Exam 1 Homework and Reading Quiz Problems

Match the polymeric structure features to which it belongs to proteins or glycogen: Linear Branched Glucose Polymer amino acid polymer

Protein: Linear Amino Acid Polymer Glycogen: Branched Glucose Polymer

The major conclusion of the experiment of C. Anfinsen involving ribonuclease was that

the information dictating how the protein should fold is contained in the amino acid sequence

The genetic information present in DNA is described by the sugar-phosphate backbone structure of the DNA. the base composition of the DNA. the sequence of bases along a DNA strand. the presence of base‑pairing between the DNA strands.

the sequence of bases along a DNA strand

Enzyme-linked immunosorbent assays (ELISA) are useful in biochemistry because

they can be used to detect very small amounts of a specific material

Anfinsen started with purified ribonuclease A in its native state. To begin he (1) TREATED IT WITH HCL TO DISRUPT NONCOVALENT BONDS. OXIDIZED THE S-H BONDS AND THEN REMOVED B-MERCAPTOETHANOL AND UREA. REMOVED THE UREA AND B-MERCAPTOETHANOL, RESULTING IN OXIDATION OF S-H BONDS. TREATED IT WITH B-MERCAPTOETHANOL AND 8M UREA This process resulted in denaturated ribonuclease A protein. Next he (2) TREATED IT WITH HCL TO DISRUPT NONCOVALENT BONDS. OXIDIZED THE S-H BONDS AND THEN REMOVED B-MERCAPTOETHANOL AND UREA. REMOVED THE UREA AND B-MERCAPTOETHANOL, RESULTING IN OXIDATION OF S-H BONDS. TREATED IT WITH B-MERCAPTOETHANOL AND 8M UREA. which allowed ribonuclease A to return to its native state

(1) TREATED IT WITH B-MERCAPTOETHANOL AND 8M UREA (2) REMOVED THE UREA AND B-MERCAPTOETHANOL RESULTING IN OXIDATION OF S-H BONDS

For the peptide Ala‑Arg‑Lys‑Ala‑Asn‑Ser‑Ala‑Ser, what would be the expected charges at pH 1, 7, and 13? +2, +2, −1 +2, +1, −1 +3, +2, −1 +3, +3, 0

+3, +2, -1

If an aqueous solution has a hydrogen ion concentration of 1×10−5 M,1×10−5 M, what is the concentration of hydroxyl ion ([OH−])?

1 x 10^-9

In what year did Francis Crick propose the scheme that underlies information processing at the level of gene expression?

1958

Beta (β) sheets are a type of secondary structure in proteins. A segment of a single chain in an antiparallel β sheet has a length of 263 Å . How many residues are in this segment?

75

The protonated amino group of an amino acid will lose a proton when the pHpH approaches 9. 5. 7.4. 3.

9

Identify the true statements regarding disulfide bridges (disulfide bonds). Disulfide bridges are formed by an irreversible oxidation reaction. A disulfide bridge forms between two cysteine residues. Disulfide bridges are important to primary and secondary structure. Disulfide bridges have a stabilizing effect on proteins. Disulfide bridges can exist between two amino acid residues on different chains.

A disulfide bridge forms between two cysteine residues Disulfide bridges have a stabilizing effect on proteins Disulfide bridges can exist between two amino acid residues on different chains

Which statements about peptide bonds are true? Peptide bond formation is a hydrolysis reaction. A tripeptide contains three amino acid residues. Peptides are polymers of amino acids. Peptide bonds are ester linkages. A tetrapeptide contains five amino acid residues.

A tripeptide contains three amino acid residues Peptides are polymers of amino acids

Which statements accurately describe the polarity and electronegativity of water? Water molecules have slight charges and are attracted to each other by ionic bonds. A water molecule is polar, but it has no net charge. The atoms of the water molecule are held together by covalent bonds. Water has polar bonds and a linear symmetrical shape, so it is polar. The oxygen atom in a water molecule is strongly electronegative.

A water molecule is polar, but it has no net charge. The atoms of the water molecule are held together by covalent bonds. The oxygen atom in a water molecule is strongly electronegative.

Lysosomes are membranous organelles that contain digestive enzymes. Lysosomes can function inside the cell, where their enzymes digest particles taken in by endocytosis or worn‑out cell components. Lysosomes can also release their enzymes outside the cell, where the enzymes break down extracellular material. Wolman disease is a lysosomal storage disease that results in the buildup of lipids (fats) in the spleen, liver, bone marrow, small intestine, adrenal glands, and lymph nodes. Which is the probable cause? A. A gene mutation results in a shortage of lipid‑digesting enzymes in the lysosome. B. The Golgi apparatus delivers lipid‑digesting enzymes to the lysosome, which destroy it. C. Lysosomes accumulate extra lipid‑digesting enzymes. D. The cell does not take up lipid molecules by endocytosis.

