Cell Biology Test - 7

Nucleus was discovered by Robert Brown in the roots of orchid.

Dujardin named protoplasm as sarcode and Flemming named mitochondria as fila. In eukaryotes, the protoplasm surrounding the cell nucleus is known as the cytoplasm and that inside the nucleus as the nucleoplasm. Mitochondria are rod-shaped organelles that can be considered the power generators of the cell, converting oxygen and nutrients into adenosine triphosphate (ATP). ATP is the chemical energy "currency" of the cell that powers the cell's metabolic activities.

When primary lysosome fuses with food carrying vacuole, heterophagosomes are formed. In heterophagosomes, digestion of engulfed food is done by hydrolytic enzymes.

In plants, the nuclear envelope functions as the main microtubule organising centre (MTOC) for microtubule nucleation and spindle organisation during plant cell mitosis.

Integral membrane proteins are integrated into the membrane. Some stick only partway into the membrane, while others stretch from one side of the membrane to the other and are exposed on either side. These are transmembrane proteins​.

In eukaryotic cells, 70S ribosomes are found in mitochondria and chloroplasts. Cytoplasm and endoplasmic reticulum of eukaryotes contain 80S ribosomes. Hence, eukaryotic cells have different kinds of ribosomes (70S and 80S), while prokaryotic cells just have 70S ribosomes.

Glyoxysomes have no enzymes for synthesis of nucleotides. They have enzymes for glyoxylate cycle, which is for synthesis of carbohydrates.
In glyoxysomes, fatty acids are hydrolysed to acetyl-CoA by peroxisomal β-oxidation enzymes. Thus, they contain enzymes for fatty acid metabolism. Glyoxysomes also contain catalase enzyme, which is required for metabolism of peroxides.

Oxysomes are found in the inner mitochondrial membrane. They play an important role in the formation of energy.

According to Loewy, a cell is a unit of biological activity surrounded by a permeable membrane and capable of self-replication in a medium free of other living systems.