Biological macromolecules:

  1. Which of the following biological macromolecules is correctly paired with one of its functions?
    1. Proteins  – Provide cell structure.
      1. Proteins are important macromolecules that play a role in maintaining cell structure. They are also important for cell signaling and catalyzing reactions, and they are crucial in the endocrine and immune systems as hormones and antibodies.
  2. Which part of the nucleotides’ structure is responsible for the incredible variation that exists amongst all types of organisms?
    1. Nitrogenous base
      1. DNA consists of four unique nucleotides that each contain one unique nitrogenous base—adenine (A), thymine (T), cytosine (C), or guanine (G). The specific arrangement of these four bases within the DNA of each organism gives that organism its unique traits.
  3. Which of the following describes the role of lipids?
    1. Membrane structure
      1. Special lipids called phospholipids make up the cell membrane. Proteins and carbohydrates also play a role in membrane structure, as they are embedded between the phospholipids.
    2. Energy storage
      1. Lipids are the cell’s source of long-term energy storage. Carbohydrates also play a role in energy storage, though they act as a short-term energy supply.
  4. Which of the following monomers are correctly matched with their polymers?
    1. Monosaccharides – polysaccharides
      1. Monosaccharides are the monomers that make up polysaccharides (carbohydrates).
  5. Which of the following best describes the molecular structure of albumin?
    1. A folded chain of amino acids
      1. Albumin is a protein. Since the monomers of proteins are amino acids, albumin must be made of amino acids.
  6. What are the repeating subunits that make up a nucleic acid?
    1. Nucleotides – Nucleotides are the monomers of nucleic acids.
  7. Which of the following macromolecules is matched with its correct role in the cell?
    1. Lipid — chemical messenger
      1. Lipids, such as the sex hormone testosterone (type of steroid), can act as chemical messengers throughout an organism’s body.
  8. Which monomer serves as the building block of glycogen, a polymer made up of many glucose molecules?
    1. Monosaccharide
      1. Monosaccharides are the building blocks of sugars and contain carbon, hydrogen, and oxygen in their molecular formula.
  9. Which part of an amino acid’s basic structure gives it its unique functional characteristics?
    1. R-group
      1. There are 20 unique R-groups which differentiate and define the 20 unique amino acids from one another. Amino acids can be arranged on the basis of their R-group’s characteristics.
  10. Which of the following statements is most true regarding macromolecules and their functions?
    1. Nucleic acids store genetic information that codes for traits. Nucleic acids are biological macromolecules that carry genetic information that is passed on from parent to offspring. They contain the “blueprints” needed to make proteins that result in different traits.
  11. A biological macromolecule is made up of glycerol and fatty acids. Based on this information, what type of molecule is this?
    1. Lipid – Glycerol and fatty acids are the building blocks of lipids, so this molecule must be a lipid.
  12. Which of the following is a primary function of carbohydrates?
    1. Providing short-term energy storage
      1. Carbohydrates are the main energy source of cells, acting as a quick energy supply for cellular activities.

Lipids:

  1. Which of the following is a characteristic of lipids?
    1. They are not soluble in water.
      1. Lipids are nonpolar molecules.
      2. Lipids tend to be hydrophobic and therefore insoluble in water.
      3. Lipids are generally composed of hydrocarbon chains.
      4. Lipids can be fats and oils, but they can take other forms, such as waxes.
  2. What are the components of a triglyceride molecule?
    1. One glycerol and three fatty acids.
      1. Triglycerides contain one glycerol and three fatty acid tails. The fatty acid tails may be identical or different (with different lengths or patterns of double bonds).
  3. Which of the following occurs when hydrogen is reacted with vegetable oil?
    1. The hydrogenated vegetable oil will become solid at room temperature.
      1. When hydrogenated, the oil will be solid at room temperature. This process of hydrogenation creates trans fats, which can result in many health problems.
      2. The vegetable oil will remain unsaturated, but the hydrogenation will cause some of the double bonds to become single bonds. This give the oils some of the desirable properties of saturated fats, such as solidity at room temperature.
  4. How are triglycerides formed?
    1. Triglycerides are formed through dehydration synthesis, which results in the loss of H2O.
      1. Triglycerides are produced during dehydration synthesis when the hydroxyl groups on the glycerol backbone react with the carboxyl groups of fatty acids. During this reaction, water molecules are lost, resulting in a triglyceride with three fatty acid tails bound to the glycerol backbone via ester linkages.
  5. Why is butter a solid at room temperature, while vegetable oil is a liquid?
    1. Butter is a saturated fat and vegetable oil is an unsaturated fat.
      1. Butter is a saturated fat, meaning its molecules can pack closely together because they do not have a kink. This makes it easier to solidify than vegetable oil, which is an unsaturated fat and has a kink that makes its molecules less likely to pack together.
      2. Saturated fats, like butter, are solid at room temperature and unsaturated fats, like vegetable oil, are liquids at room temperature.
      3. Both butter and vegetable oil are lipids, so they are nonpolar molecules.
      4. The vegetable oil will remain unsaturated, but the hydrogenation will cause some of the double bonds to become single bonds. This give the oils some of the desirable properties of saturated fats, such as solidity at room temperature.
      5. Adding hydrogen actually will create trans fats.