A. A gene mutation results in a shortage of lipid-digesting enzymes in the lysosome.

Which statement is yes of carbon‑based molecules and silicon‑based molecules? A. Both carbon and silicon can form four covalent bonds. B. A silicon-silicon bond is stronger than a carbon-carbon bond. C. Carbon can be combusted, whereas silicon cannot. D. All three statements are true.

A. Both Carbon and Silicon can form four covalent bonds.

Which statement is yes of a carbon-based molecules and silicon-based molecules? A. Both carbon and silicon can form four covalent bonds. B. A silicon-silicon bond is stronger than a carbon-carbon bond. C. Carbon can be combusted, whereas silicon cannot. D. All three statements are true.

A. Both carbon and silicon can form four covalent bonds

Rheumatoid arthritis (RA) is an autoimmune disease marked by inflammation and cartilage destruction. Although the causes are not known, it may be linked to lysosomal proteases (protein‑digesting enzymes). How may lysosomal proteases be linked to RA? A. Excess lysosomal proteases are produced and released extracellulary, where they degrade collagen. B. Chondroblasts (cells in cartilage) sequester collagen‑building enzymes within lysosomes. C. The lysosomes in cartilage tissue cannot fuse with protein‑containing vesicles. D. Cells produce defective lysosomal proteases, which break down proteins inefficiently.

A. Excess lysosomal proteases are produced and release extracellularly, where they degrade collagen.

Which statement on the amino acids found in proteins is true? Only some contain a central α carbon. All contain a central α carbon and the majority are dipolar ions, or zwitterions, at physiologic pH. All are dipolar ions, or zwitterions, regardless of the pH of their environment. All have a side chain except for glycine.

All contain a central a carbon and the majority are dipolar ions, or zwitterions, at physiologic pH

Which statement is true of the proteome? It includes the interactions of peptides that yield a functional unit. It varies with cell type. It varies with environmental conditions. All three statements are true.

All three statements are true.

Which amino acid would be positively charged at physiological pH? Asn Cys Asp Arg

Arg

Biological macromolecules can be divided into four different classes. Which type of molecule is NOT a major class of biological macromolecules? A. Carbohydrates B. Fatty Acids C. Nucleic Acids D. Lipids

B. Fatty Acids

If a solid line represents a covalent bond and a dotted line represents intermolecular attraction, which of the choices shows a hydrogen bond? A. H2O⋅⋅⋅⋅⋅⋅H−CH3H2O⋅⋅⋅⋅⋅⋅H−CH3 B. H3N⋅⋅⋅⋅⋅⋅H−O−HH3N⋅⋅⋅⋅⋅⋅H−O−H C. H4C⋅⋅⋅⋅⋅⋅H−FH4C⋅⋅⋅⋅⋅⋅H−F D. H−H

B. H3N⋅⋅⋅⋅⋅⋅H−O−HH3N⋅⋅⋅⋅⋅⋅H−O−H

When sequencing a protein, it is necessary to break disulfide bonds within a polypeptide chain. What reagent is used to break the disulfide bonds?

B-mercaptoethanol

Biological membranes are present in all cells, and they make up the end-membrane system of eukaryotic cells. Among other functions, they act as barriers that selectively allow the transport of small molecules and inns into and out of the cell or organelle. Which of the choices best describes a biological membrane? A. a bilayer containing lipids with hydrophobic head groups oriented toward the solvent (extracellular fluid and cytosol) and hydrophilic tail groups pointing inward B. a bilayer containing lipids with hydrophilic head groups oriented toward the solvent (extracellular fluid and cytosol) and hydrophobic tail groups pointing inward C. a bilayer containing lipids with hydrophilic head groups pointing inward and hydrophobic tail groups oriented toward the solvent (extracellular fluid and cytosol)

B. a bilayer containing lipids with hydrophilic head groups oriented toward the solvent (extracellular fluid and cytosol) and hydrophobic tail groups pointing inward

What do a helices and B sheets have in common?

Both are stabilized by hydrogen bonding involving carbonyl oxygens and amide nitrogens.

The genetic information present in DNA is described by A. the presence of base-pairing between the DNA strands B. the sugar-phosphate backbone structure of the DNA. C. the base composition of the DNA D. the sequence of the bases along the DNA Strand

D. the sequence of the bases along the DNA strand

What happens during transcription?

