BY1.2 - Cell structure

WJEC BY1 - Organelles and diagrams

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  • Created by: Megan
  • Created on: 14-05-11 15:43

Nucleus

  • Prominent feature in cell (http://acseenotes.files.wordpress.com/2011/03/nucleus_1.gif)
  • Nucleus is bound by double membrane (nuclear membrane)
  • Nuclear membrane has pores in it
  • The cytoplasm-like material is called nucleoplasm
  • Nucleoplasm contains chromatin
  • Small spherical body called nucleolus within nucleus
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Nucleus functions

  • Control cell's activity
  • retain chromosomes
  • Pores allow transportation of mRNA and nucleotides
  • Nucleoplasm contains chromatin (chromatin is made up of DNA coils bound to proteins).
  • Nucleolus makes RNA (RNA is needed to make ribosomes)
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Mitochondria

  • Double membrane seperated by narrow fluid-filled inter-membrane space(http://t2.gstatic.com/images?q=tbn:ANd9GcQjCgZUOGEkgJyPECZUQ8zvWdIJql9rUzMyfk_34CJLiLb_umwRzw)
  • Inner membrane is folded inwards to from extensions called cristae
  • Interior contains organic matrix (containing chemical compounds)
  • Reactions take place in matrix or on the inner membrane
  • Muscles contain large numbers of mitochondria because of high metabolic activity.

 

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Mitochondria functions

  • Site of anaerobic respiration in the cell
  • Cristae increases the surface area on which respirtory processes takes place
  • Produce energy as ATP
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Endoplasmic reticulum (ER)

  • (http://micro.magnet.fsu.edu/cells/endoplasmicreticulum/images/endoplasmicreticulumfigure1.jpg)
  • Elaborate system of membranes forming flattened sacs
  • Fluid filled spaces between membranes are called cisternae
  • The ER is connected with the nucleur membrane and may link to the golgi body
  • Cavities are interconnected
  • Rough endoplasmic reticulum (RER) - Ribosomes on outer surface
  • Smooth endoplasmic reticulum (SER) - membranes which lack ribosomes.
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Endoplasmic reticulum functions

  • Transport of materials throughout the cell
  • RER - transports proteins made by the ribosomes (present in large amounts in cells that make enzymes that may be secreted out of the cell
  • SER - synthesis and transport of lipids
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Ribosomes

  • Made of one large and one small sub-unit
  • Manafactured in nucleolus from rRNA and protein

    (http://t0.gstatic.com/images?q=tbn:ANd9GcTO5PUQAQWJniDjUcB0VWLQttcW6k325dVTRddW9cCi_k7unokPiQ)

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Ribosome functions

  • Important in protein synthesis
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Golgi body Functions

(http://t1.gstatic.com/images?q=tbn:ANd9GcRBMtG88aUdOTspgeVgjHnXkorlJlrgPskkR40s39eH5pLU0kQ57A)

  • Produce secretory enzymes
  • Secretes carbohydrates (example - formation of plant cell walls)
  • Producing glycoprotein
  • Transporting and storing lipids
  • Forming lysosomes
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Golgi body forming

1) Formed by RER being pinched off and forming small vesicles

2) A number of vesicles join up and fuse together forming golgi body

3) Proteins are transported in vesicles and are modified and packaged in golgi body

4) E.g. proteins combined to make glycoproteins

5) Vesicles pinch off other end and the products are secreted by exocytosis when vesicle fuses with cell membrane

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Lysosomes

(http://t2.gstatic.com/images?q=tbn:ANd9GcQgE3vqhC9-B9vbY94QTBo2XbuFVN3BQgb9dSq2zfELSXIa388m3g)

  • Small vacuoles formed when portions of the golgi body are pinched off
  • Contains isolated digestive enzymes from remainder of the cell
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Lysosome functions

  • Release enzymes and destroy worn out organelles in cell
  • Some lysosomes discharge contents during digestion carried out in membrane-lined vacuole
  • Digest material that has been taken into cell, e.g.white blood cells engulf bacteria by phagocytosis and lysosomes discharge contents into the vesicle and digest the bacterium.
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Centrioles

(http://t2.gstatic.com/images?q=tbn:ANd9GcRNJNOcxwLkAGt6eUk8Frn8Fwnr-Lh9ciOnmMWA-QUe8kytgNYP)

  • Found in animal cells and most protoctists but not higher plants cells
  • Located outside nucleus in centrosome
  • Two hollow cylinders positioned at right angles to one another.
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Centriole function

Cell division - centrioles divide and move to opposite poles and synthesise the microtubules of the spindle

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Chloroplast

ONLY IN PLANT CELL

(http://t3.gstatic.com/images?q=tbn:ANd9GcTay9tNSVyx7UpVbNSBA5g0qfYNwlNNN3ykoZLkD_t59oERO6FT)

  • Found in photosynthesising tissue
  • Double membrane, inside fluid stroma - containing ribosomes, lipid, circular DNA (maybe starch)
  • Thylakoids (flattened sacs), A stack is called a granum (with 2-100 of closed parallel sacs)
  • Thylakoid contains photosynthetic pigments such as clorophyll
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Chloroplast function

  • Has a large surface area for trapping light energy.
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Comments

Sam Tobin

Mitochondria is aerobic respiration, not anaerobic respiration.

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