Cloning and biotechnology

Question 1

what do organisms from when they divide asexually?

Answer 1

clones

Question 2

what happens in mitosis?

Answer 2

Two identical copies of the DNA are created in mitosis, each copy is then are separated into one of two genetically identical nuclei.

Question 3

define clones

Answer 3

Organisms or cells that are genetically identical

Question 4

what are some examples of organisms that are capable of asexual reproduction to form clones?

Answer 4

bacteria and plants

Question 5

what are some advantages of natural cloning?

Answer 5

• Reproduction can occur without needing another organism of the same species for sexual reproduction. This is more convenient as you can produce many offspring in a smaller time frame
• It allows an organism to take advantage of favourable environmental conditions; if the parents are suited to the environmental conditions, their offspring will be too

Question 6

what are some disadvantages of natural cloning?

Answer 6

• There is less genetic diversity in the population, with only mutations giving rise variation. Selection is not possible
• If environmental conditions alter, the entire population will be affected as they will be less able to adapt
• As cloning produces many offspring, this could lead to eventual overcrowding within the population

Question 7

what is meant by totipotent?

Answer 7

able to differentiate into any cell

Question 8

what is the benefit of many plant cells being totipotent?

Answer 8

• This allows adult plants to form natural clones through a process known as vegetative propagation.
• The plants reproduce through the vegetative parts of a plant (e.g. roots and leaves)rather than the reproductive structures (e.g. petals).

Question 9

define vegetative propagation

Answer 9

Asexual reproduction from the vegetative parts of a plant rather than through specialised sexual reproductive structures.

Question 10

what is the benefit of the vegetative parts of the plant which are over-wintering (perennating organs)?

Answer 10

they allow plants to survive through the winter

Question 11

what are the 2 types of over-wintering organs that are used for vegetative propagation?

Answer 11

• bulbs

- tubers

Question 12

describe the structure and function of bulbs

Answer 12

Bulbs consist of an underground stem fromwhich fleshy leaf bases sprout. This leaf base contains food reserves that allow the plant to survive adverse environmental conditions (e.g. winter). The bulb also contains apical buds, which develop into new shoots and eventually new plants during the growing season. The new individual plants that grow are natural clones of the old plant. Corms are similar to bulbs but are solid rather than fleshy. They are underground stems with scaly leaves and buds which also remain in the ground during winter.

Question 13

give some examples of bulbs

Answer 13

daffodils and onions

Question 14

describe the structure of tubers

Answer 14

Tubers consist of underground stems which become large, underground structures as they become swollen with stored food. Tubers also form buds that often can go on to form shoots, which can then develop into cloned plants.

Question 15

give some examples of tubers

Answer 15

potatoes and sweet potatoes

Question 16

what is meant by horizontal stems?

Answer 16

Some plants are able to develop stems that grow horizontally away from the parent plant and are able to form roots of their own.

Question 17

what are the 2 kinds of horizontal stems?

Answer 17

• Runners/stolons — when the horizontal stems run above the ground
• Rhizomes — when the horizontal stems go underground

Question 18

what is meant by ‘suckers’ and what do they do?

Answer 18

• When a new stem grows from the roots of a plant, they are called suckers.
• They can either grow near the base of the original stem or further away from it.

Question 19

what happens to the original stem of suckers?

Answer 19

The original horizontal stem often dies leaving the new stem as a separate individual

Question 20

explain how vegetative propagation happens in leaves

Answer 20

• vegetative propagation can also occur in leaves.
• Smaller plants grow along the leaf margin and eventually drop from the leaf on to the ground.
• These can then go on to form their own roots and grow, being a clone of the parent plant

Question 21

what are plant cutting used to do?

Answer 21

Cuttings exploit vegetative propagation in order to create clones of a plant. This technique can be used to produce large numbers of plants very quickly.

Question 22

describe the 2 step method used to clone plants using plant cuttings

Answer 22

=Cuttings are primarily made from stems.

