Exam (elaborations)
AQA A-level biology example essay 2022
- Course
- Institution
AQA A-level biology example essay: Explain the importance of ions in biology
[Show more]
Seller
Follow
NURSMontero
Reviews received
Content preview
,Describe how you would use a biochemical test to show that a solution contained a non -reducingsugar, such as sucrose. [3] - ,first reducing sugars test; boil with dilute HCl acid then Neutralise with
NaHCǑ, add benedict and heat to 95 degrees C brick red ppt forms if reducing sugar is present
1. Describe a chemical test you could carry out to show that a piece of coconut contains lipids. [3] -
(Crush in) ethanol / alcohol; Add (to) water (Order of adding is critical for this point); Emulsion /
white colour
2. Explain what is meant by a polymer. [1] - Molecule) made up of many identical/similar
molecules/monomers/ subunits;
3. Name the reaction which occurs when starch is broken down into maltose. [1] - Hydrolysis
4. What is the formula for lactose? [2] - C12 ; H22Ō1
5. Describe how β-glucose molecule differs from a molecule of α-glucose. [1] - H at top right end
(instead of OH) / OH at bottom (carbon 1)
6. Show two ways in which the structure of cellulose is different from the structure of starch. [2] -
Starch 1,4 and 1,6 bonds / branching Cellulose 1,4 bonds / no 1,6 bonds / straight; starch All
glucoses /monomers same way up cellulose Alternate glucoses upside down; starch Helix /
coiled/compact cellulose Straight; Starch monomer Alpha glucose Cellulose monomer Beta
glucose
7. Describe the structure of starch and explain how its structure is related to its function. [3] -
Formed from α glucose; Joined by condensation/ by the removal of a water molecule/ glycosidic
bonds; Between (carbons) 1 and 4 (and 1 and 6); Coiled chain; compact; (Allows) storage of large
amount in a small space; Insoluble so has no effect on osmosis/water potential; Branches;
(Allows) rapid breakdown/release of glucose / hydrolysis;
8. The structure of a phospholipid molecule is different from that of a triglyceride. Describe how.
[2] - triglyceride has three fatty acids and phospholipid has two; no phosphate group present in
triglyceride but present in phospholipid.
, 9. What is an unsaturated fatty acid? [1] - Some / two carbons with only one hydrogen / (double
bonds) between carbon atoms / not saturated with hydrogen;
10. Describe the structure of cellulose and explain how its structure is relate d to its function. [3] -
Alternate β-glucose rotated 180o, long straight chains, Many hydrogen bonds join
(polysaccharide) chains/molecules to each other / makes microfibrils / gives tensile strength;
11. Which elements are found in proteins? [1] - Carbon, hydrogen, oxygen, nitrogen (sometimes
sulphur)
12. Describe how you would use a biochemical test to show that a solution contained protein. [2] -
Biuret / alkali + copper sulphate; Lilac/purple/mauve/violet;
13. Which bonds are found in a)Primary structure [1]b)Secondary structure [1] c)Tertiary structure
[2] - a)Peptide b) Hydrogen (and peptide) c)Ionic, disulphide bridges, hydrophobic interactions
(hydrogen and peptide)
14. Explain how a change in the primary structure of a globular protein may result in a different
three-dimensional structure. [3] - Sequence of amino acids changes; tertiary structure
changes/folds in a different way; bonds form in different places (not peptide);
15. Describe how two-way chromatography is carried out. [2] - Run chromatogram then turn
through 90/right angle; With a different solvent;
16. Explain the advantage of using two-way chromatography to separate short polypeptides. [2] -
Spreads spots/polypeptides out more/ make sure spot only contains one substance;
17. Explain how inhibitors affect the rate of enzyme-controlled reactions. [6] - Statement about two
types, competitive and non-competitive; Competitive: Similar shape to substrate;Inhibitor can
enter/bind with active site (of enzyme);Non-competitive: Affect/bind to enzyme other than at
active site; Distorts shape of active site; Inhibitors: Prevent entry of/binding of substrate to
active site; Therefore fewer/no enzyme-substrate complexes formed;
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 or Stuvia-credit 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 NURSMontero. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $12.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
76710 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now