Biochemistry: Lipids and Carbohydrates Quiz
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Questions and Answers

What happens during the emulsion test for lipids?

  • Lipids turn the water transparent
  • Lipids float to the bottom of the solution
  • A milky emulsion forms if lipids are present (correct)
  • Lipids dissolve completely in water

    • Sudan III is a water-soluble dye used to identify lipids.

    False

    What is the primary function of starch in plants?

  • Water transport
  • Photosynthesis
  • Structural support
  • Food and energy storage (correct)

    • What is formed when a peptide bond is created between two amino acids?

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

    Glycogen is a storage polysaccharide that is found chiefly in plants.

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

    The ___ structure of proteins includes alpha-helices and beta-pleated sheets.

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

    What are the two main components of starch?

    <p>Amylose and amylopectin</p> Signup and view all the answers

    Glycogen is primarily stored in the liver and ______ in vertebrates.

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

    Which of the following amino acids is considered an S-containing R group example?

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

    Match the following terms with their descriptions:

    <p>Primary structure = Sequence of amino acids Tertiary structure = Overall 3D shape formed by interactions of R groups Quaternary structure = Combination of more than one polypeptide chain Fibrous proteins = Have structural roles</p> Signup and view all the answers

    Which type of linkage is found in amylose?

    <p>α-(1,4) glycosidic linkages</p> Signup and view all the answers

    Globular proteins primarily serve structural roles in the cell.

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

    Starch contributes to osmotic pressure inside plant cells.

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

    What is the storage organelle in plant cells that stores starch called?

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

    What is the role of lipoproteins in the body?

    <p>Transport lipids in the bloodstream</p> Signup and view all the answers

    Match the following types of polysaccharides with their properties:

    <p>Starch = Major fuel store in plants Glycogen = Storage polysaccharide in animals Amylose = Long, unbranched chains Amylopectin = Branched structure</p> Signup and view all the answers

    What term describes reactions that require energy to initiate?

    <p>Endergonic reactions</p> Signup and view all the answers

    Enzymes are consumed during the chemical reactions they catalyze.

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

    What is the active site of an enzyme?

    <p>The active site is the region of an enzyme that comes into direct contact with the substrate.</p> Signup and view all the answers

    During metabolism, breakdown reactions are called ______.

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

    Which hypothesis suggests that the enzyme's structure fits perfectly with the substrate?

    <p>Lock and key hypothesis</p> Signup and view all the answers

    Match the following enzyme functions with their definitions:

    <p>Catabolic = Involved in breakdown of molecules Anabolic = Involved in the synthesis of molecules Biological catalysts = Substances that speed up reactions without being consumed Activation energy = Energy required to start a reaction</p> Signup and view all the answers

    Most enzymes are smaller than the substrates they act upon.

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

    How do enzymes affect the activation energy of a reaction?

    <p>Enzymes reduce the activation energy required for the reaction to occur.</p> Signup and view all the answers

    What happens to enzyme reactions as the temperature increases up to the optimum temperature?

    <p>The reaction rate speeds up.</p> Signup and view all the answers

    What type of bond is primarily responsible for stabilizing secondary protein structures?

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

    Enzymes are not affected by changes in pH.

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

    The R groups of amino acids interact in the secondary structure to maintain protein shape.

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

    What is the effect of a temperature increase of 10°C on the rate of an enzyme-controlled reaction with a Q10 coefficient of 2?

    <p>The rate of reaction doubles.</p> Signup and view all the answers

    Enzymes can be denatured if the ___ or ___ is extreme.

    <p>temperature, pH</p> Signup and view all the answers

    Name one type of secondary structure formed in proteins.

    <p>α-helix or β-pleated sheet</p> Signup and view all the answers

    In a peptide bond, the carboxyl group retains a –C=O and the amino group retains a _______ group.

    <p>–N-H</p> Signup and view all the answers

    Match the protein structure with its description:

    <p>α-helix = A coiled structure stabilized by hydrogen bonds β-pleated sheet = A sheet-like structure with chains lying side by side keratin = A protein known for its coiled structure silk = A protein that resembles a β-pleated sheet</p> Signup and view all the answers

    What occurs after the enzyme's temperature exceeds its optimum?

    <p>The enzyme starts to denature.</p> Signup and view all the answers

    Increased kinetic energy always enhances enzyme activity.

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

    Which amino acids' groups are involved in the formation of hydrogen bonds in secondary structures?

