Molecular Biology 2.2 Flashcards
What is Cohesion ?
When molecules of same type are attracted to each other.
why cohesive properties of water are useful ?
1) Helps water to form droplets
2) Helps water to have surface tension
3) Water can move as water column in vascular plants
Cohesion and surface tension in water
1) However for a molecule on the surface of the liquid, there will be a net inward force since there will be no attractive force acting from above. This inward net force causes the molecules on the surface to contract and to resist being stretched or broken. Thus the surface is under tension, which is probably where the name “surface tension” came from.
2) Due to the surface tension, small objects will “float” on the surface of a fluid, as long as the object cannot break through and separate the top layer of water molecules. When an object is on the surface of the fluid, the surface under tension will behave like an elastic membrane.
Adhesion
Any attraction between 2 unlike molecules
1) It works when a column of water is being pulled up in Vascular tissue
Thermal properties of water
1) High specific heat capacity
2) Water absorbs or gives off great deal of heat without changing temperature very much.
3) Water is a temperature stabilizer in living things.
4) Cooling mechanism: high heat of vaporization therefore water absorbs great deal of heat when it evaporates.
Solvent Properties of water
1) Excellent solvent for polar molecules like carbs, nucleic acids, proteins.
2) Because of this, most of the biochemical reactions take place in aqueous solutions.
3) Glycolysis/Protein synthesis reactions take place in Cytoplasm
4) Nucleoplasm (contains water)= DNA replication and RNA synthesis.
5) Stroma(fluid inside chloroplast)= light independent reactions of photosynthesis.
6) Blood plasma= Loading and unloading of respiratory gases.
Examples of water as an excellent solvent
1) Xylem in plants carries water and dissolved minerals
2) Blood is largely composed of water.It carries glucose,amino acids, fibrinogen and hydrogen carbonate ions.
Why carbohydrates are hydrophilic ?
Due to its hydroxyl functional group !
Examples of Hydrophobic molecules
1) Fatty acids
2) Phospholipids
Carboxylic group in fatty acids
1) It gives slight polarity
Polarity of Protein molecules
1) Depends on the arrangement of amino acid
2) Some amino acids are relatively polar and some are non-polar.
Cholesterol and Fats
1) Largely non-polar
2) very low solubility in water
3) Therefore, transported by blood proteins that have polar amino acids on the outer portion to give water solubility and non-polar amino acids on the inside to bind with fats and cholesterol molecules
Oxygen
1) Low solubility
2) Travels as Diatomic gas
3) Specially in warm blooded animals oxygen is less soluble due to high temperature
4) Hemoglobin is used to bind and transport oxygen molecules.
