Water, Acids, PH, buffers & Bases- Week 3 Flashcards
(33 cards)
what is the structure of water
consists of two hydrogen atoms bonded by covalent bonds to the oxygen atom.
Because of the higher electronegativity of the oxygen atom, the bonds are polar covalent (polar bonds).
explain why water is electronegative, what effect does it have on water
Oxygen is more electronegative than hydrogen- this leads to the polarity of water (polarity leads or facilitates the formation of hydrogen bonds)
what is the van der waals radius
its the area around the orbit around the atom where repulsion starts to take place- no atoms can get close than that van der waals
what are the characteristics of water
- Fairly high melting point
-Fairly high boiling point - High surface tension
-its polar
how many hydrogen bonds can 1 molecule of water form
4
what is the amount of energy needed to break a hydrogen bond
20kj of energy
whats the amount of energy needed to break a covalent bond
400kj of energy
what are the components for forming a hydrogen bond
- need a covalent bond
-need the covalent bond to be dipole (one component is electropositive & the other electronegative) - other molecule needs to be a electronegative atom
what are the 2 types of hydrogen bonds
weak & strong hydrogen bonds - they are characterised by the fact of the 3 components of the electropositive, electronegative, electropositive are on a straight line or not
what are some examples of hydrogen bonds
- between the hydroxyl group of an alcohol and water
- between peptide groups in polypeptides
- between complementary bases of DNA
- between the carbonyl group of ketone and water
give some examples of polar molecules
- Glucose
- Lactate
- Glycerol
- Glycine
what does polar molecules mean
hydrophilic compounds- form hydrogen bonds so are soluble in water
* hydrophobic compounds are non-polar as they cant form hydrogen bonds
Give an example of a Non-polar molecule
Typical wax
Give 2 examples of Amphipathic molecules
- Phenylalanine
- Phosphatidylcholine(its a phospholipid found in the membrane)
what does Amphipathic molecules mean
molecules which have both polar & Non-polar compounds
give 4 Non-covalent reactions
1- hydrogen bonds
2- Ionic compounds
3- Hydrophobic reactions
4- Van der waals interactions
(this are all relatively weak compared to covalent bonding)
explain how water is a solvent
when water is added it creates a HYDRATING SHELL around each ion, due to the dipolar nature of water
*can happen with sugar where the water interacts directly and creates hydrogen bonds with the sugar molecules
give an example of water acting as a reactant- explain it
means that water being a part of reactions in cells, ATP + H2O = ADP + Pi, it breaks phosphodiester bonds- provides energy for another reaction or can provide a phosphate in the reaction
why is water important for the regeneration of ATP
as water facilitates the transfer of both protons and electrons in the cell- called PROTON HOPPING (beneficial as its much quicker than diffusion of protons & electrons)
define acid
its a substance that produces hydrogen ions, by dissociation
whats the difference between strong & weak acids
Strong acids completely dissociate in water- produce H+
weak acids only partially dissociate in water, and an equilibrium is established
how is Base defied
its a substance that can:
1) extract a proton (H+) from water, forming hydroxide ion (OH-)
2) produce a hydroxide ion directly by dissociation
what effect will a strong base have on water, give an example of a strong base
it will dissociate completely in water- and will increase the PH of the solution
KOH(aq)—> K+ + OH-
what happens when weak bases react with water
they only partially react with water to EXTRACT a proton (H+) & LEAVE a HYDROXIDE ION (OH-)- equilibrium reached
