Some Properties And Functions Of The Cell SS1 Biology Lesson Note

MODE OF NUTRITION AND PLANT NUTRITION

1. AUTOTROPHIC NUTRITION    

Plants are referred to as autotrophs, i.e. being able to manufacture their food (Organic compound from inorganic materials such as water, and carbon dioxide)                                            

Autotrophs generally have two modes of nutrition which are chemosynthesis and photosynthesis (holophytic).

2. HETEROTROPHIC NUTRITION

This is a type of nutrition in which organisms depend directly or indirectly on autotrophs for food. All animals, fungi, protozoa and some bacteria belong to this group and they are referred to as heterotrophs 

HETEROTROPHIC MODES OF FEEDING

(a)    Holozoic Nutrition 

This is the mode of feeding in which food is ingested in the form of complex organic substances which are digested and assimilated into the body. Holozoic organisms are grouped into carnivores, herbivores, omnivores and scavengers.

(b)    Parasitic Nutrition 

This is the mode of feeding in which certain organisms (parasites) feed on other organisms (host). Parasites can be endoparasites (tapeworm, liver fluke) or ectoparasites (lice, ticks) depending on whether they live inside or outside the host. Plant parasites include dodder and mistletoe. Parasites have special structures such as haustoria, sucker, hooks, and muscular lips e. t. c. 

(c)     Saprophytic Nutrition 

This is a feeding process in which certain organisms (saprophytes) feed on non-living organic matter i. e. plant and animal remains. Saprophytes secrete digestive enzymes into the dead organic matter to digest the food (extracellular digestion) and the soluble food substances are then absorbed into their body. Examples include fungi i.e. mucor, mushroom, yeast and some bacteria 

(d)    Symbiotic Nutrition 

This is a mode of feeding in which two organisms of different species called symbionts live together and derive mutual benefits e.g. nutrients or food, shelter, moisture e. etc. c from each other. Examples are nitrogen-fixing bacteria called Rhizobia, which live in root nodules of legumes, algae and fungi in a lichen. 

(e)     Carnivorous / Insectivorous Nutrition

This is a feeding process in which some plants that have special devices trap and digest insects. These plants grow in poor soil and proteins obtained from the insects are used to supplement their nitrogenous compound requirement. These plants secrete enzymes which help in digesting their victim. Examples include bladderwort (Ultricularia), Pitcher plant, sundew and venus fly trap 

MODES OF AUTOTROPHIC NUTRITION    

Plants are referred to as autotrophs, i.e. being able to manufacture their food (Organic compounds from inorganic materials such as water, and carbon dioxide).                                            

Autotrophs generally have two modes of nutrition which are chemosynthesis and photosynthesis

1. PHOTOSYNTHESIS

This is the process by which green plants synthesize organic compounds from inorganic raw materials in the presence of chlorophyll and light.

light

    6C02 + 6H20                      C6H12O6            +         602

(Inorganic materials)          Chlorophyll     (organic compound)      (by-product) 

The main product of photosynthesis is sugar (carbohydrate) while the oxygen given up is a by-product which is released into the atmosphere.

 FEATURES (CHARACTERISTICS) OF PHOTOSYNTHESIS

These are as follows:

1. Photosynthesis occurs in the chloroplast of cells in the presence of light.
2. The raw materials required are low energy containing inorganic compounds i.e. CO2  and H2O
3.  The final product is a high energy-containing compound (C6H12O6 ) Photosynthesis, therefore is an anabolic process (metabolic building-up process)
4. The energy required is obtained from solar energy through the chlorophyll (the green pigment present in the chloroplast of green plants.

The carbon dioxide and oxygen diffuse in and out (respectively) between the surrounding air and leaf passing through the stomata opening on the leaf surface. These gases are stored in insoluble form until the day is dark. Then, the sugar is converted and transported to other parts of the plants where it is needed. The movement of the sugar is called translocation.

Leaf is the main photosynthetic organ of the plant although all green parts of a plant are photosynthetic. The main site of photosynthesis in a leaf is the palisade mesophyll.

IMPORTANCE OF PHOTOSYNTHESIS

The enzyme-rich product of photosynthesis is used by plants and animals in the following ways:

1. The source of energy for their metabolic activities 
2. It is needed in the food cycle being the only process that can trap sun energy.
3. All animals and other heterotrophic plants are directly or indirectly dependent on green plants for food.
4. Photosynthesis assists in the purification of the environment by removing carbon (iv) oxide from it while oxygen is released into it.
5. Basis for manufacturing other complex organic compounds such as lipids, proteins

2. CHEMOSYNTHESIS 

This is the process by which non-green plants (e.g. Nitrosomonas, Nitrobacter, iron bacteria etc) synthesize organic compounds from inorganic materials (carbon dioxide and water). The energy used in this process is obtained from inorganic substances such as ammonia and hydrogen sulphite.

H2S     +     O2                                        S        +        H2O      +     chemical energy

    chemical

H2O    +      CO2                                         CH2O

energy

MINERAL REQUIREMENTS OF PLANTS

Mineral elements are required for normal growth and development of green plants. In addition to Carbon, oxygen, and hydrogen, other mineral requirements are discussed below. Unlike glucose and other carbohydrates made from carbon dioxide and water by green plants, mineral salts are obtained from the soil. 

1. Macronutrients

These are mineral nutrients that are required by plants in large quantities. They include the following;

MICRONUTRIENTS

These are mineral nutrients required by plants in small quantities. They include the following;

ASSIGNMENT:

1. The main photosynthetic organ of the plant is —– (a) leaf (b) seed (c) fruit (d) root

2. Which of these is not a macro element needed for plant growth?    potassium                      B. magnesium     C. sodium     D. molybdenum
3. Yellowing of leaves is a symptom associated with deficiency of     iron, calcium and magnesium     B. nitrogen, sulphur and potassium     C. sulphur, phosphorus and iron     D. iron, magnesium and nitrogen
4. Trace elements are required by plants mainly for the     formation of pigments and enzymes    B. production of energy and hormones     C. manufacture of carbohydrates     D. manufacture of protein
5. The dark phase of photosynthesis occurs in the ——- of chloroplast (a) cells (b) tissues (c) fluid (d) stroma

6. What are macronutrients
7. b) List three macro elements that are essential for protein synthesis
8. What is autotrophic nutrition?
9. a) List the two modes of autotrophic nutrition.  (b) Differentiate between the two modes listed above.