Cell Bio Final

Front 1

State of balance between cell proliferation, differentiation, and death:

Back 1

Homeostasis

Front 2

State of temporarily or reversibly ceasing to divide:

Back 2

Quiescence, G0 phase

Front 3

State of permanent cessation of cell division due to age or accumulated DNA damage:

Back 3

Senescence

Front 4

Embryo cell division cycle:

Back 4

20 minutes

Front 5

Skin cell division cycle:

Back 5

12-24 hours

Front 6

Liver cell division cycle:

Back 6

1-2 years

Front 7

Mature nerve and muscle cell division cycle:

Back 7

After maturity, never (permanent G0)

Front 8

Controls cell cycle progression:

Back 8

Cell cycle regulators

Front 9

Categorization of cell cycle mediators:

Back 9

Cyclins or cyclin-dependent kinases (CDKs)

Front 10

Categories of cyclins:

Back 10

D, E, A, B

Front 11

What binds to form activated complexes that trigger events in the cell cycle?

Back 11

Cyclins and CDK partner proteins

Front 12

CDK presence and activity:

Back 12

Always present, only active depending on concentration of cyclins

Front 13

What happens when cyclin forms a complex with CDK?

Back 13

The CDK becomes phosphorylated, stimulates it's kinase activity, then catalyze the phosphorylation of substrate proteins to advance the cell cycle past a checkpoint

Front 14

What is the tumor suppressor checkpoint?

Back 14

G1

Front 15

What tumor suppressor protein halts a cell in the resting G1 phase of cell cycle?

Back 15

Retinoblastoma

Front 16

What does the RB protein do in resting cells?

Back 16

Contains phosphorylated amino acids; in that state, it blocks entry into S phase by binding to transcription factor W2 which is critical for that transition

Front 17

What does the RB protein do in actively cycling cells?

Back 17

It is hyperphosphorylated because of growth factor stimulation and signaling via MAP kinase cascade. In that form, it can't inhibit E2F binding to DNA so the transition to S phase continues

Front 18

Tumor suppressor protein stimulates CKI transcription to halt cell cycle in G1:

Back 18

p53

Front 19

How and why does p53 halt cell cycle?

Back 19

p21, to allow for repair. If irreparable, triggers apoptosis

Front 20

What happens if p53 mutates?

Back 20

Unregulated cell cycle progression, 50% of cancers show mutated p53

Front 21

What checkpoint is between S phase and mitosis?

Back 21

G2

Front 22

Antimetabolites:

Back 22

Compounds structurally related to normal cellular components

Front 23

When and how do antimetabolites exert an effect on cancer cells?

Back 23

During S phase, they inhibit the synthesis of nucleotide precursors and compete with nucleotides in DNA and RNA synthesis

Front 24

How do mitotic spindle poisons suppress tumors?

Back 24

During M phase (specifically metaphase) they bind to tubulin and disrupt the spindle apparatus on microtubules so chromosomes cannot segregate

Front 25

2 ways cells die:

Back 25

Necrosis and apoptosis

Front 26

Passive pathological process involving simultaneous death of cells in groups:

Back 26

Necrosis

Front 27

Necrosis is induced by:

Back 27

Cellular injury or accident

Front 28

What happens to cells that die by necrosis?

Back 28

Increase in volume, lyse, and release intracellular contents (sometimes inducing inflammatory response)

Front 29

LDH enzyme and necrosis:

Back 29

Released from dying necrotic cells so it appears in blood work and can be used as a general marker of necrotic cell death and aid in diagnosis

Front 30

Programmed cell death:

Back 30

Apoptosis (intracellular suicide)

Front 31

Physical changes during apoptosis:

Back 31

Cells shrink (don't lyse) and portions of membrane bud off (bleb)

Front 32

What membrane phospholipid switches to the outer leaflet during apoptosis?

Back 32

Phosphatidylserine

Front 33

What happens to apoptotic cells once the phosphate changes leaflets?

Back 33

Phagocytic cells bind to phosphatidylserine and reduce risk of inflammation so no extensive damage is done to neighboring cells

Front 34

Necrosis vs. Apoptosis

Back 34

Necrosis is traumatic causing widespread cell death, tissue damage, and inflammation. Apoptosis can eliminate harmful/damaged cells to improve survival of others

Front 35

First step of apoptosis:

Back 35

Stimulation of tumor suppressor gene p53 to stop cell cycle and start apoptosis

Front 36

Effect of mutant p53 on apoptosis:

Back 36

Cells continue to divide and cannot initiate apoptosis so they damage the organism

Front 37

Importance of apoptosis during development:

Back 37

Excess cells must be removed for normal development to occur

Front 38

What happens to nerve cells during development?

Back 38

More than half undergo apoptosis soon after they are formed

Front 39

How does apoptosis "sculpt" developing tissue?

