Living systems are organized in levels according to their structures and functions.
-> tissues-> organs -> organ systems-> organisms -> ecosystems
Which word is missing from the organized chart above
A. Cells
B. Water
C. Bacteria
D. Protons

A. Cells

Explanation: Tissues are a group of the same cells with the same functions

both anaerobic and aerobic respiration use glucose (or other carbohydrates), proteins and lipids to produce atp and nadh. cell uses those energy molecules, obtained from food and   breaks them down during the chemical reactions of respiration. in anaerobic respiration, nadh is regenerated to nad+ by enzymes lactate dehydrogenase (lactate is produced, e.g. in muscle cells) or by alcohol dehydrogenase where ethanol is produced (alcohol fermentation), while in aerobic respiration, electrons from nadh are deposited in the mitochondria to regenerate nad+ (electron transport chain. anaerobic respiration produces 2 atp per molecule of glucose compared to aerobic respiration where about 38 atp molecules are produced.

the wires in the toaster turning red and the toast crisping and turning brown