Biological Molecules Flashcards
What is a polymer?
A molecule made of many identical/similar molecules/monomers/sub-units.
Describe the structure of an amino acid.
Normally a single carbon with 4 different groups attached - the “amino” part coming from a NH2 (amino group) and the “acid” coming from a COOH (carboxyl group), there is an “R” group which changes depending which amino acid it is, and the last thing attached to the carbon is a hydrogen.
How are amino acids joined together? What bond forms?
By a condensation reaction, where a molecule of water is removed, and the NH2 and COOH join in a HNCO (peptide) bond (One hydrogen is removed from the NH2, and the OH is removed from the COOH (leaving the doubly bonded O))
What is the primary structure of the polypeptide?
The sequence of amino acids.
What is the secondary structure of the polypeptide? What are the 2 examples?
The folding of the amino acid chain, being held by hydrogen bonds. The 2 common examples are beta pleated sheets and alpha helix.
What is the tertiary structure of the polypeptide?
Increased folding of the amino acid chain, being held by more hydrogen bonds, ionic bonds and disulphide bridges.
What is the quaternary structure of the polypeptide?
Numerous tertiary chains joined together.
How are proteins adapted to their roles as receptor molecules?
The tertiary structure of the polypeptide determines the shape of its active site, and this is complementary to the shape of their substrate, meaning only specific enzyme-substrate complexes can be formed.
How are fibrous proteins adapted to to their function? Give an example.
They are long chains of amino acids, folded into either a helix or pleated sheet and they are many polypeptide chains fitted together. they are insoluble as they have r groups that are non-polar. The fibres provide stability for the protein, for example, keratin in hair has these fibres and this makes hair stronger.
What is the test for proteins, and what would a positive result look like?
Biuret solution, if the solution turns from a light blue colour to a lilac colour it means that there is protein present.
What reaction produces triglycerides? What are the 2 reactants and what bond binds them together?
Condensation reaction. Glycerol and 3 fatty acids joined by 3 ester bonds.
What does benedict’s reagent test for? What does a positive result look like?
It tests for reducing sugars. If the solution turns brick red then a reducing sugar is present. If the solution stays blue, but then turns brick red when HCl and sodium hydrogencarbonate are added then a non-reducing sugar is present.
What is the test for starch? What does a positive result look like?
Iodine/Potassium iodide can be used to test for the present of a starch. If the solution goes from orange to brown, then starch is present.
What is the test for lipids? What does a positive result look like?
The emulsion test. If a lipid is present the solution will go from clear to cloudy.
What do enzymes do, and how do they work?
They speed up the rate of a reaction by providing an alternative reaction pathway that requires a lower activation energy.
What factors impact the rate of enzyme controlled reactions? How do they do this?
Temperature: Increased temp increases rate, as the kinetic energy increases, however this is only to a certain temp as the active site will become denatured at a certain temperature.
pH: Could increase/decrease depending on which enzyme it is, but if the pH is too acidic or alkaline it could denature the active site.
Enzyme conc: Increased conc increases rate, as there’s more active sites, but only to a certain point as if there are more active sites than substrates, the substrate conc becomes the limiting factor.
Substrate conc: Increased conc increases rate, as more enzyme-substrate complexes can be made, but only to a certain point as there are more substrates than active sites, the enzyme conc becomes the limiting factor.
Competitive reversible inhibitor conc: Increasing conc decreases rate, as the active sites become blocked.
Non-competitive reversible inhibitor conc: Increasing conc decreases rate, as the shape of the enzyme is changed.
What is the basic structure of the DNA nucleotide?
Deoxyribose sugar with a phosphate and base attached.
What are the bases that are in DNA? Which are complementary to each other?
Cytosine + Guanine, Adenine + Thymine
What is the basic structure of the RNA nucleotide?
Ribose sugar with a phosphate and base attached.
What are the bases that are in RNA? Which are complementary to each other?
Cytosine + Guanine, Adenine + Uracil
What bond attaches nucleotides together? What reaction does this bonding occur?
A phosphodiester bond. Condensation reaction.
What is the function of the phosphodiester backbone?
It protects the more chemically reactive nitrogen containing organic bases inside the double helix.
How many hydrogen bonds are between the two pairs of bases?
Two between adenine and thymine.
Three between cytosine and guanine.
What is meant by semi-conservative replication?
That the two strands produced have a strand from the original helix.
