Circular Arrows

This Water cycle diagram example was drawn using the ConceptDraw PRO diagramming and vector graphics software extended with the clipart libraries Geography and Weather.
"The water cycle, also known as the hydrologic cycle or the H2O cycle, describes the continuous movement of water on, above and below the surface of the Earth. The mass water on Earth remains fairly constant over time but the partitioning of the water into the major reservoirs of ice, fresh water, saline water and atmospheric water is variable depending on a wide range of climatic variables. The water moves from one reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by the physical processes of evaporation, condensation, precipitation, infiltration, runoff, and subsurface flow. In so doing, the water goes through different phases: liquid, solid (ice), and gas (vapor)." [Water cycle. Wikipedia]
This water cycle diagram example is included in the Nature solution from the Illustration area of ConceptDraw Solution Park.

The vector stencils library " Biochemistry of metabolism" contains 46 metabolite symbols for drawing metabolic pathways maps, biochemical diagrams and metabolism process flow charts using the ConceptDraw PRO diagramming and vector drawing software.
"Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, catalytic activity of their own (usually as a cofactor to an enzyme), defense, and interactions with other organisms (e.g. pigments, odorants, and pheromones). A primary metabolite is directly involved in normal "growth", development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial microbiology. A secondary metabolite is not directly involved in those processes, but usually has an important ecological function. Examples include antibiotics and pigments such as resins and terpenes etc. ...
The metabolome forms a large network of metabolic reactions, where outputs from one enzymatic chemical reaction are inputs to other chemical reactions." [Metabolite. Wikipedia]
The shapes example "Design elements - Biochemistry of metabolism" is included in the Biology solution from the Science and Education area of ConceptDraw Solution Park.

The vector stencils library "Citric acid cycle (TCA cycle)" contains 26 symbols of metabolites for drawing metabolic pathway maps and biochemical shematic diagrams of the citric acid cycle (TCA cycle, tricarboxylic acid cycle, Krebs cycle) and diagrams of metabolism processes.
"The citric acid cycle - also known as the tricarboxylic acid cycle (TCA cycle), or the Krebs cycle, - is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate derived from carbohydrates, fats and proteins into carbon dioxide and chemical energy in the form of adenosine triphosphate (ATP). In addition, the cycle provides precursors of certain amino acids as well as the reducing agent NADH that is used in numerous other biochemical reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest established components of cellular metabolism and may have originated abiogenically.
The name of this metabolic pathway is derived from citric acid (a type of tricarboxylic acid) that is consumed and then regenerated by this sequence of reactions to complete the cycle. In addition, the cycle consumes acetate (in the form of acetyl-CoA) and water, reduces NAD+ to NADH, and produces carbon dioxide as a waste byproduct. The NADH generated by the TCA cycle is fed into the oxidative phosphorylation (electron transport) pathway. The net result of these two closely linked pathways is the oxidation of nutrients to produce usable chemical energy in the form of ATP." [Citric acid cycle. Wikipedia]
The shapes example "Design elements - TCA cycle" is included in the Biology solution from the Science and Education area of ConceptDraw Solution Park.