Cell as basic unit of life: Lesson 5 Flashcards
what are some non membranous cell organelles ?
ribosomes and centrosomes
what are ribosomes?
granular , nonmembranous particles in many parts of the cell. cytoplasm , mitochondria , plasmid , rough ER and nuclear membrane
what is the weight of ribosomes in prokaryotic cytoplasm and what is their weight in eukaryotic cytoplasm
70s (50s=30s)
80s(60s+40s)
what is svedberg unit?
unit of sedimentation rate of cells after centrifugation
what are centrosomes?
they play an important part in cell division by forming asters and organizing spindle fibers during cell division .
they are also involved in formation of cilia , flagella , and axial filament in sperm.
it is present near the nucleus
what kind of cells are centrosomes present in?
only present in animal cells
what structures are centrosomes formed of?
2 cylindrical structures at a right angle to each other called centrioles . these centrioles are connected by proteinaceous strands
describe the structure of centrioles
they are made of a circle of 9 triplets of microtubules
what are flagella and cilia made of ? describe it the structure of the unit .
contractile protein tubulin in the form of microtubules .
arrangement of microtubules is 9+2.meaning they have 9 pairs in a circle and then 1 pair in the middle
where can cilia and flagella be seen . give an example of a multicellular organism and a unicellular organism .
some unicellular organisms swim in water with the help of cilia and flagella
some multi cellular organisms have cilia that beat and create a current in fluid in order to move it in a specific direction (trachea )
how is the structure of microtubule different from flagella and cilia ?
centrosomes have 9 triplets of microtubules while flagella and cilia have a 9+2 structure of microtubules . meaning they have 9 pairs in a circle and then 1 pair in the middle
where do flagella and cilia arise from ?
basal bodies , which arise from 9 triplets of centrosomes . meaning they are essentially extensions of centrosomes
what is the cytoskeletons function?
structure that helps cells maintain their shape and their internal organization. it also provides mechanical support .
what are the 3 types of cytoskeleton ?
microfilament (smallest 5-7nm). they are made up of actin and present in muscles .
microtubules (largest 25nm). composed of tubulin
intermediate filament(middle 10nm): constructed of a group of different subunit proteins
