University:
Felician University
Course:
BIO-102 | Human Biology
Academic year:

2019
Views:

194

Pages:

1
Author:

5CelestialChronicle

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 3. Cells can only arise from pre-existing cells Caveats to the cell theory include: • Striated muscle – composed of fused cells that are multinucleated • Giant algae – unicellular organisms that are very large in size (~7 cm) • Aseptate hyphae – lack partitioning and have a continuous cytoplasm • • • • • • • Metabolism Reproduction Sensitivity Homeostasis Excretion Nutrition 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 the chemical energy required for survival (via metabolism) • The rate of metabolism is a function of a cell’s mass / volume • The rate of material exchange is a function of a cell’s surface area ⬆︎ metabolic rate ⬇︎ material exchange As a cell grows, volume (units3) increases faster than surface area (units2) • If metabolic requirements exceed material exchange, a cell will die • Hence, cells must stay small or increase their SA:Vol ratio to survive ⬇︎ metabolic rate ⬆︎ material exchange Low survival chances Large SA:Vol Ratio High survival chances Magnification Microscopes Calculating Magnification (MIA): Light microscopes use lenses to bend light Magnification = Image Size ÷ Actual Size • • Can view living specimens in natural colour Have lower magnification and resolution Calculating Actual Size (AIM): Electron microscopes use electromagnets to focus electrons Actual Size = Image Size ÷ Magnification • Can only view dead specimens in monochrome • Have higher magnification and resolution • Can show cross-sections (TEM) or surface renderings (SEM) Cellular Organization In multicellular organisms: • Cells may be grouped together to form tissues • Tissues may interact to form functional organs • Organs may combine to form body systems Emergent Properties An emergent property is a function that is present in multicellular organisms, but is not present in its individual component cells Emergent properties arise from synergistic interactions between the individual cells to produce entirely new aggregate functions An example of an emergent property is the increased levels of antibiotic resistance that can be seen in bacterial biofilms Muscle Cardiac Heart Vascular (Cell) (Tissue) (Organ) (System) ‘The whole is greater than the sum of its parts’ – Aristotle