Study the biochemistry of plants

A foundation course for anyone working with plants or with aspirations to become a plant scientist.

Discover how significant the chemistry of plants is in our day to day lives.

A course for:

• Botany students
• Horticulturists
• Farmers
• Anyone producing, manufacturing or using plant products -in food, medicines, or elsewhere.

There are biochemical differences between different species of living organisms, and those differences become greater as the organisms being considered become more remote from each other. For example, the biochemical differences between two different mammals are far less than the differences between animals and plants.

Plants are able to photosynthesise, trapping light energy from the sun and converting it into chemical energy, stored in carbohydrates. Animals cannot do this. Different organisms will contain and use different types of chemicals within their body. Animals often contain complex chemicals, which simply do not exist in the plant kingdom.

COURSE STRUCTURE

There are 9 lessons, as follows:

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

LEARNING AIMS

• 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.

WHAT YOU WILL DO IN THIS COURSE

• Explain the formulae of ten specified, chemical compounds commonly found in plants
• Calculate the percentages of elements contained in two specified chemical compounds
• Differentiate between characteristics of major groups of biochemicals
• Compare differences between monosaccharides and polysaccharides
• Differentiate between a fat and an oil
• Explain the characteristics of a specified protein formula
• Compare two fibrous proteins with two globular proteins
• Explain the functions of carbohydrates in plants
• Explain how one specific enzyme functions in a living organism
• Explain how one specific hormone functions in a living organism
• Compare differences in nitrogen deficiency symptoms in monocotyledons and dicotyledons
• Analyse the nitrogen cycle with diagrams
• Perform an experiment comparing the growth of 4 plants grown under differing light conditions
• Explain the processes of photosynthesis, with diagrams
• Identify the differences between anaerobic and aerobic respiration
• Explain glycolysis, including the sequence of chemical reactions which take place
• Explain the Krebs cycle, including the sequence of chemical reactions involved.
• Compare respiration in a plant with respiration in an animal
• Perform, a simple experiment, showing the movement of dyed water into and through a plant
• Explain how nutrients are moved about in a plant
• Define pH terminology including; acid, alkaline, base and neutral
• Explain plant responses to changes in soil pH
• Analyse the effects of three different fertilizers on the pH of growing media.
• Explain the effects of abnormal pH levels in a specific case study of a physiological process, in a living organism.
• Identify factors involved in controlling acidity and alkalinity in a specific case study.
• Differentiate between chemical toxicity and tolerance.
• Explain the implications of LD50 characteristics with five different chemical substances.
• List the active toxins in ten poisonous plants which commonly occur in your home locality.
• Explain the effects of two naturally occurring toxins on the human body.
• Determine three different applications for plant tissue culture.

Chemical compounds found in plants are commonly derived from carbohydrates which are synthesised during photosynthesis. These compounds can be divided into two main groups: primary and secondary metabolites. Some chemicals may be both primary and secondary, so this grouping is a slight generalisation but it is a widely used method. 

Primary Metabolites

These are found in all plant cells. They are used in basic plant processes and biochemical reactions concerned with growth and metabolism. They include fats, proteins, and carbohydrates. From a commercial perspective primary metabolites are harvested for use in large quantities as relatively low value raw materials for industry, or foods such as vegetable oils, as well as food additives such as proteins and carbohydrates like starch, cellulose and sucrose.

Amongst the primary metabolites, some have physiological influences on the human body but it is mostly secondary metabolites    

Secondary Metabolites

This is the group of most interest to us because medicinal plants have lots of these chemicals. In fact, it is the presence of secondary metabolites which give medicinal plants their name. There are thousands of these secondary metabolites.  They are generally not involved in growth and metabolic processes but instead many of them are used by plants to fight against pathogens or to ward off attacks from herbivores by being toxic or repellent to them. They therefore play a role in defence. Others may inhibit the growth of other competitor plants, and some are responsible for pigments and odours which attract pollinating insects to plants. 

Secondary metabolites are derived from primary metabolites. There are different ways to classify them but one method which is widely adopted is to group them into alkaloids, phenolic compounds, and terpenoids. Alkaloids and phenolic compounds are synthesised by the shikimic pathway. Terpenoids are synthesised via the acetyl-CoA mevalonic acid pathway.

Consider Alkaloids

Alkaloids are compounds which contain mainly nitrogen along with some hydrogen and carbon. They may also contain oxygen and sulphur. More rarely other elements may be present including phosphorous, bromine and chlorine. They are derived from primary metabolites including amino acids like lysine, tyrosine and tryptophan. Most are salts of organic acids e.g. acetic, citric and oxalic acids. Alkaloids have certain chemical characteristics such as reacting chemically like alkaline substances because of the presence of a nitrogen atom. Many are highly toxic if consumed by animals and they often taste bitter.   

Some alkaloids have great medicinal value if used carefully. Alkaloids have many different effects on the human body, for example morphine and codeine in opium are well known pain relieving alkaloids.  Vinblastine is an anti-cancer alkaloid. Others include sanguinarine which is an antibiotic, scopolamine which is a sedative, tubocuranine which is a muscle relaxant, colchicines used to suppress gout, and ajmalicine which acts as a an antiarrhythmic combating irregular patterns of heartbeats.  Nicotine in tobacco is also an alkaloid, as is caffeine in coffee and tea beverages and these both act as stimulants.

Alkaloids may be found throughout whole plants or they may be concentrated in certain plant parts like seeds, bark or roots. Nicotine and tropane alkaloids are made in the roots and then transported to above ground parts. Some, such as nicotinic acid derivatives, are found in many plants albeit in different forms. Also, some are found in particular plant families or groups of plants. For example, the anticholinergic alkaloids scopolamine, atropine and hyoscyamine are mainly found in plants from the solanaceae family.  Toxic tropane alkaloids are found in berries of plants form the convolvulaceae, solanaceae and erythroxylaceae families.  

Many isoquinoline alkaloids are found in plants of the papaveraceae, ranunculaceae, berbidaceae, and menispermaceae families. Amongst these is the opium poppy (Papaver somniferum) which contains three of these alkaloids in morphine, thebaine and codeine.

• DOES LEARNING MORE INTEREST YOU?

then ... study this course.

• IF YOU WORK WITH PLANTS BUT DIDN'T REALIZE THERE ARE SUCH COMPLEXITIES BELOW THE SURFACE

then ... study this course.

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