Cell Biology 2

Question 1

What are the three major units of the cytoskeleton made up of?

Answer 1

Microtubules non-branching, long hollow cylinders made up of tubulin heterodimers
Actin are double stranded linear helical arrays made up of G-actin monomers
Intermediate filaments are rope- like fibers made up of antiparallel tetra ears of 2 rod-like dimers

Question 2

What are the four major functions of the cytoskeleton?

Answer 2

1) structure and support
2) intracellular transport
3) contractility and motility
4) spatial organization

Question 3

Everything has a job, what is the microtubules job?

Answer 3

Microtubules establish cell shape and brace internal organelles
Other functions:cell division, intracellular transport, recycling of components from the Golgi to the ER, and cell motility

Question 4

What is the basic structure of the microtubule?

Answer 4

Two globular polypeptides (alpha and beta) form the tubulin heterodimers
They are labile and polar structures
Microtubule associated proteins (MAPs) stabilize microtubules or bind microtubules to other cell organelles. MAPs are known as motor proteins.

Question 5

What are the two types of microtubule motor proteins? What do they do?

Answer 5

Dyneins: move organelles to the minus end
Kinesins: move organelles toward the plus end

Motor proteins have protein chains that make up two heads, a neck, and a tail that binds cargo. The heads walk along the cytoskeleton fiber. ATP is the energy source

Question 6

What are some drugs that affect the microtubules in the mitotic spindle?

Answer 6

Mitotic spindle is sensitive to agents that block microtubule polymerization or stabilize microtubules

• Vinblastine is used for Hodgkin disease, advanced testicular carcinoma and breast cancer
• Vincristine is used for acute leukemia and other lymphomas
• Taxol is used for breast,lung and ovarian cancer as well as Kaposi’s sarcoma

Question 7

Describe actin filaments.

Answer 7

They are polar structures
The faster growing end is called the barbed end
The slow growing end is called the minus end
They are more flexible, thinner and shorter than microtubules
Involved in movement of non-muscle cells and are a part of the contractile apparatus of muscle cells

Question 8

What kind of bundles do actin filaments form?

Answer 8

Stress bundles extended throughout the cell

They are also involved in membrane stablilzation

Question 9

What are the two types of intermediate filaments in epithelial cells?

Answer 9

Keratin-> from nucleus to plasma membrane

Lamin-> me shower underlying the nuclear membrane

Question 10

What do intermediate filaments do?

Answer 10

Strong, flexible polymers that provide mechanical support for cells that are subject to external and internal physical forces
Helps prevent excessive stretching of cells

Question 11

What are the 6 classes of intermediate filaments?

Answer 11

Keratins, Vimentin, Vimentin-like, neurofilaments, lamins and beaded filaments.

Question 12

Describe intermediate filaments.

Answer 12

They consists of polypeptides with an N-terminal tail and a C-terminal head and a central rod
Form coiled coil dimers
Eight tetramers associate laterally to form a unit length of intermediate filament
Not polar structures and no motor proteins

Question 13

What are some diseases caused by a malfunction in intermediate filaments?

Answer 13

Mutations in genes encoding the intermediate filament protein keratin leads to skin blistering disease called Epidermolysis bullosa simplex

Question 14

What are the main functions of the ribosome?

Answer 14

Splicing of introns and linking of exons

ribosomes can be bound or free

Question 15

Talk about the subunits of the ribosome.

Answer 15

There is a small subunit and a large subunit. The small subunit is where tRNA matches codons while the large subunit catalyzes so the formation of peptide bonds.
Eukaryotes have 80s while prokaryotes have 70s.
Ribosomal subunits are synthesizes and reassembled in the nucleoli sand reach the cytoplasm via nuclear pores
The synthesis of all polypeptides begins in the cytoplasm as the large and small ribosomal subunits associate wither hotter and an mRNA

Question 16

How does antibiotics fight infection in our bodies if both eukaryotes and prokaryotes have ribosomes?

Answer 16

They have different types. Eukaryotes have 80s and prokaryotes have 70s. Antibiotics are directed towards prokaryotic ribosomes

Question 17

What is a type of disease that can come from the malfunctions of a ribosome?

