1. Plant Metabolism

2. Photosynthesis

3. The Most Important Equation in Biology

5. Primary Metabolites
Primary metabolites are compounds that are commonly produced by all plants and that are directly used in plant growth and development.
The main primary metabolites are carbohydrates, proteins, nucleic acids, and lipids.

6. Carbohydrates
Carbohydrates are the sugars made up of glucose and its isomers
Carbohydrates come in many different sizes:
Monosaccharides made up of one sugar unit (glucose or fructose)
Disaccharides made up of two sugar units (sucrose is made of a glucose and a fructose)
Polysaccharides are polymers made up of more than two sugar units

8. Harvesting Sucrose
Sugar Cane Maple Syrup

9. Traditional extraction of sugar sap from sugar cane – Assam, India

10. Tapa dulce – Costa Rica

11. Refining Sucrose

12. Maltose and Sucrose

13. Malting Process

14. Malt Varieties

15. Polysaccharides Structural polysaccharides are used to support plants
Storage polysaccharides are used to store energy for later use by the plant

16. Structural Polysaccharides
The most common structural polysaccharide in plants is cellulose. It makes up 40 to 60% of the cell wall. It is also the most common polymer on earth
Cellulose is extremely strong due to its chemical organization. It is made of a long chain of beta-glucose molecules – 100 to 15,000 glucose molecules

19. Cotton Boll – Pure Cellulose

20. Gluey Polysaccharides
Pectins are mainly polymers of galacturonic acid.
Hemicelluloses are highly variable and are not related to cellulose.
Grass hemicelluloses are high in xylose, with small amounts of arabinose, galactose, and urionic acids. But pea family (Fabaceae) hemicelluloses are high in arabinose, galactose and urionic acid, but low in xylose.
Some of the most interesting hemicelluloses are not actually used structurally, but rather are exuded from stems, leaves, roots, or fruits in a sticky mixture called a gum

21. Pectin and Hemicellulose

22. Gum Arabic from Acacia senegal

23. Storage Polysaccharides
The most important storage polysaccharides are amylose and amylopectin. Amylose is a long chain of alpha-glucose, several hundred to several thousand molecules long. Amylopectin is more complex, often made up of 50,000 molecules.
These two polymers are both used in making starch grains. Most starch grains are about 20% amylose and 80% amylopectin, but this varies with the plant species.

26. Inulin – another storage carbohydrate – long chain of fructose

27. Jerusalem artichoke

28. Digestability
The properties of alpha-glucose and beta-glucose affect their digestability. Alpha-glucose polymers don’t form fibrils and thus are not as strong as cellulose from beta-glucose. Even more important, almost all organisms have alpha-amylase, a digestive enzyme that breaks down alpha-glucose bonds. So starches can be digested easily. Plants have alpha-amylase so they can harvest energy from starches in their seeds, roots, and tubers.
Very few organisms have cellulases – just some fungi and bacteria, earthworms, and a few insects can digest cellulase.

29. Proteins
Proteins make up most of the remaining biomass of living plant cells.
A protein consists of one or more polypeptides made up of amino acids. Plants make amino acids from the products of photosynthesis through a very complex process involving the acquisition of N, usually in the form of NH4, and involving the use of large amounts of energy, in the form of ATP and NADPH.

31. Structural Proteins
Structural proteins make up 2 to 10% of the cell wall in plants. Expansins help increase the surface area of cell walls. Extensins help protect or repair damaged cell walls. The plant cell membrane is about 50% structural proteins.

32. Storage Proteins
Storage proteins are used mostly in seeds and are used as source of nutrition for the early development of seedlings. Storage proteins used in seeds vary considerably between plant species. Corn produces a storage protein called ZEIN. Wheat produces a storage protein called GLIADIN

33. Corn Zein

34. Wheat Gliadin

35. Enzymes
Enzymes catalyze biochemical reactions. Most proteins in living cells are enzymes.
Pure enzymes that maintain their activity when removed from plants are commercially important to us.

36. Papaya – Papain and Chymopapain

37. Pineapple - Bromelain

38. Nucleic Acids
The most complex biological polymers are the nucleic acids that make up RNA and DNA. The basic content of bases (adenine, thymine, gaunine and cytosine) are similar in all plants

39. Lipids
Unlike other biological polymers, lipids are not defined by specific, repeating monomeric units. Rather they are defined by their water-repelling properties. The only structure they share is that they mostly are made up of nonpolar hydrocarbon groups (CH3, CH2, and CH).
Oils are fats that are liquid at room temperature.

41. Oils
Oils occur in all parts of a plant, but are most common in seeds. Some seeds have so much oil that it can be commercially harvested. The most commonly used oils are cotton, sesame, safflower, sunflower, olive, coconut, peanut, corn, castor bean, canola, and soybean oils.
The most common seed oil fatty acids are oleic acid (one double bond), linoleic acid (two double bonds), and linolenic acid (three double bonds). Linoleic and linolenic are essential fatty acids – we can’t make them ourselves.

42. Olive Oil

43. Canola Oil

44. Palm oil

45. Waxes
Waxes are complex mixtures of fatty acids linked to long-chain alcohols. Waxes that comprise the outermost layer of leaves, fruits, and herbaceous stems and are called EPICUTICULAR waxes. Waxes embedded in the cuticle of the plant are cuticular waxes. Cutin is another wax in the cuticle and it makes up most of the cuticle. Suberin is a similar wax that is found in cork cells in bark and in plant roots. Both help prevent water loss by the plant.
Structures of waxes vary depending on which plant produced them.
Waxes are usually harder and more water repellant than other fats.

46. Bayberry Wax

47. Euphorbia antisyphilitica

48. Candelilla wax

49. Jojoba Wax

50. Plant Secondary Metabolites
Plants make a variety of less widely distributed compounds such as morphine, caffeine, nicotine, menthol, and rubber. These compounds are the products of secondary metabolism, which is the metabolism of chemicals that occurs irregularly or rarely among plants, and that have no known general metabolic role in plants.
Secondary metabolites or secondary compounds are compounds that are not required for normal growth and development, and are not made through metabolic pathways common to all plants.
Most plants have not been examined for secondary compounds and new compounds are discovered almost daily.