wood is mostly celluloseplant cell with cell wallclose-up of cell wall cellulose fiber Hydrogen bonds cross-linking cellulose molecules individual cellulose molecules bundle of cellulose molecules H O O H O O H O H O OO HH O H OH H H H H H H H H H H H HH CH 2 OH 2.6 What Are Carbohydrates? Cellulose structure Fig. 2-15

2.6 What Are Carbohydrates? Animation—Carbohydrate Functions PLAY Animation—Structure Determines Function PLAY

2.7 What Are Lipids? Molecular characteristics of lipids – Lipids are molecules with long regions composed almost entirely of carbon and hydrogen. – The nonpolar regions of carbon and hydrogen bonds make lipids hydrophobic and insoluble in water.

2.7 What Are Lipids? Lipid classification – Group 1: Oils, fats, and waxes – Group 2: Phospholipids – Group 3: Steroids

2.7 What Are Lipids? Group 1: Oils, fats, and waxes – Contain only carbon, hydrogen, and oxygen – Contain one or more fatty acid subunits—long chains of C and H with a carboxyl group (–COOH) – They usually do not have a ring structure.

2.7 What Are Lipids? Group 1: Oils, fats, and waxes (continued) – Fats and oils form by dehydration synthesis from three fatty acid subunits and one molecule of glycerol. Fig glycerol fatty acids CH 2 CHOCH 2 etc. O CH 2 CHOCH 2 etc. O CH 2 CHOCH 2 CH O C OHH H C H C H H CH 2 CH CH 2 etc. +

triglyceride 3 water molecules O HH O HH O H H + + CH 2 C etc. O CH 2 C etc. O CH 2 C CH O CH H CH C O O OH H CH 2 CH CH 2 etc What Are Lipids? Group 1: Oils, fats, and waxes (continued) – Fats and oils formed by dehydration synthesis are called triglycerides. – Triglycerides are used for long-term energy storage in both plants and animals. Fig. 2-16

2.7 What Are Lipids? Animation—Lipids PLAY

2.7 What Are Lipids? Group 1: Oils, fats, and waxes (continued) – Characteristics of fats Fats are solid at room temperature. Fats have all carbons joined by single covalent bonds. The remaining bond positions on the carbons are occupied by hydrogen atoms.

Beef fat (saturated) (a) 2.7 What Are Lipids? Group 1: Oils, fats, and waxes (continued) – Fatty acids of fats are said to be saturated and are straight molecules that can be stacked. Fig. 2-18a

2.7 What Are Lipids? Group 1: Oils, fats, and waxes (continued) – Characteristics of oils Oils are liquid at room temperature. Some of the carbons in fatty acids have double covalent bonds. There are fewer attached hydrogen atoms, and the fatty acid is said to be unsaturated.

2.7 What Are Lipids? Group 1: Oils, fats, and waxes (continued) – Unsaturated fatty acids have bends and kinks in fatty acid chains and can’t be stacked. Fig. 2-18b Peanut oil (unsaturated) (b)

2.7 What Are Lipids? Group 1: Oils, fats, and waxes (continued) – Characteristics of waxes Waxes are solid at room temperature. Waxes are highly saturated. Waxes are not a food source. Waxes form waterproof coatings over plant leaves and stems.

2.7 What Are Lipids? Group 1: Oils, fats, and waxes (continued) – Bees use waxes to store food and honey. Fig. 2-17b

2.7 What Are Lipids? Animation—Lipid Function PLAY

2.7 What Are Lipids? Group 2: Phospholipids – Phospholipids have water-soluble heads and water- insoluble tails. – They are found in cell membranes in a double layer. – They are like oils except one fatty acid is replaced by a phosphate group attached to glycerol.

polar headglycerol (hydrophilic)(hydrophobic) fatty acid tails CH 3 O–O– O O CH CH 2 CH 3 H3CH3CN+N+ -CH 2 - -O-P-O- O HC-O-C-CH CH H2CH2C-O-C-CH CH What Are Lipids? Group 2: Phospholipids (continued) – The phosphate end of the molecule is water soluble; the fatty acid end of the molecule is water insoluble. Fig. 2-19

2.7 What Are Lipids? Group 3: Steroids – Steroids contain four carbon rings fused together. – Various functional groups protrude from the basic steroid “skeleton”. – Cholesterol is a steroid found in cell membranes.

