Experiment 2.32 Energy Content of Food

Recall how to carry out a simple experiment to determine the energy content in a food sample

Equipments:

Thermometer

Boiling Tube (filled with 20cm^3 of water)

Crucible --> measured mass of food sample 

Record initial temperature of water in Celsius, for example, 20C.

The food source is ignited and there is a heat transfer from the food source to the water. When the food is completely combusted, we then record the final temperature of the water, for example 30C. 

1 cm^3 of water has a mass of 1 g. 

1 cm ^3 of water, to raise its temperature by one degree takes 4.2 J. 

Calculation:

(mass of water (g) x temperature rise (C ) x 4.2)

Energy released from food per gram = ------------------------------------------------

mass of food sample (g)

= [20 x (30-20) x 4.2] / 10

= 84J / g

Cloning

1. An egg cell was removed from the ovary of an adult sheep B The egg cell's nucleus is then removed. 
2. Nucleus from the organ cell, for example udder cell, of adult sheep A is the taken out and inserted into the empty egg cell. 
3. The fused cell has complete set of chromosome and began to develop normally (in the lab) using genetic information from the donated DNA. 
4. Before the dividing cells specialize, the embryo is implanted into the uterus of a surrogate mother sheep C. The offspring is genetically identical to sheep A. 

5.15 Genetically Modified Plants

Evaluate the potential for using genetically modified plants to improve food production (illustrated by plants with improved resistance to pests)

Maize is damaged by larvae of European cork borer --> 20% loss of crop yield.

This can be solved with that existence of Bacterium BT. In the chromosome of BT there is a gene, and when it is switched on it produces BT toxin which can kill cork borer larvae. 

We have to get the Bt toxin into maize to protect it from European cork borer.

1. Take restriction enzyme to the gene of Bt Bacterium and chop this gene out so that we will get the Bt gene for the toxin. 

2. Transfer it to the cell of the maize plant. The technique currently being used involved 'gene gon'. --> taking tiny particles of gold coated in Bt genes. They are then fired at high velocity at the plant cell, introducing the Bt gene to the interior of the plant cell. 

So the plant cell gets the gene and the maize cell have the Bt gene which make it toxin when switched on --> kill larvae. 

This gives the maize resistance to damage caused by the cork borer.

5.14 Humulin

Understand that large amounts of human insulin can be manufactured from genetically modified bacteria that are grown in a fermenter

The transgenic bacterial cell has been transformed from normal bacterial cell by the addition of recombinant DNA (plasmid + human gene for insulin).

A culture of bacteria will be ingested into the fermentor.

In this fermentor chamber we need to consider:

- Nutrient --> Used to manufacture insulin protein 

- Temperature --> Optimal temperature 

- pH

- Gases 

----> Increase in population, in which the bacteria will then switch on the gene for insulin and manufacture protein insulin. 

It will then be necessary to remove the product and carry out purification

Purification = Downstream processing 

Genetically engineered human insulin = Humulin

5.13 Recombinant DNA

Describe how plasmids and viruses can act as vectors, which take up pieces of DNA, then insert this recombinant DNA into other cells

Plasmids (circular structure) are found in bacteria cell, which are a right of bacteria DNA (as bacterias are prokaryotes and do not have proper nucleus). They are particularly small and don't carry many "information". 

Essentially, a virus has a protein shell called a capsid (pentagonal structure). Inside there will be a nucleic acid, possibly DNA or RNA. The virus has no other cellular components, such as cytoplasm or nucleus. 

A human chromosome (long threadlike structure) is made out of DNA.

Genes are section of chromosome.For instance, a gene is responsible for insulin, or hormone controlling blood sugar level. 

1. The restriction enzyme is selected that can cut the DNA of the section which made up the gene for insulin. 

2. Having cut the genes, we will take the plasmid of bacteria and cut it with exactly the same restriction enzyme. (Human enzyme that cuts out the human gene also cuts out the plasmid.) This will leave a broken ring structure. 

