Lecture 4: Macromolecules
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What is a key characteristic of macromolecules?

  • They are formed through hydrogen bonds.
  • They are large molecules composed of covalently connected atoms numbering in the thousands or more. (correct)
  • They are small molecules made of a few atoms.
  • They have limited variation across different species.

    • Which statement best describes the diversity of macromolecules?

  • Macromolecules have little variation within a single cell.
  • Macromolecules show substantial variation between different species. (correct)
  • Macromolecules exhibit minimal variation between cells of the same organism.
  • Macromolecules are identical across all living species.

    • Which of the following is NOT considered one of the four major classes of macromolecules?

  • Carbohydrates
  • Minerals (correct)
  • Lipids
  • Proteins

    • How is the variation of macromolecules between cells of an organism best described?

    <p>It is less than the variation among members of the same species. (C)</p> Signup and view all the answers

    What type of bonding primarily holds together atoms within a macromolecule?

    <p>Covalent bonding (B)</p> Signup and view all the answers

    What is the primary function of carbohydrates in living organisms?

    <p>To serve as a primary source of fuel and building material (A)</p> Signup and view all the answers

    Which of the following is NOT considered a polymer?

    <p>A monosaccharide (A)</p> Signup and view all the answers

    What type of reaction is responsible for linking monomers together to form a polymer?

    <p>Dehydration (D)</p> Signup and view all the answers

    Which of these correctly describes the breakdown of the polymer into monomers?

    <p>Hydrolysis (D)</p> Signup and view all the answers

    Which of the following is the most common example of a monosaccharide?

    <p>Glucose (C)</p> Signup and view all the answers

    How are monosaccharides generally classified?

    <p>By the location of the carbonyl group and the number of carbons (B)</p> Signup and view all the answers

    What is the relationship between a monosaccharide and a polysaccharide?

    <p>Polysaccharides are made of many linked monosaccharide molecules (C)</p> Signup and view all the answers

    What is the name given to the subunits of a polypeptide when they are linked together?

    <p>Amino acid residues (C)</p> Signup and view all the answers

    Which type of protein is primarily responsible for speeding up chemical reactions?

    <p>Enzymatic proteins (B)</p> Signup and view all the answers

    What is the primary function of defensive proteins in an organism?

    <p>To protect against disease (D)</p> Signup and view all the answers

    Which of these exemplifies a storage protein?

    <p>Casein (D)</p> Signup and view all the answers

    What is the role of hemoglobin in the body?

    <p>Transport oxygen (A)</p> Signup and view all the answers

    Which protein type is directly involved in regulating blood sugar levels?

    <p>Hormonal proteins (C)</p> Signup and view all the answers

    The primary function of receptor proteins is which of the following?

    <p>To respond to chemical stimuli (B)</p> Signup and view all the answers

    Ovalbumin is an example of which protein type?

    <p>Storage protein (A)</p> Signup and view all the answers

    Which of these proteins does not have a function in direct transport?

    <p>Antibodies (B)</p> Signup and view all the answers

    What is the primary function of motor proteins, as described in the text?

    <p>Facilitating the contraction of muscles (C)</p> Signup and view all the answers

    Which of the following is a structural protein?

    <p>Keratin (C)</p> Signup and view all the answers

    What distinguishes different amino acids from one another?

    <p>The differing side chains or R groups (C)</p> Signup and view all the answers

    Which structure is responsible for the undulations of cilia and flagella?

    <p>Motor proteins (C)</p> Signup and view all the answers

    What type of isomer is used to build polypeptides in the body?

    <p>Left-handed isomers (B)</p> Signup and view all the answers

    What is the function of collagen and elastin proteins?

    <p>Providing a fibrous framework in connective tissues (A)</p> Signup and view all the answers

    What is a polypeptide?

    <p>An unbranched polymer built from amino acids (C)</p> Signup and view all the answers

    What is the exception to the 19 out of 20 amino acids that have chiral centers, as described in the text?

    <p>Glycine (B)</p> Signup and view all the answers

    What type of chemical reaction is required to form a disaccharide?

    <p>Dehydration (B)</p> Signup and view all the answers

    What is the primary function of polysaccharides?

    <p>Providing structural support and storing energy (A)</p> Signup and view all the answers

    What determines the structure and therefore function of a polysaccharide?

    <p>The specific monosaccharide monomers and the positions of the glycosidic linkages (D)</p> Signup and view all the answers

    Which of these is a storage polysaccharide commonly found in plants?

    <p>Starch (D)</p> Signup and view all the answers

    What is the simplest form of starch?

    <p>Amylose (C)</p> Signup and view all the answers

    Where is glycogen primarily stored in vertebrates?

    <p>In the liver and muscle cells (B)</p> Signup and view all the answers

    What is a key structural difference between cellulose and starch?