DNA serves as the template for a new molecule of RNA

Suppose a team of researchers sequences the genome and measures the proteome of a human skin cell and a human kidney cell. Will there be a greater difference between the genome or the proteome between the two cells?

Differences in gene expression and post-transcriptional mRNA processing lead to a greater difference in the proteome than the genome between the two cells.

What are characteristics of DNA?

Double-stranded deoxyribose backbone contains the base thymine

Which of the constituents found in eukaryotic cells are correctly ranked from largest to smallest? A. Cell > mitochondrion > protein > ribosome > amino acid > water molecule > proton B. proton > water molecule > amino acid > protein > ribosome > mitochondrion > cell nucleus C. cell nucleus > mitochondrion > ribosome > water molecule > protein > amino acid > proton D. mitochondrion > cell nucleus > ribosome > water molecule > protein > proton > amino acid E. cell nucleus > mitochondrion > ribosome > protein > amino acid > water molecule > proton

E. cell nucleus > mitochondrion > ribosome > protein > amino acid > water molecule > proton

Translate the given amino acid sequence into one‑letter code. Glu-Leu-Val-Ile-Ser-Ile-Ser-Leu-Ile-Val-Ile-Asn-Gly-Ile-Asn-Leu-Ala-Ser-Val-Glu-Gly-Ala-Ser

ELVISISLIVINGINLASVEGAS

Identify the predominant intermolecular forces in each of the given substances. Electrostatic (ionic) interactions hydrogen bonding van der Waals interactions CaCl2 CH4 NH3 H2O (CH3)2CHOH

Electrostatic (ionic) interactions CaCl2 hydrogen bonding H2O NH3 (CH3)2CHOH van der Waals interactions CH4

What is the main difference between a prokaryotic cell and a eukaryotic cell?

Eukaryotic cells have a membrane-enclosed compartments

Classify the words or phrases as descriptions or examples of fibrous proteins, globular proteins, or both. FIBROUS PROTEINS GLOBULAR PROTEINS BOTH structure is rod-like exhibit primary protein structure some function as enzymes insoluble in water soluble in water intermediate filaments myoglobin polymers of amino acids structure is somewhat spherical primarily function as structural proteins in the cell

FIBROUS PROTEINS structure is rod-like intermediate filaments insoluble in water primarily function as structural proteins in the cell GLOBULAR PROTEINS some function as enzymes structure is somewhat spherical myoglobin soluble in water BOTH exhibit primary protein structure polymers of amino acids

The shape of hair is determined in part by the pattern of disulfide bonds in keratin, its major protein. From first to last, arrange the five steps needed to induce permanent curls in hair. KERATIN'S AMINO ACIDS REARRANGE INTO THE CURLED CONFORMATION. PHYSICALLY CURL THE HAIR. APPLY A THIOL-CONTAINING REAGENT AND GENTLE HEAT. APPLY AN OXIDIZING AGENT. KERATIN'S DISULFIDE BONDS BREAK. KERATIN'S a-HELICES CONVERT TO B-SHEETS. KERATIN'S DISULFIDE BONDS REFORM TO HOD SHAPE.

First Step APPLY THIOL-CONTAINING REAGENT AND GENTLE HEAT. KERATIN'S DISULFIDE BOND BREAK. PHYSICALLY CURL THE HAIR. APPLY OXIDIZING AGENT. KERATIN'S DISULFIDE BONDS REFORM TO HOLD.

Of the 20 amino acids that make up proteins, which is most likely to be present with its R group in a mixture of ionization states near physiological pH? Tyr His Glu Gly

His

What is the MOST abundant element in human beings by percentage of total atoms?

Hydrogen

What is the MOST abundant element in human beings by percentage of total atoms? hydrogen oxygen nitrogen carbon

Hydrogen

Certain intrinsically disordered proteins protect tardigrades from desiccation. What property of intrinsically disordered proteins will most likely allow them protect tardigrades from desiccation?

Intrinsically disordered proteins can interact with multiple proteins

Freediving is an activity in which a person dives, sometimes to great depth, without the use of scuba gear. The diver must hold his or her breath for the duration of the dive. The record depth, with no equipment such as diving fins, is 101 m; the official record time is over 11 minutes. Historically, freediving has been used by pearl divers and sponge divers. Some freedivers hyperventilate (breathe rapidly and deeply) before diving. Hyperventilation can change the concentration of CO2 in the blood and may increase the length of time that a person feels like he or she can hold his or her breath. How does hyperventilation affect blood pH? It decreases CO2 and increases H+ in the blood, increasing pH. It decreases CO2 and H+ in the blood, increasing pH. It increases CO2 and H+ in the blood, decreasing pH. It increases CO2 and decreases H+ in the blood, increasing pH.

