1. 8-10 Flashcards
The cell, 2 compartments:
cytoplasm + nucleus
Plasma membrane (PM), composed of:
phospholipids, proteins, cholesterol, oligosaccharides
PM, functions:
recognition & regulation; a selective barrier that maintains the intracellular env distinct from the extracellular env
PM, properties:
Thickness 7.5-10nm; composed of 45% lipid, 50% protein, 5% carb
PM, activities:
endocytosis, exocytosis, pinocytosis (invaginations of PM pinch off as vesicles, eventually fuse w lysosomes), phagocytosis (“cell eating”)
Mitochondria
Matrix is protein rich and contains DNA, tRNA, rRNA, mRNA.
Cristae - folds of mito membrane that increase SA
Endoplasmic Reticulum (ER)
Intercommunicating channels that form a continuous membrane and enclose a cisterna.
2 types: rough ER, smooth ER
Rough ER
Dotted with ribosomes.
Prominent in cells specialized for protein secretion.
Saclike and parallel stacks of cisternae.
Segregates proteins not destined for cytosol
Ribosomes
Electron-dense particles composed of 4 types of RNA and >80 proteins.
Stain blue with haemotoxylin
Ribosomes, cont
PROTEIN TRANSLATION.
In euks, RNA is synthesized in nuc. mRNA encode for AA’s, and ribosomes decode this and translate into protein.
Individual ribosomes are held together by mRNA to form polyribosomes.
Have 2 diff subunits - 60S and 40S
Smooth ER
Continuous with RER, lacks polyribosomes.
Specialized functions - synthesis of steroid hormones & phospholipids.
Smooth ER, muscle cells:
Aids in contraction (called sarcoplasmic reticulum). Sequesters & releases Ca2+ during contraction
Golgi Apparatus
Post-translational modification of proteins (adds carbs to tail of proteins).
Processes proteins, gets them into vesicles to transport outside cell.
Rough ER sends proteins to Golgi.
Golgi, cont
Has a trans face and cis face.
Cisternae near rough ER are convex, form cis face.
Opposite, concave face is trans.
Endosomes
System of vesicles & tubules in the cytosol near cell surface (early endosomes) and deeper (late endosomes)
Endosomes, cont
Contain ATP-driven proton pumps to acidify interior compartment; acidification causes separation of ligand/receptor complexes.
Receptors recycle back to PM, ligands are contained within late endosome
Lysosomes
Intracellular digestion and turnover.
Internally acidic, contain hydrolytic enzymes.
Abundant in phagocytic cells (i.e. macrophages)
Lysosomes, cont
0.05-0.5um
Packaged in trans-Golgi network.
Delivered in clathrin-coated vesicles to late endosomes forming endolysosomes, which mature into lysosomes
Primary lysosomes
not involved in digestion