Proteins:

  1. Which of the following are functions of proteins?
    1. Cell signaling – Many proteins are involved in cell signaling. For example, hormones are proteins that act as chemical signals, controlling specific processes, such as growth, development, metabolism, and reproduction.
    2. Catalyzing chemical reactions – Some proteins are enzymes. Enzymes act as catalysts, speeding up chemical reactions.
  2. Albumin is a protein that is found in eggs. Which of the following describes the structure of albumin?
    1. A chain of amino acids folded and twisted into a molecule.
      1. Albumin is a protein. Proteins are made up of one or more chains of amino acids called a polypeptides.
  3. The conformation, or shape, of a protein determines its function. There are four orders of protein structure: primary, secondary, tertiary, and quaternary. Which of the following statements is accurate regarding these protein structures?
    1. Interactions between the R groups in amino acids form tertiary structure.
      1. Proteins consisting of a simple polypeptide chain are in primary structure.
      2. alpha helices and beta pleated sheets are types of secondary protein structures.
      3. Quaternary structures are formed when multiple amino acid chain (polypeptide) come together.
Protein_structures
  1. Which of the following statements is accurate regarding these protein structures?
    1. Interactions between the R groups in amino acids form tertiary structure.
      1. Tertiary structure is primarily due to R group interactions between the amino acids that make up the protein. This gives proteins with tertiary structure a three-dimensional shape. R group interactions involved in tertiary structure include hydrogen bonding, ionic bonding, dipole-dipole interactions, and London dispersion forces.
      2. αalpha helices and βbeta pleated sheets are types of secondary protein structures.
        1. Amino acids fold into repeating patterns due to hydrogen bonding of the peptide backbone.
      3. Primary structure is formed via peptide bonds where several amino acids are joined together.
      4. Quaternary structures are formed when multiple amino acid chain (polypeptide) come together.
  2. Which of the following is an example of protein denaturation?
    1. A protein is exposed to extremely high heat, causing it to lose its secondary structure and be left with only its primary structure.
    2. Denaturation occurs when a protein unfolds, losing its higher-order structure, but not its primary structure. Changes in temperature or pH are common causes of protein denaturation.
  3. Polypeptides are chains of amino acids linked together in a specific order. What type of bonds are formed between these amino acids?
    1. Peptide bonds – In protein synthesis, the carboxyl group of the amino acid at the end of the growing polypeptide chain chain reacts with the amino group of an incoming amino acid, forming a peptide bond.
peptide bond

Carbohydrates:

