الفسيولوجيا العامة للنباتات I

Course Information

• Course title: General Botany I, Physiology
• Prepared by: Prof. assist Dr. Zeinab Ashour

What is Plant Physiology?

• The study of the function of plant cells, tissues, and organs, and the chemistry of these functions.
• Crucially, these functions depend on structures.

Plant Parts

• Diagram showing: flower, leaf, fruit, stem, and root.

Plant Tissue Systems

• Diagram illustrating plant tissue systems: leaf anatomy, internal stem structure, and internal root structure.

Plant Cell Diagram

• Diagram showing: chloroplast, nucleolus, ribosomes, large central vacuole, mitochondrion, and cell membrane.

Course Outline

• Key topics: Diffusion, osmosis, permeability, plasma membrane, colloids in plants, cytoplasm, photosynthesis, chloroplast, respiration, mitochondria, enzymes, and all compartments.

Evaluation

• 10 marks for midterm exam
• 15 marks for oral exam and assignments
• 20 marks for practical exam
• 60 marks for final written exam

Plasma Membrane

• The outer boundary of all cells.
• Separates the cytoplasm from the external environment.
• Allows the cell to take up or retain specific substances while excluding others.
• Contains transport proteins responsible for selective transport of solutes.

Biological Membranes

• All biological membranes share a basic structure: a phospholipid bilayer with proteins interspersed.
• Phospholipid structure:
  • Two fatty acid tails (nonpolar).
  • A phosphate group and attached molecule (polar head).
• The arrangement creates a hydrophobic interior (excluding water) and a hydrophilic exterior.

Proteins Associated with Membranes

• Two types: integral and peripheral proteins.
• Integral proteins: embedded in the lipid bilayer, interacting with outside, hydrophobic core, and inside of the cell.
• Peripheral proteins: attached to the membrane surface by non-covalent bonds, play roles in interactions between the plasma membrane and the cytoskeleton.

Permeability to Substances

• How plasma membranes control permeability:
  • Selective permeability: allowing the passage of certain substances while preventing others.
• Permeability to non-ionized substances:
  • Usually diffuse across the membrane through a process called diffusion.
  • Driving force is the kinetic energy of the particles.
  • Movement is from high concentration to low concentration. Diffusion continues in both directions at equal rates after equilibrium is reached.
• Size and solubility influence diffusion:
  • Small and non-polar substances diffuse easily.
  • Large substances require assistance (passive facilitated diffusion) from membrane proteins like channels or carriers.
  • Substances with high affinity for oil penetrate lipid membranes rapidly.
• Permeability to ionic substances:
  • Ions move much slower than non-ionized substances.
  • Cells continue to absorb ions even if internal concentration is higher than external, suggesting active transport is involved.

Active Transport

• Movement of substances against a concentration gradient (from dilute to concentrated).
• Requires metabolic energy.
• Involves transmembrane proteins (pumps).
• Essential for accumulating ions or molecules within the cell.

Selective Uptake of Ions

• Living cells can distinguish between different ions.
• Monovalent cations (like K+) are absorbed faster than polyvalent cations (like Ca²⁺).
• Even ions with the same valence may be preferred differently.