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Cellular Biology > Test 2: Golgi App., Lyso, Mito, Cytosk., Nucleus > Flashcards

Test 2: Golgi App., Lyso, Mito, Cytosk., Nucleus Flashcards

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1
Q

Where do the majority of the ER-built molecules and membranes move to?

A

Golgi Apparatus

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2
Q

What does the Golgi apparatus do?

A

Packaging and receiving center of ER-built molecules and membranes.

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3
Q

The Golgi apparatus is literally part of what organelle?

A

Endoplasmic Reticulum (RER).

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4
Q

What determines the number and size of the Golgi apparatus?

A

Cellular activity.

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5
Q

Cells that ____ and ____ usually have large Golgi?

A

Synthesize and secrete.

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6
Q

What are the general functions of the Golgi? (3)

A

Finish any necessary post translational modifications of proteins received.
Package these proteins (and lipids, by default) into vesicles.
Ship vesicles to either the plasma membrane or to some other organelles.

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7
Q

Generally, can the golgi be observed in light microscopy?

A

No. (if seen it appears as a pale patch in the cytoplasm often adj. to the nucleus.

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8
Q

When observing the golgi in an electron microscope, what is seen?

A

series of 5-7 membrane-bound saccules.

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9
Q

What are the properties of the 5-7 membrane bound saccules of the golgi?

A

Each sac is slightly curved and contains a cisternae.
Sacs are often dilated at their edges.
Sacs aren’t continuous with each other.
Small vesicles often seen around the golgi.

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10
Q

What are the 4 functional compartments of the golgi cisternae?

A

cis, medial, trans, trans golgi network.

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11
Q

What does the cis compartment of the golgi do? (2)

A

Vesicles budding from ER fuse with this sac.

Newly synthesized proteins and lipids are biochemically modified here.

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12
Q

Where does the medial compartment receive its vesicles and what does it do?

A

Receives vesicles that have pinched off the edges of the cis sac.
Further biochemical modification.

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13
Q

What does the trans compartment of the golgi do? (2)

A

Further biochemical modifications are possible.
Vesicles containing modified proteins and lipids are released to the surrounding cytoplasmic environment.
(AKA the “releasing face”).

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14
Q

What is the trans golgi network (TGN)?

A

It’s an accumulation of vesicles (containing proteins and lipids) that have budded from the trans sac and have been sorted and are waiting to be shipped to an appropriate location.

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15
Q

What are 2 potential destinations for vesicles waiting in the trans golgi network?

A

Cell membrane (secretion) and lysosomes.

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16
Q

What is the enzyme that the golgi is rich in and what does it do?

A

Glycosyltransferase.

It modifies sugar chains (oligosaccharides) to create glycoproteins and glycolipids.

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17
Q

What are the 3 major functions of the golgi?

A

Lysosome formation.
Secretory vesicle formation.
Plasma membrane renewal (which is largely a default function coupled to secretory vesicle production).

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18
Q

What’s the term(s) for the elaborate system that helps accomplish the functions of the golgi?

A

Flagging/Tagging (“addressing”).

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19
Q

What does the “addressing” process in the golgi involve?

A

Modification of oligosaccharide chains that were first installed in the ER. (chains determine targeting).
Modification of these sugar chains are done by the golgi glycosyltransferases.

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20
Q

What kind of cells is the Golgi found in?

A

Metabolically active cells and secretory cells

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21
Q

What happens in the Cis Saccule of the Golgi?

A

Newly synthesized proteins and lipids are biochemically modified.
(“Forming Face”).

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22
Q

What does glycosyltransferase do in the golgi membranes?

A

Found in membranes facing cisternal sides.
Adds sugar chains to create glycoproteins/glycolipids.
Also sort proteins on cisternal side of saccules.

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23
Q

What are the 3 major functions of the Golgi?

A

Lysosomal formation.
Secretion vesicle formation.
Plasma membrane renewal.

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24
Q

What are lysosomes?

A

Membrane bound organelles that contain an array of digestive enzymes of a class know as a hydrolase.

