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)

1. Maize is damaged by the larvae of the european corkborer which can lead to up to 20% crop yield
2. The bacteria Bt has a gene which produces Bt toxin gene which kills the corkborer larvae
3. First, take the restriction enzymes to chop the Bt toxin gene out
4. It is then transferred to cells of the maize plants however it is not easy and gene gun is the technique
5. This involves taking tiny gold particles which are coated with Bt gene. These are fired at a high velocity introducing the gene to the interior of the plant cell
6. This means that the maize gets the gene and can now kill the larvae
7. This gives the maize resistance and increases yield

5.14- Humulin

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

• A culture of the bacteria will be injected into the fermenter
• Nutrients need to be provided 
• Gases, pH and temperature need to controlled
• By creating the optimal temp. --> population will increase and the bacteria will manufacture the protein insulin
• The bacteria inside the fermenter will manufacture the insulin protein from amino acids
• Then the product needs to be removed and purification needs to be carried out (downstream processing)
• Genetically engineered human insulin is called Humulin

5.13

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

Plasmids:

·         Found in bacterial cells

·         Ring of DNA

·         Small and don’t carry many genes

Viruses:

•          A protein shell known as a capsid
•          Inside, there is nucleic acid- DNA or RNA

Human Chromosome is made of DNA and we will talk about a gene which codes for insulin (hormone controlling blood sugar levels) 

How to form the Recombinant DNA?

1.  .    Restriction enzyme is selected which cut the gene for insulin
2.  .    Then the plasmid will be cut with the same restriction enzyme
3.  .    The human insulin gene is inserted into the plasmid
4.        Then the ligase enzyme is applied to join the DNA
5.      This is now known as a recombinant DNA

After the recombinant DNA is formed:

•          Virus is used as a host cell
•          Nucleic acid is removed from the virus leaving us with an empty shell
•          The plasmids are inserted into the virus which will act as a vector
•          The virus infects bacterial cells and so is able to attach to the cell membrane of the bacteria and insert the Recombinant DNA
•          This will lead to a bacteria containing the recombinant DNA

5.12

Describe the use of restriction enzymes to cut DNA at specific sites and ligase enzymes to join pieces of DNA together

Restriction Enzymes:

• These are used to cut into the DNA at a particular location
• The location where to cut is identified by the base sequence

Ligase Enzymes:

•  These join the DNA together

5.11- Breeding Animals

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

Using Cow as an example, the desired characteristic is milk yield.

• Some cows produced 50ml or 150 ml of milk but most cows produced 100 ml
• The farmer will collect all the milk
• The farmer chooses the 150ml milk cows as his breeding cows
• In the next generation, 
• Some cows produce 100ml or 200 ml of milk but most cows produce 150 ml
• He will then select the 200ml cows for breeding

Milk yield must be genetic for this to work. 

5.10- Breeding Plants

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


The number of rice grains is under the control of genes. The farmer wants to improve the no. of grains per plant and therefore increase the yield.

• The plants have 6, 8 and 10 grains per stem
• The farmer harvests the 6 and 8 stem grains
• The 10 grain stems are planted
• In the next generation:
• The plants have 8, 10 and 12 grains per stem
• The farmer harvests the 8 and 10 grain stems
• But selects the 12 grain stems for planting

The grain of rice plant gradually increases which means the yield has increased. 

5.9- Fish farming

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

Fish are an attractive product for farmers as they have low fat and high protein. They are efficient at turning their nutrient into fish mass. 

• Fish farming allow us to control the quality of the water, predators and reduce pests/diseases
• By controlling these factors, the yield of fish will increase
• High density of fish--> possibility of fast transmission of disease, pests
• Farmers use antibiotics in some cases which is of concern to human health
• Pesticides might also be used--> harmful to humans

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 fermenter usually has two steel jackets with water in between and this is known as the cooling jacket
• The steam which goes inside sterilises the tank in between the fermentations
• There is also a heater to raise the temperature inside the fermenter, combination of the cooling jacket and the heater allows for the optimum temperature for fermentation
• Nutrients (food for micro-organisms) are also added through a pipework
• A temperature probe inside the fermenter tells us whether to use the cooling jacket or the heater
• Requires the addition of micro-organisms through another tap
• The pH probe is built in to allow the maximum rate of reaction
• A motor is used to stir the reaction which agitates the mixture --> spreading the micro-organisms
• A way to drain off the product is required which leads to downstream processing which requires the purification of the product

The fermenter allows the optimum growth conditions for the micro-organism so it is able to produce the required product

5.7- Yoghurt

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

1. Cow produces milk
2. It is then pasteurised which removes pathogens such as TB
3. This heat treatment kills of all pathogens in the milk
4. The milk sugars are then converted into Lactic acid
5. This can be done by incubating the milk at 45-46 degrees and adding  Lactobacillus
6. Lactobacillus produces enzymes which break down the milk sugar (lactose)
7. Acid will result in a lower pH which causes milk proteins which then solidify to for Yoghurt 

