Biological molecules

• Describe the structure of a water molecule

  An oxygen atom covalently bonded to 2 hydrogen atoms. It is a non-linear shape.
• Name the bond that can link two water molecules together

  Hydrogen bond
• Explain what a hydrogen bond is, which types of atoms it can join together and where they occur in biology

  A hydrogen bond is a weak interaction that can occur whenever molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen
• Draw two water molecules and draw and label the bond that links them together

  
• Define the term 'Polar'

  Has 2 poles, one slightly positive the other slightly negative
• Explain why water is a polar molecule

  Water is a polar molecule because the oxygen atom is more attractive to electrons than hydrogen so pulls the shared electrons towards it. This causes the O to be slightly negative and the Hs to be positive.
• Define the term "electronegativity" and "dipole"

  Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.A dipole is a molecule in which a concentration of positive electric charge is separated from a concentration of negative charge
• List the roles water plays in life (at least 5)

  Solvent transport medium, habitat, reactant, thermal stability, solvent
• Explain why the polar nature of water allows it to be a useful solvent, transport medium, coolant and habitat

  Solvent: Dissolves polar and charged molecules as charges interact with polar water molecules which cluster around them keeping them apartTransport medium: Liquid over large temp. range as H bonds require lots of energy to break. It dissolves many moleculesCoolant: High specific heat capacity as H bonds require lots of energy to breakHabitat: Maintains a constant temp. due to energy required to break H bonds
• Define the terms "hydrophilic" and "hydrophobic"

  Hydrophilic: The physical property of a molecule that is attracted to waterHydrophobic: The physical property of a molecule that is repelled by water
• Define the terms "cohesion" and "adhesion".

  Cohesion: Water molecules attracted to one anotherAdhesion: Water molecules attracted to other substances
• Describe any other properties (not related to its polar nature) water has that makes it useful for life

  Transparent to light - plants growing under water can get light for photosynthesis and aquatic animals can see underwater
• List examples of how water is used from across the whole diversity of life (prokaryotes and eukaryotes; plants, animals and fungi; unicellular and multicellular organisms).

  Supports - keeping plant cells turgid, the hydrostatic skeletons of earthwormsLubrication - Joints such as elbow called synovial joints have sac of synovial fluid stopping bones rubbing against each otherBouyancy - Whales couldn't be so big etc.Swimming - When something pushes against water there is an equal reactive force propelling forwardReactions - Photosynthesis, hydrolysisHigh surface tension allows organisms to suspend themselves at/on the surface e.g. pond skatersIce floats as less dense so insulates water underneath where organisms can surviveRegulating temperature and reaction conditions etc. - sweating as well as high heat capacity
• Using the "polar nature of water" explain the how water can dome above the level of the glass container it is in, the shape of the meniscus in a glass measuring cylinder and capillary action in a narrow glass tube.

  Dome: Cohesion between water molecules causing surface tension due to hydrogen bondsMeniscus: Adhesion to sides of container draws molecules up.Capillarity: Cohesion between water molecules and adhesion to other molecules explains why water moves up narrow spaces. Important for water in xylem vessels.
• Define the terms "monomer", "polymer", and "macromolecule".

  Monomer: Individual molecules that make up a polymerPolymer: Long-chain molecules composed of linked (bonded) multiple individual molecules (monomers) in a repeating patternMacromolecule: Large complex molecules with large molecular masses
• Define the terms "dimer" and "oligomer"

  Dimer: a molecule consisting of two identical molecules linked togetherOligomer: a polymer whose molecules consist of relatively few repeating units
• Define the terms "condensation reaction" and "hydrolysis reaction"


  Condensation reaction: a reaction between two molecules to form a larger molecule and the release of a water molecule. (opposite to hydrolysis)Hydrolysis reaction: the breakdown of a molecule into two smaller molecules requiring the addition of a water molecule (opposite to condensation)
• Define the terms "metabolism", "catabolic reaction", "anabolic reaction"

  Metabolism: the chemical processes that occur within a living organism in order to maintain lifeCatabolic reaction: reactions of metabolism that break molecules down into smaller units. These reactions release energy.Anabolic reaction: reactions of metabolism that construct molecules from smaller units. These reactions require energy from the hydrolysis of ATP.
• List the 4 main categories of biological molecule.

