Chemical Constituents of Organisms 生物體的化學成分
Organisms are made up of chemical substances which can be divided into two groups: Inorganic substances and organic substances
生物體是由化學物質組成的，這些化學物質可以分為兩類：無機物質和有機物質。
Inorganic substances 無機物
- Water and minerals are examples of inorganic substances commonly found in organisms
水和礦物質是生物體中常見的無機物質例子。 - Although they contain carbon, simple carbon-containing substances such as carbon monoxide, carbon dioxide, and the hydrogencarbonate ion (CO, CO₂, HCO₃⁻) are considered inorganic substances.
雖然它們含有碳，但簡單的含碳物質如一氧化碳、二氧化碳和碳酸氫根離子（CO、CO₂、HCO₃⁻）被認為是無機物質。
Organic substances (Biomolecules) 有機物質（生物分子）
- Carbohydrates, lipids, proteins and nucleic acids are the major organic substances in organisms
碳水化合物、脂質、蛋白質和核酸是生物體內的主要有機物質。 - These organic molecules substances are called biomolecules. They all contain carbon.
這些有機分子物質被稱為生物分子。它們都含有碳。
Composition of Our Body 我們身體的組成
Water 水
- Water is the most abundant compound in organisms
水是生物體內最豐富的化合物。 - In humans, water makes up about 65% of our body weight
在人體中，水約佔我們體重的65%。 - Water is essential to organisms
水對生物體是必不可少的。
Functions of water 水的功能
As a solvent and transport medium 作為溶劑和運輸介質
Water is a good solvent. It dissolves various substances
水是一種良好的溶劑。它能溶解各種物質。
Solvent 溶劑
It provides a medium for chemical reactions to take place in cells
它為細胞內的化學反應提供介質。
Transport medium 運輸介質
- It acts as a transport medium
它作為運輸介質。 - For example, blood is mainly made up of water. Nutrients, gases and metabolic activities are transported by blood around the body
例如，血液主要由水組成。營養物質、氣體和代謝產物通過血液在體內運輸。
As a reactant 作為反應物
Water is the reactant of some metabolic reactions in organisms:
水是生物體內一些代謝反應的反應物：
Digestion 消化
在消化過程中，需要水來分解複雜的食物物質。
During digestion, water is needed to break down complex food substances
Photosynthesis 光合作用
在光合作用過程中，植物利用水和二氧化碳在光和葉綠素的存在下生產食物（如葡萄糖）和氧氣。
During photosynthesis, plants use water and carbon dioxide to produce food (e.g. glucose) and oxygen in the presence of light and chlorophyll
$$\quad\text{carbon dioxde}\quad+\quad\mathrm{water}\quad\frac{\mathrm{light}}{\mathrm{chlorophyll}}\quad\mathrm{glucose}\quad+\quad\mathrm{oxygen}$$
$$\quad\text{二氧化碳}\quad+\quad\mathrm{水}\quad\frac{\mathrm{光}}{\mathrm{葉綠素}}\quad\mathrm{葡萄糖}\quad+\quad\mathrm{氧氣}$$
As a cooling agent 作為冷卻劑
- Water acts as a cooling agent in organisms
水在生物體內作為冷卻劑。 - For example, sweat is consists mainly of water
例如，汗液主要由水組成。 - When sweat evaporates, it takes away some heat. This helps lower the body temperature
當汗液蒸發時，它會帶走一些熱量，這有助於降低體溫。 - In plants, the evaporation of water from plants surfaces (called transpiration) helps prevent plants from overheating
在植物中，水從植物表面蒸發（稱為蒸騰作用）有助於防止植物過熱。
As a temperature buffer 作為溫度緩衝劑
- Water has a large specific heat capacity, which means it absorbs a large amount of heat before its temperature increases
水具有很大的比熱容，這意味著它在溫度升高之前能吸收大量的熱量。 - As organisms contain a high proportion of water, their body temperature may remain fairly stable when there is small fluctuation in environmental temperature
由於生物體內含有大量的水，當環境溫度有小幅波動時，它們的體溫可以保持相對穩定。 - Large bodies of water such as oceans and lakes have relatively constant temperatures, so they provide a suitable habitat for aquatic organisms
