GLYCOLYSIS!!!!!!!

Hello biochemistry freaks. Its been a while since I’ve posted anything, the reason being is that I had so much work to do in the past few weeks and little by little I did a little something everyday until I was ready to post something worth reading. This next topic is about Glycolysis so here I go enjoy! J

GLYCOLYSIS WAS THE FIRST METABOLIC PATHWAY TO BE UNRAVELLED BY G.Embden, O.Meyerhof and J,Parnas! Sigh…. some tedious men at work that figured out the 10 reactions.J
‘glyco’-glucose and ‘lysis’-split gives you a basic idea of what glycolysis is all about and is said to be dated as to when there was anaerobic environments still years ago in the atmosphere.

This series of reactions consists of two phases (energy investment phase/preparatory phase and energy payoff phase) and 10 enzymes with 5 in each phase. The reactions for each phase are as follows:

PREPARATORY PHASE:
Consists of 5 enzymes:
1.Hexokinase
2.Phosphohexose Isomerase
3.Phospho-fructose kinase 1
4.Aldose  and
5.Triose phosphate isomerase.

You must observe that 2 reactions ARE UNI DIRECTIONAL  (involving 1 AND 2) due to a large negative change of free energy(energergetically unfavourale). Also 2 ATP are lost in these r’xns. These two reactions are called the 1st priming and 2nd priming reactions respectively.The remaining reactions are reversible.

1st reaction/1st priming r’xn  :

A phosphate group (phosphorylation) is added to carbon 6 on glucose to form glucose 6 phosphate. This is catalyzed by Hexokinase (a type of transferase transferring terminal phosphate group from ATP to glucose). Hexo-6 kinase- taking the terminal phosphate group from ATP. IN THIS R’XN 1 ATP IS LOST!! THIS REACTION IS IRREVERSIBLE!! Reason: delta G value has a high negative value……..
*Note : Why convert to gl- 6 phosphate though?
Ans: by phosphorylating the glucose you trap it in the cell as there are no transporters in the cell membrane for this as it would have for glucose.
*Note : all kinases need mg2+ in active site….WHY??? ANS. It stabilizes the negative charge on ATP molecule. Also it stabilizes the conformation of the enzyme and it prevents the hydrolysis of the ATP  by keeping water out.

2nd reacton:

Phospho-hexose isomerase enzyme converts glucose6-phos. to fructose -6- phos. AN ALDOSE SUGAR IS CONVERTED TO A KETOSE SUGAR.  THIS IS A REVERSIBLE REACTION.

3rd reaction/ 2nd priming reaction:

Catalyzed by PFK1. This enzyme is the most regulated enzyme in glycolysis. ATP IS LOST HERE AGAIN as f-6-phos. is converted to fructose-1-6-bisphosphate. The phosphate groups are not attached to the same carbon atom thus bi- is used rather than di-.. THIS IS A IRREVERSIBLE REACTION!!

4th reaction:

Catalysed by Aldolase . In this reaction f-6-phos[hate is split into glyceraldehyde 3-phosphate (G3P) + dihydroxyacetone phosphate (DHAP). Two 3-carbon structures are formed. THIS IS A REVERSIBLE REACTION.

5TH REACTION:

DHAP is converted to G3P. This is catalyzed by triose phosphate isomerase. *note: it is said that this enzyme is a kinetically perfect enzyme meaning that as substrate bund too the enzyme a reaction happens. The reaction happens fast , its intermediate is very unstable.

THE PAYOFF PHASE:

The 5 enzymes involved are:

6.Glyceraldehyde 3-phosphate dehydrogenase
7.Phospho glycerate kinase
8.Phospho glycerate mutase
9.Enolase
10.Pyruvate kinase

6th reaction:

2 G-3-p converted to 2 molecules 1,3bsphosphateglycerate(1,3 BPG). This is a reversible reaction. 2 phosphate are used to energise the conversion and 2 molecules of NAD+-NADH formed. OXIDATION AND PHOSPHORYLATION OCCURS. Oxidation is nad –nadh where the g 3 p lost hydrogen so it is oxidized. Phsphorylation (atp is not used here but inorganic source), the oxidation reaction produces the energy need to add the phosphate group. THIS REACTION CONTAINS THE ONLY OXIDATION REACTION IN GLYCOLYSIS.

*note: glycolysis would not occur without NAD+. It needs to be converted to NADH.

7th reaction:

1,3 BPG converted to 2 molecules 3-phosphoglycerate.  1ST ATP FORMED HERE (2 are formed) !!. SUBSTRATE LEVEL PHOSPHORYLATION OCCURS HERE. Catalyzed by phosphoglycerate kinase. Phos. comes from the substrate 1,3 BPG leaving 3-ph glycerate.

*note: the 2 ATP  used in investment phase is paid back here.