  1. There are four major biological macromolecules: carbohydrates, lipids, proteins, and nucleic acids. Which of the following makes carbohydrates unique from the other biological macromolecules?
    1. Carbohydrates contain a 1:2:1 ratio of carbon to hydrogen to oxygen.
      1. The chemical formula of carbohydrates is (CH2​O)n​ meaning each carbohydrate molecule contains a 1 carbon:2 hydrogen:1 oxygen ratio.
      2. The monomers in carbohydrates are held together by glycosidic bonds
      3. Carbohydrates provides short-term energy reserves.
  2. Which of the following statements is true of the carbohydrate glucose?
    1. Glucose contains carbon, hydrogen, and oxygen atoms.
      1. All carbohydrates contain carbon, hydrogen, and oxygen. The chemical formula for glucose is C6H12O6, meaning it contains six carbons, twelve hydrogens, and six oxygens.
      2. Glucose and galactose have the same chemical formula C6​H12​O6​. While their atoms are bonded in the same order, they each have a different 3D arrangement of atoms around one of their asymmetric carbons. This makes them stereoisomers of one another.
  3. Carbohydrates are able to undergo a reaction known as hydrolysis. Which of the following correctly describes hydrolysis?
    1. Long carbohydrates are broken into monomers through the addition of water molecules between the subunits.
      1. Hydrolysis uses a water molecule to break a bond between polymers, adding a hydroxyl group to one end and a hydrogen to another.
Hydrolysis
  1. What type of carbohydrate is sucrose?
    1. Disaccharide
      1. Disaccharides form when two monosaccharides join together via dehydration synthesis. The hydroxyl (OH) group of one monosaccharide combines with the hydrogen of another, releasing an H2O molecule and forming a glyosidic linkage. In this case, glucose and fructose link to form sucrose.
        1. Image showing two carbon rings connected by C-O bonds
Non-reducing sugar
  1. Glucose and fructose are both monosaccharides. How does the structure of fructose compare to the structure of glucose?
    1. Glucose and fructose are structural isomers. Although glucose and fructose have the same chemical formula (C6​H12​O6​) glucose and fructose have different organizations of their atoms, making them structural isomers of one another.
    2. Glucose and fructose are isomers of one another, but they are structural isomers, not stereoisomers. This means they have the same chemical formula, but their constituents are bonded in different ways.
structural isomer

DNA structure:

  1. The pitch of a DNA molecule is 34A∘(angstrom). The following diagram represents a part of a DNA molecule. Which of the following illustrates the pitch of DNA?
DNA – Primary structure
  1. A – This is the radius of the DNA molecule.
  2. B – The pitch is the height of the DNA molecule in one turn.
  3. C – This is the length of the DNA molecule in one turn.
  4. D – This is the diameter of the DNA molecule.
  1. Which of the following best represent correct base pairing and bonding in the base pairs in a DNA molecule?
    1. C≡G – Cytosine (C) forms three hydrogen bonds with guanine (G).
    2. G≡C – Guanine (G) forms three hydrogen bonds with cytosine (C).
    3. T=A – Thymine (T) forms two hydrogen bonds with adenine (A).
  2. Which of the following make up the backbone of a DNA molecule?
    1. 5-carbon sugar
      1. One of the components of the DNA backbone is the 5-carbon sugar deoxyribose.
    2. Phosphate group
      1. One of the components of the DNA backbone is the phosphate group.
Nucleotide
  1. Which of the following statements about the bonding in base pairs in DNA are true?
    1. Cytosine forms three hydrogen bonds with guanine. In DNA, cytosine always pairs with guanine by forming three hydrogen bonds.
    2. Thymine forms two hydrogen bonds with adenine. In DNA, thymine always pairs with adenine by forming two hydrogen bonds.

Identifying the nature of bond linking the monomers and the process involved:

  1. The diagram below shows linking between two glucose units. Identify the process involved in this bond formation.
  1. Dehydration – Dehydration is a chemical reaction that involves the loss of a water molecule during bond formation.
  2. An amide bond is a covalent bond formed between the carboxyl group of one molecule and the amino group of another. The final product is an amide -CONH2. Which of the following polymers is most likely to have a similar linking between the monomers?
    1. Proteins – In proteins, a peptide bond formed between the carboxyl group (-COOH) of one amino acid and the amino group (NH2) of the next one is a type of amide bond.
  3. Cellulose is a polymer of glucose. It is made up of same type of glucose molecules. Name the bond that links the 222 carbon atoms of adjacent glucose molecules in cellulose.
    1. Glycosidic bond – Cellulose is a polysaccharide consisting of glucose monosaccharides linked by glycosidic bonds.
  4. Aayat while studying the structure of DNA, came across a variety of bonds present within different parts of the structure. According to her study, which of the following should Aayat identify to be linked by a phosphodiester bond?
    1. One nucleotide with another nucleotide. The  -OH on each sugar of adjacent nucleotides links to the phosphate group forming two ester bonds or a phosphodiester bond.
DNA Secondary Structure
  1. Identify the process involved in this bond formation.
  2. Dehydration – Dehydration is a chemical reaction that involves the loss of a water molecule during bond formation.
  1. Ajay was studying about amide group (-CONH2​). He learnt that an amide bond is a covalent bond formed between the carboxyl group of one molecule and the amino group of another. He then tried to identify monomers that undergo a linkage that is a type of amide bonding. Which of the following monomers should Ajay identify?
    1. Amino acids – A peptide bond formed between the carboxyl group (–COOH) of one amino acid and the amino group -NH2​ of the next one is a type of amide bond.
  2. The diagram below shows a portion of glycogen.
Glycogen

