Biol Ch3
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Questions and Answers

What are waxes formed from?

Fatty acids combining with long-chain alcohols or hydrocarbon structures

What is the primary lipid of cell membranes?

  • Phospholipids (correct)
  • Triglycerides
  • Waxes
  • Steroids

    • Phospholipids have a polar and a nonpolar end.

    True

    ______ is an important component of animal cell membranes.

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

    Match the following lipid types with their functions:

    <p>Chlorophylls and carotenoids = Absorb light and help convert it to chemical energy in plants Glycolipids = Formed by combining lipids with carbohydrates in cell membranes Lipoproteins = Formed by combining lipids with proteins in cell membranes</p> Signup and view all the answers

    What are the four major classes of organic molecules found in living organisms?

    <p>Carbohydrates, lipids, proteins, nucleic acids</p> Signup and view all the answers

    Hydrocarbons are molecules consisting of carbon linked only to oxygen atoms.

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

    What is the function of a chaperonin?

    <p>Chaperonins promote correct association of individual amino acid chains and inhibit incorrect formations.</p> Signup and view all the answers

    Which types of R-group interactions are involved in determining the tertiary structure of proteins?

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

    What is the process by which trees and plants convert water and carbon dioxide into sugars using sunlight?

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

    Nucleotides, the monomers of nucleic acids, consist of a nitrogenous base, a five-carbon sugar, and __________ linked together by covalent bonds.

    <p>one to three phosphate groups</p> Signup and view all the answers

    Carbohydrates contain carbon, hydrogen, and oxygen atoms in a ratio of about 1C:2H:1O, with the formula CH2O. Monosaccharides contain three to seven 1.

    <p>carbon atoms</p> Signup and view all the answers

    Proteins with multiple functions often have individual functions located in the same domain.

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

    What is the key difference between deoxyribose and ribose?

    <p>The chemical group bound to the 2' carbon (—H in deoxyribose, —OH in ribose)</p> Signup and view all the answers

    Which structure contains only a nitrogenous base and a five-carbon sugar?

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

    In DNA, adenine pairs only with cytosine.

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

    Complementary base pairing in DNA allows the sequence of one polynucleotide chain to determine the sequence of its __________ in the double helix.

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

    Match the following bases with their complementary partners:

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

    What type of lipids combine with long-chain alcohols or hydrocarbon structures to form waxes?

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

    What is the primary lipid found in cell membranes?

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

    Steroids are lipids with structures based on a framework of five carbon rings.

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

    Phospholipids form a ____________ in cell membranes, which is the structural basis of membranes.

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

    Match the lipid types with their functions:

    <p>Chlorophylls and carotenoids = Absorb light and help convert it to chemical energy in plants Glycolipids = Combine with carbohydrates Lipoproteins = Combine with proteins</p> Signup and view all the answers

    What are the polymers of amino acid monomers called?

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

    What are the four major classes of organic molecules found in living organisms?

    <p>carbohydrates, lipids, proteins, nucleic acids</p> Signup and view all the answers

    Which functional groups frequently enter into biological reactions?

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

    Polysaccharides are polymers of hundreds or thousands of glucose units.

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

    Carbohydrates contain carbon, hydrogen, and oxygen atoms in a ratio of about 1C:2H:1O, often represented as ___.

    <p>CH2O</p> Signup and view all the answers

    What are the two common types of neutral lipids?

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

    What is the role of random coil in proteins?

    <p>Provide flexible sites for folding</p> Signup and view all the answers

    What are the five important types of R-group interactions in proteins?

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

    What is the key difference between deoxyribose and ribose sugars?

    <p>The chemical group bound to the 2′ carbon</p> Signup and view all the answers

    What is a nucleotide?

    <p>A structure containing a nitrogenous base and a five-carbon sugar</p> Signup and view all the answers

    What is denaturation of a protein?

    <p>Unfolding of a protein</p> Signup and view all the answers

    Denaturation of proteins can sometimes be reversible.

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

    Adenine only pairs with thymine in DNA base pairing.

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

    What is the main function of chaperonin proteins in protein folding?

    <p>Guide protein folding towards correct tertiary structure</p> Signup and view all the answers

    In RNA, __________ takes the place of thymine in DNA.

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

    Match the following DNA and RNA components:

    <p>Deoxyribose = Found in DNA Uracil = Found in RNA Phosphodiester bonds = DNA and RNA backbone bonds Ribose = Found in RNA</p> Signup and view all the answers

    Which types of interactions contribute to quaternary structure in proteins?

    <p>Nonpolar attractions</p> Signup and view all the answers

    What are waxes primarily composed of?

    <p>Fatty acids combine with long-chain alcohols or hydrocarbon structures.</p> Signup and view all the answers

    What is the primary function of waxy coatings in animals?

    <p>Protect skin, hair, or feathers</p> Signup and view all the answers

    Phospholipids are the primary lipids of cell membranes.

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

    In a phospholipid bilayer, the ________ groups face the surrounding water molecules.

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

    Match the following lipid types with their functions:

    <p>Chlorophylls and carotenoids = Absorb light and help convert it to chemical energy in plants Glycolipids = Combine with carbohydrates to form Lipoproteins = Combine with proteins to form, important roles in cell membranes</p> Signup and view all the answers

    What is the difference between Deoxyribose in DNA deoxyribonucleotides and Ribose in RNA ribonucleotides?

    <p>Presence of a different chemical group attached to the 2' carbon</p> Signup and view all the answers

    What is the term for an irregularly folded arrangement of a protein?

    <p>Random coil</p> Signup and view all the answers

    DNA and RNA consist of single polynucleotide chains.

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

    What is the primary difference in structure between DNA and RNA?

    <p>RNA contains uracil instead of thymine</p> Signup and view all the answers

    Which of the following is NOT an important type of R-group interaction for tertiary structure?

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

    The sides of the DNA ladder are composed of sugar-phosphate backbones, while the rungs are made up of ____________.

    <p>nitrogenous bases</p> Signup and view all the answers

    Denaturation of a protein involves maintaining its structure and function.

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

    The tertiary structure of most proteins is ________, allowing them to undergo limited conformational changes.

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

    Match the following base pairs with the correct number of hydrogen bonds they form:

    <p>Adenine-Thymine (A-T) = Two hydrogen bonds Guanine-Cytosine (G-C) = Three hydrogen bonds</p> Signup and view all the answers

    Match the following nitrogenous bases with their respective types:

    <p>Uracil, Thymine, Cytosine = Pyrimidines Adenine, Guanine = Purines</p> Signup and view all the answers

    What process do trees and plants use to combine water and carbon dioxide into sugars and other carbon-based compounds?

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

    Which four major classes of organic molecules are found in living organisms?

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

    Hydrocarbons involve carbon atoms bonding covalently to each other and to other atoms in molecules.

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

    Molecules consisting of carbon linked only to hydrogen atoms are called ________.

