Organelles
Organelles are the discrete subunits of a cell that are adapted to perform specific functions
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The plasma membrane and ribosomes are universal organelles that are present in every living cell
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Complex cells (eukaryotes) possess additional membrane-bound organelles that provide further functionality
Types of Organelles
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Nucleus
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The nucleus is a double membrane structure with pores that stores the genetic material (DNA)
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Within the nucleus, a specific region called the nucleolus is responsible for ribosome assembly
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Mitochondria
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Mitochondria are responsible for ATP production via the process of aerobic cell respiration
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It has an inner membrane that is highly folded into cristae in order to increase the SA:Vol ratio
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Endoplasmic Reticulum
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The ER is a membranous network that synthesises and transports materials via vesicles
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The smooth ER synthesises lipids, while the rough ER synthesises proteins (via ribosomes)
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Golgi Complex
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The golgi apparatus is an assembly of folded membranes responsible for material secretion
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Material is sorted, stored, modified and exported from the cell within vesicles (exocytosis)
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Vesicles
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Vesicles are membranous containers involved in the transport and storage of materials
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Peroxisomes are involved in the oxidation of lipids and the digestion of toxic metabolites
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Lysosomes are responsible for the breakdown of cellular wastes and pathogenic debris
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Vacuoles are comparatively larger containers that store excess fluid and regulate pH
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Chloroplast (plants)
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An organelle responsible for photosynthesis (converting light energy into chemical energy)
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Chloroplasts use the photosynthetic pigment chlorophyll to absorb and utilise light energy
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Centrosome (animals)
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Centrosomes function as microtubule-organising centres composed of paired centrioles
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They contribute towards cell division in animal cells (plants and fungi use other structures)
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Nucleus
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Double membrane structure that stores genetic material / DNA
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A nucleolus is a dark region in a nucleus that makes ribosomes
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Mitochondria
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Responsible for ATP production (via aerobic cell respiration)
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The inner membrane is highly folded to increase SA:Vol ratio
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Endoplasmic Reticulum
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A membranous network that transports materials via vesicles
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Smooth ER synthesises lipids ; rough ER synthesises proteins
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Golgi Complex
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An assembly of folded membranes used for material secretion
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Material is sorted, stored, modified and exported from the cell
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Vesicles
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Membrane sacs involved in transport and storage of material
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Peroxisomes are involved in the digestion of toxic metabolites
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Lysosomes are responsible for breaking down cellular wastes
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Vacuoles are comparatively larger sacs that store excess fluid
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Chloroplast (plants)
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Structure responsible for photosynthesis (in plant cells only)
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Uses the pigment chlorophyll to absorb and utilise sunlight
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Centrosome (animals)
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Microtubule-organising centre composed of paired centrioles
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Contributes towards mitotic cell division (in animal cells only)
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Exceptions
Certain cellular components are not considered to be organelles:
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Cell walls are not considered organelles as they are extracellular components
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Cytoskeletons and cytosol are categorised as structural elements as opposed to distinctive organelles