Lysosome helps in waste disposal of the cell. It breaks down unnecessary substances.

Ribosomes are made of RNA and protein. It is the site of protein synthesis in the cell.

Krebs Cycle: After glycolysis, the glucose molecule breaks down into two pyruvic molecules, which are oxidized in the form of a cyclic path by various respiratory enzymes present in the matrix, which is called the Krebs cycle.

Note: The answer given in the book is (3), which appears scientifically incorrect as Lysosomes are single-membrane organelles. In fact, the Nucleus, Mitochondria, and Chloroplast all possess a double membrane.

Cell cycle - The processes occurring from the formation of a cell to its re-division to form daughter cells is called the cell cycle. It is divided into three parts . Histone protein synthesis occurs during the S-phase.

Under the process of photosynthesis, trees absorb carbon dioxide and release oxygen, therefore it does not release $CO_2$.

Plant breeding is a purposeful manipulation of plant species so that desired plant varieties can be prepared. These varieties are more useful for farming, high yielding, and disease resistant.

The cellular organelle (Nucleus) was discovered by Robert Brown in 1831.

Light reaction takes place in the grana of the plastid, and dark reaction takes place in the stroma.

Camillo Golgi (1898) first observed dense reticular structures near the nucleus. Golgi stacks are organized concentrically near the nucleus, having a forming surface (cis) and a mature surface (trans).

The main organelles that separate plant cells from animal cells are the cell wall, plastids, and large vacuoles. Cell wall and plastids are present in plant cells, whereas animal cells have many small vacuoles. Endoplasmic reticulum and cell membrane are found in both plant and animal cells.

Photosynthesis is a reduction reaction in which $CO_2$ is reduced to carbohydrate.

The process of photosynthesis only occurs in the presence of sunlight.

In a hypotonic medium, the cell swells due to endosmosis, the cell wall prevents it from bursting.

Two processes of gaseous exchange in plant leaves continue constantly. The first is respiration, which is similar to other living organisms, continues 24 hours, where plants use oxygen and release carbon dioxide. The second process is food production, i.e., photosynthesis, in which carbon dioxide is used and oxygen is released.

See explanation of the above question.

Ribosomes are made of ribonucleic acid and protein and are not surrounded by any membrane. Eukaryotic ribosomes are $80S$ and prokaryotic ribosomes are of the $70S$ type.

Due to insufficient sunlight during twilight, photosynthesis may slow down or stop. Hence, plants do not release any gas at this time.

Oxygen is a by-product of photosynthesis, not a necessary reactant.

The first cells were discovered in 1665 by Robert Hooke in cork/phloem (a part of tree bark). It was called 'cellula'. Robert Hooke is known as the father of cell biology. Carl P. Swanson is known as the father of modern cell biology.