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

    Match the following functional groups with their properties:

    <p>Hydroxyl group = Can donate a 'Hydrogen' ion in water, acts as an Acid. Carbonyl group = Can accept a 'Hydrogen' ion in water, acts as a Base. Phosphate group = Example of a group which can donate a 'Hydrogen' ion in water. Sulfhydryl group = Example of a group which can accept a 'Hydrogen' ion in water. Amino group = Functional group that frequently enters biological reactions.</p> Signup and view all the answers

    What process allows trees and plants to convert water and carbon dioxide into sugars and other carbon-based compounds?

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

    Which are the four major classes of organic molecules found in living organisms?

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

    What is the function of tertiary structure in proteins?

    <p>Tertiary structure gives a protein its overall three-dimensional shape.</p> Signup and view all the answers

    Enzymes that catalyze biochemical reactions involving amino acids recognize the L-stereoisomer.

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

    Which type of interaction between R-groups involves weak electrical interactions?

    <p>van der Waals interactions</p> Signup and view all the answers

    Monosaccharides contain _____ to _____ carbon atoms.

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

    Denaturation of proteins can be caused by changes in pH.

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

    Match the following types of proteins with their examples:

    <p>Enzyme = Lysozyme Complex protein = Hemoglobin Guide protein = Chaperonin</p> Signup and view all the answers

    A nucleotide consists of a nitrogenous base, a sugar, and ___ phosphate group(s).

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

    What are waxes primarily composed of?

    <p>Fatty acids combine with long-chain alcohols or hydrocarbon structures</p> Signup and view all the answers

    Which group of lipids are the primary lipids of cell membranes?

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

    The nonpolar ends of phospholipid molecules in the bilayer face the surrounding water molecules.

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

    Phospholipids have a glycerol backbone linked to two ________ groups and a polar phosphate group.

    <p>fatty acid chains</p> Signup and view all the answers

    Match the following lipid types with their respective functions:

    <p>Chlorophylls and carotenoids = Absorb light and help convert it to chemical energy in plants Glycolipids = Combine with carbohydrates Lipoproteins = Combine with proteins to form structures in cell membranes</p> Signup and view all the answers

    What are the two sugars that differ in DNA and RNA nucleotides?

    <p>Deoxyribose and Ribose</p> Signup and view all the answers

    What is a nucleoside?

    <p>A structure containing only a nitrogenous base and a five-carbon sugar</p> Signup and view all the answers

    DNA molecules are double-stranded and consist of two polynucleotide chains.

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

    DNA is put together like a ladder, with antiparallel sugar–phosphate backbones forming ladder side rails and bases attached to sugars forming ladder ____.

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

    Match the following base pairs:

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

    What are the four major classes of organic molecules found in living organisms?

    <p>carbohydrates, lipids, proteins, and nucleic acids</p> Signup and view all the answers

    What are the common types of lipid molecules?

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

    Saturated fatty acids contain only single bonds between carbon atoms.

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

    Carbohydrates contain carbon, hydrogen, and oxygen atoms in a ratio of about ______C:2H:_O (CH2O).

    <p>1</p> Signup and view all the answers

    What type of lipid combines fatty acids with long-chain alcohols to form harder and less greasy substances?

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

    What is the primary lipid of cell membranes containing a glycerol backbone linked to two fatty acid chains and a polar phosphate group?

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

    Steroids are lipids based on a framework of four carbon rings.

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

    A ______ bond is formed by a dehydration synthesis reaction between the —NH2 group of one amino acid and the —COOH group of another amino acid.

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

    What is the function of a chaperonin?

    <p>Chaperonins promote correct association of amino acid chains and inhibit incorrect formations.</p> Signup and view all the answers

    What are the five important types of R-group interactions for proteins?

    <p>Ionic bonding</p> Signup and view all the answers

    Denaturation is a process that permanently alters the structure and function of a protein.

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

    A nucleotide consists of a nitrogenous base, a five-carbon, ring-shaped sugar, and one to three __________ groups.

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

    What is the difference between deoxyribose and ribose in terms of the chemical group bound to the 2' carbon?

    <p>Deoxyribose has -H bound to the 2' carbon, while ribose has -OH bound to the 2' carbon.</p> Signup and view all the answers

    Which of the following examples are nucleotides? (Select all that apply)

    <p>Adenosine monophosphate (AMP)</p> Signup and view all the answers

    RNA molecules exist mainly as double polynucleotide chains (double-stranded).

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

    In RNA, the base ____ takes the place of thymine in DNA, forming A-U base pairs.

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

    Match the following base pairings:

    <p>Adenine pairs with = Thymine in DNA Guanine pairs with = Cytosine</p> Signup and view all the answers

    What is the primary structural difference between RNA and DNA?

    <p>RNA contains ribose sugar instead of deoxyribose and uracil instead of thymine.</p> Signup and view all the answers

    Which process uses energy from sunlight to combine water and carbon dioxide into sugars and other carbon-based compounds?

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

    Which are the four major classes of organic molecules found in living organisms?

    <p>Nucleic Acids</p> Signup and view all the answers

    Stereoisomers have different molecular structures but the same chemical formula.

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

    What are the three common types of lipid molecules?

    <p>Neutral lipids, Phospholipids, Steroids</p> Signup and view all the answers

    What are waxes primarily composed of?

    <p>Fatty acids combined with long-chain alcohols or hydrocarbon structures</p> Signup and view all the answers

    Which lipid is the primary lipid of cell membranes?

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

    The nonpolar ends of phospholipid molecules collect together in a region that includes water.

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

    Phosphate-containing phospholipids are the primary lipids of __________ membranes.

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

    What is the function of a tertiary structure in proteins?

    <p>It gives a protein its overall three-dimensional shape.</p> Signup and view all the answers

    Which types of R-group interactions are important for tertiary structure?

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

    Denaturation of a protein can be caused by changes in pH.

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

    Nucleotides, the monomers of nucleic acids, consist of a nitrogenous base, a five-carbon, ring-shaped sugar, and one to three ________ groups.

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

    What is the primary difference between deoxyribose and ribose?

    <p>Chemical group bound to the 2′ carbon</p> Signup and view all the answers

    What is the structure of a nucleoside?

    <p>Nitrogenous base and a five-carbon sugar</p> Signup and view all the answers

    DNA and RNA consist of single polynucleotide chains.

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

    Complementary base pairing in DNA allows the sequence of one polynucleotide chain to determine the sequence of its partner in the double helix through ___ and ___ base pairs.

