Download BCH210 Final Exam: Carbohydrates (Monosaccharides, Disaccharides, Polysaccharides) and more Exams Nursing in PDF only on Docsity!
Uoft 2025 Fall BCH210 Final exam Questions
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Monosaccharide formula correct answer: (CH2O)n (n is 3 or more) Aldotriose correct answer: Also known as glyceraldehyde, simplest aldehyde monosaccharide (n = 3), has L and D isomer (centre carbon is chiral) Ketotriose correct answer: Also known as dihydroxyacetone, simplest ketone monosaccharide (n = 3), non chiral Carbon numbering correct answer: Aldoses always have aldehyde and C1, ketoses have ketone at C Sugar naming correct answer: triose, tetrose, pentose, hexose, etc., l or d based on whether hydroxyl is right of chain (d) or left (l), last chiral carbon (furthest from carbonyl) denoted with L or D L isomer of a sugar correct answer: Last chiral carbon's hydroxyl is on the left D isomer of a sugar correct answer: Last chiral carbon's hydroxyl is on the right, found in body Number of stereoisomers in a linear monosaccharide correct answer: 2^(Number of chiral carbons), e.g. for an aldopentose,
3 chiral carbons so 8 isomers, for a ketopentose, 2 chiral carbons so 4 isomers. If including cyclic structures, there are 2 more or 4 more if it can form both 5 and 6 ring structures cyclic structures of monosaccharides correct answer: Prevalent form monosaccharides with 5 or 6 carbon atoms, form when the hydroxyl group on the last chiral carbon reacts with the aldehyde group or ketone group. Furan ring correct answer: 5 member ring with O formed by cyclization of a monosaccharide (cyclization of ketose usually). Can occur with tetroses (4 Cs + O from carbonyl) Pyran ring correct answer: 6 member ring with O formed by cyclization of monosaccharide (cyclization of aldose usually) Nucleophilic attack to cyclize sugars correct answer: Only occurs in water, electrons of hydroxyl group attack carbonyl, forming cyclic structure with the old hydroxide becoming an O in the ring and a new hydroxide formed (using the old hydroxide's H) either above/equatorial (beta) or below/axial (alpha) the plane of the structure - beta is more stable Anomeric Carbon correct answer: the new chiral center formed in ring closure; it was the carbon containing the carbonyl in the straight-chain form Anomers correct answer: Isomers that differ at a new asymmetric carbon atom formed on ring closure (e.g. alpha and beta)
hydroxide while the hydroxide in the ring forms a double bond with its carbon forming a ketone/aldehyde Disaccharides correct answer: Carbohydrates that are made up of two monosaccharides Oligosaccharides correct answer: 3-20 monosaccharides Polysaccharides correct answer: Up to 1000s monosaccharides Glycosylation correct answer: Process of covalently attaching a carbohydrate to a protein or lipid. Protein glycosylation assists in folding and cellular recognition Disaccharide formation correct answer: OH on C1 can react with hydroxyls on other sugars, e.g. OH on C4 can attack OH on C1, turning 2 hemiacetals into a full acetal. Condensation reaction because an H2O is lost hemiacetal correct answer: aldehyde + alcohol bond hemiketal correct answer: ketone + alcohol bond a(1-4) glycosidic bond correct answer: Bond between an alpha C1 (on the left sugar) and a C4 (on the right sugar). Alpha based on the orientation of the O on the left sugar's C O-glycosidic bond correct answer: Bond formed between the anomeric carbon atom and a hydroxyl group of another molecule (another sugar, amino acids Serine and Threonine, methanol)
N-glycosidic bond correct answer: A bond formed between the anomeric carbon atom and an amine (from amino acid Asparagine) Variable aspects of oligosaccharides correct answer: Amino acids (N/O linked amino acids), Sugar types/composition (Glu, Fru, Man, Lac), Sugar configurations (alpha, beta), linkages (1- 4, 1-6, 2-4 for ketoses). If chain, can differ by branched or unbranched Glycosyltransferase correct answer: Any of a number of specific enzymes that catalyze the formation of glycosidic bonds. Have specificity for certain sugars and can join them in the proper orientation and connectivity. Sugars must first be activated using UTP to create a high-energy sugar-nucleotide intermediate. Maltase correct answer: Cleaves alpha 1-4 bond between two glucose molecules via hydrolysis Lactase correct answer: Cleaves beta 1-4 bond between galactose and glucose via hydrolysis Glycogen correct answer: An extensively branched glucose storage polysaccharide found in the liver and muscle of animals. Contains branch points every 8-12 glucose units and covalently bound to a protein dimer glycogenin at the centre. Glucose units are added and removed from the non-reducing ends (anomeric carbon in glycosidic linkages). Contains 1-4 and some 1- glycosidic linkages at branch points
