THE CHEMISTRY OF LIFE

Protoplasm – refers to the substance associated with life- substance out of which cells and organisms are made

The basic chemical components that made up the protoplasm are almost the same in almost all cells but they vary in proportion

CHEMICAL COMPOSITION

1. INORGANC COMPOUNDS•Are compounds that do not contain hydrocarbon. It also includes the oxides and sulfides of carbon

A. WATER- The most abundant protoplasmic compound

ranging from 35-90% of the weight of the protoplasm

- It is about 60-90%of most living organisms- By far, oxygen,hydrogen and carbon are the most

abundant elements in the body and account for 93% of its weight. Much of the oxygen and hydrogen is linked together as water molecules

CHARACTERISTICS OF WATER THAT IS IMPORTANT TO THE CELL:

1. Universal solvent2. Favors dissociation of an electrolyte3. Has a great fluidity which serves as a

vehicle for transport of materials4. High surfae tension5. High specific heat

Shown are water

molecules adhering to various ions (adhesion),

forming hydration shells

around them

Adhesion—Hydration Shells

Water resists evaporating (i.e., vaporizing) because hydrogen bonds must be broken in order for water to

transition from the liquid to the gas state H

IGH

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AT

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PO

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ION

B. MINERAL & MINERAL SALTS-present in the form of cat-ions and

anions.

* Cat-ions- K+ and Na+- for conduction of nerve

impulse- Mg+2 and Ca+2- for muscular contraction- Fe +2- for red blood cell formation

* Anions- PO4 - - necessary for nucleic acid

formation- HCO3

- - Control of pH in the blood

C. GASES- the most abundant are oxygen and

carbon dioxide

* Carbon dioxide – carried in three ways:1. 5% in solution in the plasma as carbonic acid2. 10% in combination with amino groups of hemoglobin3. 85% in the form of sodium and potassium bicarbonates (blood salts both in the plasma and RBC

* Oxygen -Carried by erythrocytes and partly by the plasma necessary during the oxidation process.

2. ORGANIC COMPOUNDS- compounds that contain carbon

except for the oxides and sulfides of carbon.

- The source of the vast diversity of organic molecules found in living things is the bonding capacity of just one of the 92 naturally occurring elements - CARBON

* Because life is built largely of Carbon atoms, macromolecules are large carbon-carbon molecules

•In building large macromolecules carbon usually combines with other carbons, H, O, N, P and sulfur, leading to almost endless variety of organic (carbon based) molecules

Organic Molecules fall into 4 groupings:1. Carbohydrates2. Lipids3. Proteins4. Nucleic Acids

CarbohydratesRole: energy storage, structural roleNot all carbons are macromolecules- some are small: Simple sugars

The macromolecular form is just a long chain of simple sugars

1. Monosaccharides- simple sugar with one 6-carbon sugars- E.g., glucose, dextrose, galactose, fructose and pentose (constituents of nucleic acids and nucleotides such as deoxyribose and ribose sugars)

2. Oligosaccharides (mostly disaccharides)- double sugar with two 6-carbon sugarsExamples:Glucose + galactose = lactoseGlucose + fructose = sucroseGlucose + glucose = maltose

3. Polysaccharides- a combination of more than 2

monosaccharides that is, a straight or branched chain of hundreds or thousands of sugar units of the same or different kinds

Examples:1. Cellulose – the structural material in plant cell

wall and consists of 2,000 united glucose units2. Glycogen – glucose-storage form that serves

as reserve food for animals and is made up of 12-16 glucose units

3. Starch- glucose- storage form that serves as reseve food for plants and is made up of 24-26 glucose units

Lipids:Fats & Oils

-insoluble in water, but soluble in organic solvents such as chloroform

-nonpolar and hence hydrophobic- contain higher proportion of hydrogen and much

smaller proportion oxygen- chemically composed of C, H, and O but they may

also contain other elements,particularly phosphorus and nitrogen

Examples include: Oils (olive, corn…),Waxes (bee’s, ear),Fats

Functions:1. True fats furnish concentated fuel of high-

energy value and represent an economical form of storage reserves in the body

2. Some phospholipids form part of the basic protoplasmic structure

Classes of lipids2. Fatty acids

- has a long unbranched carbon backbone with a –COOH group at the end-in living organisms usually contain an even number of carbon atoms

