1.2.2
Types of Polysaccharides
Starch
Starch
Starch is a polysaccharide and a common storage compound.


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.


Iodine test
Iodine test
- A common test for the presence of starch, particularly in food testing, is to add iodine solution.
- Iodine solution is made by mixing iodine and 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 solution 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 quickly be released.


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.
1Biological Molecules
1.1Monomers & Polymers
1.2Carbohydrates
1.3Lipids
1.4Proteins
1.4.1The Peptide Chain
1.4.2Investigating Proteins
1.4.3Primary & Secondary Protein Structure
1.4.4Tertiary & Quaternary Protein Structure
1.4.5Enzymes
1.4.6Factors Affecting Enzyme Activity
1.4.7Enzyme-Controlled Reactions
1.4.8End of Topic Test - Lipids & Proteins
1.4.9A-A* (AO3/4) - Enzymes
1.4.10A-A* (AO3/4) - Proteins
1.4.11Diagnostic Misconceptions - Enzyme Inhibitors
1.5Nucleic Acids
1.6ATP
1.7Water
1.8Inorganic Ions
2Cells
2.1Cell Structure
2.2Mitosis & Cancer
2.3Transport Across Cell Membrane
2.4Cell Recognition & the Immune System
2.4.1Immune System
2.4.2Phagocytosis
2.4.3T Lymphocytes
2.4.4B Lymphocytes
2.4.5Antibodies
2.4.6Primary & Secondary Response
2.4.7Vaccines
2.4.8HIV
2.4.9Ethical Issues
2.4.10End of Topic Test - Immune System
2.4.11Exam-Style Question - Immune System
2.4.12A-A* (AO3/4) - Immune System
2.4.13Diagnostic Misconceptions - Humoral vs Cellular
3Substance Exchange
3.1Surface Area to Volume Ratio
3.2Gas Exchange
3.3Digestion & Absorption
3.4Mass Transport
3.4.1Haemoglobin
3.4.2Oxygen Transport
3.4.3The Circulatory System
3.4.4The Heart
3.4.5Blood Vessels
3.4.6Cardiovascular Disease
3.4.7Heart Dissection
3.4.8Xylem
3.4.9Phloem
3.4.10Investigating Plant Transport
3.4.11End of Topic Test - Mass Transport
3.4.12A-A* (AO3/4) - Mass Transport
3.4.13Diagnostic Misconceptions - Concentration Gradient
3.4.14Diagnostic Misconceptions - Cardiac Cycle
3.4.15Diagnostic Misconceptions - Carrying Capacity
3.4.16Diagnostic Misconceptions - Translocation
4Genetic Information & Variation
4.1DNA, Genes & Chromosomes
4.2DNA & Protein Synthesis
4.3Mutations & Meiosis
4.4Genetic Diversity & Adaptation
4.5Species & Taxonomy
4.6Biodiversity Within a Community
4.7Investigating Diversity
5Energy Transfers (A2 only)
5.1Photosynthesis
5.1.1Overview of Photosynthesis
5.1.2Photoionisation of Chlorophyll
5.1.3Production of ATP & Reduced NADP
5.1.4Cyclic Photophosphorylation
5.1.5Light-Independent Reaction
5.1.6A-A* (AO3/4) - Photosynthesis Reactions
5.1.7Limiting Factors
5.1.8Photosynthesis Experiments
5.1.9End of Topic Test - Photosynthesis
5.1.10A-A* (AO3/4) - Photosynthesis
5.2Respiration
5.2.1Overview of Respiration
5.2.2Anaerobic Respiration
5.2.3A-A* (AO3/4) - Anaerobic Respiration
5.2.4The Link Reaction
5.2.5The Krebs Cycle
5.2.6Oxidative Phosphorylation
5.2.7Respiration Experiments