    <p>The glycosidic linkage orientation of $\alpha$ and $\beta$ (D)</p> Signup and view all the answers

    What type of bond holds parallel cellulose molecules together?

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

    Why can’t amylase digest cellulose?

    <p>Amylase can break the alpha links, but not beta links (C)</p> Signup and view all the answers

    Which of the following organisms is MOST LIKELY to express a cellulase enzyme?

    <p>Fungi (B)</p> Signup and view all the answers

    What is the role of the microbes in the digestive system of ruminants and termites?

    <p>To break down cellulose (A)</p> Signup and view all the answers

    What is a unique quality of humans in regards to cellulose digestion?

    <p>Humans cannot digest cellulose (B)</p> Signup and view all the answers

    Where would you most likely find chitin?

    <p>In the cell walls of fungi (C)</p> Signup and view all the answers

    What is the main function of proteins in cells?

    <p>Help transport substances, structural roles and communication (C)</p> Signup and view all the answers

    Which of the following is NOT a function of proteins?

    <p>Storage of genetic information (A)</p> Signup and view all the answers

    Which of the following describes how phospholipids arrange themselves in an aqueous environment?

    <p>They form a bilayer with the hydrophobic tails facing inward, away from water, and the hydrophilic heads facing outwards towards the water. (D)</p> Signup and view all the answers

    What is the primary purpose of adipose tissue in mammals?

    <p>To cushion organs, insulate the body and store fat. (A)</p> Signup and view all the answers

    Which of the following is a key characteristic of a steroid?

    <p>A carbon skeleton of four fused rings. (A)</p> Signup and view all the answers

    How does cholesterol influence cell membrane fluidity in different temperatures?

    <p>It increases fluidity in cold environments and increases viscosity in hot environments. (A)</p> Signup and view all the answers

    What makes a phopholipid an amphipathic molecule?

    <p>The presence of a phosphate group and two non-polar fatty acid tails. (D)</p> Signup and view all the answers

    In a phospholipid, what is directly attached to the glycerol molecule?

    <p>Two fatty acid chains and a phosphate group (B)</p> Signup and view all the answers

    According to the provided information, which of these is a primary element of cell membranes?

    <p>Phospholipids (D)</p> Signup and view all the answers

    What is the effect of high blood cholesterol levels in animals, as highlighted in the text?

    <p>It may contribute to cardiovascular disease. (A)</p> Signup and view all the answers

    What is the key difference between saturated and unsaturated fats, based on the text?

    <p>The text only indicates them as 2 types of lipids one should be aware of, and does not explicitly describe the distinction. (C)</p> Signup and view all the answers

    What is the role of insoluble fiber in the diet within the materials provided?

    <p>The materials do not detail what the main purpose of insoluble fiber within the diet is. (B)</p> Signup and view all the answers

    Study Notes

    Lecture 4: Macromolecules

    • Macromolecules are large molecules composed of covalently connected atoms, numbering in the thousands or more
    • Each cell contains many thousands of different macromolecules
    • Macromolecule variation exists among cells within an organism, and even more between species
    • All living organisms are composed of four classes of macromolecules: carbohydrates, proteins, nucleic acids, and lipids
    • Which of the four macromolecules is different from the others?

    Polymers Built from Monomers

    • A polymer is a large molecule consisting of many similar building blocks, called monomers
    • When part of a polymer, the subunits are often referred to differently (e.g., amino acids in polypeptides)
    • A wide variety of polymers can be built from a small set of monomers
    • A dehydration reaction occurs when two monomers bond together via the loss of a water molecule
    • Polymers break down into monomers through hydrolysis, a reaction that is the opposite of dehydration 

    Carbohydrates

    • Carbohydrates serve as fuel and building materials
    • Carbohydrates include simple sugars and polymers of sugars
    • Monosaccharides are the simplest carbohydrates (single sugars)
    • Two linked sugar molecules are called disaccharides
    • Short chains of sugars are called oligosaccharides
    • The most complex carbohydrate macromolecules are polysaccharides (polymers composed of many sugar building blocks)

    Monosaccharides

    • Monosaccharides have molecular formulas that are usually multiples of CH₂O
    • Monosaccharides are classified by the location of the carbonyl group (aldose or ketose) and the number of carbons in the carbon skeleton
    • Monosaccharides serve as fuel for cells and raw material 

    Carbohydrates: Monosaccharides

    • Monosaccharides exist as linear skeletons, but rings dominate in aqueous solutions
    • Spontaneous isomerizations occur, and equilibrium favors the ring structure

    Carbohydrates: Disaccharides

    • A disaccharide is formed when a dehydration reaction joins two monosaccharides
    • This covalent bond is called a glycosidic linkage

    Carbohydrates: Oligosaccharides

    • Oligosaccharides are short polymers of sugars with diverse roles (building blocks for more complex carbohydrates and signaling molecules, involved in cell-cell recognition)

