Biochemistry and Molecular Biology Study Notes, Exams of Biology

Download Biochemistry and Molecular Biology Study Notes and more Exams Biology in PDF only on Docsity! BIOL 1P91 Fin al Exam Questions with Verified Solutions 2024 Update. What are the 3 general components that make up an atom? - Correct answer Protons Neutrons Electrons The sum of the atomic number and the number of neutrons is: - Correct answer A (the atomic number) Mass Number Which of the following is/ are a polar bond? A) O-H bond in water * B) C-O in CO2 C) N-N in N2 D) all of the above E) two of the above - Correct answer A) O-H bond in water A substance dissolvable in oil is said to be: - Correct answer Hydrophobic - since oil is hydrophobic, it will dissolve hydrophobic substances - like dissolves like Amphipathic molecules have two different properties: When dissolved in water, they form: - Correct answer Amphipathic molecules have hydrophobic and hydrophilic properties and in water they form micelles. A pH of 2 is ________ than a pH of 6 - Correct answer 10,000 times more acidic -more acidic the lower you go Which of the following macromolecules is the most hydrophobic? A) Lipids B) Proteins C) Carbohydrates D) Nucleic Acids E) All of the above F) 2 of the above - Correct answer Lipids are the most hydrophobic - water hating What is the following reaction? R1-OH + H-R2 --> R1-R2 + H20 A) Hydrolysis B) Condensation C) Dehydration D) Decomposition E) All of the above F) 2 of the above - Correct answer Two of the above: Hydrolysis and Condensation - they both lose a water to combine molecules What are the 4 molecules in all living organisms - Correct answer Hydrogen Oxygen Nitrogen Carbon Which macromolecule contains a sulphydryl functional group? A) Fatty acids B) Carbohydrates C) Steroids D) Amino acid - Correct answer Amino Acids - this is a -SH group that is specifically found in cysteine What kind of bonds connect sugar monomers - Correct answer Glycosidic bonds How do plants store energy? - Correct answer Starch - starch is for plants - glycogen is for animals Which protein structure involves the formation of a 3D shape due to R-group interactions? - Correct answer Tertiary What are the three types of movement across a membrane? - Correct answer -Diffusion (passive transport down the concentration gradient) - Facilitated Transport ( movement down a concentration gradient using a protein) -Active Transport (movement against the concentration gradient without the input of energy and the aid of a protein) The protein that moves lipids from the outer leaflet to the inner leaflet of the membrane - Correct answer Flippase - Scramblase (Random) - Flippase (Out to in) -Floppase (In to out) What type of proteins span the liquid membrane? - Correct answer Transmembrane Proteins If a red blood cell is thrown into a hypertonic solution what would happen? - Correct answer The cell will shrivel Which two reduced cofactors supply electrons to the electron transport chain in the Inner Mitochondrial Membrane? A) H2O and electrons B) ATPase and H+ C) NADH2 and FADH D) NADH and FADH2 - Correct answer NADH and FADH2 What is the name of the enzyme that couple the proton motive force to ATP synthesis in the inner mitochondrial membrane? - Correct answer ATP Synthase How many gross ATP are made in glycolysis by transferring 1 molecule of glucose into 2 pyruvate molecules? - Correct answer 4 are made The answer is 4 ATP, but remember that 2 ATP are consumed in the "Energy Investment Stage" prior to the "Energy Harvesting Stage" so the net amount of ATP produced from splitting one molecule of glucose into 2 pyruvate is 2 ATP (very low compared to OXPHOS (about 32 ATP are made). Enzymes lower: - Correct answer The activation energy of the reaction A competitive inhibitor will bind to the ________ of an enzyme - Correct answer Active Site Remember that a competitive inhibitor competes with the substrate for the active site of an enzyme. Also, remember that non-competitive inhibition is when the inhibitor inhibits the enzymatic reaction whether or not the substrate is bound to it. It can bind to a site other than the active site (ie. allosteric site). What is a heterotroph and give an example. - Correct answer Use organic molecules for energy an example being a lion Heterotrophs must eat food (organic molecules) as an energy source to sustain life. This includes animals, most fungi, some bacteria and archaea. Plants are autotrophs, organisms capable of using inorganic molecules or light as an energy source to synthesize organic molecules. What are the major products of the light reactions of photosynthesis? - Correct answer NADPH, ATP, Oxygen The light reactions of photosynthesis produce oxygen when water is broken down at the start of the light reactions. NADP+ is reduced to NADPH during electron chain reactions in the thylakoid membrane, which end in the production of ATP from ATP synthase. Where do the light reactions and dark reactions of