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Name ______________________________________________
Date _________________
The Chemistry of Life (Biochemistry)
Homework/Study Guide
Directions: Compare and contrast the following pairs of terms:
- element / compound: __________________________________________________________________________________________
____________________________________________________________________________________________________________________
- ionic bond / covalent bond: ___________________________________________________________________________________
- cohesion / adhesion: __________________________________________________________________________________________
- compound / mixture: __________________________________________________________________________________________
- solvent / solute: ________________________________________________________________________________________________
____________________________________________________________________________________________________________________
- acid / base: _____________________________________________________________________________________________________
- organic compounds / inorganic compounds: ________________________________________________________________
- monosaccharide / polysaccharide: ___________________________________________________________________________
- enzyme / catalyst: ______________________________________________________________________________________________
- saturated fat / unsaturated fat: ________________________________________________________________________________
Vocabulary Review:
____________________________11. The smallest particle of a substance that still retains the properties of that substance. ____________________________12. List the three subatomic particles that compose atoms.
____________________________
____________________________13. The atoms in a compound are held together by chemical bonds. What part of the atom is involved in the bonding process? ____________________________14. This type of bond is formed when electrons are transferred from one atom to another. ____________________________15. This term describes an atom that has lost or gained valence electrons.
____________________________16. This type of bond is formed when electrons are shared between two atoms.
____________________________17. Type of mixture in which the parts are evenly mixed.
____________________________18. Type of mixture in which the parts are unevenly mixed.
____________________________19. What term describes a mixture of water and undissolved materials that are so small they do not settle out? ____________________________20. What term is used to describe “giant molecules”?
____________________________21. List the four groups of organic compounds.
____________________________22. The storage form of excess glucose in plants.
____________________________23. The storage form of excess glucose in animals.
____________________________24. Name of the stringy, fibrous material that serves as a strengthening tissue in the cell walls of plants. ____________________________25. Proteins that speed up chemical reactions inside of cells.
____________________________26. What are the two types of nucleic acids?
- Describe the polarity of a water molecule. ___________________________________________________________________
____________________________________________________________________________________________________________________
- Why is water neutral in pH despite the fact that it produces hydrogen and hydroxide ions? ____________
- Describe what happens when a hydrogen bond is formed. _________________________________________________
- Draw four water molecules that are hydrogen-bonded together. Show the location of the covalent bonds and the location of the hydrogen bonds.
- List three reasons why water is essential for life on Earth.
a) _________________________________________________________________________________________________________________
b) _________________________________________________________________________________________________________________
c) _________________________________________________________________________________________________________________
- What does the pH scale measure? _____________________________________________________________________________
- Describe the roll of buffers in living cells. ____________________________________________________________________
- What characteristics are found in carbon that makes it excellent for the building of organic compounds? _____________________________________________________________________________________________________
____________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________
- What elements compose each of the following types of organic compounds?
a) Carbohydrates: _____________________________________________________________________________________________
b) Lipids: ________________________________________________________________________________________________________
c) Proteins: _____________________________________________________________________________________________________
d) Nucleic Acids: _______________________________________________________________________________________________
- What are the building blocks, or monomers, of each of the groups of organic compounds?
a) Carbohydrates: _____________________________________________________________________________________________
b) Lipids: ________________________________________________________________________________________________________
c) Proteins: _____________________________________________________________________________________________________
d) Nucleic Acids: _______________________________________________________________________________________________
- What is the difference between a saturated and an unsaturated fatty acid? _______________________________
- An amino acid has four parts to its structural formula. The drawing below is an amino acid. Circle and label each of the four distinguishing parts.
_________45. Two or more different atoms are combined in a definite whole number ratio to form a(n): (a) element (b) compound (c) isotope (d) mixture (e) suspension
_________46. Which one of the following is a correct pairing? (a) Proteins: A source of quick energy for the cell. (b) Carbohydrates: Used as the strengthening tissue in plant cell walls. (c) Lipids: Catalyzes the reactions of the cell. (d) Nucleic Acids: Structural component of cell membranes.
_________47. Which of the following elements readily bonds to itself, forming long chains and ringed- structures as a result? (a) hydrogen (b) oxygen (c) nitrogen (d) carbon (e) phosphorus
_________48. The primary function of nucleic acids is: (a) to speed up the chemical reactions of the cell (b) to provide structure to the cell membrane (c) to store energy for use by the cell (d) to store the information needed to build proteins.
Directions: Determine if each of the following statements is true or false. If the
statement is false, correct the underlined word to make the statement
true.
________________________49. A molecule is the basic unit of matter.
________________________50. An atom that loses an electron has a negative charge.
________________________51. An ionic bond is formed due to the attraction of oppositely charged ions.
________________________52. Molecules such as O 2 , H (^) 2 , and N 2 contain nonpolar covalent bonds.
________________________53. A single water molecule can form up to four hydrogen bonds with other water molecules at the same time. ________________________54. Basic solutions have a pH below 7.
