Biochemistry: Carbohydrate Structures
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Questions and Answers

Which level of protein structure involves regular coils and folds formed by hydrogen bonds?

  • Secondary structure (correct)
  • Quaternary structure
  • Tertiary structure
  • Primary structure

    • What describes the tertiary structure of a protein?

  • It does not affect the protein's function.
  • It is formed by the sequence of amino acids.
  • It is determined by interactions among side chains (R groups). (correct)
  • It consists of multiple polypeptide chains.

    • What role does the sequence of amino acids play in protein structure?

  • It determines a protein’s three-dimensional structure. (correct)
  • It determines the protein's secondary structure only.
  • It influences the protein's solubility and stability.
  • It is irrelevant to the protein's function.

    • Why is the primary structure of a protein important?

    <p>It dictates the protein's final three-dimensional shape.</p> Signup and view all the answers

    What is the primary structure of a protein?

    <p>The unique sequence of amino acids.</p> Signup and view all the answers

    What type of bonds are primarily responsible for forming the secondary structures of proteins?

    <p>Hydrogen bonds</p> Signup and view all the answers

    Which statement best describes the tertiary structure of a protein?

    <p>It is determined by interactions between the R groups of amino acids.</p> Signup and view all the answers

    What is the composition of collagen?

    <p>Three polypeptide chains coiled like a rope</p> Signup and view all the answers

    Which of the following interactions is NOT involved in tertiary protein structure?

    <p>Peptide bonds</p> Signup and view all the answers

    What is the primary role of fats in the human body?

    <p>Energy storage</p> Signup and view all the answers

    What causes sickle-cell disease at the molecular level?

    <p>A single amino acid substitution in hemoglobin</p> Signup and view all the answers

    Which property of phospholipids allows them to form a bilayer in cell membranes?

    <p>Hydrophobic tails and hydrophilic heads</p> Signup and view all the answers

    What structure characterizes steroids?

    <p>Four fused carbon rings</p> Signup and view all the answers

    What role do enzymes play in biological processes?

    <p>Catalyze chemical reactions</p> Signup and view all the answers

    What is the monomer unit used to build proteins?

    <p>Amino acids</p> Signup and view all the answers

    Which of the following statements about polypeptides is true?

    <p>Polypeptides range in length from a few to more than a thousand amino acids.</p> Signup and view all the answers

    How do amino acids differ from one another?

    <p>By their variable side chains, or R groups</p> Signup and view all the answers

    What is the consequence of high cholesterol levels in the blood?

    <p>Increased risk of cardiovascular disease</p> Signup and view all the answers

    What type of reaction is involved in forming disaccharides from monosaccharides?

    <p>Dehydration synthesis reaction</p> Signup and view all the answers

    Which of the following is a storage polysaccharide found in animals?

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

    What distinguishes the structure of starch from cellulose?

    <p>Starch has alpha linkages, while cellulose has beta linkages.</p> Signup and view all the answers

    Which of the following statements about cellulose is correct?

    <p>Cellulose contributes to the structural integrity of plant cell walls.</p> Signup and view all the answers

    What is the main reason humans cannot digest cellulose?

    <p>Humans cannot break down the beta linkages in cellulose.</p> Signup and view all the answers

    What is a significant structural feature of cellulose compared to starch?

    <p>Cellulose can form microfibrils through hydrogen bonding.</p> Signup and view all the answers

    Which polysaccharide is composed of glucose monomers and has a storage function in plants?

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

    What relationship do many herbivores have with microbes regarding cellulose?

    <p>They rely on microbes to help digest cellulose.</p> Signup and view all the answers

    What is the term for the loss of a protein's native structure due to environmental factors?

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

    Which of the following proteins assists in the proper folding of other proteins?

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

    Which of the following is NOT a characteristic of nucleotides?

    <p>They are part of proteins</p> Signup and view all the answers

    What is the main role of messenger RNA (mRNA)?

    <p>Direct synthesis of proteins</p> Signup and view all the answers

    What structural feature describes the DNA double helix?

    <p>Antiparallel backbones</p> Signup and view all the answers

    Which of the following nitrogenous bases is found in RNA but not in DNA?

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

    Which method is NOT typically used to determine protein structure?

    <p>Ultraviolet spectroscopy</p> Signup and view all the answers

    What do genes primarily encode?

    <p>Protein synthesis information</p> Signup and view all the answers

    What is the role of the sugar-phosphate backbone in nucleic acids?

    <p>To provide structural support</p> Signup and view all the answers

    Which nitrogenous base pairs with adenine in RNA?

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

    Which of the following statements is true regarding polynucleotides?

    <p>They have a specific sequence of nucleotides.</p> Signup and view all the answers

    What is the unit of inheritance that programs the amino acid sequence of polypeptides?

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

    What common feature do both DNA and RNA share?

    <p>Both are composed of nucleotides.</p> Signup and view all the answers

    What term describes the pairing of nitrogenous bases in DNA?

