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RELEVANT LEARNING OUTCOME:
(b) Interpret and recognise drawings, photomicrographs and electron micrographs of the cytoplasm (cytosol) and cellulose cell wall, and the following membrane systems and organelles: rough and smooth endoplasmic reticulum, Golgi body, mitochondria, ribosomes, lysosomes, chloroplasts, cell surface membrane, nuclear envelope, centrioles, nucleus and nucleolus. [H2 only: for practical assessment, candidates may be required to operate a light microscope, mount slides and use an eyepiece graticule and a stage micrometer]
(c) Outline the functions of the membrane systems and organelles.
Organelles are structures found within the cytoplasm that have distinct structures, macromolecular compositions and functions. There are two types:
(i) Membranous: membrane-bound compartments
(ii) Non-membranous: not enclosed in a membrane but freely floating in the cytosol
Click on any of the organelles in the table below to find out more about structures and functions of each one.
👁️🗨️View the video below for an overview of the common structures in a cell, as well as some uncommon ones in specialised cells.
💡The Endosymbiotic Theory
💡The Endosymbiotic Theory
This theory proposes that eukaryotic cells developed from the symbiosis (i.e., the close, long-term interaction between two species) of prokaryotic cells. It was first based on observations that the mitochondrion and the chloroplast share some similarities with bacteria!
👁️🗨️Watch this video that explains how the theory came about (and how endosymbiosis still exists today!).
This webpage also provides you with information about the founder of this theory, Lynn Margulis, and more evidence supporting this theory.
🖊️Check Your Understanding: Lecture Notes Checkpoint
🖊️Check Your Understanding: Lecture Notes Checkpoint
(attempt these questions after you have familiarised yourself with the list of organelles above)
1) What are the membrane bound organelles？What are the non-membrane bound ones？
1) Membrane-bound: nucleus, mitochondrion, chloroplast, rough ER, smooth ER, Golgi apparatus, lysosome.
Non-membrane bound: ribosome, centriole
2) Which organelles are enclosed by a double membrane？
2) Nucleus, mitochondrion, chloroplast
3) Which one of the following statements is true? Support your answer.
a) The nucleolus is a membrane-bound region containing DNA that codes for rRNA.
b) Plant cells contain chloroplasts but not mitochondria.
c) The Golgi apparatus receives biomolecules from both the RER and the SER for further chemical modification.
3) Statement (c) is true. The GA will complete the processing of these molecules and package them for delivery.
Statement (a) is false because the nucleolus is a dense region within the nucleus that is NOT membrane-bound.
Statement (b) is false because plant cells also need to carry out respiration for energy production, and hence need mitochondria as well.
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