Week 17 Flashcards
what are atoms?
Atoms are the smallest particles that retain the properties of an element
what are atoms made up of?
Atoms are made up of sub atomic particles called protons, neutrons and electrons.
what is biological chemistry largely determined by?
It is largely determined by the physio- chemical properties of these atoms.
what is the physical chemistry of an atom determined by?
How do electrons distribute around the atomic nucleus?
How do electrons move between shells?
It is determined by its complement of electronic charge and their distribution
they distribute around the atomic nucleus in spaces described as shells or orbitals which define the probability of an electron (or electrons).
electrons move between these shells only on input and release of energy.
When do bonds arise?
What are the most stable atomic states?
Bonds arise in order to fill or empty shells.
the most stable states are
- with paired electrons
- with filled electron shells
Atoms with unpaired electrons and partially electrons and partially- filled outer shells react to fill or empty the shell.
What bonds are important for life?
What is the compound structure determined by?
- Ionic bonds arise when atoms exchange electrons
- covalent bonds arise when atoms share electrons
- compound structure is determined by the valence shells in the bonds.
What other bonds are also important?
What do these other bonds include?
Weaker interactions are also important.
Hydrogen bonds- partial charge interactions between polar molecules
Van der Waals interactions arise from locally induced dipoles between atoms in very close proximity
why is water a universal solvent for life?
What does hydrogen bonding explain?
What structure do hydrogen bonds give water?
what does the polarity of water allow?
water (H20) is a polar molecule and forms hydrogen bonds
hydrogen bonding explains
- cohesive and adhesive properties
- high specific heat (hence a good insulator).
Hydrogen bonds give water its crystal structure and ridgidity in ice and enable plant transpiration
The polarity of water allows
- salvation interactions with charged (ionic) compounds (forms ‘hydration’ shells)
- salvation interactions with uncharged polar compounds
- high reactivity with many other transition metals/ atoms
what is PH?
What concentration does water occur at?
- pH is a property of water and its polarity- pH defines the acidity/ alkalinity of a solution.
- water occurs at high concentration- 55M
What is a buffer?
What does carbonic acid buffer?
A buffer is a substance that suppresses (or buffers!) changes in (X).
pH buffers are compounds that changes in (H+).
Water is a ‘buffer’, because it suppresses changes in (H+) so that (H+) x (OH-) = 10-14.
Carbonic acid buffers blood, because
- under stress …. H+ + HCO3 combine to form H2CO3 removing acid from solution.
- under alkaline stress…. H2CO3 dissociates to form H+ + HCO3 adding acid to solution.
Summary of lecture 1
- atoms are elemental units, composed of sub- atomic particles
- atoms form bonds based on their atomic shell valencies and, in stable compounds, approximate filled shell Valencies
- C, H, N and O are the most important elements of life
- the unique properties of water relate to its polarity and ability to form hydrogen bonds
- pH is a measure of the acidity/ alkalinity of solution and is equal to the negative of the log10 of the (H+).
what are polymers?
what are biological polymers generally formed by?
Examples of common polymers
polymers are molecules built of repeated subunits
Biological polymers are generally formed by dehydration (water removal)
Common polymers include- DNA, RNA, Proteins, cellulose, keratin, lipids.
What are membranes?
membranes are phosphilipid polymers of fatty acids, glycerol, phosphate and a terminal amine or alcohol group
Membrane phospholipids are……. and in water they…..
membrane phospholipids are amphipathic molecules- in water they spontaneously form monolayers and bilayers.
Simple detergents are salts of fatty acids and are able to interact and dissolve other organic compounds.
why are membranes so important?
cellular membranes function…
- to compartmentalise metabolic activities
- to separate/ protect a scaffold for signalling
- as a medium for cellular energy generation
compartmentalisation, protection and energy generation arises from the immiscibility of water and membranes.
