you must know how the sequence and subcomponents of proteins determine their properties. the...
TRANSCRIPT
You Must Know• How the sequence and subcomponents of proteins
determine their properties.• The cellular functions of proteins. (Brief – we will come
back to this in other chapters.)• The four structural levels of proteins and how changes
at any level can affect the activity of the protein.• How proteins reach their final shape (conformation),
the denaturing impact that heat and pH can have on protein structure, and how these may affect the organism.
• The directionality of proteins (the amino and carboxyl ends).
Concept 3.5: Proteins include a diversity of structures, resulting in a wide range of functions
• Proteins account for more than 50% of the dry mass of most cells.
• Protein functions include defense, storage, transport, cellular communication, movement, and structural support.
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• Life would not be possible without enzymes.
• Enzymatic proteins act as catalysts, to speed up chemical reactions without being consumed by the reaction
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Enzyme
• Polypeptides are unbranched polymers built from the same set of 20 amino acids
• A protein is a biologically functional molecule that consists of one or more polypeptides
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Figure 3.UN04
Side chain (R group)
Carboxylgroup
Aminogroup
carbon
Amino Acids
Figure 3.17a
What do the side chains of these amino acids have in common?
Side chain (R group)
Glycine (Gly or G)
Alanine (Ala or A)
Methionine (Met or M)
Phenylalanine (Phe or F)
Leucine (Leu or L)
Isoleucine (le or )
Tryptophan (Trp or W)
Proline (Pro or P)
Valine (Val or V)
Figure 3.17b
Serine (Ser or S)
Threonine (Thr or T)
Tyrosine (Tyr or Y)
Asparagine (Asn or N)
Cysteine (Cys or C)
Glutamine (Gln or Q)
What do the side chains of these amino acids have in common?
Figure 3.17c
Aspartic acid (Asp or D)
Glutamic acid (Glu or E)
What do the side chains of these amino acids have in common?
Figure 3.17c
Arginine (Arg or R)
Lysine (Lys or K)
Histidine (His or H)
What do the side chains of these amino acids have in common?
C-terminusN-terminus peptide bond
Protein Structure and Function
• A functional protein consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape
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“mad cow disease”
• The sequence of amino acids, determined genetically, leads to a protein’s three-dimensional structure.
• A protein’s structure determines its function
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Four Levels of Protein Structure
• Proteins are very diverse, but share three superimposed levels of structure called primary, secondary, and tertiary structure.
• A fourth level, quaternary structure, arises when a protein consists of more than one polypeptide chain
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Figure 3.21aPrimary structure
Amino end
Carboxyl end
Primary structure of transthyretin
125
95
90
100105110
120
115
80
70 60
85
75
6555
504540
2530
35
20 15
1051
Amino acids
Figure 3.21ba
Secondary structure
Hydrogenbond
pleated sheet
helix
Hydrogen bond
strand
Figure 3.21d
Polypeptidebackbone
Hydrogenbond
Disulfidebridge
Ionic bond
Hydrophobicinteractions andvan der Waalsinteractions
Tertiary structure
Figure 3.21f
HemeIron
subunit
subunit
subunit
subunitHemoglobin
Quaternary Structure
Figure 3.23-1
Normal protein
Figure 3.23-2
Normal protein Denatured protein
Figure 3.23-3
Denatured proteinNormal protein