Biology For Life Online
|
|
Biology For Life Online |
| Introduction | Lesson Plans | Answer Keys | Quarter Tests | Supplements | Ask a Question | My Seton | Home |
II. Cells: the Building Blocks of Physical Life
An organism is a form of life, such as plant or an animal or any living thing. Some organisms are very, very small. The very smallest organisms are called microorganisms. Most microorganisms (micro means too small even to be seen by the unaided eye) are unicellular, which means that they contain only one cell. Obviously, plants and animals that we commonly see are multicellular, or composed of many cells. Humans are multicellular because the human body contains trillions of cells. The complexity and the order and the functions of these trillions of cells are evidence of God's great intellect. To learn more about cells, go to www.kathimitchell.com/cells.html.
In 1665, Robert Hooke, an English scientist, examined a slice of cork under a microscope. Hooke noticed that the cork was composed of many small compartments. Hooke named these compartments "cells" because he thought that they resembled the little rooms, or cells, in a monastery. As you may recall from your reading of the lives of the saints, many monks lived in large monasteries but they slept or prayed in tiny rooms or cells, often with only a bed and a table.
The cork cells seen by Robert Hooke were nonliving. Hooke did not pursue the study of the structure and function of living cells. However, almost 200 years later, in 1835, the French biologist, Felix Dujardin, determined from his studies of organisms under a microscope that many living microorganisms are composed of a single cell. He also observed that the internal substance of all living cells was similar. You can find out more about Robert Hooke by going on the Internet to http://www.roberthooke.org.uk
Three years later, Matthias Schleiden, a German botanist, made the statement, based on his study and observations, that all plants are composed of cells. Shortly thereafter, a German zoologist, Theodor Schwann, concluded from his studies that all animals are composed of cells. Twenty years after Schleiden and Schwann, a German biologist named Rudolf Virchow observed cells under a microscope in the process of dividing, and concluded that cells can arise only from other cells. You can read a dramatic presentation which includes quotes from Rudolf Virchow at http://www.pathguy.com
The observations from these English, French, and German scientists formed the basis of The Cell Theory, which states:
The cell is the basic unit of structure of all living things. All living things are composed of cells or the products of cells.
The cell is the basic unit of function of living things.
All cells come from other cells by the process of cell division.
As tiny as cells are, it is truly amazing to study the several functions of these tiny cells. All cells require energy from food in order to perform their functions. Nutrition is the process by which organisms obtain and use food. Some cells are able to make their own food, while other cells must obtain food from their environment.
Cells obtain energy by processing food molecules (the smallest part of a substance) such as glucose molecules. The cell converts the energy of food molecules into a form of energy usable by the cell. This process of energy conversion is known as cellular respiration. Cells absorb water, minerals, and other materials which are essential to life from their environment. This process is called absorption.
Due to the processes of a cell, waste chemicals accumulate within a cell. Cells must eliminate, or excrete waste products into their environment because if these waste products were allowed to accumulate, they would poison the cell. The process of excretion is necessary for proper cell functioning.
One of the most amazing functions of all cells is that they are able to put together or make complex chemicals from simple chemicals in a process known as biosynthesis. For example, cells combine or synthesize complex protein cells from simple amino acids.
Cells can be flexible in their response to changes in their environment. Cells can respond to the conditions around them, and alter their functions in response to changes in their environment. Cells even replace themselves. Multicellular organisms must continually produce new cells to replace old worn-out cells.
Cell reproduction causes an increase in the number of cells in an organism, which results in the growth of an organism. Adults are larger than infants because they have grown and accumulated many more cells.
In conclusion, the tiny cell can make its own food, absorb materials necessary for its life, excrete waste products, make complex chemicals from simple chemicals, reproduce, and help an organism to grow. The truly profound functions of the tiny living cell prove the amazing intelligence of our almighty and loving God. No person or thing in the physical universe could ever have produced the amazing living cell.