3. Introduce into the cut plasmid the human insulin gene. Both plasmid and human genes are composed of DNA. The human gene is then inserted into the plasmid. 

4. Complete the process by applying DNA Ligase enzyme to join the DNAs together. This combination of human genes + plasmid is known as recombinant DNA. 

Hosting Recombinant DNA 

(way in which recombinant DNA is transferred into other cells)

It is necessary to transfer the recombinant DNA into the host cell. In this instance we will use the virus. Inside the virus is the nucleic acid such as DNA or RNA. Around it is the protein.

1. Remove nucleic acid from the virus. We only want the capsid protein shell. 

2. The plasmid are taken up by the virus. The virus is going to act as a vector of the recombinant DNA, which will transfer it into the host cell.

The reason why we have chosen virus is that the virus is known as a phage, and it infect bacterial cells. The virus is able to attach to the cell member of the bacteria and insert the recombinant DNA into the host cell. 

At the end of this process we have a bacterial cell which now contains the recombinant DNA including the human gene for insulin. 

Notice that the bacteria still has its own normal DNA plus DNA from another organism. This organism is known as transgenic. 

5.12) Restriction and Ligase Enzymes

Describe the use of restriction enzymes to cut DNA at specific sites and ligame enzymes to join piece of DNA together. 

A restriction enzyme is able to cut DNA at particular location. Location is identified by the base sequence of DNA molecule. This is a very important tool in biotechnology and genetic engineer. 

A DNA Ligase is able to join the two DNA together. 

5.11 Breeding animals

Understand that animals with desired characteristics can be developed by selective breeding

Cow ---> Desired character = milk yield

Earliest farmers noticed that a few cows (A) would produce a small amount of milk each time, for example, 50 ml. A few other cows (B) would produce a 150 ml of milk. Most © would be producing a 100ml of milk.

The farmer will collect all the milk, but it would be cows C that he would choose to become his breeding cows. 

In the next generation of cows, we find that a few cows are producing 100 ml, a few with 200 ml (D) , and most with 150 ml of milk. 

The farmer then will select cows (D) as his breeding cows. 

Cows that produce high yield becomes the breeding population --> selected for the desired characteristic.

In the 3rd generation, it would be ranged with 150 --> 200 --> 250. 

As we progressively select, we change the desired characteristic. We are able to develop the desired characteristic by selective breeding. 

For this to work, recall that milk yield must be under the control of genes (genetic). 

5.10 Breeding Plants

Understand that plants with desired characteristics can be developed by selective breeding

The number of rice grain per rice is under the control of genes. The farmer wants to increase the number of rice grain per plant to increase the yield. 

Some plants have 6 grains per stem, while others have 8 and 10 grains per stem (variety in number). 

The farmer's decision is to harvest the grains with 6 and 8 grains, but will use those with 10 grains for planting. 

In the next generation of rice, the grains increase to 8-10-12. And so the farmer will harvest those with 8 and 10 grains, but selective those with 12 grains for planting and breeding.

In this way, the number of grains of rice which are found on  these plants gradually increases. This means increase in yield. 

This is an example of selective breeding.

It can be applied to most characteristics of the plant. 

5.9 Fish Farming

Explain the methods which are sued to farm large numbers of fish to provide a source of protein, including maintenance of water quality, control of intraspecific and interspecific predation, control of disease, removal of waste products, quality and frequency of feeding and the use of selective breeding 

Fish

- low fat and high protein

- efficient at turning their nutrients into fish mass

Advantage of fish farming

- allow us to control quality of water, ensuring that it's clean

- control predators

- reduce pests

- reduce disease

We contribute to the increase of yield of fish.

Disadvantage of fish farming

- When you have a high density of fish, the possibility is the transmission of disease. Because of this, some fish farmers have been using antibiotics, which is a concern to human health. 

- Abundance of fish also makes pest, so some farmers would use pesticides, which is also a cause of concern for human body.

