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ANAT 365 - Cellular Trafficking > Cell Biology of Metabolism > Flashcards

Cell Biology of Metabolism Flashcards

1
Q

Metabolism is defined as the ______________ processes occurring within a living cell or organism that are necessary for the _______________ of life

A

Chemical; maintenance

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2
Q

Metabolism studies how nutrients are being used to make _________________

A

Energy

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3
Q

Insulin is produced in the __________ cells, which make up to ____________% of the cells in the _____________

A

Beta; 1-2; pancreas

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4
Q

Insulin is secreted in response to __________ levels of ______________ in the blood

A

High; glucose

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5
Q

Insulin is produced and packaged into _________ ___________ ___________ in the ___________

A

Dense core granules; Golgi

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6
Q

How is bioactive insulin produced?

A

Pro-insulin in the Golgi matures as it moves to the cell surface because the vesicle acidifies, activating proteases like PC2 to cleave pro-insulin and produce the active form
Cleavage of signal peptide and formation of disulfide bonds

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7
Q

When are mature insulin granules secreted?

A

In response to an external stimulus (glucose or hormone signals)

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8
Q

Which steps are necessary for the release of insulin in granules?
i. Glucose taken up by GLUT2 receptor on beta cells
ii. Breakdown of glucose into energy via glycolysis in mitochondria
iii. ATP signaling for inhibition of K+ channels
iv. Ca++ channels signal secretion of insulin granules
v. Insulin breakdown inside beta cell

A

i, ii, iii, iv

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9
Q

Which of the following steps support the first or second phase of insulin secretion?
i. F-actin is broken down by glucose entry and calcium release, allowing the release of vesicles to the PM
ii. Pre-docked vesicles release stimulated by calcium through a “stimulus-secretion” coupling pathway
iii. Glucose stimulates granule recruitment to PM on microtubules

A

i. First phase
ii First phase
iii. Second phase

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10
Q

Where is glucose stored?

A

Muscle and adipose tissue

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11
Q

_______________ glucose transporters are found in the pancreas and liver, while _______________ glucose transporters are found in the muscle and adipose tissue

A

GLUT2; GLUT4

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12
Q

Which glucose transporter is controlled by insulin?

A

GLUT4

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13
Q

GLUT4 allows muscle, adipose and ___________ to increase glucose entry when glucose is ___________

A

Heart; abundant

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14
Q

Insulin regulates level of GLUT4 receptor at the ___________ ____________

A

Cell surface

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15
Q

The level of GLUT4 on the cell membrane is directly _________________ to the amount of glucose that can enter the muscle or fat cell

A

Proportional

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16
Q

What happens after insulin is gone?

A

GLUT4 is recycled back to GLUT4 storage vesicles (GSVs) to prevent the blood glucose from getting too low

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17
Q

How is insulin receptor activity controlled?

A

Ligand-mediated receptor internalization

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17
Q

Insulin action can be rapidly ________________ by internalization and degradation of the insulin receptor

A

Inactivated

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18
Q

Which of the following allow the decrease of hormone action in the cell?
i. Activation of Ras/MAP kinase pathway to mitogenic endpoints
ii. Sustain ligand-induced Akt phosphorylation
iii. Ligand secretion
iv. R complexes recruited to gene loci to induce or repress transcription

A

i, ii, iv

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19
Q

Decreased insulin receptor levels at the cell surface contribute to insulin ______________ in diabetes

A

Resistance

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20
Q

Long-term insulin exposure may lead to receptor _______________ instead of recycling

A

Degradation

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21
Q

Internalization of receptors is slow in patients with __________________

A

Diabetes

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22
Q

Lipid droplets store fat in the form of _________________ esters or __________________, fatty acids bound to a glycerol backbone

A

Cholesterol; acyl-glycerols

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23
Q

Lipid synthesis and storage is stimulated by ____________

A

Insulin

24
Q

Lipids provide a source of ______________ during times of ________________ demand

A

Energy; energy

25
Q

Lipid droplets have a ______________ phospholipid protein-containing __________-membrane

A

Single; hemi

26
Q

What organelles do lipid droplets interact with?

A

Mitochondria, ER, early and late endosomes, peroxisome

27
Q

Which protein in lipid droplets regulate their interactions with specific organelles?

A

Rab

28
Q

Which protein is responsible for lipid droplet motility?

A

Caveolin

29
Q

What is the most accepted theory of lipid droplets?

A

They are formed following the accumulation of neutral lipid between the leaflets of the phospholipid bilayers in the ER

30
Q

Which protein breaks down lipid droplets when fuel is needed and allows their movement to different locations?