    <p>A–T, G–C</p> Signup and view all the answers

    Match the following terms with the correct description:

    <p>Ribozymes = RNAs that catalyze reactions and have three-dimensional structures Tertiary Structure in RNA = Directed by complementary base pairing Complementary Base Pairing in DNA = Determines partner sequence in the double helix</p> Signup and view all the answers

    Study Notes

    Organic Molecules

    • Four major classes of organic molecules found in living organisms: carbohydrates, lipids, proteins, and nucleic acids
    • Organic molecules consist of carbon atoms bonded covalently to each other and other atoms, forming molecules of varying sizes

    Hydrocarbons

    • Simplest hydrocarbon is CH4 (methane), consisting of a single carbon atom bonded to four hydrogen atoms
    • More complex hydrocarbons involve two or more carbon atoms arranged in linear unbranched chains, linear branched chains, or ring structures
    • Single and double bonds are found in linear and ring hydrocarbons, while triple bonds are only found in two-carbon hydrocarbons

    Chemical Evolution

    • Resulted in the first forms of life on Earth after the formation of organic molecules
    • Involved reactions between inorganic molecules on primordial Earth and the conditions present at that time
    • Stanley Miller and Harold Urey performed a classic set of experiments in 1953 to simulate chemical evolution and formed several complex organic molecules

    Functional Groups

    • Small, reactive groups of atoms that give larger molecules specific chemical properties
    • Functional groups that frequently enter into biological reactions include the hydroxyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl groups
    • Functional groups are linked by covalent bonds to other atoms in biological molecules, usually carbon atoms

    Isomers

    • Carbons linked to four different atoms or functional groups can take either of two fixed positions with respect to other carbons in a chain, resulting in isomers
    • Isomers that are mirror images of each other are called stereoisomers
    • Structural isomers are two molecules with the same chemical formula but with atoms arranged in different ways

    Macromolecules

    • Carbohydrates, lipids, proteins, and nucleic acids are large polymers assembled from subunit molecules (monomers) into a chain by covalent bonds
    • Polymers are assembled from monomers by dehydration synthesis reactions
    • Breakdown of polymers into monomers occurs by hydrolysis
    • Each type of polymeric biological molecule contains one type of monomer

    Carbohydrates

    • Serve many functions, including energy storage and structural roles
    • Contain only carbon, hydrogen, and oxygen atoms in a ratio of about 1C:2H:1O (CH2O)
    • Monosaccharides contain three to seven carbon atoms
    • Two monosaccharides polymerize to form a disaccharide
    • Carbohydrate polymers with more than 10 linked monosaccharide monomers are called polysaccharides

    Lipids

    • Water-insoluble, primarily nonpolar biological molecules composed mostly of hydrocarbons
    • Three common types of lipid molecules:
      • Neutral lipids are stored and used as an energy source
      • Phospholipids form cell membranes
      • Steroids serve as hormones that regulate cellular activities

    Proteins

    • Perform many vital functions in living organisms, including structural support, enzymatic activity, movement, transport, recognition, and receptor functions
    • Macromolecules composed of amino acid monomers, which contain both an amino and a carboxyl group
    • 20 different amino acids are used to build proteins in all organisms### Peptide Bonds
    • Peptide bonds are covalent bonds that link amino acids into polypeptide chains, which are the subunits of proteins.
    • Peptide bonds are formed through a dehydration synthesis reaction between the -NH2 group of one amino acid and the -COOH group of another amino acid.
    • The growing polypeptide chain has an N-terminal end and a C-terminal end, with new amino acids being linked only to the C-terminal end.

    Protein Structure

    • Primary structure of a protein refers to the precise sequence of amino acids linked together.
    • Changing even a single amino acid can alter the secondary, tertiary, and quaternary structures of a protein, which can affect its biological function.
    • Example: Substitution of a single amino acid in hemoglobin produces an altered form responsible for sickle-cell disease.

    Secondary Structure

    • The amino acid chain is folded into arrangements that form the protein's secondary structure.
    • Two common types of secondary structure are:
      • Alpha (α) helix: a twisted, regular right-hand spiral structure stabilized by regularly spaced hydrogen bonds.
      • Beta (β) sheet: a flat, zigzagging structure formed by side-by-side alignment of β strands, stabilized by hydrogen bonds.

    Tertiary Structure

    • Tertiary structure refers to the overall three-dimensional shape of a protein, which is determined by the positions of secondary structures, disulfide linkages, and hydrogen bonds.
    • Attractions between positively and negatively charged chemical groups, as well as polar and nonpolar associations, also contribute to tertiary structure.
    • Tertiary structure determines a protein's function, including its chemical activity, solubility, and ability to undergo conformational changes.

    Quaternary Structure

    • Quaternary structure refers to the presence and arrangement of two or more polypeptide chains in a protein.
    • Hydrogen bonds, polar and nonpolar attractions, and disulfide linkages hold the multiple polypeptide chains together.
    • Chaperonins promote the correct association of individual amino acid chains and inhibit incorrect formations.

    Denaturation

    • Denaturation is the process of unfolding a protein from its active conformation, causing it to lose its structure and function.
    • Denaturation can be caused by chemicals, changes in pH, or high temperatures.
    • Experiments by Christian Anfinsen showed that breaking the disulfide linkages holding a protein in its functional state caused it to unfold and lose enzyme activity.

    Chaperonins

    • Chaperonins are "guide" proteins that bind temporarily with newly synthesized proteins, directing their conformation towards the correct tertiary structure and inhibiting incorrect arrangements.
    • Chaperonins promote the correct association of individual amino acid chains and inhibit incorrect formations.

    Nucleotides and Nucleic Acids

    • Nucleic acids are macromolecules assembled from repeating monomers called nucleotides.
    • DNA (deoxyribonucleic acid) stores hereditary information responsible for inherited traits in all eukaryotes and prokaryotes.
    • RNA (ribonucleic acid) is the hereditary molecule of another large group of viruses and is involved in protein synthesis.

    Nucleotides

    • A nucleotide consists of three parts linked together by covalent bonds:
      • A nitrogenous base (formed from rings of carbon and nitrogen atoms)
      • A five-carbon, ring-shaped sugar (deoxyribose in DNA or ribose in RNA)
      • One to three phosphate groups

    Nitrogenous Bases

    • Pyrimidines are nitrogenous bases with one carbon-nitrogen ring, including uracil (U), thymine (T), and cytosine (C).
    • Purines are nitrogenous bases with two carbon-nitrogen rings, including adenine (A) and guanine (G).

    DNA and RNA

    • DNA and RNA consist of polynucleotide chains, with one nucleotide linked to the next by a phosphodiester bond.
    • DNA is a double-stranded molecule, with two polynucleotide chains wrapped around each other in a spiral.
    • RNA is typically single-stranded, but can form double-helical regions by folding back on itself.

    Complementary Base Pairing

    • The two polynucleotide chains of a DNA double helix are held together by hydrogen bonds between the base pairs.
    • A base pair consists of one purine and one pyrimidine, with adenine (A) pairing with thymine (T) and guanine (G) pairing with cytosine (C).
    • In RNA, the uracil (U) base takes the place of thymine (T), forming A-U base pairs.

