Enzymes

An enzyme is a biological catalyst that increases the rate of reaction without actually taking part in the reaction itself. Like all catalysts, enzymes do not change the course of the reaction, but rather how quickly the reaction reaches its final state or equilibrium. Like all catalysts, enzymes are only required in very small amounts since they can be reused repeatedly.

Enzymes are globular proteins with (at least) tertiary structure and are of the order of 10 nanometres in diameter – enzymes are protein machines (with moving mechanical parts) on the nanotechnology scale!

Almost every important chemical reaction in the body is catalysed by an enzyme.

Q.1 Where in the body are enzymes found?

Q.2 Enzymes are said to be specific, but what is meant by ‘specificity’?.

Q.3 Enzymes (like all positive catalysts) work by reducing the activation energy of a reaction. What is the activation energy?

Q.4 What is the active site of an enzyme and what does it do?

Q.5 State the substrates of the following enzymes: lipase, trypsin, pepsin, sucrase and amylase. What are these substrates converted into?

Q.6 What is hydrolysis? Give an example of an enzyme-catalysed hydrolysis reaction.

Q.7 Describe the Lock-and-Key Hypothesis of enzyme function. (Draw or print out a diagram of the lock-and-key mechanism).

Q.8 Many enzymes require cofactors to work properly. What is a cofactor?

Q.9 There are three types of cofactor – prosthetic groups (tightly bound non-protein organic molecules), coenzymes and metal ion activators. What is a coenzyme? Give one example of an enzyme and its coenzyme.

Q.10 Enzymes can be controlled by other molecules called inhibitors which bind to the enzyme. What is meant by reversible and non-reversible inhibition? What is meant by competitive and non-competitive inhibition?

Q.11 The metabolism of a cell or organism is the sum of all chemical reactions occurring within it. How do enzymes control metabolism?

Q.12 Complete the graphs you have been given, to show the effects of 1) temperature; 2) pH; 3) enzyme concentration; and 4) substrate concentration, on the rate of reaction.

BTEC level 3, year 1: Unit 2 – Working in the Science Industry

You must know how procedures are followed and information passed on in the laboratory.

P1 Describe procedures and practices undertaken in a lab and how they can be communicated.

You need to produce a ‘technicians’ handbook’ – or at least a few pages that could belong to one and which explains commonplace items of laboratory equipment.

You need to write simple procedures for the safe use of each item of equipment, including how to clean, calibrate and service the equipment. You should write no more than one page per item of equipment.

1. The pH meter

Describe how to use a pH meter safely.What steps should you take to ensure accurate measurements? How do you calibrate a pH meter? What steps should you take to prevent damage to a pH meter?

2. The Bunsen burner

List the procedure for lighting a Bunsen burner safely.How do you reduce the risk of strike-back and what do you do if it occurs?What are the key things to look for to ensure a Bunsen burner is in good working condition?

3. Pipettes

What is a transfer pipette?What is a measuring pipette?What is a Pasteur pipette?What are Gilson pipettes?How do you calibrate a pipette?

4. Burettes

What is a burette used for?How would you clean a burette and why is this important?

5. The desiccator

What is a desiccator and what is it used for?How do you ensure that a desiccator works well – what two things does it need?

BTEC level 3, year 1: Unit 2 – Working in the Science Industry

You must know how procedures are followed and information passed on in the laboratory.

P1 Describe procedures and practices undertaken in a lab and how they can be communicated.

You need to produce a ‘technicians’ handbook’ – or at least a few pages that could belong to one and which explains commonplace items of laboratory equipment.

You need to write simple procedures for the safe use of each item of equipment, including how to clean, calibrate and service the equipment. You should write no more than one page per item of equipment.

1. The Centrifuge

Describe how to use a centrifuge safely.Why is it important to balance the centrifuge? What is the difference between g and rpm? What is an ultracentrifuge and what might you use it for?

2. The Colorimeter

What is a colorimeter and what is it used for (give an example)?List the procedure for using a colorimeter safely. How do you calibrate a colorimeter using a blank? What is a cuvette? What is monochromatic light?

3. Fume cupboardWhat is a fume cupboard used for? How would you use a fume cupboard safely? How does a fume cupboard differ from an extraction hood?

4. OvensOvens may be used for drying glassware and reagents (usually at about 110 oC).Find a picture of a laboratory drying oven. What safety precautions should one take when using a drying oven?

5. Electrophoresis

What is electrophoresis?Give an example of electrophoresis, e.g. as used in DNA fingerprinting?Write a safe procedure for gel electrophoresis.

More apparatus and protocols:

Gene Technologies

Introduction:

Gene technologies include a very wide variety of techniques that involve the manipulation of DNA. This includes genetic engineering, which is the modification of an organism’s genome,

e.g. by inserting the human insulin gene into yeast or bacteria which are subsequently cultured as a source of insulin to treat diabetics; or the insertion of healthy genes into the respiratory tract of cystic fibrosis patients (an example of gene therapy), or the development of genetically modified (GM) crops.

Gene technologies also include the use of DNA analysis in forensics, such as DNA profiling (DNA fingerprinting) and also includes the manipulation of an organism’s genetic material by selective breeding (whether by artificial insemination or natural fertilisation).

Grading Criteria:

P5 Describe the principles of gene technologies and how they affect individuals, society and the environment.

P6 Describe ethical dilemmas that may arise from gene technology.

M3 Explain how gene technologies affect health and well-being – mention both positive and negative affects.

D2 Analyse ethical dilemmas arising from gene technologies.