It decreases CO2 and H+ in the blood, increasing pH.

Which statement is no of Brownian motion? It is due to thermal noise. It causes the random movement of pollen granules suspended in water. It is independent of temperature. It is due to the random fluctuation of the energy content of the environment.

It is independent of temperature

Which of the choices are components of biological membranes? Select all that apply Lipids Proteins Nucleic Acids

Lipids and Proteins

Tropomyosin, a 70-kDa muscle protein, is a two‑stranded α‑helical coiled coil. Estimate the length of the molecule.

Molecule length: 464

Which statement is true of the chirality of amino acids found in proteins? D amino acids alternate with L amino acids in certain regions of proteins. Proteins contain both D and L amino acids. Only L amino acids are found in proteins. Only D amino acids are found in proteins.

Only L amino acids are found in proteins

Classify each protein example according to its highest level of protein structure. PRIMARY STRUCTURE SECONDARY STRUCTURE TERTIARY STRUCTURE QUATERNARY STRUCTURE hemoglobin the C helix of a a-lactalbumin myoglobin with heme Gly-Ala-Val-Leu

PRIMARY STRUCTURE Gly-Ala-Val-Leu SECONDARY STRUCTURE the C helix of a-lactalbumin TERTIARY STRUCTURE myoglobin with heme QUATERNARY STRUCTURE hemoglobin

Determine the highest level of protein structure described by each item. PRIMARY STRUCTURE SECONDARY STRUCTURE TERTIARY STRUCTURE QUATERNARY STRUCTURE overall macromolecule structure containing more than one polypeptide chain B-pleated sheet order of amino acids overall shape of a single polypeptide unit a-helix

PRIMARY STRUCTURE order of amino acids SECONDARY STRUCTURE B-pleated sheet a-helix TERTIARY STRUCTURE overall shape of a single polypeptide unti QUATERNARY STRUCTURE overall macromolecule structure containing more than one polypeptide chain

In numerous studies, treatment of prion preparations with ionizing and UV radiation does not reduce transmission of disease; however; treatment with denaturants reduces disease transmission. What can be inferred from these observations? Choose all of the correct answers Prions do not contain genetic information, which is affected by ionizing radiation. Prions are proteins. Denaturants may affect the tertiary structure of prions.

Prions do not contain genetic information, which is affected by ionizing radiation. Prions are proteins. Denaturants may affect the tertiary structure of prions.

Classify each statement based on whether it describes prokaryotes only, eukaryotes only, or can describe both prokaryotes and eukaryotes. Unicellular Multicellular have a true nucleus are generally less than 2 um lack a discrete nucleus

Prokaryotes: Lack a discrete nucleus are generally less than 2um Eukaryotes: multicellular have a true nucleus Both: unicellular

Which amino acid contains a guanidinium group? Y R G V

R

Arrange the steps of the formation of a secretory protein from its gene to its exocytosis RNA POLYMERASE BINDS TO THE PROMOTER REGION OF A GENE ENCODING A SECRETORY PROTEIN the protein enters the lumen of the endoplasmic reticulum the protein is packaged into secretory vesicles the gene undergo transcription the protein is sequestered into transport vesicles and sent to the Golgi complex the RNA is translated into protein by ribosomes on the endoplasmic reticulum EXOCYTOSIS FROM THE CELL

RNA POLYMERASE BINDS TO THE PROMOTER REGION OF A GENE ENCODING A SECRETORY PROTEIN. The gene undergoes transcription. The RNA is translated into protein by ribosomes on the endoplasmic reticulum. The protein enters the lumen of the endoplasmic reticulum. The protein is sequestered into transport vesicles and sent to the Golgi complex. The protein is packaged into secretory vesicles. EXOCYTOSIS FROM THE CELL.

Translation: Transcription: Replication:

RNA->protein DNA->RNA DNA->DNA

When performing site-directed mutagenesis to test predictions about which residues are essential for protein function, which amino acid substitution would disrupt protein structure the most. Val replaced by: Ala or Phe Gln replaced by: Asn or Glu Lys replaced by: Arg or Asp Ala replaced by: Gly or His

Val replaced by Phe Gln replaced by Glu Lys replaced by Asp Ala replaced by His

Examine the peptide. The-Glu-Pro-Ile-Val-Ala-Pro-Met-Glu-Tyr-Gly-Lys Write the sequence using one-letter abbreviations. Estimate the net charge on the peptide at pH 7. Estimate the net charge on the peptide at pH 12.