  Carbohydrates, Lipids, Proteins, Nucleic acids
• Summarise the name of the building blocks, the name of the dimer, the name of the macromolecule, whether or not the macromolecule is a polymer, the name of the bond that links the building blocks together, the name of the reaction that joins the building blocks together, the name of the reaction that breaks the macromolecule apart, examples of the functions of the molecules and the elements that make up the molecules for carbohydrates, lipids, proteins and nucleic acids. Include examples of names of specific molecules where appropriate


  Carbohydrates: monosaccharides, disaccharides, polysaccharides, they are polymers, glycosidic bond, condensation reaction, hydrolysis, respiration-cell wall-cell signalling etc.Lipids: fatty acids and glycerol, (monoglyceride, diglyceride) and triglyceride, not a polymer, ester bond, condensation, hydrolysis, source of energy-membrane structure-hormones etc.Proteins: amino acids, dipeptide, polypeptide, they are polymers, peptide bond, condensation, hydrolysis, transport molecules-enzymes-antibodies etc.Nucleic acids: nucleotides, dinucleotide, polynucleotide, they are polymers, phosphodiester bond, condensation, hydrolysis, genetic material-protein synthesis etc.
• Define the terms "single bond" and "double bond"

  single bond: a chemical bond in which one pair of electrons is shared between two atomsdouble bond: a chemical bond in which two pairs of electrons are shared between two atoms
• State the elements present in carbohydrates

  Carbon, Hydrogen and Oxygen
• State the general formula of carbohydrates

  (CH2O)n
• Define the term "monosaccharide", "disaccharide" and "polysaccharide"

  Monosaccharide: A single sugar moleculeDisaccharide: A molecule comprised of two monosaccharides joined by a glycosidic bondPolysaccharide: A polymer made of many sugar (monosaccharides) monomers
• Define the term "pentose sugar" and "hexose sugar"

  Pentose - a monosaccharide composed of 5 carbonsHexose - a monosaccharide composed of 6 carbons
• Define the term "triose sugar" and name an example

  Triose - monosaccharide composed of 3 carbons E.g. glyceraldehyde
• Describe what is meant by a "furanose ring" and a "pyranose ring"

  Furanose ring - 5 membered ring e.g. fructosePyranose ring - 6 membered ring e.g. glucose
• Draw a molecule of alpha-glucose

  
• Draw a molecule of beta-glucose

  
• Draw a molecule of ribose

  
• Define the term "isomer"

  Molecules with the same molecular formulae but different structural formulae (same atoms but arranged differently)
• Describe the difference between alpha- and beta-glucose

  The hydrogen and hydroxyl groups on carbon 1 are reversed.
• Describe the differences between alpha glucose and ribose

  Glucose is pyranose but ribose is furanoseGlucose used in starch and glycogenRibose used in RNA
• List 3 examples of disaccharides and for each state which monosaccharides they are composed of

  Sucrose - alpha-glucose and fructoseMaltose - two alpha-glucoseLactose - alpha-glucose and galactose
• State the properties and functions of glucose, fructose, galactose, maltose, sucrose and lactose. For each also state where they occur.

  Glucose - monosaccharide used in respiration and to make polymers such as starchFructose - hexose sugar commonly found in fruitGalactose - another hexose sugarMaltose - found in barleySucrose - found in sugar cane and beetLactose - found in milk
• Draw a labelled diagram demonstrating how two molecules of glucose form a disaccharide in a condensation reaction, showing the location of a 1,4-glycosidic bond and from where a water molecule is generated

  Condensation reaction involves hydroxyl groups on carbons 1 and 4. Water is lost and the bond is formed by the remaining oxygen atom.

  
• Describe, using a diagram, how hydrolysis of maltose occurs and why water is needed

  Glycosidic bond is broken by the addition of water. Catalysed by enzymes at 35-40°C or by being boiled with an acid for acid hydrolysis

  
• Explain why alpha-glucose links together to form starch whereas beta-glucose links together to form cellulose

  Due to the arrangement of the hydrogen and hydroxyl groups on carbon-1...The 1-4 glycosidic bonds using alpha mean all the monomers are the same way up, but with beta each is rotated 180° from the last.
• List the two different polysaccharides that make up starch.

  Amylose (1-4 bonds only) and Amylopectin (mainly 1-4 but some 1-6)
• Explain with the use of diagrams why glycosidic bonds are called 1,4 or 1,6


  Whether they are between the OH groups on carbons 1 and 4 or 1 and 6.