. E. None of the answers is correct.
C. both pyranose and furanose ring forms
Which of the following explains how some viruses gain entry into specific cells? A. by attaching to ion channels B. by cleaving the glycosidic bonds of cell surface glycoproteins and altering protein shapes C. by binding to glycoproteins on the cell surface that are unique to specific cells D. All of the answers are correct. E. None of the answers is correct.
C. by binding to glycoproteins on the cell surface that are unique to specific cells
What term describes stereoisomers that are mirror images of each other? A. anomers B. epimers C. enatiomers D. diastereomers E. meso compound
C. enatiomers
What type of enzyme synthesizes oligosaccharides? A. amylase B. sucrase C. glycosyltransferase D. β-galactosidase E. protein kinase
C. glycosyltransferase
An aldehyde and alcohol can react to form a A. hemialdol. B. hemiketal. C. hemiacetal. D. All of the answers are correct. E. None of the answers is correct.
C. hemiacetal.
What complex is observed between cholesterol and membrane phospholipids? A. salt bridge B. clathrate C. lipid raft D. phospholipid domain E. None of the answers is correct.
C. lipid raft
The low incidence of protein or lipid flip-flop in a membrane A. membrane fluidity. B. membrane melting temperatures. C. membrane asymmetry. D. membrane fluidity and membrane melting temperatures. E. All of the answers are correct.
C. membrane asymmetry.
Carbohydrate residues attached to the membrane lipids are almost always A. positioned on the intracellular side of the membrane. B. positioned on the inside center of the bilayer. C. positioned on the extracellular side of the membrane. D. positioned equally on both sides of the membrane. E. also covalently attached to membrane proteins.
C. positioned on the extracellular side of the membrane.
Entropy is defined as A. a spontaneous reaction B. the enthalpy of the system C. the measure of randomness of a system D. All of the above.
C. the measure of randomness of a system
The First Law of Thermodynamics states A. diversity is the result of gradual evolution. B. the total entropy of a system and its surroundings always increase for a spontaneous process. C. the total energy of a system and its surroundings are constant D. light both particle and wave.
C. the total energy of a system and its surroundings are constant
________________ is a membrane lipid composed of sphingosine, fatty acid, and a simple sugar like glucose or galactose.
Cerebroside
Approximately what percentage of the human genome encodes for proteins? A. 50% B. 90% C. 10% D. 3%
D. 3%
Hydrophobic molecules can be covalently attached to proteins to increase membrane association. Type(s) of group(s) include A. palmitoyl groups attached via Cys residues. B. glycolipid structures attached to the carboxy terminus. C. farnesyl groups attached via Cys residues. D. All of the answers are correct. E. None of the answers is correct.
D. All of the answers are correct.
What are lectins? A. proteins that bind the carbohydrates on glycoproteins and other macromolecules B. proteins that promote cell−cell interaction C. proteins found in animals, plants, and microorganisms D. All of the answers are correct. E. None of the answers is correct.
D. All of the answers are correct.
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 answers are correct. E. A and B.
D. All of the answers are correct.
The structure of DNA described by Watson and Crick included A. a double helix B. the sugar phosphate backbone aligned in the center of the helix C. the base pairs that are stacked on the inside of the double helix. D. Both A and C are correct
D. Both A and C are correct
Atoms commonly found in biological molecules that are often hydrogen-bond donors. A. carbon B. oxygen C. nitrogen D. Both oxygen and nitrogen
D. Both oxygen and nitrogen
Stereochemistry can be easily depicted in a simple form using A. ball-and-stick models. B. ribbon diagrams. C. space-filling models. D. Fisher projections.
D. Fisher projections.
What are the primary chemical components present in a phosphate buffer at pH 7.4? A. H3PO4 and PO4-3 B. H2PO4- and PO4-3 C. HPO4-2 and PO4-3 D. H2PO4- and HPO4-2
D. H2PO4- and HPO4-2
Using the Henderson-Hasselbach equation, calculate the pH of a buffer solution made from 0.20 M HC2H3O2 and 0.050 M C2H3O2- that has pKa= 4.7. A. 4.3 B. 5.1 C. 2.5 D. None of the above
D. None of the above
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 are referred to as a lipid bilayer.
D. The membrane lipids self-assemble to form the lipid bilayer.
What property of water is important for biological interactions? A. The polarity of water B. The density of water C. The cohesive properties of water D. The polarity of water and the cohesive properties of water
D. The polarity of water and the cohesive properties of water
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 bilayers made of lipids with polyunsaturated 16 carbon-fatty acids. E. All of the above all equivalent in fluidity.
D. a bilayers made of lipids with polyunsaturated 16 carbon-fatty acids.
Common carbohydrates found in nature are A. aldehydes with two or more hydroxyl groups. B. ketones with two or more hydroxyl groups. C. amines with two or more hydroxyl groups. D. aldehydes with two or more hydroxyl groups and ketones with two or more hydroxyl groups. E. All of the answers are correct.
D. aldehydes with two or more hydroxyl groups and ketones with two or more hydroxyl groups.
What term describes molecules that have both hydrophilic and hydrophobic moieties? A. amphoteric B. amphiprotic C. amphibian D. amphipathic E. None of the answers is correct.
