Flashcards
LSC 10034
Flashcards do conjunto (19)
- 1LSC 10034Nature’s Tools - Proteins and Enzymes
- 2Non-covalent bonding InteractionsImportant in protein molecules, in terms of not only activity and specificity, but also in terms of folding and stability.
- 3These weak interactions between non-bonded atoms all arise fromdifferences in electric charge between these atoms.
- 4Groups of atoms which have chargesPOLAR
- 5they can interact with each other through attraction between opposite charges.ionic bonds.
- 6Molecules or groups of atoms that have both δ+ and δ- interaction between these dipoles that is mainly responsible for the weak interactions and for protein stability.DIPOLES
- 7Hydrogen bonds.Arising from interactions between permanent dipoles (and between permanent dipoles and charged groups)
- 8van der Waals forcesArising from interactions between transient dipoles
- 9HydrophobicityArising from, but not directly involving, dipole-dipole interactions
- 10How do the charges giving rise to the dipoles and dipole-dipole interactions arise?Charged groups
Due to Base/Acid character
Permanent dipoles
Due to electronegativity.
Transient dipoles
Varying charge distributions induced by interactions between
non-polar groups - 11ElectronegativityCovalently bonded atoms often do not share the shared electrons equally.
This inequitable sharing of shared (covalent) electrons arises from asymmetry in the electron orbitals of the atoms involved. - 12THE WATER DIPOLE• Exist as permanent dipoles due to electronegativity
• Water molecules have a relatively strong adhesion for each other
• The permanent dipoles interact with each other.
• These dipole-dipole interactions are called Hydrogen bonds
• Each water molecule can form up to 4 hydrogen bonds - 13THE HYDROGEN BOND• Hydrogen bonds form when a H atom is partly shared between a H donor atom (atom bonded to the H) and acceptor atom
• Both the donor and acceptor atoms must be strongly electronegative (both are O in water) - 14PROPERTIES of HYDROGEN BONDS• H bonds are strongest when the donor, H and acceptor are in line
• a single H bond is weak
• hydrogen bonds are additive
• many hydrogen bonds can give rise to a strong structure (e.g. ice)
• In proteins the formation of regular patterns of H bonds gives rise to the formation of regular structures (as we shall see)
• H bonds are often important in the function of a protein
• H bond distance is around 2.5 (strong) – 3Å (ie. 0.25 – 0.3 nm). - 15The van der Waals forceThis is again electric in origin, arising from the effect that neighbouring groups of atoms have on each others electric charge distributions, but operates between all molecules particularly when their shapes fit each other well.
• transient dipoles can be induced in adjacent molecules
• these transient dipoles are very weak and fleeting but result in an attractive force
• Interactions are individually very weak (0.5 kJ/mol)
• Additive - can be strong if many atoms make contact (e.g. in a folded protein) - 16The molecules interfere with the water-water hydrogen bonds simply by getting in the way and will be squeezed out by the attractions between the δ+ and δ- charges in the water. The molecule is termedHYDROPHOBIC
- 17If the molecule(s) added to the water are polar with their own δ+ and δ- charges (eg O and/or N), they will be able to participate in the hydrogen bond network in the water. Such a molecule isHYDROPHILIC
- 18Some molecules will have both hydrophobic and hydrophilic parts (eg. Lipids). Such molecules are calledAMPHIPATHIC
- 19—
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- Biomedical Science FlashCards sobre LSC 10034, criado por Wythehi Ambihapathy em 02-01-2017.
- Criado por
- Wythehi Ambihapathy
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