Hexokinase correct answer: Phosphorylates glucose to glucose- 6-phosphate, trapping it in the cytoplasm using ATP (occurs before glycogen synthesis and glycolysis). Inhibited by the buildup of its product, glucose 6-phosphate. Mg2+ cofactor + ATP bind away from glucose binding site. C6 hydroxyl attacks the γ phosphate producing Glucose 6-Phosphate. Glycolysis net equation correct answer: Glucose + 2 ADPs + 2 Pi + 2 NAD+ --> 2 Pyruvate + 2 ATP + 2 NADH + 2 H2O + H+ (number depends on pH) Phosphofructokinase (PFK-1) correct answer: Phosphorylates the C1 hydroxyl using ATP to form fructose-1-6-bisphosphate. Allosterically inhibited by ATP and citrate and stimulated by AMP, ADP or Fructose 2,6-bisphosphate (feed forward regulation). Induced fit model of binding correct answer: Most enzymes change shape upon binding their substrates - this induced fit then allows the reaction to proceed Fructose-2,6-BP correct answer: -synthesized by PFK-2 and broken down by FBPase- -allosteric modulator -regulates both glycolysis and gluconeogenesis
- it activates PFK-1, thus turns up/activates glycolysis and inhibits FBPase-1, inhibiting gluconeogenesis -regulated by insulin and Glucagon Pyruvate Kinase correct answer: Converts phosphoenolpyruvate (PEP, high energy molecule) to pyruvate. Stimulated by
Fructose 1-6-BP and AMP (feed forward regulation) and inhibited by ATP, Alanine, and Acetyl CoA. Also inhibited through phosphorylation: under low blood glucose GPCR signalling activates PKA which phosphorylates PK to slow glycolysis. Under high blood glucose, insulin signalling activates phosphatases to stimuate glycolysis. Glycogen synthesis correct answer: Glycogen synthase adds glucose onto non reducing ends, needs glycolysis to slow down phosphoglucomutase correct answer: converts glucose-1- phosphate to glucose-6-phosphate for glycogen synthesis UDP-glucose pyrophosphorylase correct answer: Uses UTP to activate Glucose 1-phosphate, producing UDP glucose and PPi glycogen synthase correct answer: catalyzes the transfer of glucose from UDP-glucose to a growing chain (C4 hydroxide of chain attacks anomeric carbon, producing glycosidic linkage and free UDP) Glycogen Breakdown correct answer: Epinephrine and glucagon signalling leads to the phosphorylation and activation of glycogen phosphorylase, which releases glucose 1-phosphate from non-reducing ends. Phosphoglucomutase converts it back to glucose-6-phosphate glycogen phosphorylase correct answer: Enzyme that cleaves glucose from the non-reducing end of a glycogen branch by phosphorylating it. Allosterically inhibited by ATP and Glucose 6-phosphate, and stimulated by AMP
E3 - Dihydrolipoamide dehydrogenase correct answer: Resets complex by reoxidizing lipoamide. Uses NAD+ to reset FADH to FAD+ making NADH. Inhibited by NADH PDC Covalent Modification correct answer: Phosphorylation of PDC E1 inactivates complex, done by PD kinase and undone by PD phosphatase (using H2O). PD Kinase and Phosphatase regulation correct answer: NADH and Acetyl CoA stimulate PD kinase, Pyruvate and ADP inhibit kinase (allosteric control), and Ca2+ stimulate phosphatase Citric Acid Cycle correct answer: Links the breakdown of fuel molecules to ATP Production in Oxidative Phosphorylation Why is the Citric Acid Cycle considered a 'cycle' and not a linear pathway? correct answer: Final product (oxaloacetate) becomes the substrate when it binds with Acetyl CoA. The route of the pathway and its regulation is dependent on the concentration of oxaloacetate Net reaction of CAC correct answer: Acetyl-CoA + 3NAD+ + FAD + GDP + Pi + 2H2O —> 2CO2 + 3NADH + FADH2 + GTP + CoA (+ 3 H+) Citrate Synthase correct answer: Oxaloacetate + Acetyl CoA --
Citrate, hydrolysis of thioester from CoA provides lots of
energy and drives cycle forward. Inhibited by ATP and NADH, stimulated by ADP and pyruvate Where do carbons in CO2s released in CAC originate? correct answer: Carbons that are released in the first half of CAC originate from oxaloacetate. Only at succinate intermediate in the pathway do we "lose track" of which carbons are old/new Isocitrate Dehydrogenase correct answer: isocitrate to alpha- ketoglutarate. First redox reaction: NAD+ to NADH and O double bond created, then decarboxylation using H+. Inhibited by ATP and NADH, activated by ADP and Ca2+ α-Ketoglutarate Dehydrogenase Complex correct answer: A complex of 3 subunits (E1/E2/E3) and 5 cofactors that converts a-ketoglutarate to succinyl-CoA. CO2 is released first by E1, followed by the production of NADH in E3. A thioester bond is created in Succinyl-CoA to help drive the next reaction. Inhibited by ATP, NADH, Succinyl CoA, activated by Ca2+ Succinate Dehydrogenase correct answer: Converts succinate to fumarate, also used in ETC as Complex II (embedded in inner mito membrane). Uses FAD and produces FADH2, which is immediately used in ETC (electrons passed in transport chain, regenerating FAD+) Mitochondrial Oxidative Phosphorylation correct answer: Protein complexes transport H+ across the inner mitochondrial membrane (into intermembrane space) during electron transport in a series of redox reactions, which creates a proton gradient