This assignment is BIG and so will be broken into several parts, but ALL parts must be completed to obtain a pass. It will be broken down as follows:

Part 1: DNA analysis – restriction endonucleases, PCR, gel electrophoresis and DNA fingerprinting and its use in forensics and paternity testing.

Part 2: Genetic engineering – making recombinant DNA, plasmids, gene therapy insulin and cystic fibrosis examples and selective breeding.

Useful links to help you:

http://www.ornl.gov/sci/techresources/Human_Genome/medicine/genetest.shtml

http://news.bbc.co.uk/1/hi/uk/7156051.stm

http://www.accessexcellence.org/RC/AB/BA/DNA_Fingerprinting_Basics.html

If in doubt – ask your tutor who, of course, knows everything (well a bit anyway)!

Part 1: DNA analysis, for example as used in forensics & paternity testing

1 What is a restriction endonuclease and how is it used in DNA analysis? Give an example of a restriction endonuclease and its recognition sequence. Draw and annotate a diagram to show the end result of restriction of a piece of DNA containing the recognition site.

2 What is gel electrophoresis and how is it used in DNA analysis? Briefly (in a few sentences only) describe the method of gel electrophoresis.

3 What is DNA (genetic) profiling aka DNA fingerprinting?

4 What is the aim of DNA profiling?

5 What is PCR, what does it do and how is it used to assist genetic fingerprinting?

6 Describe very briefly (in a few sentences only) one method of DNA profiling (such as STR analysis).

7 How is DNA profiling used in genetic screening for inheritable disorders, paternity testing, in forensics and in organ donor matching?

8 What ethical issues arise from the use of DNA fingerprinting, e.g. in paternity testing, forensics and genetic screening.

9 is for a merit (M3):

8 Explain the advantages and disadvantages of the use of DNA profiling, e.g. in (prenatal and neonatal) genetic screening and in organ donor matching. Focus on the pros and cons as far as the health and well-being (physical and mental) of people are concerned.

10 and 11 are for a distinction (D2):

10 Why is the use of DNA profiling, e.g. to screen for genetic disease and to solve crimes, controversial? See if you can find a specific example of controversy, perhaps involving a court case.

11 Some have proposed storing the DNA profiles of all newborn babies on a central database. What are the pros and cons of such a scheme? Should DNA profiling be used for National ID card schemes or for life insurance companies? Should everyone have their DNA placed on a central database?

Part 2a: Genetic Engineering:

1 Define genetic engineering.

2 What is a plasmid? What is recombinant DNA and how is it used in trasnformation? What is a recombinant plasmid and why is this especially useful? How can you detect whether or not a cell has taken up a recombinant plasmid (been transformed)?

3 Give one example of a useful chemical (e.g. a pharmaceutical) that is prepared using genetic engineering.

4 What is gene therapy? Give one example of a genetic disease (e.g. cystic fibrosis) that has been treated by gene therapy. How successful is this treatment?

5 What is genetic screening and how is it used in gene therapy? Give one example.

6 What is genetic counselling and how is it used in medicine? Give one example.

Part 2b: Other uses of DNA technology:

1 What is tissue matching (tissue typing or organ donor matching) as used prior to transplantation? Briefly describe one method of tissue typing (e.g. the mixed leukocyte reaction). Point 7 of part 1 will help here.

2 What is selective breeding? Briefly describe one procedure for selective breeding, listing the reproductive or gene technologies used. Give a specific example of the benefits of selective breeding. What, if any, are the problems and ethical issues that result from selective breeding?

D2: Analyse ethical dilemmas arising from gene technologies.

Research the ethical issues associated with gene technologies (such as DNA profiling). Section B, Part 1 Q.11 should help. If it helps then discuss what you find in pairs. We shall discuss this in class before you need to complete this section. This section requires an in-depth discussion of the ethical issues, like a short essay. You need to give both sides to each dilemma.

Some useful links:

http://news.bbc.co.uk/1/hi/uk/7156051.stm

http://news.bbc.co.uk/1/hi/health/4396833.stm

http://news.bbc.co.uk/1/hi/uk/7156051.stm

Part 2c: P6 - Describe ethical dilemmas that may arise from gene technology

Q.1 Describe the ethical dilemmas arising from the use of gene technologies, especially genetic engineering (e.g. genetically modified food crops and farm animals, cloning of animals, production of drugs like insulin) and the various uses of DNA fingerprinting (in forensics, paternity testing, tissue matching and genetic screening) and genetic counselling.

(In other words list what the dilemmas are and write a couple of sentences stating why each is a dilemma – a dilemma is an uncertain situation which remains unresolved, in other words there are moral arguments for and against the use of such technologies and it is not yet clear whether the pros outweigh the cons or vice versa). Points 8 to 11 of part 1 will help here.

Gene Technology assignment: earning a merit or distinction

The following are harder grading criteria which require you to draw together information about a variety of gene technologies (you have already answered parts of these questions in the earlier sections but you will need to elaborate and draw everything together).

M3 Explain how gene technologies affect health and well-being – mention both positive and negative affects.

Here you need to focus on the affects of gene technologies on human health and psychological well-being. For example, genetic screening and counselling have helped to reduce certain genetic diseases; tissue matching has saved lives by making organ transplants more viable. However, GM crops and DNA biometrics (as might be used on a national ID card scheme) are causing many people anxiety, whilst others argue that these technologies will benefit humanity.

By ‘explain’ it means list the pros and cons and then briefly say why they are pros and cons, e.g. tissue matching benefits human health because it enables a donor organ to be matched to its recipient which reduces the immune response of the recipient against the donor organ (if the donor recognises the new organ as foreign then their body’s immune system will attack it).