photosynthesis take place? - Correct answer Light Reactions = Thylakoid Membrane Dark Reactions = Chloroplast stroma Light reactions of photosynthesis occur in the thylakoid membrane where electron transport proteins are present to aid in the production of oxygen, ATP and NADPH. The Calvin cycle occurs in the chloroplast stroma where carbon dioxide, ATP and NADPH are used to make carbohydrates like sugars. Which reactions produce NADPH? A) Krebs cycle B) Calvin cycle C) A and B D) None of the above - Correct answer None of the above Only the light reactions of photosynthesis produce NADPH. The Calvin cycle oxidizes NADPH to make carbohydrates. The Krebs cycle produces NADH, not NADPH. Choose the correct pairing of a protein complex in the thylakoid membrane and its function. A) Photosystem II; absorb light and oxidize water into oxygen B) Photosystem I; reflect light C) ATP Synthase; hydrolyze ATP D) NADP+ reductase; oxidize NADPH - Correct answer Photosystem II; absorb light and oxidize water into oxygen Both photosystems absorb light and use the light to increase the energy level of electrons. Only photosystem II has the ability to split water into H+ and oxygen. NADP+ reductase reduces NADP+. ATP synthase creates ATP from ADP using the energy of the H+ gradient across the thylakoid membrane. During non-cyclic electron flow in the light reactions, the high-energy electron from P680 A) Eventually moves to NADP+ B) Becomes incorporated in water molecules C) Is pumped into the thylakoid space to drive ATP production D) Provides the energy necessary to split water molecules E) Falls back to the low-energy state in photosystem II - Correct answer Eventually moves to NADP+ The final acceptor of electrons in linear electron flow is NADP+, which is reduced to form NADPH. Water is not a product of photosynthesis. Protons are pumped into the thylakoid space as a gradient for ATP production, not electrons. Light provides the energy necessary to split water molecules in photosystem II. Why do we perceive plant leaves to be green? - Correct answer Photosynthetic pigments in the leaves reflect green wavelengths of light. When light strikes a pigment, some of the wavelengths of light energy are absorbed, while others are reflected. We perceive that leaves are green because they are reflecting radiant energy of the green wavelength. At the extremes of colour reflections are white and black. A white object reflects nearly all of the light energy falling on it, whereas a black object absorbs nearly all of the light energy. What is the role of Rubisco in the Calvin Cycle? - Correct answer To incorporate carbon dioxide into ribulose bisphosphate Rubisco is the most abundant protein on Earth and is found inside chloroplasts. It serves to add carbon dioxide molecules to ribulose phosphate (an important 5 carbon molecule). This step is referred to as carbon fixation. What molecule does photosystem II split in the light reactions to produce oxygen? - Correct answer H2O Water (H2O) is split by photosystem II to produce H+ and oxygen. Light A) Travels only as a wave B) Travels only as a particle C) Travels as a wave and a particle in discrete packets called photons D) Is used by heterotrophs for energy E) Wavelengths of every size are absorbed by chlorophyll - Correct answer Travels as a wave and a particle in discrete packets called photons. Light consists of discrete quanta called photons. Photons are absorbed by photoautotrophs and used to sustain life. Which is true of oxidative phosphorylation? A) Occurs in the mitochondrial matrix B) Involves chemiosmosis, synthesis of ATP when H+ moves down its gradient C) Transport of electrons in the electron transport chain breaks down the H+ gradient D) NADH is the only molecule that can donate electrons to the electron transport chain E) H+ are the final electron acceptor - Correct answer Involves chemiosmosis, synthesis of ATP when H+ moves down its gradient. In the final steps of cellular respiration, ATP is synthesized when protons move down the concentration gradient established by the electron transport chain. They move through ATP synthase into the cytoplasm, releasing energy as they move down their gradient. ATP synthase harnesses this energy to make ATP from ADP. E) The start codon defines the reading frame. - Correct answer The start codon is usually GGA. The start codon is usually AUG (methionine), GGA codes for the amino acid glycine. Which of the following is not true of stop codons? A) The stop codons are also called termination codons B) The stop codons are also called nonsense codons C) UAA, UAG, UGA are all common stop codons D) The stop codons code for specific amino acids E) The stop codon is followed by the untranslated 3' tail - Correct answer The stop codons code for specific amino acids The stop codons do not code for amino acids, they signal the end of translation. During translation, chain elongation continues until what happens? - Correct answer