D. amphipathic
Which of the following is among the most abundant organic molecules in the biosphere? A. glycogen B. amylose C. amylopectin D. cellulose E. chitin
D. cellulose
What is the most common process by which lipids and proteins move in the membrane bilayer? A. kinesin-mediated movement B. flip-flopping C. translocation D. lateral diffusion E. asymmetric longitudinal flipping
D. lateral diffusion
Which of the following are proteins that bind to specific carbohydrate structures in order to facilitate recognition between proteins and cells? A. mucoproteins B. glycosaminoglycans C. glycoproteins D. lectins E. proteoglycans
D. lectins
What gives proteins such a dominant role in biochemistry? A. the rigidity of the peptide backbone B. the ability to act as a blueprint C. their ability to self-replicate D. their ability to spontaneously fold into complex three-dimensional structures
D. their ability to spontaneously fold into complex three-dimensional structures
The degree of membrane fluidity in bacteria depends mainly on the percentage of A. lipids that contain sphingosine. B. glycolipids. C. free fatty acids. D. unsaturated fatty acids. E. None of the answers is correct
D. unsaturated fatty acids.
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 lipids and membrane proteins. D. van der Waals interactions and electrostatic and hydrogen bonding between the polar heads and surrounding water. E. electrostatic and hydrogen bonding between the polar heads and surrounding water.
D. van der Waals interactions and electrostatic and hydrogen bonding between the polar heads and surrounding water.
A _______________ is a stereoisomer that is not a mirror image.
Diastereoisomer
Membranes are primarily comprised of A. lipids B. proteins C. carbohydrates D. All of the answers are correct E. A and B
E. A and B
How do the membranes of archaea differ from bacteria and eukaryotes? A. The lipids do not contain a carboxylic acid ester, but instead have an ether link to the glycerol. B. The alkyl chains are branched. C. The stereochemistry of the central carbon of glycerol is inverted. D. A and C are correct. E. All the answers are correct.
E. All the answers are correct.
What molecule are most sugars attached to prior to their transfer to proteins? A. GDP B. GMP C. AMP D. UMP E. UDP
E. UDP
What substance inhibits prostaglandin H2 synthase-1 by blocking the channel through which the substrate, arachidonate, travels? A. acetaminophen B. Celebrex C. Zoloft D. Vioxx E. acetylsalicylic acid
E. acetylsalicylic acid
The nutritional storage form(s) of glucose in plants is/are A. glycogen. B. amylose. C. amylopectin D. cellulose. E. amylose and amylopectin.
E. amylose and amylopectin.
At what location(s) within a cell is/are proteins glycosylated? A. ribosome B. endoplasmic reticulum C. complex D. lysosome E. endoplasmic reticulum and Golgi complex
E. endoplasmic reticulum and Golgi complex
Glycoproteins are normally A. found on membranes B. secreted as extracellular proteins. C. found inside organelles. D. All of the answers are correct. E. found on membranes and secreted as extracellular proteins.
E. found on membranes and secreted as extracellular proteins.
What membrane components contain carbohydrates? A. lipid-linked proteins B. cholesterol C. integral membrane proteins in contact with the cytoplasm D. phosphatidylserine E. glycolipids
E. glycolipids
Which of the following terms describes a class of compounds with the molecular formula (CH2O)n? A. proteoglycans B. glycogen C. mucoproteins D. polysaccharides E. monosaccharides
E. monosaccharides
______________ is a disaccharide composed of galactose and glucose joined by a β-1,4 glycosidic bond.
Lactose
___________________ membrane proteins are bound to membranes primarily by electrostatic and hydrogen bond interactions with the head groups of lipids.
Peripheral
Plant starch is composed of amylose, a linear polymer of glucose, and a branched polymer of glucose referred to as _______________.
amylopectin
In N-linked glycoproteins, the carbohydrate portion is attached to a(n)_____________ residue in the protein.
asparagine
In C-type lectins, a _______________ acts as a bridge between the carbohydrate and the protein.
calcium ion
In animals, ________________ is the key regulator of membrane fluidity.
cholesterol
In phosphoglycerides, the fatty acids are linked to the glycerol backbone by ______________ linkages.
ester
A _______________ is a five-membered ring formed from a monosaccharide.
furanose
A given protein with several potential glycosylation sites can have many different glycosylated structures called ________________.
glycoforms
When an open-chain aldose cyclizes into a ring, it forms a _______________.
hemiacetal
___________________ are aqueous compartments enclosed by a lipid bilayer which can be created in a laboratory.
lipid vesicles
The temperature at which a phospholipid membrane transitions from a rigid to a fluid state is referred to as _______________.
melting temperature
Ionized fatty acids readily form ______________ in aqueous solutions.
micelles
__________________ contain a double bond three carbons from the distal end of the fatty acid.
omega-3 Fatty acids
The rate of diffusion is such that a phospholipid molecule can travel from one end of a bacterium to the other in _______________ of time.
one second
Some proteins are anchored to the membrane by being covalently attached to a _______________ group by a thioester linkage to a specific (non-C-terminal) cysteine residue.
palmitoyl
The influenza virus recognizes _______________ (a carbohydrate) residues of glycoproteins present on cell surface.
sialic acid
The DNA backbone is made from repeating _________. A. sugar-phosphate units B. hydrogen bonds C. amino acids D. nitrogen bonds
sugar-phosphate
DNA is made from the building blocks adenine, guanine, cytosine, and ____________. A. uridine B. thymine C. histidine D. histidine
thymine
Maltose is composed of two molecules of glucose linked together by a(n) ____________ glycosidic bond.
α-1,4