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25
When golgi sort hydrolase into spherical packets, what does the process include?
Mannose oligosaccharide chains are installed on hydrolases in the RER (where enzymes are made). Hydrolases are shuttled to the golgi cic-compartment. In the cis golgi, the mannose "flag" is capped with phosphates by an enzyme called glucosamine phosphotransferase.
26
In which golgi compartment is there an addition of a phosphate to the mannose-6 (M-6) sugar?
Cis compartment
27
In which compartment of the golgi is there an oligosaccharide addition?
Medial compartment
28
If secretory proteins aren't separated into a lysosome (by way of posphorylated mannose oligosaccharide flags), what happens?
The TGN produces vesicles destined for exocytosis (either immediately or delayed).
29
What is the default pathway for most molecules emerging from the Golgi (and ER)?
Eventual exocytosis
30
What happens when secretory vesicles merge with the plasma membrane?
Interior contents get dumped. New phospholipids are added to the surface. Membrane-bound proteins (IMP's) are added.
31
What are the 2 forms of exocytosis (from the golgi)?
Constitutive and regulated.
32
What is constitutive exocytosis?
The default path for such vesicles. Movement to surface conducted by the cytoskeleton. Sent to surface without delay.
33
What is regulated exocytosis?
Vesicles temporarily bind to cytoskeleton for later release. | Often stimulated by Ca(2+) burst following some sort of external signal
34
What is I-Cell Disease due to?
Failure of glucosamine phosphotransferase.
35
(I-Cell Disease) | If hydrolases can't be phosphorylated, what 2 things happen?
Lysosomal enzymes will be thrown into the ECM. | Anything brought in by endocytosis will not be able to be broken down by merger with lysosomes (which are absent).
36
I-Cell disease is due to a failure of what part of the cell?
Golgi Apparatus. (ER sends Golgi a bad enzyme which it can't sort out). (Death by 5, severe retardation, skeletal deformities).
37
What organelle is considered a derivative of the Golgi?
Lysosome. | It's contents are synthesized in the RER.
38
What determines the # of lysosomes in a host cell?
Digestive activity. | Phagocytic cells have many
39
What are lysosomes rich in?
Digestive enzymes (hydrolases).
40
What do hydrolases do?
Cleave a molecule by adding water.
41
What is a primary lysosome?
Inactive, small vesicles with a homogeneous interior.
42
What is a secondary lysosome?
Occurs when a primary lysosome merges with an endosome. True digestive vesicle. Active, larger vesicles with a heterogeneous interior.
43
What is a residual body?
In a secondary lysosome, it's a small vesicle that remains if materials are undigestible. (Not too common except in long lived cells).
44
What are the 3 major functions of lysosomes?
Autophagy, heterphagy, and "external operations"
45
Explain "external operations" of a lysosome:
It's an uncommon use of lysosomes for extracellular digestion. Osteoclasts- normal bone recycling. Special neutrophilic attack (extraordinary situations).
46
What happens if ANY enzyme is missing in a lysosome?
The lysosome won't be able to fully digest what was internalized. This eventually leads to the formation of a residual body (undigestible material stored inside shrunken lysosome)
47
What causes Tay-Sachs disease?
Accumulation of lipids resulting from a single missing enzyme called B-hexosaminidase A (Hex A). If the enzyme is missing the breakdown gets stuck and lipids accumulate.
48
What are hepatocytes involved in with lysosomes?
Autophagy
49
What kind of cells have a higher number and size of mitochondia?
High metabolism/activity --> Increased number of mitochondria. (directly related to the cells activity and need for ATP).
50
Describe the outer mitochondrial membrane:
It isolates the organelle from the rest of the cytoplasm and is rich in an IMP called porin (a channel) which allows for significant free-passage (especially for incoming nutrients).
51
Describe the inner mitochondrial membrane:
shelf-like folds called cristae that cross the interior. (# of cristae is directly correlated to the ability to produce ATP. Contains proteins of the electron transport system, ATP synthesis (F1 particle), and various transporters related to oxidative phosphorylation. Also high in concentration of a phospholipid called cardiolipin
