Biological Molecules-Topic One

• What are biological molecules?

  A particular group of chemicals that are found in living organisms.
• What is covalent bonding?


  Atoms share a pair of electrons in their outer shells. The outer shell of BOTH atoms are FILLED, and a more stable compound, a molecule, is formed.
• What is ionic bonding?

  Ions with OPPOSITE charges attract each other. This electrostatic attraction is known as an IONIC BOND. Weaker than covalent bonds.
• What is hydrogen bonding?


  The electrons within a molecule aren't evenly distributed but tend to spend more time at one position. This region is more negatively charged than the rest of the molecule.
• What is a polarised molecule?


  A molecule with an uneven distribution of charge, a polar molecule. The negative charged region of one polarised molecule attract each other. A weak electrostatic bond is formed.
• What is the formation of polymers?


  Monomers can be linked together to form long chains>monomer sub-units called POLYMERS, through the process of POLYMERISATION. Monomers usually based on carbon.
• How are polynucleotides formed?

  Through the process of polymerization, where nucleotides are joined together by phosphodiester bonds. Formed by linking mononucleotide sub-units.
• How are polypeptides formed?


  Through the process of protein synthesis, where amino acids are joined together by peptide bonds.
• What is a condensation reaction?


  A reaction which joins monomers by chemical bonds and it involves the elimination of a water molecule.
• What is a hydrolysis reaction?

  A chemical reaction that breaks down a compound by adding water.
• What is metabolism?


  Metabolism is the process by which the body converts food and drink into energy.
• What is a mole?


  SI unit for measuring the amount of a substance and is abbreviated to mol.
• What is a molar solution?


  A solution with a concentration of 1 mole of solute per liter of solution.
• Carbon atoms


  Very readily form bonds with other carbon atoms allowing a sequence of carbon atoms of various lengths to be built up. These form a 'backbone' along which other atoms can be attached, permitting a large number of different types and sizes of molecule, all based on carbon.
• What is a carbohydrate?


  A macronutrient that provides energy to the body. Carbon molecules-carbo & water-hydrate.
• Monomers and examples of monomers

  E.G- monosaccharides, amino acids, nucleotides. They can join together to form long chains called POLYMERS. Biological molecules are often polymers.
• What is the basic monomer unit in carbohydrate?

  Sugar, also known as a saccharide A single monomer is called a monosaccharide.
• What can a pair of monosaccharides make?

  A disaccharide. Can also be combined in large numbers to make polysaccharides.
• What are monosaccharides?


  Sweet-tasting, soluble substances that have the general formula of (CH2O)n' where 'n' can be any number between 3 and 7.
• Examples of monosaccharides?


  Glucose, galactose and fructose. Glucose is a hexose sugar with 6-carbon atoms, general formula of C6H12O6.
• Examples of disaccharides?


  Glucose + Glucose= MALTOSE Glucose + Fructose = SUCROSE Glucose + Galactose = LACTOSE
• What reaction occurs when monosaccharide join?

  A condensation reaction. Bond formed is a GLYCOSIDIC BOND.
• What reaction occurs when water is added to a disaccharide?

  A hydrolysis reaction. Water is added to a disaccharide under suitable conditions, breaking the glycosidic bond releasing the constituent monosaccharides.
• What is starch?


  Starch is a complex carbohydrate made up of glucose molecules and is the primary storage form of energy in plants. Forms an important component of food and is the major energy source in most diets.
• What is starch made up of?


  Chains of a-glucose monosaccharides linked by glycosidic bonds formed by a condensation reaction. Chains can be branched or unbranched (unbranched is wound into a tight coil that makes the molecule very compact)
• What is the structure of starch suited for?

  Insoluble- does not affect water potential so water is not drawn into cells by osmosis/ doesn't diffuse out of cells/ stored in a small space as it is compact/ a-glucose is easily transported & readily used in respiration/ branched form has many ends which can be acted on by enzymes simultaneously so glucose monomers are released rapidly.
• What is glycogen?


  Glycogen is a polysaccharide that serves as a storage form of glucose in animals.
• Where is glycogen found?

  (Liver and muscles). Animals and bacteria.
• What is the structure of glycogen?


  Glycogen is a branched polymer of glucose molecules linked together by alpha-1,4-glycosidic bonds with alpha-1,6-glycosidic bonds at the branch points.
• Why does glycogens' structure suit it up for storage.

  Highly branched structure- end can be acted on simultaneously by enzymes, rapidly broken down to form glucose monomers that are used in respiration. It's insoluble so does not draw water in the cells by osmosis- does not diffuse out of cells/ compact so can be stored in a small space.
• What is cellulose?


  Cellulose is a complex carbohydrate that is the main structural component of plant cell walls. Made of b-glucose monomers.
• What is the structure of cellulose?

  Cellulose is a linear polymer composed of glucose units linked together by beta-1,4-glycosidic bonds. Straight, unbranched chains that run parallel to one another, allowing hydrogen bonds to form cross-linkages between adjacent chains.
• Structure of Cellulose

  Molecules are grouped together to form microfibrils which are arranged in parallel groups called FIBRES. Cellulose is a major component of plant cell walls and provides rigidity. The wall also prevents the cell from bursting as water enters the cell by osmosis<it does this by exerting an inward pressure stopping any further influx of water<living plant cells are turgid & push against each other, making non-woody parts of the plant semi-rigid<important in maintaining stems and leaves in a turgid state so they can provide the MAX surface arear for photosynthesis.
• What are lipids?

  Varied group of substances that share characteristics:

  -contain hydrogen, carbon and oxygen

  -proportion of oxygen to carbon & hydrogen is smaller than in carbs

  -insoluble in water

  -soluble in organic solvents like alcohols & acetone
• What is the main group of lipids?

  Triglycerides (which are fats and oils) and phospholipids
• What are triglycerides?


  Fats in the blood. They have three (tri) fatty acids combined with glycerol (glyceride). Each of the three fatty acids forms an ESTER bond with glycerol in a condensation reaction. Hydrolysis of a triglyceride therefore produces glycerol and three fatty acids.
• What are triglycerides?


  Over 70 different fatty acids and all have a carboxyl group (-COOH) with a hydrocarbon chain attached. If this chain has no carbon-carbon double bonds, the fatty acid is SATURATED, as all carbon atoms are linked to max number of hydro atoms, (saturated with hydro atoms. If there's a single double bond, it's MONO-SATURATED, or if more than one double bond is present, it's POLYUNSATURATED.
• How is the structure of triglycerides related to its properties?

  ~High ratio of energy-storing-carbon-hydrogen bonds to carbon atoms; great source of energy

  ~low mass to energy ratio; good storage molecules as a lot of energy can be stored in a small volume. Beneficial to animals as reduces mass they carry

  ~large and non-polar, insoluble in water. Storage does not affect osmosis in cells the water potential

  ~high ratio of hydrogen to oxygen atoms, they release water when oxidised & provide an important source of water
• What are phospholipids?


  Phospholipids are a type of lipid molecule that make up the basic structure of cell membranes. Similar to lipids but one fatty acid is replaced by a phosphate molecule, they attract water.
• What is a hydrophobic tail in phospholipids?

  Interacts (attracted) with water not with fat