    <p>Complementary base pairing</p> Signup and view all the answers

    Study Notes

    Dehydration Synthesis

    • Forms larger molecules from smaller monomers by removing water
    • Example: Glucose + Glucose = Maltose (disaccharide)

    Disaccharides

    • Two monosaccharides joined by a glycosidic linkage
    • Examples:
      • Maltose (Glucose + Glucose)
      • Sucrose (Glucose + Fructose)
      • Lactose (Glucose + Galactose)

    Polysaccharides

    • Polymers of sugars with storage and structural roles
    • Structure and function determined by:
      • Sugar monomers
      • Positions of glycosidic linkages

    Storage Polysaccharides

    • Starch (Plant):
      • Made of glucose monomers
      • Stored as granules in chloroplasts and other plastids
    • Glycogen (Animal):
      • Found in liver and muscles

    Structural Polysaccharides

    • Cellulose:
      • Major component of plant cell walls
      • Polymer of glucose with different glycosidic linkages than starch
      • Uses beta (β) glucose
    • Differences in glucose ring forms:
      • Alpha (α) glucose: helical polymers
      • Beta (β) glucose: straight polymers
    • Cellulose structure:
      • Straight structure allows hydrogen bonding between strands
      • Forms strong microfibrils for plant structure
    • Humans lack enzymes to digest beta (β) linkages in cellulose

    Lipids

    • Diverse group of hydrophobic molecules
    • Major functions:
      • Energy storage
      • Structural components of cell membranes

    Fats

    • Store energy for long-term use
    • Triglycerides composed of glycerol and three fatty acid tails
    • Adipose tissue stores fat in animals

    Phospholipids

    • Amphipathic molecules
    • Two fatty acid tails (hydrophobic) + phosphate group (hydrophilic)
    • Form bilayers in water to create cell membranes

    Steroids

    • Four fused ring structure
    • Cholesterol:
      • Important component of animal cell membranes
      • Can contribute to cardiovascular disease at high levels

    Proteins

    • Account for more than 50% of cell dry mass
    • Diverse functions:
      • Structural support
      • Storage
      • Transport
      • Cellular communications
      • Movement
      • Defense
    • Polymers of amino acids (polypeptides)

    Amino Acids

    • Monomers of proteins with:
      • Carboxyl group
      • Amino group
      • Central carbon
      • Variable side chain (R group)
    • 20 different amino acids due to different R groups

    Polypeptides

    • Unbranched polymers of amino acids
    • Covalent bonds between amino acids called peptide bonds
    • Unique linear sequence of amino acids
    • Have carboxyl end (C-terminus) and amino end (N-terminus)

    Protein Structure

    • Determines protein function
    • Four levels:
      • Primary: Sequence of amino acids
      • Secondary: Coils (alpha helices) and folds (beta pleated sheets) due to hydrogen bonding
      • Tertiary: Folding due to R group interactions (hydrogen bonds, ionic bonds, hydrophobic interactions, van der Waals interactions, disulfide bridges)
      • Quaternary: Multiple polypeptide chains forming one macromolecule

    Sickle-Cell Disease

    • Caused by a single amino acid substitution in hemoglobin protein
    • Affects protein structure and function

    Protein Folding

    • Chaperonins assist in proper protein folding
    • Misfolded proteins can cause diseases like Alzheimer's, Parkinson's, and mad cow disease

    Nucleic Acids

    • Store and transmit hereditary information
    • Two types:
      • Deoxyribonucleic acid (DNA)
      • Ribonucleic acid (RNA)

    DNA

    • Directs its own replication
    • Directs synthesis of messenger RNA (mRNA)
    • Controls protein synthesis

    RNA

    • Transports genetic information from DNA to ribosomes
    • Plays a role in protein synthesis

    Nucleotides

    • Monomers of nucleic acids
    • Components:
      • Nitrogenous base
      • Pentose sugar
      • Phosphate group
    • Nucleoside: Without phosphate group

    Nitrogenous Bases

    • Two families:
      • Pyrimidines: Cytosine (C), Thymine (T), Uracil (U)
      • Purines: Adenine (A), Guanine (G)

    DNA vs. RNA

    • DNA sugar: Deoxyribose
    • RNA sugar: Ribose
    • DNA bases: A, T, C, G
    • RNA bases: A, U, C, G

    Nucleic Acid Structure

    • Polynucleotides: Polymers of nucleotides
    • Covalent bonds between nucleotides form a sugar-phosphate backbone
    • Sequence of bases is unique for each gene

    DNA Structure

    • Double helix with two antiparallel polynucleotide strands
    • Complementary base pairing:
      • A with T (in DNA)
      • G with C
    • Hydrogen bonds between bases hold strands together

    RNA Structure

    • Usually single-stranded
    • A with U (in RNA)
    • G with C
    • Can form complementary base pairing with itself or other RNA molecules

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