PUBLISHED PAPER #2
Panfoli, Isabella,Daniela Calzia, Silvia Ravera, Alessandro Morelli.2010. “Inhibition of Hemorragic Snake Venom Components: Old and New Approaches”. Accessed April 12, 2013. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3153198/
Snake venoms are mixtures of biologically active proteins, metal ions, peptides and organic compounds. There are over 600 species of venomous snakes which can be classified into several groups. Most of the world’s envenomation’s are due to crotalidae and viperidae venoms. Venoms which affect the cardio-vascular system are classified hemotoxic whereas those that affect the nervous system are classified as neurotoxic.
Hemotoxic venoms contain various enzymes, isoenzymes and non-enzymatic proteins that either activate or inhibit factors that affect hemostasis. Many of the toxins in the venom affect platelet function by inhibiting or inducing platelet aggregation. Phospholipase A2 (Pla2) isoenzymes are responsible for inflammation and can be found in large numbers in both hemotoxic and neurotoxic venoms. Hemorrhages are caused by enzymes degrading proteins and components of the hemostatic system. This can be lethal as the hemostatic system is responsible for stopping bleeding and wound healing, which is the opposite of hemorrhage.
The extract of protein from horses and sheep are used as antivenins as they neutralize the toxins in humans. The administration of these toxins may be risky. Neutralization of toxins using inhibitors in plant extract may be used. Inhibitors of PLA2’s form soluble complexes with PLA2 enzymes, inhibiting their effects. Electric currents can also be used as a neutralizer at low voltages against metalloproteases and PLA2. There are many approaches to inhibit hemorrhagic venom which present advantages as well as disadvantages.
Most people, if not aware of how, know that some snakes possess poisonous venoms which can be lethal. It is known that poison affects the body in a negative way, but I have never known how or why. From this paper I have learnt that venoms are composed of proteins which are responsible for attacks on specific system which, if not treated, will bring down the body from within. I also learnt that inhibitors play a positive role in preventing these damaging proteins and so are the major components in antivenins. This paper may be difficult for someone without a biochemistry, biology or chemistry background to follow. It is also too wordy.
PUBLISHED PAPER #1
Mattar ,Rejane , Daniel Ferraz de Campos Mazo, Flair Jose’ Carrilho.2012. “Lactose intolerance: diagnosis, genetics and clinical factors”. Accessed April 11, 2013. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3401057/
Lactose is a disaccharide that makes up the majority of mammalian milk and is also a major source of nutrition for new-borns until they are weaned. It is broken down by the enzyme lactase, which most people are born with, into glucose and galactose. Lactase activity is high at young ages such as birth to around two years old, but begins to decrease rapidly with age in some people(hypolactasia) grouped as “lactase non-persistence”. Those who maintain high lactase activity into adulthood are grouped as “lactase persistence”.
The LCT gene controls lactase persistence and non-persistence. The LCT13910CT and LCT13910TT genes are both found to be associated with lactase persistence, showing that the allele is still dominant in a heterozygous form, allowing the breakdown of lactose. However when the dominant LCT13910T is not present this results in lactose non-persistence, “lactose intolerance”. This may differ in different countries.
Lactose persistence and non-persistence can be tested by checking the body’s glucose and galactose level when lactose is ingested. Galactose metabolism is inhibited with ethanol to determine the glucose rise. A breathe test based on the fermentation of undigested lactose can be used as well as genetic testing.
The by-products of undigested lactose in the intestines, carbon dioxide, hydrogen, methane and short-chain fatty acids result in abdominal pains, flatulence and bloating. It also acidifies the colon which results in diarrhea. These symptoms may also be accompanied with others not related to the gut.
This paper was very in-depth about the topic. It is very easy to be lactose intolerant and not know it can be so complex. One may drink a glass or milk or some yogurt for breakfast and not fully understand why they have and urge to defecate (poop) or fluctuate. I would’ve never guessed that my body’s ability to ingest milk and tolerate it could be associated with my genetics. I would suggest this paper to anyone in need of answers to their milk-stomach related issues.
This wordle pretty much sums up the previous posts on amino acids.
- Tests for amino acids
- reacts to form a purple coloured imino derivative
- Most amino acids are colourless
- not all may give a purple colour
- Proline and hydroxyproline, secondary amino acids give a yellow colour due its cyclic structure which results in the reduction of flexibility of polypeptide regions. The ninhydrin reaction as this reagent requires free alpha amino group (-NH2) . Therefore the amino acids which have a free -NH2 (amino) group, are positive for the ninnydrin test but because proline only has -NH (imino) group it is negative.
- Tests for proteins
- the buiret reagent is light blue in colour as it containd copper(II) ions
- turns purple in the presence of proteins
- the purple colour is formed when the copper ions in the buiret reagent reacts with peptide bonds on the polypeptide chains to form a complex
Essential and Non-Essential Amino Acids
There are 20 amino acids required for adequate health. Some of these 20 amino acids are esseital amino acids as well a non-essential amino acids.
Essential Amino Acids – these are amino acids that cannot be synthesized by the body and have to be acquired through the diet.
Non- essential Amino Acids can be synthesized by the body.
- contain all 10 amino acids
- proteins are derived from animal sources
- Bears contain some complete proteins
- lack one or more of the essential amino acids
- most vegetable proteins are incomplete
- Beans are an exception to this generalization
All amino acids contain this functional group, but differ based on their R-group.
THESE ARE THE DIFFERENT AMINO ACID GROUPS
The smallest amino acid has H for its R-group. It is Glycine.
