5.15a Genetically Modified Plants

Key Points:
1. Maize can be damaged by the larvae of the European cork borer. This can cause up to 20% loss of crop yield.
2. The existance of a bacterium called BT, one of the chromosomes contains a gene which produces BT toxin. This is known to kill the cork borer larvae.
3. The first step is to take a restriction enzyme and cut out the gene of the BT which produces the toxin. This has to be transferred to the cells of the maize plant. This isnt easy. The technique which is being used is to use a gene gun and fire tiny pieces of gold covered with the BT gene and firing them at high velocity into the plant. This makes the maize cells contain BT. Kills larvae. Gives the maize resistance to damage caused by the cork borer.

5.14 Humulin

Key Points:
1. In 5.13b we saw the making of transgenic cells using a virus capsule and a bacterial cell.
2. A culture of this bacteria will be put in a fermenter and this culture will need to be provided with nutrient, temperature and pH and the gases which are in the chamber. By creating the optimal temperature, the population will increase and the bacteria manufacture more and more insulin.
3. The product will then be removed and then purified. There are many purifications needed to make it safe for humans. Called downstream processing. Humulin.

5.13b Hosting recombinant DNA

Key Points:
1. In 5.13a Recombinant DNA was introduced. It is a mixture of the human gene and the bacterial plasmid.
2. Inside a virus is the nucleic acid (DNA or RNA) and around this is the protein shell. The first thing to do is to remove the RNA from the virus. The capsid is all that is required. The plasmids are taken up by the virus and the virus will act like a vector
3. This will help transfer the DNA into the host cell. The reason for this is that this virus is known as a phage, and this infects bacterial cells. The virus will attach itself to the cell membrane of the bacteria and insert the DNA into the host cell. At the end of this process, there is a bacterial cell which contains the recombinant DNA including the human gene for insulin. Transgenic.

5.13a Recombinant DNA

Key Points:
1. The image above represents a plasmid. Plasmids are found in bacterial cells, and they are a ring of DNA. Don't carry very many genes.
2. The diagram on the right shows a virus. Virus has a protein shell called a capsid, and inside there will be either DNA or RNA. No other cellular components.
3. The third diagram shows a human chromosome, this is a length of DNA. Chromosome is made of DNA. A gene picked, this one is a code for insulin.
4. The restriction enzyme is chosen and this will cut out the gene for insulin. Having cut the gene, a plasmid will also be cut with the same restriction enzyme. This leaves the plasmid looking like a broken circle.
5. The next stage is to introduce the human insulin gene. The gene will be inserted into the plasmid and this will be completed by adding a DNA ligase which will join the DNA onto the plasmid.

This combination is known as recombinent DNA.

5.8 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

5.8 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

Suitable conditions inside an industrial fermenter are extremely important. For example, the enzymes must be kept around their optimal temperatures or else they will be slow or will denature. They also need their optimum pH. Air inside must be regulated so that oxygen is constantly put in and CO2 constantly taken out. It also needs to be sterile inside the chamber, so steam is put inside to kill off any bacteria inside.

The temperature can be regulated by the use of a plate which gets hotter or less hot which controls the temperature.

There is a mixer that ensures there are no lumps and to evenly distribute the substances.

5.7 understand the role of bacteria (Lactobacillus) in the production of yoghurt

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

• Lactobacillus is added to pasteurised milk
• The bacteria consumes some of the milk and produces lactic acid
• Causes the milk to go denser and compact together

5.6 describe a simple experiment to investigate carbon dioxide production by yeast, in different conditions

Describe a simple experiment to investigate carbon dioxide production by yeast, in  different conditions

An experiment which would be viable would be:
1. To get a set amount of yeast and sucrose and to mix them. In this example, it would be 10 ml of yeast with 15 ml of sucrose.
2. Then a set amount of the solution should be added to 5 or more different test tubes.
3. The solution HAS to respire anaerobically, so no more oxygen can be let in. A bung put on top of the test tube will stop any air from coming in.
3. A change in each of the test tubes must be apparent, in this case we will use temperature. One of the test tubes will be at 5 degrees, and the temperature goes up by 10 until all the test tubes are done.
4. The gas can be collected in a water trough, using the displacement of water to determine how much CO2 is produced.

5.5 understand the role of yeast in the production of beer

Yeast in the production of beer

Alcohol is produced with the anaerobic respiration of yeast, which produces carbon dioxide, water and ethanol.

The equation is : Glucose -> CO2 + H2O + Ethanol

5.4 understand the reasons for pest control and the advantages and disadvantages of using pesticides and biological control with crop plants

5.4 understand the reasons for pest control and the advantages and disadvantages of using  pesticides and biological control with crop plants

Pests are an annoyance to people wanting to produce large amount of crops. These include weeds, insects and moulds

Advantages

Reduces the number of insects which eat the crops, resulting in higher crop yield. Also helps stop the spread of disease in crops. This is also a very easy alternative to biological control which is much more complicated

Disadvantages

Can cause a problem in the food chain, for example if many insects eaten by birds are poisoned, then the birds will then be poisoned and this will lead on and on. Furthermore, some pesticides can affect humans. DDT is dangerous, and doesn't degrade easily.

