1.3 Carbohydrates - Sugars
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38 Terms
What are carbohydrates?
Organic compounds that contain elements C, H and O.
What is the general formula of carbohydrates?
C(H₂O)ₙ
What are the three main types of carbohydrates?
Monosaccharides, disaccharides, polysaccharides.
Give examples of monosaccharides.
Glucose, fructose, galactose.
Give examples of polysaccharides.
Starch, glycogen, cellulose.
What is a monosaccharide?
Simple sugars such as glucose.
What type of sugar is glucose based on carbon number?
Hexose sugar (6 carbon atoms).
Why is glucose water soluble?
It is a polar molecule.
What are three functions of glucose in organisms?
- Source of energy in respiration 2. Stored as polysaccharides for energy storage 3. Used to make other compounds
What is the structure of glucose in solution?
It exists mainly in a ring form.
What are the two forms of glucose?
Alpha (α) glucose and beta (β) glucose.
What is α-glucose?
Glucose with the –OH group below carbon 1.
What is β-glucose?
Glucose with the –OH group above carbon 1.
Why is glucose a reducing sugar?
It can donate electrons from its aldehyde or ketone group.
Why can glucose act as a reducing agent in solution?
Because it can form a straight-chain form exposing an aldehyde group.
What is a disaccharide?
A sugar formed when two monosaccharides join together.
What is sucrose made from?
Glucose and fructose.
What type of reaction forms sucrose?
Condensation reaction.
What is removed during condensation?
A molecule of water.
What bond is formed in sucrose?
Glycosidic bond.
What type of bond is a glycosidic bond?
A glycosidic bond is a covalent bond formed between two monosaccharides during a condensation reaction
What is hydrolysis?
The breaking of a glycosidic bond by the addition of water.
Why is sucrose less reactive than glucose?
Its aldehyde and ketone groups are involved in the glycosidic bond.
Why is sucrose a non-reducing sugar?
It does not have free aldehyde or ketone groups to act as reducing agents.
Why is sucrose suitable for transport in plants?
It is less reactive than glucose.
Where is glucose transported in animals?
In the blood.
Where is sucrose transported in plants?
In the phloem.
What are pentoses?
Monosaccharides with five carbon atoms.
What are trioses?
Monosaccharides with three carbon atoms.
What is a condensation reaction?
A reaction where water is removed when forming a glycosidic bond.
What is a hydrolysis reaction?
A reaction where water is added to break a glycosidic bond.
Why is glucose used in animals but sucrose in plants?
Glucose is reactive and used for energy; sucrose is less reactive and better for transport.
What happens to a glycosidic bond during hydrolysis?
Water is added and the glycosidic bond is broken, producing two monosaccharides.
Compare the STRUCTURE of glucose and sucrose
Glucose is a monosaccharide (single sugar unit) while sucrose is a disaccharide made from glucose + fructose. Glucose exists as a single ring structure, and sucrose is formed when two monosaccharides are joined by a glycosidic bond, with a water molecule removed during formation (condensation reaction).
Compare the FUNCTIONS of glucose and sucrose
Glucose is used directly in respiration to release energy in cells and is the main immediate energy source in animals. Sucrose, on the other hand, is mainly used for transport in plants (phloem) and is less reactive (non-reducing sugar), making it safer for transport. Glucose is used immediately or stored, while sucrose is mainly a transport sugar.
How is a glycosidic bond formed?
A glycosidic bond is formed by a condensation reaction between two monosaccharides, where a molecule of water is removed, an oxygen bridge forms between the sugars, and a strong covalent glycosidic bond is produced.
How is a glycosidic bond broken?
A glycosidic bond is broken by a hydrolysis reaction, where water is added, the bond is broken, and two monosaccharides are produced.
List the features of carbohydrates.
- Contain carbon, hydrogen and oxygen 2. General formula C(H₂O)ₙ 3. Include monosaccharides, disaccharides and polysaccharides 4. Monosaccharides are small, soluble, sweet-tasting sugars 5. Polysaccharides are large, often insoluble molecules 6. Many carbohydrates act as energy sources or energy stores 7. Some provide structural support (e.g. cellulose) 8. Formed by condensation reactions and broken by hydrolysis reactions.