Plant Physiology - the study of how plants function - growth - plant behavior ( temperature, pressure, light) - complex synthetic process ( photosynthesis, respiration)
Biological Molecules consist of a carbon backbone attached to functional groups determine the characteristics, solubility chemical reactivity of the molecules.
Synthesizing Organic Molecules • Small molecules (e.g. amino acid ) are synthesize larger molecules (e.g. Protein). Amino acid add Amino acid Small molecule subunit /monomers
Protein larger molecules polymers
a. A typical organic molecule is composed of similar or identical subunits linked together. (e.g. starch)
A condensation reaction & Hydrolysis reaction
• Living organisms synthesize long organic molecules through condensation reactions, • a hydrogen removed from one subunit and a hydroxyl removed from a second subunit "condense" to form a molecule of water
• as the subunits are joined by a covalent bond • The reverse reaction, called hydrolysis, • uses water to break the molecule into individual subunits again.
The Principal Types of Biological Molecules all biological molecules fall into one of four categories : • carbohydrates • lipids • proteins • nucleic acids.
Carbohydrates All carbohydrates are small water – soluble sugars (glucose, fructose) or chains made by stringing sugar subunits together (starch, cellulose, glycogen).
General Formula ---- ( CH2O)n Three Principle Kinds Monosaccharides Disaccharides Polysaccharides
•The general formula for carbohydrates is Cn(H2O)n.
Monosaccharides • consisting of one sugar molecule is a monosaccharide. • monosaccharide is glucose. • six carbons, • the chemical formula (CH2O)6 or C6H12O6. a key role • in short term energy storage • nearly all the chemical reactions that produce energy for living organisms
monosaccharides six carbon atoms are • Fructose • galactose • mannose. five carbon atoms • Ribose • deoxyribose • xylose • arabinose.
- The open chain structure applies to solutions - Starch, and glycogen, sugars occur in a ring or cyclic structure. -The ring may be six – membered ( pyranose) as in glucose - five membered ( furanose ) as in fructose
Diasccharides • Two monosaccharides linked together form a disaccharide, • e.g. sucrose(table sugar : glucose plus fructose), • Lactose ( milk sugar : glucose plus galactose ), • Maltose ( glucose plus glucose )
Polysaccharides • Polysaccharides are molecules containing numerous monosaccharides usually glucose. e.g.
starch (in plants ) ,
glycogen (in animals) and
cellulose (in plant cell walls).
Starch • Starch is made up of long chains of glucose residues linked by oxygen bridges • between carbon atom number 1 of one residue to carbon atom number 4 of the next.
Chemical structure of starch
Chemical structure of starch • made up of two components, amylose and amylopectin. • Amylose is more soluble in water than amylopectin,
• may be separated from amylopectin by allowing starch grains to stand in water for prolonged periods. • Amylose then dissolves, while the less soluble
amylopectin remains behind
• Amylose dissolves, • while the less soluble amylopectin remains behind. • This difference in behaviour is due to a difference in chain structure. • In amylose the chains are unbranched. • In amylopectin the chains are branched
amylose & amilopectin
• Many short branches, containing about eighteen glucose residues, are linked with other chains of roughly eight glucose residues, forming a highly ramified structure.
Lipids • are insoluble in water. • are classified into three groups : • oils, fats and waxes, • which are similar in structure
• contain carbon, hydrogen and oxy