1. click on the different organelles to find out about them
on every slide you can click on the animal or the plant icon to go to that cell type

2. the nucleus
the nucleus controls the cell’s activities and contains a cytoplasm like substance called nucleoplasm
DNA is bound to proteins and is called chromatin – this condenses to form the chromosomes during cell division
within the nucleus are 1 or 2 bodies – each called a nucleolus these make rRNA and assemble ribosomes `
the nuclear membrane is a double membrane structure containing pores that allow the transport of mRNA and nucleotides

3. mitochondria
mitochondria are formed from 2 membranes separated by a narrow inter-membrane space
the inner membrane is folded to increase its surface area into extensions called cristae
the biochemical reactions of aerobic respiration take place in the mitochondria and they release chemical energy in the form of ATP

4. golgi body
the golgi body (or apparatus) was named after its discoverer Camillo Golgi it is similar in structure to smooth ER but has a more compact form
it is a collection of flattened membrane sacs that are constantly forming on one side and budding off as vesicles on the other
its functions are:
to package proteins for secretion
to secrete carbohydrates
to produce glycoproteins
to transport and store lipids
to form lysosomes

5. lysosomes
lysosomes contain and isolate digestive enzymes – they are needed to prevent the rest of the cell being digested by these enzymes
several lysosomes may empty their contents into one membrane lined vacuole containing a worn out organelle

6. centrioles
centrioles arise from a region of the cytoplasm called the centrosome and consist of 2 hollow cylinders
at cell division they migrate to opposite poles of the cell and produce the microtubules of the spindles that pull chromosomes apart

7. endoplasmic reticulum
the endoplasmic reticulum (ER) is an elaborate system of membrane bound sacs (cisternae) – these are often continuous with the nuclear envelope and the golgi body
smooth endoplasmic reticulum (sER) lacks ribosomes – it is involved with the synthesis and transport of lipids
rough endoplasmic reticulum (rER) has ribosomes lining it and is involved with protein synthesis as a transport system

8. ribosomes
ribosomes are involved in protein synthesis – they move along molecules of mRNA and read the nucleotide code to produce proteins
mRNA
U U U C G A U G C A U C G C A A C U C G C
C G U
aa5
U G A
aa6
small sub-unit
large sub-unit
aa1
aa2
aa3
aa4
ribosomes are made of rRNA (produced by the nucleolus) and protein – they consist of one large and one small sub-unit

9. cytoplasm
the cytoplasm is the matrix that contains all of the different organelles
it is an aqueous mixture of chemicals either in solution or as colloids including:
simple ions such as sodium (Na+) and chloride (Cl-)
organic molecules such as amino-acids, ATP and sugars
storage materials such as fat droplets
it can be seen to be moving – this is called cytoplasmic streaming

10. cell membrane
the main function of a cell membrane is to function as a boundary between the cell and its environment – it controls entry and exit into and from the cell
a phospholipid bilayer forms the majority of the membrane
this “fluid-mosaic” model was proposed in 1972 by J Singer and G Nicholson
proteins also totally penetrate and appear on the inner and outer surfaces of the membrane

12. chloroplasts
found only in plant cells – chloroplasts are bounded by a double membrane known as the chloroplast envelope
inside is a colourless matrix – the stroma
floating in the stroma are thylakoids these stack together to form a granum
the grana can be interconnected by tubular extensions called intergranal lamellae
also present are starch grains which act as temporary stores for the carbohydrates formed during photosynthesis

13. vacuole
the vacuole is a large fluid filled sac
it is surrounded by a membrane called the tonoplast
it functions as a storage site and provides support for plant cells by creating a pressure potential through osmosis

14. cell wall
the cell wall is made of cellulose microfibrils contained in a polysaccharide matrix
the cell wall provides strength and support and provides a pathway for water to move through the plant – the apoplast pathway

15. plasmodesmata
there are gaps in the cell wall that allow neighbouring cells to link together
there is a continuation of cytoplasm from cell to cell and the endoplasmic reticulum can also be linked
cell 1
cell 2