52
What does cardiolipin do in the inner mitochondrial membrane?
Decreases permeability of the membrane to small ions -especially H(+)
53
In the mitochondria, where is there an accumulation of H(+)?
Intermembrane Space
54
Describe the matrix of the mitochondria:
Fills the interior of the organelle. | Contains nucleic acid machinery (looks of DNA, ribosomes, and tRNA's) and enzymes of the Kreb's cycle.
55
What are the functional purposes of the mitochondria?
Ultimate purpose is to convert ADP into ATP (for use in chemical reactions). Oxygen is burned with metabolic food to produce carbon dioxide and water (wastes). (Heat is unavoidably produced from inefficiency).
56
What enters a mitochondria?
ADP+P, carbohydrates & fats (nutrients), and oxygen.
57
What leaves the mitochondria?
ATP (chemical energy), heat, and CO2 &H2O (wastes).
58
What are the 3 components of oxidative phosphorylation?
Glycolysis Kreb's Cycle Electron transport chain
59
What is required to phosphorylate ADP into ATP?
Oxygen
60
What happens during glycolysis?
The conversion of glucose into pyruvate in the cytoplasm. It produces a small amount of ATP. Pyruvate enters the matrix and is converted to acetyl CoA.
61
What happens during the Kreb's cycle?
Occurs in the matrix. As acetyl CoA enters a series of reactions it results in the production of CO2, electrons, and protons. Electrons and protons are received by a reducing agent (mostly NAD).
62
What happens during the electron transport system?
Occurs in/on the inner mitochondrial membrane. NADH oxidation leads to the release of H+ and e-. H+ is pumped across the IMM to the intermembrane space. e-'s are pulled along and through the IMM by way of many IMP's. The separation of charges creates potential energy.
63
What is an F1 particle?
The main agent for re-entry proteins. lollipop-shaped IMP that is more correctly called ATP synthetase. It allows H+ to re-enter the matrix as it converts an ADP to and ATP.
64
What are the 5 major protein complexes within the IMM that make up the ETS?
``` Complex 1: aka NADH dehydrogenase. Complex 2: aka fumarate reductase. Complex 3: aka cytochrome b-c. Complex 4: aka cytochrome c oxidase Complex 5: ATP synthetase. ```
65
What do cytochromes serve as in the mid section of the mitochondria?
Carriers
66
What drives the production of ATP in the mitochondria?
The controlled re-entry of H+ into the matrix.
67
What's so special about mitochondria having their own DNA (and ribosomes)?
They can do some limited transcription and translation for some of their proteins. (still, most of the mitochondrial proteins come from DNA in the nucleus).
68
What is Myoclonic epilepsy with ragged red fibers attributed to?
Failure of some mitochondria. Affected mitochondria lack critical electron transport system protein assemblies due to a mutation in mtDNA for an IMM component.
69
What are the functions that the cytoskeleton is thought to be important to performing?
Maintain cellular morphology. responsible for cellular motility (when seen). Contraction of a cell. Transport vesicles through the cytoplasm. Organize the cytoplasm. External movements.
70
What are the families of proteins in the cytoskeleton?
Microfilaments: solid rods of varying thicknesses. Microtubules: hollow tube-like rods. Protein motors: small associated globular proteins that work with these microfilaments and microtubules. Other associated proteins: variable size, shape, and number (many are microfilament cross-linkers).
71
What is the most common and best understood microfilament?
Actin
72
What are the small bead-like sub-units of actin called?
G-actin. | G-actin monomers that are assembled into a helical polymer are called F-actin
73
Describe the growing and shrinking ends of actin:
+ end: happens when ATP binds to the G-actin. | - end: Happens after hydrolysis to ADP on those proteins.
74
What are the 2 other proteins associated with actin?
Troponin and tropomyosin. | can be wound up with actin which is critical for interaction with myosin in the muscle
75
What is troponin?
``` A Ca(2+) mediated regulatory protein and it influences the rope-like tropomyosin protein. (Together they control the binding of myosin to actin by affecting access to myosin binding sites, which are present on each G-actin subunit). ```
76
What is collectively known as the "thin filament"?
Troponin and tropomyosin.
77