    <p>Carboxyl and amino groups</p> Signup and view all the answers

    The secondary structure of proteins is solely determined by the sequence of amino acids.

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

    What type of bonds can break, causing an enzyme to denature?

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

    What is the role of hydrogen bonds in forming an α-helix?

    <p>To stabilize the turns of the coil</p> Signup and view all the answers

    What are the main functions of nucleotides?

    <p>Information storage, protein synthesis, and energy transfers</p> Signup and view all the answers

    All nucleotides have the same nitrogenous bases.

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

    What forms when a sugar combines with a nitrogenous base?

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

    The sugar in nucleotides can either be __________ or __________.

    <p>ribose, deoxyribose</p> Signup and view all the answers

    Match the following components with their descriptions:

    <p>Adenine = Purine Cytosine = Pyrimidine Thymine = Pyrimidine Guanine = Purine Uracil = Pyrimidine</p> Signup and view all the answers

    Which of the following best describes a dinucleotide?

    <p>Two nucleotides joined by a phosphodiester bond</p> Signup and view all the answers

    The sugar-phosphate backbone of DNA is located on the inside of the double helix.

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

    What kind of bond is formed between nucleotides to create a polynucleotide?

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

    Study Notes

    Biochemistry (Basic Molecules and Enzymes)

    • Syllabus Section 2: The Biomolecules of Life
      • Focuses on carbohydrates, lipids, proteins, and nucleic acids
      • Includes diagrams of molecular structures for each class.

    Basic Chemistry

    • Matter: Anything that takes up space and has mass
    • Elements: Substances that cannot be broken down into substances with different properties
      • Common elements in living organisms: carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur
    • Atoms: The smallest units of a substance
      • Composed of a nucleus (protons and neutrons) and orbiting electrons
      • Protons: Positive charge
      • Neutrons: No charge
      • Electrons: Negative charge
    • Atomic Number (Z): The number of protons in an atom's nucleus, equal to the number of electrons in a neutral atom
    • Mass Number (A): The total number of protons and neutrons in an atom's nucleus
    • Isotopes: Atoms of the same element with different numbers of neutrons
    • Electron Shells: Energy levels around the nucleus where electrons orbit
      • First shell: Holds up to 2 electrons
      • Second shell: Holds up to 8 electrons
      • Third shell: Holds up to 8 electrons (can hold more under specific conditions)
    • Chemical Bonds: Forces of attraction between atoms
      • Ionic Bonds: Electrons are transferred from a metal atom to a non-metal atom, forming ions with opposite charges
      • Covalent Bonds: Atoms share pairs of electrons to complete their outer electron shells
        • Non-polar Covalent Bonds: Electrons are shared equally between atoms
        • Polar Covalent Bonds: Electrons are not shared equally, leading to partial charges on atoms
      • Hydrogen Bonds: Weak attraction between a slightly positive hydrogen atom and a slightly negative atom (e.g., oxygen or nitrogen) of another molecule

    Chemical Bonds

    • Compounds result when atoms of different elements react or bond together

    • Ionic Bonding: Electrons transferred between metal and non-metal atoms, forming ions (cations and anions) held together by electrostatic forces

    • Covalent Bonding: Atoms share one or more pairs of electrons

      • Polar Covalent: Unequal sharing of electrons, creating partial charges on atoms
      • Nonpolar Covalent: Equal sharing of electrons

    • Hydrogen Bonding: Weak attraction between a partially positive hydrogen atom and a partially negative atom (e.g., oxygen, nitrogen).

      • Water as a solvent:
        • Water dissolves polar molecules because the positive and negative poles of water molecules are attracted to oppositely charged regions of other molecules.
        • Many biological molecules are polar (e.g. sugars, amino acids) and readily dissolve in water
        • Water dissolves gases, such as oxygen and carbon dioxide

    • Water as a reagent:

      • Water is used in many chemical reactions within living cells, including photosynthesis

    • Other biologically significant properties of water

      • High heat capacity: Water absorbs a large amount of heat energy with only a small increase in temperature. This reduces temperature fluctuations for organisms.
      • High latent heat of vaporisation: A relatively large amount of energy is needed to vaporize water, cooling the organism by evaporative heat loss.
      • Density and freezing properties: Ice is less dense than liquid water, allowing ice to float and insulate aquatic environments.
      • High surface tension and cohesion: Water molecules stick together, creating surface tension. This is useful for movement of water in plants and for support of some small organisms.

