Consider statements about cell biology: 1. The plasma membrane is composed of a phospholipid bilayer. 2. The nucleus contains the cell's genetic material. 3. Mitochondria are the site of photosynthesis. Which are correct? MCQ with Answer and Explanation

Explanation:
The poly-A tail is a long chain of adenine nucleotides (typically 100-250) added to the 3' end of a pre-mRNA molecule during post-transcriptional processing in the nucleus. Its primary functions are to protect the mRNA molecule from enzymatic degradation in the cytoplasm (by exonucleases), to facilitate the export of the mature mRNA from the nucleus to the cytoplasm, and to promote translation by helping to recruit ribosomes. It also plays a role in determining the lifespan of the mRNA in the cytoplasm.

Explanation:
Carolus Linnaeus, a Swedish botanist, introduced the binomial nomenclature system in his book 'Species Plantarum' (1753). This system assigns a two-part scientific name—genus and species—to every organism. For example, Homo sapiens. Darwin proposed natural selection, Hooke discovered cells, and Mendel laid the foundation of genetics. Linnaeus is also known as the father of taxonomy. Binomial names are universally accepted and italicized in print.

Explanation:
Approximately 97% of O₂ is transported bound to hemoglobin (as oxyhemoglobin), while only 3% is dissolved in plasma. Each hemoglobin molecule can bind four O₂ molecules cooperatively. CO₂ is mainly transported as bicarbonate (70%), carbaminohemoglobin (23%), and dissolved (7%). The affinity of hemoglobin for O₂ is influenced by pH, CO₂, and temperature (Bohr effect).