1. 羟qiǎng基（hydroxyl）

其化学式为 $\text{-OH}$

Compound and example: 酒精 / 乙醇（alcohol / ethanol）化学式如下

Properties: Polar. H-bonds with water. Linked to molecules by condensation.

2. 羧suō基（carboxyl）

其化学式为 $\text{-COOH}$

Compound and example: 羧酸 / 乙酸，醋酸（carboxylic acid / acetic acid）化学式如下

Properties: Acidic and gives up ${\text{H}}^{\text{+}}$ to negatively charged. Linked to alcohols and amines by condensation.

3. 氨基（amino）

其化学式为 ${\text{-NH}}_{\text{2}}$

Compound and example: 胺 / 甲胺（amine / methyl amine）化学式如下

Properties: Basic and takes up ${\text{H}}^{\text{+}}$ to positively charged. Linked to carboxylic acids by condensation.

4. 磷酸盐（phosphate）

其化学式为 ${\text{PO}}_{\text{4}}^{\text{3-}}$

Compound and example: 有机磷酸酯 / 3-磷酸甘油酸盐（organic phosphate / 3-phosphoglycerate）化学式如下

Properties: Acidic and gives up ${\text{H}}^{\text{+}}$ to negatively charged. Linked to alcohols by condensation. Form high energy bonds with other phosphates.

5. 巯基（sulfhydryl）

其化学式为 $-\text{SH}$

Compound and example: 硫醇 / 巯基乙醇（thiol / mercaptoethanol）化学式如下

Properties: Polar. Linked to other thiols to form disulfides. Important in proteins (cysteine)

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