A stop codon is encountered The stop codon signals the end of translation, the chain will continue growing until the terminator is reached. The term N-terminus refers to the presence of a(n) ___ at the 5' end of a polypeptide. - Correct answer Amino group The synthesis of a polypeptide occurs during which stage of translation? - Correct answer Elongation Splicing occurs during the alterations of the pre- mRNA, initiation and termination begin and end the synthesis respectively. The movement of the polypeptide from the tRNA in the P site to the tRNA in the A site is referred to as what? - Correct answer Peptidyl Transfer Reaction Peptide bonding occurs between the amino acids on the chain, peptidyl transfer reaction is the name given to the process of moving the codon through the ribosomal subunit. During the initiation step of translation, the first codon, ____, will enter the _____ and associate with the initiator tRNA. - Correct answer AUG, P site AUG is the start codon. In initiation, the first codon enters the P site, then the consecutive ones go through the A site for preparation, the strand then exits through the E site. The region of the tRNA that is complementary to the triplet on the mRNA is: - Correct answer The anticodon The _______ is the organelle where the translation process takes place: - Correct answer Ribosome Ribozymes are; - Correct answer RNA molecules that catalyze chemical reactions. Ribozymes function as enzymes of the ribosome, enzymes are capable of catalyzing reactions. Which of the following DNA mutations is the most likely to be damaging to the protein it specifies? A) a base-pair deletion B) a codon substitution C) a substitution in the last base of a codon D) a codon deletion E) a point mutation - Correct answer a base-pair deletion Deletions are the most detrimental type of mutation, a codon deletion has less affect than a basepair deletion. Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein? A) a base substitution B) a base deletion near the start of a gene C) a base deletion near the end of the coding sequence, but not in the terminator codon D) deletion of three bases near the start of the coding sequence, but not in the initiator codon E) a base insertion near the end of the coding sequence, but not in the terminator codon - Correct answer a base deletion near the start of a gene Deletions close to the start codon can affect the way the entire strand is read. A deletion of three base pairs would erase a whole codon, so only one amino acid would be affected. When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate? - Correct answer an assembled ribosome with a polypeptide attached to the tRNA in the P site Which of the following is the first event to take place in translation in eukaryotes? A) elongation of the polypeptide B) base pairing of activated methionine-tRNA to AUG of the messenger RNA C) binding of the larger ribosomal subunit to smaller ribosomal subunits D) covalent bonding between the first two amino acids E) the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA - Correct answer the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA Hemophilia is an X-linked recessive disorder. If a mother with hemophilia decides to have a child with a normal man, what is the likelihood that the child will have hemophilia? - Correct answer 50% In humans, which one of the following adheres to maternal inheritance: A) Hair colour B) Eye colour C) Blood type D) Mitrochondrial genome - Correct answer Mitrochondrial genome A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism? - Correct answer HT Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (I). What fraction of the progeny of the cross BbTt x BBtt will have black fur and long tails? - Correct answer ½ If a man with the blood type AB has children with a woman with the blood type O, what is the probability that their children will have the blood type A? - Correct answer 50% Both Susan and her daughter have the blood type AB. Susan is unsure whether Bob or Carl is the father of her child. Bob has the blood type O while Carl has the blood type A. Who is the father? - Correct answer Carl What is the main function of Helicase? - Correct answer Uses the hydrolysis of ATP to "unzip" or unwind the DNA helix at the replication fork to allow the resulting single strands to be copied. What is the main function of DNA polymerase 1? - Correct answer synthesizing nucleotides onto primers on the lagging strand, forming Okazaki fragments. However, this enzyme cannot completely synthesize all of the nucleotides. What is the main function of Topoisomerase? - Correct answer This enzyme introduces a single-strand nick in the DNA, enabling it to swivel and thereby relieve the accumulated winding strain generated during unwinding of the double helix. What is the main function of Ligase? - Correct answer This enzyme is in charge of "gluing" together Okazaki fragments, an area that DNA Pol I is unable to synthesize.