Cellular Biology: Prokaryotes, Eukaryotes, and Respiration
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Prokaryotes and Eukaryotes
Prokaryotes are small, simple cells with their genetic material dispersed throughout the cytoplasm. Eukaryotes are larger, more complex cells with their genetic material contained within a structure called the nucleus, separated from the cytoplasm by a membrane called the nuclear membrane.
- Animal Cell: Found in protozoa and animals.
- Plant Cell: Found in algae and plants.
Photosynthesis
Photosynthesis is the process by which organisms synthesize energy-rich organic molecules, such as glucose, from inorganic substances lacking energy. Sunlight provides the necessary energy. Photosynthesis occurs in leaves and green stems and takes place within chloroplasts.
Formula: H2O + CO2 + sunlight = Mineral salts = Glucose + O2
Cellular Respiration
Once oxygen and other nutrients enter the cells, catabolism occurs. The most important catabolic reaction is cellular respiration, which essentially consists of the degradation of organic molecules. Oxygen is necessary for aerobic cellular respiration. The energy stored in the bonds of organic molecules is transformed into high-energy molecules, such as ATP, during respiration. This process takes place in the mitochondria.
The Circulatory System
The circulatory system is divided into the cardiovascular system, which circulates blood, and the lymphatic system, which circulates lymph. It is formed by the heart and blood vessels. Arteries carry blood from the heart to various organs, while veins carry blood back to the heart. Capillaries facilitate the exchange of substances with cells.
The circulatory system can be either open or closed. In an open system, blood leaves the blood vessels, while in a closed system, it does not.
Types of Closed Circulatory Systems
- Simple: Blood passes through the heart only once. It then goes to the gills to be oxygenated, then to the tissues, and finally returns to the heart.
- Double: Blood passes through the heart twice.
- Pulmonary Circulation: Blood travels from the heart to the lungs to receive oxygen and then returns to the heart.
- Systemic Circulation: Blood travels from the heart to the rest of the body.
Types of Double Circulatory Systems
- Incomplete: Arterial blood mixes with venous blood in the heart. Found in amphibians and some reptiles.
- Complete: Arterial blood does not mix with venous blood in the heart. Found in birds and mammals.