Practice Questions Bio
Entropy
Entropy is a measure of the amount of disorder, or randomness, in a system. Every time energy is converted to one form or another, entropy increases. In general, the more disordered a system is, the higher its entropy.
How does an enzyme lower a reactions activation energy?
Enzymes bring reactants into contact with each other so that less energy is required to start the reaction.
What do enzymes do in cells?
Enzymes speed up chemical reactions without being consumed in the process.
Most enzymes are
proteins
Building proteins ___________ energy; ATP hydrolysis __________ energy.
requires; releases
Why does oil not dissolve in water?
Oil is hydrophobic.
What are some energy conversions that occur in cells?
One example is photosynthesis, which uses light energy to store the chemical energy of glucose. Cells use the potential energy in glucose to power many processes which includes muscle movement (which illustrates kinetic energy).
An enzyme whose 3-D shape or conformation is altered will become inactive.
True
Distinguish between endergonic and exergonic reactions.
Endergonic reactions require an input of energy to proceed to completion. Exergonic reactions release energy.
Enzymes are reusable. One enzyme could do the job of twenty enzymes; however, it would take much longer. Enzymatic activity is dependent upon enzyme concentration and the time allotted. Enzymes are only functional in their three-dimensional shape. The active site of an enzyme is not formed in the primary and secondary structures. In order for an enzyme to fold into its three-dimensional tertiary (or quaternary) structure, the environmental conditions such as temperature and pH must be favorable. Enzymes are substrate-specific, meaning, enzymes prefer a specific substrate.
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In competitive inhibition, an inhibitor binds to the active site of an enzyme, preventing the enzyme from binding with its substrate.
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In noncompetitive inhibition, an inhibitor binds to a spot on an enzyme other than the active site of the enzyme. This alters the enzyme's shape, so it can no longer bind to its substrate.
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Molecules in food, such as glucose, store energy. When cells break down organic molecules, such as glucose energy is released. The energy is used to produce ATP the energy currency of the cell. In a hydrolysis reaction, the cell uses Water to break ATP into ADP+P, releasing energy. The cell can use energy from ATP hydrolysis to perform endergonic reactions. In this way, the exergonic reaction of ATP hydrolysis is coupled to an endergonic reaction.
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How do the values of 0, 7, and 14 relate to the pH scale?
0 and 14 on the pH scale represents the strongest acidic and basic solutions, respectively, while 7 is the pH value of a neutral solution.
Match the description to the appropriate protein structure. The task is to match the lettered items with the correct numbered items. Appearing below is a list of lettered items. Following that is a list of numbered items. Each numbered item is followed by a drop-down. Select the letter in the drop down that best matches the numbered item with the lettered alternatives. a. Amino acid sequence of a polypeptide. b. Overall protein shape, arising from interactions between multiple polypeptides that make up the functional protein. c. Localized areas of coils and sheets stabilized by hydrogen bonds. d. Overall shape of one polypeptide.
1. Primary structure - Amino acid sequence of a polypeptide. 2. Secondary structure - Localized areas of coils and sheets stabilized by hydrogen bonds. 3. Tertiary structure - Overall shape of one polypeptide. 4. Quaternary structure - Overall protein shape, arising from interactions between multiple polypeptides that make up the functional protein.
Match the molecules with their function. The task is to match the lettered items with the correct numbered items. Appearing below is a list of lettered items. Following that is a list of numbered items. Each numbered item is followed by a drop-down. Select the letter in the drop-down that best matches the numbered item with the lettered alternatives. a. Form major part of biological membranes b. Stabilize animal membranes; sex hormones c. Store energy d. Provide waterproofing; prevent water loss
1. Triglycerides (fats) - Store energy 2. Phospholipids - Form major part of biological membranes 3. Steroids - Stabilize animal membranes; sex hormones 4. Waxes - Provide waterproofing; prevent water loss
How many different amino acids make up the tens of thousands of different proteins in your body?
20
In a sample of double-stranded DNA, 30% percent of the nitrogenous bases are guanine (G). What percentage of the nitrogenous bases in the sample are adenine (A)?
20% The percent composition of guanine is equal to that of cytosine, and the percent composition of adenine is equal to that of thymine. Given %G = 30%, we know %C = 30%. This means that the remaining percentage (40%) is equal amounts of A and T. 40% divided in half gives us 20% adenine and 20% thymine.
Why does the amount of entropy in the universe always increase?
According to the second law of thermodynamics, the entropy in the universe always increases because in every reaction some energy is lost as heat, and heat is a disordered form of energy.
What is the significance of a protein's shape, and how can the shape be destroyed?
A protein's shape determines its function. The shape can be destroyed by exposure to heat, strong acids, or strong bases; each of these can denature a protein. Also, genetic mutations can change the amino acid sequence of a protein, perhaps altering its overall shape. (We'll learn more about this at the end of the semester.)
Distinguish between a solute and a solvent.
A solute (such as salt) is a substance that dissolves in a liquid solvent (such as water).
What are the main parts of an ATP molecule?
