Eukaryotic Cell Structure

• Eukaryotic cells have a distinct nucleus and posess membrane-bound organelles.
• The nulceus contains the organism's hereditary material and controls the cells activites.
• The nucleus is usually spherical and is between 10 - 20 micrometers.
• The parts of the nucleus:

  • The nuclear envelope
  • Nuclear pores
  • Nucleoplasm
  • Chromosomes
  • Nucleolous
• The nuclear envelope is a double membrane that surrounds the nucleus.
• The nuclear envelope controls the entry and exit materials in an out of the nucleus and contains the reaction taking place within it.
• The nuclear envelope's outer membrane is continuous with the endoplasmic reticulum of the cell and often has ribosomes on its surface.
• Nuclear pores allow the passage of large molecules, such as messanger RNA, out of the nucleus.
• There are typically around 1000 nuclear pores, and are each 40 - 100 micrometers in diameter.
• Nucleoplasm is the granular, jelly-like material that makes up the bulk of the nucleus.
• The nucleolus is a small spherical region within the nucleoplasm.
• The nucleolus manufactures ribosomal RNA and assembles ribosomes.
• The Nucleus:

  A) Nuclear envelope

  B) chromatin

  C) nucleolus

  D) endoplasmic reticulum

  E) nuclear pores

  F) ribosomes

  
• Function of the nucleus: act as the control centre of the cell through the production of mRNA and tRNA and hence protein synthesis
• Function of the nucleus: retain the genetic material of the cell in the form of DNA and chromosomes
• Function of the nucleus: manufacture ribosomal RNA and ribosomes
• Mitochondria are usually rod-shaped and 1 - 10 micrometers in length.
• The structures of mitochondria:

  • Double membrane
  • Cristae
  • Matrix
• Around the mitochondria is a double membrane that controls the entry and exit material.
• The inner of the two membranes in the mitochondria is folded to form extensions called cristae.
• Cristae are extensions in the inner membrane, which in some species extend across the whole width of the mitochondrion.
• Cristase provide a large surface area for the attachment of enzymes and other proteins involved in respiration.
• The matrix contains protiens, lipids, ribosomes and DNA thhat allows the mitochondria to control the production of some of their own proteins.
• Many enzymes involved in respiration are found in the matrix.
• Mitochondria are the sites of the aerobic respiration.
• Mitochondria are responsible for the energy-carrier molecule, ATP, from respitory substrates.
• The mitochondria:

  A) matrix

  B) outer membrane

  C) cristae

  D) inner membrane

  
• Chloroplasts are the organelles that carry out photosynthesis.
• Chloroplasts vary in shape and size, but are typically disc-shaped.
• The parts of the chloroplast:

  • The chloroplast envelope
  • The grana
  • Thylakoids
  • The stroma
• The chloroplast envelope is a double plasma membrane that surrounds the organelle. It is highly selective in what it allows to enter and leave the chloroplast.
• The grana in chloroplasts are stacks of up to 100 disc-like structures called thylakoids.
• Within thylakoids, in the chloroplast, is the photosynthetic pigment called chlorophyll.
• Some thylakoids have tubular extensions that join up with thylakoids in adjacent grana.
• The grana is where the first stage of photosynthesis (light absorption) takes place.
• The stroma is a fluid-filled matrix where the second stage of photosynthesis (synthesis of sugars) takes place.
• Within the stroma, are a number of other strucutures, such as starch grains.
• Function of chloroplasts: harvest sunlight and carry out photosynthesis.
• Chloroplasts are adapted to their function: The granal membranes provide a large area for the attachement of chlorophyll, electron carriers and enzymes that carry out the first stage of photosynthesis.
• Chloroplasts are adapted to their function: The fluid of the stroma posesses all the enzymes needed to make sugars in the second stage of photosynthesis.