Biologie cellulaire general

Question 1

Quelles sont les principales différences entre les cellules procaryotes et eucaryotes ?

Answer 1

Les cellules eucaryotes possèdent un noyau délimité par une membrane nucléaire, alors que les procaryotes n’ont pas de noyau véritable, leur ADN étant libre dans le cytoplasme. Les eucaryotes ont également des organites membraneux tels que les mitochondries, le réticulum endoplasmique et l’appareil de Golgi, tandis que les procaryotes ne possèdent pas ces structures. Les eucaryotes sont généralement plus grands et plus complexes que les procaryotes.

Question 2

Que sont les différentes parties de la cellules et leurs fonctions

Question 3

Qu’est-ce que l’autophagie et pourquoi est-elle importante ?

Answer 3

L’autophagie est un processus par lequel la cellule dégrade et recycle ses composants endommagés ou inutiles. Ce mécanisme est essentiel pour l’homéostasie cellulaire, la survie en conditions de stress et la défense contre les infections. L’autophagie joue également un rôle important dans les maladies neurodégénératives et les cancers.

Question 4

comment les métaux lourds peuvent-ils induire L’apoptose dans les cellules des poissons ?

Answer 4

L’apoptose est un mécanisme de mort cellulaire programmée, impliquant l’activation des caspases. Les métaux lourds peuvent activer la voie mitochondriale de l’apoptose en augmentant les niveaux de ROS et en perturbant le potentiel de la membrane mitochondriale, ce qui conduit à la libération de cytochrome c et à l’activation de la cascade apoptotique.

Question 5

omment les métaux lourds affectent-ils la fonction mitochondriale dans les cellules

Answer 5

Les métaux lourds peuvent perturber la chaîne de transport des électrons dans les mitochondries, entraînant une production excessive de ROS, une baisse de la production d’ATP et une rupture du potentiel de la membrane mitochondriale. Cela peut entraîner la mort cellulaire par apoptose ou nécrose.

Question 6

Quel est le rôle des lysosomes dans la gestion du stress causé par les métaux lourds

Answer 6

Les lysosomes participent à la dégradation des composants cellulaires endommagés par les métaux lourds. Cependant, une surcharge en métaux lourds peut entraîner une rupture des lysosomes, libérant des enzymes hydrolases dans le cytoplasme, ce qui peut provoquer une autophagie excessive ou une mort cellulaire.

Question 7

Qu’est ce que la reaction de Fenton

Answer 7

The Fenton reaction is defined as the oxidation of organic contaminants by hydrogen peroxide and Fe (II).

Fe2+ H2O2 = Fe3+ Ho. + Ho-

Question 8

Qu’est ce qu’un reducteur ?
Oxydant ?
Une oxydation ?
Une réduction

Answer 8

Un réducteur est une entité (atome, ion, molécule) qui perd des électrons.

Un oxydant est une entité (atome, ion, molécule) qui gagne des électrons.

Une réaction d’oxydation est une réaction au cours de laquelle des électrons sont perdus.

Une réaction de réduction est une réaction au cours de laquelle des électrons sont gagnés.

Question 9

quel organe à les changements histologiques les plus sévère et est plus sensible

Answer 9

Several studies reported that the histopathological changes in kidney are more severe than the gills and liver and is more susceptible to even minor toxic injury due to its large proportion of post-branchial blood supply to the renal tissu

Question 10

quand la mellationeine agumente, que cela signifie ?

Answer 10

Like liver, kidney also has metal binding protein such as metallothionein (MT) and the increased level of MT in kidney indicates the increased amount of heavy metal deposition

Question 11

Lorsque le niveau de ROS a dépassé celui des molécules antioxydantes et des éliminateurs de radicaux libres, quel système est en première ligne ?

Comment il fonctionne ?

Answer 11

SOD-CAT system provides the first line of defense against oxidative damage. The SOD has direct involvement in the removal of reactive oxygen species by converting super-oxide free radical to hydrogen peroxide and CAT works by breaking down hydrogen peroxide to water and free oxygen

Question 12

quel est l’effet des metqux lourds sur la production de SOD et CAT?

Answer 12

Ça dépend :
The expression differences could be due to different signaling pathways for detoxification of different heavy metals.

