Organelles Flashcards
Describe the nucleolus.
The nucleolus is a dense, granular region within the nucleus containing some DNA, but mostly RNA. It is responsible for the manufacturing of ribosomes.
Command centre of head quarters.
Describe the nucleus.
The nucleus is a large, spherical structure found within the cytoplasm. It is colourless, transparent and very jelly-like. It is responsible for coordinating the activities of the cell.
Additionally, the nucleus is surrounded by a double nuclear membrane pierced with tiny pores which allow for the passage of substances between the nucleus and cytoplasm.
The headquarters of the cell.
Describe the endoplasmic reticulum (ER).
The endoplasmic reticulum is a network of flattened interconnected membranes found within the outer nuclear membrane. There is the “smooth ER” and the “rough ER.” The smooth ER is responsible for the production of lipids, while the rough ER is responsible for the transportation and processing of proteins.
Cellular highway.
Describe ribosomes.
Ribosomes are dense, rounded granules composed of RNA and protein. They carry out the genetically-coded instructions of DNA to produce proteins.
They can be found either floating freely in the cytoplasm or bound to rough endoplasmic reticulum.
Describe the Golgi apparatus.
The Golgi apparatus is a stack of flattened cisternae and associated vesciles responsible for processing, packaging and sorting cell products.
Post office.
Describe lysosomes.
Sphere-shaped sacs containing digestive enzymes that for break complex substances down into simpler substances. It is responsible for breaking down excess or worn out cell parts.
The digestive system of the cell.
What is apoptosis? How does it occur?
Apoptosis is programmed cell death. It is a deliberate action by the cell to destroy old and damaged cells.
Under the direction of the cell, the membrane of the lysosome ruptures, and the digestive enzymes leak out into the cell. These enzymes digest the contents of the cell, killing it in the process.
Describe the mitochondria.
Mitochondria are rod-shaped organelles with double membranes. They are the site of cellular respiration and are responsible for the production and storage of ATP (adenosine triphosphate).
Describe the components of mitochondria.
1) Outer membrane: gives the mitochondrion its shape and regulates the passage of substances coming in and out of the mitchondria.
2) Inner membrane: is folded into fine, finger-like ridges or cristae which increase the SA of the mitochondrion and allow for groups of enzymes responsible for the production of ATP to attach to it.
3) Matrix: contains mitochondrial DNA and enzymes that provide mitochondria with the ability to replicate themselves.
Describe vacuoles.
Vacuoles are large, permament, fluid-filled sacs found in mature plant cells. Each vacuole consists of a watery solution calledcell sap surrounded by a single membrane - tonoplast. Vacuoles are responsible for storage and support.
Explain how plant cells are able to become turgid.
As the vacuole fills up with water, it pushes outwards, exerting pressure on the cell wall. As a result of the outward pressure of the contents of the cell and the resistance of the cell wall, the plant cell becomes firm or turgid (a good thing!!)
Describe choloroplasts.
A chloroplast is a green, disc-shaped structure found in plant cells. It is green due to the presence of a pigment called chlorophyll. Choloroplasts are only found in the green tissue of plants that photosynthesise.
They belong under “plastids.” (the umbrella term): a class of organelles containing pigment or nutrients that vary in colour.
Identify and describe the components of chloroplast.
Chloroplast is surrounded by a double nuclear membrane. The liquid part is called “stroma.” The enzymes required in photosynthesis are found the stroma. Additionally, stacks of membranes containing chlorophyll called “thylakoids” are found. A stack/group of thylakoids is referred to as a “granum” (or plural: grana).
What does the stacking of thylakoids do for the choloroplast?
The stacking of thylakoids increases the surface area allowing for large amounts of sunlight to be absorbed for photosynthesis.
Describe the centrosome.
- Consists of 2 centrioles.
- Found near the nucleus in animal cells.
- Important for cell division and forming the mitotic spindle.