5.8 Fermenter

Interpret and label a diagram of an industrial fermenter and explain the need to provide suitable conditions in the fermenter, including aseptic precautions, nutrients, optimum temperature and pH, oxygenation and agitation, for the growth of microorganisms

The industrial fermenter is the reaction vessel in which fermentation occurs. It is usually built out of metal such as copper or steel. Inside the steel jacket there is usually another steel jacket inside, and in between it contains water which made up the cooling jacket. Once the fermentation gets going it produces heat, and this cools down the reaction to keep temperature at optimum temperature. 

The fermenter will need to be cleaned and that's why we have a tubelike inlet which allows the steam to be pass into the fermenter. The steam will be sterilizing fermenter between fermentations (after finish producing the product and we need to clean the tank out). 

Within the fermenter there will be a heating plate to raise the temperature, which is called heater. 

Heater + Fermenter ---> Keep at optimum condition 

For fermentation to occur, we have to put nutrient into the tank, so there is a tap or pipework to insert nutrient as foods for microorganism.

To measure the internal temperature there is a temperature probe in the fermenter and it will tell us whether to apply the heater or the cooling jacket. 

The reaction will also require the addition of microorganism (so we have another tap for that). Reaction occurs inside the tank. 

We also require a pH probe as we are trying to keep the pH level at the optimum rate. 

We are also going to need a way to stir the reaction. This is going to be done by having a motor inside the fermenter and this will agitate the mixture, stopping it from clamming together and spreading the microorganism throughout the mixture.

At the end of reaction, we will need a way to drain off the product. This is called downstream processing which involves purification 

Overall, the fermenter is to keep the optimum growth conditions for the microorganisms so it is able to produce the product that we are looking for. 

5.7 Yoghurt

Understand the role of bacteria (Lactobacillus) in the production of yoghurt

1. Cow produces milk through the process of milk production. 

2. Milk goes through process called pasteurization to remove pathogens such as TB bacillus. This heat treatment kills off any pathogens in the milk. 

3. Milk sugars are converted into lactic acid. This is brought about by incubating the milk by 45-46 Celsius and add lactobacillus, which produces the enzyme that breaks down the milk sugar lactose to produce lactic acid.

4. Lactic acid results in lower pH, creating acidic condition. This causes milk proteins.

5. Milk proteins will solidify. This solidification of milk product produces what we called yoghurt. 

5.5 Beer Production

Understand the role of yeast in the production of beer

Beer-- composed largely ethanol, which is a kind of alcohol

Glucose --Yeast/Enzyme--> Ethanol + Carbon Dioxide 

This reaction is in the form of anaerobic respiration which is carried out by yeast, which is a kind of microorganism able to supply the enzyme, to bring about this convert ion.

Ethanol is often flavored by the addition of plants such as hops. 

Glucose comes from starch in a two step process: 

1. Starch -----> Maltose 

Enzyme: amylase

Source: Barley seeds, wheat seed, rice

Starch is broken down through amylase through the germination of the seed, which is the stage called malting. 

2. Maltose -----> Glucose

Enzyme: Maltase

5.4 Pesticide and Biological Control

5.4 Pesticides and Biological Control 

Understand the reasons for pest control and the advantages and disadvantages of using pesticides and biological control with drop plants

Where we have large field of crop all with the same type (monoculture), they tend to be very susceptible to pests, which use crop as their food sources.

This will reduce the productivity of farming ---> loss of food & financial impact 

To overcome this farmers can use…

1. Pesticides - chemicals designed to kill the pests

Advantages

- Chemicals = easy to obtain

- Easy to apply 

- Very effective

Disadvantages

- Toxic = killing other plants and animals other than the pests, and may be harmful to humans

- Bioaccumulation = pesticides buildup through the food chain causing problems for animals in the higher trophic level. Eg DDT

- Mutation in the pests often leads to resistance = pesticides have to be applied in higher concentration --> more toxic/ no longer work --> we have to find alternative pesticides 

2. Biological Control

For example..

