Cell Biology

The Cytoskeleton The cytoskeleton extends throughout the cytoplasm It organises cell structure and activities, anchoring many organelles in place It provides mechanical support, maintaining the cells shape: it?s domed in shape and stabilised by opposing forces It is also very dynamic, and can be dismantled and reassembled quickly, to change the shape of the cell Form The cytoskeleton is a network of fibres, the molecular structures include: Microtubules: the thickest of the fibres at 25nm (15nm lumen) Microfilaments: the thinnest of the fibres at 7nm Intermediate filaments: range in diameter from 8?12nm, larger than microfilaments but smaller than microtubules Roles

The Nucleus Functions of the nucleus Storage of genes on chromosomes Transportation of regulatory factors & gene products via nuclear pores Separation of: DNA from cytosol Transcription from translation Organisation of: genes into chromosomes (to allow cell division) uncoiling of DNA to replicate key genes Production of: messenger RNA ( mRNA ) that code for proteins ribosomal RNA (rRNA) in the nucleolus Components within the nucleus Nuclear envelope: double membrane, each membrane is a phospholipid bilayer Nuclear pore: controls entry and exit from the nucleus e.g. of RNA proteins Nuclear lamina: a series of structural proteins found on the inner membrane of the nuclear envelope, provide structural support Nuclear matrix: scaffold proteins Nucleoplasm: viscous medium