Four Classes of Biological Macromolecules. Biological Macromolecules. Lipids

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1 Biological Macromolecules Much larger than other par4cles found in cells Made up of smaller subunits Found in all cells Great diversity of func4ons Four Classes of Biological Macromolecules Lipids Polysaccharides Proteins Nucleic Acids 1 2 Hydrophobic or amphipathic Lipids Important for: energy storage membrane signaling cushioning insula4on Include: fats phospholipids cholesterol and phytosterol some hormones others Fatty acid (palmitic acid) Glycerol (a) Dehydration reaction in the synthesis of a fat Ester linkage 3 (b) Fat molecule (triacylglycerol) 4 Structural formula of a saturated fat molecule Stearic acid, a saturated fatty acid (a) Saturated fat Structural formula of an unsaturated fat molecule Oleic acid, an unsaturated fatty acid Hydrophobic tails Hydrophilic head (a) Structural formula Choline Phosphate Glycerol Fatty acids (b) Space-filling model Hydrophilic head Hydrophobic tails (c) Phospholipid symbol (b) Unsaturated fat cis double bond causes bending 5 6

2 Hydrophilic head WATER Hydrophobic tail WATER 7 8 Polysaccharides Trioses (C 3 H 6 O 3 ) Pentoses (C 5 H 10 O 5 ) Hexoses (C 6 H 12 O 6 ) Complex sugars Polymers of monosaccharides (simple sugars) Polysaccharides and monosaccharides are carbohydrates Important for: storage of energy cell iden4ty marking Ketoses Aldoses Glyceraldehyde Dihydroxyacetone Ribose Galactose 9 Ribulose Fructose glycosidic linkage Chloroplast Starch Mitochondria Glycogen granules (a) Dehydration reaction in the synthesis of maltose Maltose 1 2 glycosidic linkage 1 µm 0.5 µm Fructose Sucrose (b) Dehydration reaction in the synthesis of sucrose Amylose Amylopectin (a) Starch: a plant polysaccharide Glycogen (b) Glycogen: an animal polysaccharide 11 12

3 Cell walls Cellulose microfibrils in a plant cell wall Microfibril (a) and glucose ring s 10 µm 0.5 µm Cellulose molecules (b) Starch: 1 4 linkage of glucose monomers (b) Cellulose: 1 4 linkage of glucose monomers 13 monomer 14 (a) The (b) Chitin forms the (c) Chitin is used to make of the chitin exoskeleton of a strong and flexible monomer. arthropods. surgical thread Proteins Polymers of amino acids Highly complex shape Func4on is based on shape Huge variety of func4ons 17 18

4 Substrate (sucrose) carbon OH Enzyme (sucrase) H 2 O Fructose H O Amino group Carboxyl group Nonpolar Peptide bond Glycine (Gly or G) Alanine (Ala or A) Valine (Val or V) Leucine (Leu or L) Isoleucine (Ile or I) Methionine (Met or M) Phenylalanine Trypotphan (Phe or F) (Trp or W) Polar Proline (Pro or P) (a) Serine (Ser or S) Threonine (Thr or T) Cysteine Tyrosine (Cys or C) (Tyr or Y) Electrically charged Asparagine Glutamine (Asn or N) (Gln or Q) Peptide bond Side chains Acidic Basic Backbone Aspartic acid Glutamic acid (Asp or D) (Glu or E) Lysine (Lys or K) Arginine (Arg or R) Histidine (His or H) 21 (b) Amino end (N-terminus) Carboxyl end (C-terminus) 22 Polypeptide chain Chains Antibody protein Protein from flu virus Iron Heme Collagen Chains Hemoglobin 23 24

5 Primary Normal hemoglobin Val His Leu Thr Pro Glu Glu Primary Sickle-cell hemoglobin Val His Leu Thr Pro Val Glu Secondary and tertiary s subunit Secondary and tertiary s Exposed hydrophobic region subunit Denaturation Quaternary Normal hemoglobin (top view) Quaternary Sickle-cell hemoglobin Function Molecules do not associate with one another; each carries oxygen. 10 µm Function Molecules interact with one another and crystallize into a fiber; capacity to carry oxygen is greatly reduced. 10 µm Normal protein Renaturation Denatured protein Red blood cell shape Normal red blood cells are full of individual hemoglobin moledules, each carrying oxygen. Red blood cell shape Fibers of abnormal hemoglobin deform red blood cell into sickle shape Nucleic Acids 5ʹ C 5ʹ end Nitrogenous bases Pyrimidines Polymers of nucleo4des also called polynucleo4des Store and convey informa4on Instruc4on manual of the cell Include: DNA (deoxyribonucleic acid) RNA (ribonucleic acid) Important for: reproduc4on of cells produc4on of proteins 3ʹ C Phosphate group 5ʹ C 3ʹ C (b) Nucleotide 3ʹ end (a) Polynucleotide, or nucleic acid Nucleoside Nitrogenous base Sugar (pentose) Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Purines Adenine (A) Guanine (G) Sugars Deoxyribose (in DNA) Ribose (in RNA) (c) Nucleoside components: sugars DNA Sugar-phosphate backbones Base pair (joined by hydrogen bonding) 1 Synthesis of mrna in the nucleus mrna Old strands Nucleotide about to be added to a new strand 2 NUCLEUS Movement of mrna into cytoplasm via nuclear pore mrna CYTOPLASM Ribosome New strands 3 Synthesis of protein 29 Polypeptide Amino acids 30

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