    Organic Molecules

    • Four major classes of organic molecules found in living organisms: carbohydrates, lipids, proteins, and nucleic acids
    • Organic molecules consist of carbon atoms bonded covalently to each other and other atoms, forming molecules of varying sizes

    Hydrocarbons

    • Simplest hydrocarbon is CH4 (methane), consisting of a single carbon atom bonded to four hydrogen atoms
    • More complex hydrocarbons involve two or more carbon atoms arranged in linear unbranched chains, linear branched chains, or ring structures
    • Single and double bonds are found in linear and ring hydrocarbons, while triple bonds are only found in two-carbon hydrocarbons

    Chemical Evolution

    • Resulted in the first forms of life on Earth after the formation of organic molecules
    • Involved reactions between inorganic molecules on primordial Earth and the conditions present at that time
    • Stanley Miller and Harold Urey performed a classic set of experiments in 1953 to simulate chemical evolution and formed several complex organic molecules

    Functional Groups

    • Small, reactive groups of atoms that give larger molecules specific chemical properties
    • Functional groups that frequently enter into biological reactions include the hydroxyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl groups
    • Functional groups are linked by covalent bonds to other atoms in biological molecules, usually carbon atoms

    Isomers

    • Carbons linked to four different atoms or functional groups can take either of two fixed positions with respect to other carbons in a chain, resulting in isomers
    • Isomers that are mirror images of each other are called stereoisomers
    • Structural isomers are two molecules with the same chemical formula but with atoms arranged in different ways

    Macromolecules

    • Carbohydrates, lipids, proteins, and nucleic acids are large polymers assembled from subunit molecules (monomers) into a chain by covalent bonds
    • Polymers are assembled from monomers by dehydration synthesis reactions
    • Breakdown of polymers into monomers occurs by hydrolysis
    • Each type of polymeric biological molecule contains one type of monomer

    Carbohydrates

    • Serve many functions, including energy storage and structural roles
    • Contain only carbon, hydrogen, and oxygen atoms in a ratio of about 1C:2H:1O (CH2O)
    • Monosaccharides contain three to seven carbon atoms
    • Two monosaccharides polymerize to form a disaccharide
    • Carbohydrate polymers with more than 10 linked monosaccharide monomers are called polysaccharides

    Lipids

    • Water-insoluble, primarily nonpolar biological molecules composed mostly of hydrocarbons
    • Three common types of lipid molecules:
      • Neutral lipids are stored and used as an energy source
      • Phospholipids form cell membranes
      • Steroids serve as hormones that regulate cellular activities

    Proteins

    • Perform many vital functions in living organisms, including structural support, enzymatic activity, movement, transport, recognition, and receptor functions
    • Macromolecules composed of amino acid monomers, which contain both an amino and a carboxyl group
    • 20 different amino acids are used to build proteins in all organisms### Peptide Bonds
    • Peptide bonds are covalent bonds that link amino acids into polypeptide chains, which are the subunits of proteins.
    • Peptide bonds are formed through a dehydration synthesis reaction between the -NH2 group of one amino acid and the -COOH group of another amino acid.
    • The growing polypeptide chain has an N-terminal end and a C-terminal end, with new amino acids being linked only to the C-terminal end.

    Protein Structure

    • Primary structure of a protein refers to the precise sequence of amino acids linked together.
    • Changing even a single amino acid can alter the secondary, tertiary, and quaternary structures of a protein, which can affect its biological function.
    • Example: Substitution of a single amino acid in hemoglobin produces an altered form responsible for sickle-cell disease.

    Secondary Structure

    • The amino acid chain is folded into arrangements that form the protein's secondary structure.
    • Two common types of secondary structure are:
      • Alpha (α) helix: a twisted, regular right-hand spiral structure stabilized by regularly spaced hydrogen bonds.
      • Beta (β) sheet: a flat, zigzagging structure formed by side-by-side alignment of β strands, stabilized by hydrogen bonds.

    Tertiary Structure

    • Tertiary structure refers to the overall three-dimensional shape of a protein, which is determined by the positions of secondary structures, disulfide linkages, and hydrogen bonds.
    • Attractions between positively and negatively charged chemical groups, as well as polar and nonpolar associations, also contribute to tertiary structure.
    • Tertiary structure determines a protein's function, including its chemical activity, solubility, and ability to undergo conformational changes.

    Quaternary Structure

    • Quaternary structure refers to the presence and arrangement of two or more polypeptide chains in a protein.
    • Hydrogen bonds, polar and nonpolar attractions, and disulfide linkages hold the multiple polypeptide chains together.
    • Chaperonins promote the correct association of individual amino acid chains and inhibit incorrect formations.

    Denaturation

    • Denaturation is the process of unfolding a protein from its active conformation, causing it to lose its structure and function.
    • Denaturation can be caused by chemicals, changes in pH, or high temperatures.
    • Experiments by Christian Anfinsen showed that breaking the disulfide linkages holding a protein in its functional state caused it to unfold and lose enzyme activity.

    Chaperonins

    • Chaperonins are "guide" proteins that bind temporarily with newly synthesized proteins, directing their conformation towards the correct tertiary structure and inhibiting incorrect arrangements.
    • Chaperonins promote the correct association of individual amino acid chains and inhibit incorrect formations.

    Nucleotides and Nucleic Acids

    • Nucleic acids are macromolecules assembled from repeating monomers called nucleotides.
    • DNA (deoxyribonucleic acid) stores hereditary information responsible for inherited traits in all eukaryotes and prokaryotes.
    • RNA (ribonucleic acid) is the hereditary molecule of another large group of viruses and is involved in protein synthesis.

    Nucleotides

    • A nucleotide consists of three parts linked together by covalent bonds:
      • A nitrogenous base (formed from rings of carbon and nitrogen atoms)
      • A five-carbon, ring-shaped sugar (deoxyribose in DNA or ribose in RNA)
      • One to three phosphate groups

    Nitrogenous Bases

    • Pyrimidines are nitrogenous bases with one carbon-nitrogen ring, including uracil (U), thymine (T), and cytosine (C).
    • Purines are nitrogenous bases with two carbon-nitrogen rings, including adenine (A) and guanine (G).

    DNA and RNA

    • DNA and RNA consist of polynucleotide chains, with one nucleotide linked to the next by a phosphodiester bond.
    • DNA is a double-stranded molecule, with two polynucleotide chains wrapped around each other in a spiral.
    • RNA is typically single-stranded, but can form double-helical regions by folding back on itself.

    Complementary Base Pairing

    • The two polynucleotide chains of a DNA double helix are held together by hydrogen bonds between the base pairs.
    • A base pair consists of one purine and one pyrimidine, with adenine (A) pairing with thymine (T) and guanine (G) pairing with cytosine (C).
    • In RNA, the uracil (U) base takes the place of thymine (T), forming A-U base pairs.

