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Cell Bio > Week 4 > Flashcards

Week 4 Flashcards

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Biology 101 flashcards
1
Q

What is hypoxia

A

Insufficient oxygen availability and there is a deficiency in the amount of oxygen delivered to cells or body tissues

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2
Q

How much oxygen does mitochondria use to make ATP

A

More than 95%

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3
Q

What does a decrease in O2 do

A

Effects energy production and disrupts cells ability to maintain proper functions

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4
Q

What is oxygen homeostasis

A

A balance between oxygen consumption and oxygen supply

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5
Q

What is hypoxia linked too

A

Cancer, Cardiovascular disease , Stroke and COVID-19

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6
Q

What pathway does hypoxia induce

A

An evolutionary conserved signalling pathway mediated by hypoxia inducible transcriptional factors (HIF)

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7
Q

What is the concentration of moleculaor oxygen in the atmosphere

A

21% which also coresponds to normal oxygen conditions normoxia

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8
Q

What is the concentration in alveoli and arterial bood

A

13%

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9
Q

What is concentration of oxygen in tissues

A

5%

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10
Q

Why is concnetration is tissues and cells so low

A

en route oxygen consumption

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11
Q

Are vivo cells exposed to a lower concentration of oxygen than atmospheric oxygen

A

YES

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12
Q

Why might vitro and vivo normoxia not be the same

A

Vitro in a controlled envinroment like a lab dish they used conditions that mimic normoxic where in vivo a living organism the oxygen levels can differ signficantly due to various factors so vitro studies may not be super accurate

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13
Q

What are cells in vitro usually exposed too

A

5% CO2 and 95% air

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14
Q

What is the oxygen concentration in these incubators

A

20%

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15
Q

What are cells in vitro exposed too

A

Hyperoxic conditions

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16
Q

What is hypoxia considered at

A

1-5% and require specific chambers

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17
Q

What are erythrocytes

A

Red blood cells that reansfer oxygen in our body

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18
Q

Where are RBC produced

A

In the bone marrow

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19
Q

What is erythropiesies controoled by

A

A hormone erythropoietin which is produced in the kidneys

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20
Q

What happens to people with anemia

A

It is a chronic kidney diesase which is a deficiency in red blood cells to carry adequated oxygen to bodys tissues

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21
Q

How can anemina be treated

A

EPO provided efficient thearpy

22
Q

What is the process of the EPO gene

A

Has a specific short sequence downstream gene HRE which binds a heterodimer called hypoxia-inducible factor HIF-1

23
Q

Under hypoxia conditions what are the cells switching from

A

Oxidative to glycolytic metabolism

24
Q

What do the glycolytic enzymes do

A

Convert glucose to pyruvate

25
Q

What is pyruvate converted too

A

aceytlye CoA for oxidation in Krebs cycle or lacate in glycolytic end

26
Q

What does hypoxia activate the expression of

A

LDHA and PDK1 which inhibits pyruvate dehydrogenase tipping the balance from oxidative to glycolytic metabolism

27
Q

What is angiogensis

A

The growth of newly formed blood vessels from pre-existing vasculature

28
Q

What is angiogenesis induced by

A

A growth factor called vasular endothelial growth factor which is upregualted by hupoxia

29
Q

How does cancer use angiogensis

A

Induces the formation of new blood vessels in tumors under hypoxic conditions for supplying more nutrients in supporting tumor growth

30
Q

Why is VEGF up-regualted in hypoxia

A

They have hypoxia response element sequence in their promoter regions for binding the transcription factor HIF-1 which is activated by hypoxia

31
Q

What is the transcription factor HLF-1 a heterodimer of

A

HIF-1 alpha and HIF-1B that assembles in the nucleus to make an active HIF-1

32
Q

What is the difference between HIF-1 alpha and HIF-1B

A

HIF-1a is a subunit of Ox labile cytoplasmic protein with a half life of under 5 min under normoxia to due to protesomal degradation where HIF-1B is a subunit of a stable nuclear protein

33
Q

What do both subuntis have

A

DNA binding domain (bHLH) and a dimerization domain

34
Q

What domains does HIF-1A have

A

Transactivation domain at C terminus split into TAD-N and TAD-C subdomains

35
Q

What amino acid residues are in HIF-1a

A

Two prolines in TAD-N and one asparagine in TAD-C they can be hydroxylated by two different types of HIF hydroxylases

36
Q

What are the two hydroxylases and what do they need

A

PHDs and FIH1 molecular oxygen as a substrate and hydroxylation occurs at normoxia conditons

37
Q

What happens to HIF-1A under normoxia

A

VHL binds to the hydroxylated proteins recurits a ubiquitin E3 ligase and protesomal degradation and hydroxylation of asparagine prevents binding of P300 which is reuqired for HIF-1 activation and so it is not available under normal hypoxia signaling pathway

38
Q

What happens to HIF-1A under hypoxia conditions

A

HIF-1A can’t be hydroxylated VHL can not bind which prevents protesomal degradation which it can now be moved to the nucleus to pair with HIF-1B dimerization is needed for DNA binding p300 now binds HIF-1 is now active which binds to HRE

39
Q

What genes are expressed when HIF-1 dimer binds

A

EPO PDK1 and VEGF

40
Q

What domains make sure of dimerization

A

bHLH and PAS

41
Q

What is VHL

A

A tumor supressor gene so in its abesnce or mutations it can lead to cancer

42
Q

What tumors form with VHL disease

A

Benging or maligant tumors in the eye kideny or other tissues

43
Q

What are the two characteristics of VHL disease

A

Angiogenic intensive blood vessel growth elevated production of VEGF and have high hematocrit the proprotion of red blood cells is high

44
Q

What is in the E3 ubiquitin protein ligase complex

A

Elongin c ELC elogin B ELB and Cullin 2 (CUL2) and RING-box protien 1 (RBX1)

45
Q

What happens in VHL disease

A

It is not target for VHL-protesomal degradation and accumulate in cells resulting activation of hypoxia-related genes cell proliferation and neovascularization of tumors

46
Q

What enzyme catalyzes protesomal degradation

A

PHD and needs oxygen but also c-substrate 2-oxoglutrate and FE(II)

47
Q

What happens if one of the componets are missing

A

Hydroxylation of prolines will be impaired and HIF-1a will be stabilized and avoid protesomal degradation

48
Q

So what can hypoxia signaling response be induced by

A

Low oxygen, iron chelation (replacment with transtion metals) or non metabolix analgouses of 2-oxoglutrate

49
Q

What are the two majors way to induce hypoxia

A

Grow cells in the presence of low oxygen or to use chemical inhibitors of HIF1a hydoxylation

50
Q

What are the methods of inducing hypoxia

A

Molecualr oxygen in 1-5% or the chemical approach uses inhibitory durgs colbalt cholride which will replace iron ions

51
Q

What should you see in a western blot under hypoxia stress

A

HIF-1A are suppose to increase

52
Q

How else can hypoxia be tested

A

Cells can be transfected with a reporter gene (luciferase) under the control of HRE which is supposed to activated by binding HIF-1

Cell Bio (8 decks)

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