Life Science

• Monosaccharides


  • Simple sugars, such as glucose, are the basic units of carbohydrates
  • We test for glucose with Benedict’s solution or Fehling’s A and Fehling’s B solutions
• Elements found in all compounds


  • Carbon, Hydrogen, Oxygen, Nitrogen, Phosphate
• Saturated and Unsaturated Fats

  • Unsaturated fatty acids are mainly found in plants and are liquid at room temperature
  • Saturated fatty acids are found in fats from animals and are solid at room temperature
  • Generally, unsaturated fats are healthier for humans to consume than saturated fats
• Carbohydrates


  • Are made up of atoms of carbon, hydrogen, and oxygen
  • Their main function is to provide energy in living organisms
• Disaccharides


  Two 'single sugars' can join together to form 'double sugars like sucrose
• Classes of Carbohydrates

  1. Some carbohydrates are small, energy simple molecules like glucose

  2. Others, such as starch and cellulose, are large complex molecules
• Atoms and Molecules

  • Everything around us consists of many different chemical substances made of tiny particles called atoms
  • When two or more atoms combine, they form a molecule
• Over 90% of all known compounds are organic
• Organic and Inorganic Compounds


  All known molecules and compounds can be classified as either inorganic or organic, depending on which elements make up the compound
• Proteins

  • Proteins consist of atoms of carbon, hydrogen, oxygen, and nitrogen
  • Some may contain atoms of sulphur, phosphorous, and iron
  • Proteins are important in cell structure and functions, making up more than 50% of the dry mass of most cells
  • Functions include carrying oxygen, forming antibodies, forming hormones, and regulating body functions
  • Proteins are very sensitive to temperature and pH levels
• Structure of Lipids

  • Lipid molecules are made of three fatty acids joined to a smaller molecule called glycerol
  • When broken down, they release a lot of energy
• Lipids


  Lipids are fats and oils that store energy in the bodies of living things and make up some structures in cells like cell membranes
• Polysaccharides


  Large carbohydrate molecules like starch, glycogen, and cellulose
• Organic Compounds

  Carbohydrates, proteins, lipids, nucleic and enzymes are all organic compounds that have different functions in living organisms
• pH


  • Measure of how acidic/alkaline a substance is on a scale of 1-14
  • Every enzyme has an optimum pH at which it functions best
• Nucleic acids

  • Nitrogenous compounds found in all cells
  • Play an important role in controlling cell structures and functions
  • Contain carbon, hydrogen, oxygen, nitrogen, and phosphorus
  • Made up of nucleotides
  • Two types: RNA and DNA
• Enzymes

  • Regulate and make possible every chemical reaction in cells
  • Join molecules together to make bigger molecules and break down large molecules into smaller ones
  • Function best within a certain temperature range
  • Have an active site with a specific shape
  • Sensitive to temperature and pH
• Temperature increase

  Reaction rate increases
• Temperature increase beyond a certain point

  Shape of the active site changes, enzyme is denatured
• Enzyme action

  1. Enzyme and substrate fit together like a key fits a lock

  2. Chemical reaction takes place when enzyme and substrate are joined

  3. Product is released from the enzyme after the reaction

  4. Enzyme can be used again on a new substrate
• Substances by pH


  • pH 7 is neutral (e.g., water)
  • pH below 7 is acidic (e.g., vinegar)
  • pH above 7 is alkaline (e.g., soap)
• Proteins


  • Very large molecules that form chains made up of smaller units called amino acids
  • Functions include carrying oxygen, forming antibodies, forming hormones
  • Act as catalysts
• Uses of enzymes


  • Washing powders, baby food, brewing industry, rubber industry, dairy industry, fruit juice manufacture, baking
• Amino acids

  • There are 20 amino acids used to make proteins
• Vitamins


  • Complex organic compounds found in small quantities in natural foods
  • Needed for body health and normal metabolic processes
  • Named alphabetically in order of discovery starting with vitamin A
  • Plants do not require vitamins
• Water

  • Most important inorganic molecule for living organisms
  • Chemical formula is H2O
  • Consists of two hydrogen atoms and one oxygen atom
• Eutrophication is the process when: High levels of nutrients stimulate the growth of aquatic plants and algae, which can clog the water bodies. The plants and algae use up dissolved oxygen in the water as they decompose and block light from reaching deeper water
• Plants obtain their minerals from the soil
• Water makes up a large proportion of the mass of cells and is required for many metabolic processes in plants and animals
• The main nutrients in fertilizers are nitrogen, in the form of nitrates and phosphorus, as well as potassium, magnesium, calcium and other minerals
• Micro-elements are minerals that are needed in relatively small quantities by plants and animals
• Each molecule of water consists of two atoms of hydrogen and one atom of oxygen
• Why minerals are needed

  • Development of strong teeth and bones
  • Bone growth; helps release energy in the body
  • Development of bones and teeth; helps release energy in the body
  • Needed for transport of oxygen in the body
  • Regulates the rate at which body processes take place, in other words, metabolism
• In 1838, after studying many plant tissues, Matthias Schleiden claimed that all plants are made of cells
• Minerals are needed in key chemical reactions in important life processes
• Inorganic Compounds

  • Waters
  • Minerals
• Minerals are simple chemical substances such as calcium
• Results of mineral deficiency


  • Stunted growth, rickets
  • Muscle weakness and cramps
  • Very rare, as most foods contain some phosphorus
  • Tiredness, weakness, headaches, iron-deficiency anaemia
  • Goitre, which is a growth on the neck in adults
• Plants require inorganic nutrients for normal healthy growth
• Overuse of artificial inorganic fertilizers breaks down the soil structure as organic matter is not replaced in the soil through decomposition