Biological Molecules - Water Flashcards
- How are the atoms in a water molecule combined?
- What is the charge of water?
- covalently bonded - has STRONG covalent bonds
- 0 (neutral)
What are the properties of water?
- High specific heat capacity
- Polar solvent
- High surface tension
- Incompressible
- Reaches its maximum density at 4 degrees C
Why is water a polar molecule?
The sharing of electrons in water is not equal. Electrons are held closer to the oxygen atom than the hydrogen atoms. This means oxygen has a very small negative charge(δ−) and the hydrogen atoms have a very small positive charge(δ+). Therefore water = polar molecule.
What is a polar molecule?
A molecule which has a region of positive and negative charge
Where are the hydrogen bonds found in water?
In between the water MOLECULES Not in between the atoms making up the molecule.
Describe the molecular structure of ice
- Hydrogen bonds hold water molecules in rigid lattice formation
- so molecules vibrate but don’t move around + bonds = harder to break
- less dense than liquid so floats on surface of water + INSULATES water below
Describe the molecular structure of liquid water
- Molecules have more kinetic energy than ice
- move past each other + form fleeting hydrogen bonds w each other: makes it more DifficulT for the molecules to escape
Describe the molecular structure of water vapour
- Molecules far apart + scarcely interacting w each other
Why is ice less dense than water in liquid form?
As the temp of water decreases, the kinetic energy of the individual molecules decreases –> molecules slow down. This means that each molecule is able to form the maximum num of hydrogen bonds w other water molecules. The water molecules spread out to accommodate more bond formation.
Why does water have a high specific heat capacity?
As water is heated the temp of the water rises. This means that the water molecules have more kinetic energy. As heat energy is added to the water a lot of this energy is used to break the hydrogen bonds between the water molecules. As a large amount of heat energy is used to break the hydrogen bonds there is less energy available to raise the temperature of the water. Therefore water requires a lot of heating to increase its temp tmt water is slow to absorb and release heat.
Why is water’s high SHC a useful property for organisms?
- Cells + tissues in org. have high water content - allows living organisms to maintain a particular temperature to OPTIMISE ENZYME ACTIVITY(enzymes less likely to denature)
- metabolism @ steady rate
- gases LESS soluble as temp INCREASES - means gases remain soluble - gas exchange
- Temp of large bodies of water does not change much throughout the year which makes good habitats for living organisms
Why does water have a high latent heat of vapourisation?
- Lots of heat energy required to make water evaporate because of the many hydrogen bonds. Water must be heated to 100 degrees C b4 the molecules have enough energy to break apart.
Why is water’s high latent heat of vapourisation useful for organisms?
- When liquid sweat lies on the surface of skin, water in the sweat absorbs heat energy from body as it evaporates - creates cooling mechanism + allows org. to maintain constant body temp
—> sweating = prevents overheating = less likely to denature enzymes - cooling transpiring leaves
Why is water incompressible? + why is this important in organisms?
Water is a liquid and has close packing of molecules so can’t be compressed.
- water provides a hydrostatic skeleton(earthworm movement) = hydraulic mechanism
- turgor pressure in plants(opening of stomata by making guard cells turgid)
- amniotic fluid - supports + protects foetus
Why is water cohesive?
cohesion - water molecules stick together bc hydrogen bonds form btwn O of 1 molecule and H of another - they attract each other.
cohesion causes surface tension.
Hydrogen bonds pull water molecules in at the surface.
water molecules are also adhesive = attracted to diff molecules
