Stage 2 Biology 2015
Macromolecules Formative Test One Answers:
Multiple Choice Answers
1. K 2. L
3. M 4. M 5. K
9. J
10. L 11. K 12. M
6. M
7. L
8. M
Short Answers:
1(a)
succinate dehydrogenase
1(b)
succinic acid + FAD
1(c)
Malonic acid acts as a competitive inhibitor in the active site of succinate
dehydrogenase due to its similar shape to the substrate succinic acid. This prevents
succinic acid being converted to fumaric acid.
2(a)
This is an alpha-helix.
2(b)
This reveals secondary structure in this polypeptide chain.
2(c)
Beta pleated sheets are also found in secondary level structure.
3
The semi-conservative replication of DNA means that when DNA replicates itself, the
two new identical copies will each be composed of one strand of the original piece of
DNA, and one strand that is new. This is because the two stands of the original piece
of DNA serve as template strands as new nucleotides are added by way of
complimentary base pairing.
(draw diagram of simple semi-conservative replication happening, and label
important parts)
4(a)
communication; messenger; hormone molecule
Its function is to act as a chemical message that can be passed through the body
triggering responses in various cells.
4(b)
receptor molecule
Its function is to receive messenger molecules that are specific in 3D shape to its
binding site. When this binding occurs a response is triggered in the cell contains
this receptor molecule.
4(c)
Because this messenger molecule (hormone) has a specific 3D shape that only fits
certain receptor proteins. Only the cells that have the receptor molecules with
binding sites that match this messenger molecule will be affected.
1
4(d)
Phospholipid molecule
5
Poisons that work in this way may act as competitive or non-competitive inhibitors.
Those that work as competitive inhibitors act by blocking the active site of the
enzyme that is needed by the body, thus preventing the enzyme from normal
function. Those that work as non-competitive inhibitors act by binding to an
alternate place on the enzyme and in doing so cause a conformational change to the
active site of that enzyme. This change prevents the active site from binding to
normal substrate, and prevents normal function. Either way, both of these may stop
an enzyme from working that is needed by the body.
Extended Response
1.
Both RNA and DNA polymerase are complex globular proteins that have either
tertiary or quaternary structure. Both of these enzymes bind to DNA to initiate and
facilitate the production of either RNA or DNA molecules based on the template
strand of DNA. They do this by adding nucleotides in the correct order.
These two molecules have highly specific 3D conformations with active sites that
directly match the nucleic acids they bind to. In other words, they are
complimentary in shape to their ‘substrate’ at their active site making them only
useful for the specific job of polymerizing RNA or DNA molecules from nucleotides.
These two types of molecules, although similar, have some key differences. RNA
polymerase is only used to facilitate the transcription of mRNA molecules from the
DNA template strand, making a single stranded nucleic acid molecule. DNA
polymerase, on the other hand, is used in DNA replication, facilitating the binding
bases forming the complimentary strand of DNA. The results is a double stranded
double helix of DNA.
2
DNA is described as the chemical unit of genetic information. The chemical itself is a
double helix molecule with two sugar-phosphate backbones running anti-parallel to
each other. In the middle nitrogenous bases (attached to the deoxyribose sugars)
match and bind together with hydrogen bonds. The genetic information is stored in
this molecule in the specific sequence of bases found along the DNA molecule.
DNA is packed around protein molecules and wound up forming chromosomes.
Humans have 46 chromosomes of these chromosomes. Each chromosomes contains
specific genetic instructions, called genes, that are located at specific locations called
loci. There may be hundreds or thousands of genes that have their own loci on a
chromosome.
2
Genes are the functional unit of genetic information. Each gene has the information
(specific sequence of bases) to code for a polypeptide molecule, which arises from
transcription and translation in the cell. The polypeptide molecule may be formed
into a protein or part of a protein molecule. Proteins have specific functions in the
cell and in the body which are critical for life. A gene may also code for a specific
type of RNA molecule which has a function in the cell.
3