    Organic Molecules

    • Four major classes of organic molecules found in living organisms: carbohydrates, lipids, proteins, and nucleic acids
    • Organic molecules consist of carbon atoms bonded covalently to each other and other atoms, forming molecules of varying sizes

    Hydrocarbons

    • Simplest hydrocarbon is CH4 (methane), consisting of a single carbon atom bonded to four hydrogen atoms
    • More complex hydrocarbons involve two or more carbon atoms arranged in linear unbranched chains, linear branched chains, or ring structures
    • Single and double bonds are found in linear and ring hydrocarbons, while triple bonds are only found in two-carbon hydrocarbons

    Chemical Evolution

    • Resulted in the first forms of life on Earth after the formation of organic molecules
    • Involved reactions between inorganic molecules on primordial Earth and the conditions present at that time
    • Stanley Miller and Harold Urey performed a classic set of experiments in 1953 to simulate chemical evolution and formed several complex organic molecules

    Functional Groups

    • Small, reactive groups of atoms that give larger molecules specific chemical properties
    • Functional groups that frequently enter into biological reactions include the hydroxyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl groups
    • Functional groups are linked by covalent bonds to other atoms in biological molecules, usually carbon atoms

    Isomers

    • Carbons linked to four different atoms or functional groups can take either of two fixed positions with respect to other carbons in a chain, resulting in isomers
    • Isomers that are mirror images of each other are called stereoisomers
    • Structural isomers are two molecules with the same chemical formula but with atoms arranged in different ways

    Macromolecules

    • Carbohydrates, lipids, proteins, and nucleic acids are large polymers assembled from subunit molecules (monomers) into a chain by covalent bonds
    • Polymers are assembled from monomers by dehydration synthesis reactions
    • Breakdown of polymers into monomers occurs by hydrolysis
    • Each type of polymeric biological molecule contains one type of monomer

    Carbohydrates

    • Serve many functions, including energy storage and structural roles
    • Contain only carbon, hydrogen, and oxygen atoms in a ratio of about 1C:2H:1O (CH2O)
    • Monosaccharides contain three to seven carbon atoms
    • Two monosaccharides polymerize to form a disaccharide
    • Carbohydrate polymers with more than 10 linked monosaccharide monomers are called polysaccharides

    Lipids

    • Water-insoluble, primarily nonpolar biological molecules composed mostly of hydrocarbons
    • Three common types of lipid molecules:
      • Neutral lipids are stored and used as an energy source
      • Phospholipids form cell membranes
      • Steroids serve as hormones that regulate cellular activities

    Proteins

    • Perform many vital functions in living organisms, including structural support, enzymatic activity, movement, transport, recognition, and receptor functions
    • Macromolecules composed of amino acid monomers, which contain both an amino and a carboxyl group
    • 20 different amino acids are used to build proteins in all organisms### Peptide Bonds
    • Peptide bonds are covalent bonds that link amino acids into polypeptide chains, which are the subunits of proteins.
    • Peptide bonds are formed through a dehydration synthesis reaction between the -NH2 group of one amino acid and the -COOH group of another amino acid.
    • The growing polypeptide chain has an N-terminal end and a C-terminal end, with new amino acids being linked only to the C-terminal end.

    Protein Structure

    • Primary structure of a protein refers to the precise sequence of amino acids linked together.
    • Changing even a single amino acid can alter the secondary, tertiary, and quaternary structures of a protein, which can affect its biological function.
    • Example: Substitution of a single amino acid in hemoglobin produces an altered form responsible for sickle-cell disease.

    Secondary Structure

    • The amino acid chain is folded into arrangements that form the protein's secondary structure.
    • Two common types of secondary structure are:
      • Alpha (α) helix: a twisted, regular right-hand spiral structure stabilized by regularly spaced hydrogen bonds.
      • Beta (β) sheet: a flat, zigzagging structure formed by side-by-side alignment of β strands, stabilized by hydrogen bonds.

    Tertiary Structure

    • Tertiary structure refers to the overall three-dimensional shape of a protein, which is determined by the positions of secondary structures, disulfide linkages, and hydrogen bonds.
    • Attractions between positively and negatively charged chemical groups, as well as polar and nonpolar associations, also contribute to tertiary structure.
    • Tertiary structure determines a protein's function, including its chemical activity, solubility, and ability to undergo conformational changes.

    Quaternary Structure

    • Quaternary structure refers to the presence and arrangement of two or more polypeptide chains in a protein.
    • Hydrogen bonds, polar and nonpolar attractions, and disulfide linkages hold the multiple polypeptide chains together.
    • Chaperonins promote the correct association of individual amino acid chains and inhibit incorrect formations.

    Denaturation

    • Denaturation is the process of unfolding a protein from its active conformation, causing it to lose its structure and function.
    • Denaturation can be caused by chemicals, changes in pH, or high temperatures.
    • Experiments by Christian Anfinsen showed that breaking the disulfide linkages holding a protein in its functional state caused it to unfold and lose enzyme activity.

    Chaperonins

    • Chaperonins are "guide" proteins that bind temporarily with newly synthesized proteins, directing their conformation towards the correct tertiary structure and inhibiting incorrect arrangements.
    • Chaperonins promote the correct association of individual amino acid chains and inhibit incorrect formations.

    Nucleotides and Nucleic Acids

    • Nucleic acids are macromolecules assembled from repeating monomers called nucleotides.
    • DNA (deoxyribonucleic acid) stores hereditary information responsible for inherited traits in all eukaryotes and prokaryotes.
    • RNA (ribonucleic acid) is the hereditary molecule of another large group of viruses and is involved in protein synthesis.

    Nucleotides

    • A nucleotide consists of three parts linked together by covalent bonds:
      • A nitrogenous base (formed from rings of carbon and nitrogen atoms)
      • A five-carbon, ring-shaped sugar (deoxyribose in DNA or ribose in RNA)
      • One to three phosphate groups

    Nitrogenous Bases

    • Pyrimidines are nitrogenous bases with one carbon-nitrogen ring, including uracil (U), thymine (T), and cytosine (C).
    • Purines are nitrogenous bases with two carbon-nitrogen rings, including adenine (A) and guanine (G).

    DNA and RNA

    • DNA and RNA consist of polynucleotide chains, with one nucleotide linked to the next by a phosphodiester bond.
    • DNA is a double-stranded molecule, with two polynucleotide chains wrapped around each other in a spiral.
    • RNA is typically single-stranded, but can form double-helical regions by folding back on itself.

    Complementary Base Pairing

    • The two polynucleotide chains of a DNA double helix are held together by hydrogen bonds between the base pairs.
    • A base pair consists of one purine and one pyrimidine, with adenine (A) pairing with thymine (T) and guanine (G) pairing with cytosine (C).
    • In RNA, the uracil (U) base takes the place of thymine (T), forming A-U base pairs.

