BTEC Applied Science Unit 1 Biology: Prokaryotes and Prokaryotic Cells

Introduction to Cells

Types of Cells
- Eukaryotic Cells: Found in plants and animals; contain nucleus and membrane-bound organelles.
- Prokaryotic Cells: Single-celled organisms without a nucleus; primarily bacteria.

Nucleoid
- Not a true nucleus but a single circular DNA molecule.
- Not enclosed by a membrane.
Ribosomes
- Float freely in the cytoplasm.
- Smaller (70S) than those in eukaryotic cells (80S).
Slime Capsule
- Outer protective layer.
- Helps prevent desiccation and provides defense against white blood cells.
- Aids in adhesion to surfaces.
Cell Wall
- Made of peptidoglycan (sugars and amino acids).
- Provides structural support and shape.
Plasmids
- Circular DNA structures within the cell.
- Contain additional genes for survival, like antibiotic resistance.

Composition
- Bacterial cell walls consist of long chains of sugars and amino acids.
Gram Test
- Differentiates bacteria into gram-positive and gram-negative based on cell wall properties.

Gram-Positive Bacteria
- Thick peptidoglycan cell wall.
- Absorb stain during gram test, turning purple.
- Lack an outer membrane.
Gram-Negative Bacteria
- Thin cell wall with an outer membrane.
- Do not retain stain during gram test.
- More resistant to antibiotics due to additional protective layers.

What are bacterial cell walls made from? (Answer: Peptidoglycan)
Why are some bacteria gram-positive and others gram-negative?
What structural differences exist between gram-positive and gram-negative bacteria?
Why is it crucial for doctors to distinguish between these types?
Note: Refer to diagrams illustrating the differences between gram-positive and gram-negative bacteria and the flagella aiding bacterial movement.