Classwork Series and Exercises {Biology- SS1}: Major Sources and Forms of Energy

Introduction To Energy

Energy is the ability to do work. Work is done when force causes an object to move through a distance. All living organisms need energy to enable them to carry out their life processes. This energy is normally obtained from the food we eat.

Forms of Energy

There are many forms of energy. Some of them are as follow:

1. Kinetic energy or energy in a moving object
2. Potential energy or stored energy
3. Light energy
4. Sound energy
5. Heat energy
6. Electrical energy
7. Chemical energy or energy stored in chemical substances. Energy-rich carbon substances are called fuels. Coal, petrol and kerosene are common fuels. They release energy when they are burned in air (oxygen). Food is also an energy-rich carbon substance, and so is known as the fuel of living things.

Energy Requirements of Biological Activities

Energy is used up for the following activities:

1. Muscular Activities: Potential energy is converted into kinetic energy and finally into heat energy during physical activities like sporting, trekking, fighting etc.
2. Active Transport: Energy is used up in form of kinetic energy in body processes like diffusion and osmosis during the movement of materials like digested food or waste products.
3. Production of heat: Energy transformation from chemical to mechanical is bound to produce heat. E.g. as in tissue respiration
4. Metabolic processes: Energy is required in the course of anabolism since simple molecules are built into complex forms.
5. For Growth: Energy is also required by organisms for the multiplication of cells which give to young ones.

Major Sources of Energy

The sun is the ultimate source of energy. Biological energy is therefore derived from sunlight which is trapped by chlorophyll, i.e., the green pigments of the leaves. The energy so trapped is used to manufacture their food through a process called photosynthesis.

Other sources are derived from plants after photosynthesis in form of food, wood, fuel (crude oil, coal and natural gas), fats etc.

Energy Transformation

Energy can be changed from one form to another. This can be illustrated as follow:

1. Potential energy to kinetic energy and back to potential energy when a static object is forced to move and after which it stops.
2. Chemical energy to mechanical energy and finally to heat energy, as found in tissue respiration.
3. Solar energy converted to heat energy for boiling or melting materials in factories.
4. Conversion of chemical energy into light as in AC and DC batteries, as well as firefly.

Law of Thermodynamics

Thermodynamics ordinarily means heat changes. Heat is a form of energy and how it can be changed in living organisms is governed by two laws. These laws are called first and second laws of thermodynamics.

First Law of Thermodynamics: States that energy can neither be created nor destroyed but can be changed from one form to another. For example, chemical energy in food can be converted to kinetic energy and heat energy in our muscles when we walk or run.

Second Law of Thermodynamics: States that when energy is converted from one form to another, it is not always 100 percent efficient; heat is lost along the line. During transformation of energy, there is always a decrease in the amount of useful energy.

Plant Nutrition

Nutrition is the supply of food to the cells of organisms in order that they can grow as well as repair and replace worn-out tissues. It also aids respiration.

This is one of the main characteristics of living things i.e. the ability to feed. Both plants and animals feed. While some organisms called autotrophs can manufacture their own food, other organisms called heterotrophs cannot. Therefore, most autotrophs can manufacture their own food through a process called photosynthesis.

Photosynthesis

Photosynthesis is defined as the process by which green plants manufacture their food (organic compounds) making use of carbon dioxide and water in the presence of sunlight. In other word, photosynthesis is the process by which green plants, use the energy from sunlight to produce sugar(glucose), which cellular respiration converts into ATP, the “fuel” used by all living things. The conversion of unusable sunlight energy into usable chemical energy is associated with the actions of the green pigment chlorophyll. Most of the time, the photosynthetic process uses water and release the oxygen that we absolutely must have to stay alive.

Chemical equation of this process is:

6H₂O      +      6CO₂        ———->     C₆H₁₂O₆+      6O₂

_{(water)             (carbon dioxide)               (glucose)               (oxygen)}

From the chemical equation above, water combines with carbon dioxide in the presence of sunlight within the chlorophyll of leaves to manufacture food (glucose) and oxygen is liberated as a by-product. Photosynthesis occurs in all green parts of plants and it takes place primarily in plant leaves, and little to none occurs in stems

Mechanism of Photosynthesis

Photosynthesis is an endothermic reaction. These reactions during photosynthesis are grouped into two stages called light reaction and dark reaction.

Light Reaction Stage

Light reaction stage occurs during the day or in the presence of sunlight. The chlorophyll traps the light energy. The energy further splits the water into hydrogen (H⁺) and hydroxyl (OH^–) ions in what is referred to as photolysis.

                          4H₂O  ——–>  4H⁺   +    4(OH^–)   +   ATP

The hydroxyl (OH^–) is reconverted to water and oxygen

4(OH^–)   ——–>     2H₂O   +   O₂

During this process, oxygen is given out as by-product as shown in the chemical equation above. At the same time, a compound, co-enzyme (NADP) is reduced by hydrogen ion to NADPH and ATP (Adenosine Triphosphate) is formed.

Dark Reaction Stage

Dark reaction occurs at night or in the absence of light. The reaction takes place in the presence of enzymes. The hydrogen atoms are added to carbon (IV) oxide to form simple sugars.

                   CO₂   +     2H₂   ———–>    CH₂O   +   H₂O

Significance of Photosynthesis

1. The end-product of photosynthesis – starch, sustains life as well as supplies the needed energy for all animals and non-green plants.
2. The use of carbon (IV) oxide by plants during photosynthesis helps in purifying the atmosphere.

Condition Necessary for Photosynthesis

For photosynthesis to take place, certain materials or conditions must be available:

1. Carbon (IV) oxide
2. Water
3. Chlorophyll
4. Sunlight
5. Minerals
6. Enzymes

Importance of Photosynthesis

1. Photosynthesis is very important both to plants and animals for the following reasons:
2. Production of food
3. Purification of the atmosphere
4. Release of oxygen to the environment
5. It serves as building blocks for other substances.

Chemosynthesis

This is the use of energy released by inorganic chemical reactions to produce food. This is an alternate way to generate energy and make sugars to photosynthesis. Instead of using light as the energy source, chemosynthetic organisms use some chemical as the energy source. Typical chemicals for this are hydrogen sulfide, hydrogen or ammonia. Chemosynthesis is at the heart of deep-sea communities, sustaining life in absolute darkness, where sunlight does not penetrate.

CO₂ + 4H₂S + O₂  ——->  CH₂0 + 4S + 3H₂O

EXERCISES

Lets see how much you’ve learnt, attach the following answers to the comment below

1. During which of the following processes is food for animals produced? (a) photosynthesis (b) respiration (c) nutrition (d) transpiration
2. Which of the following is an autotrophic mode of nutrition? (a) chemosynthesis (b) saprophytism (c) parasitism (d) symbiosis
3. Autotrophic nutrition may be defined in terms of food obtained (a) from other organisms in exchange for some products (b) by the breakdown of complex substances (c) by an organism utilizing its own store of energy (d) by synthesizing simple substances using energy from an external source
4. Which of the following does not occur during photosynthesis? (a) energy from sunlight is absorbed (b) carbon dioxide is evolved (c) glucose is synthesized (d) oxygen is given off
5. Even though some flowering plants contain accessory pigments which give them colours they still contain the pigment (a) melanin (b) chlorophyll (c) xanthophylls (d) carotene

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