Biological control is similar to pesticides in respect that it is intended to get rid of pests and disease. One example of biological control would be releasing lots of ladybugs into a group of crops to kill insects which the ladybugs feast on. This doesn't cause any harm to the crops and avoids pesticides completely.

5.3 understand the use of fertiliser to increase crop yield

The use of fertilizer can increase crop yield.
Fertilizers often improve the quality of the soil, returning many nitrate ions and such to help the plant grow and obtain more nutrients.
This can help the crops grow FASTER and makes them HEALTHIER.

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

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

Carbon Dioxide

http://www.omafra.gov.on.ca/english/crops/facts/00-077.htm

This photo clearly demonstrates that the amount of CO2 affects the crop yields. An increased amount of carbon dioxide (or a higher concentration) causes an increase in the rate of photosynthesis. However, there reaches a point where the rate cannot go any higher.

Temperature

It is apparent that when the temperature is increased, the rate of reactions taking place inside the crops increases as well, increasing the growth rate. As mentioned, there is an optimal temperature. However, too much heat can cause the plant to dehydrate, as well as causing the plant to grow badly. The enzymes can denature.

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

1. Glasshouses and polythene tunnels can be used to increase the yield of certain crops
2. These houses protect the crops from the environment and help regulate the optimal temperature, CO2, water and fertilizers.
3. These give the crops best conditions for photosynthesis.
4. A note to point out is that all of these variables which affect a crops growth and health are all CONTROLLABLE, they can be changed due to the nature of being inside a greenhouse/glasshouse. This makes a definite advantage if mass farming to produce high yields.

Fertilizers can help increase yields, whilst chemicals control pests, weeds and diseases.

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

1. Our body produces hormones to tell different parts of the body what to do. These are produced in the hormonal system in glands. Small amounts are carried around in the blood. Responses are NOT reflexes, these responses take minutes or can go on for years.
2. Thyroid makes thyroxin - Regulates the rate of metabolism
Pituitary is at the base of the brain. Produces many hormones. Regulates sperm and egg production, water balance, growth etc.
3. The Pancreas makes insulin and glucagon, insulin lowers blood sugar, and glucagon increases blood sugar.
Adrenal glands produce adrenalin - Adrenaline helps the body cope with fear and anger in an emergency, or pain. Basically, it converts glycogen into glucose, increases the heart rate, bronchioles widen for more air, blood vessels widen to the brain and muscles, blood vessels to the gut narrow, and hairs are raised.
4. Testes make testosterone in males, and these develop the male features during puberty. The ovaries create oestrogen and progesterone in females, and these control the menstrual cycle and female features during puberty
5. Hormonal glands are affected by feedback. If the level of a hormone is too high, then less is produced and vice versa.
Sometimes things can go wrong. Sometimes too much/too little

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

Key Points
1. To keep in a state of isotonic homeostatis in most cells of the body, the skin reacts to different temperatures by doing different things.
2. There are many different types of sensors in the skin; Pain sensors are at the skin surface, touch sensors are attatched to the base of our hairs, some pressure sensors are deep in the skin and some pressure sensors are close to the surface. Temperature sensors respond to temperature.
3. We sweat when we are hot because the heat stimulates the temperature sensor to send information to the brain telling us that we are hot. Then the brain responds by sweating from pores in our skin, and the sweat evaporates and we get cooler.
4. We get goosebumps and shivering when we are cold because the cold stimulates the temperature sensors in the skin to send information to the brain telling us that we are cold. The brain then responds by giving us goosebumps and increasing the surface area of our body to absorb more heat, and to shiver.

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

Key Points
1. When light enters your eye, it passes through the cornea and lens, and then is focussed onto the retina. There are cells which are sensitive to light and these are called rods and cones.
2. When light stimulates them, they send information to the brain.
3. When you are looking at a distant object:
-Your ciliary muscles relax
-The suspensory ligaments tighten
-the lens becomes THIN, and the distant object is focussed.
4. When you are looking at a near object,
-Ciliary muscles contract
- Suspensory ligaments slack
-the lens becomes fat or thicker, and the near object is focussed.
5. The image which goes into the eye is actually inverted, but the brain corrects the inversion.

2.86 describe the structure and function of the eye as a receptor

Key Points
1. The eye contains tear glands, tear ducts, a cornea, a pupil, the iris, the sclerotic layer, the socket, the eye muscle and the optic nerve to the brain.
2. The function of the eye is to collect light and translate it into images we see with our brain.
3. Going into more specifics about the eye, there is the cilary muscle, which changes the thickness of the lens while focussing. Then there is the aqueous humour, which is the watery liquid filling the front of the eye.
4. There is also the lens, which changes shape to focus light onto the retina, and the retina is the inner light sensitive layer which detects light.
5. The iris controls the amount of light entering the eye, the suspensory ligaments hold the lens in place and the sclerotic is a tough white protective layer. The choroid is the black layer which contains blood vessels, the vitreous humour is the jelly like substance which supports the back of the eye, and the fovea is the most sensitive part of the retina.

