Biology 3.3 Structure of an epithelial cell

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  • Created by: Anna
  • Created on: 14-04-13 20:45

Each cell type has an internal structure that suits it for its job = ultrastructure of the cell.

Epithelial cells = examples of eukaryotic cells.

Function of epithelial cells = absorb and secrete.

Nucleus

Most prominent feature of eukaryotic cell.

Contains hereditary material, controls the cells activities, usually spherical and between 10-20um.

  • Nuclear envelope = double membrane - outer membrane continuous with endoplasmic reticulum of the cell, often has ribosomes on its surface. Controls in and out of materials in nucleus, contains reactions that take place within nucleus.
  • Nuclear pores = allow passage of large molecules e.g. RNA, around 3000 pores in each nucleus.
  • Nucleoplasm = granular, jelly-like material, bulk of the nucleus.
  • Chromatin = DNA found within nucleoplasm -diffuse form of chromosomes.
  • Nucleolus = small spherical body within nucleoplasm, manufactures ribosomal RNA, assembles the ribosomes.

Functions of the nucleus are to:

  • Act as control centre through production of mRNA and hence protein synthesis.
  • Retain genetic material as DNA or chromosomes.
  • Manufacture ribosomal RNA and ribosomes.

The mitochondrion

Rod-shaped, made up of:

  • Double membrane, outer controlling in and out of material. Inner forms extensions known as cristae.
  • Cristae = shelf-like extensions of the inner membrane, some extend whole width of mitochondrion, provide large surface area for attachment of enzymes for respiration.
  • Matrix = remainder of mitochondrion, semi-rigid material containing protein, lipids and traces of DNA (allows mitochondria to control the production of their own proteins), enzymes involved in respiration found in the matrix.

Sites of certain stages of respiration.

Responsible for production of ATP from carbohydrates.

Number, size and number of their cristae increase in…

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