What is the thick microfilament?
Myosin
78
What are the 2 parts of myosin?
Head: Enzymatic part that interacts with actin. Tail: smaller part that can be assembled into complex strands with many hundreds of exposed heads.
79
What is known as the key element ("motor") of the sliding filament theory?
The myosin head. | ATP is used to change it's conformation and set up a power stroke
80
What blocks the myosin binding sites on G-actin subunits?
Tropomyosin. (No Ca2+ present). Resting cell.
81
What happens when troponin is bound to Ca2+?
Tropomyosin moves to the center of the F-actin helix (and out of the way). Contracting cell.
82
What is the terminal web?
Cross-wire actins as well as microtubules in the apical cytoplasm. Serves to maintain structural integrity.
83
What is actin's role in the membrane cytoskeleton?
Serves as a kind of intracellular membrane linker protein. | The spectrin-actin assembly is attached to the membrane by ankyrin.
84
What is responsible for organelle movement?
Microtubules (specifically actin-myosin complexes).
85
What do intermediate microfilaments do?
Tend to be tissue and cell specific, and all seem to play a structural role.
86
What are 4 of the 5 major types of intermediate microfiliaments?
Keratin, desmin, vimentin, and neurofilaments.
87
Describe keratin:
Provides flexibility and resilience. Sulfur rich protein. Major player in the biggest cell junction called a desmosome (which is an unusually strong adhering junction).
88
Describe desmin:
in muscle cells. | Links actin into myofibrils by forming z-lines.
89
Where is vimentin found?
connective tissue cells.
90
What are neurofilaments?
Structural protein in neurons that may help maintain long cytoplasmic projections.
91
What are micotubules?
Protein rods composed of tubulin dimers.
92
What are the main functions of microtubules?
Mitotic and meiotic chromosomal movements. Intracellular transport of vesicles. Ciliary and flagellar movement. (most involving movement)
93
In microtubules, what is required for movement?
Kinesin (walks towards the + end of the microtubule). | Dynein (walks towards the - end of the microtubule).
94
What is axoplasmic flow?
An important mechanism to deliver new neurotransmitters and other supplies to the terminal end of an axon.
95
What is ameboid movement?
Used by faster movers which involves rapid changes in the viscosity of cytoplasm as well as cytoskeletal geometry.
96
What is kartagener syndrome due to?
Abnormal (of missing) dynein in the axoneme. Therefore, the microtubule doublets cannot walk on each other. With no axonemal function, cilia and any flagella will fail everywhere in the body. The root cause is in the nucleus.
97
What is the nuclear envelope?
2 unit membranes that bind the nucleus. | It separates the cytoplasm from the nucleoplasm.
98
Describe a chromosome:
Made of 2 chromatids held together by a centromere. | Each centromere has 2 kinetochore proteins for attachment of spindle apparatus microtubules.
99
What is mitosis?
When a somatic cell divides. | This causes the need for nuclear contents to be accurately duplicated and separated
100
What are the 3 major phases interphase is broken down into?
G1: First growth. Growth and normal metabolic roles. (This is where most cells live their lives). S: DNA synthesis and replication. G2: Second growth. Growth and preparation for mitosis.
101
What are the 4 major phases mitosis is broken down into?
Prophase, metaphase, anaphase, telophase.
102
Describe prophase:
The first phase of chromosomal formation. Chromatin condenses by coiling to form chromosomes (with 2 chromatids). At the end of prophase, the nucleolus disappears and the nuclear envelope disintegrates. Centrosomes migrate to opposite poles and grow a spindle apparatus of microtubules.
103
Describe metaphase:
Phase of chromosomal alignment in the "middle" (equatorial plate). Spindle apparatus connects to all kinetochores.
104
Describe anaphase:
Phase of separation ("apart") of chromatids as centromeres split. Former chromatids are pulled to the respective centrosome poles of the spindle apparatus.
105
Describe telophase:
End phase of reconstruction. Newly arrived chromosomes at poles de-condense. Reversal of prophase. Cytokinesis occurs. (Contractile ring pulls plasma membrane in and pinches off).

Cellular Biology (2 decks)

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