parts of eukaryotic cells + functions

nucleus

- controls cell activities such as cell growth and repair of worn-out parts

- essential for cell division = cells without a nucleus are unable to divide

- controls genetic info (DNA) = DNA molecules contains sequences of nucleotides called genes, which code for polypeptides

cell surface membrane

- since it is partially permeable, it allows some substances to pass through but not others

- compartmentalization to allow cells and organelles to have specialized functions

cytoplasm

- main site for metabolic activities

- many chemical reactions occur here (due to presence of water)

ribosomes

- sites for polypeptide/protein synthesis

- ribosomes translate (the gene carried by) the messanger RNA (mRNA) into a polypeptide

- the polypeptide then folds to form a protein with a specific 3D conformation

- free ribosomes suspended in the cytoplasm synthesise proteins that function within the cytoplasm

- ribosomes attatched to the RER synthesise proteins that are meant to be secreted out of the cell, packaged within lysosomes or to be embedded into the membranes

vesticles

- carry substances between membrane compartments

- exocrytosis describes the process of vesticles fusing with the plasma membrane and releasing their contents to the outside of the cell

- endocrytosis is the process of capturing a substance or particle from outside of the cell by engulfing it with the cell membrane and bring it into the cell

lysosomes

- digestion of food/foreign particles

rough endoplasmic reticulum

- folding of polypeptides into proteins

- ribosomes attatched to the RER are sites of protein synthesis

- transport of proteins for secretion

smooth endoplasmic reticulum

- synthesis of lipids - enzymes present in the SER synthesise lipids such as phospholipids and steroids

- detoxification - convert harmful substances into harmless ones to be excreted

golgi apparatus

- chemical modification - performs chemical modification of proteins and lipids transported from the RER and SER via transport vesticles

- sorting and packing - proteins and/or lipds that are secreted and sorted and packeged into secretory vesticles

- formation of lysosomes

mitochondrion

- site of respiration - mitochondrion performs (aerobic) respiration during which glucose is oxidised to release energy for cell activities

chloroplast

- Site of photosynthesis- light energy absorbed by chlorophyll is converted into chemical energy for glucose formation

vacuole

- helps develop turgidy of plant cell as water molecules enter the cell sap by osmosis when vacuole volume increases

- storage of starch converted from excess glucose

- storage of pigments which gives flowers or fruits its colour to attract insects and birds for pollination and seed dispersal

- storage of defensive compounds for protection by making plants deadly or unpalatable for hebivores to consume

- deposition site for metabolic waste materials

cellulose cell wall

- highly rigid to provide mechanical support for individual cells, lignin deposition further increases the strength in some of the xylem walls

- prevevents cell lysis when the cell is placed in a medium of less negative water potential

deleop a coat of waxy cuticle which reduces excessive water loss and reduces rate of infection by plant pathogens