03- biological molecules

• carbohydrates: organic molecules made up of the elements carbon, hydrogen, and oxygen.

  • hydrogen and oxygen atoms are present in the ratio 2:1
• carbohydrates

  • monosaccharides (simple sugar)
  • glucose, fructose, galactose, ribose
  • disaccharides (double sugar)
  • maltose, sucrose, lactose
  • polysaccharides (complex carbohydrates)
  • starch, glycogen, cellulose
  • monosaccharides & disaccharides are readily soluble in water, exerts osmotic pressure
  • polysaccharides are insoluble in water
• Monosaccharides

  • basic unit of carbohydrates
  • can pass through cell membranes and be absorbed in cells
  • e.g glucose and fructose have the same chemical components arranged differently, different chemical and biological properties
  • glucose: plants and animals
  • fructose: common in plants, rare in animals
• Disaccharides

  • condensation reaction
  • e.g maltose and sucrose
  • glucose + glucose = maltose
  • glucose + fructose = sucrose
  • galactose + glucose = lactose
  • can be split into 2 monosaccharides by hydrolysis
• polysaccharides

  • many molecules of monosaccharides joined together to form a large molecule through condensation reaction
  • e.g starch, cellulose and glycogen (all glucose)
  • starch
  • storage form of carbohydrates, can be digested to glucose to provide energy
  • found in storage organs of plants
  • cellulose
  • cellulose cell wall protects plant cells form bursting or damage
  • cannot be digested in our intestines
  • glycogen
  • branched molecule
  • storage form of carbohydrates in mammals (main store of glucose)
  • stored in liver and muscles of mammals
• condensation reaction: 2 monosaccharides joined together to form a larger molecule with the removal of 1 molecule of water (formation of glycosidic bond in carbs)
• hydrolysis: splitting up a disaccharide into its monosaccharide units by adding 1 molecule of water to break the bond
• plants store glucose in the form of starch

  starch is consumed and digested forming glucose and stored as glycogen in animals

  glycogen and starch are:

  • insoluble in water, do not change the water potential in cells
  • large molecules that cannot diffuse through cell membranes, will not be lost from the cell
  • can easily be broken down to glucose when needed
  • molecules have compact shape, occupy less space than all individual glucose molecules
• breakdown of starch

  • bonds within the polysaccharide are broken
  • enzyme amylase digests starch to form the sugar maltose, which is then hydrolysed to glucose by maltase
• functions of carbohydrates:

  • substrate for respiration, provide energy for cell activities
  • form supporting structures
  • converted to other organic compounds (amino acids and fats)
  • formation of nucleic acids (DNA)
  • synthesise lubricants
  • synthesise nectar in flowers
• Fats (lipid)

  • organic molecules made up of the elements carbon hydrogen and oxygen
  • can be broken down into fatty acids and glycerol
• triglycerides

  • major group of lipids
  • fats - solid at room temp
  • oils - liquid at room temp
  • made up of fatty acids and glycerol
  • 1 glycerol & 3 acid molecules
  • macromolecules
• fatty acids

  • organic molecule
  • has a carboxyl group (OH-C=O)
  • may be saturated or unsaturated
  • saturated - single covalent bond
  • unsaturated - at least 1 double bond, bend in structure known as kink

  bonding of fatty acids and glycerol

  • hydroxyl group (O-H)
  • ester linkage (O-C=O)
• proteins

  • organic molecules made up of he elements carbon, hydrogen, oxygen and nitrogen (sulfur may be present)
  • always present in all cells
• amino acids

  • building blocks of protein
  • amino group, acidic group, and side chain (R)
  • long chains of amino acids fold to give proteins a 3 dimensional shape
  • polypeptide: many amino acids joined in a linear manner through condensation
  • peptide bonds/ linkages are formed between amino acids in a polypeptide chain
  • protein molecules made up of 1 or more chains folded together in a 3D shape

  
• function of proteins

  • synthesis of new cytoplasm for growth and repair of worn-out body cells
  • synthesis of enzymes and some hormones
  • formation of antibodies to combat diseases
• functions of fats

  • source and long-term storage of energy
  • have higher energy value compared to carbs
  • insulating material that prevents excessive heat loss (e.g blubber)
  • solvent for fat-soluble vitamins & vital substances such as hormones
  • essential part of cells (cell membranes)
  • way to reduce water loss from the skin surface
  • oily substance reduce rate of evaporation of water & rate of heat loss from the skin
• TEST FOR

  proteins: buriets test

  • add buriets solution and let it rest for 5 minutes
  • turns violet if proteins are present

  reducing sugars: Benedicts test

  • add Benedicts solution, shake, and place in boiling water for 3 minutes
  • green: traces
  • yellow/ orange: moderate
  • red: large

  starch: iodine test

  • add iodine solution
  • turns blue-black if there is starch

  lipids: ethanol emulsion test

  • add equal amounts of ethanol and water to the liquid
  • shake well
  • white emulsion formed at the presence of lipids