5.6- Experiment to investigate production of Yeast

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

1. Mix yeast suspension with a sucrose solution and place in a boiling tube
2. A delivery tube must be attached to collect the CO2 formed
3. The CO2 can be collected over water 
4. Or bubbled through limewater

5.5- Beer Production

Understand the role of yeast in the production of beer

• Beer is broken down from glucose into Ethanol and Carbon Dioxide (Anaerobic respiration)
• Using Yeast which provides the necessary enzymes for the reaction
•  Ethanol is flavoured using Hops (plants)
• Starch --Amylase--> Maltose --Maltase--> Glucose
• Sources of starch are Wheat, Barley seeds and rice

5.4- Pesticides and Biological Control

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

Monoculture: 

• Large fields with the same type of crops
• Susceptible to pests (variety of living things)--> reduces productivity of farming--> loss of food and financial impact on farmer
• Pesticides- Chemical and are designed to kill a pest
• Advantages:
• Chemicals --> Easy to obtain
• Easy to apply
• Very effective
• Disadvantages:
• Very toxic- harmful to humans
• Bio accumulation
• Mutation in the pest leads to resistance
• Pesticides may not work/ may need to be applied in a higher concentration

Biological Control: 

• Cactus flourished in Australia but there were no natural predators of it
• It needed to be removed as it was taking up agricultural land
• Moth (Cactoblastis) was introduced from another country (Alien species)
• Advantages:
• No toxic chemicals involved
• Less impact on humans and wildlife
• Disadvantages:
• Not 100% effective
• Difficult to control
• A danger that an alternative food source might be found for the alien species
• Sometimes difficult to match a predator to the prey

5.3- Fertilisers

understand the use of fertiliser to increase crop yield


Fertilisers:

• Generally take the form of nitrates, phosphates or a combination of both
• These compounds are taken up by the roots 
• Used in the leaf to form proteins (nitrates) and DNA, membrane structure (phosphates)
• Can be divided into two groups:
• Organic
• Produced from animal waste--> Cow faeces
• Goes through decomposition and fermentation
• Forms slurry which gives the plant nitrates and phosphates
• Artificial
• Chemicals which are synthetically produced
• Potassium Nitrate and Ammonium nitrate
• They will go into solution in the soil water
• Releases nitrates 
• Promotes growth in the same way as organic compounds

5.2- Crop yield

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

Increased concentration of CO2:

• Substrate
• Rate of photosynthesis increases which means that there is a higher yield

Increased temperature:

• Increase in rate of photosynthesis which means that there is a higher yield
• There is an optimum temperature along the graph
• Avoiding frost damage, Constant temperature --> higher yield

Both of the conditions have limits

5.1- Glasshouses

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

Glasshouses- Simple house structure, all surfaces are glass which allow light to pass through

1. The initial source of energy is solar radiation
2. Light goes through the glass
3. Light is absorbed by surfaces inside the glasshouse
4. Energy is re-emitted as heat
5. Heat warms the air- raising the temperature
6. Warm air is trapped inside which causes convection currents (warm air rises and moves back down after being cooled at the top of the glasshouse)

Polythene tunnels- Framework with polythene over it, allows light to pass through, cheaper and more adjustable than the glasshouse

Increasing crop yield: 

• High temperatures --> optimum temp. for enzyme reactions (photosynthesis)
• Constant temp. throughout the growing year--> constant production
• Prevention of loss of water vapour --> crops do not dry out
• Avoid frost damage (particularly seedlings)
• Glasshouses are often warmed by burning fossil fuels:
• Increase in carbon dioxide levels inside the glasshouse
• Increased concentration of substrate for photosynthesis
• Production of ethene --> Stimulate fruit ripening

2.89

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


Hormones- Chemicals released by a cell or a gland which sends out messages that affect other parts of the organism. 

• ADH- controls the amount of water in the blood. It is produced in the Pituitary gland. 
• Adrenaline- Increases heart rate and breathing rate during exercise. It is produced in the Adrenal gland.
• Insulin- Decreases the level of glucose in the blood. It is produced in the pancreas. 
• Testosterone- This hormone triggers puberty in boys. It is produced in the testis. 
• Progesterone- Controls the menstrual cycle in females. It is produced in the ovaries.
• Oestrogen- Triggers puberty in girls and stimulates growth of uterus lining. It is also produced in the ovaries. 

