Summary HISTOLOGY (CELL STRUCTURE) - GRADE 10 IEB LIFE SCIENCE

The Cell
 Smallest unit of life.
 Organelle (Cell Inclusions) – Membrane-bound structure found cytoplasm &
performs a certain function.
 Eukaryote – Has nucleus
 Prokaryote – Doesn’t have nucleus.
 Differentiation
 Size, shape and structure change in order to perform specific functions.
 Specialisation
 Cells that have developed characteristics in order to perform a particular function.
 Muscle Cells
 Glandular Cells
 Nerve Cells

Protoplasm
 Cytoplasm + Nucleus
 Endoplasm (Ground Plasm) – Centre
 Ectoplasm – Bordering Cell Membrane

Chemical Composition
Inorganic Compounds
 Lacks C-H bonds & isn’t produced in cell.

 Water
 Main component (≤90%)
 Serves as solvent median + reagent in chemical reactions.

 Gases – Oxygen & Carbon Dioxide dissolve in ground plasma.

 Mineral Salts – Sodium Chloride, Phosphates + Potassium ions.


Organic Compounds
 Contains Hydrocarbons & produced in cell.

 Proteins – Important structural component of membrane, enzymes & some
hormones.

 Carbohydrates – Sugars & Starch (energy)

 Lipids – Part of cell membranes, stored as reserve energy.

 Nucleic Acids – RNA & DNA
Physical Nature of Protoplasm

, NOT EXAMINABLE
 Solvent – Liquid in which substance is dissolved (water in biological systems).
 Solute – Particles/substance being dissolved.
 Solution – Solvent + Solutes




Type Explanation Diagram
True Solution  Homogenous Salt
 Salts, sugars, gases dissolved
in water
Water



Suspension  Heterogeneous
 Organelles floating in ground
plasm



Emulsion  Solvent & solute both liquid




Colloidal Solution  Solute too big to sink but too
small to sink.
 Ionized ∴ repel




Aggregate  Particles remain in suspension
and form strings/clumps.
 Hold water between particles.
 States:
 Sol – Endoplasm
(Ground plasm)
 Gel – Ectoplasm
 Reversible
through:
Temperature,
Pressure, pH