1 Organic Molecules and Water 1. In most animal cells, a complex network of proteins provides which of the following? A. organization B. shape C. movement D. all of these 2. Technology Enhanced Questions are not available in Word format. 3. All living organisms contain carbon atoms. Which of the following is an important characteristic of carbon? Carbon atoms are highly reactive and form unstable bonds with any available atom. A. Carbon atoms can bond with any other atom, but they cannot form bonds with other carbon atoms. B. Carbon atoms are very stable and do not easily form bonds with other atoms. C. Carbon atoms can bond with many other kinds of atoms to form very stable molecules. D. 4. Sugars such as glucose, fructose, and ribose are examples of. A. proteins B. nucleic acids C. lipids D. carbohydrates
2 5. Nucleic acids, proteins, and other large biological molecules are known as polymers because A. they are the base units used in the formation of plastics. B. they all contain only ionic bonds. C. they contain many small, repeating subunits bonded together. D. they all have the capability of functioning as enzymes. 6. Carbohydrates are composed of which three elements? A. oxygen, sulfur, and phosphorus B. carbon, nitrogen, and phosphorus C. carbon, hydrogen, and oxygen D. oxygen, hydrogen, and nitrogen
3 7. Nucleic acids are biological polymers that are comprised of nucleotide monomers covalently bonded together. The picture above shows two monomer units of a nucleic acid chain. What are the components that make up each nucleotide monomer? A. glucose, a phophate group, and an amino acid B. a five-carbon sugar, a phosphate group, and an amino acid C. a five-carbon sugar, a phosphate group, and a nitrogenous base D. glucose, a phosphate group, and a nitrogenous base 8. Organic macromolecules called are insoluble in water, are often found in biological membranes and other waterproof coverings, and have the ability to store energy for extended periods of time. A. proteins B. nucleic acids C. lipids D. carbohydrates
4 9. Lipids are organic macromolecules that serve a variety of purposes. What is the most important role of lipids? A. to build muscles B. to metabolize sugar C. to oxygenate blood D. to store energy 10. Which of the following best describes a carbohydrate? A. B. C. D. Carbohydrates are composed of amino acid monomers and are involved in cell signaling, cell transport, immune responses, and the cell cycle. Carbohydrates are organic macromolecules that are insoluble in water and have the ability to store energy for extended periods of time. Carbohydrates always consist of a five-carbon sugar, a nitrogenous base, and one or more phosphate groups and are used to store genetic information. Carbohydrates are organic macromolecules that are made up of carbon, hydrogen, and oxygen atoms and are used for energy storage or as structural molecules. 11. Which of the following are examples of nucleic acids? A. saturated fats and unsaturated fats B. DNA and RNA C. glucose and starch D. collagen and keratin
5 12. All living things contain carbon. Which of the following statements are true about carbon atoms? I. Each carbon atom can form single bonds with up to four other carbon atoms. II. Each carbon atom can form double bonds with up to two other carbon atoms. III. Carbon atoms can join together to form chains or rings. IV. A single molecule of some compounds can contain thousands of carbon atoms. A. II and III only B. I and III only C. I, II, and III only D. I, II, III, and IV 13. A is a kind of lipid that can store energy for a long period of time. These lipids are made up of long chains of carbon and oxygen atoms bonded to a backbone structure. A. protein B. carbohydrate C. fat D. nucleic acid 14. Technology Enhanced Questions are not available in Word format. 15. A large carbohydrate molecule is composed of several subunits, such as glucose. An example of a large carbohydrate molecule is. A. glycogen B. starch C. cellulose D. all of these
6 16. Which of the following is true about protein molecules? Protein molecules are made up of strands of DNA joined together by amino acid sequences. A. The shape and folded structure of a protein molecule are important in determining its function. B. The sequence of amino acids that make up a protein molecule do not affect its function. C. Protein molecules have many functions in the body, including the storage of genetic information. D. 17. Carbohydrates, such as glucose, are excellent sources of immediate energy for living organisms. More complex carbohydrates, such as glycogen and starch, can also be used for the long term storage of energy. However, carbohydrates play other vital roles, too. Which of the following describes another common use for carbohydrates? A. Enzymes help speed up metabolic reactions. B. Keratin provides support in hair, nails, feathers, hooves, and some animal shells. C. Cellulose is used as a structural component in plant cell walls. D. Collagen is a major component in cartilage and tendons. 18. Carbon atoms have four electrons in their outer shell. This means that a single carbon atom can form up to bonds with other atoms. A. eight B. two C. six D. four 19. What role do ATP and NADH play in living cells? A. They provide structural support to cell membranes. B. They are involved in cell-to-cell signaling. C. They also store and transfer information. D. They store and transfer energy. 20. Protein molecules are composed of long chains of. A. amino acids B. DNA C. RNA D. ribosomes