    Organic Molecules

    • Four major classes of organic molecules found in living organisms: carbohydrates, lipids, proteins, and nucleic acids
    • Organic molecules consist of carbon atoms bonded covalently to each other and other atoms, forming molecules of varying sizes

    Hydrocarbons

    • Simplest hydrocarbon is CH4 (methane), consisting of a single carbon atom bonded to four hydrogen atoms
    • More complex hydrocarbons involve two or more carbon atoms arranged in linear unbranched chains, linear branched chains, or ring structures
    • Single and double bonds are found in linear and ring hydrocarbons, while triple bonds are only found in two-carbon hydrocarbons

    Chemical Evolution

    • Resulted in the first forms of life on Earth after the formation of organic molecules
    • Involved reactions between inorganic molecules on primordial Earth and the conditions present at that time
    • Stanley Miller and Harold Urey performed a classic set of experiments in 1953 to simulate chemical evolution and formed several complex organic molecules

    Functional Groups

    • Small, reactive groups of atoms that give larger molecules specific chemical properties
    • Functional groups that frequently enter into biological reactions include the hydroxyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl groups
    • Functional groups are linked by covalent bonds to other atoms in biological molecules, usually carbon atoms

    Isomers

    • Carbons linked to four different atoms or functional groups can take either of two fixed positions with respect to other carbons in a chain, resulting in isomers
    • Isomers that are mirror images of each other are called stereoisomers
    • Structural isomers are two molecules with the same chemical formula but with atoms arranged in different ways

    Macromolecules

    • Carbohydrates, lipids, proteins, and nucleic acids are large polymers assembled from subunit molecules (monomers) into a chain by covalent bonds
    • Polymers are assembled from monomers by dehydration synthesis reactions
    • Breakdown of polymers into monomers occurs by hydrolysis
    • Each type of polymeric biological molecule contains one type of monomer

    Carbohydrates

    • Serve many functions, including energy storage and structural roles
    • Contain only carbon, hydrogen, and oxygen atoms in a ratio of about 1C:2H:1O (CH2O)
    • Monosaccharides contain three to seven carbon atoms
    • Two monosaccharides polymerize to form a disaccharide
    • Carbohydrate polymers with more than 10 linked monosaccharide monomers are called polysaccharides

    Lipids

    • Water-insoluble, primarily nonpolar biological molecules composed mostly of hydrocarbons
    • Three common types of lipid molecules:
      • Neutral lipids are stored and used as an energy source
      • Phospholipids form cell membranes
      • Steroids serve as hormones that regulate cellular activities

    Proteins

    • Perform many vital functions in living organisms, including structural support, enzymatic activity, movement, transport, recognition, and receptor functions
    • Macromolecules composed of amino acid monomers, which contain both an amino and a carboxyl group
    • 20 different amino acids are used to build proteins in all organisms### Peptide Bonds
    • Peptide bonds are covalent bonds that link amino acids into polypeptide chains, which are the subunits of proteins.
    • Peptide bonds are formed through a dehydration synthesis reaction between the -NH2 group of one amino acid and the -COOH group of another amino acid.
    • The growing polypeptide chain has an N-terminal end and a C-terminal end, with new amino acids being linked only to the C-terminal end.

    Protein Structure

    • Primary structure of a protein refers to the precise sequence of amino acids linked together.
    • Changing even a single amino acid can alter the secondary, tertiary, and quaternary structures of a protein, which can affect its biological function.
    • Example: Substitution of a single amino acid in hemoglobin produces an altered form responsible for sickle-cell disease.

    Secondary Structure

    • The amino acid chain is folded into arrangements that form the protein's secondary structure.
    • Two common types of secondary structure are:
      • Alpha (α) helix: a twisted, regular right-hand spiral structure stabilized by regularly spaced hydrogen bonds.
      • Beta (β) sheet: a flat, zigzagging structure formed by side-by-side alignment of β strands, stabilized by hydrogen bonds.

    Tertiary Structure

    • Tertiary structure refers to the overall three-dimensional shape of a protein, which is determined by the positions of secondary structures, disulfide linkages, and hydrogen bonds.
    • Attractions between positively and negatively charged chemical groups, as well as polar and nonpolar associations, also contribute to tertiary structure.
    • Tertiary structure determines a protein's function, including its chemical activity, solubility, and ability to undergo conformational changes.

    Quaternary Structure

    • Quaternary structure refers to the presence and arrangement of two or more polypeptide chains in a protein.
    • Hydrogen bonds, polar and nonpolar attractions, and disulfide linkages hold the multiple polypeptide chains together.
    • Chaperonins promote the correct association of individual amino acid chains and inhibit incorrect formations.

    Denaturation

    • Denaturation is the process of unfolding a protein from its active conformation, causing it to lose its structure and function.
    • Denaturation can be caused by chemicals, changes in pH, or high temperatures.
    • Experiments by Christian Anfinsen showed that breaking the disulfide linkages holding a protein in its functional state caused it to unfold and lose enzyme activity.

    Chaperonins

    • Chaperonins are "guide" proteins that bind temporarily with newly synthesized proteins, directing their conformation towards the correct tertiary structure and inhibiting incorrect arrangements.
    • Chaperonins promote the correct association of individual amino acid chains and inhibit incorrect formations.

    Nucleotides and Nucleic Acids

    • Nucleic acids are macromolecules assembled from repeating monomers called nucleotides.
    • DNA (deoxyribonucleic acid) stores hereditary information responsible for inherited traits in all eukaryotes and prokaryotes.
    • RNA (ribonucleic acid) is the hereditary molecule of another large group of viruses and is involved in protein synthesis.

    Nucleotides

    • A nucleotide consists of three parts linked together by covalent bonds:
      • A nitrogenous base (formed from rings of carbon and nitrogen atoms)
      • A five-carbon, ring-shaped sugar (deoxyribose in DNA or ribose in RNA)
      • One to three phosphate groups

    Nitrogenous Bases

    • Pyrimidines are nitrogenous bases with one carbon-nitrogen ring, including uracil (U), thymine (T), and cytosine (C).
    • Purines are nitrogenous bases with two carbon-nitrogen rings, including adenine (A) and guanine (G).

    DNA and RNA

    • DNA and RNA consist of polynucleotide chains, with one nucleotide linked to the next by a phosphodiester bond.
    • DNA is a double-stranded molecule, with two polynucleotide chains wrapped around each other in a spiral.
    • RNA is typically single-stranded, but can form double-helical regions by folding back on itself.

    Complementary Base Pairing

    • The two polynucleotide chains of a DNA double helix are held together by hydrogen bonds between the base pairs.
    • A base pair consists of one purine and one pyrimidine, with adenine (A) pairing with thymine (T) and guanine (G) pairing with cytosine (C).
    • In RNA, the uracil (U) base takes the place of thymine (T), forming A-U base pairs.

