To stand up in English is to "stand". The word "stand" comes from the Old English word "standan", which means "to stand or place upright". Here are some example sentences in English and their translations in Chinese:

Can you stand up and help me with this heavy box? 你能站起来帮我搬这个沉重的箱子吗？

I stood up to stretch my legs after sitting for so long. 我站起来伸展一下我长时间坐着的腿。

The crowd stood up and cheered as the winning team was announced. 当获胜的队伍宣布时，人群站起来欢呼。