Biology Chapter on Proteins and Lipids
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What is the result of performing the emulsion test if lipids are present?

  • The sample dissolves completely in water
  • A milky emulsion forms (correct)
  • A red color appears
  • The solution becomes clear

    • Sudan III dye can be used to identify water-soluble substances.

    False

    What type of bonds are involved in the tertiary structure of proteins?

    H-bonding, ionic bonds, disulphide bridges, and hydrophobic and hydrophilic interactions

    The two amino acids that contain sulfur in their R groups are _______ and _______.

    <p>cysteine, methionine</p> Signup and view all the answers

    Match the protein structure levels with their descriptions:

    <p>Primary structure = Sequence of amino acids Secondary structure = Alpha-helix and beta-pleated sheet Tertiary structure = Three-dimensional shape formed by interactions Quaternary structure = Complex of multiple polypeptide chains</p> Signup and view all the answers

    Which protein is known to have a structural role?

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

    Proteins account for less than 50% of the dry mass in most cells.

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

    Explain the importance of the shape of proteins in relation to their function.

    <p>The shape of proteins is crucial as it determines their functionality, allowing for specific interactions and activities like enzymatic action and binding to other molecules.</p> Signup and view all the answers

    What is formed when two amino acids are linked together?

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

    Peptide bonds are formed through hydrolysis.

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

    How many different amino acids are commonly found in naturally occurring proteins?

    <p>20</p> Signup and view all the answers

    Proteins are composed primarily of carbon, hydrogen, oxygen, and __________.

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

    Match the following terms with their definitions:

    <p>Peptide bond = Linkage formed between amino acids Dipeptide = Compound formed by two amino acids Polypeptide = Chain of many amino acids Condensation = Reaction that produces water and bonds amino acids</p> Signup and view all the answers

    Which functional groups are involved in the formation of a peptide bond?

    <p>Amino group and carboxylic group</p> Signup and view all the answers

    Proteins are the least abundant organic molecules found in cells.

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

    What determines the primary structure of a protein?

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

    The covalent bond that links amino acids is called a __________.

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

    Which of the following elements can be found in some proteins besides carbon, hydrogen, oxygen, and nitrogen?

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

    What happens to the rate of an enzyme-catalyzed reaction when substrate concentration increases?

    <p>It increases until a saturation point is reached.</p> Signup and view all the answers

    Increasing enzyme concentration always results in a proportional increase in reaction rate.

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

    What is the theoretical maximum rate of an enzyme-catalyzed reaction called?

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

    Enzymes have an optimum __________ at which they catalyze reactions at the maximum rate.

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

    Match the following factors with their effects on enzyme-catalyzed reactions:

    <p>Enzyme concentration = Increases reaction rate with more active sites Substrate concentration = Increases until saturation is reached Temperature = Increases until optimum temperature is surpassed pH = Can either increase or decrease reaction rate depending on enzyme</p> Signup and view all the answers

    What occurs to an enzyme if the temperature exceeds its optimum level?

    <p>It denatures and loses activity.</p> Signup and view all the answers

    What is the relationship between kinetic energy and reaction rate in enzyme-catalyzed reactions at lower temperatures?

    <p>Lower kinetic energy leads to fewer successful collisions.</p> Signup and view all the answers

    What is denaturation of proteins?

    <p>The loss of a protein's 3-dimensional structure</p> Signup and view all the answers

    Fibrous proteins are primarily involved in enzymatic functions.

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

    What role does collagen play in the body?

    <p>It provides structural support and tensile strength to tissues.</p> Signup and view all the answers

    Proteins are composed of __________ folded into specific three-dimensional structures.

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

    Match the role of the protein to its type:

    <p>Enzymes = Biological catalysts promoting reactions Antibodies = Identifying foreign invaders Collagen = Providing structural integrity Insulin = Regulating glucose levels</p> Signup and view all the answers

    Which of the following factors can cause denaturation of proteins?

    <p>All of the above</p> Signup and view all the answers

    Globular proteins are known for providing structural support in the body.

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

    What is the primary function of enzymes in biological processes?

    <p>To act as catalysts that promote chemical reactions.</p> Signup and view all the answers

    A protein's __________ shape determines its specific interactions and function.

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

    Which type of protein is structured to resist mechanical stress?

    <p>Fibrous proteins</p> Signup and view all the answers

    Which type of bond only occurs between cysteine amino acids?

    <p>Disulfide bridge</p> Signup and view all the answers

    Ionic bonds can occur between uncharged R groups in amino acids.

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

    What is the general shape formed by the tertiary structure of a protein?

    <p>Globular shape</p> Signup and view all the answers

    A tertiary structure is maintained by interactions such as __________ and __________ _____.

    <p>disulfide bridges, hydrogen bonds</p> Signup and view all the answers

    Match the type of bond or interaction with its description:

    <p>Hydrogen bond = Weak attraction between a hydrogen atom and electronegative atom Disulfide bridge = Covalent bond between the sulfur atoms of cysteine Ionic bond = Attraction between charged R groups Hydrophobic interactions = Tendency of non-polar R groups to avoid water</p> Signup and view all the answers

    Which method can be used to determine the tertiary structure of a protein?

