Summary
Summary - Unit 2 - B Biological Molecules (9700)
- Institution
- CIE
Summary notes on biological molecules according to the cie Cambridge international syllabus, and the corresponding textbooks.
[Show more]
Seller
Follow
Content preview
Biological moleculesBenedicts test - reducing sugars
1. Add a few drops of Benedict’s reagent (copper II sulphate) into the sample
2. Heat mixture (boiling water bath) — copper II sulphate -> copper (I) oxide
3. Blue -> coloured precipitate (green -> yellow-> red -> brown)
- Semi-quantitative -> also shows the amount of of reducing sugars in the sample
- Greater concentration, greater colour change
- Time to rst colour change
- Or comparison to colour standards
Safety precautions
- handle test tube with tongs
- Wear safety goggles and heatproof gloves
! not when measuring enzyme activity!
Benedicts test - non reducing sugars
1. No colour change = no reducing sugars
2. Add dilute hydrochloric acid and heat, then neutralise
- acid will break down non-reducing sugars into monosaccharides
- After adding acid neutralise with sodium hydrogencarbonate (NaHCO3)
3. Heat and observe colour change - repeat Benedict’s test
Iodine test - starch
1. Add aqueous iodine solution (Lugol’s solution) to the sample
- Iodine from potassium iodide solution - iodine doesn’t dissolve in water
2. Brown orange -> dark blue-black
- starch iodine complex
Emulsion test - lipids
1. Add ethanol and shake
- lipid dissolves in ethanol
2. Pour the solution into water
- since lipids are insoluble in water they will not mix with water and will oat on top
3. Check for formation of cloudy (milky white) emulsion
- if negative no emulsion
Safety precaution: Do not use near open ame, ethanol is amable
Biuret test - proteins
1. Add sodium hydroxide - to make the solution alkaline
2. Add copper (II) sulphate solution
- Benedict’s solution contains alkali and copper (II), no need for step one
3. Blue -> purple
- for the test to work there must be at least two peptide bonds
fi fl fl fl
, De nitions:
Monomer - a relatively simple molecule which is used as a basic building block for the synthesis of a polymer
Polymer - a molecule made from many similar repeating subunits (monomers) joined together in a chain, through
covalent bonds
Macromolecule - a very large molecule such as a polysaccharide, protein, nucleic acid
Carbohydrates
Cx(H2O)y
Monosaccharide - single sugar monomer
Disaccharide - a sugar formed from two monosaccharides joined together by a glycosidic bond by condensation
polysaccharide - a polymer formed by many monosaccharides joined by glycosidic bonds in a condensation reaction
to form chains
Covalent bonds
- Bonds where atoms are joined by sharing electrons
- Strong, require large energy to break them
Glucose
- a monosaccharide containing six carbon molecules = hexose
Glucose isomers
- in aqueous solutions glucose forms a ring structure
Reducing sugars: glucose, fructose, maltose
Non-reducing sugars: sucrose
fi
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller np3. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £7.26. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
53340 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now