Answer:
- <u>Conventional plastics-</u>
"Plastics are typically organic polymers of high molecular mass, but they often contain other substances."
"Oil-based polymers is currently used in packaging applications. These are virtually all non-biodegradable, and some are difficult to recycle or reuse due to being complex composites having varying levels of contamination.
- <u>Biodegradable plastics</u>-
"They are largely manufactured from renewable natural resources, to produce biodegradable materials with similar functionality to that of oil-based polymers."
Explanation:
<u>Complex Issue-</u>
- Diversity of biodegradable materials and their varying properties makes it difficult to make simple, generic assessments such as biodegradable products are all ‘good’ or petrochemical-based products are all ‘bad’.
- Biodegradable packaging materials are most suitable for single-use disposable applications where the post-consumer waste can be locally composted.
Answer:
The correct answer is D) short-lived plasma cells that secrete antibodies for the antigen
Explanation:
Each B lymphocyte has an antigen receptor (BCR: B cell receptor), a surface immunoglobulin (IgM or IgD), that binds to specific domains of the antigen called antigenic determinants or epitopes. Only B lymphocytes with a high antibody affinity for the antigen, and which are capable of processing and presenting it, will be positively selected. In this contact between the two cells, an exchange of chemical signals takes place that leads to the activation, clonal proliferation and differentiation of B cells into two sister subclones: one of antibody-secreting plasma cells, and the other of memory primed B cells. Therefore, only these last positively selected B lymphocytes will survive, proliferate and differentiate into plasma cells, synthesizing and secreting antibodies of a single isotypic class, with a unique specificity and high affinity, improving the ability to adhere to the antigen and, thus , neutralize and destroy pathogens.