    <p>X-ray crystallography</p> Signup and view all the answers

    What part of the amino acid participates in the interactions that stabilize the tertiary structure?

    <p>R groups</p> Signup and view all the answers

    Weak hydrophobic interactions are also known as van der Waals interactions.

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

    For hydrogen bonding to occur, __________ functional groups or atoms need to be present in the R-groups.

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

    How many polypeptide chains are shown in the tertiary protein structure?

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

    Study Notes

    Biochemistry (Basic Molecules and Enzymes)

    • This section covers basic biochemistry, including elements, atoms, isotopes, chemical bonds, basic molecules, and enzymes.
    • The most common elements found in living organisms are carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur.

    Basic Chemistry

    • Matter is anything that takes up space and has mass.
    • Elements are substances that cannot be broken down into simpler substances. (e.g., carbon, hydrogen, oxygen, etc.)
    • Atoms are the basic units of matter.
    • Atoms are composed of a nucleus containing protons (positive charge) and neutrons (no charge), and electrons (negative charge) orbiting the nucleus.
    • Isotopes of an element have the same number of protons and electrons but a different number of neutrons.
    • Electron shells determine how atoms interact.
    • First shell holds up to 2 electrons; second shell holds up to 8; third shell also holds up to 8 (under certain conditions).
    • Atoms with incomplete outer shells (valence shells) are reactive.
    • Atoms bond when their atoms share, gain, or lose electrons.
    • Compounds result when atoms from different elements react.
    • Chemical bonds form when there are forces between atoms.

    Chemical Bonds

    • Ionic bonding: occurs between metal and non-metal atoms. Electrons are transferred resulting in oppositely charged ions (cations and anions), which attract each other.
    • Covalent bonding: occurs between non-metal atoms. Atoms share electrons to form molecules.
    • Polar covalent bonding: Unequal sharing of electrons, creating a partial positive and negative charge on the atoms involved. This is especially important in water molecules because of the difference in electronegativity between oxygen and hydrogen atoms.
    • Nonpolar covelant bonding: Equal sharing of electrons. Does not result in any net charge.
    • Hydrogen bonding: a weak attraction between a hydrogen atom on one molecule and a highly electronegative atom (like oxygen or nitrogen) on another molecule. This type of bonding is very important in biological systems.
    • van der Waals forces: very weak attractions between molecules as a result of temporary fluctuations in electron distribution, important in nonpolar molecules.

    Water

    • Water is crucial in biological systems. It is a polar molecule.
    • The polarity of water creates hydrogen bonds between water molecules, which give water several unique properties.

    The Biomolecules of Life

    • Carbohydrates

      • Monosaccharides (simple sugars): single unit with a three to seven carbon skeleton.
      • Glucose is one of the most important monosaccharides; it is a major energy source in living organisms.
      • Disaccharides are formed by linking two monosaccharides via glycosidic bonds (example, maltose = glucose + glucose)
      • Polysaccharides (complex carbohydrates): long chains of monosaccharides linked together. Examples include starch (energy storage for plants), cellulose (structural component in plants), and glycogen (energy storage in animals).

    • Lipids

      • Triglycerides are composed of glycerol and three fatty acids.
      • Fatty acids can be saturated (no double bonds) or unsaturated (one or more double bonds).
      • Phospholipids contain a polar head and two nonpolar tails, which are crucial for cell membrane structure.
      • Steroids are lipids that have a complex ring structure (e.g., cholesterol = critical component of cell membranes).

    • Proteins

      • Proteins are composed of amino acids linked by peptide bonds. Different R-groups give amino acids their uniqueness.
      • The primary structure is the linear sequence of amino acids.
      • Secondary structures (such as alpha-helical or beta-pleated sheets) are stabilized by hydrogen bonds between the amino acid backbone.
      • Tertiary structure is the three-dimensional shape of a polypeptide chain. It is stabilized by various interactions among amino acid side chains (R groups), including hydrogen bonds, disulfide bridges, ionic bonds, and hydrophobic interactions.
      • Some proteins have quaternary structure, which results from the aggregation of multiple polypeptide chains.

    • Nucleic Acids

      • Nucleic acids are polymers composed of nucleotides.
      • The two major nucleic acids are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
      • Nucleotides consist of a sugar, a nitrogenous base, and a phosphate group.
      • DNA is a double helix that stores genetic information.
      • RNA has a variety of functions, including protein synthesis.

    Enzymes

    • Enzymes are biological catalysts, accelerating reactions in living organisms.
    • Enzymes are proteins with a specific 3D structure.
    • The region of the enzyme where the substrate binds is called the active site.
    • Enzymes reduce the activation energy needed for a reaction to occur.
    • The substrate fits into the active site, forming an enzyme-substrate complex.
    • The reaction then occurs, turning the substrate into products.
    • The products leave the active site, freeing the enzyme to react with another substrate.
    • Factors affecting enzyme activity: temperature, pH, enzyme concentration, and substrate concentration. Enzyme Inhibitors

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    Biochemistry Basic Molecules and enzymes 2024-25 PDF

    Description

    Test your knowledge on proteins and lipids with this quiz focused on their structures, functions, and relationships. Explore concepts like emulsion tests, amino acids, and the importance of protein shape. Perfect for biology students seeking to refine their understanding of essential biomolecules.

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