Biochemistry Exams!

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

Well seeing as how I'm finding it all to easy to ignore the textbooks and browse Retro Renault instead I figured I may as well use it to help me revise for my 6 upcoming exams for my Biochemistry degree!

This is my last year, and these are my finals, so if I don't give it my all in these exams then the last 3 years of my life, Â£11,400 in Student Loan and Â£3425 in Tuition Fees will have gone down the proverbial drains!

I have 6 exams, entitled as follows:

BL3692: Microbial Biotechnology
The commercial exploitation of micro-organisms, such as the use of filamentous fungi in the production of Quorn mycoprotein as an alternative to meat.
Examined on: 25th May @ 9.45am for 2 hours

BL3322: Advanced Parasitology
The life cycles and pathogenesis of obligate intracellular parasites such as Leishmania, Filariaemic parasites, Plasmodium (Malaria) and Toxoplasma Gondii
Examined on: 26th May @ 9.45am for 2 hours

BL3591: Hormones and Behaviour in Animals
The physical and mental assignment of gender and gender-related behaviour.
Examined on: 26th May @ 2.00pm for 2 hours

BL3522: Genome Regulation
The developmental and temporal control of gene expression in eukaryotic organisms such as humans.
Examined on: 31st May @ 2pm for 2 hours

BL3902: Data Handling
A non-revisable exam in which a random biological scenario or experiment is detailed with a view to testing skills in analysis, mathematics and interpretation of raw data.
Examined on: 6th June @ 9.45am for 3 hours

BL3702: Post-Transcriptional Control of Gene Expression
How messenger RNA (the copy made from the original DNA template) is edited and processed prior to translation into a functional cellular protein.
Examined on: 8th June @ 9.45am for 2 hours

Next week is the heftiest period, when I will complete half of my exams in just 2 days, Wednesday and Thursday next week.

I've already revised most of the material for Advanced Parasitology, meaning there are just two more exams I need to revise in the next week or so. I'll revise the material and make post in this thread to see how much I remember.

What I'll do now is just read through the notes as opposed to re-writing everything like I have been doing and just use this thread to reel off what I've learnt, and see how much I've retained!

To most of you it'll probably be complete gibberish but I find the easiest way to learn and remember things is to try and teach it to somebody else so you never know, this strategy may well help me and you may learn something to impress your mates with in the pub!

Site Subscriber Joined: 01 Feb 2005 Posts: 728

Sounds Fun Confused

Is it OK that I don't understand the titles, let alone the subject matter?

Good Luck though Ben Smile

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

Cheers matey!

Like I said I find trying to teach others the best way of learning so hopefully some of the stuff you might be able to understand!

Gonna do a bit now, whilst watching 2F2F for about the millionth time (just finished watching the original TFATF!) Going for an all-nighter in the revision stakes, need to get my erratic sleep patterns back in order!

Then I reckon I'll trek over to me' parents to see about getting this V6 engine in the garage!

Site Subscriber Joined: 01 Feb 2005 Posts: 728

LOL well get that coffee pot out the cupboard buddy Smile

Don't be asleep when the courier gets there in the morning though!

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

I wont be asleep mate, I'll be hard-coring it tonight! Always got the Pro-Plus in the cupboard if needs be and yes there is always that big jar of Nescafe on the side in the kitchen!

Posted: Wed May 18, 2005 5:51 pm

BL3591: Hormones and Behaviour in Animals

Surely you could revise some of that with some of the people on here!

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

Chet and the welsh would be the place to sart withnthat eh mals!

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

I hate you Christopher

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

I know you do JB but i cant be without you! Crying or Very sad

my heart cries out for you...

lol speaking of which diud you read the joke I put up about it? Guy walks in with the sheep and points to his girlfriend saying this is th epig I sleep with. lol

Posted: Thu May 19, 2005 10:54 am

Chris H wrote:

Chet and the welsh would be the place to sart withnthat eh mals!

Sounds like a plan!

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

lol yes i did.....baby

Site Subscriber Joined: 28 Jan 2005 Posts: 3547

JB...will sleep with anything with a pulse...2,3,or 4 legs Laughing

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

Righty......this first bit to thrill you will be all about the production of that vegetarian delight known as Quorn!

The History of Quorn

The main ingredient in Quorn and all Quorn-based products is mycoprotein - this is basically the major component of the cell walls of fungi. The decision to look into the production of fungal-based food was because of a predicted shortage of protein-rich foods in the late 1950's.

Rank Hovis McDougall (RHM) was given permission to sell mycoprotein for human consumption. The first retail product was produced by a company known as Marlow Foods, a joint venture between RHM and ICI. Their collaboration was out of mutual gain, RHM had exclusive right to sell and ICI had a free fermenter to use in the production process.