A

Lipase

31
Q

True or false: Intracellular trafficking machinery is involved with lipid droplets

A

True

32
Q

Why do lipid droplets form interactions with mitochondria, ER and peroxisome?

A

Exchange of proteins and lipids for fuel

33
Q

Which of the following are reasons for trafficking of lipid droplets?
i. Fusion/fission of lipid droplets
ii. Storage space for proteins from other organelles
iii. Sites for protein translation
iv. Source of lipid building blocks or fuel for organelles

A

i, iii, iv

34
Q

What might cause an increase in the size of lipid droplets?

A

Metabolic disease and viral infection

35
Q

How do lipid droplets allow for the infection of other cells by viral proteins in HCV?

A

Viruses hijack cell surface receptors for lipoproteins
Lipid droplets are scaffolds for viral assembly
Liver cells secrete lipoproteins
Lipoproteins contain HCV viral proteins

36
Q

Exosomes are generated from _____________

A

MVBs

37
Q

Exosomes travel through the _________ to other tissues

A

Blood

38
Q

Which of the following is not cargo for exosomes?
i. Cytosolic proteins
ii. Hormones
iii. miRNAs
iv. DNA

A

i, iii

39
Q

Which cargo allow distant cells to influence gene transcription in other cell types?

A

IncRNA and miRNA

40
Q

How do cardiomyocytes regulate the glycolytic flux in endothelium when glucose is low?

A

Cardiomyocytes secrete exosomes containing GLUTs and enzymes that metabolize glucose
Exosomes are taken up by endothelial cells, which promotes the uptake of glucose from the blood and metabolism of glucose to pyruvate

41
Q

Which risk factors increase or decrease release of exosomes from tissues?

A

High nutrients and physical activity

42
Q

Which risk factor influences the cargo released from the muscle cells?

A

Diet

43
Q

Which signals have a big influence on what is packaged into exosomes?

A

Inflammatory signals

44
Q

What is the function of nanotubes and nanotubules?

A

Transferring metabolism from one cell to another (ex: mitochondrial therapy)

45
Q

How do mitochondria interact with each other?

A

Mitochondrial nanotunnels

46
Q

What are the uses of mitochondrial nanotunnels?

A

Exchange of mitochondrial content and aid in communication when mitochondrial movement is limited

47
Q

MAMs (mitochondria-associated (ER) membranes) are membranes that are in direct contact with ________________

A

Mitochondria

48
Q

Which of the following are characteristics of MAMs?
i. Have a unique lipid profile at connection point
ii. Have a lower concentration of lipid than ER or mitochondrial membrane
iii. Have a protein profile facilitating unique signaling, lipid synthesis, protein folding and tethering

A

i and iii

49
Q

How is MAM isolated from other membranes?

A

Spinning in sucrose density gradient
MAMs separate and mass can be extracted

50
Q

MAMs are enriched with _______________ and ______________

A

Cholesterol; ceramides

51
Q

What are the consequences of lipid depletion in MAMs?

A

MAM-associated proteins redistribute to the bulk ER
Reorganization of the mitochondrial network and dissociation of MAMs

52
Q

Which of the following proteins do MAMs share with either ER or mitochondria?
i. IP3R
ii. VDAC
iii. Calretuculin

A

i. ER
ii. Mitochondria
iii. ER

53
Q

What are the unique proteins of MAMs?

A

FACL-4, Mnf2

54
Q

What are some roles of MAMs in metabolism?

A

Reservoir for specific lipid species
Sites of lipid metabolism, phospholipid synthesis and transport
Platform for enzymes involved in controlling metabolism and cell growth
Mediate autophagy
Permit Ca++ flow into mitochondria

55
Q

True or false: MAMs are dynamic and can move in response to cell signaling

A

True

56
Q

Receptors for _____________-induced signaling molecules are colocalized at the MAM interface

A

Ca++

57
Q

Associate the following metabolic signals to the correct area:
i. Local concentrations of Ca++ at mitochondria and ATP production
ii. Mitochondrial dysfunction, disturbances in lipid synthesis/catabolism and Ca++ signaling
iii. Mitochondria and rise and fall of Ca++ concentrations for ATP production
iv. Muscle contraction requires tight Ca++ signaling

A

i. Insulin secretion
ii. Liver
iii. Heart contraction
iv. Skeletal muscle

58
Q

How do MAMs regulate fasting and fed states?

A

Fasting: Stimulation of MAMs formation and Ca++ exchange, mitochondria needed for energy
Fed: MAMs breakdown and less Ca++

ANAT 365 - Cellular Trafficking (5 decks)

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