1.1 Cell Theory PDF

Topic 1.1: Cell Theory Cell Theory Functions of Life According to the cell theory: Organisms consisting of only one cell carry...

Topic 1.1: 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 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 Cellular Organization Can show cross-sections (TEM) or surface renderings (SEM) In multicellular organisms: Cells may be grouped together to form tissues Emergent Properties Tissues may interact to form functional organs An emergent property is a function that is present in multicellular Organs may combine to form body systems 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