7.5 proteins. 7.5.1 explain the four levels of protein structure, indicating the significance of...
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7.5Proteins
7.5.1 Explain the four levels of protein structure, indicating the significance of each level.
1°- sequence of amino acids in the chain
2°- coils; H bonds; collagen, keratin have repeated sequences so have lots coils
α-helix: hair, wool, horns, feathers
β-pleated sheet: silk
7.5.1 Explain the four levels of protein structure, indicating the significance of each level.
3°- helix folding; R groups interact: hydrophobics cluster together on inside, hydrophilics cluster on outside,
disulfide bridges between S of 2 R groups (cov bond),
ions may be cofactors
7.5.1 Explain the four levels of protein structure, indicating the significance of each level.
4°- different polypeptides combine w/H bonds, +/- attractions, hydrophobic forces, and/or disulfide bridges;
common in large globular proteins (hemoglobin—2 α chains, 2 β chains)
“conjugated proteins” - binding of prosthetic group: each chain also has a Heme group, contains Fe (not a polypeptide)
chlorophyll, electron transport chain enzymes are other examples
7.5.2 Outline the difference between fibrous proteins & globular proteins,
with reference to two examples of each protein type.
Fibrous Globular
Shape Long Tightly folded
Solubility Insoluble in water Soluble in water
Main level of organization
2° is most important 3° is most important
Function Structural (they ARE something)
Functional (they DO something)
Examples Collagen, keratin, myosin
Hemoglobin, enzymes, antibodies, hormones
7.5.3 Explain the significance of polar and non-polar amino acids.
• 20 common amino acids• 8 w/non-polar R groups
– Insoluble in water– Cluster together @ center (4° structure)
• More non-polar AAs less soluble in water• Cell membrane (phospholipid bilayer): polar on
outside, non on inside – Protein situated with hydrophilic portions to outside of
membrane, hydrophobic sections to center
7.5.4 State four functions of proteins, giving a named example of each:
• Structure: collagen (fibrous, structural ptn) builds tendons & in skin
• Enzymes: all are globular – starch –amylase maltose
• Transport: hemoglobin (globular, conjugated); readily, reversibly binds Oxygen b/c of heme group
7.5.4 State four functions of proteins, giving a named example of each:
• Hormones: some are ptns (some are steroids)– Insulin
• Contractile: muscle contractions (actin, myosin)
• Defense: antibodies/immunoglobulins for defense against antigens
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