Chemistry for Biologists Quiz
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Questions and Answers

What is a dipole in the context of molecular structure?

  • A molecule with a separation of positive and negative charges (correct)
  • A molecule that generates equal charges across its bonds
  • A molecule with no polar bonds
  • A molecule with evenly shared electrons

    • Which statement best differentiates ionic substances from polar substances?

  • Ionic substances contain covalent bonds, while polar substances have ionic bonds.
  • Ionic substances form through covalent sharing of electrons, while polar substances involve ionic bonds.
  • Ionic substances are formed from ionic bonds, while polar substances involve unequal sharing of electrons. (correct)
  • Ionic substances have dipoles, while polar substances do not.

    • Why does water have high melting and boiling points?

  • Because it has a high density when frozen
  • Because it is a nonpolar molecule
  • Because of hydrogen bonding between water molecules (correct)
  • Because it forms strong ionic bonds

    • What role does water's polar nature play in biological systems?

    <p>It makes water a versatile solvent for both covalent and ionic compounds.</p> Signup and view all the answers

    How does water's property of cohesion benefit plants?

    <p>It assists in the upward movement of water in the xylem.</p> Signup and view all the answers

    What effect does the hydrogen bond attraction have on the density of ice compared to liquid water?

    <p>Ice is less dense than liquid water.</p> Signup and view all the answers

    Which characteristic of water contributes to its effectiveness as a stable medium for life?

    <p>Its property of slowly absorbing and releasing heat.</p> Signup and view all the answers

    Which statement about polar molecules is true?

    <p>They demonstrate unequal sharing of electrons leading to slight charges.</p> Signup and view all the answers

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

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

    What is the primary function of polysaccharides in organisms?

    <p>Energy storage</p> Signup and view all the answers

    Which of the following describes the hydrolysis of polysaccharides?

    <p>Addition of water to break down the bonds</p> Signup and view all the answers

    What differentiates amylose from amylopectin?

    <p>Amylopectin has branching at 1,6.</p> Signup and view all the answers

    Which carbohydrate is referred to as 'animal starch'?

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

    How does the breakdown of glucose during cellular respiration primarily generate energy?

    <p>By generating adenosine triphosphate (ATP)</p> Signup and view all the answers

    What characteristic of polysaccharides makes them suitable for energy storage?

    <p>They are physically and chemically inactive.</p> Signup and view all the answers

    What effect do monosaccharides and disaccharides have on osmotic pressure?

    <p>They significantly increase osmotic pressure.</p> Signup and view all the answers

    What is the primary characteristic of an anion?

    <p>It gains electrons.</p> Signup and view all the answers

    Which of the following describes a polar molecule?

    <p>It contains a dipole.</p> Signup and view all the answers

    What is a significant property of hydrogen bonds in water?

    <p>They are weak but require substantial energy to break.</p> Signup and view all the answers

    Which of the following ions is essential for nerve impulses?

    <p>Sodium ion</p> Signup and view all the answers

    What role do bicarbonate ions play in biological systems?

    <p>They assist in blood pH buffering.</p> Signup and view all the answers

    Which of the following best describes ionic bonding?

    <p>It includes the transfer of electrons between atoms.</p> Signup and view all the answers

    How does water's polarity contribute to its role as a solvent?

    <p>It enables the dissociation of ionic substances.</p> Signup and view all the answers

    Which ion is necessary for ATP and ADP production in living organisms?

    <p>Phosphate ion</p> Signup and view all the answers

    What is one reason why water has a high surface tension?

    <p>Because of hydrogen bonding between water molecules.</p> Signup and view all the answers

    In biological systems, magnesium ions are important for what primary function?

    <p>Production of chlorophyll in plants.</p> Signup and view all the answers

    What structure is formed when two amino acids join together?

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

    Which type of bond is primarily responsible for the folding and coiling of proteins?

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

    What is the main characteristic of fibrous proteins compared to globular proteins?

    <p>They form long, parallel chains.</p> Signup and view all the answers

    Which protein structure consists of a sequence of amino acids?

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

    What is the primary function of lipids in the body?

    <p>Acting as a source of energy storage</p> Signup and view all the answers

    What is formed during the condensation reaction that synthesizes triglycerides?

    <p>One molecule of water</p> Signup and view all the answers

    What role do the R groups play in amino acids?

