2.1.1

Tests for Sugars & Starch

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Benedict's Test for Sugars

Benedict’s solution (also known as Benedict's reagent or the Benedict’s test) can be used as a test for reducing and non-reducing sugars.

Reducing sugars

Reducing sugars

  • All monosaccharides are reducing sugars.
    • E.g. Glucose, galactose and fructose.
  • Some disaccharides are reducing sugars.
    • E.g. Lactose and maltose.
Test for reducing sugars

Test for reducing sugars

  • Benedict's solution can be reduced by reducing sugars.
  • Benedict's solution is a clear blue liquid that changes colour and gives a precipitate depending on how much it is reduced.
    • Step 1: Place 2 ml of the substance in a boiling tube (substance must be in liquid form).
    • Step 2: Add 10 drops of Benedict's solution.
    • Step 3: Place in a boiling water bath for 3-5 minutes.
Results of the Benedict's test

Results of the Benedict's test

  • Blue solution → no reducing sugar.
  • Green/yellow precipitate → traces of reducing sugar.
  • Orange/red precipitate → moderate amounts of reducing sugar.
  • Brick red precipitate → large amount of reducing sugar.
  • The faster the colour change occurs, the greater the concentration of reducing sugar present.
Non-reducing sugars

Non-reducing sugars

  • Non-reducing sugars will show a negative result to the Benedict’s test. A second test is needed to determine if non-reducing sugar is present.
  • Sucrose is a non-reducing sugar. It is a disaccharide made up of glucose and fructose joined by a glycosidic bond.
Test for non-reducing sugars

Test for non-reducing sugars

  • Step 1: Boil in dilute HCl (to hydrolyse the non-reducing sugar).
  • Step 2: Neutralise the solution by adding sodium bicarbonate.
  • Step 3: Repeat the Benedict’s test.
    • The result will now be positive if a non-reducing sugar is present.
    • If the solution remains blue, then no sugar is present.

The Iodine Test for Starch

A common test for the presence of starch, particularly in food testing, is to add iodine. Iodine is commonly used as a name for a solution of potassium iodide.

Step 1

Step 1

  • Place a small sample into the dimple of a spotting tile or into a boiling tube.
Step 2

Step 2

  • Add a few drops of iodine and observe any colour change.
Results

Results

  • If starch is present, the solution will change colour from orange → blue-black.
Jump to other topics
1

Cell Structure

1.1

Cell Structure

1.1.1Studying Cells - Microscopes1.1.2Introduction to Eukaryotic & Prokaryotic Cells1.1.3Ultrastructure of Eukaryotic Cells1.1.4Ultrastructure of Eukaryotic Cells 21.1.5Ultrastructure of Eukaryotic Cells 31.1.6Prokaryotic Cells1.1.7Viruses1.1.8End of Topic Test - Cell Structure1.1.9Exam-Style Question - Microscopes1.1.10A-A* (AO2/3) - Cell Structure
2

Biological Molecules

2.1

Testing for Biological Modules

2.1.1Tests for Sugars & Starch2.1.2Tests for Lipids & Proteins
2.2

Carbohydrates & Lipids

2.2.1Monomers & Polymers2.2.2Carbohydrates2.2.3Examples of Carbohydrates2.2.4Triglycerides & Phospholipids2.2.5Types of Fatty Acids2.2.6Exam-Style Question - Carbohydrates2.2.7End of Topic Test - Carbohydrates & Lipids
2.3

Proteins

2.3.1Amino Acids & Overview of Protein Structure2.3.2Primary & Secondary Structure2.3.3Tertiary & Quaternary Structure2.3.4Globular & Fibrous Proteins2.3.5Haemoglobin2.3.6Collagen2.3.7End of Topic Test - Proteins
2.4

Water

2.4.1Water Structure & Function2.4.2End of Topic Test - Water
3

Enzymes

3.1

Enzymes

3.1.1Enzyme Action3.1.2Factors Affecting Enzyme Activity3.1.3Factors Affecting Enzyme Activity 23.1.4A-A* (AO2/3) - Enzymes
4

