Molecular bonding Flashcards
Describe covalent bonds
-atoms consist of a nucleus surrounded by shells of electrons
-most atoms tend to be stable when outermost shell has 8 electrons
-atoms of different elements have different numbers of electrons in their outermost shell
-by sharing electrons with other atoms the atoms outermost shell can be filled and becomes strongly bonded with other atom - this is a covalent bond
Condensation and hydrolysis reactions
-condensation reaction occurs when two molecules are joined together with removal of water
-in same way, two molecules can be split apart with addition of water - hydrolysis
Describe monomers and polymers
-condensation and hydrolysis reactions are responsible for linking and splitting apart biological molecules
-the units which are joined together they form a dimer
-when lots monomers join together they form a polymer
List the monomer and polymer of carbohydrates, proteins and nucleic acids
CARBOHYDRATES
monomer= monosaccharides (e.g. glucose)
polymer=polysaccharide (e.g. starch)
PROTEINS
monomer=amino acids
polymer=polypeptides and proteins
NUCLEIC ACIDS
monomer=nucleotides
polymer= DNA and RNA
Describe hydrogen bonds
-a hydrogen bond is weak interaction which happens wherever molecules contain slightly negative charged atom bonded to slightly positively charged hydrogen atom
-the bond is weaker than a covalent bond
-in some polymers, thousands and thousands of hydrogen bonds form between chains of monomers
-having many bonds like this help stabilise the structure of some biological molecules
WATER PROPERTIES: transparent liquid
-0-100 degrees celcius
1) Habitat - aquatic animals can move/swim
2) photosynthesis can occur - plants can live at depth
3) cytoplasm - reactions occur in solution
4) transport - blood, in xylem
WATER PROPERTIES: solvent due to polar molecule
1) solutes can dissolve - reactions can occur in cytoplasm of cells
2) molecules and ions can be transport - e.g. in blood
3) plants/fish can absorb minerals from water
WATER PROPERTIES: ice less dense than water
-ice less dense than water therefore ice floats on water
-below 4 degrees
-H bonds form lattice
-deeper water insulated
-prevents ponds from completely freezing
WATER PROPERTIES: cohesion and surface tension
-cohesion - water column in xylem
-surface tension - insect walk on water
-adhesion - capillary action in xylem
WATER PROPERTIES: high specific heat capacity
-energy required to raise 1kg by 1 degree=4.2kJ
-takes a lot of energy to heat water up
-therefore thermally stable aquatic environment for aquatic organisms
-stable environment in cells - enzymes work efficiently
WATER PROPERTIES: high latent heat of vaporisation
-energy required to break H bonds and cause evaporation
-evaporation from skin takes a lot of heat energy - effective cooling, sweating and panting
WATER PROPERTIES: reactant
-water is part of metabolic reactions e.g. hydrolysis
Carbohydrate function
-carbohydrates contain carbon, hydrogen and oxygen
-hydrated carbon - for ever carbon there are 2 hydrogens and 1 oxygen atom
-functions: act as source of energy (e.g. glucose), store of energy (e.g. starch) and structural units (e.g. cellulose in plants and chitin in insects)
-some carbohydrates are also part of other molecules such as nucleic acids and glycolipids
-three main groups of carbohydrates: monosaccharides, disaccharides and polysaccharides
Describe monosaccharides
-monosaccharides are simplest carbohydrates
-they’re important in living things as source of energy
-well suited due to large number of carbon-hydrogen bonds
-they’re sugars, soluble in water, insoluble non polar solvent
-can exist as straight chains (triose and tetrose)
-or can ring or cyclic forms (pentoses and hexoses)
-have backbone of single bonded carbon atoms with one double bonded to oxygen atom to form carbonyl group
-different sugars have different numbers of carbon atoms
-hexose=6/ pentose=5/ triose=3
-monosaccharide hexose sugars like glucose, are monomers of more complex carbohydrates and they bond to form disaccharides or polysaccharides
