cell structure

• Nucleus – a large spherical organelle surrounded by the nuclear envelope (double membrane with pores which are responsible for regulating the movement of substances between the cytoplasm and the nucleus). Has small structures within it (chromatin) made from DNA and protein and can be found in the nucleolus. It is responsible for controlling the cell by regulating transcription which takes place in protein synthesis and makes ribosomes.
• Cell wall – a structure found on the outside of prokaryotes and plant cells. Can be rigid or flexible. Mainly made from the carbohydrate cellulose. Offers structure and support.
• Plasma membrane – encloses the cell. Found on surface of animal cells and inside of cell wall for prokaryotes and plant cells. Made of lipids and proteins. Regulates movement of substances inside and outside the cell. Has receptors on the surface which respond to chemicals like hormones. 
• Lysosomes – round organelles which have no clear internal structure. Surrounded by plasma membrane and contain digestive enzymes which are separated from the cytoplasm by the plasma membrane. Responsible for breaking down worn down components of the cell and digesting invading cells (phagocytosis).  
• Ribosomes – not surrounded by plasma membrane. Small organelle made form RNA and protein. Found floating in the cytoplasm or attached to the rough endoplasmic reticulum. Site for protein synthesis. 
• Rough endoplasmic reticulum – series of membranes enclosing a fluid filled space/membranes. Whole surface is covered in ribosomes. Fold and process proteins made by ribosomes.  
• Smooth endoplasmic reticulum – series of fluid filled membranes. Synthesise and process lipids. 
• Vesicles – small, flattened sacs in cytoplasm surrounded by a plasma membrane. Transport substances between cell organelles and sends things outside of the cell via the plasma membrane. Different types of vesicles. Made in Golgi apparatus on cell surface or by rough/smooth ER. 
• Golgi apparatus – series of membrane bound, fluid filled, flattened sacs. Have many vesicles surrounding them. Responsible for processing and packaging proteins and lipids. Makes lysosomes. 
• Golgi centrioles – hollow cylinders made from microtubules. Used to pull apart chromosomes during cell division. Present in all animal cells but only some plant cells. 
• Cilia – found on cell surface of some animal cells. Small hairlike structures. In cross section there are nine pairs of microtubules around the edge with and individual pair in the middle. These microtubules allow the cilia to move so they can move substances across the cell surface. 
• Flagella – long cilia in eukaryotes. Stick out of cell surface and is surrounded by a plasma membrane. Inside they have nine pairs of microtubules around the edge and a pair in the middle. Tubules contract allowing the flagella to move like outboard motors to propel the cell forward. 
• Mitochondria – oval shaped organelle with a double membrane. Used to make structures known as cristae. Matrix inside contains enzymes that help with respiration. Main site of aerobic respiration which releases ATP. More mitochondria found in cells which require more energy. 
• Chloroplasts – small, flattened organelles with a double membrane. Thylakoid membranes are stacked in some parts of the chloroplasts called granum. Grana are held together by lamella (pieces of thylakoid membrane).  Site of photosynthesis takes place in grana or stroma (thick fluid). 
• Transport vesicles - move molecules between locations in the cell
• Secretory vesicles - contains substances to be moved to the plasma membrane to be excreted from cells
• vacuole - contains mostly water to control the correct water potential (concentration) in cells
• Cytoskeleton – made up of microtubules, actin filaments, and intermediate filaments. Gives cells its shape and helps to organise the cell’s parts. Basis for movement and cell division.