Cells – Prokaryotes and Eukaryotes

Prokaryotes and Eukaryotes

Prokaryote

Eukaryote

Etymology:
Eukaryote = “good carrier bag” i.e. has a nucleus
Prokaryote = “before carrier bag” i.e. no nucleus

Differences

Prokaryotes

Eukaryotes

Bacteria, archaebacteria Protists (amoeba), plants, animals, fungi
Smaller (< 5μm) Larger ( > 10μm)
Always unicellular Often multicellular, can be unicellular
No nucleus and membrane-bound organelles*HAS organelles –> ribosomes and nucleoid Always has a nucleus and membrane-bound organelles
DNA is circular, without proteins DNA is linear, associated with proteins
Small ribosomes (70S) Large ribosomes (80S)
No cytoskeleton Always has a cytoskeleton
Reproduction by binary fission or budding (asexual) Reproduction by mitosis (sexual) or meiosis (asexual)
In general:Smaller and simpler In general:More advanced and complex

————————————————–

Plant and Animal cells

Similarities:

Both are present:

  •  Nucleus
  •  Cell membrane
  •  Cytoplasm
  •  Endoplasmic Reticulum (Both smooth and rough)
  •  Ribosomes
  •  Mitochondria
  •  Golgi Apparatus
  •  Microfilaments
  •  Flagella –> may be found in some cells

(those in bold are not found in the picture)

Differences:

Feature

Animal Cell

Plant Cell

Shape Irregular (round, elliptical) Fixed (rectangular)
Vacuole One or more small vacuoles (much smaller than plant cells) One large, central vacuole taking up 90% of cell volume
Function of vacuole Store water, ions and waste Store water and maintain turgidity of cell
Plasma membrane Cell membrane only Cell membrane and cell wall
Cell wall
Chloroplast
Plastids
Lysosomes Not confirmed (controversial)
Cilia ✖ (Rare)
Centrioles ✖ (only present in some lower plant forms – ferns, mosses)

—————————————————

Organelles and their functions

Organelle

Function

Nucleus Controls all activities of the cellProtects DNA from interference by separating it from cytoplasm’s activity
Nuclear membrane Allows transfer of material out of the nucleus to the cytoplasm
Chromatin(The contents of the nucleus, made up of DNA and proteins) Strengthen DNA to prevent damage during reproductionControl DNA replication
Cytoplasm A jelly-like substance where most cellular activities occur.Supports and protects organelles.
Cell membrane Separates and protects the interior of cell from the outside environmentSemi-permeable membrane that regulates the movement of substances in and out of cell
Vacuole(works with lysosomes) Stores nutrientsIsolates and exports harmful/unwanted materials in the cell

Plant cells -> contains cell sap

Regulates turgor pressure (i.e. plant’s rigidity) by regulating the amount of water in it

Animal cells

As animal cells are already in an aqueous environment, their vacuoles are not needed to store water and are small

Mitochondria Uses glucose and oxygen to produce energySite of aerobic cellular respiration
Endoplasmic Reticulum (ER) (Works with Golgi apparatus) Transports substances between and within cells.

(a layman’s definition and analogy: http://goo.gl/oS4Ds)

Smooth ER

Removes toxins from the cells

Rough ER

Supports the cell’s shape

Packs synthesized proteins from ribosomes and fats into vesicles and sends them to Golgi apparatus

Ribosomes Site of protein synthesis
Golgi apparatus(Works with ER) Packages proteins and other macromolecules for transport to other parts of the cell or for storage within the cell.
Lysosomes(Works with vacuole) Fuses with vacuole to digest the harmful/unwanted materials insideTransports undigested material to cell membrane for release
Choloroplast Contains chlorophyll for photosynthesis in plants
Cell wall Protects the cell and maintains its shapePrevents over-expansion due to turgor pressure when water enters the cell

References

Pictures:

http://yunzhenandbio.blogspot.sg/2010/02/cells.html
http://imcurious.wikispaces.com/Period+1+Midterm+Review+2009
http://evolution.berkeley.edu/evosite/lines/IIDmolecular.shtml

Information:
Difference between eukaryotes and prokaryotes – pdf file
Difference between eukaryotes and prokaryotes
Difference between eukaryotes and prokaryotes – Yahoo answers
What is Turgidity?
Functions of nuclear membrane
Function of vacuole in an animal cell
Function of endoplasmic reticulum

Interactive Websites about organelles:

http://www.cellsalive.com/cells/cell_model.htm

http://learn.genetics.utah.edu/content/begin/cells/insideacell/

http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.htm

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One thought on “Cells – Prokaryotes and Eukaryotes

  1. Christa says:

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