Biology is the branch of science that deals with the study of living systems and life processes.
A. Cells
Cells are the most basic units that compose all living systems. They are responsible for the structure and function in living things. All living systems are composed of cells.
Organelles are structures with specific functions found within living cells. Examples of these structures are the nucleus, cell wall/cell membrane, cytoplasm, lysosome, and vacuole. These structures are essential for the cell to function properly.
Nucleus
The nucleus is arguably the most important structure in the cell because it serves as the control center in which individual functions of the other organelles are coordinated.
Cell Wall/Cell Membrane
The cell wall in plant cells provides rigidity for support, and the cell membrane is selectively permeable.
Mitochondrion
This organelle is also called the "powerhouse of the cell". It serves as the site where ATPs are synthesized.
Differences Between Plant and Animal Cells
Plants:
Cell wall present
Chloroplast present
Centriole absent
One large mitochondrion
And other organelles
Animals:
Cell wall absent
Chloroplast absent
Centriole present
Many small mitochondria
And other organelles
How Did the Concept of the Cell Come About?
The Cell Theory serves as the basis on which everything that we know about the cell is anchored. The three elements of this theory are:
- All living things are made up of cells.
- Cells are the basic unit of structure and function in living systems.
- All cells come from preexisting cells.
The cell is composed of biomolecules that are intricately combined to enable the cell to perform its metabolic functions—biomolecules such as carbohydrates, fats/lipids, proteins, and nucleic acids.
Cells According to Complexity
Prokaryotic Cells:
No membrane-bound nucleus and organelles
Typical of bacteria and blue-green algae
Eukaryotic Cells:
Membrane-bound nucleus and organelles
Typical of protests, fungi, plants, and animals.
Cell Transport
Passive Transport:
Does not require the expenditure of energy
Moves particles through the concentration gradient.
Active Transport:
Requires the expenditure of energy
Moves particles against the concentration gradient.
Diffusion:
Molecules of solvent move from an area of high concentration to an area of low concentration.
Osmosis:
Refers to the diffusion of particles or molecules across a selectively permeable membrane.
Cell Reproduction
Cell reproduction involves the process by which cells divide to produce daughter cells. It involves either mitosis if somatic or body cells are involved or meiosis if germ or sex cells are involved.
Mitosis:
Division of the somatic cells
Also referred to as equational division because the ploidy number of the daughter cells is equal to the ploidy number of the dividing cell.
Meiosis:
Division of germ cells
Also referred to as reductional division because the ploidy number of the daughter cells is only half that of the parent cell.
B. Botany
Plants are autotrophic organisms capable of synthesizing their own food for growth and maintenance through the process of photosynthesis. Their cells are eukaryotic and are distinguished by the presence of cellulosic cell walls, plastids, and large vacuoles. Plant cells may also contain non-living inclusions called ergastic substances that are products of the cell's metabolism.
