Bio 148 Exam 3 Questions With All Correct Answers Verified Answers 2025 Marking Scheme New Update

Bio 148 Exam 3 Questions With All Correct Answers Verified Answers 2025 Marking Scheme New Update Which of the following is not attached to the central carbon atom in an amino acid? -An amino functional group -A side chain ("R group") -A carboxyl functional group -An oxygen - Answer- An oxygen (The central carbon atom in an amino acid is bonded to an amino functional group, a carboxyl functional group, a side chain, and hydrogen) Which part of an amino acid is always acidic? -Amino functional group -Carboxyl functional group -Side chain ("R group") -None of the above - Answer- Carboxyl functional group (The carboxyl group (COOH) contains two oxygen atoms that tend to pull electrons away from the hydrogen atom, so this group tends to lose a proton and is acidic) Which polymers are composed of amino acids? -Proteins -Carbohydrates -Monomers -Nucleic acid - Answer- Proteins (Proteins are composed of amino acids joined together) Which monomers make up RNA? -Amino acids -Nucleotides -Simple sugars -Polymers - Answer- Nucleotides (Nucleotide monomers make up nucleic acids.) Which of the following statements about the formation of polypeptides from amino acids is true? -The reaction occurs through the addition of a water molecule to the amino acids. -A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid. -A bond can form between any carbon and nitrogen atom in the two amino acids being joined. -Polypeptides form by condensation or hydrolysis reactions - Answer- A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid. (A hydroxyl group is removed from the carboxyl group of one amino acid and hydrogen is removed from the amino group of the other amino acid, allowing a bond to form between the two groups) True or false? Enzymes in the digestive tract catalyze hydrolysis reactions. - Answer- True (Enzymes in the digestive tract break down food molecules, which is a process that occurs by hydrolysis.) Proteins are polymers of _____. -nucleotides -glycerol -amino acids -hydrocarbons -CH2O units - Answer- Amino Acids (Proteins are polymers of amino acids.) What type of bond joins the monomers in a protein's primary structure? -hydrogen -hydrophobic -ionic -peptide -S - S - Answer- Peptide (The amino acids of a protein are linked by peptide bonds.) The secondary structure of a protein results from _____. -hydrogen bonds -peptide bonds -ionic bonds -hydrophobic interactions -bonds between sulfur atoms - Answer- Hydrogen bonds (Electronegative oxygen and nitrogen atoms leave hydrogen atoms with partial positive charges.) Tertiary structure is NOT directly dependent on _____. -hydrophobic interactions -bonds between sulfur atoms -hydrogen bonds -ionic bonds -peptide bonds - Answer- Peptide bonds (Peptide bonds link together the amino acids of a protein's primary structure.) ______ structure is the sequence of amino acids in a protein - Answer- primary ______ structure is the result of two or more protein subunits assembling to form a larger,biologically active protein complex. - Answer- quaternary ______ structure describes alpha helices and beta sheets that are formed by hydrogen bonding between backbone atoms located near each other in the polypeptide chain. - Answer- secondary ______ structure is achieved when a protein folds into a compact, 3-D shape stabilized by interactions between side chain R groups of amino acids. - Answer- tertiary What aspects of amino acid structure vary among different amino acids? --the long carbon-hydrogen tails of the molecule --the components of the R-group --the presence of a central C atom --the glycerol molecule that forms the backbone of the amino acid - Answer- the components of the R-group How does the structure of an amino acid enable it to play its most important roles in cells? --It can serve a wide variety of functions in a cell, because it contains the atoms most commonly found in organisms (C, H, N, and O). --The presence of carboxyl and amino groups gives it the ability to form peptide bonds, and its side chain gives it unique chemical properties. --Because both carboxyl and amino groups are present, polymerization is exergonic. In addition, the presence of a side chain makes the molecule water soluble. --Because each amino acid contains a variety of functional groups, they can participate in a wide variety of chemical reactions. - Answer- The presence of carboxyl and amino groups gives it the ability to form peptide bonds, and its side chain gives it unique chemical properties. Which of the following most accurately lists elements of any protein's primary, secondary, tertiary, and quaternary structure (in that order)? -one polypeptide chain, two polypeptide chains, three polypeptide chains, more than three polypeptide chains -amino acid sequence, hydrogen bonding between backbone atoms, overall shape of a single polypeptide, combinations of tertiary structures -amino acid sequence, hydrogen bonding between R groups, overall shape of a single polypeptide, multiple polypeptide subunits -covalent bonding, van der Waals interactions, hydrogen bonding, hydrophobic interactions - Answer- amino acid sequence, hydrogen bonding between backbone atoms, overall shape of a single polypeptide, combinations of tertiary structures You've just sequenced a new protein found in mice and observe that sulfur-containing cysteine residues occur at regular intervals. What is the significance of this finding? -Cysteine residues are required for the formation of α-helices and β-pleated sheets. -Cysteine causes bends, or angles, to occur in the tertiary structure of proteins. -Cysteine residues are involved in disulfide bridges that help form tertiary structure. -It will be important to include cysteine in the diet of the mice. - Answer- Cysteine residues are involved in disulfide bridges that help form tertiary structure. Aquaporins are proteins that control the passage of water molecules across the cell membrane. The protein forms a pore, or opening, in the membrane. You isolate what you think are two different molecules of aquaporin, and determine that one of the proteins has a larger pore diameter than the second. Which of the following do you conclude? -These two forms of aquaporin will have different sequences of amino acids. -These molecules both can't have aquaporin because all proteins that do the same type of job (such as catalyze a reaction) have the exact same 3-D structure. -These two forms of aquaporin will have identical sequences of amino acids. -You will have to sequence the proteins to compare their primary structure, because it should have no effect on pore diameter. - Answer- These two forms of aquaporin will have different sequences of amino acids Where does translation take place? -Golgi apparatus -Ribosome -Endoplasmic reticulum -Nucleus - Answer- ribosome (Translation, or protein synthesis, occurs at the ribosome.)