The Chemical Basis of The Chemical Basis of LifeLife

Basic ChemistryBasic Chemistry

Matter: anything that has mass and takes up Matter: anything that has mass and takes up spacespace

Element: simple form of matter, a substance Element: simple form of matter, a substance that cannot be broken down into two or that cannot be broken down into two or more different substancesmore different substances26 elements in the human body26 elements in the human body

11 major elements11 major elements15 trace elements15 trace elements

Compound: atoms of two or more elements Compound: atoms of two or more elements joined to form chemical combinationsjoined to form chemical combinations

96% of the human body is made up of96% of the human body is made up of

1.1. CarbonCarbon

2.2. OxygenOxygen

3.3. HydrogenHydrogen

4.4. NitrogenNitrogen

ESSENTIAL ELEMENTS

ElementElement SymbolSymbol % by Mass% by Mass ElementElement SymbolSymbol % by Mass% by Mass

OxygenOxygen OO 65.065.0 IronIron FeFe TraceTrace

CarbonCarbon CC 18.518.5 ZincZinc ZnZn TraceTrace

HydrogenHydrogen HH 9.59.5 CopperCopper CuCu TraceTrace

NitrogenNitrogen NN 3.33.3 IodineIodine II TraceTrace

CalciumCalcium CaCa 1.51.5 ManganeseManganese MnMn TraceTrace

PhosphorusPhosphorus PP 1.01.0 BoronBoron BB TraceTrace

PotassiumPotassium KK 0.40.4 ChromiumChromium CrCr TraceTrace

SulfurSulfur SS 0.30.3 MolybdenuMolybdenumm

MoMo TraceTrace

SodiumSodium NaNa 0.20.2 CobaltCobalt CoCo TraceTrace

ChlorineChlorine ClCl 0.20.2 SelenimSelenim SeSe TraceTrace

MagnesiumMagnesium MgMg 0.10.1 FlourineFlourine FF TraceTrace

Atoms StructureAtoms Structure

Protons: +Protons: +

Electrons: –Electrons: –

Neutrons: no chargeNeutrons: no charge

Atomic Number = Atomic Number = proton numberproton number

Atomic Mass = Atomic Mass = protons + neutronsprotons + neutrons

Chemical BondsChemical Bonds

1.1. Ionic or electrovalent bondIonic or electrovalent bond: formed : formed by a transfer of electrons; by a transfer of electrons; electrostatic force binds positively electrostatic force binds positively and negatively charged ions togetherand negatively charged ions together

2.2. Covalent bondCovalent bond: formed by sharing of : formed by sharing of electron pairs between atomselectron pairs between atoms

3.3. Hydrogen bondHydrogen bond: weak bond; results : weak bond; results from unequal charge distribution on from unequal charge distribution on moleculesmolecules

Chemical BondsChemical Bonds

Chemical BondsChemical Bonds

Ionic Bond

Chemical BondsChemical Bonds

Covalent Bond

Chemical BondsChemical Bonds

Chemical ReactionsChemical Reactions

There are 3 basic types of chemical reactions There are 3 basic types of chemical reactions involved in physiology:involved in physiology:

1.1. Synthesis reaction (dehydration Synthesis reaction (dehydration synthesis)synthesis): combining of two or more : combining of two or more substances to form a more complex substances to form a more complex substance; A+B ABsubstance; A+B AB

2.2. Decomposition reaction (hydrolysis)Decomposition reaction (hydrolysis): : breaking down of a substance into two or breaking down of a substance into two or more substances; more substances;

AB A+BAB A+B1.1. Exchange reactionExchange reaction: decomposition of two : decomposition of two

substances and, in exchange, synthesis of substances and, in exchange, synthesis of two new compounds; AB+CD AD+BCtwo new compounds; AB+CD AD+BC

MetabolismMetabolism

MetabolismMetabolism——all of the chemical all of the chemical reactions that occur in body cells reactions that occur in body cells

CatabolismCatabolism Ultimately, the end products of catabolism are Ultimately, the end products of catabolism are

carbon dioxide, water, and other waste carbon dioxide, water, and other waste productsproducts

More than half the energy released is More than half the energy released is transferred to ATP, which is then used to do transferred to ATP, which is then used to do cellular workcellular work

Chemical reactions that break down complex Chemical reactions that break down complex compounds into simpler ones and release compounds into simpler ones and release energy; energy; hydrolysishydrolysis (decomposition) (decomposition) is a is a common catabolic reactioncommon catabolic reaction

MetabolismMetabolism

AnabolismAnabolism Chemical reactions that join simple Chemical reactions that join simple

molecules together to form more molecules together to form more complex moleculescomplex molecules

Chemical reaction responsible for Chemical reaction responsible for anabolism is anabolism is dehydration synthesisdehydration synthesis