1. The stem is cut between two leaf joints (nodes) and the cut end is replanted into the soil
2. Parts of tissues in the stem develop into new roots — this can be promoted by submerging the base of the cut stem in rooting hormone

Question 23

where in plants can cuttings be taken from?

Answer 23

• stem
• roots
• leaves

Question 24

if a cutting is taken from the roots, what happens?

Answer 24

If taken from the roots, the cut root is buried just below the soil surface and goes on to develop shoots and eventually new plants

Question 25

if a cutting is taken from the leaf, what happens?

Answer 25

If taken from a leaf, the cut leaf is placed on moist soil. It then develops new shoots and roots

Question 26

why were methods of artificial cloning developed when we have natural cloning methods?

Answer 26

• natural cloning can be very time-consuming and only a limited number of cuttings can be taken from one plant.
• Therefore, methods of artificial cloning have been developed so that hundreds of plants can be rapidly cloned.

Question 27

name some methods of artificial cloning

Answer 27

micropropagation and tissue culture

Question 28

define micropropagation

Answer 28

The process of growing large numbers of cloned plants from meristem tissue taken from a sample plant

Question 29

what are some factors that make micropropagation possibel?

Answer 29

• Micropropagation is possible because meristem plant cells are totipotent.
• Micropropagation also requires the use of plant tissue cultures.
• In these cultures, cells, tissues, and organs are grown from a small sample of cells or tissue.

Question 30

define tissue culture

Answer 30

The growth of tissues or cells in an artificial medium taken from tissues of a sample plant.

Question 31

what are the conditions of the medium that tissues are cultured on to allow maximal growth?

Answer 31

• It contains nutrients necessary for growth such as glucose and phosphates
• The medium also usually contains a mixture of plant hormones (e.g. auxin and cytokinin) essential for the promotion of cell differentiation
• The medium must also be sterile to prevent the growth of unwanted bacteria and/or fungi – meristem tissue is usually used as it is typically virus-free

Question 32

what is the 6 step method used to carry out micropropagation?

Answer 32

1–Small samples of plant meristem tissue, called explants, are dissected from the plant

2. The explants are sterilised using either bleach or ethanol to kill any unwanted microorganisms which often compete with plant cells, limiting their growth
3. The explants are then placed on a sterile culture medium which contains the necessary nutrients and plant hormones. This helps stimulate growth via mitosis and forms a mass of undifferentiated cells called a callus
4. The main callus that was formed is then divided into a large number of smaller clumps of cells. These are then moved to another culture medium that stimulates the development of roots
5. Once the roots have developed, the clump of cells is then transferred to a different culture medium that stimulates the development of shoots. This results in the formation of tiny plants (plantlets)
6. The plantlets are then potted in soil to grow into larger plants. These plants are all genetically identical clones of the original sample plant

Question 33

what are some advantages of using artificial cloning in agriculture and horticulture (6)?

Answer 33

• New plants can be grown quicker than growing plants from seeds,so it is more time efficient and produces more plants in the same time-frame
• Desirable traits can be retained more reliably than traits derived from sexual reproduction
• Allows for the development of plants that are naturally hard to grow from seeds such as orchids
• The method of micropropagation ensures that the developing plant is free from viruses so is more likely to grow
• Provides a means of increasing the numbers of rare or endangered plants
• The new plants’ phenotypes are uniform, making them easier to harvest and grow

Question 34

what are some disadvantages of using artificial cloning in agriculture and horticulture (3)?

Answer 34

• Artificial cloning produces a monoculture of genetically identical plants with no variation. This makes it more susceptible to diseases or pests as they will not be able to acclimatise to changes in environmental conditions
• Micropropagation is expensive and labour intensive
• Large numbers of plants can also be lost if the culture is contaminated with bacteria or fungi

Question 35

why is using natural cloning advantageous in animals?

Answer 35

as it can produce a large number of animals possessing the desirable trait.

Question 36

why cells are used for artificial cloning of plants?

Answer 36

-with plants, artificial cloning uses totipotent cells (able to differentiate into every cell type),therefore only early embryonic stem cells are used (the only type of cell in humans that is totipotent).

