Plant Cell Structure and Function

Plant Cell Structure and Function

• Plant cells are composed of protoplasm and a cell membrane
• Biologists identify two main cell types: prokaryotic (simple, no nucleus) and eukaryotic (with a nucleus)
• Plant cells are eukaryotic, containing a nucleus and other organelles
• Plant cells have a rigid cell wall primarily composed of cellulose microfibrils, polysaccharides, and lignin.
• The cell wall provides structural support and prevents excessive water uptake
• Secondary cell walls are thicker and stronger than primary walls, contributing to the strength and toughness.
• Lignin is a key component of secondary cell walls.
• Plasma membrane is a semi-permeable barrier surrounding the cytoplasm
• The membrane is primarily composed of lipids (fatty acids) and proteins
• There are two types of membrane proteins: extrinsic (loosely attached) and intrinsic (firmly embedded)
• Membrane lipids are phospholipids and sterols (like cholesterol)
• The membranes have an amphiphilic property, meaning they can interact with both water and fat
• Membranes are actively involved in metabolism and contain a higher proportion of protein
• Membranes perform critical tasks, such as dividing the cell into compartments and regulating molecule passage.
• Membranes can grow and fuse
• The cell wall helps maintain cell shape and prevents overexpansion

Plant Cell Components

• Cell Wall: Provides structural support and protection, and prevents the plant cell from rupturing. Primarily composed of cellulose.
• Cytoplasm: Contains all organelles and the jelly-like cytosol.
• Chloroplasts: Site of photosynthesis; contain chlorophyll for capturing light energy.
• Vacuoles: Fluid-filled sacs that store water, nutrients, and waste products, and helps maintain turgor pressure.
• Mitochondria: Site of cellular respiration, generating energy (ATP).
• Lysosomes: Involved in the breakdown and recycling of cellular waste materials. Peroxisomes break down fatty acids and other molecules.
• Endoplasmic Reticulum (ER): Rough ER (with ribosomes) processes proteins; Smooth ER (without ribosomes) synthesizes lipids.
• Golgi Apparatus: Processes and packages proteins and lipids.
• Nucleus: Contains the cell's genetic material (DNA), controls cellular activities
• Ribosomes: Involved in protein synthesis.

Cell Wall Details

• Plant cells have a rigid cell wall that differs from animal cells
• Two types of walls:
  • Primary Cell Walls: Thin, characteristic of young growing cells
  • Secondary Cell Walls: Thicker, stronger, formed when cell growth has ended
• Cell walls are critical for plant development and their ability to grow vertically.
• Cell wall cementing prevents migration of cells
• Cell walls play a role in cell division, expansion and in communication amongst plant cells.

Cytoplasm and Cytosol

• Cytoplasm includes the cytosol (the fluid component) and all the organelles
• The inner part called endoplasm
• The outer part called ectoplasm
• Cytosol is the matrix for all metabolic reactions of the cell.