7 21. Water is the most abundant molecule found in living organisms. Most mammals, in fact, are approximately 70% water by weight. About two-thirds of this water is present inside cells. The other one-third is present outside cells (e.g., in blood plasma or other body fluids). Why is water so important to cells? A. Water is stored in the cells to be used when the organism gets thirsty. B. The main structural component found in plasma membranes and cell walls is water. C. Almost all the chemical reactions in life processes occur in solutions with water. D. Water determines which proteins are translated from the cellular DNA. 22. Nitrogen atoms are part of the structure of some organic molecules, such as all amino acids and some modified carbohydrates. What other organic molecules contain nitrogen? A. cellulose B. fatty acids C. nucleotides D. starch
8 23. Examine the diagram of the enzyme below: How does the structure of this enzyme help with its function? A. Since the enzyme is larger than the substrate, catalytic reactions can occur within the enzyme itself. B. The enzyme's shape complements the substrate's shape, so it only catalyzes specific reactions. C. Since the enzyme's shape matches the substrate's shape, it catalyzes only reverse reactions. D. The enzyme's active site is amorphous and can change its shape to fit any substrate. 24. Monosaccharides are the simplest form of carbohydrates. They can be combined to form more complex carbohydrates known as polysaccharides, which are typically used for long term energy storage within a cell. Based on the information above, it can be concluded that complex organic molecules cannot contain more than one carbon atom. A. simple organic molecules are not necessary for the life processes of an organism. B. simple organic molecules can be organized into much longer, more complex molecules. C. complex organic molecules can only be formed by the polymerization of inorganic molecules. D.
9 25. Cellular processes are carried out by many different types of molecules, mostly proteins. The function of each protein molecule depends on its shape which, in turn, is determined by the protein's specific sequence of. A. triglycerides B. amino acids C. nucleotides D. monosaccharides 26. Water is important to plant cells because it is used as one of the reactants in the process of photosynthesis. What is another reason why water is important to plant cells? A. Water is a major structural component found in plant cell walls. B. Water signals plant DNA to start transcription and translation. C. Water can be used as a substitute for glucose in times of distress. D. Water helps to maintain turgidity in plant cells. 27. The characteristics of all organisms and viruses are determined by the instructions carried in. A. hydrogen bonds B. nucleic acids C. phosphoric acids D. sugar bases 28. Nucleic acids are one of the four major macromolecules. The main functions of nucleic acids are to A. act as enzymes, cell signals, and structural support for the cell. B. store and transport energy and structural components in the cell. C. aid in development, the immune system, and blood clotting. D. carry genetic material and create structures inside the cell.
10 29. Suppose that the temperature in the ecosystem below dips below freezing. What would happen to the fish swimming in the lake? A. Ice would form on the surface of the lake and insulate the fish. B. Ice would only form on the bottom of the lake, so the fish would be okay. C. The fish would die because the lake would freeze solid. D. The fish would move more rapidly to increase their body temperature. 30. A student is given a small amount of unknown tan-colored liquid substance. This unknown liquid is placed into a glass of water and mixed. Despite mixing, the tan liquid remains separated from the water and collects as a large droplet at the top. Which of the macromolecule groups is this liquid MOST likely to be a member of? A. proteins B. nucleic acids C. lipids D. carbohydrates Answers 1. D D 4. D 5. C 6. C 7. C 8. C 9. D 10. D 11. B 12. D 13. C D 16. B 17. C 18. D 19. D 20. A 21. C