Cell Membranes & Transport

4.1

Biological Membranes

4.1.1Fluid Mosaic Model4.1.2Cell Signalling4.1.3End of Topic Test - Biological Membranes4.1.4Exam-Style Question - Membranes
4.2

Movement Into & Out of Cells

4.2.1Passive Movement Across the Membrane4.2.2Active Movement Across the Membrane4.2.3Osmosis4.2.4Osmosis & Plant Cells4.2.5Surface Area to Volume Ratio4.2.6Adaptions to Surface Area to Volume Ratio4.2.7Calculations - Volume4.2.8Calculations - Surface Area
5

The Mitotic Cell Cycle

5.1

Replication & Division of Nuclei

5.1.1Chromosomes5.1.2The Cell Cycle5.1.3Mitosis5.1.4Role of Mitosis5.1.5Stem Cells5.1.6Mitosis & Cancer5.1.7End of Topic Test - Replication & Division5.1.8A-A* (AO2/3) - Cell Cycle & Transport
6

Nucleic Acids & Protein Synthesis

6.1

Nucleic Acids

6.1.1Introduction to DNA & RNA6.1.2Nucleotides6.1.3Polynucleotides6.1.4ADP & ATP6.1.5DNA6.1.6DNA Replication6.1.7RNA6.1.8End of Topic Test - Nucleic Acids & ATP
6.2

Protein Synthesis

6.2.1The Genetic Code6.2.2Polypeptide Synthesis6.2.3RNA Processing in Eukaryotes6.2.4Mutations6.2.5Exam-Style Question - Protein Synthesis6.2.6A-A* (AO2/3) - Coronavirus Translation
7

Transport in Plants

7.1

Transport in Plants

7.1.1Plant Vessels7.1.2Xylem7.1.3Investigating Transpiration7.1.4Adaptations to Water Availability7.1.5Phloem7.1.6End of Topic Test - Transport in Animals & Plants7.1.7A-A* (AO2/3) - Transport in Animals & Plants
8

Transport in Mammals

8.1

Circulatory System

8.1.1Double Circulation8.1.2Blood Vessels8.1.3Important Blood Vessels8.1.4Blood Cells8.1.5Tissue Fluid
8.2

Transport of Oxygen & Carbon Dioxide

8.2.1Haemoglobin8.2.2Oxygen Dissociation
8.3

The Heart

8.3.1Structure of the Heart8.3.2The Cardiac Cycle8.3.3Coordination of Heart Action
9

Gas Exchange

9.1

Gas Exchange System

9.1.1Mammalian Gas Exchange9.1.2Smoking
10

Infectious Diseases

10.1

Infectious Diseases

10.1.1Transmission of Disease10.1.2Tuberculosis10.1.3HIV10.1.4Malaria10.1.5Cholera10.1.6Measles
10.2

Antibiotics

10.2.1Antibiotics
11

Immunity

11.1

The Immune System

11.1.1Phagocytes11.1.2Antigens11.1.3Lymphocytes11.1.4Primary & Secondary Response
11.2

Antibodies & Vaccination

11.2.1Antibodies11.2.2Monoclonal Antibodies11.2.3Immunity11.2.4Vaccines11.2.5Exam-Style Question - Immune System11.2.6A-A* (AO2/3) - Disease & Immune System
12

Energy & Respiration (A2 Only)

12.1

Energy

12.1.1Energy & ATP12.1.2Respiratory Substrates & Quotient12.1.3Respirometers
12.2

Respiration

12.2.1Introduction to Respiration12.2.2Anaerobic Respiration12.2.3Aerobic Respiration12.2.4Chemiosmosis & Coenzymes12.2.5Mitochondria12.2.6Respiration Experiments12.2.7End of Topic Test - Respiration12.2.8A-A* (AO3/4) - Respiration
13

Photosynthesis (A2 Only)

13.1

Photosynthesis

13.1.1Introduction to Photosynthesis13.1.2Light-Dependent Reactions13.1.3Light-Independent Reactions13.1.4Limiting Factors13.1.5Investigating Photosynthesis13.1.6End of Topic Test - Photosynthesis13.1.7A-A* (AO3/4) - Photosynthesis
14

Homeostasis (A2 Only)