    Organic Molecules

    • Four major classes of organic molecules found in living organisms: carbohydrates, lipids, proteins, and nucleic acids
    • Organic molecules consist of carbon atoms bonded covalently to each other and other atoms, forming molecules of varying sizes

    Hydrocarbons

    • Simplest hydrocarbon is CH4 (methane), consisting of a single carbon atom bonded to four hydrogen atoms
    • More complex hydrocarbons involve two or more carbon atoms arranged in linear unbranched chains, linear branched chains, or ring structures
    • Single and double bonds are found in linear and ring hydrocarbons, while triple bonds are only found in two-carbon hydrocarbons

    Chemical Evolution

    • Resulted in the first forms of life on Earth after the formation of organic molecules
    • Involved reactions between inorganic molecules on primordial Earth and the conditions present at that time
    • Stanley Miller and Harold Urey performed a classic set of experiments in 1953 to simulate chemical evolution and formed several complex organic molecules

    Functional Groups

    • Small, reactive groups of atoms that give larger molecules specific chemical properties
    • Functional groups that frequently enter into biological reactions include the hydroxyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl groups
    • Functional groups are linked by covalent bonds to other atoms in biological molecules, usually carbon atoms

    Isomers

    • Carbons linked to four different atoms or functional groups can take either of two fixed positions with respect to other carbons in a chain, resulting in isomers
    • Isomers that are mirror images of each other are called stereoisomers
    • Structural isomers are two molecules with the same chemical formula but with atoms arranged in different ways

    Macromolecules

    • Carbohydrates, lipids, proteins, and nucleic acids are large polymers assembled from subunit molecules (monomers) into a chain by covalent bonds
    • Polymers are assembled from monomers by dehydration synthesis reactions
    • Breakdown of polymers into monomers occurs by hydrolysis
    • Each type of polymeric biological molecule contains one type of monomer

    Carbohydrates

    • Serve many functions, including energy storage and structural roles
    • Contain only carbon, hydrogen, and oxygen atoms in a ratio of about 1C:2H:1O (CH2O)
    • Monosaccharides contain three to seven carbon atoms
    • Two monosaccharides polymerize to form a disaccharide
    • Carbohydrate polymers with more than 10 linked monosaccharide monomers are called polysaccharides

    Lipids

    • Water-insoluble, primarily nonpolar biological molecules composed mostly of hydrocarbons
    • Three common types of lipid molecules:
      • Neutral lipids are stored and used as an energy source
      • Phospholipids form cell membranes
      • Steroids serve as hormones that regulate cellular activities

    Proteins

    • Perform many vital functions in living organisms, including structural support, enzymatic activity, movement, transport, recognition, and receptor functions
    • Macromolecules composed of amino acid monomers, which contain both an amino and a carboxyl group
    • 20 different amino acids are used to build proteins in all organisms### Peptide Bonds
    • Peptide bonds are covalent bonds that link amino acids into polypeptide chains, which are the subunits of proteins.
    • Peptide bonds are formed through a dehydration synthesis reaction between the -NH2 group of one amino acid and the -COOH group of another amino acid.
    • The growing polypeptide chain has an N-terminal end and a C-terminal end, with new amino acids being linked only to the C-terminal end.

    Protein Structure

    • Primary structure of a protein refers to the precise sequence of amino acids linked together.
    • Changing even a single amino acid can alter the secondary, tertiary, and quaternary structures of a protein, which can affect its biological function.
    • Example: Substitution of a single amino acid in hemoglobin produces an altered form responsible for sickle-cell disease.

    Secondary Structure

    • The amino acid chain is folded into arrangements that form the protein's secondary structure.
    • Two common types of secondary structure are:
      • Alpha (α) helix: a twisted, regular right-hand spiral structure stabilized by regularly spaced hydrogen bonds.
      • Beta (β) sheet: a flat, zigzagging structure formed by side-by-side alignment of β strands, stabilized by hydrogen bonds.

    Tertiary Structure

    • Tertiary structure refers to the overall three-dimensional shape of a protein, which is determined by the positions of secondary structures, disulfide linkages, and hydrogen bonds.
    • Attractions between positively and negatively charged chemical groups, as well as polar and nonpolar associations, also contribute to tertiary structure.
    • Tertiary structure determines a protein's function, including its chemical activity, solubility, and ability to undergo conformational changes.

    Quaternary Structure

    • Quaternary structure refers to the presence and arrangement of two or more polypeptide chains in a protein.
    • Hydrogen bonds, polar and nonpolar attractions, and disulfide linkages hold the multiple polypeptide chains together.
    • Chaperonins promote the correct association of individual amino acid chains and inhibit incorrect formations.

    Denaturation

    • Denaturation is the process of unfolding a protein from its active conformation, causing it to lose its structure and function.
    • Denaturation can be caused by chemicals, changes in pH, or high temperatures.
    • Experiments by Christian Anfinsen showed that breaking the disulfide linkages holding a protein in its functional state caused it to unfold and lose enzyme activity.

    Chaperonins

    • Chaperonins are "guide" proteins that bind temporarily with newly synthesized proteins, directing their conformation towards the correct tertiary structure and inhibiting incorrect arrangements.
    • Chaperonins promote the correct association of individual amino acid chains and inhibit incorrect formations.

    Nucleotides and Nucleic Acids

    • Nucleic acids are macromolecules assembled from repeating monomers called nucleotides.
    • DNA (deoxyribonucleic acid) stores hereditary information responsible for inherited traits in all eukaryotes and prokaryotes.
    • RNA (ribonucleic acid) is the hereditary molecule of another large group of viruses and is involved in protein synthesis.

    Nucleotides

    • A nucleotide consists of three parts linked together by covalent bonds:
      • A nitrogenous base (formed from rings of carbon and nitrogen atoms)
      • A five-carbon, ring-shaped sugar (deoxyribose in DNA or ribose in RNA)
      • One to three phosphate groups

    Nitrogenous Bases

    • Pyrimidines are nitrogenous bases with one carbon-nitrogen ring, including uracil (U), thymine (T), and cytosine (C).
    • Purines are nitrogenous bases with two carbon-nitrogen rings, including adenine (A) and guanine (G).

    DNA and RNA

    • DNA and RNA consist of polynucleotide chains, with one nucleotide linked to the next by a phosphodiester bond.
    • DNA is a double-stranded molecule, with two polynucleotide chains wrapped around each other in a spiral.
    • RNA is typically single-stranded, but can form double-helical regions by folding back on itself.

    Complementary Base Pairing

    • The two polynucleotide chains of a DNA double helix are held together by hydrogen bonds between the base pairs.
    • A base pair consists of one purine and one pyrimidine, with adenine (A) pairing with thymine (T) and guanine (G) pairing with cytosine (C).
    • In RNA, the uracil (U) base takes the place of thymine (T), forming A-U base pairs.