2.88

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

• When the body feels that it is too hot:
• Hairs on skin lie flat (less insulating air trapped)
• Sweating starts
• Blood is diverted close to the surface of the skin (more heat radiation)
• When the body feels that it is too cold:
• Hairs on skin stand up (more insulating air trapped)
• Sweating stops
• Shivering starts, so muscles respire more, producing more heat
• Blood is diverted away from the skin (less heat radiated)
• How is blood diverted?
• Arterioles in the skin can open and close in response to nerve messages
• Vasoconstriction: Arteriole closes
• This happens when the body is cold
• Vasodilation: Arteriole opens
• This happens when the body is hot

2.87

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

• Eye- Focuses light onto photo receptors
• Photo receptors- the sensory cells of the eyes known as the rods and cones
• When focussing on distant objects:
• The rays of light are almost parallel
• Lens remains flat and focussed on the retina (the inner area of the eye)
• The cilliary body relaxes
• When focussing on near objects:
• The lens has to adjust to the scattered light rays
• The cilliary body contracts which forces the Lens to become rounded
• This allows the image to be focussed on the retina

2.86- The eye

 Describe the structure and function of the eye as a receptor

• The eye is made of three coats: 
• The outermost layer consists of the Cornea and Sclera 
• The middle layer consists of the Cilliary body, Choroid and the Iris 
• The innermost layer consists of the Retina 

• The function of the eye is to receive light and send it to the brain which interprets these signals 
• The light first enters the cornea
• There are no blood vessels in the cornea as the light must be able to travel through uninterrupted 
• The aqueous humour is a nutrient filled liquid which provides nutrients to the cornea and the lens
• The pupil controls how much light passes through from the cornea to the lens
• The iris is two sets of muscle fibres that control the size of the pupil

2.85- Reflex arc

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

• The hot object is the stimuli
• The receptor is the sensor in our finger and this detects the hot object
• The electrical impulse travels along the sensory nerve to the CNS
• It is then passed on to the relay nerve which in turn passes it onto the motor nerve
• The impulse is then carried to the finger to which the response is to move the finger away
• The brain also receives some of the impulse but not all of it
• This makes the process faster and prevents more damage

2.84- Impulses

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

• Receptors:
• These detect the stimuli like temperature
• They are connected to the CNS by the sensory nerve
• The electrical impulse travels to the CNS using the sensory nerve
• It is then transferred to the motor nerve by the relay nerve
• The motor nerve carry the impules from the CNS to the effectors
• The genes store the information about which relay nerve connects where
• Some impulses also go to the brain 

2.83- Central Nervous system

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

• The nervous system coordinates the activities of all the parts of your body
• The nervous system consists of the brain and the spine
• The brain is protected by the skull and the spine is protected by the vertebrae
• The central nervous system contains millions of neurons
• The spinal cord:
• Conducts sensory information from the peripheral nervous system to the brain
• Conducts motor information from the brain to the various effectors
• The brain:
• Receives sensory input from the spinal cord as well as its own nerves
• Initiates appropriate and coordinated motor outputs

2.82- Communication

Describe how responses can be controlled by hormonal or by nervous communication and understand the differences between the two systems

1. First way to connect the coordinator to the effector:

• The left side of the nerve would be embedded in the spine
• The right side will be connected to the effector (muscle)
• The electrical impulse is carried inside the nerve from the cell body to the synaptic knob
• This is where it connects to the muscle
• The long structure in the middle is known as the axon
• This is surrounded by the schwann cells which is a layer of fat
• These form Myelin sheath which increases the speed which increases the speed of nerve conduction

    2. Second way of connecting the coordinator to the effector:

• This is known as the endocrine system
• The endocrine gland produces a chemical (hormones) 
• The hormone is secreted into the blood
• The hormones travels through the blood stream and goes to the target tissue
• The hormones can effect multiple target tissues and can bring about multiple effects

1. Nerve Impulses:
• Fast
• Nervous coordination is Instantaneous
• Sent through neurons
• Enables body to react to external environment
2. Hormone Impulses:
• Really slow
• Prolonged effect on body
• Enables body to react to internal environment 

2.77b- Thermoregulation

Understand that Homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis

• Negative feedback loop is a method of control and maintaining constant conditions
• Receptors- Hypothalamus responds to the temperature of the blood
• The ideal temperature in a human is 37-38 degrees
• The temperature is fed back to the brain so that the required changes in the temperature can be made
• Effectors- Skin can be used to change the temperature of the blood 
• Skin:
• Sweat Glands- used to control body temperature
• Capillary networks- allow blood to move closer or further away from the surface of the skin
• If body temperature increases, the hypothalamus will make the body cool down by:
• Sweating
• Increase blood flow, the blood vessels dilate which increases the exchange of heat to the outside of the body by the processes of radiation and evaporation of sweat
• If body temperature decreases, the hypothalamus will make the body heat up by:
• Shivering 
• Vasoconstriction
• Raised hairs

2.77a- Thermoregulation

Understand that Homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis


Homestasis- Where the conditions are kept the same or constant
Homeothermic- The temperature is kept the same

In mammals, when the temperature of the environment changes, their body temperature remains constant as they carry out thermoregulation which is an example of Homeostasis. These are Homeothermic organisms.

By looking at the rate of reaction to temperature graph, we see that there is an optimum temperature. Which is why mammals try to keep their body temperature at the optimum temperature as much as possible.

2.76- Sensitivity

Understand that organisms are able to respond to changes in the environment


Stimuli- Changes in the environment (light, temperature,pressure, chemical)
Receptors- Detect changes in the environment
Effectors- Respond to changes in the environment (muscles and glands)

The response ensures that the organism is able to survive the changes in the environment.