Lipids and phospholipids Lipids are not macromolecules Different types of

Lipids and phospholipids lipids are not

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Lipids and phospholipids Lipids are not macromolecules •Different types of lipids: phospholipids, cholesterol, etc •Energy storage •Signalling (water-insoluble vitamins, steroid hormones) •Forms membrane bilayer Figure 2-22 Molecular Biology of the Cell (© Garland Science 2008) 66
Proteins are experts at creating unimaginable structural diversity from only 20 building blocks (amino acids) 67 This is accomplished by a hierarchical structural order: Primary structure : the sequential order of the amino acids in the polypeptide Secondary structure : local folds of the polypeptide, often -helices and -sheets Tertiary structure : the global, 3-dimensional fold of the entire polypeptide Quaternary structure : the positioning of all polypeptide chains needed to make a functional protein
Figure 3-2 Molecular Biology of the Cell (© Garland Science 2008) Twenty amino acids have different physical and chemical properties 68
Figure 3-1 Molecular Biology of the Cell (© Garland Science 2008) The primary sequence affects the “surface look” of the polypeptide chain 69
Figure 3-4 Molecular Biology of the Cell (© Garland Science 2008) Non-covalent interactions within the polypeptide chain are responsible for folding 70
71 The -helix is a common secondary structure (local fold) found in proteins Helix is held in place by hydrogen bonds between nearby peptide bonds
72 The -sheet is a common secondary structure (local fold) found in proteins -sheets are held in place by hydrogen bonds between peptide bonds adjacent in space but that may be distantly located in the primary structure
Figure 3-10 Molecular Biology of the Cell (© Garland Science 2008) Secondary structures interact to form the three- dimensional structure (tertiary structure) of a protein 73
74 Proteins work by interacting with other molecules Interacting molecules can be small molecules or other macromolecules: these are called ligands Figure 3-36 Molecular Biology of the Cell (© Garland Science 2008) Ligands bind to proteins via noncovalent bonds Ligand binding specificity and strength (affinity) depends on type and number of non- covalent bonds
Proteins are like people: proteins have their own “social network” A “social network” for proteins is network of molecules (including other proteins) that a specific protein interacts with to do its function(s) eric-social-networks-and-your- identty/ Proteome Sci. 2011; 9: 35 . 75
Regulating protein function: the use of “ON” and “OFF” molecular switches Protein phosphorylation and GTPases 76
77 How can Molecular machines/enzymes can be turned on and off? Turning proteins ON and OFF: 1) Controls enzymatic activity 2) Controls protein-ligand interactions How does this happen? The “ON” and “OFF” states represent different conformations . One that is conducive to function, the other is not. “activator” “inactivator”
Figure 3-64 Molecular Biology of the Cell (© Garland Science 2008) Protein phosphorylation: kinases and phosphatases 78
Figure 3-71 Molecular Biology of the Cell (© Garland Science 2008) GTPases: molecular switches 79
Figure 3-73 Molecular Biology of the Cell (© Garland Science 2008) GTPases and phosphorylation are important for signaling and decision making 80

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