TEPIVAPMEYGK Charge at pH 7: -1 Charge at pH 12: -4

Protein disulfide isomerase (PDI) is a protein folding enzyme that catalyzes disulfide-sulfhydryl exchange reactions. Ribonuclease is an enzyme with 2 b-sheets, 3 a-helices, and 4 disulfide bridges critical to the stability of its structure. PDI rapidly converts inactive, scrambled ribonuclease to enzymatically active ribonuclease. This process is driven by the decrease in free energy as the scrambled conformations are converted into the stable, active conformation of the enzyme. In contrast, PDI rapidly inactivates insulin. What does PDI's effect on insulin imply about the structure of insulin?

The active conformation of insulin is not the most thermodynamically preferred form.

Consider an experiment where your goal is to isolate Bruton's tyrosine kinase (BTK) enzyme from a whole‑cell lysate. You have an affinity chromatography column with a tyrosine kinase inhibitor molecule covalently attached to the beads. The tyrosine kinase inhibitor binds and inhibits BTK. As a result of the experiment, you are able to elute BTK from the column, but in a mixture of other tyrosine kinases. Why are tyrosine kinases other than BTK present in the eluate? The kinase inhibitor has low specificity. BTK is rapidly degraded during cell lysis. BTK is inactive in the cell. The kinase inhibitor has low binding affinity.

The kinase inhibitor has low specificity

In the 1950s, Christian Anfinsen demonstrated the renaturation of the protein ribonuclease (RNase) in vitro. After reduction and the addition of urea, the protein was in an unfolded state. After removing the urea and then the reducing agent, the protein oxidized and refolded, with greater than 90% activity. If reducing agent removal occurs before removing the urea, the protein showed less than 5% activity. Why does synthetically produced RNase refold incorrectly if the reducing agent is removed before urea removal? Contaminants in the RNase preparation would form covalent bonds with the protein, preventing reactivation. The protein would not fully denature. Disulfide bonds are not positioned correctly unless weak bonding interactions are present. Urea would participate in weak bonding interactions with RNase, preventing oxidation of Cys.

The protein would not fully denature

Select the true statements about protein secondary structure. Peptide bonds stabilize secondary structure. The secondary level of protein structure refers to the spatial arrangements of short segments of the protein. In a β‑pleated sheet, the side chains extend above and below the sheet. In an α‑helix, the side chains are located inside the helix. The β‑pleated sheet is held together by hydrogen bonds between adjacent segments.

The secondary level of protein structure refers to the spatial arrangements of short segments of the protein In a B-pleated sheet, the side chains extend above and below the sheet The B-pleated sheet is held together by hydrogen bonds between adjacent segments

Which statement is false regarding peptide bonds? They tend to be planar. They contain an unusually long carbon-carbon bond. They are generally in the trans and rarely in the cis configuration. They tend to have the amide nitrogen protonated to give a positive charge.

They tend to have the amide nitrogen protonated to give a positive charge

Select all the choices that correctly describe the Golgi apparatus of the cell. Aerobic respiration is carried out by this organelle, which produces ATPATP . This organelle is part of the endomembrane system. Proteins are modified by this organelle and repackaged into transport vesicles. Toxins in the cell are inactivated by this organelle.

This organelle is part of the end-membrane system Proteins are modified by this organelle and repackaged into transport vesicles

What is central dogma?

Transcription is the process of synthesizing RNA from DNA. Translation is the process of synthesizing an amino acid sequence from RNA

What is the hydrogen ion concentration of a solution with pH=2.25?

[H+]=.00562

During exercise when the body lacks an adequate supply of oxygen to support energy production, the pyruvate that is produced from the breakdown of glucose is converted into lactate. High lactate levels can lead to acidity in the muscle cells as some of the lactate hydrolyzes to lactic acid. The dissociation of lactic acid to lactate is shown in the reaction. Lactic acid has a pKa of 3.86 A solution containing a mixture of lactic acid and lactate was found to have a pH of 4.13. Calculate the ratio of the lactate concentration to the lactic acid concentration in this solution.

