Chemistry Basics: Water and Atomic Structure
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Questions and Answers

What does the atomic number represent in an atom?

  • The total number of protons and neutrons
  • The number of protons and electrons combined
  • The number of electrons
  • The number of protons (correct)

    • What is the significance of columns in the periodic table?

  • They indicate the number of valence electrons (correct)
  • They indicate the number of protons in an atom
  • They represent the total number of electrons in an atom
  • They show how many neutrons are present

    • What is the definition of atomic mass unit (amu)?

  • A unit that measures the total mass of an atom including protons and electrons
  • A unit of measurement that equals 1/12 the mass of a carbon atom (correct)
  • A unit to measure the number of protons in an atom
  • A measurement used for the weight of an element in a gravitational field

    • How does mass differ from weight regarding an object?

    <p>Weight is the measure of gravitational force on an object's mass</p> Signup and view all the answers

    Which statement accurately describes protons and neutrons?

    <p>They are both approximately equal in mass and significantly larger than electrons</p> Signup and view all the answers

    Which statement accurately reflects the First Law of Thermodynamics?

    <p>Energy can be transformed from one form to another.</p> Signup and view all the answers

    What type of energy is stored in the chemical bonds of substances?

    <p>Chemical energy</p> Signup and view all the answers

    What is the role of free energy (G) in chemical reactions?

    <p>It helps define the direction of spontaneous reactions.</p> Signup and view all the answers

    Which of the following best describes potential energy?

    <p>Stored energy due to an object's position.</p> Signup and view all the answers

    Which of the following statements about entropy is true?

    <p>Entropy is a measure of disorder in a system.</p> Signup and view all the answers

    What is a characteristic of spontaneous reactions?

    <p>They proceed naturally with minimal energy input.</p> Signup and view all the answers

    Which of the following is NOT a form of energy?

    <p>Solid energy</p> Signup and view all the answers

    What does the term 'metabolism' refer to?

    <p>The total of all chemical reactions in an organism.</p> Signup and view all the answers

    What characterizes a reaction that is classified as endergonic?

    <p>It requires an input of energy and has a positive ΔG.</p> Signup and view all the answers

    Which statement about the hydrolysis of ATP is correct?

    <p>It has a negative ΔG, indicating it is spontaneous.</p> Signup and view all the answers

    How can an endergonic reaction become thermodynamically favored?

    <p>By coupling it to an exergonic reaction.</p> Signup and view all the answers

    What does a negative ΔG value signify in a chemical reaction?

    <p>The reaction occurs spontaneously and releases energy.</p> Signup and view all the answers

    What happens to photosynthesis in conditions of darkness?

    <p>It does not occur since it is an endergonic process requiring energy.</p> Signup and view all the answers

    What effect does the addition of solutes have on the freezing point of water?

    <p>It lowers the freezing point below 0° Celsius.</p> Signup and view all the answers

    Which of the following statements about acids is correct?

    <p>Acids release hydrogen ions (H+) in solution.</p> Signup and view all the answers

    How do buffers function within biological systems?

    <p>They help maintain a stable pH by removing or releasing H+.</p> Signup and view all the answers

    What is the importance of carbon's four electrons in its outer shell?

    <p>It enables carbon to form up to four covalent bonds.</p> Signup and view all the answers

    Which of the following best describes isomers?

    <p>Two molecules with an identical molecular formula but different structures.</p> Signup and view all the answers

    What is the primary function of carbohydrates in living organisms?

    <p>To serve primarily as a source of energy.</p> Signup and view all the answers

    What type of bond is formed when two monosaccharides join?

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

    How are triglycerides formed?

    <p>By bonding glycerol to three fatty acids.</p> Signup and view all the answers

    What is a characteristic feature of lipids?

    <p>They are predominantly nonpolar and insoluble in water.</p> Signup and view all the answers

    Which of the following sugars is least commonly found in living cells?

    <p>L-glucose</p> Signup and view all the answers

    What defines an alkaline solution on the pH scale?

    <p>pH greater than 8</p> Signup and view all the answers

    What is the process of hydrolysis?

