Plant Cells and Their Structures

Study Notes

Plant Cells are bounded by a cell wall surrounding the protoplasm.
The plasma membrane bounds the living components of the cell.
Cytoplasm is the space between the plasma membrane and nucleus.
The cytosol is a soup-like fluid containing various organelles.
Organelles are specialized structures with specific functions, mostly membrane-bound.

Primarily composed of cellulose, hemicellulose, pectin, glycoproteins, and lignin.
Functions as structural support and protection of the cell's contents.
Pectin forms the middle lamella between newly formed cell walls.
Lignin is a complex polymer embedded in secondary cell walls, increasing rigidity and strength.

Stores DNA which carries the genetic information of the cell.
Genetic information governs cell growth, differentiation, and cellular activities.
Nuclear pores regulate the movement of molecules between the nucleus and cytoplasm.
Chromatin is composed of DNA and proteins.
Chromosomes form when chromatin coils during cell division.

Plant cells are enclosed by a cell wall that surrounds the protoplasm, which contains all the living components of a cell.
These living components are bound by a membrane called the plasma membrane.
All cellular components located between the plasma membrane and nucleus are known as cytoplasm.
Cytoplasm contains a fluid called cytosol, in which various bodies called organelles are dispersed.
Organelles are persistent structures of various shapes and sizes with specialized functions in the cell; most, but not all, are bounded by membranes.

The cell wall is the outermost layer of a plant cell and is composed of :
- Cellulose (main structural component)
- Hemicellulose
- Pectin
- Glycoproteins
- Lignin
The cell wall provides structural support and protection to the delicate cell contents within.
Additionally, cell walls contain a matrix of hemicellulose, pectin, and glycoproteins.
A middle lamella, composed of a layer of pectin, initially forms during the formation of new cell walls.
The cell wall undergoes reorganization, synthesis of new molecules, and insertion of new polymers as the cell grows.
Secondary walls, which are produced inside the primary walls, are derived from primary walls by thickening and inclusion of lignin.
Generally, secondary cell walls have a higher cellulose content (40% to 80%) compared to primary walls.

The plasma membrane is the outer boundary of the living part of the cell.
Similar to other cell membranes, the plasma membrane is composed of phospholipids arranged in two layers with proteins dispersed throughout.
The plasma membrane's primary function is to regulate the movement of substances in and out of the cell.
It is also involved in the production and assembly of cellulose for cell walls.

The nucleus is the storehouse of genetic material in the form of DNA.
Its function is to store genetic information that contributes to growth, differentiation, and cellular activities.
The nuclear envelope, a double membrane surrounding the nucleus, contains pores that act as channels for molecules.
These pores allow only certain kinds of molecules to pass between the nucleus and the cytoplasm.
Chromatin, composed of protein and DNA, is found within the nucleus.
During cell division, chromatin strands coil becoming shorter and thicker, transitioning into chromosomes.

The endoplasmic reticulum (ER) is a network of interconnected membranes that extend throughout the cytoplasm.
It is involved in the synthesis and transportation of lipids and proteins.
The ER can either be rough or smooth, depending on the presence or absence of ribosomes.
Rough ER is studded with ribosomes and primarily involved in protein synthesis.
Smooth ER lacks ribosomes and is involved in lipid synthesis and detoxification.
The ER also aids in the production of steroid hormones and plays a role in calcium storage.

Ribosomes are small organelles found throughout the cytoplasm, typically measuring 20 nanometers in diameter.
Each ribosome consists of two subunits, composed of RNA and proteins.
Their primary function is protein synthesis, where they link amino acids together.
They translate the genetic code carried by messenger RNA (mRNA) into proteins.