chemical basis of life

Water•found in largest quantities (50-90%)•normal body temperature- 37oC or 98oF•(<body temperature or hypothermia- metabolic functions bec slower and finally stop)•(>body temperature or hyperthermia- proceed too rapidly and body proteins break down)•death at either extreme

Inorganic Compounds

Uses of Water1.vehicle for chemical reactions2.regulation of body temperature3.excretion of waste4.acts as solvent5.transport of food, nutrients and essential gases6.protection7.serves as base for body lubricants

• Water is a polar molecule

THE PROPERTIES OF WATER

Which leads to hydrogen bonding

Hydrogen bonds make liquid water cohesive– Due to hydrogen bonding, water

molecules can move from a plant’s roots to its leaves

– Insects can walk due to surface tension created by cohesive water molecules

Like no other common substance, water exists in nature in all three physical states:

– as a solid

– as a liquid

– as a gas

Water is a universal solvent. -It is able to dissolve a large number of different chemical compounds.

Ions- 5% of body weight; dissolved in water•Important ions: K, Mg, PO4, SO4, bicarbonates, Na, Cl•most plentiful salts- Calcium Phosphates (in bones, teeth)

Inorganic Compounds

Uses of Inorganic Materials1.provide inorganic chemicals for cellular reactions2.necessary for operation of some cellular activities3.maintenance of proper osmotic condition4.acid-base balance5.formation of bones6.formation of thyroxine7.transport of CO2 and O2

Organic Compoundscarbon-containing ; exceptions: CO2, CO and

carbidesCarbohydratesLipidsProteins

Carbohydrates – C,H,O; C is in the same ratio as H2O= (Cn (H2O)n)

•oxidize easily and are the most readily-available energy/heat source•serve as important structural material in some animals and all plants•literally means ‘hydrated carbon’•made up of repeating units called sugars.•Excess CHO-- glycogen or fat (stored in liver or muscles)

Note : The larger the carbohydrate molecule, the

less soluble it is in water.

Organic Compounds

Classification of Sugars according to size and solubility

1.Monosaccharides- simple sugars; single ring structures with 3-7 carbon atoms•CHO in a ratio of 1:2:1•Basic units of carbohydrates•Examples:Glucose, Fructose, galactose- C6H12O6 (hexoses)Deoxyribose, ribose – pentose ( 5C)

2. Disaccharides- double sugars; made up of two monosaccharides joined together by dehydration synthesis

•Have to be hydrolyzed to be broken down to monosaccharides

•Examples: glucose + fructose = sucrose (table sugar)

2C6H12O6 ---- C12H22O11 + H2O

lactose( milk sugar)= gluc + galmaltose(malt sugar)= gluc + gluc


1.Polysaccharides- long chains of simple sugars (polymers) linked together by dehydration synthesis•individual units called monomers•large, insoluble molecules•lack sweetness of mono- and disaccharides

Examples:Starch- storage form of

CHO in plants (made up of long glucose chains)


Hydrolysis: Amylase maltaseStarch - ------- maltose -------2 glucose

Glycogen- storage CHO of animal tissues - large molecule and highly branched - can easily be broken down to yield glucose

Cellulose – most abundant organic molecule in the planet

- chief structural material in plants; provides rigidity

- indigestible in man due to complex arrangement of glucose

- provides bulk and stimulates bowel movement - enzyme cellulase from bacteria and

protozoans digest cellulose to yield glucose

Chitin•Second most abundant organic compound on earth.•Makes up the hard outer skeletons of certain animals

ex. Insects, crabs, lobsters•Resistant to breakdown by bacteria and animals

Lipids insoluble in water but dissolve readily in organic solvents as alcohol, chloroform and ether

-CHO, but with less O and more C atoms-- more heat

Three forms of Lipids1.Neutral fats- or triglycerides; Fatty acids and glycerol as building blocks (3:1 ratio) - most common;

for heat loss and protection - non-polar and do

not mix with water •may be solid (fats) or liquid (oils) according to length of fatty acid chains and degree of saturation:

•Saturated- with single bonds between C atoms-longer fatty acid chains; solid at 20oC- animal fats as butter fat and meat fats- encourage build-up of plaques in walls and vessels

•Unsaturated- with double/triple bonds between C atoms- short FA chains; liquid at room temperature- plant sources as olive, peanut, corn-margarine as substitute for butter

** fat deposits in subcutaneous tissue – thicker layer in women

1.Phospholipids-modified triglycerides with two FA chains + 1 phosphorus-containing group

- with polar heads and non-polar (hydrocarbon)

tails- phosphate groups in

heads attract water and ions

- in cell membrane; regulates transport

1.Steroids – lipids made up of solid alcohol with no fat-like properties

- fat-soluble and contain little O

Cholesterol - from animal products; CV

disorders - component of cell membranes - raw material for Vitamin D

synthesis, other steroid hormones ( estrogen, progesterone,testosterone,

cortisol and aldosterone)- manufactured in liver, most

abundant in brain- attaches to protein to form

lipoprotein before it can circulate

Two types of Lipoproteins

High Density Lipoproteins (HDL)- more CHON, less lipid- brings cholesterol to liver for elimination-‘good cholesterol

Low Density Lipoproteins (LDL)- less CHON, more lipid-clogs blood vessels- ‘bad cholesterol’

•CHON, sometimes sulfur, phosphorus and trace metals as iron and copper; second most abundant (10-20% of cell mass)•Building blocks: amino acids-- about 20 aa

•Essential aa ( 8)- taken in with food•Non-essential (12)- synthesized by body

•aa can be a base (proton acceptor) or an acid (proton donor)•linked by peptide bonds which break during hydrolysis•Deficiency: brittle nails, rough scaly skin, rough lackluster hair•Extreme deficiency: kwashiorkor

Proteins

Functions of Proteinsi.constitute framework of cytoplasmii.releases energy when oxidizediii.source of enzymes and hormonesiv.repair of damaged/worn-out tissues

Fibrous Protein•with extended strand-like appearance•linear, insoluble in water and very stable•provides support and tensile strength to body tissues•‘structural proteins’; most exhibit 2o structure, others 4o

•Examples: leather, hair, nuclear membrane, ER, mitochondrion

Two types of Proteins

Globular Protein•compact, spherical, exhibit 3o to 4o structures•water soluble, mobile, chemically active•‘functional proteins’•dissolved in cellular fluids•Examples: antibody molecules, enzymes, plasma prteins

Two types of Proteins

•DNA –chief hereditary material•RNA- important in protein synthesis•nucleotides as structural units•nucleotide- nitrogen base, pentose sugar, phosphate group

Nucleic Acids

chemical basis of life

Food

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