Cholesterol Testosterone Estrogen HC HO OH HO OH O (a)(c) (b) CH 3 CH 2 CH What Are Lipids? Group 3: Steroids – Testosterone and estrogen are male and female reproductive hormones, respectively, and are steroids. Fig. 2-20

2.8 What Are Proteins? Functions of proteins – Proteins act as enzymes to catalyze many biochemical reactions. – They can act as energy stores. – They are involved in carrying oxygen around the body. – They are involved in muscle movement.

2.8 What Are Proteins? Some proteins are structural and provide support in hair, horns, spider webs, etc. Fig. 2-21

2.8 What Are Proteins? Proteins are formed from chains of amino acids. – All amino acids have the same basic structure: – A central carbon – An attached amino group – An attached carboxyl group – An attached variable side group

2.8 What Are Proteins? Amino acid structure Fig amino group hydrogen variable group carboxylic acid group O O CC N R H H H H

2.8 What Are Proteins? Amino acids join to form chains by dehydration synthesis. – Proteins are formed by dehydration reactions between individual amino acids. – The –NH 2 group of one amino acid is joined to the – COOH group of another, with the release of H 2 O and the formation of a new peptide (two or more amino acids).

2.8 What Are Proteins? More and more individual amino acids are added to the peptide until a polypeptide (protein) is formed. Fig amino acid amino group carboxylic acid group amino acidpeptide water peptide bond H H HH H H H H HH H H H H H H ++ O O O R O N NN R CCCC O O R CC N O O R CC

2.8 What Are Proteins? Animation—Proteins PLAY

2.8 What Are Proteins? Three-dimensional shapes give proteins their functions. – Long chains of amino acids fold into three- dimensional shapes in cells, which allows the protein to perform its specific functions. – When a protein is denatured, its shape has been disrupted and it may not be able to perform its function.

2.8 What Are Proteins? Fig helix hydrogen bond (a) Primary structure: The sequence of amino acids linked by peptide bonds (c) Tertiary structure: Folding results from bonds with surrounding water molecules and between amino acids (d) Quaternary structure: Individual polypeptides are linked to one another (b) Secondary structure: Folding usually maintained by hydrogen bonds leu lys gly ala lys val pro his O O O O C C C C N H N N H C O C N H O C N H C C C C C C N H N H O O C C C C C N H N H O O H C C C N H N H O H R

2.8 What Are Proteins? Animation—Protein Function PLAY

2.9 What Are Nucleic Acids? Structure of nucleic acids – Nucleic acids are long chains of similar, but not identical, subunits called nucleotides.

2.9 What Are Nucleic Acids? Structure of nucleic acids (continued) – All nucleotides have three parts. A five-carbon sugar (ribose or deoxyribose) A phosphate group A nitrogen-containing molecule called a base

phosphate base sugar PO O O CH 2 H OH HH H H HO C N CH N C C N HC N NH What Are Nucleic Acids? Deoxyribose nucleotide Fig. 2-25

2.9 What Are Nucleic Acids? Types of nucleotides – Those that contain the sugar ribose. – Those that contain the sugar deoxyribose. – Nucleotides string together in long chains as nucleic acids with the phosphate group of one nucleotide bonded to the sugar group of another.

phosphate base sugar 2.9 What Are Nucleic Acids? Nucleotide chain Fig. 2-26

2.9 What Are Nucleic Acids? DNA and RNA, the molecules of heredity, are nucleic acids. – There are two types of nucleic acids. Deoxyribonucleic acid (DNA): contains the genetic code of cell Ribonucleic acid (RNA): is used in the synthesis of proteins

2.9 What Are Nucleic Acids? Animation—Nucleic Acids PLAY Animation—Nucleic Acids PLAY

2.9 What Are Nucleic Acids? Other nucleotides perform other functions. – Adenosine monophosphate: acts as a messenger in the cell, carrying information to other molecules – Adenosine triphosphate: carries energy from place to place in the cell