Cell Structure and Cell Membrane

Structure

• Surrounded by a nuclear envelope, made of two membraneswith fluid between them. Nuclear pores go right through the envelope
• Nuclear pores - large enough for relatively large molecules to pass through
• Dense spherical structure called neucleolus inside the nucleus 

Function

• Nucleus houses nearly all genetic material
• Chromatins consists of DNA  and proteins - when cells divide chromatin condenses into visible chromosomes
• Nucleolus makes RNA and ribosomes - these pass into cytoplasm and proteins are assembled at them

Structure

• Consists of series of  flattened membrane sacs called cisternae - continuous with outer nuclear membrane
• Rough ER (RER) studded with ribosomes
• Smooth ER (SER) does not have ribosomes

Function

•  RER transports proteins that are made on the attaches ribosomes - some of proteins secreted from cell, some replaced on cell surface membrane
• SER makes lipids that cell needs

Structure

• Stack of membrane-bound, flattened sacs

Function

• Receives proteins from ER and modifies them - may add carbohydrate chains
• Packages modified proteins into vesicles that can be transported
• Some modified proteins may go to surface of cell so that it may be secreted

Structure

• May be spherical or sausage-shaped
• Have two membranes seperated by fluid filled space
• Inner membrane highly folded to form cristae
• Central part of mitochondria called matrix

Function

• Site where ATP produced during anerobic respiration
• ATP sometimes called universal energy carrier - almost all activities that need energy in cell driven by energy released by ATP

Structure

• Found only in plants and some protoctists.
• Have two membranes separated by fluid-filled space
• Inner membrane continuous with an elaborate network of flattened membrane sacs called thylakoids (stack of thylakoids called granum or grana (plural))
• Chlorophyll molecules on thylakoid membranes and in internal membranes

Function

• Site of photosynthesis in plant cells
• Light energy used to drive reactions in photosynthesis in which carbohydrate molecules are made from carbon dioxide and water

Structure

• Spherical sacs surrounded by single membrane

Function

• Contain digestive enzymes
• Break down materials e.g. Neutrophils' lysosomes break down invading microorganisims;specialised lysosomes (acrosome) in the head of sperm penetrate egg by breaking down material surrounding egg

Structure

• Tiny organelles
• Some in cytoplasm and some bound to ER
• Each ribosome consists o two subunits

Function

• Site of protein synthesis in the cell (where proteins are made)
• Act as assembly line where mRNA from nucleus is used to assemble proteins from anmio acids

Structure

• Small tubes of protein fibres (microtubules)
• There is a pair of them next to nucleus in animal cells and in cells of some protocists

Function

• Take part in cell division
• Form spindle fibres, which move chromosomes during nuclear division