ATP is a nucleotide consisting or ribose, a nitrogenous base, and three phosphate groups.
Compare and contrast the structure of polysaccharides, proteins and nucleic acids.
All are long polymers built of monomers. The monomers that form polysaccharides are monosaccharides. The monomers that form proteins are amino acids. The monomers that form nucleic acids are nucleotides.
How do acids and bases affect a solution's H+ concentration?
An acid adds H+ to the solution, whereas a base absorbs H+ or releases OH-.
Which of the following statements about acids and bases is/are true? (Check all that apply.)
An acid increases the concentration of H+ of a solution and lowers its pH. A base decreases the H+ of a solution and raises its pH. Adding a base to an acidic solution will bring the pH of the solution closer to 7.
How does the number of valence electrons determine an atom's tendency to form chemical bonds?
An atom is most stable if its valence (outmost) shell is full. The number of "vacancies" in the valence shell determines how many electrons an atom will gain, lose, or share to achieve a full valence shell. Some atoms, such as neon and argon, do not form bonds because they already have a full valence shell.
Where in an atom are protons, neutrons, and electrons located?
An atom's protons and neutrons are located in its nucleus. A cloud of electrons surrounds the nucleus.
Distinguish between an enzyme and a coenzyme.
An enzyme is an organic molecule (typically a protein) that speeds up a chemical reaction. A coenzyme is an organic molecule, such as a vitamin, that is required for an enzyme to function.
How does water participate in the chemistry of life?
Because cells are mostly made up of water and because most cells are surrounded by water, water is the medium in which nearly all life's chemical reactions occur. Water is either a reactant in or a product of many of the chemical reactions that sustain life, including photosynthesis.
How does the density difference between ice and liquid water affect life?
Because the density of ice is less than that of liquid water, a layer of ice forms at the top of a lake in cold temperatures. Insulated from the cold air above, the liquid water below the ice layer is less likely to freeze. Aquatic organisms that cannot tolerate freezing can therefore survive the cold season.
Which of the following is true about buffers?
Buffer solutions help maintain a constant pH by absorbing or releasing H+ into a solution. When pH is too high, buffers release H+ ions to lower the pH. When pH is too low, buffers absorb H+ ions to raise the pH.
Which four elements do organisms require in the largest amount?
Carbon, oxygen, hydrogen, and nitrogen are the chemical elements that organisms require in the largest amounts.
How are cohesion and adhesion important to life?
Cohesion is water's tendency to stick to itself. Adhesion is water's tendency to stick to other substances. Cohesion means water is liquid at most temperate on Earth's surface; it allows small insects to "skate" on the water surface. Both cohesion and adhesion help water move from roots to leaves in plants.
In the biochemical pathway shown above, the product of enzyme 2 is the substrate for enzyme 1.
False, The product of enzyme 2 is the substrate for enzyme 3.
Sucrose is a disaccharide that forms when a molecule of glucose bonds with a molecule of fructose. What type of reaction joins glucose and fructose?
Dehydration synthesis
Which statement is NOT true about carbohydrates?
Disaccharides are formed by hydrolysis.
Which of the following correctly represents the mechanism of enzyme function? In the answer choices below, E = Enzyme, P = Product, and S = Substrate. A dash between two molecules means that they are united (e.g., E-P stands for an enzyme bound to a product).
E + S -> E-S -> E-P -> E + P
What are some examples of the "work" of a cell?
Examples of "work" of a cell include cell division, biochemical reactions (such a dehydration synthesis and hydrolysis), and membrane transport.
Glucose (Monosaccharide) - provides quick energy Cellulose - provides structural support to plant cells Starch - stores energy in plants Glycogen - stores energy in animals Proteins - carry out nearly all the work of the cell Nucleic Acids - Store and use genetic information and transmits it to the next generation
Glucose (Monosaccharide) - provides quick energy Cellulose - provides structural support to plant cells Starch - stores energy in plants Glycogen - stores energy in animals Proteins - carry out nearly all the work of the cell Nucleic Acids - Store and use genetic information and transmits it to the next generation
Two or more atoms bonded together form a molecule. A compound is a molecule made of atoms of two or more different elements.
How are atoms, molecules, and compounds related?
What type of reaction breaks down the disaccharide sucrose to the monosaccharides glucose and fructose?
Hydrolysis
How does ATP hydrolysis supply energy for cellular functions?
Hydrolysis of ATP breaks the unstable bonds between the second and third phosphate group, releasing energy. The reaction is coupled to cellular reactions that require energy input.
Distinguish between hydrolysis and dehydration synthesis?
Hydrolysis reactions break the covalent bonds between the subunits of a large molecule; the opposite reaction, dehydration synthesis forms the covalent bonds that link the subunits of a large molecule to one another.
What are hydrophilic substances?
Hydrophilic substances are either polar or charged, so they readily dissolve in water. ("hydro" = water "philic" = loving)
What happens in a chemical reaction?
In a chemical reaction, reactants swap atoms to form products. As atoms are swapped, chemical bonds are broken, energy is released or used in the reaction, and new chemical bonds are formed.
