EUKARYOTE CELL ULTRASTRUCTURE 2016 Paul Billiet ODWS Primary

Primary Cell Structure That which can be seen using the light microscope. © 2016

Ultrastructure That which can be observed under the electron microscope. Transmission electron micrograph (TEM)

EUKARYOTE CELL ULTRASTRUCTURE ORGANELLE MAIN FUNCTIONS DIMENSIONS Nucleus Cell division, protein synthesis 10 µm diameter Mitochondrion Respiration pathways 1. 0 to 12. 5 µm Chloroplast Photosynthetic pathways Lysosome Digestion, recycling & isolation Golgi apparatus Secretion, reprocessing, lysosome synthesis Cisternae: 0. 5µm thick, l-3µm diameter Endoplasmic Reticulum (ER) Support, Golgi apparatus synthesis 26 to 56 nm thick Ribosome Protein synthesis © 2016 Paul Billiet ODWS 5 to 10 µm diameter 0. 5 to 3. 0 µm diameter 20 nm diameter

NUCLEUS (latin kernel) TEM Nucleus of a rat hepatocyte © 2016 Paul Billiet ODWS

NUCLEUS (pl nuclei) 10 µm Usually spherical, occupying up to 75% of the cell

NUCLEUS Chemical composition �Protein: Up to 90%, HISTONES rich in basic amino acids. �Deoxyribonucleic Acid (DNA) about 20% �Ribonucleic Acid (RNA) 5 to 20% �Nuclei usually contain about 10% CHROMATIN = Histone + DNA = NUCLEOPROTEIN. © 2016 Paul Billiet ODWS

NUCLEUS Functions �Main site of DNA in eukaryotic cells �Preservation, replication and expression of genetic information �It makes RNA for protein synthesis �It copies DNA for cell division. © 2016 Paul Billiet ODWS

MITOCHONDRION (gk mitos = thread khondrion = granule) TEM of mitochondrion from mouse kidney

MITOCHONDRION (pl. mitochondria) Cristae Inter membrane space outer membrane Mitochondrial envelope inner membrane 1.

MITOCHONDRION Pigments Cytochromes Functions � The mitochondria are closely associated with the pathways of respiration � These metabolic pathways are divided up and supported by the membranes � The inner membrane contains the enzyme necessary for the synthesis of Adenosine Triphosphate (ATP). © 2016 Paul Billiet ODWS

CHLOROPLAST (Gk chloros = green plast = form or shape) TEM chloroplast botit. botany.

CHLOROPLAST Grana Thylakoid membrane Frets Chloroplast envelope outer membrane inner membrane Stroma © 2016

CHLOROPLAST Pigments Mainly chlorophylls with carotenoids and others Function: Photosynthesis The metabolic pathways are closely associated with the membranes as in the case of the mitochondrion. © 2016 Paul Billiet ODWS

Organelles and evolution �Both chloroplasts and mitochondria are double membrane bound �They involved in energy reactions �They contain extranuclear DNA and characteristic small ribosomes of their own �This has led biologists to believe that there may be some similarity in their origins in the cells of eukaryotes �The endosymbiotic theory. © 2016 Paul Billiet ODWS

LYSOSOME cellbio. utmb. edu/cellbio/lys 2. jpg © 2016 Paul Billiet ODWS

LYSOSOME �Not discovered by electron microscopy but by centrifugation and enzyme analysis �Not present in plant cells Structure: Simple, spherical, single membrane bound Lysosomes contain a large number of CATABOLIC enzymes. © 2016 Paul Billiet ODWS

Enzymes found in lysosomes ENZYME SUBSTRATE Acid phosphatase Phosphate esters Acid ribonuclease RNA Acid deoxyribonuclease DNA Glycosidases Polysaccharides Protease Proteins and peptides Lipase Lipids Phospholipase Phospholipids More than 40 types of enzymes are known to occur in lysosomes. © 2016 Paul Billiet ODWS

LYSOSOME Function �Digestion of compounds taken in by the cell by endocytosis �Recycling of

GOLGI APPARATUS www. scielo. cl/. . . /ijmorphol/v 23 n 4/img 07 -01. jpg

GOLGI APPARATUS Golgi vesicles take transformed materials from the exit face to their destination Golgi vesicles transport the materials from one cisterna to the next Cisternae are flattened sacs © 2016 Paul Billiet ODWS Transport vesicles bring material from the endoplasmic reticulum to the entry face

GOLGI APPARATUS Functions �Processing and packaging �Synthesising lysosomes to contain the potentially dangerous catabolic enzymes �Producing secretory vesicles e. g. mucus �Making more plasma membrane. © 2016 Paul Billiet ODWS

ENDOPLASMIC RETICULUM (ER) © 2016 Paul Billiet ODWS www. lifesci. sussex. ac. uk/. .

ENDOPLASMIC RETICULUM (ER) Rough ER Smooth ER Transport vesicles Membranes © 2016 Paul Billiet

ER Functions �Difficult to extract intact �ER starts the biosynthetic pathways that form many protein and lipid molecules in the cell �These continue in the Golgi apparatus �Rough ER has ribosomes attached to it as opposed to Smooth ER �The proteins made on rough ER will eventually be secreted outside the cell. © 2016 Paul Billiet ODWS

RIBOSOME www. palaeos. com/. . . /Images/Ribosome. jpg www. kcl. ac. uk/. . .

RIBOSOME �NOT membrane bound �Found both in prokaryotes and eukaryotes �The subunits are synthesised separately in the nucleolus of the nucleus of eukaryotes. © 2016 Paul Billiet ODWS Large ribosome subunit Small ribosome subunit

RIBOSOME Distribution in the cytoplasm • single free-floating • attached to rough ER • linked together as a POLYRIBOSOME or POLYSOME Function: Protein synthesis Chemical composition Protein + RNA = a nucleoprotein. © 2016 Paul Billiet ODWS