11 22. C 23. B 24. C 25. B 26. D 27. B 28. D 29. A 30. C Explanations 1. In most animal cells, a complex network of proteins provides organization, shape, and movement. In all cells, other than very primitive ones, the network of proteins provides organization and shape. Most of these structural proteins that provide organization and shape are fibrous proteins, such as actin and tubulin. Most of the motor proteins are made up of myosin and kinesin Carbon atoms can bond with many other kinds of atoms to form very stable molecules. This is because carbon atoms have four electrons in their outer shells, and all four are available for bonding. Carbon can share these electrons in single bonds with up to four other atoms to form very stable structures. Alternatively, carbon can form double bonds with up to two other atoms by sharing two electrons with each. Carbon can also form a combination of double and single bonds, as long as no more than four electrons are donated. 4. Sugars such as glucose, fructose, and ribose are all examples of monosaccharides, or simple carbohydrates. Carbohydrates are organic macromolecules that are made up of carbon, hydrogen, and oxygen atoms. These atoms are combined in a ratio of 1 carbon atom : 2 hydrogen atoms : 1 oxygen atom Simple carbohydrates can bond together to make polysaccharides, or larger, more complex carbohydrates, such as starch or cellulose. Carbohydrates are typically used for energy storage or as structural molecules. 5. Nucleic acids, proteins, and other large biological molecules are known as polymers because they contain many small, repeating subunits bonded together. For example, proteins contain many amino acid monomers covalently bonded together, and nucleic acids contain many nucleotide monomers covalently bonded together. 6. Carbohydrates, like sugars and starches, are composed of carbon, hydrogen, and oxygen. 7. Nucleotide monomers contain a five-carbon sugar, a phosphate group, and a nitrogenous base. In DNA, the five-carbon sugar is deoxyribose and the nitrogenous base could be adenine, thymine, cytosine, or guanine. In RNA, the five-carbon sugar is ribose and the nitrogenous base could be adenine, uracil, cytosine, or guanine.
12 Glucose is a six-carbon sugar found in other biological polymers like starch and cellulose. Amino acids are the monomer units of proteins. 8. Organic macromolecules called lipids are insoluble in water which is why lipids are often found in biological membranes and other waterproof coverings. Lipids also play a vital role in insulation, regulating which substances can or cannot enter a cell, and they have the ability to store energy for extended periods of time. 9. Lipids are found as structural components of cell membranes and can also serve as signaling molecules. Their most important role, however, is to store energy. In fact, lipids store over twice as much energy (9 kcal/gram) as carbohydrates or proteins (4 kcal/gram). 10. Carbohydrates are organic macromolecules that are made up of carbon, hydrogen, and oxygen atoms. These atoms are combined in a ratio of 1 carbon atom : 2 hydrogen atoms : 1 oxygen atom Carbohydrates may be simple or complex and are typically used for energy storage or as structural molecules. Examples of carbohydrates include glucose, cellulose, starch, and fructose. 11. There are two main types of nucleic acids - ribonucleic acids (RNA) and deoxyribonucleic acids (DNA). These nucleic acids are different because their five-carbon sugars are different. RNA contains ribose, and DNA contains deoxyribose. DNA and RNA also have different functions. DNA stores genetic information and encodes the sequences of all the cell's proteins whereas RNA is involved in the direct production of the proteins. 12. Carbon atoms have four electrons in their outer shells, and all four are available for bonding. Carbon can share these electrons in single bonds with up to four other atoms. Alternatively, carbon can form double bonds with up to two other atoms by sharing two electrons with each. Or, carbon can instead form a combination of double and single bonds, so long as it donates no more than four electrons. As a result of carbon's ability to bond with itself, carbon atoms can form chain-shaped or ring-shaped molecules. The backbones of carbon molecules can be of any size and may contain from one carbon atom to thousands of carbon atoms. 13. A fat is a kind of lipid that can store energy for a long period of time. Fats are made up of long chains of carbon and oxygen atoms bonded to a backbone structure. This backbone structure is often glycerol. Fats are important because they are a major source of energy. Since they contain even more carbon-hydrogen bonds than carbohydrates, fatty tissue has the ability to store energy for extended periods of time Polysaccharides, or large carbohydrate molecules, are polymers that are made up of monosaccharide subunits. Starch, cellulose, and glycogen are all examples of large carbohydrate molecules. Starch, cellulose, and glycogen are all composed of glucose subunits linked in different ways. Starches have branched chains of glucose subunits and are used as food storage for plants. Glycogen has more highly branched chains of glucose than starch and is used by animals instead of plants. Cellulose is a mostly straight chain of glucose subunits and is used to form the cell wall of plants. 16. Protein molecules are composed of long chains of amino acids and perform many functions in the human body. The function of a protein molecule is determined by the sequence of its amino acids and its shape/folded structure.
