Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

BIOCHEM
L1 – Bonding in bio compounds
Bonding in Biological Compounds:
•
•
•
•
•
•
•

Covalent bonding
Hydrogen bonding
Ionic bonding
Hydrophobic interactions
Polar and non-polar compounds

Covalent Bonding
•
•
•
•

A covalent bond between two atoms arises from the SHARING of a PAIR of electrons
...

Hydrogen would like to have 2 outer shell electrons
...


H forms 1 covalent bond
C forms 4 covalent bonds
N forms 3 covalent bonds
O forms 2 covalent bonds
F forms 1 covalent bond
Example:
Methane Carbon Group IV 4 outer shell electrons wants to share 4 electron pairs (make 4 covalent bonds)
...

Each hydrogen has 2 outer shell electrons
...

Hydrogen has 1 electron and would like 2 in order to fill its 1s subshell and attain
the structure of helium
...

• These in turn arise from differences in electronegativity between the atoms which make up
the polarised covalent bonds
...


Water
•
•

The shared pair of electrons of each O—H bond is closer to the oxygen
nucleus than the hydrogen nucleus
...


Ice has an ordered structure because of hydrogen bonding
...


The amide group –CO-NH– is both a H-bond donor and an acceptor
...


The two strands in DNA are held together by hydrogen bonding
...

•
•
•

Solvation of bio-molecules
Solubilisation of bio-molecules in water
• Hydrophilic groups of enzymes, peptide hormones and antibodies tend to be on the outside
...

•
• DNA helix
• Peptide -helix / -sheet
Important for substrate-receptor interactions
...


Hydrogen bonds are MUCH WEAKER than covalent bonds
...


Sodium chloride is an ionic solid comprising Na+ and Cl ions held together by ionic forces (electrostatic
interactions)
Common charged states of some biologically important mono-atomic anions and cations

The iron is present as Fe2+
Fe3+ is inactive
...

When molecules have large surface areas that can come into close contact, the total attraction from
such interactions can be VERY LARGE
...

❖ The 3D shape of a protein molecule is essential for its correct functioning, and Van der Waals forces are
important in maintaining this shape
...

To dissolve something in water involves breaking these hydrogen bonds – costs energy
...

Hydrophobic portions of bio-molecules tend to associate with each other because they “cannot pay the
energy cost
...

Hydrophobic amino acid side-chains in globular proteins tend to associate  hydrophobic core
...

Non-polar Compounds
usually deficient in electronegative atoms, hydrogen bonding groups or charged groups

Six key points:
1
...

2
...

3
...

4
...

5
...

6
...




---