THE PROPERTIES AND FUNCTIONS OF THE CELL

Subject:

Biology

 

Class:

SS 1

 

Term:

First Term / 1st Term

 

Week:

Week 9

 

Topic:

THE PROPERTIES AND FUNCTIONS OF THE CELL

 

 

 

Previous Knowledge: The pupils have previous knowledge of

 

Micro and Macro Elements

 

that was taught in their previous lesson.

 

 

Behavioural  Objectives : At the end of the lesson, learners will be able to

  • Define cellular Respiration
  • Give examples of Cellular Respiration
  • Say the meaning of Excretion
  • Define Growth

 

 

Instructional Materials 

  • Wall charts
  • Online Resource
  • Textbooks
  • Sodium hydroxide, rubber bung, conical flask, potted plants, clamp, Vaseline
  • Laptop
  • Flash cards
  • Spirogyra fertilizers yeast and rat.
  • www.edudelighttutors.com

 

Methods of Teaching 

  • Role modelling
  • Questions and Answers
  • Explanation
  • Discussion
  • Recitation
  • Imitation
  • Story Telling
  • Dramatization

 

Content: 

THE PROPERTIES AND FUNCTIONS OF THE CELL

CONTENT

  1. Cellular Respiration
  2. Excretion
  3. Growth

 

Cellular Respiration

Respiration is the enzymatic breakdown of organic food substances, like glucose, through a series of chemical reactions in the cell to release energy and produce carbon (iv) oxide and water as by-products. Respiration occurs in all living cells.

Now, the energy released during respiration is used by the organism for such activities as synthesis of proteins, lipids and protoplasm; germination; cell division and enlargement leading to growth; movement; transmission of nerve impulses; active transport and maintenance of body temperature. There is variation in the amount of energy used by different organisms depending on their activities. A very active organism like a Tiger uses much more energy than a sluggish one, like a Chameleon.

The reactions that occur in cellular or tissue respiration are usually represented by the following equation:

C6H12O6 + 6O2 6CO2 + 6H2O + Energy
Glucose Oxygen Carbon
iv oxide
Water

The equation represents only a summary of the raw materials and the end products of tissue respiration. The complex pathway of cellular respiration is shown below:

Tissue respiration is divided into two main parts. The first is glycolysis, the stepwise series of reactions which leads to the breakdown of glucose to pyruvic acid. The process occurs in the cytoplasm in the cells. It consists of step-wise reactions, each brought about by specific enzymes. Glycolysis is common to, and occurs in the same general manner in all organisms.

Types of Respiration

You already know that we have external and internal respiration, while external deals with breathing in and out i.e. inhalation and exhalation, the internal which takes place in the cell hence, cellular respiration is divided into two basic parts:

  1. Anaerobic Respiration and
  2. Aerobic Respiration

Anaerobic respiration is that type which involves the use of very little or no Oxygen, while Aerobic Respiration is that type which involves the use of large amount of Oxygen.

Anaerobic Respiration

In anaerobic respiration, pyruvic acid is converted alcohol in plants and lactic acid in animals

Equation for lactic acid formation:

C6H12O6 2C3H6O3 + Energy

In plant cell, the products of anaerobic respiration are ethanol and carbon iv oxide. The formation of alcohol is represented by the equation:

C6H12O6 2C2H5OH + 2CO2 + Energy

This series of reactions convert glycogen in animals and starch in plants to glucose. The glucose is then converted by ten steps to pyruvic acid as below:

 

Converting Food to Usable Energy

Cellular respiration is a complex series of chemical reactions that harvests the energy trapped in the bonds of glucose sugar molecules and converts it into a chemical form that can be stored for later use. Humans and other animals obtain glucose sugar molecules from food, such as the fruits and grains shown here, while plants create glucose sugars in the process of photosynthesis. Essential to the survival of most organisms on Earth, cellular respiration yields the energy that makes our bodies function properly.

Aerobic Respiration

Aerobic respiration is a breaking down process known as catabolism, an aspect of metabolism. It is represented by the Kreb’s Cycle.  Diagram required.   In Kreb’s Cycle, for one molecule of pyruvic acid 15 molecules of ATP are produced. Since a molecule of glucose produce 2 molecules of pyruvic acid, therefore 30 molecules of ATP are produced from the the 2 molecules of pyruvic acid. Hence, a molecule of glucose produceds a total of 38 molecules of ATP during a complete aerobic respiratory process. The oxidation of glucose can thus be summarised with the following equation:

C6H12O6 + 6O2 6CO2 + 6H2O + Energy
Glucose Oxygen Carbon
iv oxide
Water

Another aspect of metabolism is Anabolism which is a building up process. An example is an aspect of plant nutrition commonly known as photosynthesis

 

 

 

Excretion

Definition of Excretion

Excretion is defined as the process by which living things eliminate waste products or toxic substances from their body through their excretory organs.

Excretory System of Some Organisms

ORGANISM EXCRETORY SYSTEM
Some unicellular organism Contractile Vacuole
Flatworms Flame cells
Annelids (e.g. earthworm) Nephridia
Insects Malpighian tubules
Vertebrates Kidneys, lungs, skin, and liver.
Plants Stomata and Linticels

 

Excretory Organs and Substances they Excrete in Vertebrates

In Animals

Lungs: Carbon (iv) oxide, and water vapour.