In Australia, Cactus A of North America was introduced to gardens, and escaped into the country side and flourishes under Australian climate and ecosystem. The cactus then starts to cover a good deal of agricultural land and it was necessary to get rid of this. 

However, there were no natural predators of such cactus in Australia, so it was necessary to introduce alien species from another country, which was a moth/larvae, which feeds on the cactus (Cactoblastis). It has no competitors and was able to eat away this cactus and remove it from the agriculture land of Australia.

This control of pests by herbivore is called biological control. 

Advantages:

- No toxic/ chemicals involved

- Less impact on man and wildlife

Disadvantages: 

- Not 100% effective

- Difficult to control = always a danger that introduced species will find alternative prey on which to feed and will not actually die out once the pest has been removed

- Difficult to math a predator to the prey (to remove your pest)

5.3 Fertilisers

Understand the use of fertilizers to increase crop yield

We can increase the growth of plants in farming by the application of fertilizers to the soil. Fertilisers are usually in the form of nitrate and phosphate, or combination of both.

These compounds go down into the soil and are taken up from the root structure, and move in the transpiration stream up to the leave.

Nitrate --> proteins

Phosphate --> DNA, membrane structure 

Fertilisers can be divided into two groups. 

1. Organic fertilizers

Produced from animal waste on farm

This usually take the forms like Cow faeces, collected by the farmer

It often goes through the process of decomposition and fermentation and form a substance known as slurry. 

This gives crop plant a supply of nitrate and phosphate to promote growth. 

2. Artificial fertilizers 

Take the forms of chemicals 

- Potassium nitrate

- Ammonium nitrate

Apply to the field, they will go into solution in the soil water. This will release nitrate and promote growth in the same way as it would do at the compound. 

5.2 Crop Yield

Understand the effects on crop yield of increased carbon dioxide and increased temperature in glasshouses

Rate of photosynthesis:

CO2 + H2O ----light/enzyme---> C6H12O6 + 6O2

1. Increasing concentration of carbon dioxide

Carbon dioxide is the substrate. 

If we increase the concentration of substrate, the rate of reaction will increase and become constant at one point. 

This means we will have a higher yield up to a point when we reach the optimum carbon dioxide level. That point will give you the highest yield of product. 

2. Increasing temperature

The higher the temperature, the greater the kinetic energy. This means that particles collide into each other more frequently, resulting in higher chance for them to collide in correct orientation with greater temperature --> higher rate of reaction. 

However, a temperature which is too high can also do denature the enzyme and therefore slow down the rate of reaction. 

The peak of the graph is the optimum temperature. 

Increasing temperature also have other effect such as avoiding frost damage and providing constant temperature. 

If we increase the temperature and carbon dioxide, we will increase the rate of photosynthesis, and therefore yield. But they all have limit.

5.1 Glasshouses

Describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops 

Both polythene tunnel and greenhouse provide warmth for the growth of plant. 

The glasshouse (or greenhouse) is constructed on a framework of a simple house structure.

All surfaces are glass, allowing the light to penetrate through to the interior.

How it works

1. Solar radiation, which is initial source of energy, in the form of light

2. Light penetrates through the glass into the internal surfaces

3. Light is absorbed by surfaces inside the glasshouse, which can be soil, wooden surfaces, and plants themselves

4. These surfaces then reemit this energy as heat

5. The heat warms the air, raising its average kinetic energy = temperature increases

6. The warm air which is raising the temperature is trapped and create convection current within the glasshouse

This cause the increase of crop yield because…

How it works: Warm air in glasshouse ---> Increase in crop yield 

1. The higher temperature leads to closer, or optimum temperature, for enzyme reaction such as photosynthesis. (enzymes work most efficiently, allowing the fastest rate of reaction)

2. Allows constant temperature throughout the year = constant production (especially high altitude area) 

3. Prevention of loss of water vapor (they have a constant supply of water) 

4. Avoid frost damage to seedlings (in the spring time) Polythene tunnels are usually used to protect growth of seedlings in spring time, and removed to allow full growth in summer 

5. Glasshouses are often warmed by the burning of fossil fuels

= increase carbon dioxide level (increase concentration of substrate for photosynthesis) --> more product and growth

= inefficient burning of fossil fuels lead to the production of ethene gas, which turns out to stimulate fruit ripening (especially tomato) 

The polythene tunnels has polythene as surface on its framework and again allows light to penetrate to the interior.