14.1

Homeostasis

14.1.1Homeostasis14.1.2Negative Feedback
14.2

The Kidney

14.2.1Kidneys & Osmoregulation
14.3

Cell Signalling

14.3.1Messengers & cAMP
14.4

Blood Glucose Concentration

14.4.1Blood Glucose Concentration14.4.2Controlling Blood Glucose14.4.3Urinalysis
14.5

Homeostasis in Plants

14.5.1Stomata & Guard Cells
15

Control & Coordination (A2 Only)

15.1

Control & Coordination in Mammals

15.1.1Neurones15.1.2Receptors15.1.3Taste15.1.4Reflexes15.1.5Action Potentials15.1.6Saltatory Conduction15.1.7Synapses15.1.8Cholinergic Synnapses15.1.9Neuromuscular Junction15.1.10Skeletal Muscle15.1.11Sliding Filament Theory Contraction15.1.12Sliding Filament Theory Contraction 215.1.13Menstruation15.1.14Contraceptive Pill
15.2

Control & Co-Ordination in Plants

15.2.1Venus Flytrap15.2.2Auixns15.2.3Gibberellins
16

Inherited Change (A2 Only)

16.1

Passage of Information to Offspring

16.1.1Meiosis16.1.2Gametogenesis16.1.3Meiosis & Genetic Diversity
16.2

Genes & Phenotype

16.2.1Key Terms in Genetics16.2.2Inheritance16.2.3Linkage16.2.4Multiple Alleles16.2.5Chi-Squared Test16.2.6Mutations16.2.7Specific Mutations16.2.8End of Topic Test - Genetics16.2.9A-A* (AO2/3) - Genetics
16.3

Gene Control

16.3.1lac Operon16.3.2Transcription Factors16.3.3Gibberellins & DELLA Proteins
17

Selection & Evolution (A2 Only)

17.1

Variation

17.1.1Phenotypic Variation17.1.2Continuous & Discontinuous Variation17.1.3t-Tests
17.2

Natural & Artificial Selection

17.2.1Natural Selection & Evolution17.2.2Types of Selection17.2.3Types of Selection Summary17.2.4Genetic Drift & Founder Effect17.2.5Populations17.2.6Hardy-Weinberg Principle17.2.7Artificial Selection
17.3

Evolution

17.3.1Evolution by Natural Selection17.3.2Evidence for Evolution17.3.3Speciation17.3.4Extinction
18

Classification & Conservation (A2 Only)

18.1

Biodiversity

18.1.1Key Terms18.1.2Biodiversity18.1.3Sampling Methods18.1.4Correlation18.1.5Spearman’s Rank18.1.6Measuring Biodiversity
18.2

Classification

18.2.13-Domain Classification System18.2.2Linnaean Classification System
18.3

Conservation

18.3.1Importance of Biodiversity18.3.2Conservation18.3.3Zoos, Seedbanks, & Other Conservation Methods18.3.4Assisted Reproduction & Contraception18.3.5Non-Governmental Organisations
19

Genetic Technology (A2 Only)

19.1

Manipulating Genomes

19.1.1Recombinant DNA & Genetic Engineering19.1.2Restriction Endonucleases19.1.3Gel Electrophoresis19.1.4DNA Probes & Microarrays19.1.5End of Topic Test - Manipulating Genomes19.1.6A-A* (AO2/3) - Manipulating Genomes
19.2

Genetic Technology Applied to Medicine

19.2.1Bioinformatics19.2.2Applications of Recombinant DNA19.2.3Genetic Screening19.2.4Gene Therapy19.2.5Ethics19.2.6DNA Profiling & Forensics
19.3

Genetically Modified Organisms in Agriculture

19.3.1GM Crops & Livestock19.3.2Ethics

Practice questions on Tests for Sugars & Starch

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    What can the Benedict’s test be used to test?Fill in the list
  2. 2
    Test for Non-Reducing SugarsPut in order
  3. 3
    Which of the following describes Benedict's solution?Multiple choice
  4. 4
    If starch is present, what colour change is seen during the iodine test?Multiple choice
  5. 5
    What is used to test for starch in food testing?Multiple choice
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A-A* (AO2/3) - Cell Structure

Tests for Lipids & Proteins