Chem Lab - Ex 37
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Wear eye protection to ward against...
shattered glass and spills of acids and bases
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
_____ molecules build up skin, muscles, hair, the heart, liver, kidneys, and other essential organs.
Proteins are composed, for the most part, of...
long chains of amino acids joined together by peptide linkages
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
The human body builds up the proteins it needs from molecules furnished directly or indirectly by its ____.
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
The _____ contain molecular structures which they body must obtain form food if it is to synthesize other necessary protein strutures.
essential amino acids
Amino acids contain both _____ and _____.
amine groups (usually -NH2) and carboxylic acid groups
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
The reactions of amino acids are characteristic of...
the particular funtional groups present
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.
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
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
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
In the nitroprusside reaction, ____ and ____ are two amine acids that contain sulfur.
Cysteine and methionine
Methionine is an essential amino acid, but part of the methionine requirement can be satisfied by _____.
The sulfhydryl group (-SH) in cysteine reacts with sodium nitroprusside to give a ____ color.
Only the amino acids containing the _____ group give the red color with nitroprusside.
Many proteins give _____ with salts of heavy metals such as ____, ____, and ____.
percipitates, mercury, lead, and silver
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.
In the case of metals reacting with the ______ and _____ their normal functioning is essentially destroyed.
protein lining of the mouth and stomach
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
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
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
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
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.
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
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 _____.
The denaturation process may be reversible, depending upon...
how extensive it is
Proteins can be denatured by ___, ___, ____, or ____, and ____.
heat, light, strong acids, or alkalies, and by many other chemical and physical processes
In many cases, a denatured protein is _____ soluble in water because of the excess ofeither positively or negatively charged groups on it.
The relative numbers of charges change with ___.
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
Give the names of 3 chemicals used in this experiment which are especially harmful to the eyes.
Nitric acid, hydrochloric acid, and sodium hyroxide
List 3 body structures which are made up mostly of proteins.
skin, muscle, and hair
What does a postive nitropruside test indicate about a substance?
That a -SH group is present
What are the two groups that all amino acids possess?
amine groups and carboxylic acid groups
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
What amino acid (as a constituent in a protein) in the skin reacts with nitric acid give a yellow color in the xanthoproteic test?
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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