8th reaction:

Catalysed by ph g’te mutase (enz 8 above). In this reaction the 3-phos.g’te is first converted to 2molecules of 2,3 bisphosphate glycerate. Then the phosphate on carbon 3 is removed finally forming 2-phos.glycerate.

9th reaction:

The product above is converted to 2 molecules Phosphoenolpyruvate (PEP).  WATER IS LOST, THIS IS A HYDROLYSIS REACTION. Catalyzed by enolase. This is an irreversible reaction beacause of delta G value being highly negative.

10th reaction: catalyzed by pyruvate kinase. 2 molecules PEP converted to 2 molecules pyruvate. Substrate level phos. this reaction is the most energeticslly favourable reaction in glycolysis. 2 ATP molecules made  THIS IS THE SECOND ATP FORMATION ad is profit ATP.

*note:PEP HAS A LOT OF ENERGY THAT CAN CREATE THEORETICALLY MAKE 2 MOL. ATP FROM EACH BUT ONLY FORMS 1 ATP EACH AS REST OF ENERGY IS LOST AS HEAT. This r’xn is a reason for sweating also when exercising.

*note p.kinase deficiency- erythrocytes cannot get energy from glycolysis. Ery… can only get energy from glycolysis, this condition is aka hemolytic anemia.

2ATP AND 2 NAD+ IS USED THEN 4 ATP AND 2 NADH GENERATED—————>
THEREFORE THERE IS A NET GAIN OF 2 ATP MOLECULES AND 2 MOLECULES NADH

The following picture illustrates the process of glycolysis in good detail:

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NOWWW WHAT ARE THE FATES OF THIS PYRUVATE????????????????

Under aerobic conditions the following reaction occur :

This is a unidirectional reaction as delta G is very negative aslo known as the link reaction as it links it to the TCA  cycle.
acetyl co-a

Under anaerobic conditions lactate or ethanol fermentation occurs. Fermentation is done for regenerating NAD+ for glycolysis to continue.

For  lactate fermentation :

This method is unidirectional an is used by erythrocytes or strenuous exercise(lactic acid formed…needs oxygen to break down L.acid……can cause cramps). ERYTHROCYTES HAS NO MITOCHONDRIA THEREFORE LACTATE FERMENTATION IS USED FOR ENERGY. NO ATP FORMED.THE CELL GETS 2 ATP MOLECULES FOR EACH GLUCOSE MOLECULES USED IN GLYCOLYSIS.
aerobic pyruvate

For ethanol fermentation:

NAD+ IS REGENERATED SO GLYCOLYSIS TO CONTINUE.

ethanol fermentation

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MULTIPLE CHOICE QUESTIONS

Which of the following pairs of statements explains the mode of action of enzymes?

  1. They lower the activation energy for the reaction.
  2. They are globular proteins and as a result are soluble.
  3. They break down substrate molecules into products.
  4. They bond to the substrate molecules at their active sites.
  1. 1 and 2only
  2. 2 and 3 only
  3. 3 and 4 only
  4. 1 and 4 only
  5. 2 and 4 only

Name the enzyme that phosphorylates glucose to glucose-6-phosphate.

  1. Phospho-fructokinase
  2. Kinase
  3. Hexokinase
  4. Phospho-glucase
  5. ligase

THE CELL VIDEO REVIEW

The cell was discovered by Robert Hooke. Cells generally come in different sizes but always adhere to a suitable surface area to volume ratio with which it can survive with. There is however a limit to where a cell can be for it to survive on its own which is the size of a dialister pneumosintes bacteria. Living cells are of two main categories :prokaryotes and eukaryotes. These two braod categories contain many distinctive traits of their own not found in the other but the main difference between the two is the presence of a nucleus (eukaryotes) or not (prokaryotes).
The information given in this video is very clear and concise. I was able to understand the information very easily as the narrator kept repeating certain key elements so that the information would remain fresh in my head and along with the visual representations of structures helped make the video much more understandable as I know where exactly functions are taking place in the cell not just the theory of it.

AMINO ACID AND PROTEIN VIDEO REVIEW

This video is mainly an introduction to amino acids and proteins. The general structure of an amino acid is a central carbon connected to a hydrogen, an amino group,a carboxyl group and a variable r- group. The variable r-group are of categories which include: Nonpolar (no charge) aliphatic R-groups, Polar ,uncharged R-groups, Aromatic R-groups, Positively charged r-groups and Negatively charged r-groups. Amino acids bond to each other via condensation reactions to form protein molecules.strong covalent bonds such as disulfide bonds may form between amino acids e.g 2 csyteine molecules to form a cystine molecule. Amino acids are tested for by way of ninhydrin test whereas the biuret test is used for protein testing. There are different types of protein structures : globular proteins, fibrous proteins and membranous poteins.
I would give this video a thumbs up because though concise, the information was clear cut and to the point so therefore everything needs to be adhered to and I had no probems with which this video was presented.

