BSC Exam I Lectures and Text Pages I. Intro to Biology (2-29) II. Chemistry of Life – Chemistry review (30-46) – Water (47-57) – Carbon (58-67) – Macromolecules (68-91) III. Cells and Membranes – Cell structure (92-123) – Membranes ( ) IV. Introductory Biochemistry – Energy and Metabolism ( ) – Cellular Respiration ( ) – Photosynthesis ( )

The Chemistry of Carbon (Ch. 4) Carbon can bond to carbon: and form long chains or ring structures Carbon can bond: to many different functional groups.

Carbon—The Backbone of Biological Molecules All living organisms – Are made up of chemicals based mostly on the element carbon Figure 4.1

Carbon atoms can bond to four other atoms Carbon has four valence electrons This allows it to form four covalent bonds with a variety of atoms, and to form large complex molecules.

Molecular Diversity Arising from Carbon Skeleton Variation Carbon chains – Form the skeletons of most organic molecules – Vary in length and shape H H H H H H H H H H H HHH H H H H H H H H H H H H H H H H HH H H HH HHH H HH HH H H H H H H H C C CCC CCCCCCC CCCCCCCC C C C C C C C C C C C C H H H H H H H (a) Length (b) Branching (c) Double bonds (d) Rings Ethane Propane Butane 2-methylpropane (commonly called isobutane) 1-Butene2-Butene Cyclohexane Benzene HH HHH Figure 4.5 A-D

The electron configuration of carbon Gives it covalent compatibility with many different elements H O NC Hydrogen (valence = 1) Oxygen (valence = 2) Nitrogen (valence = 3) Carbon (valence = 4) Figure 4.4

Hydrocarbons are molecules consisting of only carbon and hydrogen Hydrocarbons – Are found in many of a cell’s organic molecules (a) A fat molecule (b) Mammalian adipose cells 100 µm Fat droplets (stained red) Figure 4.6 A, B

Functional groups = chemically reactive groups of atoms within a molecule – Give organic molecules distinctive chemical properties CH 3 OH HO O CH 3 OH Estradiol Testosterone Female lion Male lion Figure 4.9

Functional Groups Engage in Chemical Reactions Six functional groups are important in the chemistry of life – Hydroxyl -OH; alcohols – Carbonyl >CO; aldehydes and ketones – Carboxyl -COOH; carboxylic (organic) acids – Amino –NH 2 ; amines – Sulfhydryl -SH; thiols – Phosphate –OPO 3 2- ; organic phosphates

BSC Exam I Lectures and Text Pages I. Intro to Biology (2-29) II. Chemistry of Life – Chemistry review (30-46) – Water (47-57) – Carbon (58-67) – Macromolecules (68-91) III. Cells and Membranes – Cell structure (92-123) – Membranes ( ) IV. Introductory Biochemistry – Energy and Metabolism ( ) – Cellular Respiration ( ) – Photosynthesis ( )

Macromolecules – Structure and Function (Ch. 5) Another level in the hierarchy of biological organization is reached when small organic molecules are joined together. Macromolecules are large molecules composed of smaller molecules, and they can be very complex in structure. Figure 5.1

Macromolecules – Structure and Function (Ch. 5) 4 main classes of carbon-based molecules necessary to life 1. Carbohydrates – sugars and their polymers 2. Lipids – diverse group of nonpolar molecules 3. Proteins – polymers of amino acids 4. Nucleic Acids –polymers of nucleotides

Most macromolecules are polymers, built from monomers Three of the classes of life’s organic molecules are polymers – Carbohydrates – Proteins – Nucleic acids A polymer is a long molecule consisting of many similar building blocks called monomers

The Synthesis of Polymers Monomers form larger molecules by condensation reactions called dehydration reactions (a) Dehydration reaction in the synthesis of a polymer HOH H H H2OH2O Short polymer Unlinked monomer Longer polymer Dehydration removes a water molecule, forming a new bond Figure 5.2A

The Breakdown of Polymers Polymers can disassemble by – Hydrolysis (b) Hydrolysis of a polymer HO H H H2OH2O H Hydrolysis adds a water molecule, breaking a bond Figure 5.2B

Carbohydrates Carbohydrates include both sugars and their polymers Carbohydrates serve as immediate fuel, energy storage, and building material.

Sugars Monosaccharides – the monomers of carbohydrates – Are the simplest sugars – Can be used for fuel – Can be converted into other organic molecules – Can be combined into polymers

Examples of monosaccharides Triose sugars (C 3 H 6 O 3 ) Pentose sugars (C 5 H 10 O 5 ) Hexose sugars (C 6 H 12 O 6 ) H C OH HO C H H C OH HO C H H C OH C O H C OH HO C H H C OH C O H H H HHH H H HHH H H H C CCC O O O O Aldoses Glyceraldehyde Ribose Glucose Galactose Dihydroxyacetone Ribulose Ketoses Fructose Figure 5.3

Monosaccharides May be linear, or can form rings H H C OH HO C H H C OH H C O C H H OH 4C4C 6 CH 2 OH 5C5C H OH C H OH H 2 C 1C1C H O H OH 4C4C 5C5C 3 C H H OH OH H 2C2C 1 C OH H CH 2 OH H H OH HO H OH H (a) Linear and ring forms. Chemical equilibrium between the linear and ring structures greatly favors the formation of rings. To form the glucose ring, carbon 1 bonds to the oxygen attached to carbon 5. OH 3 O H O O 6 1 Figure 5.4

Disaccharides = dimers Disaccharides – Consist of two monosaccharides – Are joined by a glycosidic linkage