Back 39

Remove certain tissue cells to form things like digits normally

Front 40

How does apoptosis effect the immune system?

Back 40

Removing auto-reactive T cells by negative selection in the thymus during development

Front 41

Homeostasis:

Back 41

Balance between cell division and death

Front 42

2 major pathways of apoptosis:

Back 42

Mitochondrial-mediated and death receptor pathways

Front 43

Mitochondrial-mediated pathway of apoptosis:

Back 43

Bax is induced and inserted into mitochondrial membrane to form a channel for cytochrome c which triggers formation of the apoptosome in the cytoplasm

Front 44

Complex of apoptosome:

Back 44

Apaf-1 and caspase-9

Front 45

What happens to caspase-9 in apoptosome?

Back 45

Proteolytically activates caspase-3

Front 46

What does caspase-3 do in apoptosis?

Back 46

Cleaves and destroys cellular proteins and DNA to cause cell death

Front 47

Fas and TNFR:

Back 47

Death receptors

Front 48

How do death receptors initiate apoptosis?

Back 48

External signals transmitted to death machinery, caspase-8, and caspase-3

Front 49

Proteases:

Back 49

Enzymes whose substrates are proteins

Front 50

Caspases:

Back 50

Family of proteases, major effectors of apoptotic cell death

Front 51

Classification and function of caspases:

Back 51

Initiator (8&9 cleave inactive proenzyme forms of effector capsases to activate them) and effector (3,6&7 proteolytically cleave protein substrates to cause apoptosis)

Front 52

Targets of capsases include:

Back 52

Nuclear and cytoplasmic proteins

Front 53

Members of Bcl-2 family in apoptosis:

Back 53

Prosurvival (Bcl-2 and Bcl-xL) and prodeath (Bak and Bax)

Front 54

DNA laddering:

Back 54

Visualization of DANA to detect that apoptosis has occurred

Front 55

TUNEL:

Back 55

Detects DNA fragmentation based on presence of strand breaks or nicks in DNA

Front 56

Replicative span of cells is limited and referred to as:

Back 56

Replicative senescence

Front 57

Replicative senescence depends on what aspect of cell division?

Back 57

Number of divisions, not amount of time taken

Front 58

How do cells reach their limit of cell divisions?

Back 58

With each replication, telomeres shorten until they stop functioning

Front 59

What happens when cells fail to senesce?

Back 59

They proliferate and can develop errors in chromosomes that can result in cancer

Front 60

Characteristics of senescent cells:

Back 60

State cannot be reversed, cannot replicate, are viable and metabolically active, survive long term, and resist apoptosis

Front 61

Senescent cells express what kind of enzyme activity?

Back 61

Beta-galactosidase (used as biomarker)

Front 62

When does growth arrest of senescent cells occur and what accompanies it?

Back 62

G1 phase and an increased expression of cell cycle inhibitors like p21and p16

Front 63

Example of age-old remodeling of chromatin:

Back 63

Increased methylation at specific sites

Front 64

Sirtuins:

Back 64

Class of proteins that protect cell from age-old decline in function by removing acetyl groups from lysine residues in the presence of NAD+

Front 65

RecQ helicase:

Back 65

Unwinds DNA and aids in replication

Front 66

How does again affect stem cells?

Back 66

Affects ability to produce undifferentiated progeny and differentiated cells but NOT ability to self-renew

Front 67

HGPSyndrome is cause by a mutation in what gene?

Back 67

Prelamin A

Front 68

Sequence of duplication for cells:

Back 68

Cell cycle

Front 69

3 distinct stages of cell cycle:

Back 69

Interphase, mitosis, and cytokinesis

Front 70

Interphase:

Back 70

Period between successive rounds of nuclear division, distinguished by cellular growth and new synthesis of DNA

Front 71

1st phase of interphase:

Back 71

G1; cells are active functioning, growing and copying cell contents except DNA

Front 72

Mature cells remain at rest in what phase?

Back 72

G0

Front 73

Quality control periods in cell cycle:

Back 73

Checkpoints; if cell can't pass restriction point, it will be repaired or signaled for apoptosis

Front 74

Conditions to pass G1 checkpoint:

Back 74

Signals tell cells to divide, cells have plenty of nutrients, DNA in good condition, cells large enough to divide

Front 75

Phase in which cells copy DNA:

Back 75

S phase, DNA replication/synthesis in which each of 46 chromosomes is copied to form a sister chromatid

Front 76

Conditions to pass G2 checkpoint after S phase:

Back 76

DNA not damaged, cell copied all chromosomes, signals tell the cell to proceed into mitosis

Front 77

Cell structure responsible for separating pairs of chromosomes:

Back 77

Mitotic spindle

Front 78

Kinetochores:

Back 78

Protein clusters that attach to the replicated chromosomes at their centromeres

Front 79

Prophase:

