Chapter 2- 2.4- Eukaryotic cell structure Flashcards
What is the cytoskeleton?
A network of fibres necessary for the shape and stability of a cell.
Organelles are held in place by the cytoskeleton and it controls cell movement and the movement of organelles within cells.
What are the 3 components of the cytoskeleton?
Microfilaments-
Contractile fibres formed from the protein actin.
These are responsible for cell movement and also cell contraction during cytokinesis, the process in which the cytoplasm of a single eukaryotic cell is divided to form two daughter cells.
Microtubules-
Globular tubulin proteins polymerise to form tubes that are used to form a scaffold-like structure that determines the shape of the cell.
They also act as tracks for the movement of organelles, including vesicles, around the cells.
Spindle fibres, which have a role in the physical segregation of chromosomes in cell division, are composed of microtubules.
Intermediate fibres- These fibres give mechanical strength to cells and help maintain their integrity.
What is the interrelationship between the organelles involved in the production and secretion of protein?
Proteins are synthesised on the ribosomes bound to the endoplasmic reticulum.
They then pass into its cisternae and are packaged into transport vesicles.
Vesicles containing the newly synthesised proteins move towards the Golgi apparatus via the transport function of the cytoskeleton.
The vesicles fuse with the cis face of the Golgi apparatus and the protein enter.
The proteins are structurally modified before leaving the Golgi apparatus in vesicles from its trans face.
Secretory vesicles carry proteins that are to be released from the cell. The vesicles move towards and fuse with the cell-surface membranes, releasing their contents by exocytosis. Some vesicles form lysosomes- these contain enzymes for use in the cell.
Explain cells
The basic unit of all living things is the cell- but not all cells are the same. There are two fundamental types of cells- prokaryotic and eukaryotic.
Prokaryotic are single-celled organisms with a simple structure of just a single undivided internal area called the cytoplasm (composed of cytosol, which is made up of water, salts and organic molecules).
Eukaryotic cells make up multicellular organisms like animals, plants and fungi.
Eukaryotic cells have a much more complicated internal structure, containing a membrane- bound nucleus (nucleoplasm) and cytoplasm.
Where do reactions take place inside the cell?
In the cytoplasm.
The cell cytoplasm is separated from the external environment by a cell-surface membrane.
In eukaryotic cells the cytoplasm is divided into many different membrane-bound compartments, known as organelles.
These provide distinct environments and therefore conditions for the different cellular reactions.
Membranes are selectively permeable and control the movement of substances into and out of the cell and organelles. Membranes are effective barriers in controlling which substances enter and exit cells but they are fragile.