大型水體如海洋和湖泊的溫度相對穩定，因此它們為水生生物提供了適宜的棲息地。
As a supporting agent 作為支撐劑
- Water gives shape and support to organisms
水為生物體提供形狀和支撐。 - For example, in some animals (e.g. earthworms and jellyfish), they body cavity is filled with liquid, which serves as a hydrostatic skeleton (i.e. hydroskeleton) for support and movement
例如，在一些動物（如蚯蚓和水母）中，它們的體腔充滿液體，這些液體作為水力骨骼（即水骨骼）來支撐和運動。 - Plant cells become turgid when they have sufficient water
當植物細胞有足夠的水時，它們會變得膨脹。 - This provides turgidity to support young seedlings and non-woody plants
這為幼苗和非木本植物提供了支撐。 - Water has a high density. It provides buoyancy for aquatic plants and animals
水具有高密度，為水生植物和動物提供浮力。
Minerals 礦物質
- Minerals are inorganic substances
礦物質是無機物質。 - They are needed in small amounts for the normal functioning of organisms
它們以少量形式存在於生物體內，對生物體的正常功能至關重要。 - Most minerals are in the form of inorganic ions dissolved in cytoplasm and body fluid
大多數礦物質以無機離子的形式溶解在細胞質和體液中。 - They play important roles in regulating metabolism
它們在調節代謝方面發揮著重要作用。 - On the other hand, some minerals form body structures in organisms. For example, our bones and teeth contain calcium phosphate
另一方面，一些礦物質構成了生物體的結構。例如，我們的骨骼和牙齒含有磷酸鈣。
| Inorganic Ion (無機離子) | Functions | 功能 (zh-tw) |
| Sodium 鈉 (Na+) | Important for water balance | 重要的水分平衡 |
| Magnesium 鎂 (Mg2+) | Needed for plants for forming chlorophyll | 植物形成葉綠素所需 |
| Calcium 鈣 (Ca2+) |
| 需要肌肉收縮和血液凝固 骨骼和牙齒的結構成分 |
| Iron 鐡 (Fe3+) | Needed for forming haemoglobin, a pigment in red blood cells for carrying oxygen | 需要形成血紅蛋白，紅血球中的一種色素，用於攜帶氧氣 |
| Chloride 氯化物 (Cl–) |
| 重要的水分平衡 形成胃液中的鹽酸所需 |
| Nitrate 硝酸鹽 (NO3-) | Needed in plants for forming proteins | 植物形成蛋白質所需 |
| Phosphate 磷酸鹽 (PO43-) | Component of nucleic acids and cell membranes | 核酸和細胞膜的組成部分 |
Carbohydrates 碳水化合物
- Carbohydrates are organic substances made up of carbon (C), hydrogen (H) and oxygen (O)
碳水化合物是由碳 (C)、氫 (H) 和氧 (O) 組成的有機物質 - They have a general formula of Cx(H2O)y
它們的通式為 Cx(H2O)y - The ratio of hydrogen atoms to oxygen atoms is 2:1
氫原子與氧原子的比例為 2:1 - For example, the chemical formula of glucose (a 6-carbon carbohydrate) is C6H12O6
例如，葡萄糖（一種含有 6 個碳的碳水化合物）的化學式為 C6H12O6
Carbohydrates are classified into three types according to their complexity:
碳水化合物根據其複雜性分為三種類型：
- Monosaccharides 單醣
- Disaccharides 雙醣
- Polysaccharides 多醣
Carbohydrates 碳水化合物 種類1：Monosaccharides 單糖
- Monosaccharides are the simplest forms of carbohydrates
單醣是最簡單形式的碳水化合物 - Properties: They are soluble in water and taste sweet
性質：它們可溶於水且味道甜
Glucose, fructose and galactose
葡萄糖、果糖和半乳糖
- Glucose is the most common monosaccharide found in organisms
葡萄糖是生物體內最常見的單醣 - Function: Glucose can be broken down directly in the body cells during respiration to provide energy (for cellular activities)
功能：葡萄糖可以在呼吸過程中直接在體細胞中分解，提供能量（用於細胞活動） - Other examples are fructose and galactose
其他例子包括果糖和半乳糖
所有單醣都是還原糖
All monosaccharides are reducing sugars
- 它們的存在可以通過本尼迪克試驗中形成的磚紅色沉澱來指示
Their presence is indicated by the formation of brick-red precipitate in Benedict’s test
| Glucose 葡萄糖 | Fructose 果糖 | Galactose 半乳糖 | |
| 存在於 | Most organisms 大多數生物體 | Fruits 水果 | Milk 牛奶 |
| 功能 | 即時能量來源 | – | – |
Test for Glucose – Glucose Test Strips
葡萄糖測試 – 葡萄糖試紙
Dip the glucose test strip in the sample solution.
