Chapter 5

Big Questions How are molecules of biological systems constructed? What functions do these molecules have in relation to biological systems? How do these molecules interact in living systems?

Questions How are macromolecule polymers assembled from monomers?  How are they broken down? How can you tell a biological molecule is a carbohydrate? Explain the relationship between monosaccharides, disaccharides, and polysaccharides. Why are starch and glycogen useful as energy storage molecules, while cellulose is useful for structure and support?  Why isn’t cellulose easily broken down? How do herbivores solve the problem of cellulose digestion? How can you tell a biological molecule is a lipid? Chemically, what is the difference between a saturated fat and an unsaturated fat?  How does this difference affect the properties of the molecules? How are triglycerides, phospholipids, and steroids similar?  How do they differ?

(a) Dehydration reaction in the synthesis of maltose Fig. 5-5 1–4 glycosidic linkage Glucose Glucose Maltose (a) Dehydration reaction in the synthesis of maltose 1–2 glycosidic linkage Glucose Fructose Sucrose (b) Dehydration reaction in the synthesis of sucrose

(a) Starch: a plant polysaccharide Fig. 5-6 Chloroplast Starch Mitochondria Glycogen granules 0.5 µm 1 µm Amylose Glycogen Amylopectin (a) Starch: a plant polysaccharide (b) Glycogen: an animal polysaccharide

Cell walls Cellulose microfibrils in a plant cell wall Microfibril Fig. 5-8 Cell walls Cellulose microfibrils in a plant cell wall Microfibril 10 µm 0.5 µm Cellulose molecules Glucose monomer

The structure of the chitin monomer. Chitin forms the Fig. 5-10 The structure of the chitin monomer. Chitin forms the exoskeleton of arthropods. Chitin is used to make a strong and flexible surgical thread.

Peptidoglycan Cell wall

Fatty acid (palmitic acid) Fig. 5-11 Fatty acid (palmitic acid) Glycerol (a) Dehydration reaction in the synthesis of a fat Ester linkage (b) Fat molecule (triacylglycerol)

Structural formula of a saturated fat molecule Stearic acid, a Fig. 5-12 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 cis double bond causes bending (b) Unsaturated fat

Choline Phosphate Hydrophilic head Glycerol Fatty acids Fig. 5-13ab Choline Phosphate Hydrophilic head Glycerol Fatty acids Hydrophobic tails (a) Structural formula (b) Space-filling model

Fig. 5-15

Questions Why are proteins the most complex biological molecules? Draw the structure of a general amino acid.  Label the carboxyl group, the amino group, and the variable (‘R’) group. Draw the formation of a peptide bond between two amino acids. How does the structure of the ‘R’ group affect the properties of a particular amino acid? Define each of the following levels of protein structure and explain the bonds that contribute to them: Primary Secondary Tertiary Quaternary How can the structure of a protein be changed (“denatured”)? Draw a nucleotide.  Label the phosphate, sugar, and nitrogenous base. Explain the three major structural differences between RNA and DNA.

Table 5-1

Fig. 5-UN1  carbon Amino group Carboxyl group

Fig. 5-21b +H3N Amino end Amino acid subunits Carboxyl end 1 5 10 15 20 25 75 80 85 90 95 105 100 110 115 120 125 Carboxyl end

Secondary Structure  pleated sheet Examples of amino acid subunits Fig. 5-21c Secondary Structure  pleated sheet Examples of amino acid subunits  helix

Tertiary Structure Quaternary Structure Fig. 5-21e Tertiary Structure Quaternary Structure

Hydrophobic interactions and van der Waals interactions Polypeptide Fig. 5-21f Hydrophobic interactions and van der Waals interactions Polypeptide backbone Hydrogen bond Disulfide bridge Ionic bond

Polypeptide  Chains chain Iron Heme  Chains Hemoglobin Collagen Fig. 5-21g Polypeptide chain  Chains Iron Heme  Chains Hemoglobin Collagen

DNA 1 Synthesis of mRNA in the nucleus mRNA NUCLEUS CYTOPLASM mRNA 2 Fig. 5-26-3 DNA 1 Synthesis of mRNA in the nucleus mRNA NUCLEUS CYTOPLASM mRNA 2 Movement of mRNA into cytoplasm via nuclear pore Ribosome 3 Synthesis of protein Amino acids Polypeptide

(a) Polynucleotide, or nucleic acid (c) Nucleoside components: sugars Fig. 5-27 5 end Nitrogenous bases Pyrimidines 5C 3C Nucleoside Nitrogenous base Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Purines Phosphate group Sugar (pentose) 5C Adenine (A) Guanine (G) 3C (b) Nucleotide Sugars 3 end (a) Polynucleotide, or nucleic acid Deoxyribose (in DNA) Ribose (in RNA) (c) Nucleoside components: sugars

(c) Nucleoside components: nitrogenous bases Fig. 5-27c-1 Nitrogenous bases Pyrimidines Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Purines Adenine (A) Guanine (G) (c) Nucleoside components: nitrogenous bases

(c) Nucleoside components: sugars Fig. 5-27c-2 Sugars Deoxyribose (in DNA) Ribose (in RNA) (c) Nucleoside components: sugars

5' end 3' end Sugar-phosphate backbones Base pair (joined by Fig. 5-28 5' end 3' end Sugar-phosphate backbones Base pair (joined by hydrogen bonding) Old strands Nucleotide about to be added to a new strand 3' end 5' end New strands 5' end 3' end 5' end 3' end

Fig. 5-UN2

Fig. 5-UN2a

Fig. 5-UN2b