The mRNA of SOD and CAT genes has been down-regulated significantly in the brain tissue of Oreochromis niloticus a

Another study found that CAT transcript increased significantly in Javanese medaka (Oryzias javanicus) exposed to Cd, Cu, Zn and decreased by exposure to Cr and Ni (Woo et al., 2009).

Question 13

Que sont les rôles de la glutathione peroxidase ?

Comment elle varie selon les métaux

Answer 13

Glutathione peroxidase (GPx) has a direct role in body defense mechanism against the formation of hydrogen peroxide and GPx transcript expression has been influenced by the heavy metal exposur

Cd, Cu and Zn exposure in Javanese medaka fish has induced the GPx gene expression in liver tissue, whereas inhibited by Cr and Ni

Question 14

que fait la Glutathione reductase (GR) and Glutathione S-transferase (GST) ? comment elles varient ?

Answer 14

re also known to play an important role in detoxification and are used to determine the oxidative stress in the cells due to heavy metal exposure. The GR mRNA expression was found to significantly high in the gills and kidney of brown trout but not in the liver collected from a river contaminated with Cd, Cu and Zn (Hansen et al., 2006). On the other hand, significantly higher GST transcript has been expressed in the liver tissue of Japanese medaka fish exposed to five heavy metals such as Cd, Cu, Zn, Cr and Ni in a dose-dependent manner (Woo et al., 2009).

Question 15

Qu’est ce que la matallothioneine ? Elle s’exprime dans tous les tissus ?

Answer 15

Metallothioneins are low-molecular weight, heat-stable and cysteine-rich peptides which plays an important role in homeostasis of essential metals such as Cu and Zn, and detoxification of non-essential metals

The MT mRNA transcripts were found to express in almost all tissues with the highest expressions in liver may be due to its role as a major detoxifying organ

Question 16

Comment varie la mellathionein dans les tissus avec son exposition aux metaux lourds

Answer 16

Ça dépend
Two types of MT genes (MT-A and MT-B) have been identified in a number of teleost fish and MT-A has shown to have a significant role in Cd detoxification in fish than MT-B (Wu et al., 2018). For example, MT-A mRNA gene has been expressed in the liver with the dietary Fe supplementation and MT-B has not been affected. On the other hand, Fe exposure has suppressed the mRNA expression of both MT-A and MT-B genes in the kidney. Likewise, Cd exposure increased the up-regulation of MT-A gene in the intestine and liver whereas kidney was very sensitive to Cd exposure by expressing the MT-B gene (Vergani et al., 2007).

Question 17

cite un autre an important iron binding protein

Answer 17

ransferrin (Tf), an important iron binding protein synthesized from liver and transported to the blood. Cd is also known to bind Tf, which further reduce the binding capacity of Fe to Tf and has up-regulate the expression of Tf mRNA in the liver.

Question 18

Quelle est la différence entre free radicals ROS and non radical

Answer 18

radicals with an unpaired electron in their outer orbital

Question 19

Cite des ROS free radical

Answer 19

Oxygen-derived free radicals include the superoxide anion (O2radical dot−), the hydroxyl radical (OHradical dot), and the peroxyl (ROOradical dot) and alkoxyl radicals (ROradical dot) (R = lipid or protein)

Question 20

Cite des non radical ROS

Answer 20

n-radical ROS molecules include hydrogen peroxide (H2O2), hypochlorous acid (HOCl), singlet molecular oxygen (1O2), and organic hydroperoxides (ROOH)

Question 21

Pourquoi les ROS sont dangereux ? est ce qu’il le sont tous de la mpeme manière

Answer 21

ROS are highly reactive and indiscriminate in their reactions with different biological targets such as proteins, lipids, membranes, and nucleic acids. However, the chemical reactivity of each individual ROS is very different and spans up to 11 orders of magnitude for second-order rate constant

Question 22

Comment le ROS sont naturellement fabriqués dans le corps .

Answer 22

They are produced through normal cellular metabolism in mitochondria, the cytosol, plasma membrane, endoplasmic reticulum, nucleus, and other organelles

Question 23

que sont les principales sources de superoxide ?

Answer 23

Two main endogenous sources of superoxide are from leaks in the mitochondrial electron transport chain at Complexes I, II and III, and by NADPH oxidases (NOX) at the plasma membrane (

Question 24

Que se passe t-il avec les superoxide dans la mitchondrie ?

