Cell Anatomy - Organelles

Question 1

What are the problems associated with visualizing cells and their contents

Answer 1

They are tiny (10-20um) and colorless

Question 2

Light micropscopy - mechanism and resolution

Answer 2

Glass lenses & light
0.2um

Question 3

Electron microscopy - mechanism and resolution

Answer 3

Electron beams and electromagnets on the lenses
0.1nm

Question 4

Resolution:

Answer 4

the minimal distance required for two objects to be separated and seen and independent

Question 5

What is the favored technique for visualizing cells & why

Answer 5

Light microscopy
Straightforward sample prep
Inexpensive
Non-destructive
Can use dead or living cells

Question 6

What are florescent probes and why do we care

Answer 6

Small fluorescent molecules that bind to specific compounds
They can light up intracellular components

Question 7

What are fluorescent marker proteins

Answer 7

A fluorescent protein used to tag certain cellular components
Most common is green fluorescent protein (GFP)

Question 8

What is an example of how GFP is used

Answer 8

GFP gene sequence ligated into gene sequence of interest
GFP is translated by live cells
Can then be visualized with fluorescence microscopy

Question 9

How does immunofluorescence work

Answer 9

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

Question 10

Pros of EM

Answer 10

Much higher resolving power (x1,000)

Question 11

Cons of EM

Answer 11

Sample prep is more technical and takes longer
Destructive to cells
Cells must be dead and dried
Expensive

Question 12

What is transmission electron microscopy (TEM)

Answer 12

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

Question 13

What is scanning EM

Answer 13

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

Question 14

Organelle:

Answer 14

Specialized subunit of the cell with a special function, usually enclosed by its own lipid bilayer
Basically the organs of the cell

Question 15

What are the three main categories of organelles

Answer 15

Manufacture
Breakdown
Energy processing

Question 16

What organelles are in the manufacturing group?

Answer 16

Nucleus
ER
Golgi

Question 17

What organelles are in the breakdown group?

Answer 17

Proteasome
Lysosome
Peroxisome

Question 18

What organelles are in the energy processing group?

Answer 18

Mitochondria

Question 19

Organelles are distinct to what type of cells

Answer 19

Eukaryotes

Question 20

Are organelle structure and function conserved between species?

Answer 20

Yes

Question 21

Nucleus: structural features

Answer 21

-Round or elliptical
-Double membrane w/ nuclear pores
-Nucleoli
Contiguous with ER

Question 22

Nucleus: function

Answer 22

-Control center of cell
-DNA and RNA synthesis
-Nucleolus - rRNA synthesis

Question 23

ER: structural features

Answer 23

-network that extends from nucleus throught cell
-2 subdomains:
-rER - ribosomes
-sER - no ribosomes

Question 24

ER: funtion

Answer 24

-sER - lipid syntheis
-rER - protein synthesis
-Ca storage
-Initial site for protein glycosylation

Question 25

ER: system

Answer 25

Secretory pathway

Question 26

Golgi: structural features

Answer 26

-Stack of disc-like compartments -Polarity: cis face close to ER, trans face far from ER

Question 27

Golgi: function

Answer 27

-Protein sorting and modifiction -receives proteins and lipids from the ER -Extensive protein glycosylation

Question 28

Golgi: system

Answer 28

Exocytic (secretory) pathway

Question 29

Why is Golgi always capitalized?

Answer 29

Because it's named after the guy who discovered it. He has an amazing mustache

Question 30

Proteasome: structural features

Answer 30

-Protein complex -Not membrane bound -In cytoplasm and nucleus

Question 31

Proteasome: function

Answer 31

-Degrades foreign proteins in cytoplasm -Degrades cellular proteins that don't fold properly in cytoplasm and ER

Question 32

How do proteasomes know which proteins to degrade?

Answer 32

They are tagged by a small protein called ubiquitin

Question 33

Where does biogenesis and folding of proteins occur (mostly)?

Answer 33

Cytoplasm, ER lumen

Question 34

What are the steps of ubiquitination

Answer 34

1. ATP dependent conjugation of Ub and Ub activating enzyme (E1) 2. Activated Ub transferred to Ub conjugating enzyme (E2) 3. Ub transferred from E2 to target via Ub protein ligase (E3)

Question 35

Lysosomes: structural features

Answer 35

-Membrane-bound spheres -Filled with hydrolases

Question 36

Lysosomes: function

Answer 36

-Digestion of nucleic acids, proteins, lipids via endocytosis, autophagy, and phagocytosis -Contents are delivered in endosomes

Question 37

Lysosomes: system

Answer 37

Endocytic

Question 38

Is ubiquitination required for proteins to be internalized from the cell surface?

Answer 38

No, but it can be used

Question 39

Peroxisomes: structural features

Answer 39

-Membrane bound spheres -Contains enzymes involved in oxidation reactions

Question 40

Peroxisomes: functions

Answer 40

-Oxidative metabolism -Breakdown of fatty acids --> acetyl CoA -Conversion of free radicals --> peroxide -Conversion of peroxide --> water

Question 41

Mitochondria: structure

Answer 41

-Double membrane -Folds called cristae -Have their own genome!

Question 42

Mitochondria: function

Answer 42

-Powerhouse of the cell -Provides ATP via oxidative metabolism