Name the bond labelled A – Glycosidic bond – Glycogen is a polysaccharide consisting of glucose monosaccharides linked by glycosidic bonds.

  1. The diagram below indicates a portion of the secondary structure of DNA. Various bonds have been labelled using letters  X, Y, Z, W
Secondary structure of DNA
  1. Which of the following bonds best represent a phosphodiester bond?
    1. X – The –OH on each sugar of adjacent nucleotides links to the phosphate group forming two ester bonds or a phosphodiester bond.
    1. Z – The  -OH on each sugar of adjacent nucleotides links to the phosphate group forming two ester bonds or a phosphodiester bond.
    2. Y and W are Nitrogenous bases are linked by hydrogen bonds.

Introduction to metabolism:

  1. Why do you, as a living organism, need to continually consume food?
    1. Food is broken down by catabolic pathways and converted to ATP, which is then used to fuel anabolic pathways.
      1. Food can only provide energy for the body if it’s properly catabolized (broken down) through exergonic reactions, converted to ATP, and then used to power the endergonic, build-up reactions of anabolism.
      2. Food, in its original form, cannot be used as a direct source of energy in the cell because it has to be converted into ATP, a form of usable cell energy, through catabolism.
      3. Anabolic pathways require energy input to build complex molecules from simpler ones, while catabolic pathways release energy by breaking down complex molecules into simpler ones.
      4. Endergonic reactions consume energy to build complex molecules, while exergonic reactions release energy break down complex molecules.
  2. During intense exercise, your body has the ability to undergo gluconeogenesis, a process in which certain small molecules already within the body are combined together and built into new glucose molecules that can be used by cells. Which of the following answer choices includes the proper terms to metabolically describe gluconeogenesis?
    1. It is an anabolic process with endergonic reactions that require an input of energy. Gluconeogenesis is an anabolic process because it involves building glucose molecules through endergonic reactions that require the input of energy (ATP) to work.
  3. AB⟶A+B+energy. Which best describes the reaction above?
    1. It is a catabolic reaction.
      1. This reaction is catabolic, since it releases energy as a complex molecule is broken down into smaller ones.
  4. What is the relationship between anabolism and catabolism?
    1. Anabolism builds molecules using the energy produced during catabolism.
      1. Anabolic reactions require energy to build larger molecules from smaller molecules. This energy is provided by catabolic reactions, which release energy as they break down complex molecules into simpler ones.
  5. During the Calvin cycle of photosynthesis, a plant cell uses carbon dioxide to synthesize large carbohydrates. Which statement about this reaction is true?
    1. Energy is consumed. This reaction is anabolic: building a larger molecule (carbohydrate) from a smaller one. Anabolic processes require energy to occur.
  6. During glycolysis, the molecule glucose is broken down into pyruvate. What type of reaction is this?
    1. Catabolic reaction – In catabolic reactions, energy is released as complex molecules are broken down into smaller ones.
  7. Which of the following best defines metabolism?
    1. The complete set of reactions carried out by a cell. Metabolism is the total sum of all of the chemical reactions that take place inside of a cell.
  8. A+B+C+energy⟶ABC. Which best describes the reaction above?
    1. It is an anabolic reaction. This reaction is anabolic, since it consumes energy to build a more complex molecule from smaller ones.