This is used in less developed country as it is cheaper.

Advantage: more adjustable and movable

Disadvantage: less shelter for plant; less effective (which may decrease total output) 

2.89 Hormones

Understand the sources, roles and effects of the following hormones: ADH, adrenaline, insulin, testosterone, progesterone and oestrogen. 

Hormones are made in endocrine glands and are chemical messengers which travels in through blood in the plasma. (Because endocrine glands do not have ducts which carry hormones to target organs).

Adrenaline

Source: adrenal glands
Target: (many organs) e.g.) Heart

Excitement, anger, fright or stress 

Prep"Flight or fight" (attack or run for your life!)

Effects: 

- increased heart rate

- increased depth of breathing and breathing rate

- increased sweating

- hair standing on end (goose bumps)

- dilated (wider) pupils

- pallidness = blood is redirected to muscles

ADH - anti-diuretic hormones

Source: pituitary gland (in the brain)

Target: Collecting duct (of kidney tubules)

Controls amount of water to be reabsorbed into the blood in the kidney tubules (collecting duct) 

Insulin

Source: Pancreas

Target: Liver
Effect: Storage of glucose --> reduce blood sugar level 

Controls glucose level in the blood and keep it steady to prevent illness

Insulin is released after a meal (because glucose level rises after meal) to convert glucose into glycogen for storage and is insoluble. 


Glucagon
Source: Pancreas
Target: Liver
Effect: Break glycogen down into glucose in the liver 

Testosterone (male only)

Source: Testes
Target: (many organs) e.g.) Testis

For secondary growth and sexual characteristics in boys

Progesterone (female only)

Source: Ovaries

Target organ: Uterus Lining

Prevent the uterus lining from breaking down so that fertilized egg can plant into endometrium. (Maintain the lining of uterus.) If no sperm is present then ovaries stop producing progesterone and endometrium wall breaks down, resulting in menstrual bleeding.

Oestrogen (female only)

Source: Ovaries
Target: Uterus Lining
Effect: Buildup to the thickness of the uterus lining 

Responsible for secondary sexual characteristics 

Work with progesterone for menstrual cycle; Produce LH hormone that causes ovary to release its egg (ovulation) 


Difference between nerves and hormones:
- Hormones can have different effects

2.88 Skin and Temperature Regulation

Describe the role of the skin in temperature regulation, with reference to sweating vasoconstriction and vasodilation

Stimulus: Bood temperature (change in internal temperature)
Receptor: Hypothalamus 
Effector: Skin
Response: Cooling down/ Warming up 

Core temperature is controlled by Hypothalamus. It is a part in the brain that monitors temperature of blood passing through the brain (detects changes in temperature of blood). 

It is also responsible for ADH (osmoregulation).

The keeping of inner conditions within acceptable limits, such as water or temperature, is called homeostasis. 

Skin is responsible for temperature regulation within our body.

The core temperature of our body is 37 C. It is important to maintain our body temperature at about 37 C because enzyme is most efficient at this temperature.

Temperature control is a negative feedback. This means to any change in the environment, the negative feedback system will try to minimize the change as much as possible.

Blood sugar and water level are also controlled by negative feedback system. 

