1A - Chemistry of Life Flashcards
(23 cards)
polar molecule
a molecule containing a dipole
dipole
the sepration of charge in a molecule when the electrons in covalent bonds are not evenly shared
dissociation
splitting of a molecule into smaller molecules, atoms or ions, especially by a reversible process
hydrogen bonds
weak electrostatic intermolecular bonds formed between polar molecules containing at least one hydrogen bond
nitrate ions (NO3-)
(plants) make DNA, amino acids, and proteins from the products of photosynthesis
phosphate ions (PO4^3-)
(all) make ATP, ADP, DNA and RNA
chloride ions (Cl-)
(animals) needed in nerve impulses, sweating and secretory systems
hydrogencarbonate ions (HCO3-)
(animal) buffer blood pH to prevent it becoming too acidic
sodium ions (Na+)
(animals) needed in nerve impulses, sweating and secretory systems
calcium ions (Ca2+)
(plants) for formation of calcium pectate for the middle lamella between two cell walls
(animals) for bone formation and muscle contration
hydrogen ions (H+)
for cellular respiration and photosynthesis, and in numerous pumps and systems as well as pH balance
magnesium ions (Mg2+)
(plants) needed for production of chlorophyll
why is water a polar molecule?
electrons are held closer to the oxygen atom than to the hydrogen atom
how are hydrogen bonds formed between water molecules?
the slightly negative oxygen atom of one water molecule will attract the slightly positive hydrogen atoms of another water molecule => hydrogen bond
Simplified reasons to the importance of water
- ionic substances can dissolve in it
- it’s an excellent transport medium
- ice is less dense than water and floats => forming an insulating layer
- has a high specific heat capacity
- incompressible
- water molecules are cohesive
- water molecules are adhesive
- high surface tension
how does water allow ionic substances to dissolve in it
because water is a polar molecule, many ionic substances like sodium chloride dissolve in it
- many covalently bonded substances are polar and will dissolve in water, but often do not dissolve in other covalently bonded solvents
why is water an excellent transport medium?
because the dipole nature of water enables many different substances to to dissolve in it
how is ice less dense than water and why is this a good thing for living organisms?
- max density of water is at 4C
- further cooling = molecules become more widely spaced = ice less dense and floats
- ice forms an insulating layer and prevents water underneath from freezing
- melts quickly since its exposed to sun
- so temperature of large bodies of water doesn’t change much => good habitats for living organisms
importance of water being incompressible?
its important in many hydraulic mechanisms in living organisms
importance of water being cohesive?
- (cohesive = forces between the molecules mean they stick together)
- important for the movement of water from the roots to the leaves of plants (transpiration pull)
importance of water being adhesive?
- (adhesive = attracted to other different molecules)
- important in plant transport systems and in surface tension
why does water have a surface tension?
- the attraction between the water molecules (including hydrogen bonds) is greater than attraction between water molecules and air
- so, water molecules hold together forming a thin ‘skin’ of surface tension
importance of water having high surface tension?
- important in plant transport system
- affects life at the surface of ponds, lakes and other water masses