[lactate]/[lactic acid]=1.86

Which structure represents the secondary structure of a protein?

a B-pleated sheet

Which bond or interaction is considered covalent? a disulfide bond an ionic bond a hydrogen bond a van der Waals interaction

a disulfide bond

The partially positively charged hydrogen atoms of one water molecule can interact with the partially negatively charged oxygen atoms of another water molecule. This interaction between water molecules is called both a water bond and Brownian motion. a water bond. a hydrogen bond. both a hydrogen bond and Brownian motion.

a hydrogen bond

Select the descriptions that apply to the ribosome. a membranous network associated with protein production a molecular structure that is the site of protein synthesis a network of proteins that supports the cellular structure a cellular structure that is composed of both RNA and protein a membrane‑bound organelle that stores digestive enzymes

a molecular structure that is the site of protein synthesis a cellular structure that is composed of both RNA and protein

What is the method for ensuring that proteins are separated by size and not be charge during gel electrophoresis?

a negatively charged detergent binds to amino acids and denatures the protein

Select the phrases that describe the plasma membrane. a. maintains the correct ion concentration inside the cell b. creates a barrier between the inside and outside of the cell c. provides a rigid structure that allows the cell to hold its shape d. separates the nucleus and the cytosol

a. maintains the correct ion concentration inside the cell b. creates a barrier between the inside and outside of the cell

The p𝐾apKa of acetic acid is 4.76. 4.76. The pKa of trichloroacetic acid is 0.7. Calculate the equilibrium dissociation constant,Ka, of each acid. acetic acid: trichloroacetic acid: Which is the stronger acid?trichloroacetic acid acetic acid

acetic acid: 1.74x10^-5 Trichloroacetic acid: .2 trichloroacetic acid

A small generic section of the primary structure of an α helix is given by −amino acid1−amino acid2−amino acid3−amino acid4−amino acid5−amino acid6−amino acid7− Which amino acid residue's backbone forms a hydrogen bond with the backbone of the sixth (6th) residue? Which peptide segment is most likely to be a part of a stable a helix at physiological pH? −Glu−Glu−Glu−Glu−Glu− −Pro−Leu−Thr−Pro−Trp− −Gly−Gly−Gly−Ala−Gly− −Gly−Arg−Lys−His−Gly− −Tyr−Trp−Phe−Val−Ile− −Lys−Lys−Ala−Arg−Ser− −Glu−Leu−Ala−Lys−Phe−

amino acid2

Which weak acid would be best to use when preparing a buffer solution with a pHpH of 8.90? an acid with 𝐾a=0.00020 an acid with 𝐾a=2.5×10−6 an acid with 𝐾a=7.9×10−11 an acid with 𝐾a=1.6×10−5 an acid with 𝐾a=2.0×10−7 an acid with 𝐾a=1.3×10−9

an acid with Ka=1.3×10−9

The conversion of cysteine to cystine is what kind of reaction?

an oxidation

How does the hydrophobic effect influence protein folding? In an aqueous environment, nonpolar portions of the molecule

are found in the interior of the protein, away from water, which preserves the entropy of the water in solution.

Which statements correctly describe the rough endoplasmic reticulum (rough ER)? a. It contains enzymes that detoxify drugs. b. It is connected to the membrane of the nucleus. c. It is used to transport mRNA to the cell membrane. d. It has ribosomes bound to its membrane. e. It produces proteins that need to be modified before use.

b. It is connected to the membrane of the nucleus d. It is ribosomes bound to its membrane e. It produces proteins that need to be modified before use

Select the phrases that accurately complete the sentence. The mitochondrion a. is made up of pancake-like membrane stacks that package proteins in vesicles b. is a cellular scaffolding contained within a cell's cytoplasm c. contains unique DNA that is different from the cell's nuclear DNA d. contains digestive enzymes that break down cellular waste and debris e. has a double membrane, with ATP synthesis occurring at the inner membrane

c. contains unique DNA that is a different from the cell's nuclear DNA e. Has a double membrane, with ATP synthesis occurring at the inner membrane

The dielectric constant of the interior of a protein is considerably smaller than that of water. How would this difference in dielectric constants affect the strength of an electrostatic interaction between two opposite charges with the same distance between them if the charged groups were located in the interior of the protein rather than on its surface? The strength of the electrostatic interaction would be a. independent of the charges' location in the protein. b. stronger if the interacting charges were on the surface of the protein. c. stronger if the interacting charges were in the interior of the protein. d. stronger if one of the interacting charges was on the surface of the protein and the other was in the interior.

c. stronger if the interacting charges were in the interior of the protein.

