Exchange surfaces and a transport system are essential in multicellular organisms to ensure that there is a large surface area to volume ratio. This allows for the efficient exchange of materials. The small intestine and lungs in mammals, gills in fish, and the roots and leaves in plants are all examples of structures adapted for exchanging materials.
Specialization for Exchange
Surfaces and organ systems in multicellular organisms are specialized for the purpose of exchanging materials. This is necessary to ensure that enough molecules can be transported into and out of cells to meet the organism's needs. Gas and solute exchange surfaces in humans and other organisms are specifically adapted to maximize their effectiveness. As the size and complexity of an organism increase, so does the difficulty of exchanging materials.
Factors That Increase Effectiveness
The effectiveness of an exchange surface can be increased by having a large surface area, being thin to provide a short diffusion path, having an efficient blood supply (in animals), and being ventilated (in animals, for gaseous exchange).
Osmosis
Dissolved substances move by diffusion and active transport, and water often moves across boundaries by osmosis, which is the diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane. Differences in the concentrations of solutions inside and outside a cell cause water to move into or out of the cell by osmosis.
Examples of Osmosis
Active transport allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil, and sugar molecules to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration. This process is essential for healthy growth and cell respiration.
Active Transport
Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient) and requires energy from respiration. This process enables cells to absorb substances from very dilute solutions.
Principles of Organization
The human digestive system provides the body with nutrients and the respiratory system provides it with oxygen while removing carbon dioxide. These systems provide dissolved materials that need to be transported quickly around the body in the blood by the circulatory system. Any damage to these systems can be debilitating or fatal, emphasizing the importance of maintaining a healthy diet and lifestyle.
Basic Concepts
- Cells are the basic building blocks of all living organisms.
- A tissue is a group of cells with a similar structure and function.
- Organs are aggregations of tissues performing specific functions.
- Organs are organized into organ systems, which work together to form organisms.
- The plant's transport system depends on environmental conditions to ensure the provision of water and carbon dioxide needed for photosynthesis in leaf cells.
Animal Tissues, Organs, and Organ Systems
Large multicellular organisms develop systems for exchanging materials, and during their development, cells differentiate to perform different functions. Examples of tissues include muscular tissue, glandular tissue, and epithelial tissue. Organs are made up of different tissues, and the digestive system is an example of an organ system in which several organs work together to digest and absorb food.
Enzymes
Enzymes are catalysts that increase the rate of chemical reactions. They are responsible for various metabolic reactions within our bodies. Enzymes have specific pH values at which they work best, and high temperatures can change the shape of their active site, denaturing the enzymes. Some enzymes work outside the body cells, and digestive enzymes are produced by specialized cells in glands and in the lining of the gut, playing a crucial role in the process of digestion.