Examples of disaccharides Dehydration reaction in the synthesis of maltose. The bonding of two glucose units forms maltose. The glycosidic link joins the number 1 carbon of one glucose to the number 4 carbon of the second glucose. Joining the glucose monomers in a different way would result in a different disaccharide. Dehydration reaction in the synthesis of sucrose. Sucrose is a disaccharide formed from glucose and fructose. Notice that fructose, though a hexose like glucose, forms a five-sided ring. (a) (b) H HO H H OH H OH O H CH 2 OH H HO H H OH H OH O H CH 2 OH H O H H OH H OH O H CH 2 OH H H2OH2O H2OH2O H H O H HO H OH O H CH 2 OH HO OH H CH 2 OH H OH H H HO OH H CH 2 OH H OH H O O H OH H CH 2 OH H OH H O H OH CH 2 OH H HO O CH 2 OH H H OH O O – 4 glycosidic linkage 1–2 glycosidic linkage Glucose Fructose Maltose Sucrose OH H H Figure 5.5

Polysaccharides – polymers Polysaccharides – Are polymers of sugars – Serve many roles in organisms – May be 100s to 1000s of monomers

Storage Polysaccharides Starch – Is the major storage form of glucose in plants – Is a polymer consisting entirely of glucose monomers Chloroplast Starch Amylose Amylopectin 1  m (a) Starch: a plant polysaccharide Figure 5.6

Storage Polysaccharides Glycogen – Consists of glucose monomers – Is the major storage form of glucose in animals Mitochondria Giycogen granules 0.5  m (b) Glycogen: an animal polysaccharide Glycogen Figure 5.6

Structural Polysaccharides - Cellulose – Is a polymer of glucose – Has different glycosidic linkages than starch (c) Cellulose: 1– 4 linkage of  glucose monomers H O O CH 2 O H H OH H H H H HO 4 C C C C C C H H H OH H H O CH 2 O H H H H OH H H HO 4 OH CH 2 O H O OH HO 4 1 O CH 2 O H O OH O CH 2 O H O OH CH 2 O H O OH O O CH 2 O H O OH HO 4 O 1 OH O O CH 2 O H O OH O O (a)  and  glucose ring structures (b) Starch: 1– 4 linkage of  glucose monomers 1  glucose  glucose CH 2 O H Figure 5.7 A–C

Cellulose Plant cells 0.5  m Cell walls Cellulose microfibrils in a plant cell wall  Microfibril CH 2 OH OH OHOH O O O CH 2 OH O O OH O CH 2 OH OH O O CH 2 OH O O OHOH O O OHOH O O OH CH 2 OHOH O O CH 2 OH OH O CH 2 OH O O OHCH 2 OH OH  Glucose monomer O O O O O O Parallel cellulose molecules are held together by hydrogen bonds between hydroxyl groups attached to carbon atoms 3 and 6. About 80 cellulose molecules associate to form a microfibril, the main architectural unit of the plant cell wall. A cellulose molecule is an unbranched  glucose polymer. OH O O Cellulose molecules Figure 5.8 – Is a major component of the tough walls that enclose plant cells

Cellulose Cellulose is difficult to digest – Cows have microbes in their stomachs to facilitate this process Figure 5.9

Chitin – an animal structural polysaccharide – Is found in the exoskeleton of arthropods – Can be used as surgical thread (a) The structure of the chitin monomer. O CH 2 O H OH H H H NH C CH 3 O H H (b) Chitin forms the exoskeleton of arthropods. This cicada is molting, shedding its old exoskeleton and emerging in adult form. (c) Chitin is used to make a strong and flexible surgical thread that decomposes after the wound or incision heals. OH Figure 5.10 A–C

Lipids Lipids, a diverse group of hydrophobic molecules – Are the one class of large biological molecules that do not consist of polymers – Share the common trait of being hydrophobic – Are fats, oils, waxes and other biologically important molecules

Fats Fats, oils and waxes – Are constructed from two types of smaller molecules, a single glycerol and usually three fatty acids (b) Fat molecule (triacylglycerol) H H H H H H H H H H H H H H H H O Figure 5.11

Fatty acids – Can be saturated or unsaturated – Vary in the length and number and locations of double bonds they contain

Saturated fatty acids – Have the maximum number of hydrogen atoms possible – Have no double bonds (a) Saturated fat and fatty acid Stearic acid Figure 5.12

- Have one or more double bonds - and are thus not “saturated” with the maximum number of hydrogens (b) Unsaturated fat and fatty acid cis double bond causes bending Oleic acid Figure 5.12 Unsaturated fatty acids

Phospholipids Phospholipids (major part of membranes) – Have only two fatty acids – Have a phosphate group instead of a third fatty acid

Phospholipid structure – Consists of a hydrophilic “head” and hydrophobic “tails” (amphipathic) CH 2 O P O O O CH CH 2 OO C O C O Phosphate Glycerol (a) Structural formula (b) Space-filling model Fatty acids (c) Phospholipid symbol Hydrophobic tails Hydrophilic head Hydrophobic tails – Hydrophilic head CH 2 Choline + Figure 5.13 N(CH 3 ) 3

Cell Membranes The structure of phospholipids – Results in a bilayer arrangement found in cell membranes Hydrophilic head WATER Hydrophobic tail Figure 5.14

Steroids – lipids characterized by four fused carbon rings One steroid, cholesterol – Is found in cell membranes – Is a precursor for some hormones HO CH 3 H3CH3C Figure 5.15

Steroid Hormones – important chemical messengers Cholesterol is the precursor to many important hormones: estrogen, testosterone, and progesterone. Testosterone is the major anabolic steroid, leads to muscle formation, plays a role in sexual drive in the brain. Testosterone can be converted to estrogen, which signals cells to divide. Steroids are also important in bile acids.

Prostaglandins non-steroid lipid-based hormones important to the inflammatory response and pain. important in the birth process. precursor- arachidonic acid.