2.85

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


Key Points:
1. A synapse is the gap between different neurones - this allows the electrical impulse to jump across at faster speed and results in a faster impulse. They also function as a resistor and a junction box. Synapses are easily affected by drugs and this can either slow down or heighten peoples' reactions.
2. Reflex arcs are stimulation's caused by the body to protect one from harm or damage. An example would be something very hot.
3. STIMULUS (HEAT) -> RECEPTOR (PAIN SENSOR IN SKIN) -> COORDINATOR (CENTRAL NERVOUS SYSTEM) -> EFFECTOR (ARM MUSCLE) -> RESPONSE (REFLEX ARC)
4. In specifics, the heat causes the pain sensor in the skin to send a message along the sensory neurone to the central nervous system, in which it gets passed on to the relay neurone which then passes to the motor neurone and carries the impulse to the muscle (in this case the arm muscle), and causes a reflex.
5. Some other examples of reflexes are: Blinking with dust in your eye, Coughing when liquid or food goes down the trachea, blinking when someone claps in your face etc.

2.84

2.84: understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses


Key Points:
1. Messages are carried by nerve impulses and these happen very quickly. These are electrical signals.
2. An impulse travels across the axon rapidly because it can jump from one fat globule to the next (however this only occurs in mammals). This insulates the axon as well.
3. In multiple sclerosis the fatty globules break down and impulses also slow down or even stop. This disease causes people to lose control of their muscles.
4. The axon can be over 1 meter long.
5. Nerve cells have a different structure to other cells, but retain the basic things like cytoplasm, cell membrane and a nucleus. Their shape is stretched out to form the axon.

2.83

2.83: recall that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves


Key Points:
1. The main parts of the nervous system are the brain and the spinal cord.
2. They are made up of nervous tissue , and the brain is protected by the skull and the spinal cord is protected by the back bone.
3. Nerves are what connect the central nervous system to the rest of the body, and these are made of neurones
4. Sense organs are receptors - they send messages to central nervous system.  These are sent via the sensory neurones.
5. Muscles and glands are effectors - the central nervous system send them impulses along motor neurones

2.82 Communication

Key Points:
1. Responses can be controlled by nervous or hormonal communication. In the example, the motor nerve is shown and one side is embedded in the spine and the other end is in the effector, probably the muscle.
2. The electrical impulse is carried down inside the nerve from the cell body to the structure called the synaptic knob -> connects to muscle. These cells can be up to a meter long.
3. The long structure is known as an axon. In mammals the axon is surrounded by a lot of fat in globules - this is to increase the speed on impulses.
4. The second way is known as endocrine system. This involves an endocrine gland and this produces a hormone. Manufactured in the glands, the adrenal glands. The hormone is secreted into the blood, the hormone being adreneline. This will arrive at the target tissue/organ.
5. Contrasting with the nerve system, some hormones can have multiple targets and bring about multiple effects.

Nerves = Fast, electrical impulse, single effect, reflex, carried down the axon.
Hormones = Relatively slow, can have multiple effects, secreted into blood.

2.77b Thermoregulation

1. In humans we must maintain a constant temperature - 38-37 C. In order for this to work our receptors, the Hypothalamis, responds to the stimulus, the temperature of blood, and if there is need for change then the skin will change the temperature.
2. The response will be either an increase or decrease in body temperature. Feedback to hypothalamis and based on new input, new output produced.
3. Major component of skin - Sweat glands and capillary network. Allows blood to move closer or further away to the skin.
4. Stimulates cooling which involves sweating and the bloodflow to the surface of the skin increases. Dilated blood vessels. Increases exchange of heat like radiation and evaporation.
5. Stimulates heating, which involves shivering, raised hairs. reduces heat exchange with the external environment. Vary UP and DOWN around the fixed point

2.77a Thermoregulation

Key Points:
1. Homeostasis is the process in which the internal environment of an organism is kept constant and relative to the outside environment. It also affects water content and body temperature.
2. Homeo - Something being the same Stasis - Fixed Conditions. The idea is that the conditions are kept constant. Homeothermic refers to temperature, and maintaining the same temperature.
3. Some organisms keep their body temperature constant when the temperature changes, and some adapt to it. The name of the first process is called thermoregulation.
4. Homeostatis also keeps the optimal temperature for enzymes.
5. The optimum temperature for the enzyme reaction is roughly the same as which mammals maintain their body conditions.

2.76 Sensitivity

Key Points:
1. Organisms are able to respond to changes in the environment.
2. S from MRSGREN stands for sensitivity. This characteristic enables organisms to respond to changes in the environment.
3. Types of change = Light levels, Temperature, Pressure and Chemical changes.
4. To detect and respond to these stimuli, the organism must possess receptors and effectors.
5. An example of an effector is a muscle or a gland.