Carbohydrates and Photosynthesis Quiz
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Questions and Answers

What distinguishes D-glyceraldehyde from L-glyceraldehyde?

  • The number of carbon atoms in the molecule
  • The length of the carbon chain
  • The presence of a ketone group
  • The configuration of groups around the chiral carbon 2 (correct)

    • Which carbohydrate is a disaccharide composed of two glucose units?

  • Sucrose
  • Fructose
  • Maltose (correct)
  • Amylose

    • What is the significance of D-enantiomers in naturally occurring saccharides?

  • They are nonsuperimposable mirror images of their L counterparts (correct)
  • They are the only forms found in nature
  • They are more stable than L-enantiomers
  • They are the most frequently synthesized

    • In a Fischer projection, which type of bonds are represented horizontally?

    <p>Bonds that come towards the observer</p> Signup and view all the answers

    During the energy cycle of life, what do plants release as a byproduct of photosynthesis?

    <p>Oxygen</p> Signup and view all the answers

    Which of the following statements about the R–S nomenclature is correct?

    <p>The configuration is termed R when priority decreases clockwise.</p> Signup and view all the answers

    What distinguishes diastereomers from enantiomers?

    <p>Enantiomers are mirror images, while diastereomers are not necessarily so.</p> Signup and view all the answers

    In the context of carbohydrate chemistry, which group has the highest priority according to the provided ranking?

    <p>SH</p> Signup and view all the answers

    Which statement about the anomeric carbon in cyclic saccharides is accurate?

    <p>The anomeric carbon is derived from the carbonyl position in the linear form.</p> Signup and view all the answers

    Which of the following describes the ring forms of monosaccharides with five or more carbons?

    <p>They can form either five-membered or six-membered rings.</p> Signup and view all the answers

    What does the prefix D or L signify when referring to monosaccharides?

    <p>It specifies the absolute configuration of the farthest chiral carbon from the carbonyl.</p> Signup and view all the answers

    In the context of ribofuranose conformations, which statement is true?

    <p>C-2 endo conformation has C-2 above the plane.</p> Signup and view all the answers

    What defines the primary difference between sucrose and maltose?

    <p>The types of mono-sugar units are different.</p> Signup and view all the answers

    In disaccharides, which carbon linkage is characteristic of lactose?

    <p>1→4</p> Signup and view all the answers

    What is a distinguishing feature of lactose when compared to sucrose?

    <p>Lactose has a potential free aldehyde group.</p> Signup and view all the answers

    Which of the following correctly describes the configuration at the anomeric carbon in a glycosidic bond?

    <p>The configuration can be either α or β.</p> Signup and view all the answers

    Which statement about the sequence of disaccharides is true?

    <p>The sequence is important for determining enzymatic action.</p> Signup and view all the answers

    What is the characteristic feature of trehalose compared to other disaccharides?

    <p>It has a 1→1 glycosidic linkage.</p> Signup and view all the answers

    Which of the following disaccharides does not have an anomeric carbon capable of forming a free aldehyde group?

    <p>Sucrose</p> Signup and view all the answers

    What is a significant aspect of the stereoconfiguration of sugar monomers in disaccharides?

    <p>The configuration impacts how enzymes recognize and act on the sugars.</p> Signup and view all the answers

    Which of the following correctly designates the ring configuration of a sugar monomer in a disaccharide?

    <p>p for pyranose.</p> Signup and view all the answers

    What distinguishes conformational isomers from configurational isomers?

    <p>Conformational isomers can interconvert without breaking and re-forming bonds.</p> Signup and view all the answers

    Which of the following statements about aldonic acids is correct?

    <p>Aldonic acids are produced through mild oxidation of aldoses.</p> Signup and view all the answers

    What are uronic acids primarily characterized by?

    <p>They involve oxidation at carbon 6 of aldoses.</p> Signup and view all the answers

    Which compound is categorized as an alditol?

    <p>Sorbitol</p> Signup and view all the answers

    What is the primary function of sugar phosphates in metabolism?

    <p>They serve as intermediates in metabolic reactions.</p> Signup and view all the answers

    Which statement best explains how glycosidic bonds are formed?

    <p>By elimination of water between an anomeric hydroxyl and another hydroxyl.</p> Signup and view all the answers

    Which of the following describes how epimers differ?