    <p>The addition of water to break down a polymer.</p> Signup and view all the answers

    Which functional group is known for its significance in biological reactions?

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

    What term describes sugars made from two monosaccharides?

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

    What process happens when a phosphate group is transferred from ATP to glucose?

    <p>Substrate-level phosphorylation</p> Signup and view all the answers

    Which statement correctly describes the role of enzymes in chemical reactions?

    <p>They speed up the rate of chemical reactions without being used up.</p> Signup and view all the answers

    What is the term for the concentration of substrate at which the reaction velocity is half of its maximum value?

    <p>Michaelis constant</p> Signup and view all the answers

    Which of the following best describes competitive inhibition?

    <p>Inhibitor binds to the active site, blocking substrate access.</p> Signup and view all the answers

    How do enzymes lower the activation energy of a reaction?

    <p>By positioning reactants together and straining bonds.</p> Signup and view all the answers

    What type of metabolic pathway is responsible for building larger molecules from smaller ones?

    <p>Anabolic pathway</p> Signup and view all the answers

    What is the primary role of electron carriers in cellular respiration?

    <p>To transfer electrons between molecules.</p> Signup and view all the answers

    What does the term 'allosteric site' signify in enzymes?

    <p>The site where inhibitors can change enzyme shape.</p> Signup and view all the answers

    What is a common requirement for optimal enzyme activity?

    <p>A narrow range of temperature and pH.</p> Signup and view all the answers

    Which of the following describes the process of chemiosmosis?

    <p>Energy from an electrochemical gradient for ATP production.</p> Signup and view all the answers

    What occurs during the process of autophagy in cells?

    <p>Recycling worn-out organelles.</p> Signup and view all the answers

    What mechanism do cells employ to ensure they do not overproduce organic molecules?

    <p>Metabolic feedback</p> Signup and view all the answers

    What role do prosthetic groups play in enzyme function?

    <p>They assist enzyme functions permanently.</p> Signup and view all the answers

    Which type of reaction is characterized by the addition of electrons?

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

    Study Notes

    Water

    • Water (H2O) is a molecule composed of two hydrogen atoms and one oxygen atom.
    • The number of protons in an atom determines its element.
    • The atomic number is equal to the number of protons in an atom.
    • It is also equal to the number of electrons in an atom, resulting in a neutral charge.
    • The periodic table organizes elements by atomic number.
    • Rows indicate the number of electron shells.
    • Columns represent the number of electrons in the outer shell, known as valence electrons.
    • Elements in the same column have similar chemical properties due to the same number of valence electrons.
    • Atomic mass is the mass of an atom compared to the mass of other atoms.
    • The atomic mass scale is based on carbon-12, which has six protons and six neutrons.
    • The mass of an atom is primarily attributed to protons and neutrons, which are much heavier than electrons.
    • Weight is the force exerted on an object due to gravity.
    • Mass remains constant regardless of location, but weight changes depending on gravitational force.

    Units

    • Dalton (Da) is the unit of measurement for atomic mass.
    • One Dalton is equal to 1/12 the mass of a carbon atom.

    Water as a Solvent

    • Water is a highly effective solvent due to its polarity.
    • The addition of solutes to water lowers its freezing point and raises its boiling point.
    • Antifreeze, like ethylene glycol, lowers the freezing point of water to prevent freezing in cold weather.

    Water's Biological Roles

    • Water participates in chemical reactions, such as hydrolysis and condensation.
    • Provides structural support and force.
    • Removes toxic waste components.
    • Facilitates evaporative cooling.
    • Exhibits cohesion (attraction between similar molecules) and adhesion (attraction between different molecules).
    • Creates surface tension, a measure of the attraction between molecules at the liquid surface.
    • Acts as a lubricant.

    Acids and Bases

    • Pure water ionizes slightly into hydrogen ions (H+) and hydroxide ions (OH-).
    • Acids release hydrogen ions (H+) in solution, with strong acids releasing more H+ than weak acids.
    • Bases lower the H+ concentration by releasing hydroxide ions (OH-) or binding H+.

    pH Scale

    • The pH scale measures the acidity or alkalinity of a solution.
    • pH = -log10(H+).
    • Acidic solutions have a pH below 7.
    • Neutral solutions have a pH of 7.
    • Alkaline (basic) solutions have a pH above 7.

