Plant Cell Structure and Protoplasm

Plant Cell Structure

• Plant cells are complex, containing various organelles
• Key organelles include: cell wall, cell membrane, endoplasmic reticulum, ribosomes, nucleus, nucleolus, vacuole, cytoplasm, golgi apparatus, golgi vesicles, mitochondria, and chloroplasts
• The cell wall provides support and structure
• The cell membrane controls what enters and leaves the cell
• Ribosomes are responsible for protein synthesis
• The nucleus contains the cell's genetic material
• The nucleolus is involved in ribosome production
• The vacuole maintains cell pressure
• The cytoplasm is the jelly-like substance filling the cell
• The golgi apparatus modifies and packages proteins
• Golgi vesicles transport proteins
• Mitochondria produce energy
• Chloroplasts carry out photosynthesis

The Protoplasm

• Protoplasm is the living substance of the cell (nucleus and cytoplasm)
• It is a colorless, jelly-like substance
• It contains food elements like proteins, fats, carbohydrates, minerals, and water

The Protoplasm (Colloidal System)

• Protoplasm is a colloidal complex with properties of a colloidal system
• Its colloidal properties are due to large, complex protein, carbohydrates, and fat molecules—which approach colloidal dimension
• The colloidal system is an essential aspect of living matter

Solutions

• Solutions are homogenous mixtures of molecules evenly distributed
• Everything in a solution is spread out and mixed evenly
• Heterogeneous mixtures have varying concentrations in different parts

Types of Solutions

• True solutions have solute particles smaller than 1 nm, stable, and remain evenly dispersed
  • Examples include salt or sucrose in water
  • Solute particles are individual molecules or ions
• Colloidal solutions have particles with sizes between 1 and 100 nm
  • They remain dispersed, forming a two-phase system (liquid dispersion phase and solid dispersed phase)
  • Colloidal particles are clumps or clusters of molecules
  • Examples include starch in water or egg albumin
  • Colloidal particles pass through filter paper but not semipermeable membranes
• Suspensions have particles larger than 100 nm
  • Particle sizes are large enough to be seen with a naked eye
  • They're unstable; the particles settle out over time, separating from the liquid layer
  • Examples include chalk in water

1- True Solutions

• Consist of a homogenous mixture of at least two components (solute dissolved in a solvent)
• Solute particles (size) are smaller than 1 nm
• The solute remains evenly dispersed and stable (doesn't settle)
• Example: sugar dissolved in water

1- True Solutions (Electrolytes and Non-electrolytes)

• Electrolytes: ionic substances that dissolve in water and conduct electricity (ex. salt)
• Non-electrolytes: non-ionic substances (ex. sucrose)

Water in Plant Cells

• Water is the major solvent in plant cells
• It's crucial for various cellular functions, including transporting nutrients, supporting metabolic reactions, contributing to cell turgidity, and aiding cell elongation

2- Suspension

• Suspension is a heterogeneous mixture where particles larger than 100 nm are dispersed in a liquid but not dissolved
• The particles are not separated into molecules but rather form aggregates of molecules that can be seen with the naked eye
• It's an unstable system; the particles gradually settle

3- Colloidal Solutions

• A heterogeneous mixture where particles (1–100 nm) remain dispersed throughout a medium in a stable manner
• Colloidal particles are clusters of molecules and are in the form of clusters of molecules
• Colloids easily pass through filter paper but not semipermeable membranes

Colloidal Properties of Particles

• Colloidal particles carry electric charges (positive or negative)
• The charge is consistent for a given system
• The charges are due to adsorption of free ions in the medium
• The preferential adsorption of positive ions leads to a positive charge for the particle

Types of Colloids

• Lyophilic colloids (Hydrophilic colloids): liquid-loving
  • Formed from dispersed particles surrounded by a water shell and electric charge
  • They are stable and not readily precipitated, easily precipitated by dehydration and neutralization
• Lyophobic colloids (Hydrophobic colloids): liquid-hating
  • Formed from dispersed particles surrounded only by an electric charge
  • They have similarly low surface tension and viscosity to the solvent
  • They are less stable and easily precipitated by neutral salts

Colloid Stabilizers

• Substances added to increase the stability of a colloid and prevent its precipitation
• Examples include gums and proteins
• Stabilizers form a protective layer around the colloidal particles