For the amino acid alanine, the major species in solution at pH 7 is the zwitterionic form, which has a negatively charged carboxylic acid group and a positively charged amino group. There is a less common neutral form in which neither group is charged. The carboxylic acid group of alanine has a pKa of 3.3. The amino group of alanine has a pKa of 8. Estimate the ratio of the concentration of the neutral amino acid species to the zwitterionic species at pH 7.

concentration ratio: 1x10^-5

Give the formula of the conjugate base of HSO−4 conjugate base: Give the formula for the conjugate acid of HSO−4 conjugate acid:

conjugate base: SO4^2- Conjugate acid: H2SO4

Select the descriptions that apply to the smooth endoplasmic reticulum. a. a centrally located membranous structure with attached ribosomes b. a membrane‑enclosed organelle that stores DNA c. a membranous complex which produces secretory vesicles d. a membranous organelle around the nucleus that does not produce proteins e. an organelle that synthesizes fatty acids, phospholipids, and steroids

d. a membranous organelle around the nucleus that does not produce proteind e. an organelle that synthesizes fatty acids, phospholipids, and steroids

What descriptions apply to a chloroplast? a. an important site of glucose conversion to energy b. a membrane-bound organelle that is filled with ion-rich fluid c. an organelle whose membrane has a large surface area due to folds called cristae d. the main site of photosynthesis in a plant cell e. a membrane-bound organelle with stacks of thylakoid discs called grana

d. the main site of photosynthesis in a plant cell e. a membrane-bound organelle with stacks of thylakoid discs called grana

An assay is useful for what during protein purification?

detecting a protein in a sample

What can SDS polyacrylamide electrophoresis be used to do?

determine the molecular weight of subunits of an oligomeric protein

The first step in protein purification is called

differential centrifugation

Antibodies used as reagents to quantify proteins is the basis of a lab method called

enzyme-linked immunosorbent assay

Biological macromolecules can be divided into four different classes. Which type of molecule is NOT a major class of biological macromolecules? nucleic acids fatty acids carbohydrates lipids

fatty acids

Which amino acid has the simplest side chain? alanine glycine valine histidine

glycine

Water is said to be highly cohesive because water molecules interact with one another through covalent bonds. hydrophobic interactions. hydrogen bonds. van der Waals interactions.

hydrogen bonds

Water-soluble proteins, such as myoglobin, tend to fold such that

hydrophobic amino acid R groups are on the interior of the protein and hydrophilic groups are on the outside

The second law of thermodynamics states that a spontaneous process only increases the entropy of a system's surroundings. increases the total entropy of a system plus its surroundings. decreases the total entropy of a system plus its surroundings. only increases the entropy of the system.

increases the total entropy of a system plus surroundings

Cell membranes are composed of phospholipids that have head and tail regions. The phospholipid head is hydrophilic and spontaneously orients toward the environment. What of the phrases best describes the hydrophilic region of a phospholipid?

interacts with water

The three-dimensional structure is specified by

its amino acid sequence and environment

The three‑dimensional structure of a protein is specified by its amino acid sequence and environment. other proteins that assist it in folding correctly. interaction of the newly synthesized protein with the portion of DNA that encoded it. the temperature during its synthesis.

its amino acid sequence and environment

The pKa of lactic acid is 3.86, and its conjugate base is lactate. Which form of lactic acid predominates at pH 7.4? neither; lactic acid and lactate are equimolar lactic acid lactate

lactate

alpha helices are a secondary structure in proteins. What is the length of a 51.0 kDa single-stranded a-helical protein segment? Assume a mean residue mass of 100 Da

length: 695

What is the best method to precisely determine the mass of a protein?

mass spectrometry

Nucleic Acids are polymers of _____ Proteins are polymers of _____ Polysaccharides are polymers of ___

nucleotides amino acids monosaccharides

How many distinct tripeptides can be made from the four amino acids: leucine, histidine, alanine, and valine? Each amino acid may be used more than once.

number of distinct tripeptides: 64

A biological molecule can serve as a hydrogen bond donor if the hydrogen is attached to carbon in aromatic groups. carbon. any nonmetallic atom. oxygen or nitrogen.

oxygen or nitrogen

A. What is the pH of an aqueous solution with a hydrogen ion concentration of [H+]=5.1×10−3? B. What is the hydroxide ion concentration, [OH−], in an aqueous solution with a hydrogen ion concentration of [H+]=5.1×10−3? C. A monoprotic weak acid, HAHA, dissociates in water according to the reaction HA(aq)↽−−⇀H+(aq)+A−(aq)HA(aq)⁢↽−−⇀⁢H+⁡(aq)+A−⁡(aq) The equilibrium concentrations of the reactants and products are [HA]=0.100 M, [H+]=4.00×10−4 M, and [A−]=4.00 ×10−4 M. Calculate the Ka value for the acid HA.