It was originally sold as a protein-rich supplement to conventional foods, and the predicted food shortage never materialised. The marketing of the mycoprotein changed direction and it began to be marketed as a new healthy food in it's own right. Marlow decided to name the product "Quorn" and it lacked cholesterol and animal fats. In addition it was low in calories and saturated fats and was extremely high in fibre (due to the fungal cell walls).

In 1989 a survey of the UK population revealed that around 50% of the population was reducing it's consumption of red meats and nearly 20% of young people were vegetarian. These statistics were behind another marketing change for Quorn and it began being sold as a meat analogue.

The rest as they say, is history, and Quorn is now the main ingredient in burgers, sausages and is an ingredient in over 50 pre-prepared meals. It is also available in it's pre-processed form for people to use in the cooking of their own meals and dishes.

The mycoprotein is produced through continuous-flow fermentation. The fungi used to generate the product is known as Fusarium venenatum and the product has harvested from two identical 155 cubic-metre fermenters (used in rotation) since 1994.

Continuous-flow fermentation is used as higher productivity can be achieved, this is when compared with regular batch fermentation.

Up until 1994, Quorn was grown in a much smaller 40 cubic-metre fermenter originally built by ICI in Billingham, which had originally been used to grow an animal feed known as 'Pruteen'. This smaller fermenter was known as 'Quorn 1' and was essentially a large loop approximately 40m in height.

Quorn 1 was used as a glucose-stat that was capable of producing 1000 tonnes of Quorn each year. The building of the two aforementioned 155 cubic-metre fermenters (known as 'Quorn 2' and 'Quorn 3') allowed productivity to increase from 1000 tonnes/yr to 14,000 tonnes/yr.

Each of these larger fermenters weighs in excess of 250 tonnes and cost Â£37.5M to build.

Sales increased to around Â£74M per yr since the building of Quorn 2 and 3. Sales received a boost in the mid-90's thanks to the BSE scare, and there are plans in place by Marlow Foods to build a 3rd fermenter.

As of 1998, 89% of Quorn sales are in the UK with 5% in the Netherlands and 3% each in Belgium and Switzerland.

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

Growing F. venenatum

This picture is a simplified version of the Quorn 1 fermenter. Like I said the fungus is grown in continuous flow, i.e. the fermenter is run permanently with nutrients and other chemicals being supplied continually. In practice though the cycle is terminated after ~1000 hours as the fungi acquire mutations which can cause problems in the final protein product - more on this later.

Before the fermenter is switched on, the fermenter is innoculated with 5l of F. venenatum culture. In this 5l is approximately 50g of biomass. Fermenter is switched on after 4 days. This fermenter is an air-lift fermenter, which means that the culture is drawn up towards the top, where gaseous exchange occurs, and then it drops down the other side.

The conditions for optimal growth are very specific and the most common growth method is via Glucose-stat. This means that glucose is supplied to excess so it does not limit growth.

As fungi require oxygen for the utilisation and respiration of the glucose, a steady oxygen supply is required. In the picture the oxygen is introduced in the form air at the base of the 'riser'. The riser is the column in which the fungal culture is drawn up. Conversely, the other column is named the 'downcomer', as it is where the culture drops back down to the base of the fermenter.

A heat exchange unit at the bottom maintains temperature at a stable 30 degrees celsius. As proteins are consituted from amino acids (i.e contain an amino (R-NH3) and acidic (R-COOH) functional groups) ammonia is added. Acidic metabolites accumulate as a by-product of respiration. Ammonia influx is regulated by a pH sensor that maintains pH at 6.0.

A mycotoxin sensor also makes sure that any given run is not sabotaged. The method used can detect toxins sensitive to 2 parts per billion.

Gaseous exchange of oxygen and carbon dioxide is very important. The riser is always wider at the bottom in order to increase hydrostatic pressure. Increasing pressure also encourages transfer of oxygen from the gaseous phase (the air fed in) to the liquid phase (the culture) so this is why the air is fed in under compression.

Hydrostatic pressure at the top of the fermenter is lower, causing the release of respiratory carbon dioxide. A valve at the top of the fermenter allows the carbon dioxide to be bled off. The reduction in gaseous volume results in an increase in density of the gas remaining in the fermenter. On the way through the downcomer, a stream of pure O2 is added to complete the pressure cycle.

The hydrostatic pressure differential between the riser and the downcomer gives rise to a parameter known as 'specific gravity' and this basically ensures that culture broth flow through the fermenter is in one direction only.

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

Downstream Processing

A crucial process that must occur before the mycoprotein can be harvested is RNA reduction.