Oxidative Phosphorylation Inhibitors correct answer: Rotenone, Cyanide, Azide, CO, Oligomycin Rotenone and amytal correct answer: Inhibit electron flow from complex I to CoQ Antimycin A correct answer: Blocks Complex III Cyanide, azide and CO correct answer: inhibit complex IV Oligomycin correct answer: inhibits ATP synthase by preventing binding of protons to c subunits Uncouplers correct answer: disrupt the H+ gradient across the inner mitochondrial membrane and reduce ATP product but increase oxygen consumption. Have hydrophobic groups that allow them to cross the membrane and acidic groups can bind H+and move them from high to low concentrations Peter Mitchell's Chemiosmotic Hypothesis correct answer: ATP synthesis arises due to an electrochemical gradient across the mitochondrial inner membrane. ATP synthase is membrane- bound, reversible, and dependent on the proton gradient. ATP synthase correct answer: Large protein that uses energy from H+ ions to bind ADP and a phosphate group together to produce ATP. Contains F1 and F0 units. Protons flow through the rotor causing a rotation in the ring of c subunits of F0, which then causes a conformational change in the alpha and beta subunits of F1 via the gamma subunit/rotor shaft.
F1 unit of ATP synthase correct answer: Peripheral protein unit that carries out the catalytic synthesis of ATP in the matrix. Contains 3 beta subunits alternate with 3 alpha subunits (beta subunits synthesize ATP). Contains a stator to prevent rotation of alpha and beta subunits. Contains gamma subunit which induces conformational change in alpha and beta. F0 unit of ATP synthase correct answer: Integral membrane protein unit that anchors the enzyme complex in the inner mitochondrial membrane. Beta subunits of ATP synthase / Boyer's Binding Change Mechanism correct answer: 3 subunits which all function independently and there are 3 different reactions occurring simultaneously. Binding of H+ in the rotor (c subunit) rotates the gamma subunit and induces changes in beta subunits between three states:
- Open or Empty/exit (ATP leaves)
- Loose with ADP and Pi bound
- Tight with ATP bound Each subunit Reversibility of ATP synthase correct answer: ATP hydrolysis can also be used to reverse the rotation. This form of active transport that can be used to drive proton transport across the membrane in the opposite direction. Direction of rotation is opposite to that when making ATP Visualizing reversible ATP synthase correct answer: Recombinant fusion proteins: His-tag on beta subunits to visualize, fluorescently labelled actin filament
Overall summary equation for the complete oxidation of glucose correct answer: Glucose + 30 ADP + 30 Pi + 6O2 --> 6CO2 + 30ATP + 36H2O Anaerobic Metabolism correct answer: The metabolism that takes place in the absence of oxygen; the principle product is lactic acid. All energy production in the mitochondria shuts down, and the PDC & CAC also slow down (everything is stuck in reduced state because oxygen can't accept electrons). Lactate dehydrogenase correct answer: Uses NADH made in glycolysis in the cytoplasm to replenishing NAD+ for glycolysis to continue. Converts between pyruvate and lactate (reduces pyruvate to lactate, oxidizes NADH to NAD+). Lactate can be used by liver cells in GNG. Gluconeogenesis correct answer: Lactate, glycerol and certain amino acids can be turned into glucose in the liver and some kidney cells. Anabolic pathway that uses high energy intermediates and 4 different enzymes to bypass the 3 steps in glycolysis that have negative ΔGº ́ and are essentially irreversible. First few steps need to happen twice (3Cs in pyruvate, 6Cs in glucose) and require 4 ATP and 2 GTP. Cori Cycle correct answer: The removal and recycling of lactate by the liver. After lactate is produced in anaerobic metabolism, liver converts lactate to pyruvate (lactate dehydrogenase complex). Liver can also convert some amino acids into pyruvate. 2 Pyruvate used to produce Oxaloacetate, which can be used to supplement CAC or to produce glucose. Glucose can then be used to produce energy or to store it as glycogen.