13 Proteins do not, however, store genetic information. Genetic information is stored by sequences of DNA. 17. In addition to being an energy source for living organisms, carbohydrates play a structural role, as well. Cellulose, for example, is a carbohydrate found in plant cell walls. Keratin, collagen, and enzymes are all examples of proteins, not carbohydrates. 18. Carbon atoms have four electrons in their outer shells, and all four are available for bonding. Carbon can share these electrons in single bonds with up to four other atoms to form very stable structures. Alternatively, carbon can form double bonds with up to two other atoms by sharing two electrons with each. Carbon can also form a combination of double and single bonds, as long as no more than four electrons are donated. 19. ATP is a monomeric nucleotide with three consecutive phosphate groups attached rather than one. These phosphate groups are joined by high energy phosphate-to-oxygen-to-phosphate covalent bonds that can provide energy to activities in the cell that need energy. NADH is a dinucleotide molecule that can store energy obtained from the breakdown of food molecules. This energy will later be transferred to a series of molecules to synthesize more ATP when cells need it. 20. There are over 20 different kinds of amino acids, which, when connected in long chains, form protein molecules. These long chains are usually folded into specific conformations. The sequence of amino acids and the shape of the chain are a result of attractions between the chain's parts. 21. Water is an extremely important molecule to cells because almost all the chemical reactions in life processes occur in solutions with water. Without water, processes such as photosynthesis and cellular respiration, or even simpler processes such as diffusion and osmosis, could not occur. Also, cells would be unable to manufacture and transport ATP to provide energy for the organism. Water is an essential molecule to all living things. 22. All nucleotides are made up of three component compounds: a 5-carbon sugar (ribose or deoxyribose), a phosphate group, and a nitrogenous base. The nitrogenous bases are a group of compounds with a complex one- or two-ring structure made up of carbon and nitrogen atoms in single and double bond combinations. 23. The shape of an enzyme determines how it works. Most enzymes have a surface with one or more deep folds. The folds make pockets which are called active sites. The active sites match folds in the substrate's surface, like a key matches a lock, so the enzyme only catalyzes specific reactions. Once an enzyme binds to a substrate, the amount of energy needed to start a chemical reaction with the substrate is reduced. 24. Carbohydrates may be simple or complex. Simple carbohydrates are also known as monosaccharides. Sugars such as glucose, fructose, and ribose are all examples of monosaccharides. Monosaccharides can be combined to form more complex carbohydrates known as polysaccharides. Glycogen, starch, and cellulose are all examples of polysaccharides. These compounds are typically used for long term energy storage or as structural molecules.
14 Therefore, it can be concluded that simple organic molecules can be organized into much longer, more complex molecules. 25. Amino acids are the monomers of proteins. The function of a protein depends on its shape which is determined by the protein's specific sequence of amino acids. These sequences of amino acids are, in turn, coded by the sequences of nucleotides in the organism's DNA. 26. Plant cells must retain their turgidity, or rigid structure, in order to effectively undergo photosynthesis, because if a plant's stems or leaves wilt, the surfaces of the leaves will not be able to properly absorb energy from the Sun. Inside of plant cells are large vacuoles that hold water. These vacuoles can take up 30-90% of the total volume of the plant cell. The water in these vacuoles helps to maintain turgidity in the plant cells. 27. The characteristics of all organisms and viruses are determined by the instructions carried in nucleic acids. The most common nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The chemical and structural properties of nucleic acids determine how the genetic information that underlies heredity is both encoded in genes and replicated. 28. The main functions of nucleic acids are to carry genetic material and create structures inside the cell. A nucleic acid is a macromolecule that is made up of chains of nucleotides. The two main types of nucleic acids are DNA and RNA. 29. Most solids are more dense than their liquid forms. Ice, however, is unique in that it is less dense than liquid water and is able to float on surfaces of bodies of water, such as lakes and oceans. When ice forms on the surfaces of lakes and oceans, it serves as a layer of insulation. This prevents the water bodies from freezing solid and also protects organisms, such as fish, that live within them. 30. Carbohydrates and nucleic acids are extremely polar due to the large number of oxygen atoms in these organic molecules. Polar organic molecules are able to form hydrogen bonds with the polar water molecules, allowing them to dissolve easily in water. In contrast, lipids have very little oxygen, and are mainly nonpolar. Also, lipids are less dense than water. Due to these two characteristics, the lipids form a layer above the water in the mixture.