    Basic Chemistry of Carbon

    • Carbon's role in organic molecules (bonds to 4 other atoms)
    • Single, double, triple bonds possible
    • Functional groups: clusters of atoms that always behave in a certain way
      • Examples: Hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), etc.
    • Isomers: molecules with the same molecular formula, but with different structures (structural, geometric)

    Carbohydrates

    • Monosaccharides: Simple sugars (e.g., glucose, fructose, galactose)
      • Hexoses: Six-carbon sugars (e.g., glucose)
      • Pentoses: Five-carbon sugars (e.g., ribose, deoxyribose)
    • Disaccharides: Two monosaccharides joined by a glycosidic linkage (e.g., maltose, sucrose, lactose)
    • Polysaccharides: Many monosaccharides joined together.
      • Starch: Storage polysaccharide in plants (amylose/amylopectin)
      • Glycogen: Storage polysaccharide in animals
      • Cellulose: Structural component in plant cell walls

    Lipids

    • Triglycerides: Formed from glycerol and three fatty acids; major energy storage molecules.
    • Fatty Acids: Long hydrocarbon chains with a carboxyl group
      • Saturated: No double bonds
      • Unsaturated: One or more double bonds (cis/trans)
    • Phospholipids: Key structural components of cell membranes; have a hydrophilic head and hydrophobic tails.
    • Steroids: Four fused carbon rings (e.g., cholesterol, steroid hormones)

    Proteins

    • Amino Acids: Monomers of proteins; have an amino group (-NH2), a carboxyl group (-COOH) and a variable R group
    • Peptide Bonds: Covalent bonds that link amino acids together to form polypeptides
    • Primary Structure: Linear sequence of amino acids
    • Secondary Structure: Local folding of the polypeptide chain (alpha-helix, beta-pleated sheet) stabilized by hydrogen bonds
    • Tertiary Structure: Further folding of the polypeptide chain into a 3D shape, stabilized by various interactions between R-groups (hydrogen bonds, disulfide bridges, hydrophobic interactions, ionic bonds)
    • Quaternary Structure: Multiple polypeptide chains combining to form a functional protein

    Enzymes

    • Organic catalysts (proteins) that speed up metabolic reactions by lowering activation energy
    • Active Site: Region of the enzyme where the substrate binds
    • Enzyme-Substrate Complex: Temporary complex formed between enzyme and substrate during a reaction
    • Lock-and-Key Model: Substrate fits perfectly into the active site
    • Induced-Fit Model: Enzyme changes shape slightly to accommodate the substrate
    • Factors affecting reaction rate: concentration of enzyme and substrate, temperature, pH

    Enzyme Inhibition

    • Competitive Inhibitors: Similar structure to substrate, competing for the active site
    • Non-competitive Inhibitors: Do not compete for the active site; bind to a different site, changing the enzyme's shape (allosteric) thereby altering its function.
    • Irreversible Inhibitors: Permanently bind to the enzyme, rendering it inactive

    Allosteric Enzymes

    • Enzymes that can be activated or inhibited at an allosteric site, distinct from the active site

    Vitamins as Co-enzymes

    • Cofactors: Non-protein components essential for enzyme activity
    • Coenzymes: Organic cofactors that participate directly in reactions (e.g., NAD+/NADH, FAD/FADH2, coenzyme A)
      • NAD+/NADH and FAD/FADH2: Critical in redox reactions (electron transfer)

    Nucleic Acids

    • Nucleotides: Monomers forming nucleic acids (DNA, RNA, ATP)
      • Composed of a phosphate group, a sugar (deoxyribose/ribose), and a nitrogenous base.
      • Base pairing rules: Adenine(A) with Thymine (T) or Uracil (U); Guanine(G) with Cytosine(C),
      • Polynucleotide chains: Phosphodiester bonds link nucleotides together to form long chains.
      • DNA: Double-stranded helix, stores genetic information; consists of two strands, forming a double helix with the bases paired up to form the steps of the ladder. The strands run in opposite directions (antiparallel).
      • RNA: Single-stranded, involved in protein synthesis; has uracil in place of thymine.
      • mRNA, tRNA, rRNA different types of RNA

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    Description

    Test your knowledge on important biochemical compounds such as lipids and carbohydrates. This quiz covers the roles, structures, and functions of substances like starch, glycogen, and proteins. Dive into the nuances of peptide bonds and the emulsion test for lipids.

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