    Effects of pH

    • pH influences the shape and function of molecules.
    • Affects the rate of chemical reactions.
    • Determines the ability of molecules to bind to each other.
    • Influences the solubility of ions and molecules in water.

    Buffers

    • Buffers help maintain a constant pH in biological systems.
    • Acid-base buffer systems can shift to remove or release H+ to adjust for changes in pH.

    Carbon Atom

    • Organic molecules contain carbon.
    • Organic molecules are abundant in living organisms.
    • Macromolecules are large, complex organic molecules.

    Organic Chemistry

    • The science of carbon-containing molecules.
    • Vitalism was a 19th-century concept that organic molecules were created by a life force within living organisms.
    • Vitalism was later disproven as organic molecules can be synthesized.

    Carbon Properties

    • Carbon has four electrons in its outer shell and needs four more to fill it.
    • It can form up to four bonds, usually single or double bonds.
    • Carbon can form both nonpolar and polar bonds.
    • Molecules with polar bonds are water-soluble, while nonpolar molecules are not.

    Functional Groups

    • Groups of atoms with specific chemical features that contribute to the molecule's function.
    • Each functional group exhibits the same properties in all molecules it occurs in.

    Isomers

    • Molecules with the same molecular formula but different structures and properties.
    • Structural isomers have the same atoms but different bonding relationships.
    • Stereoisomers have identical bonding relationships but differ in spatial positioning.
    • Cis-trans isomers differ in positioning around a double bond.
    • Enantiomers are mirror-image molecules with different binding abilities.

    Synthesis and Breakdown of Organic Molecules

    • Macromolecules are formed by linking monomers to create polymers.
    • Condensation reactions form polymers by removing a water molecule with each monomer addition.
    • Hydrolysis reactions break down polymers by adding a water molecule with each monomer release.

    Four Major Classes of Organic Molecules

    • Carbohydrates: Composed of carbon, hydrogen, and oxygen atoms, with many carbon atoms linked to a hydrogen atom and a hydroxyl group.
    • Lipids: Predominantly composed of hydrogen and carbon atoms, with some oxygen. Nonpolar and insoluble in water. Include fats, phospholipids, steroids, and waxes.
    • Proteins: Polymers of amino acids, crucial for biological processes.
    • Nucleic acids: Polymers of nucleotides that store and transmit genetic information.

    Carbohydrates

    • Monosaccharides are simple sugars, like glucose.
    • Disaccharides are composed of two monosaccharides linked by a glycosidic bond.
    • Polysaccharides are long polymers of monosaccharides, like starch, glycogen, cellulose, and chitin.

    Lipids

    • Fats (triglycerides) are formed by bonding glycerol to three fatty acids, linked by ester bonds.

    Metabolism

    • Chemical reactions within an organism.
    • Metabolism includes anabolic pathways (building cellular components) and catabolic pathways (breaking down cellular components).
    • Matter is anything that takes up space and has mass.
    • Energy is the ability to do work and has no mass.
    • Kinetic energy is energy in motion.
    • Potential energy is stored energy.
    • Chemical energy is stored in the bonds of molecules.
    • Electrical energy results from the movement of charged particles.
    • Mechanical energy directly moves matter.
    • Radiant energy travels in waves, like electromagnetic radiation.
    • Thermodynamics is the study of energy interconversions.

    Thermodynamics

    • The first law of thermodynamics states that energy cannot be created or destroyed, only transformed.
    • The second law of thermodynamics states that energy transfer increases entropy (disorder) in a system.
    • Entropy increases with each energy transformation, making less energy available for work.
    • Free energy (G) is the amount of energy available to do work.

    Change in Free Energy

    • The change in free energy (ΔG) determines the direction of chemical reactions.
    • Exergonic reactions release energy (ΔG < 0) and are spontaneous.
    • Endergonic reactions require energy (ΔG > 0) and are non-spontaneous.

