1: Root cells obtain energy through the process of cellular respiration, where they break down glucose to produce ATP. This process occurs in the mitochondria, which are organelles found in all eukaryotic cells, including plant cells. Roots lack chloroplasts because they are underground and do not receive adequate sunlight for photosynthesis to occur.
2: Animal cells do not require a cell wall because they do not need the rigid structure and support that a cell wall provides in plant cells. Instead, animal cells rely on intercellular junctions and extracellular matrix for support and communication. Similarly, animal cells do not need a central vacuole because they do not undergo the same turgor pressure changes that plant cells do, and they do not need to store nutrients or waste products in a central location like plants.
3: In an amoeba, digestion mainly occurs through phagocytosis, where the cell engulfs solid food particles and forms a food vacuole. Enzymes are then released into the vacuole to break down the food into smaller molecules that can be absorbed by the cell. In a mouse, digestion involves the mechanical breakdown of food in the mouth, enzymes breaking down food in the stomach and small intestine, absorption of nutrients in the small intestine, and elimination of waste through the large intestine. While both amoebas and mice digest their food to obtain nutrients, mice have specialized digestive organs and systems that allow for more efficient digestion and absorption of nutrients from a wider variety of food sources.