What class of biological molecule includes sugars, starch and glycogen?
Carbohydrates
Carbohydrates are organic molecules composed of carbon, hydrogen and oxygen, often used for energy storage or structural roles.
What type of monomer forms larger carbohydrate molecules?
Monosaccharides
Monosaccharides are single sugar units that act as building blocks for disaccharides and polysaccharides.
Name three common monosaccharides found in biological systems.
- Glucose
- Galactose
- Fructose
These are hexose sugars with the same molecular formula but slightly different structures.
What type of chemical bond forms when two monosaccharides join together?
Glycosidic bond
This bond forms during a condensation reaction between two sugar molecules.
Fill in the blank:
Two monosaccharides join together through a _______ reaction to form a glycosidic bond.
Condensation
The reaction removes a molecule of water as the bond forms.
What carbohydrate is produced when two glucose molecules join together?
Maltose
Maltose is a disaccharide commonly produced during starch digestion.
Which disaccharide forms when glucose combines with fructose?
Sucrose
Sucrose is the main sugar transported in the phloem of plants.
Which disaccharide is formed from glucose and galactose?
Lactose
Lactose is the sugar found in milk.
Glucose exists in two structural forms known as what?
Isomers
The two forms are α-glucose and β-glucose, which differ in the arrangement of atoms around one carbon.
What two specific structural forms of glucose exist in solution?
- α-glucose
- β-glucose
They differ in the orientation of the hydroxyl group on carbon 1.
What term describes carbohydrates formed by many glucose units joined together?
Polysaccharides
These are large polymer molecules built from many monosaccharides.
Which two polysaccharides are formed from α-glucose in living organisms?
Starch and glycogen
Both are energy storage molecules in plants and animals respectively.
Which polysaccharide is formed from β-glucose?
Cellulose
Cellulose forms strong fibres used in plant cell walls.
What is the main storage carbohydrate in animals?
Glycogen
Glycogen is stored mainly in the liver and muscles and can be rapidly broken down to release glucose.
What is the main storage carbohydrate in plants?
Starch
Starch is stored in plant cells and consists of amylose and amylopectin molecules.
What is the main structural carbohydrate found in plant cell walls?
Cellulose
Cellulose forms strong microfibrils that provide structural support to plant cells.
Which reagent is used to test for reducing sugars?
Benedict’s solution
When heated to near boiling (≈95 °C) with a reducing sugar, the solution changes from blue to green, yellow, orange or brick-red depending on the concentration of reducing sugar.
What colour change occurs when Benedict’s test gives a positive result for reducing sugars?
Blue to brick-red precipitate
The colour may vary depending on sugar concentration.
How can a non-reducing sugar be tested using Benedict’s solution?
Hydrolysis
The sugar is first hydrolysed with dilute acid, neutralised, then tested with Benedict’s solution.
Which reagent is used to test for starch?
Iodine solution
Iodine/potassium iodide turns from brown/orange to blue-black in the presence of starch.
True or False:
Glycogen is the main storage carbohydrate in plants.
False
Plants store carbohydrates mainly as starch, while animals store glycogen.
Fill in the blank:
Iodine solution turns _______ in the presence of starch.
Blue-black
This colour change is used in qualitative food tests for starch.
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3.1.1 Monomers & Polymers9
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3.1.2 Carbohydrates22
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3.1.3 Lipids17
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3.1.4 Proteins39
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3.1.5 Nucleic Acids32
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3.1.6 ATP11
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3.1.7 Water11
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3.1.8 Inorganic ions8
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3.2.1 Cell structure52
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3.2.2 Cell division20
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3.2.3 Transport across cell membranes20
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3.2.4 Cell recognition & the immune system36
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3.3.1 Surface area to volume ratio13
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3.3.2 Gas exchange24
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3.3.3 Digestion & absorption16
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3.3.4 Mass transport39
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3.4.1 DNA, genes & chromosomes13
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3.4.2 DNA & protein synthesis14
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3.4.3 Genetic diversity & meiosis14
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3.4.4 Genetic diversity & adaptation20
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3.4.5 Species & taxonomy20
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3.4.6 Biodiversity within a community12
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3.4.7 Investigating diversity12
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3.5.1 Photosynthesis23
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3.5.2 Respiration17
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3.5.3 Energy & ecosystems20
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3.5.4 Nutrient cycles15
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3.6.1 Stimuli & Response62
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3.6.2 Nervous coordination53
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3.6.3 Skeletal muscles14
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3.6.4 Homeostasis57
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3.7.1 Inheritance12
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3.7.2 Populations15
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3.7.3 Evolution may lead to speciation22
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3.7.4 Populations in ecosystems24
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3.8.1 Gene Mutations and Protein Structure14
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3.8.2 Control of Gene Expression44
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3.8.3 Applications of Genome Projects10
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3.8.4 Gene Technologies and Their Applications46
