2.2.3
Examples of Carbohydrates
Starch
Starch
Starch is a polysaccharide formed by condensation reactions of alpha-glucose molecules.


Functions of starch
Functions of starch
- Starch is the main energy storage material in plants.
- Starch is stored in the seeds of plants.
- Starch is broken down into glucose by plants when they need more energy.
- Starch can act as a source of food for humans and animals.


Features of starch
Features of starch
- Starch does NOT change the water potential in a cell because it's insoluble in water.
- Starch is made up of amylopectin and amylose, which are both alpha-glucose polysaccharides.


Amylopectin
Amylopectin
- Amylopectin is a highly branched chain of alpha-glucose monomers.
- The branched structure means that enzymes can easily access the glycosidic bonds and so the glucose molecules can be quickly released when needed.


Amylose
Amylose
- Amylose is a linear chain of alpha-glucose monomers.
- Because of the way the monomers are joined, the glucose chains have a helical structure.
- This means that the amylose strands can pack closely together, making this form of starch particularly good for storage.


Iodine test
Iodine test
- A common test for the presence of starch, particularly in food testing, is to add iodine.
- Iodine is used commonly as a name for a solution of potassium iodide.
- Step 1: Place a small sample into the dimple of a spotting tile or to a boiling tube.
- Step 2: Add a few drops of iodine and observe any colour change.
- If starch is present, the solution will change colour from orange → blue-black.
Glycogen
Glycogen
Glycogen is formed by condensation reactions of alpha-glucose molecules and is the main energy storage material in animals. It can be thought of as the animal equivalent of starch.


Function of glycogen
Function of glycogen
- Glycogen is a highly branched molecule, similar to amylopectin (a form of starch).
- When animals need to release energy, glycogen's highly branched structure means that glucose can be released fast.


Glycogen in the human body
Glycogen in the human body
- Glycogen is a good storage molecule because it is so compact.
- When blood glucose levels decrease, glycogen is broken down to release glucose. This is called glycogenolysis.
Cellulose
Cellulose
Cellulose is the major component of cell walls in plants.


Structure of cellulose
Structure of cellulose
- Cellulose is a long chain of beta-glucose.
- Beta-glucose molecules are linked by glycosidic bonds to form linear cellulose chains that are unbranched.
- Microfibrils are strong fibres that are made of many cellulose chains that are held together by hydrogen bonds.
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Function of cellulose
Function of cellulose
- Cellulose is the most abundant natural polymer.
- The cell walls of plant cells are mostly made of cellulose.
- These cell walls offer structural support because of the strength of the microfibril fibres that they are made of.


