biological molecules
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Questions and Answers

Which of the following statements about glucose is true?

  • Glucose is a type of lipid.
  • Glucose can exist in both α and β ring forms. (correct)
  • Glucose is a non-reducing sugar.
  • Glucose cannot be a monomer.

    • Fructose is classified as a polysaccharide.

    False

    What bond is formed when two monosaccharides combine to create a disaccharide?

    glycosidic bond

    A __________ is a substance formed from the combination of many monomers.

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

    Match the following types of carbohydrates with their descriptions:

    <p>Monosaccharide = A single sugar molecule Disaccharide = Two sugar molecules joined together Polysaccharide = Multiple sugar molecules linked together Reducing Sugar = A sugar that can donate electrons</p> Signup and view all the answers

    What two monosaccharides are produced when sucrose is hydrolysed?

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

    Starch and glycogen are soluble polysaccharides.

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

    What types of molecules are triglycerides and how are they formed?

    <p>Non-polar hydrophobic molecules formed from glycerol and fatty acids via ester bonds.</p> Signup and view all the answers

    The _______ bond is broken when water is added to sucrose during hydrolysis.

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

    Match the polysaccharides with their primary characteristics:

    <p>Starch = Storage polysaccharide in plants Glycogen = Storage polysaccharide in animals Cellulose = Structural polysaccharide in plants Triglycerides = Energy storage molecules</p> Signup and view all the answers

    What is the primary function of globular proteins in the body?

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

    Fibrous proteins have a complex tertiary structure and are soluble in water.

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

    Name one example of a conjugated protein.

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

    Collagen forms a triple helix known as __________.

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

    Match the following features with their corresponding protein type:

    <p>Globular proteins = Involved in catalysis and immune response Fibrous proteins = Provide structural support</p> Signup and view all the answers

    Which amino acid is most commonly found in collagen?

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

    Collagen is a soluble fibrous protein found only in skin.

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

    What type of bond primarily holds the polypeptide chains in collagen together?

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

    What is the primary role of phospholipids in a cell?

    <p>Forming the main component of cell membranes</p> Signup and view all the answers

    Phospholipids are hydrophobic substances that do not interact with water.

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

    How do saturated and unsaturated fatty acid tails affect the fluidity of cell membranes?

    <p>Saturated fatty acid tails make membranes less fluid, while unsaturated fatty acid tails make membranes more fluid.</p> Signup and view all the answers

    The central carbon atom in an amino acid is bonded to an amine group, a carboxylic acid group, a hydrogen atom, and an ______.

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

    Match the following proteins with their functions:

    <p>Enzymes = Catalysts for biochemical reactions Transport proteins = Carry substances across cell membranes Hormones = Chemical messengers Structural proteins = Provide support and shape to cells</p> Signup and view all the answers

    Which type of interaction helps control the orientation of membrane proteins?

    <p>Weak hydrophobic interactions</p> Signup and view all the answers

    There are 20 types of amino acids commonly found in proteins across all living organisms.

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

    Name one immunoprotein mentioned in the context of proteins.

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

    Which type of bond is formed between cysteine amino acids?

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

    Ionic bonds are the weakest bonds in tertiary structured proteins.

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

    What is the three-dimensional configuration of a protein called?

    <p>tertiary structure</p> Signup and view all the answers

    The bonds that help stabilize proteins, which are known as __________ bridges, are formed between cysteine R groups.

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

    Match the following types of bonds with their characteristics:

    <p>Hydrogen = Weakest and most common bonds Ionic = Formed between charged R groups Disulphide = Strong covalent bonds between cysteine Hydrophobic = Interactions between non-polar R groups</p> Signup and view all the answers

    What type of interactions are primarily responsible for the folding of a polypeptide chain into its tertiary structure?

    <p>R group interactions</p> Signup and view all the answers

    Quaternary structure involves more than one polypeptide chain working together.

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

    What occurs when disulphide bonds are broken?

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

    Study Notes

    Carbohydrates

    • Carbohydrates are polymers that are made of monomers called monosaccharides
    • They contain carbon, hydrogen and oxygen atoms, with a general formula of Cx(H2O)y
    • Monosaccharides are single sugar molecules that dissolve readily.
    • Disaccharides are made of two monosaccharides joined by glycosidic bonds.
    • Polysaccharides are long chains of many monosaccharides joined together.
    • The formation of a glycosidic bond is a condensation reaction where a molecule of water is removed.
    • The breakage of a glycosidic bond is a hydrolysis reaction where a molecule of water is added.

    Reducing Sugars

    • Glucose, fructose and maltose are reducing sugars, meaning they can donate electrons to other molecules.
    • Sucrose is a non-reducing sugar, because it can't donate electrons.
    • This is because the glycosidic bond is formed between the anomeric carbons of the two monosaccharides, preventing the free aldehyde or ketone group needed for reducing ability.

    Polysaccharides

    • Polysaccharides are complex carbohydrates made up of many monosaccharide units.
    • These include starch, glycogen, and cellulose.
    • They are formed by condensation reactions.
    • Their structure is related to their function.

    Starch

    • Starch is a storage polysaccharide found in plants.
    • It forms granules in plastids.
    • Starch exists in two forms, amylose and amylopectin.
    • Amylose is unbranched and helical.
    • Amylopectin is branched and more compact.
    • These structures make starch ideal for storing energy.

    Glycogen

    • Glycogen is a storage polysaccharide found in animals.
    • It forms granules in the cytoplasm.
    • Glycogen is highly branched, making it even more compact than amylopectin.
    • This structure allows for rapid release of glucose when needed.