2 Cysteine molecules undergo oxidation to produce 1 cystine molecule. A disulphide bond is formed when hydrogen is loss.
ATP can be made in 3 ways :
- substrate level phosphorylation (animals- glycolysis)
- oxidative phosphorylation (animals- mitochondria and electron transport chain)
- photophosphorylation (plants)
First Phase Enzymes
- Phosphohexose isomerase
- Phospho-fructokinase-1 (PFK-1)
- Triose phosphate isomerase
Hexokinase and PFK-1 are both enzymes for the irreversible reactions of the first phase. Their reactions are energetically favorable due to a large negative change of free energy(ΔG)
Second Phase Enzymes
6. Glyceraldehye 3-phosphate dehydrogenase
7. Phosphoglycerate kinase
8. Phosphoglycerate mutase
10. Pyruvate kinase
The most energetically favorable reaction in glycolysis is reaction 10. between phosphoenolpyruvate to pyruvate using pyruvate kinase. The reaction is irreversible due to ΔG being very negative.
ΔG is close to zero when the reaction is reversible.
- First metabolic pathway to give any living organism energy
- used in every cell- universal
- organelles are not needed for the process to take place, can occur in both prokaryotes and eukaryotes
- occurs in the cytosol
- 10 enzymes in the glycolysis procees, divided into 2 phases, the energy investment phase and the energy generation phase
Glucose enters glycolysis to form 2 mols of pyruvate. When oxygen and is available the pyruvate continues into the TCA cycle. Both mitochondria and oxygen much be present for this passage to occur.
However, when no oxygen is available, the pyruvate either forms 2 mols of carbon dioxide and ethanol through fermentation or 2 mols of lactic acid(lactate) which is also through fermentation. Lactate regenerates NAD+ when pyruvate is converted. red blood cells, rich in oxygen but lacking mitochondria use fermentation.
Process of glycolysis
5 enzyme reactions consisting of 2 irreversible reactions and 3 reversible reactions make up the Energy Investment Phase.
5 enzyme reactions consisting of 1 irreversible reactions and 4 reversible reactions make up the Energy Generation Phase.
Net gain of this reaction: 2 ATP and 2 NADH
Factors affecting enzyme activity
- Substrate concentration
- Enzyme concentration
Velocity (V) – the number of substrate molecules converted to product per minute.
Initial Velocity (Vo) – rate of reaction measured as soon as the enzyme and substrate.
Max velocity is also known as Vmax
Km – reflects enzyme-substrate affinity. It is numerically equal to the substrate concentration at which the reaction velocity is equal to ½ Vmax.
- Small Km , high enzyme-substrate affinity due to a low [S] being needed
- High Km , low enzyme-substrate affinity due to a high [S] being needed
As substrate concentration[S] increases, so does the rate of enzyme-catalysed reactions until it reaches Vmax. This can be seen by the steady increase of the curve. The plateauing off of the curve at Vmax reflects saturation(X). This is due to all the active sites on the enzyme molecule being occupied with substrate. At this point the reaction cannot occur any faster and does not have any effect on the rate of the reaction, therefore the curve plateaus.
The substrate concentration, temperature, and pH are kept constant in order for the enzyme concentration to have full effect. As enzyme concentration increases, so does the rate of the enzyme-catalysed reactions. This is because more enzymes will be colliding with substrate molecules. However this would only be up to a certain concentration where the enzyme concentration would no longer be a limiting factor.
As temperature (heat energy) increases more moles of substrate will have enough activation energy, therefore the number of substrate moles that bind to the active site(s) to form product will increase substantially. This leads to a high rate of reaction as a result of high collision rate between substrate molecules and active sites due to a high kinetic energy. This is seen in the high increase of the curve. The curve then peaks towards optimal temperature(X) and then quickly decreases. At optimal temperature the bonds of the tertiary structured enzyme cannot take it anymore and become denatured. When denaturation occurs the hydrogen bonds, hydrophobic, electrostatic and van der waal interactions begin to break. This breaking is a co-operative process, therefore as one bond breaks, it makes it easier for the others to break. As a result of this the enzyme’s shape changes and can no longer bind to the substrate.
pH is the measure of hydrogen ions concentration in a solution. The higher the hydrogen ion concentration, the lower the pH, vice versa. Most enzymes function efficiently over a narrow pH range. A change in pH above or below this range reduces the rate of enzyme reaction considerably. Changes in pH lead to the breaking of the ionic bonds that hold the tertiary structure of the enzyme in place. The enzyme begins to lose its functional shape, particularly the shape of the active site, such that the substrate will no longer fit into it, the enzyme is said to be denatured. Also changes in pH affect the charges on the amino acids within the active site such that the enzyme will not be able to form an enzyme-substrate complex.
Enzymes are specific!
Intermediate interaction between enzymes and its substrates occurs through molecular recognition based on complementary structure. This specific site on enzymes where the substrate and enzyme bond is a cleft called the active site . At this site the complementary substrate bonds using hydrophobic, electrostatic and van der waals interactions as well as hydrogen bonding.
Types of specificity
Relative specificity – enzymes to substrates that contain similar structures and the same type of bonds
Absolute specificity – enzymes only catalyse one reaction
Group specificity – enzymes only bind to n=molecules that have a specific functional group
Linkage specificity – enzymes only bind to a particular kind of chemical bond, regardless of structure of molecule
Stereochemical specificity – enzymes bind to certain steric or optical isomers
Hypotheses of Enzyme-Substrate Interactions
- Fischer’s lock and key hypothesis (Emil Fischer 1894)
This theory states that the substrate (key) is perfectly complementary to the active site (lock). Only if the substrate fits perfectly would it be catalysed, showing that enzymes can only catalyse specific substrates.
- Kushland’s induced fit hypothesis
Although the both theories are recognized, the induced fit is the more accurate of the two.the induced fit hypotheses explains that the shape of the enzyme molecule changes to fit the shape of the substrate when they encounters , thereby enabling the substrate to bind more effectively.