Question 37

what are 2 methods currently used to produce artificial clones?

Answer 37

• Embryo splitting

- Somatic cell nuclear transfer (SCNT)

Question 38

explain embryo splitting

Answer 38

• Artificial embryonic twinning normally splits the early embryos manually into two, forming two independent, genetically identical embryos.
• However, artificial embryo splitting splits the same early embryo into many embryos,all of which are genetically identical.
• This gives rise to clones which are genetically identical to one another, but not the parent

Question 39

define embryo twinning

Answer 39

The process of splitting an early embryo in half to create two genetically identical embryos

Question 40

describe the 5 step process in which artificial embryo splitting occurs

Answer 40

1-A female animal with desirable traits is treated with hormones resulting in the release of many eggs (ova)

2. The eggs are then either:

• Fertilised inside the female animal and once the early embryos are formed, they are flushed out
• Removed from the female animal and fertilised in the lab by in vitro fertilisation (IVF)

3. Whilst the embryonic cells are still totipotent, they are manually split to produce many smaller embryos (embryonic splitting)
4. The split embryos are then left to carry on dividing in vitro for a few days to ensure development proceeds correctly
5. If divided correctly, each embryo is then placed into the uterus of a surrogate mother. The embryos then develop into foetuses and are born normally. Ultimately many genetically identical cloned animals are produced

Question 41

which organisms are cloned using somatic cell nuclear transfer (SCNT)?

Answer 41

-adult animals

Question 42

what does SCNT stand for?

Answer 42

somatic cell nuclear transfer

Question 43

what were 3 things that were required to cone Dolly the sheep?

Answer 43

=This required three animals of the same species to achieve:
• A female egg donor
• A female surrogate mother
• The animal to be cloned

Question 44

define somatic cell nuclear transfer (SCNT)

Answer 44

Method of cloning that is achieved by transferring the nucleus from a somatic (body) cell of an adult animal into an egg cell.

Question 45

what is the 6 steps that artificial embryonic splitting occurs in?

Answer 45

1- The egg cell (ovum) is harvested from a female animal and the nucleus is removed in a process known as enucleation

2-. A somatic (body) cell from the adult animal to be cloned is then isolated

3. The somatic cell is then either:

• Enucleated (i.e. nucleus is removed), and transferred into the enucleated egg cell
• Joined together with the enucleated egg cell using electrofusion

4. Both procedures require an electric shock which stimulates the division of the reconstructed egg cell
5. The cell then undergoes many rounds of mitosis to form an embryo which is subsequently implanted into the uterus of a surrogate mother
6. The embryo develops into a foetus and a clone of the original animal is born

Question 46

what is the difference between embryo splitting and SCNT?

Answer 46

embryo splitting, the clones are genetically identical to one another and not the parent; whilst in SCNT the cloned animal is genetically identical to the parent.

Question 47

what is non- reproductive cloning?

Answer 47

Non-reproductive cloning is the production of cloned cells and tissues for use outside of reproduction.

Question 48

what are cloned cells used for + its benefit?

Answer 48

• for therapeutic reasons – specifically for the growth of replacement organs/tissues.
• This is advantageous,as the cells will be genetically identical to the patient’s own cells,and there will be no issue with rejection.

Question 49

what can cloned tissues/cells be used for?

Answer 49

• for medicinal drug testing
• cloned embryos can be used to determine the impact genes can have on development.
• They are also useful for scientific research looking into the action of genes that control development and differentiation

Question 50

what are some advantages associated with artificial cloning? (6)

Answer 50

• Splitting embryos allows for large numbers of animals to be produced from parents with desirable genes
• Clones as embryos can be frozen to ensure the desirable genes were passed on before allowing them to develop
• SCNT allows for genetically identical copies of high-value organisms such as GM animals to be developed
• SCNT can also be used to clone rare or endangered species to increase their numbers in a population
• Can test medicinal drugs on cloned cells/tissues, avoiding animal testing (which has ethical issues of its own)
• It can be used to form tissues and cells for repairing damage caused by disease or accidents. These tissues and cells are genetically identical to the patient so therefore are not rejected