    Carbohydrates: Polysaccharides

    • Polysaccharides, long polymers of sugars, have storage and structural roles
    • The structure and function of a polysaccharide depend on its sugar monomers and the positions of glycosidic linkages.
    • Starch: a storage polysaccharide in plants (composed of glucose monomers linked in a way called 1-4 linkage)
    • Cellulose: a structural polysaccharide in plants (composed of glucose monomers; different linkage arrangement from starch, leading to a different structure and function)
    • Chitin is a structural polysaccharide in arthropods and fungi (different from cellulose)

    Carbohydrates: Storage Polysaccharides

    • Starch, a storage polysaccharide of plants, consists entirely of glucose monomers
    • Plants store surplus starch as granules within chloroplasts and other plastids.
    • The simplest form of starch is amylose, whereas a branched form of plant starch is amylopectin
    • Glycogen is the storage polysaccharide in animals
    • Humans store glycogen mainly in liver and muscle cells

    Carbohydrates: Structural Polysaccharides

    • Cellulose is a major component of plant cell walls
    • Cellulose differs from starch in the glycosidic linkages; this difference impacts the structure and function of the polymer.
    • Cellulose has straight chains, whereas starch is helical; cellulose’s hydrogen bonds allow parallel cellulose molecules to group into microfibrils, which provide strength
    • Chitin is a structural polysaccharide in the exoskeletons of arthropods and in the cell walls of many fungi.

    Proteins

    • Proteins include a wide variety of structures, resulting in diverse functions.
    • Proteins account for more than 50% of the dry mass of most cells

    Proteins: Huge Diversity of Structures and Functions

    • Enzymatic proteins: Function in selective acceleration of chemical reactions
    • Defensive proteins: Function in protection against disease
    • Storage proteins: Function in storage of amino acids
    • Transport proteins: Function in transport of substances
    • Hormonal proteins: Function in coordination of an organism's activities
    • Receptor proteins: Function in response of cell to chemical stimuli
    • Contractile and motor proteins: Function in movement
    • Structural proteins: Function in support

    Proteins: Amino Acid Monomers

    • Proteins are polymers of amino acids, linked by peptide bonds
    • Polypeptides range in length from a few to thousands of amino acids
    • Each polypeptide has a unique linear sequence of amino acids, with an amino end and a carboxyl end

    Proteins: Structure and Function

    • A protein's unique three-dimensional shape determines its function
    • A protein's structure can be affected by environmental changes (pH, salt concentration, temperature, etc.)

    Proteins: Proper Folding

    • Physical and chemical conditions affecting proteins include pH, salt concentration, temperature, and the presence of detergents
    • Loss of a protein's native structure is called denaturation, and an unfolded protein is biologically inactive

    Nucleic Acids

    • Nucleic acids store, transmit, and help express hereditary information
    • Genes consist of DNA and a nucleic acid made of monomers called nucleotides
    • Two types exist: Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA)

    Nucleic Acids: Nucleotides

    • Nucleic acids are polymers of monomers called nucleotides
    • A nucleotide consists of a nitrogenous base, a pentose sugar, and one or more phosphates
    • Polynucleotides have sugar-phosphate backbones linked by covalent bonds
    • Adjacent nucleotides are joined by covalent bonds

    Nucleic Acids: Base Pairing

    • The nitrogenous bases in DNA pair up (adenine with thymine, and guanine with cytosine), forming hydrogen bonds
    • Complementary base pairing also occurs between two RNA molecules

    Nucleic Acids: Structures of DNA and RNA

    • DNA molecules have two polynucleotides spiraling around an imaginary axis, forming a double helix.
    • In the DNA double helix, the two backbones run in opposite 5' → 3' directions
    • RNA molecules usually exist as single polynucleotide chains, and these chains can fold back on themselves, which stabilizes their three-dimensional structures

    Lipids

    • Lipids are a diverse group of hydrophobic molecules that do not form polymers
    • The unifying feature of lipids is the little or no affinity for water
    • The most biologically important lipids are fats, phospholipids, and steroids 

    Lipids: Fats

    • Fats are constructed from two types of smaller molecules (glycerol and fatty acids)
    • Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon.
    • A fatty acid consists of a carboxyl group attached to a long carbon skeleton
    • Fats separate from water due to hydrophobic nature 
    • Fats are typically solid at room temperature when made from saturated fatty acids
    • Fats are typically liquid at room temperature when made from unsaturated fatty acids. 

    Lipids: Phospholipids

    • In a phospholipid, two fatty acids and a phosphate group are attached to glycerol.
    • The phosphate group can be further modified
    • The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head

    Lipids: Steroids

    • Steroids are lipids characterized by a carbon skeleton consisting of four fused rings
    • Cholesterol is an essential steroid component in animal cell  membranes
    • High cholesterol levels may contribute to cardiovascular disease

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