Cell structure

Cell Structure

Membrane systems and organelles

Plasma Membrane 

• Controls what enters/leaves the cell (nuclear pores)

Nucleus 

• Surrounded by Nuclear envelope, 
• Contains Chromosomes – Long strand of DNA, 
• Nucleolus (Site of ribosome production, Code on Part of the DNA)

Ribosome 

• RNA+Protien, 
• Free in cytoplasm/attached to RER

RER 

• Enclose small spaces “cristernea”, 
• Ribosomes attached which synthesise polypeptides by condensation (which later enter the cristernae, membrane bound vesicles break off and go to golgi

Golgi apparatus 

• Modifies protein molecules (add carbohydrate groups),
• Vesicles break away from the surface and merge with cell membrane for exocytosis

Smooth endoplasmic reticulum 

• More flattened cristernae, 
• Involved in synthesis/transport of steroids/lipids. 
• Break down toxins.

Mitochondria 

• Site of respiration, 
• ATP produced by electolyltic chain reaction (Kreb’s cycle), 
• 2 membranes (inner is folded, cristernae)

Lysosomes 

• Little packages of hydrolytic/digestive enzymes, broken off from golgi apparatus, 
• Digest (Phagocytosis, bacteria/unwanted substances/damaged organelles, Acrosome in sperm head)

Centrioles 

• (animal cells only) at right angles, 
• Made of microtubules, in a circular pattern 
• Microtubules form spindle fibres during animal cell division