Cell Biology and Structure

Plasma membrane pores typically measure around 8 Ångströms, allowing small molecules and ions to pass while restricting larger molecules. This size is crucial for selective permeability and controlling molecular transport across membranes.

This is the correct option. ATP is synthesised by the cell in mitochondria and chloroplast.

Meristematic tissues contain undifferentiated cells with active division capabilities, enabling plant growth at root and shoot tips. These cells remain in a perpetual state of mitotic potential, allowing continuous plant development.

Tissue cells share embryological origin, similar structural characteristics, and perform collective specialized functions. This organizational principle enables complex organisms to develop specialized tissues with precise cellular arrangements supporting specific physiological roles.

Muscular tissue demands significant energy due to continuous contraction and relaxation processes. Even at rest, muscles maintain basal metabolic tone, actively consuming ATP through complex biochemical pathways for movement and posture maintenance.

Tissues are defined as groups of cells with similar structural characteristics and coordinated functional properties. This fundamental biological principle allows multicellular organisms to organize cells into specialized units performing specific physiological tasks.

Ribosomes are the cellular structures where protein synthesis occurs. They read mRNA and assemble amino acids into protein chains. Lysosomes break down waste materials. Mitochondria produce energy (ATP). Endoplasmic reticulum modifies proteins but the actual synthesis happens at ribosomes (which can be free or attached to the ER).

Animal cells contain lysosomes for waste digestion and centrosomes for organizing cell division, which are generally absent in plant cells. Both cell types share mitochondria for energy production and ribosomes for protein synthesis.

Proteins are the most abundant organic molecules in cytoplasm, serving as enzymes that catalyze reactions and as structural components. While water is the major component overall, it's inorganic, and lipids and sugars are present in smaller amounts than proteins.

Protoplasm encompasses all living parts of the cell: the plasma membrane, cytoplasm, and nucleus. The cell wall is an extracellular structure in plants, fungi, and bacteria and is not considered part of the protoplasm.

Animal cells lack cell walls, which are rigid outer structures found in plant cells (made of cellulose), fungal cells (chitin), and bacterial cells (peptidoglycan). This allows animal cells to be more flexible and change shape.

Eukaryotic cells have a true nucleus surrounded by a double membrane and membrane-bound organelles like mitochondria and ER. Prokaryotic cells lack these features, and unicellular refers to number of cells, not cell type.

Cytoplasm is a jelly-like substance which is present all around the nucleus in which cell organelles are placed. Cell membrane is the outer covering of a cell that separates the interior of all cells from the outside environment. Nuclear membrane is the membrane, which surrounds the central nucleus. Nucleoplasm is a jelly-like substance present in the nucleus.