    Cellulose

    • Cellulose is a structural polysaccharide found in plant cell walls.
    • It forms long, straight chains of β-glucose molecules.
    • The chains are linked together by hydrogen bonds, creating strong, rigid fibers.
    • This structure provides support and rigidity to plant cells.

    Lipids

    • All lipids are hydrophobic and non-polar.
    • They are important for energy storage, insulation, and other functions.
    • Triglycerides are a type of lipid that is most common in organisms.

    Triglycerides

    • Triglycerides are composed of a glycerol molecule and three fatty acids.
    • Fatty acids are long hydrocarbon chains with a carboxyl group at one end.
    • They can be saturated or unsaturated.
    • Saturated fats are solid at room temperature because they have only single bonds between carbon atoms.
    • Unsaturated fats are liquid at room temperature because they have some double bonds between carbon atoms creating 'kinks' in the chain.
    • The ester bond forms between the glycerol molecule and fatty acids through condensation reactions.

    Phospholipids

    • Phospholipids are similar to triglycerides but contain a phosphate group instead of one fatty acid.
    • They are amphipathic, meaning they have both hydrophobic and hydrophilic parts.
    • They are the primary molecule in the structure of cell membranes.
    • The hydrophilic phosphate heads face the aqueous environment inside and outside the cell.
    • The hydrophobic fatty acid tails form the inner core of the bilayer membrane, acting as a barrier to water-soluble molecules.

    Proteins

    • Proteins are polymers made of monomers called amino acids.
    • There are 20 common amino acids in organisms.
    • These amino acids can be linked in many different sequences, creating a wide variety of proteins.
    • The sequence of amino acids in a protein determines its shape and function.
    • Proteins play many vital roles in cells, including:
      • Enzymes
      • Cell membrane proteins
      • Hormones
      • Immunoglobulins
      • Transport proteins
      • Structural proteins
      • Contractile proteins

    Amino Acids

    • Amino acids consist of a central carbon atom bonded to:
      • An amino group (-NH2)
      • A carboxyl group (-COOH)
      • A hydrogen atom
      • An R group (side chain) that varies between amino acids
    • The R group differs between each amino acid, giving it unique properties.
    • The amino and carboxyl groups form peptide bonds to join amino acids together.

    Protein Structures

    • The primary structure of a protein is its amino acid sequence.
    • The secondary structure of a protein is formed by hydrogen bonding between amino acids in the polypeptide chain.
      • This can result in an α-helix or β-pleated sheet.
    • The tertiary structure of a protein is formed by interactions between the R groups of amino acids in the polypeptide chain.
      • This can result in a variety of shapes, such as globular or fibrous.
    • The quaternary structure of a protein is formed by the interaction of multiple polypeptide chains.

    Bonds in Proteins

    • Proteins are held together by various types of bonds:
      • Peptide bonds: between amino acids (primary structure)
      • Hydrogen bonds: contribute to the secondary and tertiary structures
      • Disulphide bonds: between cysteine amino acids; stronger and help to stabilize the tertiary structure
      • Ionic bonds: between charged R groups; stronger than hydrogen bonds but less common
      • Hydrophobic interactions: between non-polar R groups; occur in the interior of the polypeptide chain
      • Van der Waals forces: weak forces between non-polar R groups; contribute to protein stability

    Fibrous Proteins

    • Long, insoluble polypeptide chains
    • Have a limited number of amino acids with a repetitive sequence
    • Examples include keratin, collagen, and elastin
    • Play structural roles in cells and tissues due to their strength and insolubility
    • Keratin is found in hair, skin, and nails.
    • Collagen is a major component of connective tissues such as tendons, ligaments, and cartilage.

    Collagen

    • The most common structural protein in vertebrates.
    • Forms a triple helix structure.
    • Contains many glycine, proline, and hydroxyproline amino acids.
    • Glycine is critical because it allows the three strands to pack tightly.
    • Provides strength and support to tissues due to its structure and cross-linking.

    Globular Proteins

    • Fold into compact, three-dimensional shapes.
    • Have a more complex tertiary structure.
    • Examples include enzymes, antibodies, and hormones.
    • Involved in a wide range of functions, including catalysis, transport, and signaling.

    Haemoglobin

    • A globular protein that contains a prosthetic group called haem.
    • Haem binds to oxygen molecules to transport oxygen throughout the body.
    • Its quaternary structure and haem group allow for efficient oxygen binding.
    • Consists of four polypeptide chains and four haem groups.

    Enzymes

    • Biological catalysts that speed up chemical reactions without being used up themselves.
    • Highly specific for their substrates, the molecules they act upon.
    • Have an active site that binds to the substrate.
    • The shape and chemical properties of the active site determine the enzyme's specificity.
    • Can be denatured by changes in temperature or pH.

    Immunoglobulins (Antibodies)

    • Part of the immune system.
    • Recognize and bind to specific antigens (foreign molecules).
    • This binding triggers a cascade of events that can neutralize or destroy the antigen.
    • Their structure allows them to bind to specific antigens.
    • Have a variable region that binds to the antigen and a constant region that interacts with other immune cells.

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    Chapter 2: Biological Molecules PDF

    Description

    This quiz covers the structure and types of carbohydrates, including monosaccharides, disaccharides, and polysaccharides. It also explores the classification of reducing and non-reducing sugars, providing insights into their chemical properties. Test your understanding of these essential biomolecules!

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