Biochemistry I - Plants

Course CodeBSC102
Fee CodeS2
Duration (approx)100 hours
QualificationStatement of Attainment

Study Plant Biochemistry

  • Foundation course for anyone working with plants: from gardeners to research assistants
  • Improve your understanding of what makes plants grow
  • Improve your job prospects in horticultural, environmental, agricultural and other industries

Chemical reactions are at the heart of everything that happens in a plant; from the germinating of seeds and the growth of tissues, to the production of flowers and fruit. Understanding these chemical reactions will help you understand how plants grow, and in turn, how to treat them.

The Problem Based Approach for learning in this course makes the educational experience practical and applied, helping you to understand, absorb and retain your new knowledge.

Student Comment: 'Having not finished high school myself and never studied biochemistry my confidence is a little low but the encouragement I am receiving from Honor [tutor] is a tremendous help and making it easier for me as I go. [The course] is helping me realize what I am actually capable of and that I am smarter than I thought. Thank you for making it possible for me to study my passion while still being able to work.' Melissa Smith, Australia, Biochemistry 1 (Diploma in Horticulture).

Lessons cover: Biochemical substances and terms, carbohydrates, lipids, amino acids, proteins, metabolism, the nitrogen cycle, photosynthesis, respiration, transpiration, acidity and alkalinity, nutrition, hormones, chemical analysis and biochemical applications in industry.

Prerequisites: Some secondary school chemistry will be helpful though it is not essential.

Lesson Structure

There are 9 lessons in this course:

  1. Introduction
  2. Lipids and Proteins
  3. Enzymes
  4. Nitrogen and the Nitrogen Cycle
  5. Photosynthesis and Respiration
  6. Assimilation and Transpiration
  7. Acidity and Alkalinity
  8. Chemical Analysis
  9. Biochemical Applications

Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.


  • Identify characteristics of common chemical compounds important in plant biochemistry.
  • Explain the characteristics of major biochemical groups including; carbohydrates, lipids and proteins.
  • Explain the characteristics of chemicals which control biological processes, including enzymes and hormones.
  • Identify the role of nitrogen in plant biological processes, including the nitrogen cycle.
  • Identify the role of photosynthesis in biological systems.
  • Explain the role of respiration in plants.
  • Explain characteristics of assimilation and transpiration in plants.
  • Explain the effect of acidity and alkalinity on biochemical systems.
  • Develop simple chemical analysis skills relevant to testing plants and soils.
  • Identify applications and uses for biochemical processes and products.


Plants are made up of lots of different chemicals. An understanding of plant chemistry is a foundation for understanding not only how to grow plants but also how to use them.

Consider the following examples of different types of chemicals that are found in plants, and do this course to lay a foundation to better understanding plant biochemistry:

Group 1: Saponins
Saponin containing plants are characterised by soap like foam when they are shaken in water.  For this reason, many native peoples throughout the world have long used saponin containing plants for cleansing.

Basically they act to speed up the passage of other substances through the walls of the gastrointestinal tract and to stimulate secretion from the mammary glands and glands along the respiratory tract.

Saponin containing plants can be used as:
a. Expectorants (i.e. phlegm removing substances) e.g. primrose roots, mullein flowers and leaves, lungwort leaves.
b. Diuretics (i.e. substances which increase the flow of urine) e.g. golden rod leaves, Java tea leaves.
c. Lactation stimulants. Nursing mothers have used goat's rue for this purpose.

They have also been used to help re establish the smooth functioning of body fluids e.g. pansy and horsetail leaves.

Group 2: Phenolglycosides
There are two particularly significant types of phenoglycosides:
1. Arbutin has a disinfecting action on the urinary tract when the urine is alkaline e.g. blueberry and bearberry leaves.

2. Salicin is chemically related to the salicylic acid in aspirin, therefore is useful in reducing fever and relieving pain e.g. pansy leaves, willow bark, poplar leaves and bark.

Group 3: Anthraglycosides
In this group, Anthraquinone (also called emodin), is used to relieve constipation e.g. senna leaves, aloes, buckthorn, rhubarb.

Group 4: flavonoids
Some flavonoids can act to stimulate the cardio-vascular system; others have diuretic properties, whilst others inhibit infections.  Rutin, one of the flavonoids, has an anti haemorrhagic effect.  It also helps the blood vessels to expand, thereby lowering blood pressure.  Examples of flavonoid containing plants are camomile flowers, juniper berries, broom leaves, linden blossoms, hawthorn flowers and birch leaves. 

Group 5: Mustard Oils
Plants that contain mustard oil glycosides can be used as rubefacients i.e. can improve the blood circulation near the surface of the skin.  They can be particularly useful for relieving breathing problems during colds and bronchitis.  Mustard oil glycosides also have antibiotic properties e.g. water-cress.
Group 6: Polysaccharides
The polysaccharide group includes pectin which acts to control diarrhoea and bleeding; mucilage which soothes inflamed mucous membranes, and inulin.  Fructose results from the digestion of inulin which is readily metabolised in the body and is converted into glycogen ("animal starch") even when insulin is lacking.  Mucilage containing plants are linseed, marshmallow root, coltsfoot leaves and mullein.  Pectin is found in fruits such as apples.

Group 7: Prussic Acid
Prussic acid has a local anaesthetic effect.  It is found in almonds and may be one of the reasons for the relief given to dry, chapped skin when almond oil is used. 

Group 8: Glycosides
Digitalis glycoside (from the leaves of the foxglove), convallatoxin glycoside (from lily of the valley), and oleandrin (from oleander), are natural chemical compounds which have an effect on the heart muscles.  These should only be used with extreme caution as they contain toxins which can be fatal.

Group 9: Coumarin
Coumarin containing plants such as woodruff are used to prevent or dissolve blood clots or thrombotic clots.  

Group 10: Tannins
Tannins have a mild astringent effect on the skin.  They also have disinfectant properties, and can help to combat diarrhoea.  Examples of plants that contain tannins are walnut leaves, sage leaves, blueberries, and oak bark.

Group 11: Bitters
Bitters promote bile secretion, improve the uptake of nutrients from the gastrointestinal tract, and stimulate digestive juices.  They also combat gastrointestinal fermentation. Plants which contain bitters are angelica root, milfoil leaves, gentian root and wormwood foliage. These four plants are called aromatic bitters because they also contain essential oils (see next paragraph).

Group 12: Essential Oils
When heated, essential oils (also called aromatic, volatile or ethereal oils) will variously act to reduce inflammation, relieve cramping, promote milk flow, aid digestion, expel gas, disinfect, and sooth the nerves.        

Group 13: Alkaloids
Alkaloids are nitrogen containing compounds with certain chemical characteristics such as reacting chemically like alkaline substances.  They have many different effects on the human body, for example morphine and codeine in opium are well known pain relieving alkaloids.  Nicotine in tobacco is also an alkaloid.

Group 14: Purines
Caffeine is a purine which increases the flow of urine and supports healthy heart function.  Too much caffeine though will cause harmful over stimulation.

Group 15: Essential Minerals
Plants of all kinds contain minerals which are essential for good health.  For example, spinach contains large amounts or iron and Vitamin A; horsetail is rich in silicon which acts to clear up the symptoms of arteriosclerosis; bladder wrack seaweed is rich in iodine which is used to treat people with goitre and obesity.