Structure of the cell Flashcards
what is a eukaryote cell
cell that contains membrane bound organelles
- organelles are suspended in cytosol
what is evidence of cellular arrangement
light microscope x1500 allows cells to be seen clearly
- electron microscope x50000 can see the ultrastructure of cells - confirms proposed arrangement
What is the function of the cell membrane
- separates the cytoplasm from the outside environment
structure of cell membrane
fluid mosaic model
- phosphate head attached to a fatty acid chain
- bilayer - tails point inwards
- cholesterol molecules
- lots of integral & peripheral proteins
what is the function of cholesterol in the CSM
- help regulate fluidity and stiffens it
- prevents small water soluble molecules from passing through
- provides a suitable molecular environment for some transmembrane proteins
what is the function of integral & peripheral proteins in the CSM
integral-allow different substances in and out of cells
peripheral- can act as receptors
what is the structure of the nucleus
large double membrane-bound organelles that contains chromatin and the nucleolus
- nuclear envelope has pores and is selectively permeable between the nucleus and the cytoplasm
what does the nucleolus contain
DNA, RNA and proteins which regulate the cell cycle
- site for rRNA synthesis
what is the function of mitochondria?
generate chemical energy (ATP) necessary for biochemical reactions with aerobic stages respiration
what do number of mitochondria indicate?
level of metabolism
which cells have many mitochondria and why?
hepatocytes - active role in digestion
sperm cell - need ATP for motility
slow twitch skeletal muscle- high aerobic activity
structure of endoplasmic reticulum
3D network of cavities, some sac like and some tubular, bounded by membranes
- two types RER AND SER
structure and function of RER
- surface studded by ribosomes which are essential for protein synthesis
- packages and folds primary and secondary proteins into tertiary ones and transports in vesicles to golgi
which cells contain lots of RER
pancreatic epithelial - synthesis proteins to release into the lumen
plasma cells - to produce antibodies
nerve cell bodies - to produce proteins that are used internally and transported along the axon along microtubules
structure and function of SER
no ribosome on the surface
single tubular sacs
involved in lipid, glycogen and steroid synthesis and the detoxification of noxious substances
where is lots of SER found?
liver cells - lipid synth and detoxification of drugs by xenobiotic degradation
structure of Golgi apparatus
- stacks of parallel flattened membrane pockets (cisternae)
function of golgi
modifies tertiary into quaternary or lipo/glycoproteins
- dehydrates enzyme secretions
- produce lysosomes
lysosomes structure and functions
membrane bound organelles that contain hydrolytic enzymes
- decompose substances taken into the cell and destroy worn out organelles and foreign proteins
what is glycogen
polymer of alpha glucose that is highly branched and absorbed from the digestive system and circulates in the blood
- can be made by most cells to allow ATP synth to take place
why are lipid droplets found in some cells
store for triglycerides in the cytoplasm
what is the structure of fat cells and why
nucleus pushed to the side
lack of organelles
capillaries in connective tissue between the cells
- this is because it is specialised for triglyceride storage
what stain turns lipids black in an electron micrograph?
osmium
what is the cytoskeleton
dynamic, 3D web like structure filling the cytoplasm that acts a framework to maintain the shape and polarity of the cell
what are the components of the cytoskeleton
microfilaments
intermediate filaments
microtubules
what are microfilaments
-strands of actin (contractile) so provide a dynamic framework
where are microfilaments important
microvilli - act as a core through the projection to increases SA, allow motility and anchor is to the actin cortex of the cell
what are intermediate filaments for?
purely structural and form assemblies inside the cell
there are 5 classes (e.g. neurofilaments)
what are microtubules
largest component of cytoskeleton and made of subunits that can assemble/disassemble to provide for changes in cell shape and position of organelles
what is the structure of centrioles
come in pairs
bundle of 9 tubules in star formation - one is vertical and one is flat
what is the function of centrioles
maintaining cell shape in non dividing cells and tracts for transporting vesicle and organelles to move from place to place
- responsible for polymerising microtubules
- in a dividing cell centrioles replicate, separate and move to opposite sides of the cell to pull out the mitotic spindle and cause separation of the cell
erythrocytes shape and reasoning
disc shaped cells
lack nucleus and organelles
can deform when passing through narrow channels and shape allows a lot of Hb
nerve cell structure and reasoning
long axon as there is need to communicate to the periphery
epithelial cell structure and reasoning
columnar cells and crushed together with high cell to cell contact - act as a barrier
skeletal muscle cell structure and reasoning
long and thin
multinucleated
allow contraction to take place with sliding filament theory