Enzymes:

  1. In the graph above, which letter represents the activation energy EAof a reaction without an enzyme and  why?
Enzyme reaction
  1. X; the activation energy is greater in an uncatalyzed reaction.
    1. The X label on the graph represents a larger Ea “hump” (as compared to Y). The increased steepness of this hump is due to the lack of an enzyme, making this an uncatalyzed reaction.
    2. X actually shows an increased activation energy  due to the lack of an enzyme in this uncatalyzed reaction.
      1. Y; the activation energy is reduced in an uncatalyzed reaction is only reduced in a catalyzed reaction due to the function and presence of an enzyme.
    3. The process of speeding up a reaction by reducing its activation energy is known as catalysis. The factor that’s added to lower the activation energy is called a catalyst. Biological catalysts are known as enzymes.
    1. Enzymes lower the activation energy EA​ of a reaction—the required amount of energy needed for a reaction to occur.
      1. In a catalyzed reaction, an enzyme is present. In an uncatalyzed reaction, an enzyme is not present.
        1. So, X; the activation energy is greater in an uncatalyzed reaction
  2. In the graph above, which letter represents the activation energy EA​ of a catalyzed reaction and why?
    1. Y; the activation energy is reduced in a catalyzed reaction. The Y label on the graph represents a  lower Ea  “hump” (as compared to X). The decreased steepness of this hump is due to the presence of an enzyme, making this a catalyzed reaction.
    2. In the graph above, what might cause a reaction that originally proceeds through the path of X to change and proceed through the path Y?
      1. The addition of a catalyst.
        1. The change in activation energy, or the change in the steepness of the graph’s “humps” from X to Y, is due to the addition of an enzyme, which functions as a biological catalyst.
  3. The active site of an enzyme is damaged, leaving it non-functional. How would this change to the enzyme’s function be best described using the graph above?
    1. The reaction originally proceeded through the path of Y, but now proceeds through the path of X.
      1. Because the enzyme is now totally nonfunctional, the original catalyzed reaction (Y, lower Ea ) would become an uncatalyzed reaction (X, greater Ea​) due to the lack of the enzyme’s presence and function.
  1. Some species of bacteria can live in hot springs. Their cells contain enzymes that function best at temperatures 70, degreesC. How will the enzymes in these bacteria most likely change if the temperature is lowered to 45∘C?
    1. The enzymes will not catalyze reactions as efficiently.
      1. 70∘C, degrees, is the optimal temperature for the bacteria’s enzymes to function. A lower temperature would reduce the enzyme’s efficiency in speeding up a reaction.
  2. Which of the following is true regarding enzymes?
    1. Enzymes are reusable.
      1. Enzymes are not reactants and are not used up during the reaction. Once an enzyme binds to a substrate and catalyzes the reaction, the enzyme is released, unchanged, and can be used for another reaction.
  3. The diagram below shows an enzyme binding with substrate.
Enzyme-substrate
  1. What is one way to increase the rate of the reaction?
    1. Increase the enzyme concentration.
      1. Because there are a small number of enzymes, and a lot of substrate, the reaction rate is limited by the enzyme concentration. Adding more enzymes would allow more substrate to bind and the reaction would occur faster.
  2. How does an enzyme influence a chemical reaction?
    1. It speeds up the reaction rate.
      1. Enzymes lower the activation energy of a reaction by binding to substrates and holding them in a way that allows the reaction rate to increase.
  3. Amylase is an enzyme found in saliva that breaks down starch. The enzyme is currently functioning at its optimal pH of 7 and optimal temperature of 32∘Which of the following could result in an increase in the reaction rate?
    1. Increasing substrate concentration.
      1. Increasing substrate concentration could increase the rate of the reaction, as there would be more substrate to bind with the enzyme.
  4. Which of the following is true regarding the structure of enzymes?
    1. The active site is where the enzyme binds with the substrate.
      1. Enzymes bind to substrates at the active site, creating a enzyme-substrate complex. Once the reaction has been catalyzed, the active site is freed so the enzyme can bind to a new substrate.
  5. Pepsin is an enzyme found in the human stomach that breaks down protein. Pepsin will not break down starch. Which statement best explains this observation?
    1. Enzymes only work for specific substrates. Each type of enzyme typically only reacts with one, or a couple, of substrates. Pepsin is an enzyme that acts only on proteins, which is why it does not affect starches (carbohydrates).
  6. The table below shows three enzymes found in the human body and the pH of their locations.
EnzymeBody partpH
PtyalinMouth6.5 – 7
PepsinStomach1.0 – 3.0
TrypsinSmall intestine7.5 – 9.0
Enzymes
  1. How will the activity of pepsin change after it moves with the food from the stomach to the small intestine?
    1. It will slow down because the environment is too basic.
      1. Pepsin functions optimally in acidic environments, with a pH between 1.0 and 3.0. When it is moved outside of its optimal pH, enzyme activity will decrease.
  2. The table below shows three enzymes found in human body, and the temperature of their locations.
EnzymeBody partTemperature (°F)
PtalyinMouth98.06 – 98.6
PepsinStomach99.14 – 99.68
TrypsinSmall intestine99.14 – 99.68
enzyme
  1. How would a fever of 104°F most likely affect the activity of these enzymes?
    1. It could slow or stop enzyme function.
      1. The enzymes have an optimal temperature of approximately 98-99°F. Very high temperatures may cause an enzyme to denature, losing its shape and activity.

