Plant Cell Structure and Function

Plant Cell Structure

• Plant cells are composed of protoplasm and a cell membrane
• Biologists identify two main cell types: Prokaryotic (simple, no nuclear envelope, found in single-celled and some simple multicellular organisms, and all bacteria) and Eukaryotic (have nuclear envelope and are found in most higher plants, algae, fungi, and animals).
• Plant cells contain cytoplasm, chloroplasts, lysosomes, ribosomes, mitochondria, vacuoles, peroxisomes, vesicles, rough endoplasmic reticulum, smooth endoplasmic reticulum, nucleoplasm, nucleolus, nuclear envelope, nuclear pore, cell wall, plasmodesmata, cell membrane, and Golgi apparatus, among other structures.

Plant Cell Wall

• Plant cells are distinct from animal cells due to the rigid cell wall which surrounds them.
• The cell wall is a rigid structure in mature plant cells, composed of cellulose microfibrils, polysaccharides, lignin, and other components like gums, resins, silica, calcium carbonate, waxes, and cutin.
• Plant cells have two types of cell walls:
  • Primary cell walls: thin and characteristic of young growing cells.
  • Secondary cell walls: thicker, stronger, and formed after cell enlargement stops, often reinforced by lignin.
• The symplast is the name of the continuous cytoplasm that is inside the cells

Cell Membranes

• Membranes play a crucial role in cell metabolism.
• Membranes divide the cell into compartments.
• Membranes regulate molecule passage.
• Heat, cold, poisons and alcohol can damage cell membranes.
• Membranes are primarily composed of fatty-acid lipids and proteins.
• Membrane proteins are classified into two types: intrinsic (firmly embedded) and extrinsic (loosely attached).
• Lipids, particularly phospholipids and sterols (like cholesterol), are essential components of membranes as they are amphiphilic (attract both water and lipid).

Cytoplasm and Cytosol

• The cytoplasm is the component of a cell surrounded by the membrane and houses all the organelles.
• The cytosol (the cytoplasm's inner, concentrated region) is where numerous cellular processes, like glycolysis, happen.
• The ectoplasm (the cytoplasm's outer region) surrounds organelles.
• All metabolic reactions occur in the cytosol.