Question 51

what are some disadvantages associated with artificial cloning? (4)

Answer 51

• Reduces genetic variation so the clones are more prone to diseases and pests
• SCNT brings up ethical issues regarding the use of multiple eggs in which only one successful clone is produced
• Many embryos formed from SCNT fail to develop normally,resulting in miscarriages or malformed offspring
• Clones that have been brought to term may have numerous health problems and often have shorter life spans, e.g. Dolly the sheep

Question 52

define biotechnology

Answer 52

Use of living organisms or parts of living organisms (e.g. enzymes) in industrial processes to produce food, drugs or other products.
+ other processes that mix tech and living organisms:
• Gene therapy
• Genetic modification of plants, animals and microorganisms
• Artificial cloning of plants and animals
• Selective breeding of crops and animals
• Synthetic biology

Question 53

what organisms are used in biotech?

Answer 53

microorganisms including: bacteria and fungi

Question 54

what are some areas that microorganisms are used in?

Answer 54

• Food — e.g. ethanol in the production of beer which uses yeast
• Pharmaceutical drugs — e.g. penicillin which uses the fungus penicillium
• Enzymes — e.g. lipase and protease in washing power which uses bacteria
• Green technology — e.g. biogas (methane and carbon dioxide) which uses decomposers

Question 55

what are some advantages of using microorganisms in biotechnology? (8)

Answer 55

• Microorganisms have a rapid growth rate which means large quantities of them can be produced in a smaller timeframe
• The nutrient requirements of microorganisms are simple, as they can use waste materials to grow, and so are relatively cheap to produce
• Production takes place at atmospheric pressure and low temperature which reduces costs and increases safety
• Microorganisms produce their own enzymes so expensive catalysts are not required, and they are also very diverse,so are capable of synthesising and degrading many products/reactants
• Microorganisms often secrete the products into the surrounding medium,so they are easier to isolate
• Microorganisms are one of the easiest organisms to genetically modify,so specific products can be made, and there are fewer ethical concerns related to this
• The production process is independent of the climate and therefore can take place in any part of the world
• Pure products are released into the surrounding medium from the microorganisms, making them easier to harvest and lowering downstream processing costs

Question 56

what are some foods that microorganisms are used to make?

Answer 56

• yogurt
• cheese
• bread
• alcoholic beverages

Question 57

describe the 3 step method for how microorganisms are used in baking bread using bacteria

Answer 57

1. Flour, water, salt and sugar are mixed with yeast and kneaded to produce dough (mixing)which is left to rest in a warm place for three hours (proving)
2. The yeast in the dough respires anaerobically to form carbon dioxide which causes the dough to rise (fermentation)
3. The dough is then cooked in a hot oven which causes the carbon dioxide bubbles to expand and the bread to rise further (cooking). The cooking process kills the yeast cells and evaporates the ethanol that was produced by the yeast during anaerobic respiration

Question 58

describe the 5 step method for how microorganisms are used to make yogurt using bacteria

Answer 58

1. Milk is pasteurised, which involves heating the milk to 95oC for 20 seconds to kill off any harmful bacteria
2. The milk is then homogenised which disperses the fat droplets evenly in the milk and is then mixed with bacteria which produce lactic acid from the lactose in the milk
3. The acidified milk is then mixed with rennet which contains the enzyme rennin (also known as chymosin). Rennin causes the milk protein casein to curdle in the presence of calcium ions (breaks down kappa-casein making the casein insoluble) which causes the milk to separate into solid curds and liquid whey
4. For most cheese, the curd is cut, stirred and cooked in the whey and then strained through a cheesecloth (for cottage cheese, the curd is separated from the whey)
5. The curd is then pressed into moulds and left to dry, mature and ripen. During this, the bacteria continue to grow and produce lactic acid,which changes the texture and taste of the cheese; e.g. the fungi Penicillium can be added to produce blue cheese