Back 79

Chromosomes coil up tightly (condensation), forms 2 chromatids connected to each other at the centromere, the nucleolus disassembles

Front 80

Prometaphase:

Back 80

Disassembly of nuclear envelope, spindle microtubules bind to kinetochores and chromosomes are pulled by microtubules of the spindle

Front 81

Metaphase:

Back 81

Cells organize the chromosomes, at checkpoint it checks that chromosomes are attached to the mitotic spindle

Front 82

Anaphase:

Back 82

Chromosomes are separated as sister chromatids to opposite sides of the cell, then chromosomes again

Front 83

Telophase:

Back 83

Ends mitosis by reversing prophase: chromosomes decondense, nuclear membrane reforms, mitotic spindle breaks down, nucleoli reform

Front 84

Cytokinesis:

Back 84

Separation of cytoplasm (forms cleavage furrow in animal cells)

Front 85

Aurora A kinase:

Back 85

Fxns. in prophase, critical for proper formation of mitotic spindle

Front 86

Aurora B kinase:

Back 86

Fxns. in attachment of mitotic spindle to centromere and in cleavage furrow formation

Front 87

Aurora C kinase:

Back 87

Don't know how it fxns. but it's in germ cells

Front 88

What happens to proteins synthesized on bound ribosomes?

Back 88

They are secreted from the cell unless they have the right signal to direct them to an intracellular location

Front 89

What happens to proteins synthesized on free ribosomes?

Back 89

They remain in cytosol

Front 90

Signal sequences:

Back 90

Ribosomes on ER the direct proteins to locations where they can be modified to be functional (act as address labels)

Front 91

Signal recognition particles:

Back 91

Cytosolic compounds composed of protein and RNA that facilitate ribosomes' attachment to ER

Front 92

What immediately happens to proteins upon entry to the ER?

Back 92

They are glycosylated (carbohydrate added to them); called N-linked glycosylation

Front 93

Transitional element:

Back 93

Area of smooth ER that surrounds and encloses new proteins until it buds off to become a transport vesicle

Front 94

3 main regions of Golgi complex:

Back 94

Cis, medial, and trans

Front 95

Lysosomes:

Back 95

Membrane-enclosed organelles with acidic internal pH that contain potent enzymes called acid hydrolases

Front 96

Constitutive secretion:

Back 96

Vesicles carrying most secretory proteins leave the Trans Golgi network (TGN) in a continuous process fuse with the nearby plasma membrane

Front 97

Regulated secretion:

Back 97

Other proteins are released from cells only at certain times in a discontinuous process also known as exocytosis

Front 98

How are proteins maintained in unfolded form before entry to mitochondria?

Back 98

Binding of chaperone proteins

Front 99

Cause of Zellweger syndrome:

Back 99

Defect in transport to peroxisomes in liver, kidneys, and brain

Front 100

ATP-dependent pathway for proteasomal degradation involves what protein?

Back 100

Ubiquitin (tags proteins for destruction by covalent attachment and degradation of the proteolytic complex called the proteosome)

Front 101

Central core of proteosome:

Back 101

20s, involved in proteolysis

Front 102

Proteosome recognition and binding of polyubiquitinated proteins regulatory particle:

Back 102

19s, removal of ubiquitin, unfolding the protein substrate, and translocation into central core

Front 103

Microfilaments:

Back 103

Made of protein actin, proteins that make the muscle cell contract, pinch animal cells in two during division, allow cells like amoebae to crawl

Front 104

Microtubules:

Back 104

Made of protein tubulin, inside cilia and flagella, move chromosomes during cell division

Front 105

Intermediate filaments:

Back 105

Made of various proteins, act as reinforcing proteins

Front 106

Where is actin localized?

Back 106

Cell cortex

Front 107

Functions of actin:

Back 107

In muscle cells: contraction. In non-muscle cells: regulation of physiological state of cytosol, cell movement, formation of contractile rings in cell division

Front 108

"Treadmilling":

Back 108

Process of addition and subtraction of G-actin monomers

Front 109

Spectrin:

Back 109

Protein that strengthens and supports RBC membrane

Front 110

Spherocytosis:

Back 110

Spectrin deficiency resulting in spherical RBCs that are fragile and susceptible to lysis

Front 111

Defects in dystrophin cause:

Back 111

Muscular dystrophy

Front 112

Four classes of intermediate filaments (IFs):

Back 112

Keratin, vimentin, neurofilaments, nuclear

Front 113

Microtubules and the centrosome:

Back 113

They grow out from it and it regulates the number, location, and cytoplasmic orientation of them

Front 114

Protofilaments:

Back 114

Linear chains of alpha/beta tubulin heterodimers

Front 115

Dynein:

Back 115

Microtubule-binding protein that generates the sliding force between microtubules

Front 116

Dyneins vs. kinesins

Back 116

Dyneins move toward centrosome, kinesins move away