________________________55. The lipids are known as the “quick-energy foods” because they are so quickly converted to energy by the cells. ________________________56. A solution is a homogeneous mixture.
________________________57. If you wait long enough the particles of a suspension will eventually settle to the bottom of the container. ________________________58. Large bodies of water regulate temperatures on earth by absorbing heat from the sun during the day, which cools the landmasses. ________________________59. The carbohydrates are classified according to the number of amino acids they contain. ________________________60. The carbohydrates are generally not soluble in water.
________________________61. The lipids are generally not soluble in water.
________________________62. The saturated fats tend to be liquids at room temperatures.
Directions: To which group of organic compounds does each of the following
belong? Use the letters for your answers.
A. Carbohydrates B. Lipids
C. Nucleic Acids D. Proteins
__________63. Enzymes
__________64. Glucose
__________65. Fats and oils
__________66. Cholesterol
__________67. Sugars
__________68. Starch
__________69. Hormones
__________70. Cellulose
__________71. Waxes
__________72. Monosaccharides
__________73. DNA and RNA
__________74. Polysaccharides
__________75. Glycogen
Monomer Identification:
Below are the chemical formulas for the five representative monomers found in living organisms. Identify each one and explain how you know which monomer it is. Explain how each compound is important to the structure and function of living organisms. In other words, what are each of these compounds used for in living systems?
Which monomer is this? ____________________________________________________________________________________
How do you know? __________________________________________________________________________________________
What is the purpose of this compound in living organisms? _____________________________________________
Think About This!
- Formulas of some of the acids include HCl, HNO 3 , and H 2 SO 4. These acids are very soluble in water. What will happen when these acids dissociate in water, and what will be the resulting change in pH of the solution? Be sure to explain your answer.
________________________________________________________________________________________________________________
________________________________________________________________________________________________________________
________________________________________________________________________________________________________________
- Why can the proteins be classified as polymers, but the lipids cannot? ________________________________
- How can a change in pH affect the functioning of an enzyme? Explain in terms of the “lock and key” hypothesis.
- Use a series of drawings to show how an enzyme works.
*** Answer Key***
Directions: Compare and contrast the following pairs of terms:
- An element is a pure substance consisting of all the same type of atom. A compound is the chemical combination of two or more elements in a definite whole-number ratio.
- An ionic bond is formed when one or more electrons are transferred or exchanged from one atom to another. In a covalent bond, electrons are shared between two atoms.
- Cohesion is an attraction between molecules of the same substance. Water molecules stick to each other because of cohesion. Adhesion is an attraction between molecules of different substances. Water sticks to other surfaces and substances because of adhesion.
- A compound is the chemical combination of two or more elements in a definite whole-number ratio. A mixture is a substance composed of two or more elements or compounds that are physically mixed together but are not chemically combined.
- The solute is the substance that is being dissolved in a solution. The solvent is the part of the solution that does the dissolving of the solute.
- An acid is any substance that increases the concentration of hydrogen ions when added to a water solution. A base is any substance that increases the concentration of hydroxide ions when added to a water solution.
- Organic compounds are derived from living organisms. They contain carbon atoms bonded to other carbon atoms. Inorganic substances do not contain carbon atoms bonded to other carbon atoms.
- A monosaccharide is composed of a single sugar molecule. It contains only one molecule of sugar. A polysaccharide is a complex carbohydrate composed of three or more monosaccharides.
- Enzymes are biological catalysts. Enzymes are proteins that speed up the chemical reactions of the cell by lowering the amount of activation energy needed for the reaction. Catalysts are inorganic substances that also lower the activation energy of a reaction, making the reaction take place at a faster rate. Catalysts, unlike enzymes, are not specific for one particular reaction.
- A saturated fat is one that has no carbon-to-carbon double bonds. The long chain of carbon atoms contains single bonds only. As a result, the carbon chain will be “saturated” with hydrogen atoms. An unsaturated fat contains at least one carbon-to-carbon double bond. There will be fewer bonding sites for hydrogen so the fat is “unsaturated.”
d) The molecule become polar. One end of the molecule will be slightly negative, while the other end of the molecule will be slightly positive. e) The atom around which the shared electrons spend the most time will have a slightly negative charge. f) The atom around which the shared electrons spend the least time will have a slightly positive charge. g) Polar Covalent Bond: A covalent bond in which a pair of electrons shared by two atoms is held more closely by one of the atoms. h) Nonpolar Covalent Bond: A covalent bond in which the bonding electrons are equally attracted to both bonded atoms.
In a water molecule, an oxygen atom has a much stronger attraction for shared electrons than does the hydrogen atom. At any given time, there is a greater probability of finding the shared electrons near the oxygen atom than near the hydrogen atom. As a result, the oxygen end of the molecule has a slight negative charge and the hydrogen end of the molecule has a slight positive charge.
In water, the force of attraction between molecules is so strong that the oxygen atom of one water molecule can actually remove the hydrogen atom from another water molecule. This breaking apart of the water molecule into hydrogen ions and hydroxide ions is called dissociation. In a sample of pure water, the number of hydrogen ions will be equal to the number of hydroxide ions, resulting in a neutral pH.