Decreased temperature (too cold) --> trying to warm up

- Vasoconstriction - capillaries narrows, so they carry less blood. This keeps heat inside the body

- Reduce sweating

- Hair erection (goose bumps) - muscles contract to makes hair stand up in order to trap the layer of air to avoid heat from escaping (it is a poor conductor of heat) 

- Shivering - releases extra heat from increased respiration

- Insulation from a layer of fat under the skin

Increased temperature (too hot) --> trying to cool down

- Vasodilation - Capillaries widened so more blood can be carried to the surface. heat transferred out of the body through conduction and radiation.

- Sweating occurs for evaporation as it reduces amount of heat. 

- Hairs lay flat  = less air is trapped so heat can transfer out of surroundings

- No shivering occurs. 

2.87 Eyes' Response to Stimuli

2.87 Understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity

Focusing Near and Distant Object

Cornea bends light to bring them to a focus on retina. 

Lens sharpen the image and makes it "clear".

For far objects, the rays of light entering the eyes are almost parallel. This means it requires less bending to bring focus on retina.

As a result the ciliary muscle relaxes --> suspensory ligaments pulls the lens to make it thin

For near objects, the rays of light entering the eyes are greatly diverged. Therefore more bending is required for focusing. 

Ciliary muscle then contracts, reducing tension on the lens. The lens then "snap" back into fatter shape, bending light more. 

Changes in light intensity

Iris control the amount of light entering the eyes by changing the size of pupil. 

It contains circular and radial muscles. 

Bright = circular muscles contract, radial muscles relax

This makes pupil smaller and less light can enter the eyes. 

Too much light entering the eyes can do damage.)

Dim = circular muscles relax, radial muscles contract 

This makes pupil bigger and so more light can enter the eyes

This helps us see in darker places (the eyes is trying to collect as many light as possible to see clearly) 

2.86 Eyes

2.86 Describe the structure and function of the eyes as receptor

Eye is the receptor that detects light.

Stimulus : Light

Sense: Sight

Ciliary Muscles - contract or relax to alter shape of the lens (for focusing)

Cornea - allows light in and bends light

Iris - (colored part of the eyes) change pupil size to control the amount of light entering the eyes

Pupil - hole in the centre of the eye in which light enters

Lens - change shape to focus light (of near and far objects)

Vitreous Humour - (transparent, jellylike substance) supports the back of the eyes

Retina - contains receptor cells (nerves) which is concentrated on one part of the eye. It change light into electrical impulse

- Rods - sensitive in dim light (but can't see colors as cones does not work well in dark) 

- Cones - detect colors, work best in bright light

Sclera - Protect the eyes

Suspensory ligaments - hold lens in place as it changes shape (pulls or contract lens in response to ciliary muscle)

Optic nerve - carries electrical impulse to the brain (not receptor!)

The eyes contain three pairs of eye muscles which helps it move.

Circular & Radial - located in the iris, controls pupil size  

Ciliary - controls lens shape

2.8 Reflex

Describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object

Reflex is the simplex type of response. It is very quick and is involuntary (automatically happen without you being able to consciously controlling it). Reflex reactions are often for self-protection, such as blinking, sneezing, or pulling your hand away from a hot object. 

stimulus --> receptor --> sensory neurone --> relay neurone in CNS --> motor neurone --> effector --> response

Impulse are usually passed from sensory nerves and remains in the spinal cord without going into the brain. The response is then processed in the spinal cord itself and then pass directly through the motor nerves to the effector (muslce) to bring about a response. It made the response much faster. 

Input produces the same output. This means it is a ‘fixed decision’ to bring about reflex. 

The small nerve called relay nerve in the spinal cord directly connects sensory nerve to the motor nerve so the response can take place. 

They know which relay nerve to target because it is encoded within our DNA.

For example, you touch something hot you will immediately pull your hand away from it --> this is reflex

The “OUCH” came AFTER the reflex and it decided by the brain (as part of the information goes into the brain as well) 

This happens after because reflex response is always faster. 

The reflex arc for touching hot object:

Stimulus (pain sensor responding to heat) --> sensory neuron --> spinal cord --> relay neuron --> motor neuron --> effector (muscles) --> response (pulling your hand away from the heat source)