Question 59

describe the 4 step method for how microorganisms are used in brewing beer using yeast

Answer 59

1. Beer is made by using germinating barley seeds which produce enzymes that breakdown starch to maltose. The barley seeds are then killed by slow heat, but the activity of the enzymes is retained to produce malt
2. The malt is mixed with hot water to produce a liquid containing maltose (called wort) in a process known as mashing. Hops are added to provide a bitter flavour and the wort is sterilised, cooled, and then inoculated with yeast which ferments the wort by using maltose in anaerobic respiration
3. Anaerobic respiration results in increasing concentrations of ethanol and carbon dioxide,which eventually inhibits the yeast
4. The beer is then left to mature at a cold temperature for up to a month and then filtered, pasteurised and made ready for sale

Question 60

what are some advantages of using microorganisms in protein production? (5)

Answer 60

• SCP is a good source of protein because it has a very high protein content
• SCP does not contain any animal fat or cholesterol,so is a healthier protein option than protein from animals
• Waste products can be used to grow microorganisms, so the production of SCP can be combined with the removal of waste products
• The production of SCP by microorganisms is very fast compared to animal protein production and can be increased and decreased easily according to demand
• Producing protein from microorganisms results in there being no animal welfare issues and not as much land is required

Question 61

what are some disadvantages of using microorganisms in protein production? (5)

Answer 61

• The conditions that microorganisms grow in to produce the proteins are ideal for pathogens, so care needs to be taken to prevent infections
• People may not wish to eat fungal protein because it is grown on waste
• The SCP needs to be isolated and purified to ensure it is not contaminated by the microorganisms or the waste material it grew on, so it may be costly
• SCP tends to have a different texture and taste to traditional protein so people may dislike it
• The amino acid profile of SCP is quite different to that of animal protein (specifically being deficient in methionine), however, the microorganisms can be genetically modified to change the amino acid content of the protein

Question 62

what is bioremediation used for?

Answer 62

• In bioremediation microorganisms are used to clear toxic pollutants by converting them to less harmful substances.
• Bioremediation is most commonly used to clean polluted water and soil.
• In bioremediation, microorganisms use pollutant contaminants as a source of food and convert them to less harmful substances.

Question 63

what are the optimal conditions used to grow the microorganisms needed for bioremediation in polluted areas?

Answer 63

• Water availability
• Optimal pH
• Optimal temperature

Question 64

what is meant by in situ modification? + give examples

Answer 64

If the conditions are not favourable for microorganism growth, they can be modified on-site.

e.g.
oxygen may be pumped into the area so as to meet the suited conditions for microorganisms which respire aerobically.

Question 65

what is meant by ex situ modification? + give examples

Answer 65

If the conditions are not favourable for microorganism growth, they can be modified off-site.

e.g.
the soil can be dug up and treated elsewhere

Question 66

why is bioremediation advantageous? (3)

Answer 66

• It is a natural process;very little waste is produced (usually in the form of carbon dioxide and water) and therefore it is not harmful to the environment
• Does not require much equipment or labour to carry out
• The workers do not need to be exposed to the toxic material, so there is less risk of humans being harmed

Question 67

what is a disadvantage of bioremediation?

Answer 67

, there are some types of waste material that bioremediation cannot be used to clear,such as heavy metals (for example, cadmium) so this technique is somewhat limited in use

Question 68

explain how large scale drug production occurs using microorganisms

Answer 68

• Microorganisms are often used to produce drugs,such as penicillin.
• Commercial drug production takes place on a large-scale using fermenters, which allow for certain conditions to be carefully controlled so that a high yield is obtained.

Question 69

why does temperature need to be controlled during large scale drug production using microorganisms?

Answer 69

Temperature — high temperatures cause the denaturation of enzymes; low temperatures reduce the growth of the microorganisms

Question 70

why does pH need to be controlled during large scale drug production using microorganisms?

Answer 70

pH — if the pH is too acidic or too alkaline thiscan cause enzymes to denature

Question 71

why does oxygen availability need to be controlled during large scale drug production using microorganisms?