將葡萄糖試紙浸入樣品溶液中。
| Observation 觀測 | Result 結論 | |
| Positive result 陽性結果 | Colour changes from green to brown | Glucose is present 存在葡萄糖 |
| Negative result 陰性結果 | No observable change | Glucose is absent 不存在葡萄糖 |
Test for Reducing Sugar – Benedict’s Test
還原糖測試 – 本尼迪克試驗
- Add 2 cm3 of sample solution into test tube A and 2 cm3 of distilled water into test tube B.
將 2 cm³ 的樣品溶液加入試管 A 中，將 2 cm³ 的蒸餾水加入試管 B 中。- Add 2 cm3 of Benedict’s solution into each of the test tubes and shake gently.
向每個試管中加入 2 cm³ 的本尼迪克試劑並輕輕搖動。- Put test tubes A and B in a boiling water bath for five minutes
將試管 A 和 B 放入沸水浴中五分鐘。
| Observation 觀測 | Result 結論 | |
| Positive result 陽性結果 | Brick-red precipitate are formed | Reducing sugar is present 存在還原糖 |
| Negative result 陰性結果 | No observable change | Reducing sugar is absent 不存在還原糖 |
Other Types of monosaccharides
其他單糖例子
- There are many types of monosaccharides
有許多種類的單醣 - Glucose, fructose and galactose are some examples
葡萄糖、果糖和半乳糖是一些例子 - But there are also many types:
但還有許多其他類型：
Triose 三碳糖
- ‘Tri’ = Three, ‘-ose’ means sugar
‘Tri’ = 三，‘-ose’ 意味著糖 - Triose means 3-carbon sugar
三碳糖指的是含有三個碳原子的糖
例如：呼吸途徑和光合作用中的三碳糖磷酸鹽
Triose phosphate (TP) in respiration pathways and Calvin cycle in photosynthesis
Glycolysis 糖酵解
Glucose 葡萄糖 —> 2 Triose phosphate 三碳糖磷酸鹽
Calvin Cycle 卡爾文循環
3C compound 化合物 —> Triose phosphate 三碳糖磷酸鹽
Pentose 五碳糖
5-Carbon sugar
五碳糖
E.g. 5-C CO2 acceptor in Calvin cycle in photosynthesis
例如：光合作用中卡爾文循環的 5 碳二氧化碳受體
5C CO2 acceptor —> 3C compound
5碳 二氧化碳 受體 —> 3 碳化合物
E.g. 5-C sugar (ribose and deoxyribose) in nucleic acid
例如：核酸中的 5 碳糖（核糖和脫氧核糖）
Carbohydrates 碳水化合物 種類2：Disaccharides 雙糖 (Double sugar)
- Disaccharides are formed when two monosaccharides combine with the removal of a water molecule
雙醣是由兩個單醣結合並去除一個水分子形成的 - This reaction is called condensation
這個反應稱為縮合反應 - The bond in-between is a glycosidic bond
中間的鍵是糖苷鍵 - Properties: They are soluble in water and taste sweet
性質：它們可溶於水且味道甜 - They are reducing sugar (except sucrose)
