Cell structure - Organelles Flashcards
describe the structure of the nucleus
nucleoplasm contains chromatin (DNA + protein)
nuclear envelope
nuclear pores
nucleolus
outer membrane is continuous with rough ER
describe the function of the nucleoplasm
contains DNA that codes for proteins
during cell division chromatin condenses into chromosomes
describe the function of the nuclear envelope
double membrane that encloses DNA and keeps it separate from reactions in the cytoplasm
describe the function of the nuclear pores
allow entry of molecules for DNA replication
exit of mRNA for protein synthesis
describe the function of the nucleolus
manufactures ribosomes
why is the outer membrane being continuous with the rough ER useful
allows easy transport of substances
describe the structure of the endoplasmic reticulum
cisternae: membrane bound sacs
rough ER: covered with ribosomes
smooth ER: lacks ribosomes
describe the function of the cisternae in ER
allow transport within the cell
describe the function of the rough ER
synthesise and transport proteins
describe the function of the smooth ER
synthesis and transport lipids and steroids
describe the structure of the ribosomes
2 subunits made of rRNA and protein
where are ribosomes synthesised and how do they leave
synthesised in nucleolus and then pass through the nuclear pores to the cytoplasm or rough ER
what are the two types of ribosomes
22nm/80S(eukaryotic cells)
18nm/70S (prokaryotic cells, chloroplasts, mitochondria)
describe the function of ribosomes
protein synthesis
binds to and moves along the mRNA and translates it
describe the structure of the Golgi apparatus
a stack of flattened membrane bound cavities called cisternae
secretory vesicles
describe the function of cisternae in Golgi apparatus
modifies proteins (e.g adds carbohydrates)
packages proteins into secretory vesicles or lysosomes
describe the function of the secretory vesicles
produced by Golgi apparatus, will fuse with the cell surface membrane to release hormones or enzymes from the cell (exocytosis)
describe the structure of the lysosomes
vesicles which contain hydrolytic enzymes
describe the function of the lysosomes
isolate potentially harmful enzymes from the cell
break down material ingested by phagocytes
break down old organelles
break down cells when they die
describe the structure of the mitochondria
double membrane
inner membrane folded to form cristae
matrix contains: small ribosomes (18nm/70S), circular DNA, enzymes
where are large numbers of mitochondria found
cells requiring lots of energy e.g muscle and liver