    <p>They influence the interaction between amino acids.</p> Signup and view all the answers

    How do saturated fatty acids differ from unsaturated fatty acids?

    <p>Saturated fatty acids only contain single bonds between carbon atoms</p> Signup and view all the answers

    In which type of protein structure might you find multiple polypeptide chains?

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

    Which type of fatty acid is more likely to be solid at room temperature?

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

    Which of the following best describes a characteristic of globular proteins?

    <p>They fold into spherical shapes.</p> Signup and view all the answers

    What happens to hydrogen bonds in proteins when there are changes in pH or temperature?

    <p>They break easily.</p> Signup and view all the answers

    What are the products of lipid oxidation in the body?

    <p>Water and carbon dioxide</p> Signup and view all the answers

    What type of protein is hemoglobin classified as?

    <p>Both B and C</p> Signup and view all the answers

    Which type of fatty acid has one or more double bonds in its carbon chain?

    <p>Both B and C</p> Signup and view all the answers

    Which type of bond involves an oxidation reaction between sulfur-containing groups?

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

    What is the structure of a triglyceride composed of?

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

    What is the primary function of collagen in the body?

    <p>Providing structural support.</p> Signup and view all the answers

    Which statement is true regarding the formation of ester bonds in lipids?

    <p>Ester bonds are formed by condensation reactions</p> Signup and view all the answers

    Which of the following is a characteristic of a secondary protein structure?

    <p>Repetitive arrangements like α-helices.</p> Signup and view all the answers

    What occurs in a condensation reaction between two amino acids?

    <p>Release of water.</p> Signup and view all the answers

    Which type of lipoprotein is associated with high-density lipoproteins (HDL)?

    <p>Transports cholesterol away from tissues.</p> Signup and view all the answers

    Study Notes

    Chemistry for Biologists

    • Anions are negatively charged ions.
    • Cations are positively charged ions.
    • Ionic bonds form when atoms give or take electrons, resulting in charged particles called ions.
    • A dipole is the separation of charge in a molecule when covalent bonds are not evenly shared.
    • A polar molecule contains a dipole.
    • Dissociation is the splitting of a molecule into smaller molecules, atoms, or ions, especially by a reverse process.
    • Hydrogen bonds are weak electronic intermolecular bonds formed between polar molecules containing at least one hydrogen atom.

    The Chemistry of Life

    • Ionic bonding occurs when atoms give or take electrons.
    • One atom or molecule gains one or more electrons and becomes an anion (negative).
    • The other atom or molecule loses one or more electrons and becomes a cation (positive).
    • Important cations include sodium, calcium, hydrogen ions, and magnesium ions.
    • Important anions include chloride, nitrate, phosphate, and hydrogencarbonate ions.

    The Chemistry of Water

    • Water is essential for life and all reactions in living cells take place in water.
    • Water is a polar molecule because the electrons are held closer to the oxygen atom than to the hydrogen atoms, so the oxygen has a very small negative charge and the hydrogen atoms have very small positive charges.
    • Hydrogen bonds form between water molecules, contributing to its high boiling point.
    • Water is a polar solvent, meaning it can dissolve many ionic substances.
    • Water is slow to absorb heat and to release it, making it a stable medium for life.
    • Water molecules are cohesive, meaning they stick together, and adhesive, meaning they stick to other molecules, both of which are important properties in the movement of water up the xylem of plants.
    • Water molecules have a high surface tension.

    Carbohydrates 1: Monosaccharides and Disaccharides

    • Carbohydrates are made up of carbon, hydrogen, and oxygen.
    • The basic structure of all carbohydrates is the same: they are made up of carbon, hydrogen, and oxygen.
    • There are three main groups of carbohydrates with varying complexity of molecules: monosaccharides, disaccharides, and polysaccharides.
    • A glycosidic bond is formed by the removal of a hydrogen atom (–H) from one monosaccharide and a hydroxyl group (–OH) from another monosaccharide to form a disaccharide and water.