它們是還原糖（除了蔗糖）
Condensation 縮合反應
Condensation is a reversible reaction
縮合反應是可逆反應
- Disaccharides can be broken down into monosaccharides by using water. This reaction is called hydrolysis
雙醣可以通過使用水分解成單醣。這個反應稱為水解反應 - Enzymes are needed in both reactions inside the bodies of organisms to catalyse the reaction
在生物體內的這兩個反應中都需要酶來催化反應
- (Malt sugar) – formed when two glucose molecules condensed together
（麥芽糖）– 由兩個葡萄糖分子縮合形成 - (Cane sugar) – formed when glucose molecule condenses with fructose
（蔗糖）– 由葡萄糖分子與果糖縮合形成 - (Milk sugar) – formed when glucose molecule condenses with galactose
（乳糖）– 由葡萄糖分子與半乳糖縮合形成
Carbohydrates 碳水化合物 種類3：Polysaccharides 多糖 (Complex sugar)
- Polysaccharides are large molecules formed by condensation of a large number of monosaccharide molecules
多醣是由大量單醣分子縮合形成的大分子 - Properties: Polysaccharides are insoluble or only very slightly soluble in water. They do not taste sweet
性質：多醣不溶於水或僅微溶於水。它們沒有甜味
Starch, glycogen, cellulose 澱粉、糖原、纖維素
- Starch is the storage form of carbohydrates in plants
澱粉是植物中碳水化合物的儲存形式 - Glycogen is the storage form of carbohydrates in animals
糖原是動物中碳水化合物的儲存形式 - Cellulose is the main component of plant cell walls to give it a rigid structure
纖維素是植物細胞壁的主要成分，賦予其堅硬的結構
| Starch (澱粉) | Glycogen (糖原) | Cellulose (纖維素) | |
| Found in (存在於) | Many parts of plants (as starch grains), seeds (e.g., cereals), storage organs of plants (e.g., potato tuber) 植物的許多部位（如澱粉粒）、種子（如穀物）、植物的儲藏器官（如馬鈴薯塊莖） | Animals (In humans, they are primarily stored in cells of liver and skeletal muscles) 動物（在人類中，主要儲存在肝臟和骨骼肌細胞中） | Food rich in dietary fibre (e.g., fruits, vegetables 富含膳食纖維的食物（如水果、蔬菜） |
| Function (功能) | Main source of energy 主要能量來源 | Storage form of carbohydrates in animals 動物中碳水化合物的儲存形式 | As a main component of plant cell wall for support 作為植物細胞壁的主要成分，提供支撐 |
Test for Starch – Iodine Test 澱粉測試 – 碘測試
- Add 2 drops of sample solution in a well of a spot plate.
在點板的一個孔中加入2滴樣品溶液。- Add 2 drops of iodine solution into the same well and observe.