Answer 17

Mutations in the L10/uL16 cause disorders called ribosompathies. (T-ALL, T-cell acute lymphoblastic leukemia

Question 18

Free ribosomes vs Bound ribosomes

Answer 18

Free ribosomes: go to either cytosol, import to the nucleus, peroxisomes or mitochondrion
-called post-translational targeting/import
Bound ribosomes: derived rom the ER, Golgi, plasma membrane and lysosome
-co-translational targeting/import

Question 19

What are some ER subdomains?

Answer 19

Outer membrane of nuclear envelope
ER export domains
Smooth ER
RER

Question 20

Name a disease that affect the ER.

Answer 20

Hydropic swelling found in the liver of patients with toxic hepatic injury.
Mutations in the ER/enlarged dilated Cisternae

Question 21

How are ribosomes targeted to the ER membrane?

Answer 21

By an amino acid sequence known as the signal sequence found at the N-terminus of the polypeptide
Signal sequence is part of the mechanism that ribosomes attach to the ER

Question 22

Where is the SER located?

Answer 22

It’s one of the ER subdomains and can be directly connected to the ER

Question 23

What is the job of the SER?

Answer 23

Abundant in cell types active in lipid metabolism
Functions varies by tissue
Involved in the detoxification of a wide variety of organic compounds by oxidative enzyme in the liver
Most universal role of the SER is the storage and sudden releases of calcium ions

Question 24

What is the job of the Golgi complex?

Answer 24

Processes membrane packaged proteins made by the RER, sorts them and packages them for transport to other parts of the cell or outside the cell

Question 25

What is the function of the Cis Golgi, medial Golgi and Trans Golgi?

Answer 25

Cis: proteins are transported to the Cis Goldie by transfer vesicles through the ER -Golgi intermediate compartment. Here is the phosphorylation of mannose residues and the remove of mannose residues. Medial: here terminal glycosylation occurs Trans: Sulfations and phosphorylation of amino acids occur. Sorting in the Trans network is performed by specific receptor proteins

Question 26

What is a disease that if affected by mutations in the Golgi?

Answer 26

I-cell disease is a defect in adding a mannose -G-phosphate moiety in the Cis Golgi to newly synthesized lysosomal enzymes

Question 27

What is the function of lysosomes?

Answer 27

Functions as the cells intracellular digestion system procession either material ingested by the cell or cellular components. They are plentiful in cells that digest and destroy cells Part of an acid vesicle system They form late endosomes, irregularly shaped vesicles that reside deep in the cytoplasm and contain both lysosomal hydrolysis and lysosomal membrane proteins

Question 28

What is a disease associated with lysosomes?

Answer 28

Tay Sachs diesels is where harmful amounts of a ganglioside called GM2 accumulates in nerve cells because of a deficient lysosomal enzyme hexaminidase

Question 29

What do peroxisomes do?

Answer 29

They are involved in the oxidation of several substrates, particularly B oxidation of long chain fatty acids Provide oxygen dependent oxidation of substrates Breaks down H2O2 into water and oxygen Reactions are used in oxidative detoxification of toxic compounds Also synthesizes socialized phospholipids -plasmalogens

Question 30

Where are mitochondria found?

Answer 30

In all cells except RBCs and terminal keratinocytes. In skeletal and cardia muscle they are concentrated in specific areas where there is high energy utilization in the form of ATP Produces ATP by oxidative phosphorylation

Question 31

What are some major features of mitochondria?

Answer 31

It has two membranes -a smooth outer membrane -folded inner membrane There is an intermembranous space and matrix space Folds of inner membrane are called crusade and they increase surface area The inner membrane is the site of ATP formation and reactions related to electron transport and oxidative phosphorylation *the number of cristae is directly related to energy requirement*

Question 32

What are the functions of mitochondria?

Answer 32

``` ATP production (energy producers of the cell) Hub of cellular processes like calcium signaling, apoptosis, heme biosynthesis, cholesterol metabolism, hormone synthesis and reactive oxygen species (ROS) production ```

Question 33

What is a disease associated with the mitochondria?

Answer 33

Mitochondrial myopathies that cause major muscle problems and Kearns-Sayre syndrome which affects eye movement due to abnormalities in mitochondrial DNA

Question 34

In microtubules growing happens on what end? Disassembly happens where?

Answer 34

Plus end, minus end

Question 35

Where is the minus end embedded in microtubules?

Answer 35

MTOC