Biochemistry: Hexose Sugars Overview
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Questions and Answers

Which pigments are known to be insoluble in water?

  • Phycobillins
  • Only chlorophylls
  • Both chlorophylls and carotenoids (correct)
  • Carotenoids

    • What percentage of solar energy is absorbed by the plant for photosynthesis?

  • 1% (correct)
  • 25%
  • 40%
  • 10%

    • What is the main source of light energy used in photosynthesis?

  • The Sun (correct)
  • The moon
  • Stars
  • Artificial lights

    • What range of wavelengths do photosynthetic pigments primarily absorb?

    <p>400-700 nm</p> Signup and view all the answers

    Which type of reaction occurs exclusively in the presence of lipids in chloroplast grains?

    <p>Light reaction</p> Signup and view all the answers

    Which pigment group includes carotenes and xanthophylls?

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

    What light property causes chloroplasts to appear green in plants?

    <p>Weak absorption in green light</p> Signup and view all the answers

    What are the two parts of the photosynthesis mechanism?

    <p>Light reaction and dark reaction</p> Signup and view all the answers

    What type of sugar is glucose classified as?

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

    Which of the following hexoses is formed during the digestion of sucrose?

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

    What is the molecular formula for both glucose and fructose?

    <p>C6H12O6</p> Signup and view all the answers

    Which disaccharide is commonly found in mammalian milk?

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

    Which type of bond links monosaccharides to form disaccharides?

    <p>Glycosidic bond</p> Signup and view all the answers

    Which hexose is predominantly found in circulating blood?

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

    What is the primary carbohydrate source for energy production in the body?

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

    Which of the following carbohydrates is not digestible by monogastric animals?

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

    What is the basic equation representing the process of photosynthesis?

    <p>6CO2 + 6H2O → C6H12O6 + 6O2</p> Signup and view all the answers

    Which scientist concluded that carbon dioxide and water are the raw materials for photosynthesis?

    <p>Jean Senebier</p> Signup and view all the answers

    Which of the following is NOT a necessary condition for photosynthesis?

    <p>Absence of water</p> Signup and view all the answers

    What role does light play in the process of photosynthesis?

    <p>It is converted into chemical energy.</p> Signup and view all the answers

    Who first suggested that plants restore CO2-laden air through a burning candle?

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

    What type of pigment is primarily responsible for photosynthesis in plants?

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

    Which of these describes photosynthesis in terms of energy transformation?

    <p>Light energy is converted into chemical energy.</p> Signup and view all the answers

    What is a primary benefit of photosynthesis to humans?

    <p>It directly provides food and oxygen.</p> Signup and view all the answers

    What is the first step of the Calvin cycle?

    <p>Carboxylation of ribulose 1,5-bisphosphate</p> Signup and view all the answers

    Which molecule is formed from the hydrolysis of the unstable 6-carbon compound in the Calvin cycle?

    <p>3-phosphoglyceric acid</p> Signup and view all the answers

    What is the key product of the reduction step in the Calvin cycle?

    <p>3-phosphoglyceraldehyde</p> Signup and view all the answers

    Which process is responsible for regenerating ribulose 1,5-bisphosphate in the Calvin cycle?

    <p>Diversion of 3-phosphoglyceraldehyde</p> Signup and view all the answers

    What type of pathway is the Calvin cycle also known as?

    <p>Photosynthetic carbon reduction pathway</p> Signup and view all the answers

    Which of the following is the first visible product of the Calvin cycle?

    <p>3-phosphoglyceric acid</p> Signup and view all the answers

    In what form is the energy stored during photosynthesis?

    <p>Chemical energy</p> Signup and view all the answers

    Which enzyme is involved in the conversion of fructose 1,6-bisphosphate to fructose 6-phosphate?

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

    What role does the imidazole ring play in histidine?

    <p>Binds hydrogen ions to regulate pH</p> Signup and view all the answers

    Which of the following amino acids are essential and contain a benzene ring?

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

    At which wavelengths do tyrosine and tryptophan strongly absorb ultraviolet light?

    <p>270-290 nm</p> Signup and view all the answers

    What is the primary use of ultraviolet light absorption at 280-290 nm in proteins?

    <p>To measure protein concentration</p> Signup and view all the answers

    Which amino acid can be converted into tyrosine by animals?

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

    Which amino acids contain small amounts in proteins besides the most common amino acids?