在同一孔中加入2滴碘溶液並觀察。
| Observation 觀測 | Result 結論 | |
| Positive result 陽性結果 | Colour changes from brown to blue-black | Starch is present 存在還原糖 |
| Negative result 陰性結果 | No observable change (Colour remains brown) | Starch is absent 不存在還原糖 |
Lipids 脂質
- Lipids are also organic substances made up of carbon (C), hydrogen (H) and oxygen (O)
脂質也是由碳 (C)、氫 (H) 和氧 (O) 組成的有機物質 - But the ratio of hydrogen atoms to oxygen atoms is greater than 2:1
但氫原子與氧原子的比例大於 2:1。 - Properties: Lipids are insoluble in water, but soluble in organic solvent such as ether and ethanol
性質：脂質不溶於水，但溶於有機溶劑如乙醚和乙醇。 - Triglycerides (Fat and Oil), phospholipids, steroids
甘油三酯（脂肪和油）、磷脂、類固醇 - One of the main groups of lipids are triglycerides, which are commonly known as fats and oils (solid triglycerides are fats and liquid triglycerides are called oils)
脂質的主要類別之一是甘油三酯，通常稱為脂肪和油（固體甘油三酯稱為脂肪，液體甘油三酯稱為油）。 - Other important lipids include phospholipids and steroids
其他重要的脂質包括磷脂和類固醇。
Lipids 脂質 種類1：Triglycerides 甘油三酯
- They are fats and oils (solids or liquids, depending on their melting points)
它們是脂肪和油（根據其熔點，可能是固體或液體）。 - A triglyceride molecule is formed by the condensation of one glycerol molecule and three fatty acid molecules
一個甘油三酯分子是由一個甘油分子和三個脂肪酸分子縮合而成的。 - The three fatty acids (FA) can be the same or different
這三個脂肪酸（FA）可以相同也可以不同。
Triglycerides Function 甘油三酯 功能
- Fats and oils are energy reserves in organisms
脂肪和油是生物體內的能量儲備。 - In mammals, fats are stored in adipose tissues in the body. These tissues may be found under the skin as subcutaneous fat, which acts as an insulating layer to reduce heat loss
在哺乳動物中，脂肪儲存在體內的脂肪組織中。這些組織可能位於皮膚下，稱為皮下脂肪，起到減少熱量散失的絕緣層作用。 - Adipose tissues are also found around internal organs and acts as shocker-absorbers for protection
脂肪組織也存在於內臟周圍，起到保護作用，作為減震器。 - In plants, oils are produced and stored in the seeds
在植物中，油在種子中生成並儲存。
Lipids 脂質 種類2：Phospholipids 磷脂
- A molecule of phospholipid is composed of a glycerol, two fatty acids and a phosphate group
一個磷脂分子由一個甘油、兩個脂肪酸和一個磷酸基團組成。 - Phospholipids are main components of cell membranes
磷脂是細胞膜的主要成分。
Lipids 脂質 種類3：Steroids 磷脂
- Steroids are a group of lipids with highly complex molecules
類固醇是一組具有高度複雜分子的脂質。 - A common example of a steroid is cholesterol, which is an essential component of cell membrane to stabilize its structure
類固醇的一個常見例子是膽固醇，它是細胞膜的重要組成部分，用於穩定其結構。 - Cholesterol is used by the liver for making bile salts and also to make steroid hormones in the sex organs
膽固醇被肝臟用來製造膽鹽，並在性器官中製造類固醇激素。 - It is also important in the production of vitamin D by the skin
它在皮膚生成維生素D的過程中也很重要。
Test for Lipids – Grease Spot Test 脂質測試 – 油漬測試
- Add a drop of sample solution to a piece of filter paper. Mark the position of the spot with a pencil.
在濾紙上滴一滴樣品溶液，用鉛筆標記位置。- Add a drop of distilled water besides and mark the position with pencil too.
