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HSC Biology

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Lesson 3, Topic 1
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Comparing Different Types of Cells

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Unicellular
Algae and Fungi
Colonial
Parasites
Multicellular
Birds and Humans
Cellular FeaturesSingle-cellMany cellsMany cells
Cellular ClassificationsMostly prokaryotes; some eukaryotesEukaryotesEykaryotes
Cellular StructureOne cell carries out all the functions to sustain lifeIndividual animals; e.g. zooids work together to sustain the colonyFunctions are carried out at cellular, tissue, organ and system level
Cellular FunctionFunctions are carried out within the cellFunctions are carried out by individuals with specific roles in the colonyFunctions are carried out at a cellular, tissue, organ and system level
Microscopic or MacroscopicMicroscopic – SA:V limits the size of the cellUsually macroscopicMacroscopic; increasing the number of cells allows for an increase in body size
Life SpanShort lifespan due to high energy outputLong lifespanLong lifespan
Asexual or SexualMostly asexual: budding, mitosis, reproductionMostly asexual: mitosis, colonial reproductionMostly sexual
Reproductive SuccessThe whole organism is involvedUsually, specific zooids are responsible for reproductionOnly cells specialised for reproduction (gametes) will reproduce

Relating Structure and Specialisation to Function

OrganelleMembrane-bound compartment or structure in a cell that performs a special function.
e.g. mitochondria, vacuole
Specialised cellCells that have a specific function
e.g. root hair cell, lead guard cell
TissueA group of similar cells working together to carry out a specific function in multicellular organisms
e.g. muscle tissue, root tissue
OrganTwo or more tissues that work together to perform one or more specialised tasks
e.g. heart, liver, flowers, leaves
SystemA 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

CellStructure 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).