set b Flashcards
Some diseases are linked to a failure in the endoplasmic reticulum (ER).
Cells of people with these diseases contain proteins that are folded incorrectly.
Some of these proteins are enzymes.
(a) Protein synthesis in eukaryotic cells occurs in
- 80S ribosomes on the endoplasmic reticulum
Many of the proteins synthesised become extracellular enzymes.Describe what happens to these proteins following the process of translation until they are released from the cell.
- goes to the rer and packaged into a vesicle and transported to the golgi body
- at the golgi body the protein is modified and packaged into a vesicle and transported to the cell surface membrane
- the vesicle fuses with the cell surface membrane(exocytosis)
Cells in people with these diseases produce incorrectly folded enzyme molecules.Explain why enzymes that are incorrectly folded cannot carry out their function.
- if the protein is not folded correctly then the tertiary structure would be different
- this alters the active site as bonding has changed so its no longer complementary to the substrate
- therefore unable to catalyse the reaction
The sundew is a small flowering plant, growing in wet habitats such as bogs and
marshes. The soil in bogs and marshes is acidic and has very low concentrations of
some nutrients. The sundew can trap and digest insects.
0 9 . 1 Describe how you could estimate the size of a population of sundews in a small
marsh.
- use a quadrat
- measure a particular area to investigate
- use a random number generator for numbers to use as coordinates
- count the number of organisms in the squares
- repeat the test and calculate a mean
- calculate the the total number of sundew by multiplying the mean number of sundews and the number of quadrat sections
Suggest and explain how digesting insects helps the sundew to grow in soil with very
low concentrations of some nutrients.
- digestion of protein provides amino acids
No bacteria were detected at any time in the flask that was inoculated with nutrient broth
that did not contain bacteria.
Explain the purpose of this flask.
- to act as a control
- to show that there is no contamination
The teacher told the students they should not investigate the growth of bacteria at 35°C.
Suggest why the teacher told them not to grow bacteria at 35°C.
- could encourage growth of human pathogen
The teacher also suggested that the students should have carried out the investigation
using three flasks at each temperature.
Explain how this suggestion would have improved the students’ investigation.
- reduces the impact of anomalies
- allows for a statistical test to be carried out (t - test)
- this would ensure a more accurate investigation
Testosterone is a steroid hormone that belongs to a group of male sex hormones
called androgens. Steroid hormones are hydrophobic. Explain why steroid hormones can rapidly enter a cell by passing through its cell-surface membrane.
- lipid soluble so diffuses through phospholipid bilayer
In the cytoplasm, testosterone binds to a specific androgen receptor (AR).
An AR is a protein. Suggest and explain why testosterone binds to a specific AR.
- it is complementary to the structure of AR
- has a specific tertiary structure
The binding of testosterone to an AR changes the shape of the AR. This AR molecule now enters the nucleus and stimulates gene expression. Suggest how the AR could stimulate gene expression.
- AR is a transcription factor
- binds to dna
- stimulates rna polymerase
For centuries, artificial selection has been used to improve the quality of crop plants used for
human consumption.
Explain, with reference to selective breeding, why it is important to maintain viable wild populations
of crop plant species.
- genetic variation
- gene bank
- source of useful alleles
- can be cross bred with crop variaties
- prevents inbreeding
- source of replacement if population is low
- prevents fall in gene pool
Each gamete contains only one allele of each gene. Describe how each gamete receives only one allele of each gene.
- homologous chromosomes are separated
- sister chromatids are separated
- spindle fibres pull the chromosomes to opposite sides of the poles
A scientist produced transgenic zebrafish.
She obtained a gene from silverside fish. The gene codes for a growth hormone (GH). She inserted copies of this GH gene into plasmids. She then microinjected these recombinant plasmids into fertilised egg cells of zebrafish. Describe how enzymes could be used to insert the GH gene into a plasmid.
- enzyme cuts plasmid
- ligase joins dna(gene) and plasmid
Microinjection of DNA into fertilised egg cells is a frequent method of producing
transgenic fish. However, the insertion of the transferred gene into nuclear DNA may be delayed. Consequently, the offspring of transgenic fish may not possess the desired characteristic. Suggest and explain how delayed insertion of the GH gene could produce offspring of
transgenic fish without the desired characteristic.
- cell division occurs before the gene is added
- cells producing the gametes dont recieve the genes