Inorganic CompoundsInorganic Compounds

1.1. Water: Body’s most abundant Water: Body’s most abundant compoundcompound

2.2. Oxygen and Carbon DioxideOxygen and Carbon Dioxide

3.3. Electrolytes: acids, bases, and salts: Electrolytes: acids, bases, and salts: dissociate in solutions to form ionsdissociate in solutions to form ions

4.4. Buffers: maintain the constancy of Buffers: maintain the constancy of the pHthe pH

Organic CompoundsOrganic Compounds

Organic moleculesOrganic molecules Have at least one carbon atom and at Have at least one carbon atom and at

least one Cleast one C––C or CC or C––H bond in each H bond in each moleculemolecule

Often have functional groups attached Often have functional groups attached to the carbon-containing core of the to the carbon-containing core of the molecule molecule

Organic CompoundsOrganic Compounds

Sugars, starches and cellulose are carbohydrates.

Sugars and starches serve as energy sources for cells; cellulose is the main structural component of the walls that surround plant cells.

Carbohydrates contain carbon, hydrogen, and oxygen in a ratio of two hydrogen and one oxygen to every carbon atom.

Typically contain 3 to 7 carbon atoms.

Large numbers of polar hydroxyl groups, plus a carbonyl group, gives a monosaccharide hydrophilic properties.

Glucose (C6H12O6), the most abundant monosaccharide, is used as an energy source in most organisms.

Glucose is so important in metabolism that its concentration is carefully kept at a homeostatic level in the blood of humans and other complex animals.

When dissolved in water, glucose undergoes a rearrangement of its atoms, forming one of two possible ring structures.

When the hydroxyl group is on the plane of the ring as the –CH2OH side group, the glucose is designated beta-glucose.

When its on the side opposite the -- CH2OH side group, the compound is designated alpha-glucose.

A disaccharide contains two monosaccharide rings joined by a glycosidic linkage, consisting of a central oxygen covalently bonded to two carbons, one in each ring.

The most abundant carbohydrates are polysaccharides. A group that includes starches, glycogen, and cellulose.

A polysaccharide is a macromolecule consisting of repeating units of simple sugars, usually glucose. Thousands of units are typically present in a single molecule.

Starch, the typical form of carbohydrate used for energy storage in plants, is a polymer consisting of a-glucose subunits. When energy is needed for cellular work, the plant can hydrolyze the starch, releasing the glucose subunits.

Humans and other animals that eat plant foods have enzymes to hydrolyze starch.

Glycogen (sometimes referred to as animal starch) is the form which glucose is stored as energy sources in animal tissues.

It is more extensively branched and more water soluble.

Glycogen is stored mainly in the liver and muscle cells.

Cellulose is the most abundant carbohydrate; it accounts for 50% or more of all the carbon in plants.

Cellulose is a structural carbohydrate.

Cellulose is an insoluble polysaccharide composed of many glucose molecules joined together.

Humans do not have the enzymes needed to break down cellulose.

Carbohydrates may also be combined with proteins to form glycoproteins, compounds present on the outer surface of cells other than bacteria.

Some of these carbohydrate chains allow cells to adhere to one another, while others provide protection

Carbohydrates can also combine with lipids to form glycolipids, compounds present on the surface of animal cells that are thought to allow cells to recognize and interact with one another.

Most proteins secreted by cells are glycoproteins. These include the major components of mucus.

The most abundant lipids in living organisms are triacyglycerols, also known as triglycerides.

These compounds commonly known as fats, are an economical form of reserve fuel storage because, when metabolized, they yield more than twice as much energy per gram as do carbohydrates

Saturated fatty acids contain the maximum possible number of hydrogen atoms.

Fats high in saturated fatty acids, such as animal fat and solid vegetable shortening, tend to be solid at room temperature

Unsaturated fatty acids include one or more adjacent pairs of carbon atoms joined by a double bond. They tend to be liquid at room temperature.

Fatty acids with one double bond are called monounsaturated fatty acids.

Those with more than one double bond are polyunsaturated fatty acids.

At least two unsaturated fatty acids (linoleic acid and arachidonic acid) are essential nutrients that must be obtained from food because the human body cannot make them.

Phospholipids belong to a group of lipids, called amphipathic lipids, in which one end of each molecule is hydrophobic and the other end is hydrophilic.

The properties of these lipid molecules cause them to form lipid bilayers in aqueous solution, making them uniquely suited to function as the functional components of cell membranes.

linoleic acid

Name% LA†ref.Name% LA†ref.Safflower oil78%78%Grape seed oil73%73%Poppyseed oil70%70%Sunflower oil68%68%Hemp oil60%60%Corn oil59%59%Wheat germ oil55%55%Cottonseed oil54%54%Soybean oil51%51%Walnut oil51%51%Sesame oil45%45%Rice bran oil39%39%Pistachio oil32.7%Peanut oil32%[17]Canola 32.7%Peanut oil32%[17]Canola oil21%Chicken fat18-23%[18]Egg oil21%Chicken fat18-23%[18]Egg yolk16%Linseed oil15%Lard10%Olive yolk16%Linseed oil15%Lard10%Olive oil10%Palm oil10%Cocoa oil10%Palm oil10%Cocoa butter3%Macadamia butter3%Macadamia oil2%Butter2%Coconut oil2% oil2%Butter2%Coconut oil2% 

arachidonic acid

Meat, eggs and dairyMeat, eggs and dairy Synthesized from Synthesized from linoleic acid

Lipids are a group of compounds that are defined, not by their structure, but rather by the fact that they are soluble in nonpolar solvents (ether and chloroform) and are relatively insoluble in water (hydrophobic).

