Medicine Semester 1: Cell Structure Quiz

Medicine (Semester 1) - Foundations of Normal Human Structure (BMS111) - Cell Structure (1)

• Objectives:
  • Demonstrate the structure of the cell membrane.
  • Determine the functions of the cell membrane and cell coat.
  • Recognize the classification of cell organelles.
  • Demonstrate routine histology staining methods.
  • Determine the structure and functions of mitochondria.
  • Recognize the structure, types, and functions of ribosomes.

Cell Structure

• Components:
  • Cell membrane
  • Nucleus
  • Cytoplasm
    • Membranous organelles (e.g., mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes)
    • Non-membranous organelles (e.g., ribosomes)
    • Cytoskeleton
    • Cell inclusions

Cell Membrane

• Description: The outer limiting membrane surrounding the cell. Also known as the plasma membrane or plasmalemma.
• Thickness: 7.5-10 nm, visible only by electron microscopy (EM).
• EM Appearance: Trilaminar appearance with two electron-dense lines (black) separated by an electron-lucent line (white).

Molecular Structure of Cell Membrane

• Components:
  • Lipids (phospholipids, cholesterol)
  • Proteins (integral, peripheral)
  • Carbohydrates (glycolipids, glycoproteins)

Phospholipids

• Structure: Composed of a hydrophilic head (water-attracting) and a hydrophobic tail (water-repelling).
• Arrangement: Organized into a double layer (bilayer) with hydrophobic tails facing inward and hydrophilic heads facing outward.

Cholesterol

• Location: Between phospholipid molecules.
• Function: Regulates the fluidity and stabilizes the phospholipid bilayer.

Proteins (Cell Membrane)

• Integral Proteins: Firmly embedded in the lipid bilayer, difficult to extract. Many are transmembrane proteins spanning the entire bilayer.
• Peripheral Proteins: Loosely attached to the outer or inner surfaces, easily extracted.

Carbohydrates (Cell Membrane)

• Glycolipids and Glycoproteins: Project from the external surface of the membrane, forming the cell coat or glycocalyx.

Functions of Cell Membrane

• Exchange of Materials:
  • Passive diffusion (for gases and ions).
  • Active transport (for amino acids, glucose, fatty acids).
  • Selective transport (for hormones, drugs, bacteria).
• Endocytosis: Cell taking in substances.
  • Phagocytosis (for solid particles).
  • Pinocytosis (for fluids).
  • Receptor-mediated endocytosis (for large molecules).
• Exocytosis: Cell expelling substances.

Mitochondria

• Definition: Membranous organelles specialized for energy production (ATP).
• Size and Shape: Vary in size and shape (elongated, rod-shaped, spherical).
• Number: Highly variable depending on cell activity (e.g., liver cells have many, lymphocytes have few).
• Location: Mobile, located where energy needs are high (e.g., between myofibrils in cardiac muscle).
• Structure: Double membrane, inner membrane with cristae (folds), intermembrane space, matrix (contains mitochondrial DNA and ribosomes).

Ribosomes

• Definition: Non-membranous organelles; protein factories of the cell.
• Size: Very small (20-30 nm in diameter).
• Light Microscopy (LM): Individual ribosomes are too small to be seen. Clusters lead to cytoplasm basophilia (due to rRNA).
• Electron Microscopy (EM): Appear as small electron-dense particles, composed of two subunits (small and large) formed of rRNA & proteins.
• Types:
  • Free ribosomes/Polyribosomes/Polysomes: Synthesize proteins for use within the cell (cytosol and cytoskeleton).
  • Attached ribosomes/Rough Endoplasmic Reticulum (RER): Synthesize proteins for secretion outside the cell, or remaining as primary lysosomes.

Staining (Hematoxylin and Eosin)

• Hematoxylin (H): Basic dye, stains acidic structures (DNA in nucleus) basophilic.
• Eosin (E): Acidic dye, stains basic structures (mitochondria) acidophilic.

Test your knowledge on the fundamentals of cell structure for the BMS111 course in Medicine. This quiz covers the components of the cell, including the cell membrane, organelles, and histology techniques. Get ready to demonstrate your understanding of cell functions and classification!