Answer 71

Oxygen availability — some microorganisms respire aerobically as aerobic respiration produces more energy than anaerobic,so stable levels of oxygen are required

Question 72

why does nutrient availability need to be controlled during large scale drug production using microorganisms?

Answer 72

Nutrient availability — microorganisms require nutrients to grow and synthesise the required product

Question 73

why does product concentration need to be controlled during large scale drug production using microorganisms?

Answer 73

Product concentration — if the product concentration becomes too high, the synthesis process can be inhibited

Question 74

what are the 2 types of culture that can be made?

Answer 74

continuous and batch

Question 75

what is meant by primary metabolites?

Answer 75

Products which are synthesised by actively growing microorganisms in normal conditions are called primary metabolites.

Question 76

describe continuous culture? what happens to primary metabolites?

Answer 76

• Primary metabolites are continually released by the microbes then removed from the fermenter.
• When the primary metabolites are being made, nutrients are regularly added to the fermenter; some cells are removed to prevent the population from becoming too dense.
• This allows for the microorganisms to continue growing at a specific growth rate.
• This type of culture is called continuous culture

Question 77

what is meant by secondary metabolites?

Answer 77

other products which are produced when the microorganisms are stressed

Question 78

how are secondary metabolites produced? and describe batch culture

Answer 78

• Secondary metabolites are produced when the microorganism population has reached a certain size and cannot increase any further.
• The microorganism population is allowed to ferment for a specific time,then the fermenter is emptied,and the secondary metabolite collected.
• batch culture is done in separate batches

Question 79

what is meant by asepsis?

Answer 79

Asepsis is the process of ensuring that sterile conditions are maintained.

Question 80

why do fermenters need to be sterilised?
+
what would happen if we did’t sterilise them?
+
how are fermenters sterilised?

Answer 80

• Fermenters need to be thoroughly sterilised to prevent the growth of unwanted microorganisms such as pathogens.
• The growth of unwanted microorganisms would not only reduce yield (as they compete with cultured microorganisms for nutrients and space) but may also produce toxins, killing the cultured microorganisms and destroying their products
• Fermenters are therefore sterilised regularly using superheated steam to avoid these issues.

Question 81

what are some drugs that can be synthesised through the use of microorganisms?

Answer 81

• penicillin

- insulin

Question 82

what fungus produces penicillin?

Answer 82

Penicillium chrysogenum

Question 83

is penicillin a primary of secondary metabolite and why?

Answer 83

• Penicillin,however, is only produced by the fungus when its population has reached a certain size and is under stress.
• This means that penicillin is a secondary metabolite,hence it is manufactured by batch culture

Question 84

give a 2 step method describing how penicillin is manufactured

Answer 84

1. The fermenter is run for up to eight days, and the culture is then removed to filter out the fungus cells from the solution containing the antibiotic (penicillin)
2. The antibiotic is precipitated from the solution by adding potassium, and the antibiotic is then mixed with inert substances and prepared as a tablet or in syrup form

Question 85

what is insulin used for?

Answer 85

to treat type 1 diabetes

Question 86

how was insulin obtained in the past?

Answer 86

from the pancreas of animals

Question 87

why do we no longer obtain insulin from the pancreas of animals and how do we now obtain insulin?

Answer 87

• this was not very effective as animal insulin is not identical to human insulin.
• Synthetic human insulin is now produced using genetically modified bacteria by continuous culture

Question 88

give a 2 step method describing how to produce insulin

Answer 88

1. The human gene for insulin is combined with a plasmid and then inserted into the bacteria E.coli
2. The E.coli goes on to synthesise large quantities of human insulin

Question 89

what is the benefit of producing human insulin using genetically modified bacteria over obtaining it from the pancreas of animals?

Answer 89

Human insulin can now be produced in vast quantities at a relatively low cost through manufacturing by continuous culture

Question 90

what is meant by a ‘closed culture’

Answer 90

In a batch culture, the microorganisms in a fermenter do not have any exchange of nutrients or gases with the external environment.

