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Wear eye protection to ward against...
shattered glass and spills of acids and bases
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Nitric acid (HNO3), hydrochloric acid (HCl), and sodium hydroxide (NaOH) solutions are ______ poisons, and mercuric chloride (HgCl2) and mercuric nitrate (Hg(NO3)2) are _____ poisons. If any of these solutions get on your skin...
corrosive, metabolic,...wash immediately under running water for several minutes
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_____ molecules build up skin, muscles, hair, the heart, liver, kidneys, and other essential organs.
Proteins
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Proteins are composed, for the most part, of...
long chains of amino acids joined together by peptide linkages
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How can amino acids react with other amino acids to form longer chain molecules?
because there is still a reactive group at either end of these molecules
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The human body builds up the proteins it needs from molecules furnished directly or indirectly by its ____.
food
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The protein molecules in food that we eat are broken down into their _____ residues through the process of _____ and are then absorbed.
amino acids, digestion
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The _____ contain molecular structures which they body must obtain form food if it is to synthesize other necessary protein strutures.
essential amino acids
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Amino acids contain both _____ and _____.
amine groups (usually -NH2) and carboxylic acid groups
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Because the amine group is a ____ and the carboxylic acid group is an ____, they react with each other, and the solid amino acids consist of internal salts, or ____ ions.
base, acid, dipolar
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The reactions of amino acids are characteristic of...
the particular funtional groups present
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In the protein itself, both the amine groups and the carboxylic acid group are usually tied up in the ____ linkage so they don't exhibit many of their usual reactions.
peptide
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Some of the reactions of amino acids which may be used to detect amino acids are...
- 1) The ninhydrin reaction
- 2) Xanthoproteic reaction
- 3) Nitroprusside reaction
- 4) Reactions with salts of heavy metals
- 5) Biuret test
- 6) Million's test
- 7) Denaturation and coagulation of proteins
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In the ______ reaction, most acids are colorless; however, they do react with ninhydrin to give a ___ colored product. This is a characteristic reaction of...
ninhydrin, blue, ...free amino acids
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Anyone who has carelessly spilled nitric acid on his skin soon observes a pronounced ____ color, which is espically noticable if concentrated nitric acid was used. This is the ________ reaction, and is due to the nitraction of the aromatic rings of _____, _____, and _____ present in skin protein.
yellow, xanthoproteic, tyrosine, tryptophan, and phenylalanine
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In the nitroprusside reaction, ____ and ____ are two amine acids that contain sulfur.
Cysteine and methionine
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Methionine is an essential amino acid, but part of the methionine requirement can be satisfied by _____.
cysteine
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The sulfhydryl group (-SH) in cysteine reacts with sodium nitroprusside to give a ____ color.
red
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Only the amino acids containing the _____ group give the red color with nitroprusside.
-SH
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Many proteins give _____ with salts of heavy metals such as ____, ____, and ____.
percipitates, mercury, lead, and silver
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The reaction with heavy metal salts is one of the processes that occurs in cases of ____ of these metals when the salts are taken orally.
acute toxicity
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In the case of metals reacting with the ______ and _____ their normal functioning is essentially destroyed.
protein lining of the mouth and stomach
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In basic solution copper ions react with many dissolved proteins to yeild a ____ to ___ color that is the rusult of the formation of a copper complex.
pink to violet
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The biuret reaction is characteristic of molecules containing ___ C=O-NH-H groups joined through a single ____ or ____ atom or joined directly.
two, carbon, nitrogen
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Compounds in which the C=O-NH group is replaced by the _____, _____, or _____ groups also gives the biuret test.
C=S-NH2 , C=NH-NH2 , -CH2NH2
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The biuret test is named fror the coumpound ___________ which gives a positive result for the test. It is charactertistic test for proteins when...
H2N-C=O-N-H-C=O-NH2 , ...they meet the structural requirements of the test
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In millon's test, proteins containing hydroxyphenyl groups react with hot mercuric nitrate solutions to produce a ____ colored solution or preceipitate. This essentially a test for the presence of ____ in the protein.
red, tyrosine
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The biologic functioning of a protein is generally dependent upon three types of stuctural features, which are...
- 1) the sequence of amino acids in the chain
- 2) the way parts of this amino acid chain interact with other parts via hydrogen bonding to form helices or sheets
- 3) the way the helices or sheets are folded to form larger sturctures
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A protein can be rendered ineffective for the purpose for which it was synthesized by the organism if any structural feature is disruped. Once this occurs the protein is described as _____.
denatured
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The denaturation process may be reversible, depending upon...
how extensive it is
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Proteins can be denatured by ___, ___, ____, or ____, and ____.
heat, light, strong acids, or alkalies, and by many other chemical and physical processes
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In many cases, a denatured protein is _____ soluble in water because of the excess ofeither positively or negatively charged groups on it.
reasonably
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The relative numbers of charges change with ___.
pH
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At a certain pH the numbers of postive and negative charges on the protein molecule are equal; this pH is called the _____ and the protein generally has ______ solubility at this point.
isoelectric point, minimum
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Give the names of 3 chemicals used in this experiment which are especially harmful to the eyes.
Nitric acid, hydrochloric acid, and sodium hyroxide
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List 3 body structures which are made up mostly of proteins.
skin, muscle, and hair
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What does a postive nitropruside test indicate about a substance?
That a -SH group is present
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What are the two groups that all amino acids possess?
amine groups and carboxylic acid groups
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Most amino acids will give a positive ninhydrin test but most proteins will not. Explain why this is true.
A postivie ninhydrin test is characteristic of free amino acids
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What amino acid (as a constituent in a protein) in the skin reacts with nitric acid give a yellow color in the xanthoproteic test?
Tyrosine
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Explain what is meant by the term "isoelectric point" in reference to proteins.
The pH at which the number of postive and negative charges on the protien molecule are equal.
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