ASVAB General Science: Cell Processes
Cells are the fundamental units of life, and they carry out a variety of essential processes that allow organisms to survive and thrive. Metabolism refers to all the chemical reactions that occur within a cell to sustain life. There are two main types of metabolic processes: anabolism, which builds up complex molecules like proteins, fats, and carbohydrates from simpler building blocks (requiring an input of energy), and catabolism, which breaks down complex molecules into simpler substances, often releasing energy in the process. The balance between anabolism and catabolism is crucial for maintaining homeostasis within the cell.
Osmosis is the spontaneous movement of water molecules across a selectively permeable membrane, from an area of higher water concentration to an area of lower water concentration. This helps regulate the water balance inside cells and prevent them from becoming overly swollen or shriveled.
Phagocytosis is a type of endocytosis where a cell engulfs and absorbs external materials, such as bacteria or cellular debris, by extending its cell membrane to surround the target and draw it into the cell interior. This allows cells to obtain nutrients and defend against pathogens.
Photosynthesis is the process by which plants, algae, and some bacteria use sunlight, water, and carbon dioxide to produce oxygen and energy-rich organic compounds like glucose. This is the primary source of energy for most of Earth's ecosystems.
Cellular respiration is the process by which cells break down glucose and other organic molecules to release the energy stored in their chemical bonds. This energy is then used to produce ATP, the universal energy currency of cells. There are three main stages of cellular respiration: glycolysis, the citric acid cycle, and the electron transport chain.