5.2.8End of Topic Test - Respiration
5.2.9A-A* (AO3/4) - Respiration
5.2.10Diagnostic Misconceptions - Aerobic vs Anaerobic
5.3Energy & Ecosystems
6Responding to Change (A2 only)
6.1Nervous Communication
6.2Nervous Coordination
6.3Muscle Contraction
6.4Homeostasis
6.4.1Overview of Homeostasis
6.4.2Blood Glucose Concentration
6.4.3Controlling Blood Glucose Concentration
6.4.4End of Topic Test - Blood Glucose
6.4.5Primary & Secondary Messengers
6.4.6Diabetes Mellitus
6.4.7Measuring Glucose Concentration
6.4.8Osmoregulation
6.4.9Controlling Blood Water Potential
6.4.10ADH
6.4.11End of Topic Test - Diabetes & Osmoregulation
6.4.12A-A* (AO3/4) - Homeostasis
6.4.13Diagnostic Misconceptions - Effect of ADH
7Genetics & Ecosystems (A2 only)
7.1Genetics
7.2Populations
7.3Evolution
7.3.1Variation
7.3.2Natural Selection & Evolution
7.3.3End of Topic Test - Populations & Evolution
7.3.4Types of Selection
7.3.5Types of Selection Summary
7.3.6Overview of Speciation
7.3.7Causes of Speciation
7.3.8Diversity
7.3.9End of Topic Test - Selection & Speciation
7.3.10A-A* (AO3/4) - Populations & Evolution
7.3.11Diagnostic Misconceptions - Types of Speciation
8The Control of Gene Expression (A2 only)
8.1Mutation
8.2Gene Expression
8.2.1Stem Cells
8.2.2Stem Cells in Disease
8.2.3End of Topic Test - Mutation & Gene Epression
8.2.4A-A* (AO3/4) - Mutation & Stem Cells
8.2.5Regulating Transcription
8.2.6Epigenetics
8.2.7Epigenetics & Disease
8.2.8Regulating Translation
8.2.9Experimental Data
8.2.10End of Topic Test - Transcription & Translation
8.2.11Tumours
8.2.12Correlations & Causes
8.2.13Prevention & Treatment
8.2.14End of Topic Test - Cancer
8.2.15A-A* (AO3/4) - Gene Expression & Cancer
8.3Genome Projects
Jump to other topics
1Biological Molecules
1.1Monomers & Polymers
1.2Carbohydrates
1.3Lipids
1.4Proteins
1.4.1The Peptide Chain
1.4.2Investigating Proteins
1.4.3Primary & Secondary Protein Structure
1.4.4Tertiary & Quaternary Protein Structure
1.4.5Enzymes
1.4.6Factors Affecting Enzyme Activity
1.4.7Enzyme-Controlled Reactions
1.4.8End of Topic Test - Lipids & Proteins
1.4.9A-A* (AO3/4) - Enzymes
1.4.10A-A* (AO3/4) - Proteins
1.4.11Diagnostic Misconceptions - Enzyme Inhibitors
1.5Nucleic Acids
1.6ATP
1.7Water
1.8Inorganic Ions
2Cells
2.1Cell Structure
2.2Mitosis & Cancer
2.3Transport Across Cell Membrane
2.4Cell Recognition & the Immune System
2.4.1Immune System
2.4.2Phagocytosis
2.4.3T Lymphocytes
2.4.4B Lymphocytes
2.4.5Antibodies
2.4.6Primary & Secondary Response
2.4.7Vaccines
2.4.8HIV
2.4.9Ethical Issues
2.4.10End of Topic Test - Immune System
2.4.11Exam-Style Question - Immune System
2.4.12A-A* (AO3/4) - Immune System
2.4.13Diagnostic Misconceptions - Humoral vs Cellular
3Substance Exchange
3.1Surface Area to Volume Ratio
3.2Gas Exchange
3.3Digestion & Absorption
3.4Mass Transport
3.4.1Haemoglobin
3.4.2Oxygen Transport
3.4.3The Circulatory System
3.4.4The Heart
3.4.5Blood Vessels
3.4.6Cardiovascular Disease
3.4.7Heart Dissection