Pyruvate carboxylase correct answer: Converts pyruvate to oxaloacetate through the addition of CO2 from bicarbonate, uses ATP. First step of GNG. Activated by Acetyl CoA, inhibited by ADP. PEP carboxykinase correct answer: Converts oxaloacetate to PEP through decarboxylation to help add a phosphate (uses GTP and energy released from decarboxylation). Produces PEP, GDP and CO2. Inhibited by ADP. Fructose-1,6-bisphosphatase correct answer: Fructose 1,6- bisphosphate to fructose 6-phosphate, reverses step 3 of glycolysis and produces a Pi. (uses H2O in hydrolysis reaction). Inhibited by Fructose 2,6, bisphosphate and AMP allosterically Glucose 6-phosphatase correct answer: Hydrolyzes glucose 6- phosphate to produce free glucose that can exit the cell. Used in GNG and glycogen breakdown Glucose Production from (2) Pyruvate correct answer: 2 Pyruvate + 4 ATP + 2 GTP + 2 NADH + 6 H2O + 2 H+ --> Glucose + 4 ADP + 2 GDP + 2 NAD+ + 6 Pi Glycerol to glucose production correct answer: Glycerol enters as dihydroxyacetone phosphate (DHAP). 2 glycerol are used along with 2 ATP and 2 H2O (to remove phosphates) in order to form 1 glucose molecule. 2 NADHs are also made. Glycolysis vs. GNG Regulation in Liver correct answer: Low energy activates glycolysis and inhibits GNG. High energy /
-> if we start w/ DHAP/GAP breakdown, divide everything by 2
- 1 NADH made per pyruvate in PDC (happens twice if starting with 6Cs)
- CAC (Happens twice if starting with 6Cs): In stage 1, 2 NADH made, -1 H2O (first step). In stage 2, 1 GTP, 1 NADH, 1 FADH2, -1H2O (fumarate, 1H2O used up earlier in CS step) in 2nd stage, but GTP is made in 1st rxn of 2nd stage (succinyl CoA -> succinate)-> breakdown of succinate or after will make NO GTPs When is NADH/FADH2 produced? correct answer: - Glycolysis step 6 (2 per glucose)* becomes FADH in mitochondria
- PDH (2 per glucose)
- CAC NADH: Isocitrate dehydrogenase, alphaketoglutarate dehydrogenase complex, malate dehydrogenase (3 per cycle, 6 per glucose)
- CAC FADH2: Succinate dehydrogenase (1 per cycle, 2 per glucose) Total per glucose in oxidative phosphorylation: 8 NADH, 4 FADH When is H2O produced/used? correct answer: - Glycolysis: 2 H2O per glucose
- CAC: 1 used in step 1, 1 used in step 7 (-2 per cycle, -4 per glucose)
- ETC/ATP synthase: 3.5 made per NADH, 2.5 per FADH (in regular cycle = 38)
Total per glucose after glycolysis, CAC, ETC, and ATP synthase: 36 H2O When is ATP/GTP produced/used? correct answer: - Glycolysis: 2 used in steps 1 and 3, produced in step 7 and 10 ( in each step, 4 total per glucose) --> net 2 per glucose
- CAC: GTP produced (1 per cycle, 2 per glucose) in step 5
- ETC/ATP synthase: 2.5 made per NADH, 1.5 per FADH Total per glucose after glycolysis, CAC, ETC, and ATP synthase: 30 ATP Triacylglycerol correct answer: A lipid consisting of three fatty acids linked to one glycerol molecule; also called a fat or triglyceride. Fat cell hormone signalling correct answer: Epinephrine and glucagon signal via GPCRs to activate triglycerol lipase/hormone sensitive lipase (HSL) (phosphorylation via PKA) triacylglycerol lipase / hormone sensitive lipase (HSL) correct answer: Hydrolyzes ester bonds on TAGs producing free fatty acids (ususally 16:0). Hydrolyzes one ester bond at a time (used 3 times to break down one TAG). Phosphorylated + activated by PKA glucagon/epinephrine (GPCR) signalling albumin correct answer: Protein that can carry free fatty acids through the blood. Can bring FFAs to all cells (except brain) for beta oxidation
