Cell:The Basic Unit of Life

​Cell: The Basic Unit of Life

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• Cells are the smallest functional units in living things.

• Cells were discovered with the use of a microscope.​

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• In 1665, an English scientist named Robert Hooke cut a thinslice of cork and looked at it under the

  microscope. He described the image of

  the cork as empty boxes, which he

  called cells.​

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• In the 1830s, Matthias Schleiden, a German scientist, used a microscope to study plant cells and concluded that plants are made of cells.

• ​A year after this discovery, another German scientist, Theodore Schwann, observed different animal cells and concluded that all animals are made of cells.

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• The food you eat is made of substances that your body needs to stay healthy and strong.

  These substances are the nutrients that provide energy and materials for cell development,

  growth, and repair.

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• Nutrients are sources of energy that the cells and the different parts of your body use to accomplish your tasks. Your body can best grow, develop, and heal you provide it with proper nutrition.

​Technology Integration

Stem cell technology is a field of medical research concerned with human and animal stem cells.

Stem cells are naturally occurring cells essential to the growth and regeneration of organisms. Bone marrow transplant as a common treatment for leukemia patients is one application of stem cell technology.

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Parts of a Cell

The most readily observable parts of a cell are its membrane, nucleus, and cytoplasm

(Figure 1.1). The plasma membrane is a semipermeable membrane surrounding the cell. It controls the kind of substance that enters the cell, particularly in the process of taking in water and nutrient. The plasma membrane also allows discharge own waste materials. The nucleus controls the activity of the cell. It contains the chromosomes, which are threadlike DNA-containing structure. The cytoplasm is jellylike substance that contains the organelles.​

Organelles are specialized parts of the cell that are analogous to organs. Each organelle carries out specific functions in the cell. Some of these organelles are listed in Table

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​Table 1.1 Some Organelles in a Cell and their Functions

Organelle Function

endoplasmic reticulum - a network of sacs that manufactures, processes, and transports chemical compounds for use inside and outside of the cell.

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golgi apparatus - a cell organelle that helps process and package proteins and lipid molecules, especially proteins destined to be exported from the cell.

mitochondria cell organelles that generate most of the chemical energy needed to

power the cell's biochemical reactions

vacuole an organelle in cells which functions to hold various solutions or

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​Table 1.1 Some Organelles in a Cell and their Functions

Organelle Function

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golgi apparatus - a cell organelle that helps process and package proteins and lipid molecules, especially proteins destined to be exported from the cell.

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Organelle Function

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mitochondria cell - organelles that generate most of the chemical energy needed to power the cell's biochemical reactions.

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vacuole - an organelle in cells which functions to hold various solutions or materials.

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Organelle Function

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mitochondria cell - organelles that generate most of the chemical energy needed to power the cell's biochemical reactions.

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Organelle Function

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vacuole - an organelle in cells which functions to hold various solutions or materials.

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Organelle Function

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nucleolus - a round structure in the nucleus that makes ribosomes.

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lysosome - stores enzymes for the digestion of carbohydrates, fats, and proteins

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Organelle Function

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ribosome - Acts as a protein assembler​.

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​Both plant and animal cells are eukaryotic, that is, their nuclei are membrane-bound.

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But plant cells have parts that are not present in animal cells. Plant cells have cell walls made of cellulose that protect, support, and give them shape. They also have chlorophyll, the green pigment essential in photosynthesis.

Animal cells, on the other hand, have centrioles, which play an important role in cell division.

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A plant cell has a large vacuole that stores nutrients and other substances for plant growth.

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An animal cell may have one or more small vacuoles that temporarily store water and wastes.