Enzymes and activation energy:

  1. The enzyme ptyalin helps digest carbohydrates, while the enzyme pepsin helps digest proteins. What prevents ptyalin and pepsin from digesting the same type of food?
    1. They have different shapes.
      1. The function of the enzyme is related to the shape of the enzyme.
  2. Which statement is true of enzymes?
    1. The activity of an enzyme might change as pH changes.
      1. Enzymes work best within a certain pH range, and, as with temperature, extreme pH values (acidic or basic) can make enzymes denature.
  3. Which of the following are roles of amino acids at an enzyme’s active site?
    1. Binding the substrate to the enzyme. The active site of an enzyme is the part of the enzyme where the substrate binds.
  4. How does an enzyme affect the rate of a reaction?
    1. It lowers the activation energy of the reaction, increasing the reaction rate.
      1. Enzymes lower activation energy of a reaction, decreasing the amount of energy required to start the reaction. This allows the reaction to occur faster than it would without the enzyme.
  5. Which statement is true of enzymes?
    1. The activity of an enzyme might change as pH changes.
      1. Enzymes work best within a certain pH range, and, as with temperature, extreme pH values (acidic or basic) can make enzymes denature.
  6. Which of the following are roles of amino acids at an enzyme’s active site?
    1. Binding the substrate to the enzyme.
      1. The active site of an enzyme is the part of the enzyme where the substrate binds.

Enzyme regulation and inhibition:

  1. What is the primary function of cofactors?
    1. To aid in enzyme function. Most enzymes do not function optimally, or even at all, unless bound to other non-protein helper molecules called cofactors.
  2. Pepstatin binds to the enzyme pepsin. The substrate is still able to bind to the active site, but the reaction is blocked. What is this an example of?
    1. Noncompetitive inhibition
      1. Pepstatin binds to the enzyme and blocks the reaction, but the substrate is still able to bind to the active site. It is “noncompetitive” because the both pepstatin and the substrate can be bound at the same time.
  3. Disulfiram binds to the active site of the enzyme aldehyde oxidase, blocking the binding of its substrate. What kind of a molecule is disulfiram?
    1. Competitive inhibitor
      1. Disulfiram “competes” with the substrate that binds to aldehyde oxidase, making it a competitive inhibitor.
  4. How do noncompetitive inhibitors interact with enzymes?
    1. They bind to a location other than the active site, stopping the enzyme from functioning.
      1. Noncompetitive inhibitors attach at a site other than the active site, blocking the enzyme from doing its job. They are “noncompetitive” because the inhibitor and substrate can both be bound at the same time.
  5. They bind to the active site, causing more substrate to bind. If a molecule binds to an active site, it will prevent the substrate from binding. What is true of a competitive inhibitor?
    1. It has a structure similar to the substrate.
      1. Competitive inhibitors “compete” with the substrate for the active site. They bind to an enzyme’s active site and block the substrate from attaching.