Proteins and Amino Acids in Human Body

Classification of Organisms

• Flowering plants: grass, maize, barley, orchid, lily
• Non-flowering plants: mosses, fern
• Vertebrates: fish, birds, amphibians, reptiles, mammals
• Invertebrates: insects, jellyfish
• Fungi: Mucor (bread mould), yeast (made of single cells, lives everywhere), Chlorella (has chloroplasts, can carry out photosynthesis)

Characteristics of Organisms

• Fungi: organized into a mycelium made from thread-like structure called hyphae, which contain many nuclei
• Viruses: parasitic, can reproduce only inside living cells, infect every type of living organism, have a wide variety of shapes and sizes, have no cellular structure, composed of a core of genetic material surrounded by a protein coat, genetic material can be either DNA or RNA

Carbohydrates

• Chemical elements: carbon, hydrogen, oxygen
• Ratio of H:O = 2:1
• Monosaccharides: simplest form of carbohydrates, examples: glucose, fructose, galactose, sweet, soluble in water, readily absorbed in the alimentary canal, can be used to produce energy in cell respiration
• Disaccharides: formed by 2 monosaccharides joining together by condensation, with the removal of a water molecule, examples: maltose, lactose, sucrose, sweet, soluble in water, can be broken down into 2 simple sugars by specific digestive enzymes or heating with dilute acid in the laboratory
• Polysaccharides: formed by a large amount of monosaccharides joining together by condensation, macromolecules, not sweet, insoluble in water, no reducing power, examples: starch (storage form of glucose in plants), glycogen (storage form of glucose in animals), cellulose (cell wall)

Lipids

• Chemical elements: carbon, hydrogen, oxygen
• Ratio of H:O > 2:1
• Composed of a glycerol molecule and three fatty acid molecules
• Insoluble in water, soluble in organic solvents
• Animal fats: solid/semi-solid at room temperature
• Plant oil: liquid at room temperature
• Major functions: source of energy, energy reserve, heat insulation, shock absorber, cell membrane component, hormone component

Proteins

• Chemical elements: carbon, hydrogen, oxygen, nitrogen, sometimes sulphur
• Basic unit: amino acid
• Amino acid: possesses an amino group, a carboxyl group, and a side chain
• 20 types of amino acids required to build proteins
• Human body requires essential amino acids from diet
• Functions: building cell membrane and cytoplasm, structural material, forming hormones, forming enzymes, production of haemoglobin, production of antibodies, growth and repair of tissues

Vitamins

• Vitamin A: fat-soluble, found in liver, dairy products, carrots, green vegetables, functions: formation of light-sensitive chemical, vision in dim light, maintaining health of skin and lining of mouth cavity and breathing system, deficiency disease: night-blindness
• Vitamin C: water-soluble, found in apples, citrus, functions: formation of connective tissue, healing of wounds, resistance to infection, deficiency disease: scurvy
• Vitamin D: fat-soluble, found in liver, dairy products, functions: absorption of calcium and phosphate salts, formation of strong bones and teeth, deficiency disease: rickets, osteoporosis

Minerals

• Calcium: found in dairy products, functions: formation of teeth and bones, normal function of nerves, blood clotting, muscle contraction, deficiency disease: rickets, osteoporosis
• Iron: found in red meat, eggs, functions: component of haemoglobin in red blood cells, deficiency disease: anaemia

Food Tests

• Reducing sugar test: Benedict's test, brick red precipitate forms
• Starch test: iodine test, iodine solution changes from brown to blue-black
• Fat/oil test: emulsion test, an emulsion/milky solution formed, grease spot test, a translucent spot is left
• Protein test: biuret test, colour of solution changes from blue to purple
• Vitamin C test: DCPIP test, dark blue to colourless/decolourized

Adaptations

• Breathing and gas exchange: numerous alveoli present in the lungs, pressure inside becomes higher than the atmospheric pressure, air is forced out of the lung

Food and Digestion

• Chemical digestion: site of digestion, site of secretion, digestive juice, enzyme/component of secretion, action, optimum pH
• Mechanical digestion: mouth, chewing of food into smaller pieces, stomach, churning, duodenum, emulsification of fats into oil droplets, small intestine, mix food with digestive juices by peristalsis