2.1.2abc Biological Molecules - water + principles of biomolecules Flashcards
water 2.1.2a (40 cards)
Draw a water molecule, label the atoms and their charges
on flashcard
hydrogen - slightly +
water - slightly -
What is the structre of a water molecule
1 Oxygen atom covalently bonded to 2 hydrogen atoms
- non-linear shape
What is the bond linking 2 water molecules together?
Hydrogen bond
What is a hydrogen bond and which type of atoms does it join together?
- A weak interaction that occurs whenever molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen
Where else do hydrogen bonds occur in biology?
DNA
polysaccharides
proteins
Draw 2 water molecules and draw and label the bond that links them together
on flashcard
on flashcard
Define polar
the presence of unevenly distrubuted charge on 2 poles
one is slightly + and one is slightly -
Why is water a polar molcule?
the oxygen (-) atom is more attractive to electrons than hydrogen (+) so pulls the shared electrons towards it,
- causes O to be slightly - and Hs to be slightly positive
Define electronegativity
a measure of the tendancy of an atom to attract a bonding pair of electrons
Define dipole
a molecule in which a concentration of positive electric charge is seperated from a concentration of negative charge
What are the 5 roles water plays in life?
- Solvent
- Transport medium
- Habitat
- Reactant
- Thermal stability
Why does the polar nature of water allow it to be used as a solvent?
as water is polar:
-water dissolves polar and charged molcules
- many solutes are polar: amino acids, proteins,nucleic acids
->water acts as medium for chemical
reactions
Why does the polar nature of water allow it to be used as a transport medium?
as water is polar:
- cohesion between water molecules= when water moves through body molecules stick together
-adhesion between water molecules and other polar molecules + surfaces
adhesion+cohesion = capillary action
- water moves up narrow tube via gravity
Why does the polar nature of water allow it to be used as a coolant?
- high specific heat capacity as H bonds require lots of energy to break
- maintains constant temperature
Why does the polar nature of water allow it to be used as a habitat?
-maintains constant temperature due to high energy required to break H bonds
-less dense when it freezes
=survival+reproduce
Define hydrophilic
a molecule attracted to water
Define hydrophobic
a molecule repelled by water
Define cohesion
water molecules attracted to one another
Define adhesion
water molecules attracted to other substances
Summarise the 5 properties of water
*High specific heat capacity - hydrogen bonds between water molecules absorb lots of energy - good habitat
*High latent heat of evaporation (liq->gas) - good coolant eg sweat evaporates+cools skin
*Very Cohesive (bc polar) - helps water to flow - good transport medium
e.g. water up stems in transpiration stream
*Lower density when solid - water molecules held further apart in ice than in liq water bc each water molecule forms 4 hydrogen bonds = lattice shape
ice less dense than water - insulating layer on top of water (water below doesnt freeze) - habitat
* Good solvent - bc water polar - slightly positive end of water molecule attracted to negative ion and slightly negative end of water molecule attracted to positive ion
= ion surrounded by water = dissolve
What are other properties (not polar related) of water that make it useful for life?
transparent
- plants growing underwater can get light for photosynthesis
- aquatic animals can see underwater
Give 10 examples of how water is used across the whole diversity of life (prokaryotes+eukaryotes; plants+animals+fungi ; unicellular and multicellular organisms)
S+C
Support - keep plant cells turgid, hydrostatic skeletons of earthworms
Lubrication - joints such as elbow synovial joints have sac of synovial fluid stopping bones rubbing against each other
Bouyancy - Whales couldn’t be so big etc.
Swimming - When something pushes against water there is an equal reactive force propelling forward
Reactions - Photosynthesis, hydrolysis
High surface tension allows organisms to suspend themselves at/on the surface e.g. pond skaters
Ice floats as less dense so insulates water underneath where organisms can survive
Regulating temperature and reaction conditions etc. - sweating as well as high heat capacity
Using the “polar nature of water” explain 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
S+C
Dome: Cohesion between water molecules causing surface tension due to hydrogen bonds
Meniscus: 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 monomer
individual molecules that make up a polymer