Skin: Sweats, salts and nitrogenous waste.

Kidney: Urea, excess water, excess salts, ammonium compounds, and acids.

Liver: Bile pigments.

In Plants

Stomata: Oxygen, Carbon (iv) oxide and water vapour.

Bark: Tannins, resins and latex.

Leaves: Crystals of calcium oxalate, calcium carbonate and anthocyanin pigments which give red, blue, and violet colours to many flowers.

Lenticels: Oxygen, Carbon (IV) oxide and vapour.

 

 

Growth

The Meaning of Growth

Growth is defined as an irreversible increase in size and mass due to formation of new protoplasm in the cell. Whenever the anabolic processes proceed at a faster rate than the catabolic process, there will be a supply of new substances to cause growth.

The three distinct processes that contribute to growth are cell division, cell enlargement and cell differentiation. In cell division, the nucleus and then the cytoplasm of the parent cell divide to form two daughter cells, then into four and so on bringing about an increase in the number of cells.

The daughter cells then increase in mass and size (i.e. enlarge) and eventually develop into a special type of cell (i.e. differentiate) by changing its shape and structure to carry out a particular function. The kind of cell it becomes depends on its position in the body of the organism. It may develop into a nerve cell in the brain, a muscle cell in the heart or a ciliated lining cell in the trachea.

Diagram of Root Tip Showing Apical Meristem

 

Root Tip Showing Apical Meristem

This lengthwise section of the tip of a plant root shows the apical meristem, which, with its rapidly dividing cells, is responsible for primary growth. Apical meristem can also be found at the tips of stems.

Basis of Growth

Cell division (mitosis) is the basis for growth in all multicelluar organisms. Mitosis is the cell division which occurs in the body cell (somatic cells) during which a parent cell divides to produce two daughter cells having the same number of chromosomes as itself.

Mitosis does not occur in all the cells of growing region of the organisms e.g. the root tips or shoot apices and cambium that undergo mitosis. These growing regions are described as meristems.

Cell division by mitosis occurs in four successive phases of continuous sequence namely prophase, metaphase, anaphase and telophase. Between the end of one mitosis and the commencement of a new mitotic division is a period described as interphase or pre-mitotic phase.

Interphase is not a resting time, but a period during which the young daughter cells accumulate and synthesize new body materials, thus preparing itself for the next division.

Diagram Showing the Growth of an Embryo

 

Spemann’s Experiments

The experiments of Hans Spemann in the early 1900s demonstrated the role of certain cytoplasmic signalling substances in the amphibian embryo. (Left): By cleaving the fertilized egg unnaturally, Spemann showed that an area called the gray crescent is essential to embryonic development. (Right): By the two-cell-layer (blastula) stage, the cells in the embryo have already been “mapped” to the structures they will form in the complete embryo. Spemann showed that if the embryo were cleaved at this point, only the section containing the dorsal lip of the blastopore (once the gray crescent area) would continue to develop.

The daughter cells synthesize new structures from the raw materials that they absorb from their surroundings. This process is called assimilation and results into cell enlargement. Cell differentiation also occurs as the cell develops into specialized cells.

An organism may be said to achieve growth when there is an increase in its dry weight, size or number of cells.

Factors Affecting Growth

These factors may be divided into external and internal factors. The external factors include the following:

  1. Nutrient availability: Body substances are synthesized from available nutrient materials and energy.
  2. Accumulation of toxic byproducts of metabolism may inhibit growth.
  3. Temperature: All biological processes including growth are accelerated as temperature rises from a minimum value at which no growth occur to a certain point beyond which retardation occurs.
  4. Light is essential for the growth of photosynthetic plants because it supplies the energy by which all new tissues are synthesised.
  5. PH: the Ph of the fluid in contact with a cell has a profound effect on all its activities. Some species grow best in a given PH range.
  6. The main internal factors controlling growth are hormones and enzymes.

 

 

 

 

Presentation: 

The topic is presented step by step

Step 1: The class teacher revises the old topic

Step 2: The class teacher introduces the new topic

Step 3: The class teacher allows the pupils to give their own contributions and gives room for pupils” participation

 

Class Teacher and Students Activities. Interaction or Participation 

This involves class teacher and pupils’ interaction, conversation, imitation or modeling through discussion, play method or just by recitation or asking and answering questions that are related to the topic that has just been taught.

 

Teacher Activities

1. The teacher introduces the subject biology and mentions the two major fields botany and zoology
2. List the steps involved in scientific methods
3. Prompt the students to elicit facts on the usefulness of biology

 

 

Students Activities.

1. Students listen attentively
2. State the steps involved in scientific methods after the teacher
3. Mention the usefulness of biology as a career

 

 

EVALUATION

  1. Explain the terms; Aerobic and anaerobic respiration.
  2. Discuss with a diagram the glycolytic pathway and Kreb’s cycle.
  3. State the following equations: respiration, lactic acid, and fermentation.

 

 

 

 

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