Digestion of cellulose
Digestion of cellulose
- Cellulose cannot be broken down by human digestive enzymes.
- Herbivores, such as cows and horses, are able to digest plant material rich in cellulose.
1Cell Structure
1.1Cell Structure
1.1.1Studying Cells - Microscopes
1.1.2Introduction to Eukaryotic & Prokaryotic Cells
1.1.3Ultrastructure of Eukaryotic Cells
1.1.4Ultrastructure of Eukaryotic Cells 2
1.1.5Ultrastructure of Eukaryotic Cells 3
1.1.6Prokaryotic Cells
1.1.7Viruses
1.1.8End of Topic Test - Cell Structure
1.1.9Exam-Style Question - Microscopes
1.1.10A-A* (AO2/3) - Cell Structure
2Biological Molecules
2.1Testing for Biological Modules
2.2Carbohydrates & Lipids
2.3Proteins
3Enzymes
4Cell Membranes & Transport
4.1Biological Membranes
5The Mitotic Cell Cycle
6Nucleic Acids & Protein Synthesis
6.1Nucleic Acids
7Transport in Plants
8Transport in Mammals
8.1Circulatory System
8.2Transport of Oxygen & Carbon Dioxide
9Gas Exchange
9.1Gas Exchange System
10Infectious Diseases
10.1Infectious Diseases
10.2Antibiotics
11Immunity
12Energy & Respiration (A2 Only)
13Photosynthesis (A2 Only)
14Homeostasis (A2 Only)
14.1Homeostasis
14.2The Kidney
14.3Cell Signalling
14.4Blood Glucose Concentration
14.5Homeostasis in Plants
15Control & Coordination (A2 Only)
15.1Control & Coordination in Mammals
15.1.1Neurones
15.1.2Receptors
15.1.3Taste
15.1.4Reflexes
15.1.5Action Potentials
15.1.6Saltatory Conduction
15.1.7Synapses
15.1.8Cholinergic Synnapses
15.1.9Neuromuscular Junction
15.1.10Skeletal Muscle
15.1.11Sliding Filament Theory Contraction
15.1.12Sliding Filament Theory Contraction 2
15.1.13Menstruation
15.1.14Contraceptive Pill
15.2Control & Co-Ordination in Plants
16Inherited Change (A2 Only)
16.1Passage of Information to Offspring
16.2Genes & Phenotype
17Selection & Evolution (A2 Only)
17.2Natural & Artificial Selection
18Classification & Conservation (A2 Only)
18.1Biodiversity
18.2Classification
19Genetic Technology (A2 Only)
19.1Manipulating Genomes
19.2Genetic Technology Applied to Medicine
19.3Genetically Modified Organisms in Agriculture
Jump to other topics
1Cell Structure
1.1Cell Structure
1.1.1Studying Cells - Microscopes
1.1.2Introduction to Eukaryotic & Prokaryotic Cells
1.1.3Ultrastructure of Eukaryotic Cells
1.1.4Ultrastructure of Eukaryotic Cells 2
1.1.5Ultrastructure of Eukaryotic Cells 3
1.1.6Prokaryotic Cells
1.1.7Viruses
1.1.8End of Topic Test - Cell Structure
1.1.9Exam-Style Question - Microscopes
1.1.10A-A* (AO2/3) - Cell Structure
2Biological Molecules
2.1Testing for Biological Modules
2.2Carbohydrates & Lipids
2.3Proteins
3Enzymes
4Cell Membranes & Transport
4.1Biological Membranes
5The Mitotic Cell Cycle
6Nucleic Acids & Protein Synthesis
6.1Nucleic Acids
7Transport in Plants
8Transport in Mammals
8.1Circulatory System
8.2Transport of Oxygen & Carbon Dioxide
9Gas Exchange
9.1Gas Exchange System
10Infectious Diseases
10.1Infectious Diseases
10.2Antibiotics
11Immunity
12Energy & Respiration (A2 Only)
13Photosynthesis (A2 Only)
14Homeostasis (A2 Only)
14.1Homeostasis
14.2The Kidney
14.3Cell Signalling
14.4Blood Glucose Concentration
14.5Homeostasis in Plants
15Control & Coordination (A2 Only)
15.1Control & Coordination in Mammals
15.1.1Neurones
15.1.2Receptors
15.1.3Taste
15.1.4Reflexes
15.1.5Action Potentials
15.1.6Saltatory Conduction
15.1.7Synapses
15.1.8Cholinergic Synnapses
15.1.9Neuromuscular Junction
15.1.10Skeletal Muscle
15.1.11Sliding Filament Theory Contraction
15.1.12Sliding Filament Theory Contraction 2
15.1.13Menstruation
15.1.14Contraceptive Pill
15.2Control & Co-Ordination in Plants
16Inherited Change (A2 Only)
16.1Passage of Information to Offspring
16.2Genes & Phenotype
17Selection & Evolution (A2 Only)
17.2Natural & Artificial Selection
18Classification & Conservation (A2 Only)
18.1Biodiversity
18.2Classification
19Genetic Technology (A2 Only)
19.1Manipulating Genomes
19.2Genetic Technology Applied to Medicine
19.3Genetically Modified Organisms in Agriculture
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