Plant Physiology - Lecture Notes - O. M. Tarnopilska 2019

2. Structural Components of the Plant Cell
2.8 Biochemical Composition of the Plant Organism

Numerous studies have revealed A wide variety of Organic compounds in plants. The Water content in plant protoplasm ranges from 75 to 90%, while The Cell sap of the vacuole contains up to 98% water. The structural foundation of plant protoplasm consists of protein substances and their derivatives, which account for 2/3 of the dry matter. Many protoplasmic Proteins are bound to other organic compounds, forming Lipoproteins, Nucleoproteins, Glycoproteins, and Chromoproteins. Dry matter components such as Lipids, phosphatides, and plant sterols make up about 1/5 of the total mass.

According to modern data, organelle chemical composition varies significantly. For instance, isolated nuclei of plant Cells contain 75–80% proteins by dry weight, along with approximately 14% DNA and 10% RNA.

Mitochondria are characterized by a low nucleic acid content (about 0.5% of dry matter) and a high lipid content (25–30%). Protein content in these Organelles ranges from 35 to 40%. Plastids are even richer in lipids (up to 40% of dry mass), containing about 50% proteins and 5% Nucleic Acids.

In terms of chemical composition, Ribosomes are nucleoproteins in which proteins and RNA each account for approximately 50%.

The plant cell wall is composed primarily of CARBOHYDRATES.

Elemental analysis of The chemical composition of plants shows that carbon, oxygen, hydrogen, and nitrogen are their primary constituents. The average Elemental Composition of plant dry matter, without organ-specific differentiation, is as follows: C – 45%, O – 42%, H – 6.5%, N – 1.5%, ash – 5%.