EduNinjaFig. 1.1 is a diagram showing a stage in protein synthesis.
Fig. 1.1
Name the stage of protein synthesis that is shown in Fig. 1.1.
Identify A, B and C in Fig. 1.1.
A
B
C
State the base sequences at D and E.
D
E
Antibodies are secreted by activated B-lymphocytes known as plasma cells.
Fig. 1.1 is a diagram showing the cellular processes involved in the production of a polypeptide of an antibody molecule (not drawn to scale).
Fig. 1.1
Name molecule D.
D
State what is occurring at 1,2 and 3.
at 1
at 2
at 3
The genes responsible for antibody production are found on different chromosomes, such as chromosomes 2 and 14 in humans.
Explain how one antibody molecule is the product of more than one gene.
Fig. 1.1 is a photomicrograph of plant root cells near the growing tip. Some of the cells are undergoing mitosis.
Fig. 1.1
Mutations can sometimes occur in cells which are rapidly dividing.
Outline how a mutation can cause an altered polypeptide to be produced.
Fig. 1.1 shows a diagram of part of a cell surface membrane.
Fig. 1.1
Structure E is a protein composed of 588 amino acids.
Calculate the minimum number of nucleotide base pairs required in the gene coding for this protein. Show your working.
Answer =
Protein production involves a complex sequence of events and a number of cell structures.
One example of protein modification is the removal of the first amino acid, methionine, from a newly formed polypeptide chain to make a functioning protein.
Suggest two other ways in which the polypeptide chain is modified to produce the functioning protein.
Fig. 1.1 shows part of a guard cell.
Fig. 1.1
State the type of protein represented by Q.
Phenylketonuria (PKU) is a genetic disease which results in a raised concentration of the amino acid phenylalanine in the blood. If left untreated in a newborn baby, it can lead to brain damage. For this reason, babies may be tested for PKU soon after birth.
In people without PKU, excess phenylalanine is converted to the amino acid tyrosine by the enzyme phenylalanine hydroxylase (PAH). One of the mutations that can lead to PKU is caused by a base substitution in the gene coding for PAH. This results in the replacement of the amino acid arginine by the amino acid glutamine.
Table 1.1 shows the triplet base codes for arginine and glutamine.
Table 1.1
Using the information in Table 1.1, explain how a single base substitution can replace arginine with glutamine in PAH.
Suggest the consequence to the structure of PAH as a result of a single base substitution in its gene.
Smooth muscle is a tissue composed of smooth muscle cells. The cells contain cytoplasm packed with proteins that are involved in contraction and relaxation.
Caldesmon is a large protein with a number of binding sites to attach to other proteins.
Caldesmon exists in two different forms, H-caldesmon and L-caldesmon.
H-caldesmon helps to regulate contraction and relaxation in smooth muscle cells.
L -caldesmon is found in some non-muscle cells, where it also acts as a regulatory protein.
- Caldesmon is coded for by a gene known as CALD1.
- CALD1 has 17 exons.
- The primary structure of H-caldesmon has a repeating sequence in the middle of the amino acid chain that is not present in L-caldesmon.
Researchers have discovered that a gene mutation is not the cause of the two different forms of caldesmon.
Explain what is meant by a gene mutation.
Researchers now know that the two different forms of caldesmon are the result of events occurring directly after transcription of DNA. Changes occur to the primary transcript that is formed by DNA transcription.
Suggest how the smooth muscle cells and non-muscle cells can produce different forms of caldesmon from the same primary transcript.
Fig. 1.1 is a transmission electron micrograph of cells from duckweed, Spirodela oligorrhiza.
magnification \(\times 4275\)
Name a cell structure that produces mRNA.
Fig. 1.1 shows the structure of the amino acid glycine.
Fig. 1.1
Plasma cells synthesise and secrete antibodies.
Fig. 1.3 is a transmission electron micrograph showing a plasma cell.
Fig. 1.3
Use a label line and the label T on Fig. 1.3 to identify where the genes coding for the polypeptide chains of the antibodies are located.