CHAPTERS 2 & 3 Continued The CHEMISTRY of LIFE. All Living Organisms are Highly Organized.

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1 CHAPTERS 2 & 3 Continued The CHEMISTRY of LIFE

2 All Living Organisms are Highly Organized

3 Cells make a huge number of large molecules from a small set of small molecules There are four classes of biological molecules –Carbohydrates –Proteins –Lipids –Nucleic acids Copyright © 2009 Pearson Education, Inc.

4 Cells make a huge number of large molecules from a small set of small molecules The four classes of biological molecules contain very large molecules –They are often called macromolecules because of their large size –They are also called polymers because they are made from identical building blocks strung together –The building blocks are called monomers Copyright © 2009 Pearson Education, Inc.

5 Cells make a huge number of large molecules from a small set of small molecules Monomers are linked together to form polymers through dehydration reactions, which remove water Polymers are broken apart by hydrolysis, the addition of water All biological reactions of this sort are mediated by enzymes, which speed up chemical reactions in cells Copyright © 2009 Pearson Education, Inc.

6 Unlinked monomer Short polymer Longer polymer Dehydration reaction

7 Hydrolysis

8 CARBOHYDRATES Copyright © 2009 Pearson Education, Inc.

9 Monosaccharides are the simplest carbohydrates Carbohydrates range from small sugar molecules (monomers) to large polysaccharides –Sugar monomers are monosaccharides, such as glucose and fructose –These can be hooked together to form the polysaccharides Carbohydrates are water soluble (HYDROPHILIC) Polar Molecular Compounds Copyright © 2009 Pearson Education, Inc.

10 Monosaccharides are the simplest carbohydrates The carbon skeletons of monosaccharides vary in length –Glucose and fructose are six carbons long –Others have three to seven carbon atoms Monosaccharides are the main fuels for cellular work –Monosaccharides are also used as raw materials to manufacture other organic molecules Copyright © 2009 Pearson Education, Inc.

11 Glucose (an aldose) Fructose (a ketose)

12 Structural formula Abbreviated structure Simplified structure

13 Glucose Maltose

14 Polysaccharides are long chains of sugar units Starch is a storage polysaccharide composed of glucose monomers and found in plants Glycogen is a storage polysaccharide composed of glucose, which is hydrolyzed by animals when glucose is needed Cellulose is a polymer of glucose that forms plant cell walls Copyright © 2009 Pearson Education, Inc.

15 Starch granules in potato tuber cells Glycogen granules in muscle tissue Cellulose fibrils in a plant cell wall Cellulose molecules Glucose monomer GLYCOGEN CELLULOSE Hydrogen bonds STARCH

16 LIPIDS Copyright © 2009 Pearson Education, Inc.

17 Fats are lipids that are mostly energy-storage molecules Lipids are water insoluble (hydrophobic, or water fearing) nonpolar molecular compounds that are important in energy storage –They contain twice as much energy as a polysaccharide Fats are lipids made from glycerol and fatty acids Lipids are a main component of cell membranes Copyright © 2009 Pearson Education, Inc.

18 Fatty acid Glycerol

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20 Phospholipids are important lipids Phospholipids are structurally similar to fats and are an important component of all cells –For example, they are a major part of cell membranes, in which they cluster into a bilayer of phospholipids –The hydrophilic heads are in contact with the water of the environment and the internal part of the cell –The hydrophobic tails band in the center of the bilayer –They help to control the movement of substances in and out of cells Copyright © 2009 Pearson Education, Inc.

21 Water Hydrophobic tails Hydrophilic heads Water

22 PROTEINS Copyright © 2009 Pearson Education, Inc.

23 Proteins are essential to the structures and functions of life A protein is a polymer built from various combinations of 20 amino acid monomers –Proteins have unique structures that are directly related to their functions –Enzymes, proteins that serve as metabolic catalysts, regulate the chemical reactions (Metabolism) within cells –They are polar molecular compounds (Hydrophilic) Copyright © 2009 Pearson Education, Inc.

24 Carboxyl group Amino group

25 Carboxyl group Amino acid Amino group Amino acid Peptide bond Dipeptide Dehydration reaction

26 A protein’s specific shape determines its function A polypeptide chain contains hundreds or thousands of amino acids linked by peptide bonds –The amino acid sequence (Primary Structure) causes the polypeptide to assume a particular shape The shape of a protein determines its specific function If for some reason a protein’s shape is altered, it can no longer function –Denaturation will cause polypeptide chains to unravel and lose their shape and, thus, their function –Proteins can be denatured by changes in salt concentration, pH, and temperature Copyright © 2009 Pearson Education, Inc.

27 3.14 A protein’s shape depends on four levels of structure A protein can have four levels of structure –Primary structure –Secondary structure –Tertiary structure –Quaternary structure Copyright © 2009 Pearson Education, Inc.

28 Four Levels of Protein Structure Amino acids Primary structure Alpha helix Hydrogen bond Secondary structure Pleated sheet Polypeptide (single subunit of transthyretin) Tertiary structure Transthyretin, with four identical polypeptide subunits Quaternary structure

29 NUCLEIC ACIDS Copyright © 2009 Pearson Education, Inc.

30 Nucleic acids are information-rich (Genetic Material) polymers of nucleotides DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are Nucleic Acids (Hydrophilic/Polar Molecular Compounds) composed of monomers called nucleotides –Nucleotides have three parts –A five-carbon sugar called ribose in RNA and deoxyribose in DNA –A phosphate group –A nitrogenous base Copyright © 2009 Pearson Education, Inc.

31 Phosphate group Nitrogenous base (adenine) Sugar

32 Nucleic acids are information-rich polymers of nucleotides DNA nitrogenous bases are adenine (A), thymine (T), cytosine (C), and guanine (G) RNA also has A, C, and G, but instead of T, it has uracil (U) Copyright © 2009 Pearson Education, Inc.

33 Nucleic acids are information-rich polymers of nucleotides Two polynucleotide strands wrap around each other to form a DNA double helix –The two strands are associated because particular bases always bond to one another –A pairs with T, and C pairs with G –DNA (the genetic material) can make copies of itself RNA is usually a single polynucleotide strand – RNA acts as a messenger molecule Copyright © 2009 Pearson Education, Inc.

34 Base pair

35 Biological Molecule Smaller Molecular Unit(s) Polarity (Polar or Nonpolar) Reaction with Water (Hydrophilic or Hydrophobic) Major Cellular Function Carbohydrate Lipid (Specifically Fats or Triglycerides) Proteins Nucleic Acids