Question 91

what are the 4th distinct stages that population growth of the microorganism population will be divided into?

Answer 91

1. Lag phase
2. Log (exponential) phase
3. Stationary phase
4. Death (decline)phase

Question 92

explain the lag phase which is the 1st stage of the growth curve

Answer 92

• the population is very small.
• Growth of the population is also slow, due to the organisms adjusting to their new environment.
• They adjust by initiating cell growth, absorbing water, synthesising enzymes and activating specific genes

Question 93

explain the log phase which is the 2nd stage of the growth curve

Answer 93

• the growth of the population is most rapid.
• The organisms have adjusted to their environment.
• They have adequate nutrients and space to grow,hence their population doubles in size with each generation

Question 94

explain the stationary phase which is the 3rd stage of the growth curve

Answer 94

• the population does not grow and therefore stays the same size.
• The organisms tend to use up more nutrients and produce more waste products like carbon dioxide.
• This causes the rate of death to increase and become equal to the rate of reproduction:

Rate of reproduction = Rate of death

Question 95

explain the death phase which is the 4th and final stage of the growth curve

Answer 95

• the nutrients run out and the concentration of waste products becomes toxic to the organisms.
• This causes the death rate to exceed the reproduction rate until eventually all the organisms die:

Rate of reproduction < Rate of death

Question 96

draw the graph for the phases of the growth curve

Answer 96

insert picture or double check from the snap revise notes- bacterial growth page 1

Question 97

is continuous culture a closed culture? + explain answer

Answer 97

in continuous culture the conditions are altered continuously to allow for optimal growth,therefore continuous culture is not a closed culture.

Question 98

what phase of the growth curve are primary metabolites produced?

Answer 98

Primary metabolites are produced during the log phase as they are made in continuous culture.

Question 99

what phase of the growth curve are secondary metabolites produced and why?

Answer 99

• Secondary metabolites are produced during the stationary phase when there are not enough nutrients for the whole population.
• This is because they are produced in stressful conditions and are therefore made in closed culture (batch culture).

Question 100

what is the equation for the number of organisms?

Answer 100

N= N0 * 2n
N= number of individuals present in population (no units)

N0= initial number of cells (no units)

n= number of cell divisions (no units)

Question 101

what are enzymes?

Answer 101

Enzymes are large proteins which act on a substrate and catalyse a reaction without being used up.

Question 102

where are enzymes extracted from?

Answer 102

Enzymes can be extracted from microorganisms for use in biotechnological processes.

Question 103

what must happen to enzymes before they can be used?

Answer 103

As enzymes remain in suspension after the reaction reaches completion they must be separated from the product before it can be used.

Question 104

why do we have immobilised enzymes?

Answer 104

• enzymes must be separated from the product before it can be used.
• This process can be very costly; to overcome this, enzymes can be held in place so that they cannot mix freely with the substrate or product.

Question 105

define immobilised enzymes

Answer 105

An enzyme that is not free to diffuse through a solution as it is held in place.

Question 106

what are the 4 main methods used to immobilise enzymes?

Answer 106

• Adsorption
• Covalent Bonding
• Entrapment
• Membrane Separation

Question 107

what is meant by adsorption?

Answer 107

Adsorption involves binding enzymes to a supporting surface (for example, clay and resin)using hydrophobic interactions and ionic linkages.

Question 108

what does it mean for the active site of the immobilised enzymes to be slightly distorted?

Answer 108

The active site of the enzyme may be slightly distorted due to the interactions the enzyme has with the supporting surface which can reduce enzyme activity; this means that less substrate is ultimately converted into product.

Question 109

what does it mean for the hydrophobic interactions and ionic linkages in immobilised enzymes to be weak?

Answer 109

The hydrophobic interactions and ionic linkages are all quite weak in adsorption, which means the enzymes can easily detach from the supporting surface and enter the solution.

Question 110

why is covalent bonding used as a method to immobilise enzymes?

Answer 110

Covalent bonds are used to bind enzymes to supporting surfaces through a crosslinking agent.

