Cell Anatomy - Organelles Flashcards
What are the problems associated with visualizing cells and their contents
They are tiny (10-20um) and colorless
Light micropscopy - mechanism and resolution
Glass lenses & light
0.2um
Electron microscopy - mechanism and resolution
Electron beams and electromagnets on the lenses
0.1nm
Resolution:
the minimal distance required for two objects to be separated and seen and independent
What is the favored technique for visualizing cells & why
Light microscopy
Straightforward sample prep
Inexpensive
Non-destructive
Can use dead or living cells
What are florescent probes and why do we care
Small fluorescent molecules that bind to specific compounds
They can light up intracellular components
What are fluorescent marker proteins
A fluorescent protein used to tag certain cellular components
Most common is green fluorescent protein (GFP)
What is an example of how GFP is used
GFP gene sequence ligated into gene sequence of interest
GFP is translated by live cells
Can then be visualized with fluorescence microscopy
How does immunofluorescence work
Antigen A of interest is bound by primary antibody
Secondary antibody with fluorescent marker attaches to primary antibody
Fluorescent emission is viewed via fluorescence microscopy
Cells are DEAD for this, but not for GFP
Pros of EM
Much higher resolving power (x1,000)
Cons of EM
Sample prep is more technical and takes longer
Destructive to cells
Cells must be dead and dried
Expensive
What is transmission electron microscopy (TEM)
Similar to light microscopy but larger
Samples stained w electron-dense materials
Image collected based on how electrons move through the sample
Sliced, 2D image
What is scanning EM
Smaller, simpler & cheaper than TEM
Samples coated w electron dense heavy metals
Image collected based on electrons scattering off of the sample’s surface
3D image
Organelle:
Specialized subunit of the cell with a special function, usually enclosed by its own lipid bilayer
Basically the organs of the cell
What are the three main categories of organelles
Manufacture
Breakdown
Energy processing
What organelles are in the manufacturing group?
Nucleus
ER
Golgi
What organelles are in the breakdown group?
Proteasome
Lysosome
Peroxisome
What organelles are in the energy processing group?
Mitochondria
Organelles are distinct to what type of cells
Eukaryotes
Are organelle structure and function conserved between species?
Yes
Nucleus: structural features
-Round or elliptical
-Double membrane w/ nuclear pores
-Nucleoli
Contiguous with ER
Nucleus: function
-Control center of cell
-DNA and RNA synthesis
-Nucleolus - rRNA synthesis
ER: structural features
-network that extends from nucleus throught cell
-2 subdomains:
-rER - ribosomes
-sER - no ribosomes
ER: funtion
-sER - lipid syntheis
-rER - protein synthesis
-Ca storage
-Initial site for protein glycosylation
ER: system
Secretory pathway
Golgi: structural features
-Stack of disc-like compartments
-Polarity: cis face close to ER, trans face far from ER
Golgi: function
-Protein sorting and modifiction
-receives proteins and lipids from the ER
-Extensive protein glycosylation
Golgi: system
Exocytic (secretory) pathway
Why is Golgi always capitalized?
Because it’s named after the guy who discovered it. He has an amazing mustache
Proteasome: structural features
-Protein complex
-Not membrane bound
-In cytoplasm and nucleus
Proteasome: function
-Degrades foreign proteins in cytoplasm
-Degrades cellular proteins that don’t fold properly in cytoplasm and ER
How do proteasomes know which proteins to degrade?
They are tagged by a small protein called ubiquitin
Where does biogenesis and folding of proteins occur (mostly)?
Cytoplasm, ER lumen
What are the steps of ubiquitination
- ATP dependent conjugation of Ub and Ub activating enzyme (E1)
- Activated Ub transferred to Ub conjugating enzyme (E2)
- Ub transferred from E2 to target via Ub protein ligase (E3)
Lysosomes: structural features
-Membrane-bound spheres
-Filled with hydrolases
Lysosomes: function
-Digestion of nucleic acids, proteins, lipids
via endocytosis, autophagy, and phagocytosis
-Contents are delivered in endosomes
Lysosomes: system
Endocytic
Is ubiquitination required for proteins to be internalized from the cell surface?
No, but it can be used
Peroxisomes: structural features
-Membrane bound spheres
-Contains enzymes involved in oxidation reactions
Peroxisomes: functions
-Oxidative metabolism
-Breakdown of fatty acids –> acetyl CoA
-Conversion of free radicals –> peroxide
-Conversion of peroxide –> water
Mitochondria: structure
-Double membrane
-Folds called cristae
-Have their own genome!
Mitochondria: function
-Powerhouse of the cell
-Provides ATP via oxidative metabolism