A hydrogen bond is formed when there is an attraction between the hydrogen atom of one molecule to a highly electronegative atom in a different molecule. Water molecules stick together because of hydrogen bonding. In water, the hydrogen of one water molecule is attracted to the oxygen of a different water molecule. A hydrogen bond forms between them.
Reasons water is essential for life on earth: a) Because water is cohesive, the sticking together of water molecules makes water a liquid over a wide range of temperatures. b) Water stabilizes temperatures on Earth. It absorbs heat from the sun during the day to cool the landmasses. It releases heat to the atmosphere at night to warm the landmasses. c) Water is the solvent of life. It is able to dissolve a wide variety of substances.
- The pH scale measures the relative concentrations of hydrogen ions and hydroxide ions in a solution.
- Buffers are substances produced by cells that prevent sharp and sudden changes in pH within the cell.
- Characteristics of carbon: a) Carbon has four valence electrons. It can form four bonds with other carbon atoms as well as to a variety of other elements. b) Carbon forms strong and stable bonds. c) Carbon can form chains that are almost unlimited in size. d) Carbon can form ringed molecules. e) Carbon can form single, double or triple bonds with itself or with other elements. f) The variety of different molecules that can be formed by carbon is almost unlimited.
- a) C, H, O b) C, H, O c) C, H, O, N, and sometimes S d) C, H, O, N, P
- a) simple sugars or monosaccharides b) fatty acids and glycerol c) amino acids d) nucleotides (consisting of a sugar, a phosphate, and a nitrogen base)
- Saturated fats: Contain no carbon-carbon double bonds, so as many hydrogen atoms as possible are bonded to the carbon skeleton. Animal fats are saturated and are solids at room temp.
Unsaturated fats: Contain one or more carbon-carbon double bonds. This will cause a “kink” in the tail wherever a double bond is found. These kinks will prevent the molecules from packing too close together, so they are usually liquids at room temperature.
- True
- False. Correct answer is “simple sugar molecules.”
- False. Correct answer is “lipids.”
- True
- False. Correct answer is “unsaturated.”
Directions: To which group of organic compounds does each of the following
belong? Use the letters for your answers.
63. D
64. A
65. B
66. B
67. A
68. A
69. D
70. A
71. B
72. A
73. C
74. A
75. A
Monomer Identification:
- Which monomer is this? This monomer is a fatty acid.
How do you know? It is easily identified by the very long carbon chain with a carboxyl group at one end.
Purpose? Fatty acids are used to build lipids. In living organisms the functions of lipids include:
- Source of energy
- Phospholipids are used in the building of membranes.
- They form waterproof coverings on feathers, fruits, leaves, exoskeletons, etc.
- They cushion and insulate the organs of the body.
- Which monomer is this? This monomer is glucose.
How do you know? The chemical formula is C (^) 6 H (^) 12 O (^) 6. This is the characteristic CH 2 O ratio seen in the carbohydrates.
Purpose? In living organisms the functions of monosaccharides include:
- Immediate source of energy for the cell.
- To provide the raw materials to build a variety of other molecules.
- Structural purposes, such as cellulose and chitin.
- Which monomer is this? This monomer is glycerol.
How do you know? Although composed of carbon, hydrogen, and oxygen, it does not have the characteristic CH (^) 2 O ratio seen in the carbohydrates. The glycerol molecule is a 3-carbon chain with a hydroxyl group on each carbon.
Purpose? Glycerol is used to build lipids. In living organisms the functions of lipids include:
- Source of energy
- Phospholipids are used in the building of membranes.
- They form waterproof coverings on feathers, fruits, leaves, exoskeletons, etc.
- They cushion and insulate the organs of the body.
- Which monomer is this? This monomer is a nitrogen base.
How do you know? It is a ringed structure with carbon and nitrogen alternating in the ring. Some nitrogen bases are single rings and others have double rings.
Purpose? A nitrogen base is a component used in the building of nucleotides, which are the building blocks of DNA and RNA. Nitrogen bases are also used in molecules of ATP and ADP.
- Which monomer is this? This monomer is an amino acid.
How do you know? It consists of one central carbon. On this carbon are four characteristics units: (1) a carboxyl group, (2) an amino group, (3) a single hydrogen, and (4) an R group.
Purpose? Amino acids are used to build proteins. In living organisms the functions of proteins include:
- Source of energy
- Enzymes
- Hormones
- Transport proteins such as hemoglobin
- Contractile proteins such as in muscle tissues
- Antibodies
- Membrane proteins
- Structural proteins such as bones and muscles
Think About This!
- When these acids dissociate in water , they will release hydrogen ions into the solution. This will cause a decrease in pH and result in an acidic solution.
- A polymer is a compound consisting repeating linked monomers. A protein is a polymer because it consists of many, many amino acids bonded together. A lipid does not have repeating subunits. A lipid is composed of only one molecule of glycerol and three fatty acids.
