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Buffers are substances that help resist shifts in pH by
- accepting H+ when they are in excess.
- donating H+ to a solution when they have been depleted.
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One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3) Carbonic acid is a weak acid that dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+) Thus, H2CO3 <==> HCO3- + H+
the HCO3- to act as a base and remove excess H+ with the formation of H2CO3.
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One of the buffers that contribute to pH stability in human blood is carbonic acid H2CO3. Carbonic acid is a weak acid that when placed in an aqueous solution dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+) Thus,H2CO3 <==> HCO3- + H+ If the pH of the blood increases, one would expect
a decrease in the concentration of H2CO3and an increase in the concentration of H2O.
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Assume that acid rain has lowered the pH of a particular lake to pH 4.0. What is the hydroxide ion concentration of this lake?
1 x 10-10mol of hydroxide ion per liter of lake water
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Early 19th-century scientists believed that living organisms differed from nonliving things as a result of possessing a "life force" that could create organic molecules from inorganic matter. The term given to this belief is
vitalism
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The concept of vitalism is based on a belief in a life force outside the jurisdiction of physical and chemical laws. According to this belief, organic compounds can arise only within living organisms. Which of the following did the most to refute the concept of vitalism?
Wöhler's synthesis of urea
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How many electron pairs does carbon share in order to completeits valence shell?
1
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What type(s) of bond(s) does carbon have a tendency to form?
covalent
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Which of the following is(are) true about the carbon atoms present in all organic molecules?
- They were incorporated into organic molecules by plants.
- They were processed into sugars through photosynthesis.
- They are ultimately derived from carbon dioxide.
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structural isomers.
isomers with the same molecular formal but differ in arrangement
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geometric isomers.
same molecular molecules but differ in spatial arrangment of thier atoms
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Research suggests that side effects from Ritalin, the drug used to treat attention deficit disorder, may be caused by contamination of enantiomers, or molecules that
are mirror images of one another.
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Which of the followingcontains nitrogen in addition to carbon, oxygen, and hydrogen?
an amino acid such as glycine
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hydroxyl functional group
OH in a moleculer structure
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amino functional group
NH2
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carboxyl functional group
COOH, the C is double bonded to the O
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carbonyl group
- CO
- ketones is when the carbonly is within the structure
- aldehydes is when the carbonly is outside the structure
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Which of the following is notone of the four major groups of macromolecules found in living organisms?
glucose
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Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic linkage to one galactose molecule. How is lactose classified?
as a disaccharide
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A molecule with the formula C18H36O2is probably a
carbohydrate
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unsaturated fatty acid
a fatty acid contaning one or more double bonds between the carbons in the hydrocarbon tail
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A polypeptide can best be described as a
polymer of amino acids.
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The bonding of two amino acid molecules to form a larger molecule requires which of the following?
removal of a water molecule
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C-terminus
the carboxyl group C double bonded to O
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Which type of interactionstabilizes the alpha helix and the beta pleated sheet structures of proteins?
hydrogen bonds
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A strong covalent bondbetween amino acids that functions in maintaining a polypeptide's specificthree-dimensional shape is a (an)
disulfide bond.
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What would be an unexpected consequence of changing one amino acid in a protein consisting of 325 amino acids?
- The primary structure of the protein would be changed.
- The biological activity or function of the protein might be altered.
- The tertiary structure of the protein might be changed
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Altering which of thefollowing levels of structural organization could change the function of aprotein?
primary
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All of the followingmolecules are proteins except
hemoglobin. transthyretin. collagen. lysozyme. glycogen.
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What is the term used for achange in a protein's three-dimensional shape or conformation due to disruptionof hydrogen bonds, disulfide bridges, or ionic bonds?
denaturation
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What is the term used for aprotein molecule that assists in the proper folding of other proteins?
chaperonin
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Of the following functions, the major purpose of RNA is to
function in the synthesis of protein.
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Which of the following best describes the flow of information in eukaryotic cells?
DNA ==>RNA==> proteins
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A double-stranded DNAmolecule contains a total of 120 purines and 120 pyrimidines. This DNA moleculecould be comprised of
120 thymine and 120 adenine molecules.
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The two strands making up the DNA double helix molecule
are held together by hydrogen bonds.
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If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary strand would have the sequence
3'TAACGT5'.
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