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Biology: lecture 5 cellular life two (The endoplasmic reticulum (Membrane…
Biology: lecture 5 cellular life two
Cytoplasm
area defined by nuclear membrane and plasma membrane
consists of cytosol and membrane bound organelles
intracellular fluid, mainly water and ions, biomolecules/metabolites and proteins
concentration gradients of biomolecules- metabolism
protein complexes(Inflammasomes, apoptosomes, centromeres)
cytoskeleton proteins
shape, structure motility
Where do proteins go?
Cytoskeleton
Actin Filaments
Microfilaments, Actin polymers, cellular growth as actin filaments polymerizes & depolymerizes at opposite ends, binds and moves along
Intermediate filaments
larger filament structures, various proteins, cell type specific, Eg keratin in epithelia, anchor organelles and organize 3D shape
Microtubules
Hollow cylindrical structures, tublin polymers involved in cellular organization and centrosome
The endoplasmic reticulum
Membrane network from nucleus into cell
consists of folds(cisternae)
rough ER -studded with ribosomes sites of protein synthesis
Smooth ER- no ribosomes, important in lipid synthesis & detoxification
It doesn't reach the plasma membrane directly
Vesicles bud off(membrane bound) & transport contents around and out of cell
Intracellular Transport
Golgi apparatus
directs/ sorts traffic inside cell
Smooth ER- traffics lipid to Golgi
Rough ER vesicles- delivers protein cargo to golgi
new membrane bound organelles bud off golgi go to LYSOSOME- for recycling PLASMA MEMBRANE- for transport functions or SECREATORY VESICLES- for secreation/export (eg exosomes)
membrane network within cytoplasm, generally 4-8 folds
Endocytosis
lysosome: contains digestive enzymes that break down cell parts or substances entering by vesicles
Transport vesicles: transports lipids to golgi apparatus
smooth endoplasmic reticulum and synthesizes lipids and has other functions
Rough ER synthesizes proteins and packages them in vesicles
golgi apparatus modifies lipids and proteins from the ER sorts and packages them in vesicles
The lysosome
membrane bound compartment within the cell
highly acidic
contains degradation enzymes (work at acidic pH)
integrates vesicles/transport network from ER/golgi & Endosomes(incoming cargo from external environment)
important in response to pathogens (Phagocytosis)
Important for recycling old organelles (autophagy)
form membranes form around damaged organelle or cargo DOUBLE MEMBRANE AUTOPHAGOSOME Matures and fuses with lysosome for degradation
Phospholipid bilayer
Hydrophilic head
Polar, water soluable
hydrophobic tails
2 fatty acids non polar
Micelle Circular arrangement of phospholipids
Transport across the phospho lipid bi layer
water (polar) passes through osmosis (passive transport) (osmotic pressure), Polar molecules(ions/simple nutrients) can diffuse through easily (active transport) because of the hydrophobic centre, Hydrophobic non polar molecules pass through easily (diffusion)
Gram Negativity/Gram positivty
Gram negative
contain outer membrane with lots of lipids/ lipoproteins & transport proteins thin wall of peptidoglycan stain negative contains periplasmic space
Gram Positive
No outer membrane, major peptidoglycan (carbohydrate polymer) cell wall (stain positive- retain counterstain)
smaller periplasmic space
Plant cell wall
each has 3 layer structure
Plasma membrane
Primary wall
middle lamella