RNA is very similar to DNA, the differences being that RNA is single-stranded and highly amorphous where as DNA is double-stranded and assumes a highly ordered and regular structure. In addition the base units of DNA structure (nucleotides) are deoxygenated at a particular position within the molecule hence why DNA = "DeoxyriboNucleic Acid" and RNA is just "RiboNucleic Acid".

Anyway, if a food meant for human consumption contains excessive amounts of RNA, a metabolic byproduct of RNA digestion is uric acid. Accumulations of this uric acid give rise to such conditions as gout, which by account of my mother is not very nice to have.

For this reason, all foods for human consumption must have an RNA content of less than 2% w/w (weight/weight). This regulation was set by the World Health Organisation (WHO). The WHO also stipulates that RNA ingested from single cell sources should be no more than 2g RNA per day, with ingestion of no more than 4g per day from all RNA sources. Unprocessed F. venenatum has an RNA content of ~8% which limits intake of the product to around 20g per day.

Consequently, a process of heat treament is implemented. The temperature is raised to around 64 celsius for half an hour, which is optimal for the activation of RNAses, enzymes that degrade RNA. As RNAses are more heat resistant than proteases (enzymes that digest protein - what needs to be retained) loss of protein is kept to a minimum. This is because RNAses are working while proteases are denatured, this leaving the protein intact.

However there are some drawbacks. Some losses will occur, including upto 40% of the biomass in some cases. Nevertheless, the heat treatment is a necessary process that reduces the RNA content from 8% to ~ 1%, falling well within the 2% boundary specified by the WHO. Recently the temperature used has been increased from 64 to 68 celsius which reduces loss of biomass from 40% to 30%, increasing efficiency and productivity.

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

Processing, Storing and Harvesting

The reason fungi is used to harvest mycoprotein as opposed to bacteria or yeast is the fact that fungi grow filamentous appendages known as mycelia.

Rank Hovis McDougall (RHM) designed a way of aligning all the fungal mycelia to resemble the structure of meat at the microscopic scale. The way they do this is to heat it up and steam-roller it in order to get all the filaments aligned. A small amount of egg white is added (egg white is a protein binder) and the heating of the fibres causes them to set.

In addition, other natural ingredients can be added to give colouration and/or flavouring to the mycoprotein if it is to be used in the preparation of ready-made meals. The whole result of the alignment process is to create a product with the same chewiness and succulence of real meat.

The mycoprotein is harvested via simple centrifugation and it can be reduced in size for storage. It can be chilled and frozen as needed and quality control checks are in place to ensure the product is consistently of a high quality.

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

Mutant Fungi

I said earlier that this kind of fermentation process is known as continuous flow, designed to run indefinitely. I also said that in reality a fermentation run is terminated after ~1000 hours running.

The reason for this is the spontaneous appearance of mutant fungi strains that affect the composition of the harvested mycoprotein. While I explained the advantages of using fungi in the last post this is a particular disadvantage.

You see, while the conditions used in fermentation are used to encourage optimal growth of the fungus, an inadvertent side-effect is that mutations crop up quicker. In a 1000 hr run the first mutant strains appear after around 300 hours. This translates as being ~ 107 generations from the parent.

The mutations appear more readily in the fermenter environment since the conditions are very specific, in that they apply a lot of selective pressure on each fungal colony. In the continuous flow process, the fungal culture is continually removed and replaced with fresh as the fermentation process progresses. This means that if a particular mutation is to remain in the fermenter, it must acquire a mutation that confers a survival advantage to it.

Logical deduction and analysis have shown that mutations do not arise spontaneously within the fermenter - the mutant strains are present in the original innoculating culture broth. This was found by charting the linear growth rate of a mutant strain from the time it was first detected. Since the axes of such a graph is growth versus time, the line could be extrapolated back to the start time of 0 hrs which reveals beyond all doubt that the mutant strain was in the original culture.

Site Subscriber Joined: 13 Oct 2004 Posts: 4722

ok, excuse me for saying this,

but i really dont think i can contiune reading, my brain will die.

not one mention of a piston in it at all!

how ever..

is this all off the top of your head?

or you doing it from text books etc?

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

these 'mutations'... they interest me. What exactly do they mean? does the product become poisonous or make you grow a third arm or what?

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

lol chris keeps "modifying" my replies....they really werent as nice as that!

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

Neal 19 16v wrote:

these 'mutations'... they interest me. What exactly do they mean? does the product become poisonous or make you grow a third arm or what?

The mutations in the fungus lead to it being much more branched. If the fungus is branched, then it cannot be packed in closely together and it cannot be aligned as easily. This means that the eventual product is crumbly in texture and is a poor meat substitute.

Obviously this means that the mutations are undesirable and so technology has been implemented to make the production process more efficient.

The mutant strains only grow if their when the mutations confers a growth advantage to the fungus. Eventually they displace the parent fungus which is nice and linear.