Cells and Organelles

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Prokaryotic and Eukaryotic Cells- General

  • Prokaryotic cells = simple cells which have no nucleus (namely bacteria).
  • Eukaryotic cells= complex cells which have a nucleus.
  • Prokaryotic cells ALWAYS have: cell wall, cell surface membrane, cytoplasm, ribosomes, food reserve, DNA circular molecule (nucleoid). 
  • Prokaryotic cells SOMETIMES have: Flagellum, slime capsule, plasmids (contain extra DNA)
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Eukaryotic Organelles- Nucleus

  • The nucleus is the largest organelle of a cell.
  • It has an inner and an outer membrane (envelope).
  • Dark central area is nucleolus, which manufactures ribosomes.
  • Surrounding nucleolus is nucleoplasm, which is perforated by nuclear pores. Nuclear pores allow the exchange of substances between nucleus and cytoplasm. 
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Eukaryotic Organelles- Nucleus (cont)

(http://www.emc.maricopa.edu/faculty/farabee/biobk/nucleus_1.gif)

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Eukaryotic Organelles- Mitochondria

  • Mitochondria are tiny rod-like structures in the cytoplasm.
  • Have an envelope.
  • Inner membrane has folds called cristae for increased surface area for respiration.
  • Space inside mitochondria is called matrix. Matrix contains DNA, ribosomes and enzymes for respiration.
  • Mitochondria are main sites for aerobic respiration.
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Eukaryotic Organelles- Mitochondria (cont)

                           (http://www.cartage.org.lb/en/themes/sciences/zoology/animalphysiology/anatomy/animalcellstructure/mitochondria/mitochondria.jpg)

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Eukaryotic Organelles- Chloroplasts

  • Chloroplasts are sites where photosynthesis occurs.
  • They consist of they thylakoids, which are membranes containing chlorophyl. 
  • Chlorophyl is pigment which traps light energy and converts it to chemical energy. 
  • A stack of thylakoids is called a granum.
  • Space in between granum is called stroma.
  • Has an envolope. 
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Eukaryotic Organelles- Chloroplasts (cont)

                 (http://carolguze.com/images/cellorganelles/chloroplast2.jpg)

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Eukaryotic Organelles- Rough Endoplasmic Reticulum

  • Rough E.R is a system of flattened, membrane-bound sacs  called cisternae. The membrane continues on from the outer membrane of the nucleus. 
  • Cisternae give R.E.R a large surface area.
  • Ribosomes are found on these cisternae. After a polypeptide is synthesised on a ribosome, it moves into the R.E.R, where is is modified and matured. Becomes a secondary/tertiary structure, or more chemical groups are added. 
  • Protein transported via vesicles to golgi body.
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Eukaryotic Organelles- Rough Endoplasmic Reticulum

             (http://img.sparknotes.com/figures/D/d479f5da672c08a54f986ae699069d7a/endoplasmic.gif)

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Eukaryotic Organelles- Golgi Body

  • The golgi body is a stack of flattened membrane bound sacs called cisternae.
  • They are continuously being formed at one end and budded of into vesicles at the other. 
  • Golgi body absorbs vesicles containing proteins. Protein is then passed through golgi body, undergoing structural maturity during movement. E.g the addition of a carbohydrate group to form a glycoprotien. 
  • When maturity is finished, protiens are budded of into vesicles and transported to the right destination.
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Eukaryotic Organelles- Golgi Body (cont)

(http://intranet.tdmu.edu.ua/data/kafedra/internal/med_biologia/classes_stud/%D0%9C%D0%B5%D0%B4%D0%B8%D1%87%D0%BD%D0%B0%20%D0%B1%D1%96%D0%BE%D0%BB%D0%BE%D0%B3%D1%96%D1%8F/Me%D0%B4%D0%B8%D1%87%D0%BD%D0%B8%D0%B9/English/1_levels%20of%20organization%20of%20living%20substance.files/image011.gif)

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Eukaryotic Organelles- Cytoskeleton

  • Cytoskeleton consists of proteins that give cell its rigid shape. The proteins form microtubules, microfilaments and intermediate filaments.
  • Microtubules are helically structured and made up of tubulin (protein). 
  • Centrioles are bundles of 9 microtubules, that pull apart to form a spindle of microtubules during mitosis.
  • Cytoskeleton controls movement of cell and transport of substances within cell.
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Eukaryotic Organelles- Ribosomes

  • Ribosomes are very smalll organelles, consisting of a large (60S) and a small (40S) sub-unit.
  • Made up of ribosomal RNA and protein.
  • Slightly smaller ribosomes found in chloroplasts and mitochondria. 
  • They are sites of protein synthesis, holding in place tRNA, mRNA and polypeptide chain.
  • They may form polysomes (collections of ribosomes).
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Eukaryotic Organelles- Ribosomes (cont)

(http://sgugenetics.pbworks.com/f/1269663451/1269891067/ribosome.jpg)

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General Eukaryotic Cell

(http://www.ebi.ac.uk/microarray/biology_intro_files/cell.jpe)

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General Microscopy

  • Resolution= The degree to which it is possible to distinguish between two objects.
  • Magnification= The degree to which the size of an image is larger than the object itself (no units).
  • Actual size = image size/magnification
  • Ensure correct units by making sure magnification has no units. 
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Organisation of Cells

  • Organelle- A specialised sub unit within a cell that has a specific function, and is usually enclosed within its own lipid membrane.
  • Cell- The cell is the functional basic unit of life. It can be specialised to preform many different tasks.
  • Tissue- A group of cells with a similar function.
  • Organ- A group of different tissues working together for a common purpose.
  • Organ system- Group of different organs working together to sustain life. 
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