PUBLISH PAPER REVIEW 2- THE MYTH OF THE MARIJUANA….DOES IT REALLY ENHANCE YOUR MIND OR JUST EAT THE CRAP OUTOV EEEET :O

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Marijuana wreaks havoc on brain’s memory cells

Khamsi, Roxanne . “Newsscientist.com.” Last modified 20 November 2006. Accessed March 20, 2013.http://www.newscientist.com/article/dn10607-marijuana-wreaks-havoc-on-brains-memory-cells.html.

There are many myths out there about marijuana use and its effects on the body but in this study the only myth of interest is that of marijuana’s devastating effect on the brain’s memory cells.The main culprit behind this occurrence is due to a drug called THC.  One may ask “what is marijuana?”, well marijuana often called pot or weed is the dried components of the Cannabis sativa hemp plant. It is usually rolled into ‘joints’ or used via a bong.
A battery of tests were performed on labrats by  David Robbe at Rutgers University in New Jersey, US to produce the findings .Marijuana’s main active ingredient is called THC or tetrahydrocannabinoid. This drug  disrupts the normal working of nerve fibres in the brain’s memory centre, the hippocampus. Some probes were inserted into this area of the rats’ brains to monitor their nerve impulses and it was found that the marijuana reduced the synced firing of nerve impulses which reduced the output impulse voltage by as much as 50%. This change in the firing sequence happens because the THC binds to a receptor on the surface of the nerve cell, and so indirectly blocks the flow of current.
The rats were put to a test to monitor their brain performance where they had to figure out their way through a T-shaped maze to obtain  a treat and repeat this task correctly a few times. It was found that normal rats were able to run through  the maze correctly 90% of the time but those that were marijuana-laced were only able to obtain the treat 50% of the time they tried. The forgetful manner weared off a few hours after though but it is not certain if long term exposure may lead to longer forgetful periods. It has been noted though that chronic smokers have trouble remembering things.Robbe says that experiments have also shown that THC disrupts the signalling of
nerve cells in a Petri dish.

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I chose this topic because I have been hearing about so many reasons why people smoke marijuana and needed some form of  facts on my curiosity particularly on the topic concerning the brain because I am a studying student. I read similiar articles on this before and I think this article helped to reinforce my knowledge as well as add in some additional information that I didn’t know of.

PUBLISH PAPER REVIEW 1 :) :) :)- DID YOU SAY CURE FOR STRESS????? 1 UP SCIENTISTS :)

Brain protein might combat feelings of despair

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Khamsi, Roxanne . “Newscientist.com.” Last modified 18 July 2007. Accessed April 6, 2013.http://www.newscientist.com/article/dn12288-brain-protein-might-combat-feelings-of-despair.html.

There are so many things in this world that  scientists have come around to cure but feelings of stress is such a strange one. It is all thanks to a special protein called FosB that according to researcher Olivier Berton and colleagues can help the human brain handle stressful situations much easier.
Olivier Berton of the University of Texas Southwestern Medical Center in Dallas, Texas, and his colleagues exposed mice to a test involving mild but painful electric shocks from a wire mesh at the bottom of a cage. Data analysis showed that those mice that tried the hardest to escape had very high levels of delta- FosB . Next, mice were injected with a virus in their brain  that allowed them to make extra delta FosB protein as well as some were injected with the same virus but without the genetic code for the protein. This served as the control group. The mice remained fairly normal when left alone but when a shock was applied the mice became erratic. The cage was left locked and the process of shocking them for an hour each day was repeated for 3 days on which the third day, a small escape door was opened. As expected those mice with extra protein got through the door 85% of the time whilst the control mice only got through 60% of the time. Berton states that mice with more FosB coped better with the stressful situation and was able to figure out the best escape route when given the chance.
It is a bit unclear as to how exactly this protein works to aid the mice. Delta FosB is said to be a transcription factor which boosts the production of other molecules within cells but for this specific T.F,is boosts production of ‘substance P’. Substance P was shown in early experiments to change feelings of pain but in the experiments carried out by Berton, all the mice had the same reaction to pain so therefore this can be ruled out in this case. He further states that this molecule is known to increase feelings of anxiety in people. It is yet theoretical that inceasing levels of delta FosB increases ones ability to pull through daunting  tasks but with further research this theory can maybe become a reality to take advantage of.
As a student ,I often experience times of stress so therefore when I came across this topic, I was quite intrigued to find out about it. I think the information within this article shows some promising stuff for future use but still seems a bit uncertain where it mentions that this is but a theoretical study. I hope through further studies that eventually a product can be made to help alleviate stressful situations because I would surely be a buyer of this product.