Biology of Respiration in Single-Celled Organisms

Study Notes

Respiration involves acquiring oxygen from the environment and using it for cellular energy through oxidation-reduction reactions.
Single-celled organisms can utilize simple diffusion for oxygen and nutrient exchange due to direct environmental contact.
Multi-cellular organisms require specialized tissues for nutrient and oxygen uptake as not all cells have direct access to the environment.
A transportation system is necessary in complex organisms to distribute food and oxygen to all cells.

Amoeba uses finger-like extensions to engulf food, forming a food vacuole, where digestion occurs before expelling waste.
Paramecium has a defined shape with cilia to guide food to a specific ingestion site.

The alimentary canal is a long tube with specialized regions for food processing from the mouth to the anus.
Bile from the liver neutralizes stomach acid and emulsifies fats, making them easier for enzymes to digest.
Pancreatic juice contains enzymes like trypsin and lipase for protein and fat digestion, respectively.
The small intestine's inner lining has villi, which increase surface area for nutrient absorption.

Organisms metabolize glucose via aerobic respiration (using oxygen) producing carbon dioxide and water, or anaerobic respiration (without oxygen) producing ethanol, carbon dioxide, or lactic acid.
Aerobic respiration occurs in mitochondria, yielding more energy compared to anaerobic processes.
Lactic acid build-up in muscles can cause cramps during intense activity due to low oxygen levels.

The heart is a muscular organ with multiple chambers, preventing mixing of oxygen-rich and carbon dioxide-rich blood.
Deoxygenated blood is sent to the lungs for carbon dioxide removal while oxygenated blood returns to the heart and is pumped to the rest of the body.
Efficient circulation is essential for transporting nutrients, oxygen, and removing waste products from cells.