    <p>Lysine derivatives</p> Signup and view all the answers

    Which amino acid exhibits very little ultraviolet light absorption?

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

    What is the maximum percentage of unusual amino acids, like hydroxylysine, typically present in proteins?

    <p>1-2 percent</p> Signup and view all the answers

    Study Notes

    Photosynthesis Overview

    • Photosynthesis is the process by which green plants synthesize organic matter using light.
    • The general equation: 6CO2 + 6H2O → C6H12O6 + 6O2.
    • Light energy is converted into chemical energy, stored as carbohydrates, with oxygen as a byproduct.
    • CO2 and H2O are the primary raw materials; it is an anabolic process.

    Historical Contributions to Photosynthesis

    • Van Helmont (1648): Suggested tree growth primarily resulted from water.
    • Stephan Hales (1727): Identified air as a nutrition source for plants and emphasized the importance of sunlight.
    • Priestley (1772): Proposed that plants could restore oxygen in CO2-laden air.
    • Ingenhousz (1779): Discovered that only green parts of plants can purify air with sunlight.
    • Jean Senebier (1783): Noted that air-purifying activities depend on CO2 presence.
    • Nicolas Theodore de Saussure (1804): Concluded that CO2 and water are essential raw materials.
    • Meyer (1845): Recognized light's role as the energy source in photosynthesis.
    • Julius Sachs (1862): Demonstrated that photosynthesis occurs in chloroplasts, producing organic matter.

    Importance of Photosynthesis

    • Directly provides food for humans and indirectly via animal products (meat, milk).
    • Maintains atmospheric oxygen equilibrium.
    • Supplies energy resources (e.g., coal, oil, wood).

    Types of Photosynthetic Pigments

    • Chlorophylls: Main pigments for light absorption, insoluble in water.
    • Carotenoids: Includes carotenes and xanthophylls, also insoluble in water.
    • Phycobilins: Water-soluble pigments.
    • Different pigments absorb various wavelengths of light and exhibit unique absorption peaks.

    Light Energy Absorption

    • The sun is the primary energy source for photosynthesis.
    • Plants receive about 40% of total solar energy; the rest is absorbed or scattered.
    • Only a small portion of light is utilized by pigments, predominantly in the 400-700 nm range (Photosynthetically Active Radiation - PAR).
    • Chloroplasts appear green due to weak absorption of light in the green spectrum.

    Mechanisms of Photosynthesis

    • Involves two main reactions:
      • Primary light reaction (Hill's reaction).
      • Dark reaction (Calvin cycle, carbon fixation).

    Light Reaction (Hill's Reaction)

    • Occurs in the presence of lipids within chloroplasts.
    • Utilizes labeled carbon dioxide (^14CO2) to trace carbon assimilation pathways.
    • Results in the formation of products necessary for the Calvin cycle.

    Calvin Cycle (C3 Pathway)

    • Steps include:
      • Carboxylation: CO2 combines with ribulose 1,5-bisphosphate (RuBP) to form a 6-carbon compound, which then splits into 3-phosphoglyceric acid (3PGA).
      • Reduction: 3PGA is converted to 3-phosphoglyceraldehyde (G3P).
      • Formation of Hexose Sugar: Some G3P molecules convert into fructose 1,6-bisphosphate and then into hexose sugars like glucose and sucrose.
      • Regeneration of RuBP: Excess G3P is used to regenerate RuBP for the continuation of the cycle.

    Summary Points

    • The Calvin cycle highlights the photosynthetic carbon reduction (PCR) pathway, playing a crucial role in synthesizing carbohydrates in plants.
    • The cycle is also known as the Reductive Pentose Phosphate (RPP) cycle.

    Additional Notes on Sugars

    • Monosaccharides: Individual sugars (e.g., glucose, fructose) typically consist of 5 or 6 carbon atoms.
    • Disaccharides: Composed of two monosaccharides linked by a glycosidic bond, with examples including sucrose, lactose, and maltose.

    Questions for Review

    • Name four scientists who contributed to the study of photosynthesis.
    • Identify four necessary conditions for photosynthesis.
    • What is the main source of energy in photosynthesis?
    • Explain the two types of reactions involved in the mechanism of photosynthesis.

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    Description

    This quiz covers the essential characteristics of hexose sugars, focusing on glucose, fructose, galactose, and mannose. It delves into their structural classifications as aldoses and ketoses, highlighting their significance in animal tissues. Test your knowledge on monosaccharides and their properties.

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