Comparing Different Types of Cells
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| Unicellular Algae and Fungi | Colonial Parasites | Multicellular Birds and Humans | |
|---|---|---|---|
| Cellular Features | Single-cell | Many cells | Many cells |
| Cellular Classifications | Mostly prokaryotes; some eukaryotes | Eukaryotes | Eykaryotes |
| Cellular Structure | One cell carries out all the functions to sustain life | Individual animals; e.g. zooids work together to sustain the colony | Functions are carried out at cellular, tissue, organ and system level |
| Cellular Function | Functions are carried out within the cell | Functions are carried out by individuals with specific roles in the colony | Functions are carried out at a cellular, tissue, organ and system level |
| Microscopic or Macroscopic | Microscopic – SA:V limits the size of the cell | Usually macroscopic | Macroscopic; increasing the number of cells allows for an increase in body size |
| Life Span | Short lifespan due to high energy output | Long lifespan | Long lifespan |
| Asexual or Sexual | Mostly asexual: budding, mitosis, reproduction | Mostly asexual: mitosis, colonial reproduction | Mostly sexual |
| Reproductive Success | The whole organism is involved | Usually, specific zooids are responsible for reproduction | Only cells specialised for reproduction (gametes) will reproduce |
Relating Structure and Specialisation to Function
| Organelle | Membrane-bound compartment or structure in a cell that performs a special function. e.g. mitochondria, vacuole |
| Specialised cell | Cells that have a specific function e.g. root hair cell, lead guard cell |
| Tissue | A group of similar cells working together to carry out a specific function in multicellular organisms e.g. muscle tissue, root tissue |
| Organ | Two or more tissues that work together to perform one or more specialised tasks e.g. heart, liver, flowers, leaves |
| System | A group of organs that work together to perform a vital task |
Cell Specialisation and Differentiation
Specialisation is a specialised function for cell. Differentiation is the process where a cell changes from one type to another, typically an unspecialised cell becoming specialised.
Structure and Function of Specific Cells – Examples
| Cell | Structure Related to Function |
|---|---|
| Red blood cell | – Carry oxygen around the body – Thin outer membrane allows oxygen to diffuse – Shape increases SA:V which allows the oxygen to be absorbed more efficiently – No nucleus, leaving room for haemoglobin – Shape allows it to squeeze through vesicles and thin capillaries |
| Epidermal cell | – Has 2 layers to keep external and internal environments separate |
| Xylem cell | – Transports water and nutrients from the soil to stems and leaves – Provides mechanical support and storage – Internal hydrophobic surface facilitating water transport – Tracheids are hollow and connect to each other to improve transport efficiency – Think lignin coated cell walls provide shape and structure |
| Phloem cell | – Transport of sugars around the plant – Next to xylem for osmosis of water – Has a source and sink as transport for substance |
| Guard cell | – Multiple large vacuoles to absorb water – Multiple chloroplasts for photosynthesis – One thicker wall for stability and a thinner wall for differentiation – Close stomata when they lose potassium ions |
| Palisade mesophyll cells | – Found in the mesophyll of the leaf – The main function is light absorption – Multiple chloroplasts for photosynthesis |
| Root hair cell | – Extremely narrow tubes – Have thin hairs which protrude outwards, allowing an increase in SA: V for osmosis – Long and thin to penetrate between soil particles and prevent harmful organisms from entering the plant |
Cohesion is where water molecules stick together because they are attracted to each other due to their charges. Adhesion is where water molecules stick to a surface. Capillarity is where water molecules move up thin tubes (xylem).