Module 7

Question 1

What is homeostasis?

Answer 1

Steady internal conditions maintained by living systems.

Question 2

What does homeostasis involve?

Answer 2

Natural resistance to change maintained by regulatory mechanisms.

Question 3

What are the key components of cell homeostasis?

Answer 3

Cell membranes and intracellular organelles.

Question 4

How is homeostasis achieved at the cellular level?

Answer 4

Through units balancing variables within set limits.

Question 5

What are the four units in homeostasis mechanisms?

Answer 5

Stimulus, Sensor/Receptor, Control Unit, Effector.

Question 6

What is the role of the stimulus in homeostasis?

Answer 6

Indicates changes in the system and initiates the homeostasis process.

Question 7

What does the sensor do in homeostasis?

Answer 7

Monitors changes and sends information to the control unit.

Question 8

What function does the control unit serve?

Answer 8

Compares values and activates effectors to counteract the stimulus.

Question 9

What are effectors in homeostasis?

Answer 9

Cellular pathways activated to bring variables back to normal.

Question 10

What variables are regulated in homeostasis?

Answer 10

pH, ion concentrations, energy reserves, metabolites, and cell size.

Question 11

What systems are discussed in homeostasis?

Answer 11

Cell Fate, Cell Death/Apoptosis, Transcriptional Adjustments, etc.

Question 12

What is the role of insulin in blood glucose homeostasis?

Answer 12

Reduces blood glucose by increasing uptake and stimulating glycogen synthesis.

Question 13

What happens when blood glucose levels rise?

Answer 13

Triggers insulin secretion from pancreatic β cells.

Question 14

Describe the process of insulin release.

Answer 14

Glucose entry via GLUT2, ATP production, depolarization, and calcium influx.

Question 15

What effect does insulin have on glucagon synthesis?

Answer 15

Inhibits glucagon synthesis and gluconeogenesis.

Question 16

How do adipocytes function in relation to insulin?

Answer 16

Store energy, converting glucose and fatty acids into lipids; induce GLUT4 translocation.

Question 17

What role does the SNARE complex play in insulin release?

Answer 17

Mediates vesicle fusion for insulin release.

Question 18

What are visualization techniques for studying insulin exocytosis?

Answer 18

TIRF Microscopy and IRAP-pHluorin.

Question 19

What is the significance of Rab GTPases in exocytosis?

Answer 19

Crucial for GLUT4 vesicle translocation and identification.

Question 20

What is mTORC1?

Answer 20

A protein kinase complex that regulates cell growth by integrating signals from growth factors and nutrient levels.

Question 21

What is required for cell division?

Answer 21

Stimulation by growth factors and sufficient amino acids, nucleotides, and energy sources (ATP).

Question 22

What processes does active mTORC1 regulate?

Answer 22

mRNA translation, ribosome biogenesis, lipid and nucleotide synthesis, and it inhibits autophagy.

Question 23

Where is the mTORC1 complex assembled?

Answer 23

On the cytosolic surface of lysosomes.

Question 24

What signals does mTORC1 integrate for activation?

Answer 24

Nutrient availability (e.g., amino acids) and growth factors.

Question 25

What happens to mTORC1 in starved cells?

Answer 25

It remains in the cytosol; recruitment occurs when amino acids are added.

Question 26

Why are lysosomes important for mTORC1?

Answer 26

They recycle proteins and release amino acids, facilitating nutrient sensing.

Question 27

How is mTORC1 recruited to lysosomes?

Answer 27

By small GTP-binding proteins RagA and RagC, anchored by Ragulator.

Question 28

Which amino acids activate mTORC1?

Answer 28

Leucine (essential) and arginine (semi-essential).

Question 29

What is the role of SLC38A9?

Answer 29

A transporter that localizes to lysosomes and transports essential amino acids into the cytosol.

Question 30

What occurs when SLC38A9 is knocked out?

Answer 30

Increased lysosomal accumulation of essential amino acids.

Question 31

What are GATOR1 and GATOR2?

Answer 31

Protein complexes that regulate mTORC1 activity in response to amino acid levels.

Question 32

What do Sestrin and CASTOR proteins sense?

Answer 32

Sestrin senses leucine, while CASTOR senses arginine.

Question 33

What happens when amino acids are depleted?

Answer 33

Sestrin and CASTOR bind to GATOR2, activating GATOR1, which prevents mTORC1 activation.

Question 34

How does mTORC1 become activated?

Answer 34

It requires both amino acid sensing and proximity to Rheb, which activates its kinase activity.

Question 35

What is TFEB's role in the cell?

Answer 35

It regulates lysosomal biogenesis and autophagy through the CLEAR network.

Question 36

How does mTORC1 affect TFEB?

Answer 36

mTORC1 inhibits TFEB under nutrient-rich conditions, while starvation promotes TFEB's nuclear accumulation.

Question 37

What are the implications of mTORC1 signaling?

Answer 37

It integrates multiple signals for growth and metabolism, impacting diseases like cancer and aging.

Question 38

What are the primary control points of the cell cycle?

Answer 38

G1-S transition, G2-M transition, M phase checkpoint.

Question 39

What is programmed cell death (PCD)?

Answer 39

Genetically regulated process essential for homeostasis (e.g., apoptosis, necroptosis).

Question 40

What are the main forms of non-inflammatory cell death?

Answer 40

Apoptosis and autophagy.

Question 41

What distinguishes necrosis from apoptosis?

Answer 41

Necrosis is unregulated, causing inflammation; apoptosis is controlled and non-inflammatory.

Question 42

Describe the morphological changes during apoptosis.

Answer 42

Chromatin condensation, cytoplasmic condensation, fragmentation, and blebbing.

Question 43

What characterizes ferroptosis?

Answer 43

Iron accumulation and lipid peroxidation, independent of caspases.

Question 44

How does necroptosis occur?

Answer 44

TNF-alpha activates RIPK3 and MLKL, disrupting membranes and triggering an immune response.

Question 45

What triggers lysosome-dependent cell death (LDCD)?

Answer 45

Factors destabilizing lysosomal membranes, releasing enzymes due to stress or toxins.

Question 46

How are caspases involved in apoptosis?

Answer 46

Caspases cleave proteins to regulate and execute apoptosis.

Question 47

What are the two main apoptotic pathways?

Answer 47

Extrinsic pathway (external signals) and intrinsic pathway (internal stress signals).

Question 48

How is the extrinsic apoptotic pathway activated?

Answer 48

Through death receptors binding to ligands, forming a DISC that activates caspases.

Question 49

What role does cytochrome c play in the intrinsic pathway?

Answer 49

Released from mitochondria to activate Apaf1, forming an apoptosome and recruiting caspase 9.

Question 50

What is the function of Bcl2 family proteins?

Answer 50

Regulate mitochondrial integrity; pro-apoptotic promote death, anti-apoptotic prevent it.

Question 51

How do extracellular survival factors affect apoptosis?

Answer 51

They inhibit apoptosis by increasing anti-apoptotic proteins or blocking pro-apoptotic factors.

Question 52

What metabolites are released by apoptotic cells?

Answer 52

Spermidine, creatine, AMP, GMP, G3P, ATP; influence gene expression to suppress inflammation.