100% satisfaction guarantee Immediately available after payment Both online and in PDF No strings attached
logo-home
Unit 3 assignment 1, 2, 3 £6.99   Add to cart

Presentation

Unit 3 assignment 1, 2, 3

 30 views  0 purchase

Presentation study book Essential Cell Biology of Bruce Alberts, Dennis Bray - ISBN: 9780393680393 (pass guaranteed)

Preview 2 out of 5  pages

  • January 20, 2021
  • 5
  • 2019/2020
  • Presentation
  • Unknown
book image

Book Title:

Author(s):

  • Edition:
  • ISBN:
  • Edition:
All documents for this subject (4)
avatar-seller
cAabdul123
Investigate the use of chemical reagents to identify starch, reducing sugars,
proteins.
Introduction:
In this practical will be provided with the concentration of starch. Then using
the technique of serial dilution to make a number of other lower
concentration. Then add a constant amount of Iodine indicator to each, using a
colorimeter find how much light its absorbed through each sample. Using this
data, a graph will be used which will show the relationship between the
concentration of the starch and the light level. Finally the samples of food
concentration will be found. Use the colorimeter and calibration curve to find
the concentration of the food samples.
Background Theory:
Starch is an example of a natural polymer. A polymer is a long and repeating
chain of the same molecule stuck together. Starch is a long-chain polymer of
glucose molecules joined together. Starch, a white, granular, organic chemical
that is produced by all green plants. Starch is a soft, white, tasteless powder
that is insoluble in cold water, alcohol, or other solvents. The basic chemical
formula of the starch molecule is (C6H10O5)n. Starch is a polysaccharide
comprising glucose monomers joined in α 1,4 linkages. The simplest form of
starch is the linear polymer amylose; amylopectin is the branched form.
Iodine is a chemical element. The body needs iodine but cannot make it. The
iodine needed by the body must come from the diet. As a rule, there is very
little iodine in food, unless it has been added during processing. Processed
food typically contains more iodine due to the addition of iodised salt. Most of
the world's iodine is found in the ocean, where it is concentrated by sea life,
especially seaweed.
Iodine is the test for starch, when starch is present the yellow/orange iodine
solution becomes a blue/black colour. The iodine will be present in the centre
of the starch helix, forming a starch iodine complex. Starch is a carbohydrate
found in plants. It consists of two different types of polysaccharides that are
made up of glucose units which are connected in two different ways. One is
the linear amylose and the other is the branched amylopectin.

, Amylose is the compound that is responsible for the blue colour. Its chain




forms a helix shape, and iodine can be bound inside this helix.
Amylose forms a colloidal dispersion in hot water whereas amylopectin is
completely insoluble. The structure of amylose consists of long polymer chains
of glucose units connected by an alpha acetal linkage. Starch - Amylose shows
a very small portion of an amylose chain.
Boiling a starch solution causes temporary unwinding of the helix and the
subsequent release of the iodine molecule, the blue/black colour will
disappear, and when the helix cools down the blue/black colour will re-form.
This effect is measured by the quantity of concentration rather than its quality.


Colorimeter This instrument calculates the density of the coloured solution, for
example, when iodine is applied to starch, it can be used to determine the
concentration of a compound solution.
Reference:
https://en.m.wikipedia.org/wiki/Iodine_test
www.chemieunterricht.de 2006.

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

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

Quick and easy check-out

You can quickly pay through credit card for the summaries. There is no membership needed.

Focus on what matters

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 cAabdul123. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy these notes for £6.99. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

70055 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

Start selling
£6.99
  • (0)
  Add to cart