-The length of the chain affects the fluidity of the molecule; short chains are fluid at room temperature whereas long-chained fatty acids tend to be solid--C-C-C-C-C-C-C-C-C-C-C-COOH-Examples of lipids with fatty acids are:-1. glycerides – the body’s most abundant lipids and its richest surce of energy. With 1,2 or 3 fatty acid tails attached to a backbone of glycerol-2. Saturated fats- including butter and lard, which tend to be solids at room temperature. Saturated means all the C atoms in the fatty acid tails are joined by single C-C bonds ans as many H atoms as possible are linked to them

3. Unsaturated fats or oil

- tend to be liquid at room temperature. One or more double bonds occur between the C atoms in the fatty acid tails

- It is liquid because the double bonds create a “kink” that disrupt packing between tails thereby making the molecules less densely packed and move about more freely

- some amounts of unsaturated fats are important in nutrition (e.g., lenoleic acid for rats)

Sat

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–Sat

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Uns

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4. Waxes – Some wax secretions form coatings

that help protect, lubricate, and maintain the pliability of skin and hair while other help make feathers water repellant

II.Fats or triglycerides- fat molecules have twice as much

energy per unit weight as CHO, which is why the body’s energy requirements are met much more readily on a high-fat diet

Functions:1. Important as energy-storage molecules in

living organisms2. Provide insulation, cushioning and protection

for various parts of the bodyComposed of (building blocks):2. Glycerol

- also called glycerin with a backbone of 3 carbon atoms, each with hydroxyl group

2. 3 fatty acids- formed by condensation reaction or dehydration synthesis (reaction joining 2 compounds with resultant formation of water) of glycerol and 3 fatty acids

Fat

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–Cis

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Sat

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-In general, animal fats tend to be saturated while most vegetable fats (oil) are unsaturated.III. Phospholipids

- are lipids wherein the phosphate group substituted for one of the 3 FA

- among the most common are those composed of 1 unit of glycerol, 2 units of FA and 1 phosphate group

are sometimes calleed “schizophrenic” molecules because of their split personality-one end is soluble in water and the other end is not.

- The main structural component of the cell membrane

Phospholipids

IV. Steroids-differ markedly from fats, oils, and

phospholipids and are not formed from condensation reactions between FA and alcohols

- composed of 4 linked rings of C atoms with various side groups attached to the rings

- are classified as lipids because they are also soluble in organic solvents and relatively insoluble in waterCholesterol is a steroid that is:1. Important constituent of mammalian cell membranes

2. Used in the synthesis of vitamin D and certain hormones (e.g., sex hormones)

3. Proteins-Far more complex than carbohydrates and lipids-Play a leading role in both the structure and function of living organisms-Contains four essential elements: carbon, hydrogen, oxygen and nitrogen;most proteins also contain some sulfur.These elements are bonded together through condensation reaction to form the building block molecules called amino acids `

Fibrous protein (e.g., collagen)

Globular protein (e.g., hemoglobin)

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FIB

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Functions:1. Major components of muscles and are

responsible for muscle contraction (contractile proteins like actin & myosin)

2. For structural supportA. Elastin- gives the skin its elasticityB. Keratin- The principal protein of hair, horns

and claws including the silk of spider webs & silkmoth cocoons

3. Energy storage (albumin in eggs and casein in milk)

4. For oxygen transport in blood (hemoglobin)5. Immune response (antibodies)

6. Hormones (a control chemical sceted in one part of the body that effects other parts of the body) – e.g., insulin & growth hormones7. Catalysts of biological reaction (protein enzymes guide all chemica reactions that occur inside the cell)8. Poison (rattlesnake venom)

4. Nucleic acid-are the materials of which genes are made of- they are also the messenger substances that

convey information that governs the synthesis of proteins amd thereby determines the structural attributes of the cell and regulates the cell’s other functional activities

-Composed of the building blocks called nucleotides that are composed of: 5-carbon sugar, a phosphate group, and an organic nitrogen-containing base. Both the phosphate group and nitrogeneous base are covalently bonded to the sugar-- deoxyribonucleic acid acid (DNA) is the nucleic acid most genes are made of. It is compose of the following:-1. Deoxyribose (the sugar component)-2. Nitrogeneous bases-A. Purine(Double-ring structure)-1. adenine 2.guanine

B. Pyrimidines (Single-ring structure)1. Cytosine 2. thymine

Nitrogeneous base pairingAdenine-thymine A-TGuanine-cytosine G-C

2. RNA (Ribonuceic acid)Nitrogeneous base pairing Adenine – uracil A-UGuanine – cytosine G-C

Cen

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Nucleic acid

Lipid

Protein

Nucleic acid

Nucleic acid

Nucleic acid+ protein

Nucleic acid

DNA and RNA

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DNA and RNA

Note that T pairs with A (T:A) and C pairs with G (G:C)