Organization of the Cell Flashcards
4 amino acids with non-polar side chains
Glycine
Alanine
Phenylalanine
Leucine
What part of a protein dictates its ultimate localization
Aspects of the primary sequence
Signal sequences/patches
Signal sequences
Typically at the N-terminal
Removed by signal peptidases after sorting
Can code to go many different places
Chaperones
Help guide the folding process
Chaperone synthesis is responsive to increases in misfolding
Proteasome
Degrade irretrievably misfolded proteins
Quite big
Breaks proteins down to amino acids
What is added to make
1. A
2. B
blood groups?
- N-acetylgalactosamine
2. Galactose
Lipid raft
In trans Golgi
Cholesterol rich domain
Has increase concentration of TM proteins and associated future cargo
Preferentially get sorted into transport vesicles
Lysosome
Has an acidic intracellular compartment
Responsible for degradation of endocytized material
Proteasome vs lysosome
Proteasome: cytosolic multi-enzyme complex, degrades intracellular proteins that were defective or mutants
Lysosome: membrane bound organelle, degrades endocytosed material and whole organelles
Lysozyme
Made by macrophages and released constitutively
Not found in lysosomes!!
2 things that determine cell polarity
Cytoskeleton
Cell Junctions
2 major morphological types of breast tumors
Ducts
Lobules
Lobular breast carcinoma progression
Normal
Hyperplasia (proliferation, but can still see lumens)
Lobular carcinoma in situ (more dysplasia, polarity is disrupted, no lumens)
Infiltrating lobular carcinoma (loss of polarity, cells become invasive)
Microfilaments
Smallest ones
Made up of globular actin
Very dynamic
Important in cell adhesion, generation of contractile force, cell shape, and surface projections (microvilli)
Intermediate filaments
Medium sized
Formed from overlapping protein rods - very stable
Convey tensile strength within cells and across tissues
Architectural scaffolds
Tissue specific expression of different intermediate filament proteins
Different types of intermediate filament proteins in
- Epithelia
- Muscle
- CT
- Neurons
- Keratins
- Desmin
- Vimentin
- Neurofilaments
Microtubules
Cylinders of globular tubulin (polar)
Highly dynamic (cell division)
Motors can move along them
Found in the cores of motile cell surface projections (cilia, sperm)
3 parts of ALL junction/adhesion complexes
Cell surface receptors (TM proteins that bind to other receptors on other cells or ECM) Linker proteins (link complex to cytoskeleton) Cytoskeletal elements (often span from one complex to another inside the same cell)
Zonula adherens
Form a belt around the cell
Initiate cell-cell adhesion on the lateral aspect of cells
Specific proteins for 1. Cell receptors 2. Linker proteins 3. Cytoskeletal elements for zonula adherens
- Cadherins
- Catenins
- Actin
2 functions of catenins
Structural: link cadherins to actin
Proliferative signal transduction: when not in junction can move to nucleus and upregulate cyclin D expression
Tight junctions
Receptors bring the membranes on adjacent cells very close together so they form a barrier
Desmosomes
Also called macula densa
Not a belt (spots)
Can be located anywhere along lateral surface
Linked to intermediate filaments (increases tensile strength)
Prominent in epithelia of skin
Gap junctions
Formed out of connexons
Channels that link cells and allow for the passage of small molecules and ions between cells
Communicating junctions
Hemidesmosomes
Anchor cells to ECM
Receptors are heterophilic (bind different proteins)
Attached to intermediate filaments inside the cell
Very stable
Focal adhesions
Anchor cells to ECM
Cytoskeletal elements are actin filaments
Can generate contractile force
Critical for cell migration
What happens in
- G1
- S phase
- G2
- cell growth
- DNA synthesis
- chromosome condensation, mitotic spindle preparation
