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Acidic side groups
Aparatic acid Asp, D
Glutamic acid Glu, E
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Basic side groups
Lysine Lys, K
Arginine Arg, R
Histidine His, H
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Polar charged amino acid bases carry what charge?
Negative
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Polar charged amino acids carry what charge?
Positive
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All amino acids have carboxyl and amino parts, but if they become the what in proteins
backbones in protein they are NOT available to participate in chemical reaction.
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Why can aspartic acid and glutamic acid participate in chemical reactions.
Because the carboxyl part is in the side chain (-R group)
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How are lysine, arginine, and histidine able to participate in chemical reactions?
If the amino part is in the side chain (-R) and can act as a proton acceptor in chemical reactions.
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What polar uncharged amino acid (hydrophilic) -R groups tend to have partial positive or negative charges?
Serine Ser, S
Threonine Thr, T
Glutamine Gln, Q
Asparagine Asn, N
Tyrosine Tyr, Y
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Hydrophilic side chains tend to have partial + or - charge allowing them to
participate in chemical reactions, form H-bonds, and associate with water.
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What are Nonpolar amino acids (hydrophobic) -R groups consist almost entirely of C and H atoms?
Alanine Ala, A
Valine Val, V
Leucine Leu, L
Isoleucine Ile, l
Methionine Met, M
Phynylalanine Phe, F
Tryptophan Trp, W
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Who does hydrophobic -R groups want to associate with?
Other hydrophobic R-groups or lipids.
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Nonpolar amino acids play an important role in membranes by
associating with the membrane lipid bilayer.
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What makes nonpolar amino acids not free to participate in reactions?
If S or N are present, they will be completely tied up.
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What are the four levels of protein structure?
Primary - the sequence of amino acids
Secondary - how that sequence if folded (a:helix, B: pleated sheet)
Tertiary - how helices or sheets are arranged in three dimensions.
Quaternary - arrangement of 3D structures into whole protein.
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Define Primary Structure
the order in which amino acids are strung together with peptide bonds.
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The primary structure may be twisted or folded into a
Secondary structure
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The Secondary structure of a protein is the
coiling or folding of its polypeptide chains.
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a-helix
"spiral staircase"
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Hair is an a-helical structure formed from the protein
Keratin; Keratin is made up of three a-helices twisted together in a cable.
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Many proteins that span the membrane are made up of
a-helices with the -R groups of hydrophobic (non-polar) amino acids associating with the hydrophobic lipids of the cell membrane and the -R groups of hydrophilic (polar) amino acids forming the pore.
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"B"- pleated sheets
are found in many proteins in nature (such as spider silk) but are less common in human proteins.
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Protein Structure illustrated. Helices, pleated, amino acids that don't have secondary structure.
a-helices are represented as coils
B-pleated sheets are represented as arrow (arrow points amino)
Amino acids that don't have secondary structure are threads
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Tertiary structures within proteins are
formed when separated chains, or different a-helices, or other parts of chains are joind together into a larger, folded structure.
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Types of atomic interactions leading to Tertiary structure
Ionic bonds
Hydrophobic interactions
Van der Waals interactions ("shapes" of molecules fit each other like puzzle pieces)
Disulfide bridges (are formed between cysteines. Cysteine is the only amino acid with an -SH group.
Hydrogen bonds
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Heme group
an iron-containing group which holds onto the oxygen molecule.
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Hemoglobin
the oxygen-carrying protein of the blood.
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The proper function of hemoglobin depends critically on
primary, secondary, tertiary and quaternary structure. Any alteration in the protein at any of these levels causes disease
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Primary, secondary and tertiary structure, combine together into a
quaternary structure.
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