<Tr> <Td> Very strongly alkaline </Td> <Td>> 9.0 </Td> </Tr> <P> pH - dependent plant pigments that can be used as pH indicators occur in many plants, including hibiscus, red cabbage (anthocyanin) and red wine . The juice of citrus fruits is acidic mainly because it contains citric acid . Other carboxylic acids occur in many living systems . For example, lactic acid is produced by muscle activity . The state of protonation of phosphate derivatives, such as ATP, is pH - dependent . The functioning of the oxygen - transport enzyme hemoglobin is affected by pH in a process known as the Root effect . </P> <P> The pH of seawater is typically limited to a range between 7.5 and 8.4 . It plays an important role in the ocean's carbon cycle, and there is evidence of ongoing ocean acidification caused by carbon dioxide emissions . However, pH measurement is complicated by the chemical properties of seawater, and several distinct pH scales exist in chemical oceanography . </P> <P> As part of its operational definition of the pH scale, the IUPAC defines a series of buffer solutions across a range of pH values (often denoted with NBS or NIST designation). These solutions have a relatively low ionic strength (≈ 0.1) compared to that of seawater (≈ 0.7), and, as a consequence, are not recommended for use in characterizing the pH of seawater, since the ionic strength differences cause changes in electrode potential . To resolve this problem, an alternative series of buffers based on artificial seawater was developed . This new series resolves the problem of ionic strength differences between samples and the buffers, and the new pH scale is referred to as the' total scale', often denoted as pH . The total scale was defined using a medium containing sulfate ions . These ions experience protonation, H + SO 2 − 4 ⇌ HSO − 4, such that the total scale includes the effect of both protons (free hydrogen ions) and hydrogen sulfate ions: </P>

Discuss how ph is important in biological reaction in our body