    Organic Molecules

    • Four major classes of organic molecules found in living organisms: carbohydrates, lipids, proteins, and nucleic acids
    • Organic molecules consist of carbon atoms bonded covalently to each other and other atoms, forming molecules of varying sizes

    Hydrocarbons

    • Simplest hydrocarbon is CH4 (methane), consisting of a single carbon atom bonded to four hydrogen atoms
    • More complex hydrocarbons involve two or more carbon atoms arranged in linear unbranched chains, linear branched chains, or ring structures
    • Single and double bonds are found in linear and ring hydrocarbons, while triple bonds are only found in two-carbon hydrocarbons

    Chemical Evolution

    • Resulted in the first forms of life on Earth after the formation of organic molecules
    • Involved reactions between inorganic molecules on primordial Earth and the conditions present at that time
    • Stanley Miller and Harold Urey performed a classic set of experiments in 1953 to simulate chemical evolution and formed several complex organic molecules

    Functional Groups

    • Small, reactive groups of atoms that give larger molecules specific chemical properties
    • Functional groups that frequently enter into biological reactions include the hydroxyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl groups
    • Functional groups are linked by covalent bonds to other atoms in biological molecules, usually carbon atoms

    Isomers

    • Carbons linked to four different atoms or functional groups can take either of two fixed positions with respect to other carbons in a chain, resulting in isomers
    • Isomers that are mirror images of each other are called stereoisomers
    • Structural isomers are two molecules with the same chemical formula but with atoms arranged in different ways

    Macromolecules

    • Carbohydrates, lipids, proteins, and nucleic acids are large polymers assembled from subunit molecules (monomers) into a chain by covalent bonds
    • Polymers are assembled from monomers by dehydration synthesis reactions
    • Breakdown of polymers into monomers occurs by hydrolysis
    • Each type of polymeric biological molecule contains one type of monomer

    Carbohydrates

    • Serve many functions, including energy storage and structural roles
    • Contain only carbon, hydrogen, and oxygen atoms in a ratio of about 1C:2H:1O (CH2O)
    • Monosaccharides contain three to seven carbon atoms
    • Two monosaccharides polymerize to form a disaccharide
    • Carbohydrate polymers with more than 10 linked monosaccharide monomers are called polysaccharides

    Lipids

    • Water-insoluble, primarily nonpolar biological molecules composed mostly of hydrocarbons
    • Three common types of lipid molecules:
      • Neutral lipids are stored and used as an energy source
      • Phospholipids form cell membranes
      • Steroids serve as hormones that regulate cellular activities

    Proteins

    • Perform many vital functions in living organisms, including structural support, enzymatic activity, movement, transport, recognition, and receptor functions
    • Macromolecules composed of amino acid monomers, which contain both an amino and a carboxyl group
    • 20 different amino acids are used to build proteins in all organisms### Peptide Bonds
    • Peptide bonds are covalent bonds that link amino acids into polypeptide chains, which are the subunits of proteins.
    • Peptide bonds are formed through a dehydration synthesis reaction between the -NH2 group of one amino acid and the -COOH group of another amino acid.
    • The growing polypeptide chain has an N-terminal end and a C-terminal end, with new amino acids being linked only to the C-terminal end.

    Protein Structure

    • Primary structure of a protein refers to the precise sequence of amino acids linked together.
    • Changing even a single amino acid can alter the secondary, tertiary, and quaternary structures of a protein, which can affect its biological function.
    • Example: Substitution of a single amino acid in hemoglobin produces an altered form responsible for sickle-cell disease.

    Secondary Structure

    • The amino acid chain is folded into arrangements that form the protein's secondary structure.
    • Two common types of secondary structure are:
      • Alpha (α) helix: a twisted, regular right-hand spiral structure stabilized by regularly spaced hydrogen bonds.
      • Beta (β) sheet: a flat, zigzagging structure formed by side-by-side alignment of β strands, stabilized by hydrogen bonds.

    Tertiary Structure

    • Tertiary structure refers to the overall three-dimensional shape of a protein, which is determined by the positions of secondary structures, disulfide linkages, and hydrogen bonds.
    • Attractions between positively and negatively charged chemical groups, as well as polar and nonpolar associations, also contribute to tertiary structure.
    • Tertiary structure determines a protein's function, including its chemical activity, solubility, and ability to undergo conformational changes.

    Quaternary Structure

    • Quaternary structure refers to the presence and arrangement of two or more polypeptide chains in a protein.
    • Hydrogen bonds, polar and nonpolar attractions, and disulfide linkages hold the multiple polypeptide chains together.
    • Chaperonins promote the correct association of individual amino acid chains and inhibit incorrect formations.

    Denaturation

    • Denaturation is the process of unfolding a protein from its active conformation, causing it to lose its structure and function.
    • Denaturation can be caused by chemicals, changes in pH, or high temperatures.
    • Experiments by Christian Anfinsen showed that breaking the disulfide linkages holding a protein in its functional state caused it to unfold and lose enzyme activity.

    Chaperonins

    • Chaperonins are "guide" proteins that bind temporarily with newly synthesized proteins, directing their conformation towards the correct tertiary structure and inhibiting incorrect arrangements.
    • Chaperonins promote the correct association of individual amino acid chains and inhibit incorrect formations.

    Nucleotides and Nucleic Acids

    • Nucleic acids are macromolecules assembled from repeating monomers called nucleotides.
    • DNA (deoxyribonucleic acid) stores hereditary information responsible for inherited traits in all eukaryotes and prokaryotes.
    • RNA (ribonucleic acid) is the hereditary molecule of another large group of viruses and is involved in protein synthesis.

    Nucleotides

    • A nucleotide consists of three parts linked together by covalent bonds:
      • A nitrogenous base (formed from rings of carbon and nitrogen atoms)
      • A five-carbon, ring-shaped sugar (deoxyribose in DNA or ribose in RNA)
      • One to three phosphate groups

    Nitrogenous Bases

    • Pyrimidines are nitrogenous bases with one carbon-nitrogen ring, including uracil (U), thymine (T), and cytosine (C).
    • Purines are nitrogenous bases with two carbon-nitrogen rings, including adenine (A) and guanine (G).

    DNA and RNA

    • DNA and RNA consist of polynucleotide chains, with one nucleotide linked to the next by a phosphodiester bond.
    • DNA is a double-stranded molecule, with two polynucleotide chains wrapped around each other in a spiral.
    • RNA is typically single-stranded, but can form double-helical regions by folding back on itself.

    Complementary Base Pairing

    • The two polynucleotide chains of a DNA double helix are held together by hydrogen bonds between the base pairs.
    • A base pair consists of one purine and one pyrimidine, with adenine (A) pairing with thymine (T) and guanine (G) pairing with cytosine (C).
    • In RNA, the uracil (U) base takes the place of thymine (T), forming A-U base pairs.

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