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IB Biology Extended Essay: Antimicrobial Activity of Essential Oils (Grade A)
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CELLS
Cell theory
1. All living things are made up of cells
2. Cells are the smallest unit of life
3. All cells come from pre-existing cells
Exceptions to the cell theory (Atypical examples)
1. Striated muscle tissue: Multinucleated, very large
2. Aseptate fungal hyphae: Large, multinucleated
3. Giant algae: Very lage, uninucleated
Functions of life
- MR. H GREN
● Metabolism: Sum of all enzyme catalysed reactions
● Reproduction: Division
● Homeostasis: Maintaining internal environmental conditions
● Growth: Enlargement based on consumption
● Response: To external environment
● Excretion: Removal of metabolic waste
● Nutrition: Synthesis of organic molecules or absorption of organic
matter
Surface area : Volume
★ Rate of metabolic reactions depends on the volume
★ Rate of excretion/absorption depends on the surface area
● Small cells = big SA:V = more efficient because every unit of volume
that needs nutrients or produces waste has more surface area
membrane
● Big cells = small SA:V = less efficient because every unit of volume
has less surface area membrane
- Big cells have slow rate of substance absorption and excretion
due to larger diffusion pathway and concentration gradient
, Differentiation
● It is the expression of some genes but not others in order to carry out
a specific function
● All cells of an organism contain the entire genetic information but only
express some genes
- Gene expression = differentiation
Reproduction
Occurs in order to….
1. Replace damaged or dead cells
2. Growth
● Reproduced cells go through the process of differentiation to produce
different cell types (with different functions)
Stem cells
● Initially unspecialized cells that can divide and differentiate into
different types to carry out different functions
Types of stem cells
1. Tultipotent: can differentiate into ANY cell type
2. Pluripotent: can differentiate into MANY cell types
3. Multipotent: can differentiate into a FEW CLOSELY RELATED cell
types
4. Unipotent: Can differentiate only into ASSOCIATED cell type
Magnification
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