only single bonds between the carbon atoms are known as saturated. ⢠because it is saturated with hydrogens, e.g. stea
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 oxygen.
Fats & Oils • are formed from one molecule of glycerol (a three carbon molecule) and three molecules of fatty acids (long chain of carbon and hydrogen
with carboxylic group at one end).
• only single bonds between the carbon atoms are known as saturated • because it is saturated with hydrogens, e.g. stearic acid. • are one or more double bonds between carbons, • fewer hydrogens the fatty acid is unsaturated, • e.g. oleic acid.
Saturated Fat (e.g.) Bacon
Unsaturated Fat ( e.g. Corn )
• a high concentration of energy, about 9300 calories per gram, • (sugars and proteins about 4100 calories per
gram), • are used for semipermanent energy storage.
Waxes • are similar to fats and oils • except that the fatty acids are linked to long chained alcohols instead of glycerol. • from a waterproof coating over the leaves and
stems of plants.
Phospholipids • are similar to fats and oils • except that one of the fatty acids is replaced by a phosphate group.
Structure of Phospholipids
Phospholipid
Phospholipids
• Each phospholipid has a head (containing a phosphate group) and • a tail (made up of two fatty acids).
Phospholipids
The head is water soluble (hydrophillic), but the tail is not.
Phospholipids
When phospholipids molecules are surrounded by water, they can form double layers (bilayers) with their head oriented towards the water molecules and their tails oriented away from water, toward the inside of the “lipid sandwich”. The membranes surrounding living cells contain a double layer of phospholipids.
When phospholipids molecules are surrounded by water
• "tails” are insoluble in water, • "heads" are water – soluble. • have two contradictory ends: • heads that are hydrophilic and • tails that are hydrophobic. • is crucial to the structure of the cell membrance.