在旁邊滴一滴蒸餾水，也用鉛筆標記位置。- Examine the filter paper against a light source, wait ten minutes and examine it again. [Spot disappears = water]
將濾紙對著光源檢查，等待十分鐘後再次檢查。[斑點消失 = 水]- Dip the filter paper into an organic solvent such as ether, acetone or hexane and allow it to dry in air
將濾紙浸入有機溶劑譬如乙醚、丙酮或己烷中，然後在空氣中晾乾。- Examine it against light again [Persistent translucent spot disappears after dipping in organic solvent = lipid]
再次對著光源檢查。[浸入有機溶劑後持續存在的半透明斑點消失 = 脂質]
| Observation 觀測 | Result 結論 | |
| Positive result 陽性結果 | Permanent translucent spot disappears after dipping the filter paper in organic solvent (e.g. ether) | Lipid is present 存在脂質 |
| Negative result 陰性結果 | The spot disappears | The spot is water 表示斑點是水 |
Protein 蛋白質
Proteins are organic substances made up of carbon (C), hydrogen (H), oxygen (O) and nitrogen (N). Some proteins may also contain sulphur (S)
蛋白質是由碳 (C)、氫 (H)、氧 (O) 和氮 (N) 組成的有機物質，有些蛋白質還可能含有硫 (S)。
Amino acid 氨基酸
- The basic unit of proteins are amino acids
蛋白質的基本單位是氨基酸。 - More than 100 different kinds of amino acids are known to occur in cells, but only 20 of them are used to make proteins
已知細胞中存在超過100種不同的氨基酸，但只有20種用於製造蛋白質。 - Each amino acid molecule has a central carbon atom, an amino group (-NH2), a carboxyl group (-COOH) and a side chain (-R group)
每個氨基酸分子都有一個中心碳原子、一個氨基 (-NH2)、一個羧基 (-COOH) 和一個側鏈 (-R 基團)。 - The side chain is unique for each kind of amino acid
側鏈對每種氨基酸都是獨特的。
Condensation of amino acids 氨基酸的縮合反應
- When the amino group of one amino acid and the carboxyl group of another are joined by condensation, a dipeptide is formed
當一個氨基酸的氨基 (-NH2) 與另一個氨基酸的羧基 (-COOH) 通過縮合反應連接時，形成一個二肽。 - The bond linking the amino acid is called a peptide bond
連接氨基酸的鍵稱為肽鍵。
Polypeptide 多肽
- When many amino acids are joined together, a chain of amino acids called a polypeptide is formed
當許多氨基酸連接在一起時，形成的氨基酸鏈稱為多肽。 - A protein may consist of one or more polypeptide chains
蛋白質可能由一條或多條多肽鏈組成。 - Similar to the 26 letters of the English alphabet, which can form a million different words, the 20 different kinds of amino acids can be joined together in different combinations and sequence to form different polypeptides or proteins, which have different functions in organisms
類似於英文字母表中的26個字母可以組成數百萬個不同的單詞，20種不同的氨基酸可以以不同的組合和順序連接在一起，形成不同的多肽或蛋白質，這些蛋白質在生物體中具有不同的功能。
Functions of proteins 蛋白質的功能
Proteins are components of various cellular structures such as the cytoplasm and the cell membrane
蛋白質是細胞結構（如細胞質和細胞膜）的組成部分。They are needed for formation of new cells. Thus, proteins are important for the growth and repair of body tissues
它們對新細胞的形成是必需的。因此，蛋白質對於身體組織的生長和修復非常重要。Almost all body structures contain proteins
幾乎所有的身體結構都含有蛋白質。Proteins are used to make many important molecules in our body
蛋白質用於製造我們體內的許多重要分子。These include enzymes, antibodies and certain hormones
這些分子包括酶、抗體和某些激素。- Enzyme catalyse (i.e. increase the rate of) chemical reactions in cells
酶催化（即增加）細胞內的化學反應速率。 - Antibodies help protect our body against germs
抗體幫助保護我們的身體免受病菌侵害。 - Hormones are involved in controlling various processes in the body
激素參與控制體內的各種過程。
- Enzyme catalyse (i.e. increase the rate of) chemical reactions in cells
Protein can be a source of energy [last source of energy]
蛋白質可以作為能量來源（最後的能量來源）。When the reserves of carbohydrates and lipids are used up, our body starts to break down proteins to provide energy
當碳水化合物和脂質的儲備耗盡時，我們的身體開始分解蛋白質以提供能量。
Test for Protein – Protein Test Strips
蛋白質測試 – 蛋白質測試紙
- Add 2 drops of sample solution in a well of a spot plate.
在點板的一個孔中加入2滴樣品溶液。- Dip a protein test strip into the well and observe.
