Carbohydrates
Introduced| English |
|---|
| starch/stɑːtʃ/ |
| monosaccharide/ˈmɒnəʊsækɑːraɪd/ |
| glucose/ˈɡluːkəʊs/ |
| disaccharide/ˌdɪsəkˈhɑːraɪd/ |
| polysaccharide/ˌpɒlɪˈsækɑːraɪd/ |
| glycogen/ˈɡlaɪkədʒn/ |
| cellulose/ˈseljuːləʊs/ |
Sugars and starches
- Carbohydrates are the cell's fast fuel and some of its building material.
- They range from a single sweet sugar to giant storage molecules.
- Bread, fruit, pasta, and plant fibres are all carbohydrates.
- Their size decides whether they give quick energy or long-term storage.
Monosaccharides: single sugars
- A monosaccharide 单糖 is one sugar unit — the simplest carbohydrate.
- Glucose 葡萄糖 is the most important: the cell's main fuel for respiration.
- Fructose (in fruit) and galactose are other single sugars.
- Most have the formula around $\text{C}_6\text{H}_{12}\text{O}_6$.
A monosaccharide is…
A monosaccharide ("one sugar") is a single sugar unit — glucose and fructose are examples.
Glucose is the main sugar that cells break down for energy.
Glucose is the cell's primary fuel — respiration breaks it down to release energy.
Disaccharides: two joined
- A disaccharide 二糖 is two monosaccharides joined by condensation.
- Sucrose (table sugar) = glucose + fructose.
- Lactose (milk sugar) = glucose + galactose.
- One condensation reaction links them and releases water.
Table sugar, sucrose, is a disaccharide made of glucose and ____.
Sucrose = glucose + fructose, joined by a condensation reaction.
Polysaccharides: many joined
- A polysaccharide 多糖 is a long chain of many sugar units.
- Starch 淀粉 stores glucose in plants; glycogen 糖原 stores it in animals.
- Cellulose 纤维素 is a tough polysaccharide that builds plant cell walls.
- Same glucose monomer, different bonds, very different roles.
Sort the sugars
Group each carbohydrate by how many sugar units it contains.
Which polysaccharide do animals use to store glucose?
Animals store glucose as glycogen (in liver and muscle); plants use starch.
Select all true statements about carbohydrates.
Carbohydrates range from single sugars to huge polymers, so not all are single units.
Starch and cellulose are both chains of glucose, yet you can digest starch and not cellulose. The glucose units are joined by different bonds, and human enzymes can only break the starch type. That is why plant fibre passes through you.
Glycogen: your body's glucose battery.
- After a meal, spare glucose is joined into glycogen in your liver and muscles.
- Between meals, hydrolysis breaks glycogen back into glucose.
- This keeps your blood glucose steady when you are not eating.
Carbohydrates are sugars, grouped by size: a monosaccharide is one unit (like glucose), a disaccharide is two, and a polysaccharide is many. Starch and glycogen store glucose; cellulose builds plant walls. Size sets the job — quick fuel or long-term storage.