They consists mainly of carbon and hydrogen, with few oxygen-containing functional groups.

Groups of lipids are fats, phospholipids, caratenoids, steroids, and waxes.

The orange and yellow plant pigments called carotenoids are classified with lipids because they are insoluble in water and have an oily consistency.

Most animals can convert carotenoids to vitamin A, which can then be converted to the visual pigment retinal.

A steriod consists of carbon atoms arranged in four attached rings; three of the rings contain six carbon atoms, and the fourth contains five

The length and structure of the side chains that extend from these rings distinguish one steroid from another.

Among the steroids of biological importance are cholesterol, bile salts, reproductive hormones, and cortisol and other hormones secreted by the adrenal cortex

Cholesterol is an essential structural component of animal cell membranes, but when there is excess cholesterol in the blood it forms plaques on artery walls. Leading to an increased risk of heart attack.

Plant cell membranes contain molecules similar to cholesterol. Some of these plant steroids are able to block the absorption of cholesterol by the intestines.

Bile salts emulsify fats in the intestine so that they can be enzymatically hydrolyzed.

Steroid hormones regulate certain aspects of metabolism in a variety of animals.

Most genetic information is used to specify the structure of proteins.

Proteins are involved in virtually all aspects of metabolism because most enzymes (molecules that regulate the thousands of different chemical reactions that take place in an organism) are proteins.

Proteins can be assembled into a variety of shapes, allowing them to serve as major structural components of cells and tissues.

For this reason, growth and repair, as well as maintenance of the organism, depend on these compounds.

The protein constituents of a cell are the clues to its lifestyle.

Each cell type contains characteristic forms, distributions, and amounts of protein that largely determine what the cell looks like and how it functions.

Amino acids, the constituents of proteins, have an amino group (--NH2) and a carboxyl group (--COOH) bonded to the same asymmetrical carbon atom, know as the alpha carbon.

Amino acids classified as having nonpolar side chains tend to have hydrophobic properties, whereas those classified as polar are more hydrophilic.

With some exceptions, bacteria and plants can synthesize all their needed amino acids from simpler substances.

If the proper raw materials are available, the cells of humans and animals can manufacture some, but not all, of the biologically significant amino acids.

Those that animals cannot synthesize and so must obtain from the diet are known as essential amino acids.

There are about 20 amino acids commonly found in proteins, each uniquely identified by the variable side chain (R group) bonded to the a-carbon

Polar Amino Acids

Nonpolar Amino Acids

Electrically Charged Amino Acids

Acidic

Basic

Amino acids combine chemically with one another by a condensation reaction that bonds the carboxyl carbon of one molecule with the amino nitrogen of another.

The covalent carbon-to-nitrogen bond linking two amino acids together is called a peptide bond.

When two amino acids combine, a dipeptide is formed; a long chain of amino acids is a polypeptide.

An almost infinite variety of protein molecules is possible, differing from one another in the number, types, and sequences of amino acids they contain.

The overall structure of a protein helps determine its biological activity.

The biological activity of a protein can be disrupted by a change in conformation.

When a protein is heated, subjected to significant pH changes, or treated with a number of chemicals, its structure can become disordered and the coiled peptide chains can unfold to give a more random conformation.

Such changes in shape and the accompanying loss of biological activity are termed denaturation of the protein.

Denaturation generally cannot be reversed (you can’t “unfry” an egg).

Nucleic acids transmit hereditary information and determine what proteins a cell manufactures.

Ribonucleic acids (RNAs)

Deoxyribonucleic Acids (DNAs)

DNA comprises the genes, the hereditary material of the cell, and contains all the instructions for making proteins, as well as all the RNA, needed by the organism.

RNA is required as a direct participant in the complex process in which amino acids are linked to form polypeptides.

Nucleic acids are polymers of nucleotides, molecular units that consist of: 1. A five carbon sugar, either ribose (in RNA) or deoxyribose (in DNA)

2. One or more phosphate groups, which make the molecule acidic

3. A nitrogenous base, a ring compound that contains nitrogen. The base may either be a double-ringed purine or a single-ringed pyrimidine

Adenosine triphosphate (ATP), composed of adenine, ribose, and three phosphates , is a major importance as the primary energy currency of all cells.

The two terminal phosphate groups are joined to the nucleotide by covalent bonds.