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)


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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)


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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)


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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


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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)


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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)


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General Eukaryotic Cell


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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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