Biomolecules Flashcards
State the constituent elements that make up each biomolecule.
Carbohydrates: C, H, O (H:O = 2:1)
Proteins: C, N, H, O, S (sometimes)
Fats: C, H, O (much less O in proportion to H as compared to carbohydrates)
State the primary structure of proteins.
Primary structure of protein is a long chain of amino acids. Proteins differ in variety, number and order of amino acids.
State the secondary structure of proteins.
Secondary structure of protein develops when either part of or all of the polypeptide chain becomes coiled to produce an alpha helix or folded to become a beta sheet.
State the tertiary structure of proteins.
Tertiary structure is a precise, compact structure, unique to the protein that arises when the molecule is further folded and held in a particular complex shape. An example is lysozyme.
State the quarternary structure of proteins.
Quaternary structure of protein arises when two or more polypeptides become held together, forming a complex, biologically active molecule. An example is haemoglobin (4 polypeptide chains; 2 alpha chains and 2 beta chains).
Starch: state the structure, role and occurrence.
Structure: Made up of several thousand glucose molecules joined together.
Role: Storage from of carbohydrates in plants. When needed, can be digested into glucose to provide energy in the form of ATP for cellular activities.
Occurrence: Found in storage organs of plants (potato tubers, tapioca, etc.)
Cellulose: state the structure, role and occurrence.
Structure: Cellulose molecule is made up of many glucose molecules joined together. The bonds between glucose units are different from that of starch.
Role: Cellulose cell wall protects plant cells from lysis or damage. Cellulose cannot be digested in our intestines. The starve as dietary fibre that prevents constipation.
Occurrence: Present in cellulose cell walls of plant cells.
Glycogen: state the structure, role and occurrence.
Structure: Glycogen is a branched molecule. It is made up of many glucose molecules joined together.
Role: It is a storage form of carbohydrates in mammals. When needed, it is digested to glucose to provide energy in the form of ATP for cell activities.
Occurrence: Stored in the liver and muscles of mammals.
State the monomers of the following macromolecules:
1. Polypeptides/Proteins
2. Polysaccharides/Complex carbohydrates
- Amino acids
- Monosaccharides/single sugars (glucose, fructose)
State the building blocks of fats/lipids. Are fats considered macromolecules? Explain. Are their building blocks considered monomers? Explain.
Fats/lipids are made up of 1 unit of fatty acids and 3 units of glycerol. No, fats are not considered macromolecules, but are rather big molecules as their structure is not as extensive as that of carbohydrates or proteins. The building blocks of fats are not considered monomers as there are 2 different (types of) building blocks, glycerol and fatty acids.
How do you identify carbohydrate and polypeptide molecules?
Polysaccharide molecules always contain hexagons while polypeptide molecules always contain nitrogen.
What kinds of bonds link the different kinds of biomolecules?
Carbohydrates — Glycosidic Bond
Polypeptides — Peptide Bond
Lipids — Ester Bond
Test for starch: Procedure, Observation and Conclusion.
Starch-iodide test: Add 1 drop of test solution and 1 drop of iodine solution onto a white tile and mix well. Observe any colour change. If the mixture turns from yellowish-orange to blue-black, starch is present. If the mixture remains yellowish-orange, starch is absent.
Solid sample: Add 1 drop of iodine solution to the sample and observe for any colour change.
Test for protein: Procedure, Observation and Conclusion.
Biuret test: Add 1.0cm^3 of test solution and 1.0cm^3 of Biuret reagent to a clean, dry test tube and shake to mix. Shake well and observe any colour change, If the mixture turns from blue to lilac, protein is present. If the mixture remains blue, protein is absent.
Solid sample: Chop/Grind samples and dissolve using distilled water. Decant or filter to obtain test sample.
Test for reducing sugar: Procedure, Observation and Conclusion.
Benedict’s test: Add 1.0cm^3 of test solution and 1.0cm^3 of Benedict’s solution to a clean dry test tube and swirl. Leave the test tube in a boiling water bath for 3 minutes and observe for formation of precipitate. If a brick red precipitate was obtained from a blue mixture, a large amount of reducing sugar is present.
(Use same phrasing as brick red):
Orange — Moderate
Yellow — Low
Green — Trace
If the mixture remained blue, reducing sugar is absent.
Solid sample: Chop/Grind samples and dissolve using distilled water. Decant or filter to obtain test sample.