Question 111

describe the properties of covalent bonds and what they do in enzymes

Answer 111

-Covalent bonds are very strong,so enzymes do not easily detach from the supporting surface, however, the bonds distort the active site a great deal causing enzyme activity to be significantly reduced.

Question 112

what is meant by entrapment?

Answer 112

• Entrapment involves trapping enzymes in a matrix (e.g. network of cellulose fibres)that does not allow free movement.
• There is no distortion of the active site, hence the enzyme activity is unaffected.

Question 113

why can the entrapment method be used for reactions which have large substrates or products?

Answer 113

• in entrapment, the substrate and the products have to be small enough to move in and out of the pores in the matrix.
• This means that this method cannot be used for reactions which have large substrates or products

Question 114

what does membrane separation use?

Answer 114

Membrane separation uses a partially permeable membrane to separate the enzyme from the reaction mixture.

Question 115

what is a similarity between membrane separation and entrapment?

Answer 115

Similar to entrapment, the product and substrate have to be small enough to pass through the membrane,hence their diffusion through the membrane towards the enzyme can be slow, limiting the reaction rate.

Question 116

what are some advantages of immobilised enzymes? (3)

Answer 116

• The enzymes do not freely mix with the product meaning that the product extraction process costs are relatively low
• The enzymes can be easily reused which lowers cost in the long run
• When the enzymes are surrounded by an immobilised matrix, they are better protected from extreme conditions, so a higher temperature and more extreme pH can be used without denaturing the enzyme

Question 117

what are some disadvantages of immobilised enzymes? (2)

Answer 117

• Immobilised enzymes are usually less active than free enzymes,which makes the process slower
• In general, it costs more initially to set up immobilised enzymes than to set up free enzymes

Question 118

what are the 5 different things immobilised enzymes are used for?

Answer 118

• glycose isomerase
• lactase
• glucoamylase
• penicillin acylase
• aminoacylase

Question 119

what does the immobilised enzyme glucose isomerase do the production of high fructose corn syrup (HFCS)?

Answer 119

converts glucose to fructose

Question 120

what is HFCS made from?

Answer 120

HFCS is made from fructose, a sweeter sugar compared to sucrose.

Question 121

what is HFCS used in?

Answer 121

HCFS is used as a sweetener in diet foods because less sugar is needed to achieve the equivalent sweetness of sucrose.

Question 122

why do we used HFCS (its benefit)?

Answer 122

It is also cheaper than sucrose so is often used in soft drinks and processed foods

Question 123

how and why do we use the immobilised enzyme lactase?

Answer 123

• Some people are lactose intolerant, meaning they cannot digest the lactose sugar present in milk.
• To make lactose free milk, the lactase enzyme is immobilised and used to convert lactose in milk to glucose and galactose.
• Lactose-free milk provides lactose intolerant individuals with an important source of calcium.

Question 124

how is glucoamylase immobilised?

Answer 124

Glucoamylase is often immobilised in the large-scale conversion of dextrins to glucose.

Question 125

what are dextrins?

Answer 125

Dextrins are short polymers of glucose that are formed during the hydrolysis of starch.

Question 126

what is immobilised glucoamylase used for?

Answer 126

Immobilised glucoamylase is usually used to digest sources of starch such as corn and is also used to convert dextrin to glucose for use in the fermentation process; for example, in the production of alternative fuels for vehicles

Question 127

why is penicilin acylase used for? + why is it advantageous in use?

Answer 127

• Penicillin acylase is immobilised for use in the formation of semi-synthetic penicillins which provides a barrier against antibiotic resistance.
• This is because some penicillin-resistant microorganisms are not yet resistant to the semi-synthetic penicillin,so it is advantageous in use.

Question 128

what is aminoacylase and how is it made?

Answer 128

• Aminoacylase is a hydrolase used to synthesise pure samples of L-amino acids (a building block used in the production of certain pharmaceutical compounds).
• It is made by removing the acyl group from the nitrogen of a N-acyl amino acid.