    Carbohydrates 2: Polysaccharides

    • Polysaccharides are the most complex carbohydrates, do not have a sweet taste, and are formed by the joining of many monosaccharides.
    • 3-10 sugar units are known as oligosaccharides, and 11+ are called true polysaccharides.
    • Hydrolysis is the process that breaks down polysaccharides for cellular respiration by adding water to the bond.
    • Monosaccharides and disaccharides provide good sources of instant energy but cannot be stored, while polysaccharides form compact molecules, need less space, are physically and chemically inactive, are not very water soluble, and are for energy storage.
    • Starches are made up of amylose and amylopectin.
    • Amylose is an unbranched chain of glucose molecules linked by 1,4 glycosidic bonds, while amylopectin has both 1,4 and 1,6 glycosidic bonds, making it branched.
    • Glycogen is structured like amylopectin and is referred to as “animal” starch.

    Lipids

    • Lipids are used as an energy store and contain C, H, O (but almost no oxygen).
    • When oxidised, the bonds are broken and the products are H2O and CO2.
    • Triglycerides store almost 3x as much energy as carbohydrates.
    • A triglyceride is formed from one glycerol molecule and three fatty acids.
    • An ester bond is formed by a condensation reaction (esterfication), and broken by hydrolysis.
    • Saturated fats are usually solid at room temperature, while unsaturated fats are usually liquid at room temperature.
    • Saturated fats have single covalent bonds in their fatty acid chains, while unsaturated fats have at least one carbon-carbon double bond.
    • Monounsaturated fats have one carbon-carbon double bond, while polyunsaturated fats have more than one carbon-carbon double bond.
    • Long chain fatty acids are more likely to be solid.

    Proteins

    • Proteins are macromolecules made from smaller monomers called amino acids.
    • They are made up of carbon, hydrogen, oxygen, and nitrogen + sometimes sulfur.
    • Amino acids are joined by a condensation reaction, which results in the loss of water.
    • There are 20 naturally occurring essential amino acids.
    • Each amino acid has an amino group (-NH2) and a carboxyl group (-COOH).
    • The R group is the variable part of an amino acid that influences its properties and how it interacts within a protein molecule.
    • When two amino acids join together, they form a dipeptide, and 3 or more are called polypeptide chains.
    • Polypeptides fold and coil into specific shapes through a series of interactions between the R groups of the amino acids.

    Types of Bonds in Proteins

    • Hydrogen bonds form between slightly negative oxygen and slightly positive hydrogen atoms present in the amino groups of proteins.
    • Disulfide bonds form between two cysteine molecules in a polypeptide through an oxidation reaction between the two sulfur-containing groups.
    • Ionic bonds form between some strongly negative and strongly positive amino acid side chains but are not as common and may be buried deep in the molecule.
    • Heat can break hydrogen bonds in proteins, while perms break disulfide bonds permanently.

    Protein Structures

    • There are four levels of protein structure: primary, secondary, tertiary, and quaternary.
    • The primary structure is the sequence of amino acids that make up a polypeptide.
    • The secondary structure is the regular repeating arrangement of the polypeptide chain, held together by hydrogen bonds, and can be either an alpha helix or a beta pleated sheet.
    • The tertiary structure is the overall 3D shape of a polypeptide chain, made up of alpha helixes and beta pleated sheets, and held together by hydrogen, sulfur, and ionic bonds.
    • The quaternary structure is formed when two or more polypeptide chains associate with each other.

    Fibrous and Globular Proteins

    • Fibrous proteins have little to no tertiary structure and are insoluble in water, such as collagen, keratin, and elastin.
    • Globular proteins fold into spherical shapes and are soluble in water, such as enzymes, antibodies, and hormones.
    • Collagen is an extremely strong fibrous protein found in tendons, ligaments, bones, and skin, formed of three polypeptide chains that wind around one another to form a triple helix.
    • Haemoglobin is a well-known globular protein that transports oxygen in the blood, formed of four polypeptide chains assembled into a quaternary structure with an iron-containing group.

    Conjugated Proteins

    • Conjugated proteins are connected to another molecule, called a prosthetic group.
    • Lipoproteins are formed when proteins are conjugated with lipids and are important for blood cholesterol, including LDL and HDL.
    • Glycoproteins are formed when proteins are conjugated with carbohydrates.

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    Description

    Test your knowledge on key concepts in biochemistry including ionic bonds, anions, cations, and molecular structures. This quiz covers essential topics such as dipoles, dissociation, and hydrogen bonding, crucial for understanding the chemistry of life. Perfect for biology students looking to enhance their chemistry skills!

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