Unit 3 Flashcards
(16 cards)
Explain how a weak cell wall can cause a bacterium to explode?
The bacterium takes up water by osmosis and increases in volume (1). The swelling is not limited by the cell wall so the cell membrane ruptures (1).
Give a biological explanation as to why reduced protein synthesis may lead to cell death.
Proteins have specific functions within the cell (enzyme, membrane protein etc.) (1) and if these are not synthesised properly it may disrupt metabolism (enzymes) or movement (1).
How would an individual’s immune system react to a second exposure of a particular pathogen?
Memory cells recognise antigens on the virus (1) and clone into plasma cells (1) that
produce large quantities of antibodies (1). This leads to the eradication of the virus.
Explain why there is a risk of organ rejection is all 5 of the tested HLA proteins are a perfect match.
There are only 5 factors used to determine compatibility, so other antigens may exist in the transplanted tissue that were not accounted for when determining compatibility (1) thus there
is a risk of rejection as the immune system will be stimulated to act against the other antigens (1).
Antibiotics are effective against bacteria, but not viruses because…?
Effective against bacteria because they disrupt various aspects of their metabolism with minimal side effects. Ineffective against viral diseases because a virus does not metabolise. Viruses hijack cells and generate more viruses within them until they literally burst.
Select the correct statement regarding cytokines.
a) are hydrophobic hormones
b) produced by a cell, can diffuse to a nearby target cell
c) cross a synapse by moving down a concentration gradient
d) secreted by an animal then released into the air
b) is true
cytokines are produced by a cell and can diffuse to a nearby target cell
What two major events occur in lymph organs such as lymph nodes, spleen and tonsils?
Clonal selection and expansion.
Explain how the expression of a single gene can lead to the production of different proteins.
- different post-transcriptional modification
- different exons are joined through alternative splicing
- results in different nucleotide sequences/mRNA sequences, coding for a different protein
Describe the effect of decreasing the concentration of a molecule that acts as an inhibitor for a particular enzyme.
- low levels of inhibitor mean less competition for the active site
- more substrate is able to bind, increasing substrate concentration
Describe the role of these immune cells.
a) lysozyme
b) complement proteins
c) cytokines
d) venom inhibitors
a) lysozyme – breaks open bacterial cells
b) complement proteins – for example, stimulate phagocytes
c) cytokines – control/stimulate other immune cells
d) venom inhibitors – would lock onto snake/spider venom molecules and prevent them from
reacting
Describe how antibodies perform their function against pathogens?
Antibodies have shape specific to the antigen.
Can mark pathogens so that macrophages/ other immune cells can engulf/destroy it.
The evidence that would NOT support symbiogenesis is
A. If mitochondria and chloroplasts are removed from a cell, the cells cannot replicate
new ones.
B. Mitochondria and chloroplasts contain single circular DNA that is identical to
nuclear DNA.
C. Transport proteins called porins, found in the outer membranes of mitochondria and
chloroplasts, are also found in bacterial cell membrane.
D. New mitochondria and plastids are formed only through a process similar to binary
A is incorrect because the fact that cells cannot create new mitochondria and chloroplasts if
they are removed supports symbiogenesis.
B is correct because nuclear DNA occurs in the form of multiple linear chromosomes, not a
single circular chromosome.
C is incorrect because the fact that mitochondria, chloroplasts and bacteria all have transport
porins support symbiogenesis.
D is incorrect because the fact that the formation of new organelles occurs through a process
that is similar to binary fission supports symbiogenesis.
Define pheromone.
Pheromones are signalling molecules released externally that can only be detected by members of the same species.
It is detected intraspecifically.
Which of the following is involved in the first line of defence in animals? A. insulin B. acetylcholine C. lysozyme D. lysosome
C. lysozyme
lysozyme is a first line defence chemical.
D is incorrect – a lysosome is an organelle involved in the breakdown of unwanted substances in
a cell.
When a hydrophilic signalling molecule reaches a target cell, which sequence of steps occurs?
Binding to protein receptor on cell surface, transduction, response.
When apoptosis is intiated by DNA damage in a cell, what occurs?
A cascade of reactions occur in the cytoplasm.
