1.1 Cell Theory
1.1 Cell Theory
1.1 Cell Theory
1: Cell Theory
Cell Theory Functions of Life
According to the cell theory: Organisms consisting of only one cell carry
out all the life functions in that single cell
1. Living organisms are composed of cells (or cell products)
2. The cell is the smallest unit of independent life
• Metabolism
3. Cells can only arise from pre-existing cells
• Reproduction
• Sensitivity
Caveats to the cell theory include:
• Homeostasis
• Striated muscle – composed of fused cells that are multinucleated • Excretion
• Giant algae – unicellular organisms that are very large in size (~7 cm) • Nutrition
• Aseptate hyphae – lack partitioning and have a continuous cytoplasm • Growth
Cell Size
Surface area to volume ratio is important in the limitation of cell size Small SA:Vol Ratio
Cells need to exchange materials with the environment in order to produce ︎ metabolic rate
the chemical energy required for survival (via metabolism) ➡︎ material exchange
• The rate of metabolism is a function of a cell’s mass / volume Low survival chances
• The rate of material exchange is a function of a cell’s surface area
Large SA:Vol Ratio
As a cell grows, volume (units3) increases faster than surface area (units2) ➡︎ metabolic rate
• If metabolic requirements exceed material exchange, a cell will die ︎ material exchange
• Hence, cells must stay small or increase their SA:Vol ratio to survive High survival chances
Magnification Microscopes