3.4.8Xylem
3.4.9Phloem
3.4.10Investigating Plant Transport
3.4.11End of Topic Test - Mass Transport
3.4.12A-A* (AO3/4) - Mass Transport
3.4.13Diagnostic Misconceptions - Concentration Gradient
3.4.14Diagnostic Misconceptions - Cardiac Cycle
3.4.15Diagnostic Misconceptions - Carrying Capacity
3.4.16Diagnostic Misconceptions - Translocation
4Genetic Information & Variation
4.1DNA, Genes & Chromosomes
4.2DNA & Protein Synthesis
4.3Mutations & Meiosis
4.4Genetic Diversity & Adaptation
4.5Species & Taxonomy
4.6Biodiversity Within a Community
4.7Investigating Diversity
5Energy Transfers (A2 only)
5.1Photosynthesis
5.1.1Overview of Photosynthesis
5.1.2Photoionisation of Chlorophyll
5.1.3Production of ATP & Reduced NADP
5.1.4Cyclic Photophosphorylation
5.1.5Light-Independent Reaction
5.1.6A-A* (AO3/4) - Photosynthesis Reactions
5.1.7Limiting Factors
5.1.8Photosynthesis Experiments
5.1.9End of Topic Test - Photosynthesis
5.1.10A-A* (AO3/4) - Photosynthesis
5.2Respiration
5.2.1Overview of Respiration
5.2.2Anaerobic Respiration
5.2.3A-A* (AO3/4) - Anaerobic Respiration
5.2.4The Link Reaction
5.2.5The Krebs Cycle
5.2.6Oxidative Phosphorylation
5.2.7Respiration Experiments
5.2.8End of Topic Test - Respiration
5.2.9A-A* (AO3/4) - Respiration
5.2.10Diagnostic Misconceptions - Aerobic vs Anaerobic
5.3Energy & Ecosystems
6Responding to Change (A2 only)
6.1Nervous Communication
6.2Nervous Coordination
6.3Muscle Contraction
6.4Homeostasis
6.4.1Overview of Homeostasis
6.4.2Blood Glucose Concentration
6.4.3Controlling Blood Glucose Concentration
6.4.4End of Topic Test - Blood Glucose
6.4.5Primary & Secondary Messengers
6.4.6Diabetes Mellitus
6.4.7Measuring Glucose Concentration
6.4.8Osmoregulation
6.4.9Controlling Blood Water Potential
6.4.10ADH
6.4.11End of Topic Test - Diabetes & Osmoregulation
6.4.12A-A* (AO3/4) - Homeostasis
6.4.13Diagnostic Misconceptions - Effect of ADH
7Genetics & Ecosystems (A2 only)
7.1Genetics
7.2Populations
7.3Evolution
7.3.1Variation
7.3.2Natural Selection & Evolution
7.3.3End of Topic Test - Populations & Evolution
7.3.4Types of Selection
7.3.5Types of Selection Summary
7.3.6Overview of Speciation
7.3.7Causes of Speciation
7.3.8Diversity
7.3.9End of Topic Test - Selection & Speciation
7.3.10A-A* (AO3/4) - Populations & Evolution
7.3.11Diagnostic Misconceptions - Types of Speciation
8The Control of Gene Expression (A2 only)
8.1Mutation
8.2Gene Expression
8.2.1Stem Cells
8.2.2Stem Cells in Disease
8.2.3End of Topic Test - Mutation & Gene Epression
8.2.4A-A* (AO3/4) - Mutation & Stem Cells
8.2.5Regulating Transcription
8.2.6Epigenetics
8.2.7Epigenetics & Disease
8.2.8Regulating Translation
8.2.9Experimental Data
8.2.10End of Topic Test - Transcription & Translation
8.2.11Tumours
8.2.12Correlations & Causes
8.2.13Prevention & Treatment
8.2.14End of Topic Test - Cancer
8.2.15A-A* (AO3/4) - Gene Expression & Cancer
8.3Genome Projects
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