Answer 24

In mitochondria, superoxide is converted to hydrogen peroxide (H2O2), spontaneously and by the action of the superoxide dismutase (SOD) isoenzyme manganese SOD (MnSOD)

Question 25

Que se passe t-il avec les superoxide dans le cytosol ?

Answer 25

Superoxide that is produced in the cytosol is converted to H2O2 by the copper-zinc isoenzyme CuZnSOD

Question 26

Par qui sont paroduit les intracellular h2o2 ?

Answer 26

Intracellular H2O2 is produced mainly in mitochondria, the cytosol and at the plasma membrane

Question 27

comment s’appelle The role of ROS in normal processes at physiological levels

Answer 27

The role of ROS in normal processes at physiological levels is known as “oxidative eustress”

Question 28

Une fois produit dans les mitochondrie, que se passe-il avec les H2o2

Answer 28

Once produced in mitochondria, it is likely that H2O2 can cross cell membranes into the cytosolic compartment, by diffusion and through aquaporin channels

Question 29

Quel est le role de H2o2 normalement ? en condition ok

Answer 29

At physiological levels, ROS can activate multiple signaling pathways

T-hese include the three mitogen-activated protein kinases (MAPK): c-jun N-terminal (JNK), p38, and extracellular signal-related (ERK) kinases

• , apoptosis signaling kinase 1 (ASK1)
• protein kinase B (AKT), and phosphoinositide 3-kinase (PI3K) (

Moreover, ROS activate transcription factors such as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) (Song et al., 2017), nuclear factor-erythroid factor 2-related factor 2 (Nrf2) (Glory & Averill-Bates, 2016), activator protein 1 (AP-1), hypoxia-inducible factor 1α (HIF-1α), Forkhead Box class O (FoxO) (Priya Dharshini et al., 2020), and the p53 tumor suppressor (Pallepati & Averill-Bates, 2010).

Question 30

Au niveau physiologil (oxidative eustress), quel est l’effet de H2o2 ?

Answer 30

At physiological levels, H2O2 is essential for many cellular processes. These include proliferation, cell cycle progression, migration and adhesion, adaptive stress responses, activation of transcription factors, redox regulation by oxidation and reduction, immune function, energy sensing and bioenergetics, wound healing, differentiation, embryonic development, and angiogenesis

H2O2 is now considered to be a second messenger and an important cellular signaling molecule It can regulate cellular metabolism in response to changes in the local cellular environment, such as nutritional status, lifestyle, and irradiation

Question 31

Au niveau physiologil (oxidative disstress), quel est l’effet de H2o2 ?

Answer 31

However, at higher doses above about 100 nM, H2O2 is toxic and causes non-specific damage to biological molecules such as lipids, proteins, membranes, and nucleic acids

H2O2 causes cell death by apoptosis, and at higher doses, by necrosis

Question 32

Est ce que les dommages sont reversibles ou non ?

Answer 32

voir article branchie

Question 32

Quel est la définition de stress oxidatif

Answer 32

The definition of oxidative stress (distress) is “a serious imbalance between the generation of ROS and antioxidant defenses in favor of ROS, causing excessive oxidative damage to biomolecules

Question 33

Quel est la définition d’antioxidant ?

Answer 33

Antioxidants are defined as “any substance that delays, prevents or removes oxidative damage to a target molecule”
They protect different molecular targets such as proteins, lipids, nucleic acids, and membranes from oxidative damage.

Question 34

Que sont les enzymes avec les plus importante sinteraction avec H2o2

Answer 34

The enzymes with the highest rates of reaction with H2O2 are GPxs and Prxs, followed by catalas

Question 35

Sod convert “” to “” ?
Que se passe-til après

Answer 35

SOD isoenzymes catalytically convert superoxide anion to H2O2

Antioxidant enzymes such as catalase, Prxs and glutathione/glutathione peroxidases (GPx) convert H2O2 to non-toxic products

Question 36

Qu’est ce que le redox equilibrum ?

Answer 36

The redox equilibrium ensures that physiological, non-toxic levels of ROS are present in cells. If the production of ROS exceeds the capacity of the antioxidant defenses, the redox balance is perturbed, giving rise to oxidative distress