pH=2.29 [OH-]=1.96x10^-12 Ka=1.6x10^-6

A patient is suspected of having low stomach acid, a condition known as hypochloridia. To determine whether the patient has this condition, her doctors take a 19.00 mL sample of her gastric juices and titrate the sample with 4.67×10−4 M KOH. The gastric juice sample required 5.88 mL of the KOH titrant to neutralize it. Calculate the pH of the gastric juice sample. Assume the sample contained no ingested food or drink which might otherwise interfere with the titration. For the patient to be suffering from hypochloridia, the pH of the gastric juices from the stomach must be greater than pH 4.4. Does the patient have hypochloridia? yes unable to determine no

pH=3.84 no

If a buffer solution is 0.290 M in a weak acid (𝐾a=4.4×10−5) and 0.590 M in its conjugate base, what is the pH?

pH=4.71

To indicate the pHpH of a substance, one can use a dye that is both an acid and that appears as different colors in its protonated and deprotonated forms. Suppose that you have a 0.001 M solution of a dye with a pKa of 7.2. From the color, the concentration of the protonated form, HA, is 0.0002 M. Assume that the remainder of the dye is in the deprotonated form, A−. What is the pH of the solution? Give your answer to one decimal place.

pH=7.8

A monoprotic weak acid, HAHA, dissociates in water according to the reaction HA(aq)↽−−⇀H+(aq)+A−(aq)HA(aq)⁢↽−−⇀⁢H+⁡(aq)+A−⁡(aq) The equilibrium concentrations of the reactants and products are [HA]=0.190 M, [H+]=4.00×10−4 M, and [A−]=4.00×10−4 M. Calculate the value of pKa for the acid HA.

pKa=6.07

Which pair of terms describes molecules that can dissolve in water? polar and hydrophilic polar and hydrophobic nonpolar and hydrophilic nonpolar and hydrophobic

polar and hydrophilic

Experiments performed with biological systems require a buffer that will not interfere with the stability and activities of the biological components. In 1966, Norman Good and his colleagues began a series of investigations that established criteria for new zwitterionic buffers that would be optimal for experimentation with biological systems. These criteria included: pKa between 6 and 8 highly water soluble minimally permeable to biological membranes minimal effects of salt concentration minimal effect of temperature on p𝐾a (Δp𝐾a/ ∘C<0.02) minimal effect of concentration on p𝐾a minimal interaction with metal ions nontoxic high chemical stability minimal absorbance between 240-700 nm For each buffer given, choose the property that does not meet Good's criteria for biochemical buffers. Properties of acetate buffer: highly water soluble Δp𝐾a/ ∘C=−0.0002 p𝐾a at 25∘C=4.76 does not cross lipid bilayer All the properties fulfill the Good's buffer criteria. Properties of MOPS buffer: p𝐾a at 25∘C=7.15 Δp𝐾a/∘C=−0.013 absorbs light at <230 nm does not cross lipid bilayer All the properties fulfill the Good's buffer criteria.

p𝐾a at 25∘C=4.76 All the properties fulfill the Good's buffer criteria

Identify the applications for gel filtration chromatography. separation of components in a mixture by hydrophobicity separation of components in a mixture by size purification of a specific protein from a mixture estimation of molecular weights

separation of components in a mixture by size estimation of molecular weight

What are characteristics of RNA?

single-stranded ribose backbone contains the base uracil

In a typical monomeric protein, which level of structure is most likely conserved?

tertiary structure

Why does oil not dissolve in water? Oil molecules covalently bond together, forming droplets that separate from water. Oil is less dense than water, which causes it to separate from water instead of dissolving. Water molecules form hydrogen bonds with each other and exclude oil molecules. Water molecules form stronger associations with other polar molecules than with oil.

water molecules form hydrogen bonds with each other and exclude oil molecules Water molecules form stronger associations with other polar molecules than with oil

Which peptide segment is most likely to be a part of a stable a helix at physiological pH? −Glu−Glu−Glu−Glu−Glu− −Pro−Leu−Thr−Pro−Trp− −Gly−Gly−Gly−Ala−Gly− −Gly−Arg−Lys−His−Gly− −Tyr−Trp−Phe−Val−Ile− −Lys−Lys−Ala−Arg−Ser− −Glu−Leu−Ala−Lys−Phe−

−Glu−Leu−Ala−Lys−Phe−