    ATP Hydrolysis

    • ATP hydrolysis is an exergonic reaction with ΔG = -7.3 kcal/mole, making it spontaneous.
    • Cells use ATP hydrolysis to drive endergonic reactions.

    Coupled Reactions

    • Endergonic reactions can be coupled with exergonic reactions to make the overall reaction spontaneous.

    Enzymes

    • Catalysts that speed up chemical reactions without being consumed.
    • Act as biological catalysts.
    • Bind to substrates at the active site to catalyze reactions.
    • Suffix "-ase" often indicates an enzyme.
    • Enzymes lower activation energy by straining bonds, positioning reactants, or promoting collisions.
    • The active site is where the reaction takes place.
    • Substrates are the reactants that bind to the active site.
    • An enzyme-substrate complex forms when the enzyme and substrate bind.
    • Affinity is the strength of attraction between an enzyme and its substrate.
    • Saturation occurs when nearly all active sites are occupied by substrate.
    • The Michaelis constant (Km) is the substrate concentration required for half-maximal velocity.
    • Enzyme inhibitors can block or reduce enzyme activity.
    • Competitive inhibition occurs when the inhibitor binds to the active site, preventing substrate binding.
    • Noncompetitive inhibition occurs when the inhibitor binds to a site other than the active site, changing the enzyme's shape.
    • Prosthetic groups are small molecules permanently attached to the enzyme that aid in its function.
    • Cofactors are inorganic ions that temporarily bind to the enzyme to facilitate a reaction.
    • Coenzymes are organic molecules that participate in reactions without being permanently changed.
    • Most enzymes function optimally within a narrow range of temperature and pH.

    Metabolism

    • Chemical reactions occur in metabolic pathways, each coordinated by specific enzymes.
    • Anabolic pathways synthesize cellular components and are endergonic.
    • Catabolic pathways break down cellular components and are exergonic.

    Building Large Molecules (Anabolic)

    • Anabolic reactions involve building larger molecules from smaller ones, like protein synthesis.

    Catabolic Reactions

    • Catabolic reactions involve breaking down reactants, used for recycling building blocks and generating energy to drive endergonic reactions.
    • Catabolic pathways produce energy-storing intermediates like NADH and ATP.

    Two Ways to Make ATP

    • Substrate-level phosphorylation: An enzyme directly transfers a phosphate from one molecule to another.
    • Chemiosmosis: Energy stored in an electrochemical gradient is used to make ATP from ADP and Pi.

    Cellular Respiration and ETC

    • Cellular respiration is a metabolic process to generate energy (ATP).
    • Electron carriers (like NAD+ and FAD) shuttle electrons between molecules.
    • Redox reactions involve the transfer of electrons, where oxidation is the removal of electrons and reduction is the addition of electrons.
    • Cellular respiration involves multiple redox reactions.

    Regulation of Metabolic Pathways

    • Cells regulate metabolic pathways to ensure efficient use of resources.
    • Catabolic pathways are regulated to break down organic molecules only when needed or when energy is required.
    • Anabolic pathways are regulated to synthesize molecules only when needed.
    • Gene regulation controls the expression of genes encoding for enzymes.
    • Cellular regulation involves cell signaling pathways, like hormones.
    • Biomechanical regulation uses feedback inhibition, where the product of a pathway inhibits early steps to prevent accumulation.

    Recycling of Organic Molecules

    • Most large molecules have a relatively short lifespan.
    • Half-life is the time it takes for 50% of molecules to be broken down and recycled.
    • Organisms must efficiently use and recycle organic molecules.

    Proteasome

    • A large complex that breaks down proteins using proteases.
    • Proteases cleave bonds between amino acids.
    • Ubiquitin tags target proteins for degradation.
    • Degrades misfolded proteins and quickly degrades proteins in response to changing conditions.

    Lysosomes

    • Contain hydrolases for breaking down proteins, carbohydrates, nucleic acids, and lipids.
    • Digest substances taken up by endocytosis.
    • Autophagy involves recycling worn-out organelles using an autophagosome.

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