BIOC2000 Lecture Notes - Lecture 2: Supramolecular Assembly, Salt, Micelle
Lecture 2
Prework defines what to learn for the exam; big indicator
DISCUSSING PRE-WORK
Biomolecule type
Soluble in water?
Not soluble in water?
DNA
✔ Charge from
phosphate groups
allows DNA and RNA to
be soluble in water.
Interaction of water and
H between bases.
RNA
✔ DNA and RNA both
very soluble!
Carbohydrate
Yes small ones are soluble.
Big polymers are not soluble once they make enormous
aggregates.
Shape and way molecules pack against each other is influential on
how soluble it is in water.
Protein
SOMETIMES
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Lipid
SOMETIMES
Sometimes lipids can be suspended in water in particular
structures.
- Micelle: aggregate (or supramolecular assembly) of fatty acids
dispersed in a liquid colloid.
Tails of fatty acids are IN
Heads of fatty acids are OUT
Tails are hydrophobic, fatty acids have a charged head on them
Not ‘soluble’ in water, but suspended in water
- Bilayers
Charged things in water are soluble.
(1)(2)
Misconception: ‘Solubility means breaking apart into constituent pieces’
Solubility of macromolecules is different to solubilisation process seen in
salt crystal
Salt crystal being ‘soluble in water’ – constituent ions break off and
become hydrated with water; water sits around ions in a hydration cell
A soluble macromolecule doesn’t ‘break up’ like this
Exam question: ‘ What happens when glucose becomes soluble in water?’
Glucose molecules remain the same, and groups on it interact with water
through H bonding
In macromolecules, the backbones are covalent. In water, the vibrational
energy of water is not enough to break the covalent bonds, so they stay
together. – good thing about biomolecules : they are stable in water and
the constituents don’t break
Dark black lines don’t break up, water
interacts with charge on side
Know how to draw glucose
Phosphate groups in structure are charged.
Reason 1: That big row of charge in DNA and RNA means that they are
soluble in water. – phosphate backbone
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find more resources at oneclass.com
Document Summary
Prework defines what to learn for the exam; big indicator. Charge from phosphate groups allows dna and rna to be soluble in water. Big polymers are not soluble once they make enormous aggregates. Shape and way molecules pack against each other is influential on how soluble it is in water. Sometimes lipids can be suspended in water in particular structures. Micelle: aggregate (or supramolecular assembly) of fatty acids dispersed in a liquid colloid. Tails are hydrophobic, fatty acids have a charged head on them. Not soluble" in water, but suspended in water. Misconception: solubility means breaking apart into constituent pieces". Solubility of macromolecules is different to solubilisation process seen in salt crystal. Salt crystal being soluble in water" constituent ions break off and become hydrated with water; water sits around ions in a hydration cell. A soluble macromolecule doesn"t break up" like this. Exam question: what happens when glucose becomes soluble in water?".
