Parts of a Cell
Centrioles are cylindrical structures that are composed of groupings of microtubules arranged in a 9 + 3 pattern. The pattern is so named because a ring of nine microtubule "triplets" are arranged at right angles to one another. Centrioles are found in animal cells and help to organize the assembly of microtubules during cell division. Centrioles replicate during the interphase stage of mitosis and meiosis. Centrioles called basal bodies form cilia and flagella.
Mitochondria provide the energy a cell needs to move, divide, produce secretory products, contract - in short, they are the power centers of the cell. They are about the size of bacteria but may have different shapes depending on the cell type.
Cytosol: The cytosol is the "soup" within which all the other cell organelles reside and where most of the cellular metabolism occurs. Though mostly water, the cytosol is full of proteins that control cell metabolism including signal transduction pathways, glycolysis, intracellular receptors, and transcription factors. Cytoplasm is a collective term for the cytosol plus the organelles suspended within the cytosol.
Cell walls are rigid (up to many micrometers in thickness) and give plant cells a very defined shape. While most cells have a outer membrane, none is comparable in strength to the plant cell wall. The cell wall is the reason for the difference between plant and animal cell functions. Because the plant has evolved this rigid structure, they have lost the opportunity to develop nervous systems, immune systems, and most importantly, mobility.
The chloroplast is made up of 3 types of membrane:
A smooth outer membrane which is freely permeable to molecules.
A smooth inner membrane which contains many transporters: integral membrane proteins that regulate the passage in an out of the chloroplast of
small molecules like sugars
proteins synthesized in the cytoplasm of the cell but used within the chloroplast
A system of thylakoid membranes
Golgi apparatus – works with endoplasmic reticulum as a molecular warehouse/finishing factory. It acts as a receiving dock for transport vesicles.
Smooth endoplasmic reticulum – a network of interconnected tubes that lack ribosomes and are used for synthesizing lipids.
Lysosome – membrane containing digestive (hydrolytic enzymes)
nuclear membrane – The double membrane of the nucleus enclosing DNA and any other genetic material in a eukaryotic cell is called the nuclear membrane.
Ribosome – assemble amino acids into polypeptides
Cell (Plasma) Membrane - prokaryotic and eukaryotic, have a plasma membrane that encloses their contents and serves as a semi-porous barrier to the outside environment. The membrane acts as a boundary, holding the cell constituents together and keeping other substances from entering. The plasma membrane is permeable to specific molecules, however, and allows nutrients and other essential elements to enter the cell and waste materials to leave the cell. Small molecules, such as oxygen, carbon dioxide, and water, are able to pass freely across the membrane, but the passage of larger molecules, such as amino acids and sugars, is carefully regulated.
Plastid - the organelles in plants and algae in which photosynthesisoccurs. They also are critical in starch and other product storage, and in the synthesis of fatty acids, terpenes, and other molecules used as cellular building blocks and critical components to plant function. Plastids are divided into several types depending on morphology and function: chloroplasts, leucoplasts, amyloplasts, and chromoplasts. One plastid may have the ability to morph into another type of plastid.
Nucleus - a membrane-bound organelle and is surrounded by a double membrane. It communicates with the surrounding cytosol via numerous nuclear pores. Within the nucleus is the DNA responsible for providing the cell with its unique characteristics. The DNA is similar in every cell of the body, but depending on the specific cell type, some genes may be turned on or off - that's why a liver cell is different from a muscle cell, and a muscle cell is different from a fat cell. When a cell is dividing, the DNA and surrounding protein condense into chromosomes that are visible by microscopy.
Vacuole - A vacuole is a membrane-bound sac that plays roles in intracellular digestion and the release of cellular waste products. In animal cells, vacuoles are generally small. Vacuoles tend to be large in plant cells and play a role in turgor pressure. When a plant is well-watered, water collects in cell vacuoles producing rigidity in the plant. Without sufficient water, pressure in the vacuole is reduced and the plant wilts.
Cilia and Flagella
These whip-like appendages extend from the surface of many types of eukaryotic cells.
- If there are many of them, they are called cilia;
- if only one, or a few, they are flagella. Flagella also tend to be longer than cilia but are otherwise similar in construction.
Rough endoplasmic reticulum - an interlinked network of cisternae (membrane disks), vesicles (intracellular transport sacs) and tubules inside a eukaryotic cell
Cytoskeleton - a cellular "scaffolding" or "skeleton" contained within the cytoplasm and is made out of protein.
Nucleolus - produces ribosomes, which move out of the nucleus to positions on the rough endoplasmic reticulum where they are critical in protein synthesis.
Chromosomes - an organized building of DNA and protein that is found in cells. It is a single piece of coiled DNA containing many genes,regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.
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