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15 questions · 3 topics · Made with PupilBot from the author's own notes
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A protein is composed of several polypeptide chains that associate into one functional protein. Which level of protein structure is being described?
Answer: Quaternary structure
Quaternary structure describes the arrangement of multiple polypeptide chains. Primary structure is the amino-acid sequence, secondary structure involves folding or coiling, and tertiary structure is the complete three-dimensional arrangement of one polypeptide.
Why can carbon form such a wide variety of biological molecules?
Answer: It has four valence electrons and can form single, double, and triple covalent bonds.
Carbon has four valence electrons, allowing it to form stable covalent bonds of different types and create chains, branches, and rings.
A fatty acid with only single carbon-carbon bonds is ___, whereas one with at least one carbon-carbon double bond is ___.
Answer: Blank 1: saturated. Blank 2: unsaturated.
Saturated fatty acids contain only single carbon-carbon bonds. Unsaturated fatty acids contain at least one carbon-carbon double bond.
Which statements correctly connect a biological macromolecule with its building blocks or components and a function?
Answer: Carbohydrates are made of simple sugars and can provide immediate energy. · Proteins are made of amino acids and can function in transport or defense. · Nucleic acids are made of nucleotides and store or transmit genetic information.
Carbohydrates contain simple sugars, proteins contain amino acids, and nucleic acids contain nucleotides. Their listed functions are characteristic of these macromolecules. Lipids do not consist of nucleotides, and carbohydrates do not form polypeptides.
Describe the structure of a nucleotide and explain the roles of DNA and RNA in cells.
Answer: A nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. DNA and RNA are nucleic acids that store and transmit genetic information.
The three components identify a nucleotide, while DNA and RNA are polymers of nucleotides involved in storing and transmitting genetic information.
The molecules that bind to an enzyme are called ___, and they attach at the enzyme’s ___.
Answer: Blank 1: substrates. Blank 2: active site (also accept: active-site).
Substrates bind to the active site. The complementary shapes of the substrate and active site help make enzymes specific.
Why might an enzyme work poorly after exposure to an extreme pH? Explain what happens to the enzyme and how this affects its active site.
Answer: An extreme pH can change or unfold the enzyme’s protein structure. This disrupts the shape of the active site, so the substrate no longer binds effectively and the reaction rate decreases.
Enzyme activity depends on the specific three-dimensional shape of the protein and its active site. Extreme pH can alter that shape and reduce substrate binding.
Which condition would best support the activity of pepsin?
Answer: An acidic environment
Pepsin works best in acidic conditions. Enzymes have particular conditions in which their active sites maintain the most effective shape.
In the generated graph, which curve best represents an enzyme that has been exposed to very high temperature before its activity is measured?
Answer: The orange curve, which remains at a low activity level
Very high temperature can change or unfold an enzyme’s protein structure, disrupting the active site and causing low activity.
Which changes would normally result from adding an enzyme to a chemical reaction?
Answer: The activation energy decreases. · The reaction proceeds faster. · The enzyme is not consumed by the reaction.
Enzymes are biological catalysts that lower activation energy and increase reaction rate. They are not consumed and do not change the starting reactants or final products.
Why is water an effective solvent, and how can a buffer help an organism maintain a suitable pH?
Answer: Water is an effective solvent because its polarity allows it to attract and separate charged or partially charged particles. A buffer helps prevent sharp changes in pH by reducing the effect of added acids or bases.
The uneven distribution of charge in water allows it to interact with many solutes. Buffers stabilize chemical conditions by resisting sudden changes in hydrogen-ion concentration and therefore pH.
What pH value should a solution have to be considered neutral?
Answer: Value: 7 (exact, no tolerance).
A solution with a pH of 7 is neutral; values below 7 are acidic and values above 7 are basic.
Which statements correctly describe important properties of water?
Answer: Cohesion is the attraction between water molecules. · Adhesion is the attraction between water and a different substance. · Water's relatively high heat capacity helps it resist rapid temperature changes.
Cohesion occurs between molecules of the same substance, adhesion occurs between different substances, and water's high heat capacity limits rapid temperature changes. Water is polar, and a pH below 7 is acidic rather than neutral.
In a solution, the substance that does the dissolving is the ___, while the substance being dissolved is the ___.
Answer: Blank 1: solvent. Blank 2: solute.
The solvent dissolves another substance, and the solute is the substance that becomes dissolved.
In the generated image, which interaction best explains why the water rises along the glass surface?
Answer: Adhesion
Adhesion is the attraction between molecules of different substances, such as water and glass. Cohesion would describe attraction among water molecules themselves.
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