How do buffers regulate the pH of a fluid?
In buffer systems, pairs of weak acids and bases consume or release H+. Adding an acid or base therefore does not affect the pH of a buffered solution.
Explain negative feedback.
In negative feedback, the accumulation of the reaction's product causes the reaction to slow down.
Explain how electronegativity differences between atoms result in each type of chemical bonds.
Ionic bonds form between pairs of atoms that have extremely different electronegativities; in this case, one atom takes one or more electrons from the other. Polar covalent bonds form between atoms that have moderately different electronegativities; such atoms share electrons unequally and thus have partial positive or partial negative charges. Nonpolar covalent bonds form between atoms that have similar electronegativities and share electrons approximately equally. The partial charges on molecules with polar covalent bonds may lead to hydrogen bonds between adjacent molecules
How are isotopes of the same element different from one another?
Isotopes of the same element have the same number of protons but different number of neutrons.
Which reaction is likely coupled with the hydrolysis of ATP?
Joining monosaccharides together DNA synthesis
Potential Energy: Chemical bonds in a sugar molecule Energy Bar
Kinetic Energy: Rolling Ball Contracting muscles
What are lipids?
Lipids are hydrophobic organic molecules consisting mainly of carbon and hydrogen.
What is metabolism on a cellular level?
Metabolism is a sum of all chemical reactions in a cell.
_______________ are monomers that form polymers that are called _________________.
Nucleotides; nucleic acids
What are some differences between RNA and DNA?
RNA is typically a single strand of nucleotides, and DNA is a double strand of nucleotides. RNA nucleotides include ribose. DNA nucleotides include deoxyribose. RNA has a nitrogenous base uracil; DNA has thymine.
Describe how your body has both potential and kinetic energy.
Stored fuels such as glucose, glycogen, and fat contain potential energy. The body's muscle movements illustrate kinetic energy, as does the movement of substances across membranes and within cells.
Describe the relationship among endergonic reactions, ATP hydrolysis, and cellular respiration.
The ATP that is produced in cellular respiration can undergo hydrolysis, releasing energy that can be used to drive endergonic reactions.
What are the components of a triglyceride?
The components of a triglyceride are a glycerol molecule and three fatty acids.
How do hydrogen ions relate to the pH scale?
The concentration of H+ ions determines a solutions pH. The higher the concentration, the lower the pH.
first law of thermodynamics
The first law of thermodynamics is the law of energy conservation. It states that energy cannot be created or destroyed, just converted to one form or another.
When an egg is fried, what happens to the proteins in the egg?
The heat denatures the proteins in the egg.
Why is a saturated fat solid at room temperature?
The hydrocarbon chain of a saturated fatty acid contains no double bonds, so the molecules can align and pack together in an orderly fashion.
How does water help an organism regulate its body temperature?
The hydrogen bonds in water keep it from changing temperature quickly, even if the external temperature rises or drops. In addition, in some animals, sweat is an adaptation that cools the body as water evaporates from the skin.
How does the chemical structure of phospholipids enable them to form a bilayer in water?
The hydrophilic heads make contact with water, whereas the hydrophobic tails avoid water. When many phospholipids join, the hydrophilic heads and hydrophobic tails align, forming a bilayer.
What is the relationship between the mass of 12C and the atomic weight of carbon (12.012)?
The mass of 12C is 12 (6 protons + 6 neutrons). The atomic weight of carbon is 12.012, not 12, because the atomic weight is the average mass of all the atoms of that element (including all the isotopes). Like other elements, carbon has the mass number of 12, 13, and 14. About 99% of carbon atoms are 12C; the other two isotopes are heavier, so the atomic weight is slightly more than 12.
second law of thermodynamics
The second law of thermodynamics states that all energy transformations are inefficient because every reaction loses some energy as heat.
Are saturated or unsaturated fats solid at room temperature? Give an example of each type of fat.
The straight fatty acid chains of saturated fats stack neatly, easily forming solids at room temperature. Bacon and butter are examples of saturated fats. Double bonds in liquid unsaturated fats create kinks that prevent the fat molecules from packing tightly. Olive oil is an example of an unsaturated fat.
Thermodynamics
Thermodynamics is the study of energy transformation. The first and second law of thermodynamics describes the energy conversions vital for life, as well as those that occur in the nonliving world. For example, they apply to energy transformations, such as gasoline combustion in a car's engine, a burning chunk of wood, or a cell breaking down glucose.
List three conditions that influences enzyme activity.
Three conditions that can influence an enzyme's activity are pH, temperature, and salt concentration. Noncompetitive and competitive inhibitors can also affect enzyme activity.
The four nitrogenous bases of RNA are:
adenine, uracil, guanine, cytosine
Adenosine triphosphate (ATP)
is a nucleotide that temporarily stores energy. All cells rely on the potential energy stored in ATP to power chemical reactions.
Compared to a glucose molecule, a starch molecule
is used for energy storage in plant cells.
What type of bonds link individual amino acids together?
peptide bonds