    <p>They differ in configuration about only one asymmetric carbon atom.</p> Signup and view all the answers

    Which statement correctly describes the stability of chair and boat conformations of hexoses?

    <p>Chair conformations are usually more stable than boat conformations.</p> Signup and view all the answers

    What are some common naturally occurring glycosides known for their toxicity?

    <p>Ouabain and amygdalin</p> Signup and view all the answers

    Study Notes

    Biochemistry I - CHM219

    • Course Instructor: Dr. Esra Aydemir
    • Course Title: Biochemistry I
    • Course Number: CHM219

    Carbohydrates: Sugars, Saccharides, Glycans

    • Carbohydrates have diverse functions in biochemistry, including generating and storing biological energy, molecular recognition (immune system), cellular protection, cell signaling, cell adhesion, biological lubrication, control of protein trafficking, and maintaining biological structure (cellulose).
    • Monosaccharides are the simplest carbohydrates composed of carbon, hydrogen, and oxygen.
    • Representative carbohydrates include glucose (monosaccharide), maltose (disaccharide with two glucose units), and amylose (a glucose polymer found in starch).
    • Aldoses and ketoses are types of monosaccharides distinguished by the position of the carbonyl group (aldehyde vs. ketone).
    • Trioses are the simplest monosaccharides.
    • Monosaccharides with 5 or more carbons exist as rings (furanoses, pyranoses) in solutions under physiological conditions.
    • Monosaccharides have a- and b-anomers.
    • The R-S system describes absolute stereochemical configurations in carbohydrates.
    • Common priorities for groups in carbohydrate chemistry are: SH, OR, OH, NH2, CO2H, CHO, CH2OH, CH3, H.
    • Enantiomers are nonsuperimposable mirror images, and the D-enantiomers are most prevalent in nature.
    • Important monosaccharides include trioses, tetroses, pentoses, and hexoses.
    • Glucose, fructose, galactose, and mannose are hexoses.
    • Ribose and deoxyribose are pentoses.
    • Monosaccharides can be oxidized, producing aldonic acids, uronic acids, or lactones.
    • Examples include aldonic acids (e.g., gluconic acid), uronic acids (e.g., glucuronic acid), and lactones.
    • Alditols are formed by reduction of the carbonyl group of a sugar.

    Oligosaccharides

    • Ouabain and amygdalin are toxic glycosides found in plants.
    • Disaccharides are formed by glycosidic bonds between two monosaccharides; examples include sucrose, lactose, maltose, cellobiose, and gentiobiose. Key features of distinguishing disaccharides include the monomers' involved and their configurations, the carbons they involve in the linkage, their order, and anomeric hydroxyl group configuration.

    Glycoproteins

    • Oligosaccharides and proteins are linked to form glycoproteins in two ways: O-linked (via threonine or serine) and N-linked (via asparagine)
    • The ABO blood group antigens are formed by the addition of GalNAc or Gal to the O oligosaccharide and elicit specific antibodies.

    Polysaccharides

    • Starch (amylose and amylopectin) and glycogen are storage polysaccharides in plants and animals, respectively.
    • Cellulose is a structural polysaccharide.
    • Other important structural polysaccharides include chitin and glycosaminoglycans (e.g., chondroitin sulfates, keratan sulfates, dermatan sulfates, hyaluronic acid).

    Specific Considerations

    • Heparin, a highly sulfated glycosaminoglycan, is a natural anticoagulant.
    • Bacteria exhibit cell walls composed of peptidoglycan, a complex of structural polysaccharides and peptides. Gram-positive and Gram-negative bacteria differ in the structure of their cell walls.
    • Lipoteichoic acids are found embedded in the cell walls of Gram-positive bacteria.

    Biosynthesis of Glycoconjugates

    • Activated sugar molecules (like UDP-galactose and UDP-N-acetylglucosamine) are essential for their synthesis.
    • Glycoproteins are important in cell-cell recognition and signaling.

    Other Concepts

    • The structure of the influenza virus includes a genome contained inside a sphere.
    • Neuraminidase inhibitors, like zanamivir and oseltamivir, can block viral activity.

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    Biochemistry I CHM219 Fall 2021 Lecture Notes PDF

    Description

    Test your knowledge on the distinctions between D- and L-glyceraldehyde, the composition of disaccharides, and the role of D-enantiomers in saccharides. Additionally, challenge your understanding of Fischer projections and the byproducts of photosynthesis in plants.

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