將蛋白質測試紙浸入孔中並觀察。
| Observation 觀測 | Result 結論 | |
| Positive result 陽性結果 | Colour changes from yellow to green | Protein is present 存在蛋白質 |
| Negative result 陰性結果 | No observable change | Protein is absent 不存在蛋白質 |
Nucleic acid 核酸
- Nucleic acids are organic substances found mainly in the nucleus of a cell
核酸是主要存在於細胞核中的有機物質。 - They are made up of carbon (C), hydrogen (H), oxygen (O), nitrogen (N) and phosphorus (P)
它們由碳 (C)、氫 (H)、氧 (O)、氮 (N) 和磷 (P) 組成。
There are two types of nucleic acids
核酸有兩種類型
- deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)
脫氧核糖核酸 (DNA) 和核糖核酸 (RNA) - They play important roles in heredity and protein synthesis
它們在遺傳和蛋白質合成中起重要作用。
Nucleotide 核苷酸
5-carbon sugar 五碳糖
- In DNA, the 5-carbon sugar is deoxyribose
在DNA中，五碳糖是脫氧核糖。 - In RNA, the 5-carbon sugar is ribose
在RNA中，五碳糖是核糖。
Nitrogenous base 含氮鹼基
- A nitrogenous base contains nitrogen in addition to carbon, hydrogen and oxygen
含氮鹼基除了碳、氫和氧外，還含有氮。 - There are five types of bases: adenine (A), thymine (T), guanine (G), cytosine (C) and uracil (U)
有五種類型的鹼基：腺嘌呤 (A)、胸腺嘧啶 (T)、鳥嘌呤 (G)、胞嘧啶 (C) 和尿嘧啶 (U)。 - A, T, G and C appears in DNA
A、T、G 和 C 出現在DNA中。 - A, U, G and C appears in RNA
A、U、G 和 C 出現在RNA中。
Phosphate group 磷酸基團
- A phosphate group is a chemical group consisting of a phosphorus atom bonded to four oxygen atoms, with the chemical formula
磷酸基團是一個由磷原子和四個氧原子組成的化學基團，化學式為
- It is very important in biochemistry, especially in the structure of nucleic acids like DNA and RNA.
它在生物化學中非常重要，特別是在核酸（如DNA和RNA）的結構中。 - Phosphate groups link nucleotides together through phosphodiester bonds to form long chains of nucleic acids.
磷酸基團通過磷酸二酯鍵將核苷酸連接在一起，形成核酸的長鏈。
Condensation of Nucleotide 核苷酸的縮合反應
- Two nucleotides join to form a dinucleotide by condensation between the phosphate group of one nucleotide and the 5-C carbon sugar of the other nucleotide
兩個核苷酸通過一個核苷酸的磷酸基團與另一個核苷酸的五碳糖之間的縮合反應連接，形成二核苷酸。 - This process is repeated up to many times to make a polynucleotide
這個過程可以重複多次，形成多核苷酸。
Structures of DNA and RNA DNA和RNA的結構
- A DNA molecule consists of two polynucleotide chains coiled around each other to form a double helix
一個DNA分子由兩條多核苷酸鏈纏繞在一起形成雙螺旋結構。 - The two chains are held together by the hydrogen bonds formed between the bases of two chains
這兩條鏈通過兩條鏈的鹼基之間形成的氫鍵連接在一起。 - The hydrogen bonds can keep the double helix stable
氫鍵可以保持雙螺旋結構的穩定性。 - An RNA molecule consists of a single polynucleotide chain
一個RNA分子由單條多核苷酸鏈組成。
Comparison Between DNA and RNA DNA和RNA的比較
| DNA | RNA | |
| 5-carbon sugar 五碳糖 | Deoxyribose 脫氧核糖 | Ribose 核糖 |
| Nitrogenous base 含氮鹼基 | Adenine (A), thymine (T), guanine (G), cytosine (C) 腺嘌呤 (A)、胸腺嘧啶 (T)、 鳥嘌呤 (G)、胞嘧啶 (C) | Adenine (A), uracil (U), guanine (G), cytosine (C) 腺嘌呤 (A)、尿嘧啶 (U)、 鳥嘌呤 (G)、胞嘧啶 (C) |
| Structures 結構 | Double helix 雙螺旋 | Single chain 單鏈 |