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OCR Categories Archives: B7: Further Biology

B7.5 New technologies

B7.5 New technologies

The features of bacteria that make them ideal for industrial and genetic processes include:

  • Rapid reproduction
  • Presence of plasmids – circular DNA molecules that can be transferred easily between bacteria
  • Simple biochemistry – easy to understand and alter
  • Ability to make complex molecules – bacteria can produce molecules that can be used medicinally
  • Lack of ethical concerns in their culture

Many useful products are made by fermentation – which involves growing bacteria or fungus (e.g. yeast) on a large scale. Some of these useful products include:

  • Antibiotics and other medicines
  • Single-cell protein – such as mycoprotein which is used in meat substitute products
  • Enzymes for food processing, for example chymosin as a vegetarian substitute for rennet
  • Enzymes for commercial products, such as washing powders and to make biofuels

In genetic modification, a gene is transferred from one organism to another where it continues to work

  1. Isolation and replicating the required gene
  2. Putting the gene into a suitable vector (virus or plasmid)
  3. Using the vector to insert the gene into a new cell
  4. Selected the modified individuals

Examples of the application of genetic modification include:

  • Bacteria synthesis of medicines e.g. insulin
  • Herbicide resistance in crop plants – by creating crops with resistance to a herbicide, the farmer can use that herbicide to kill weeds without destroying the crop

Genetic testing may be used to find out if an individual has a genetic disease – a disease which they have inherited and which is a result of a defect in their DNA

To investigate a person’s DNA, white blood cells are used because they are easy to obtain from a blood sample, and unlike red blood cells they have a nucleus containing the DNA.

  1. Isolation of DNA from white blood cells

A small quantity of blood has chemicals added it – the chemicals split open the red cells

The DNA is collected and then replicated (more copies of it are made) so that there is enough to test. The DNA is then broken up into smaller sections using enzymes and put onto a special gel. An electrical current is applied, and the pieces of DNA separate out along the gel.

  1. Gene probe (marker)

Gene probes are created that are mirror copied of the target allele or microsatellite region – the gene probes are attached to a fluorescent chemical that emits ultraviolet light. If the target segment of DNA is present in the DNA sample, the gene probe will attach to it

  1. Adding the gene probe to the sample DNA

The separated pieces of DNA on the gel are ‘blotted’ to split the DNA into single strands. The gene probe is added and if the gene the scientist is searching for is present, the gene probe will bind to it because it has a complementary base sequence to the gene being investigated. This process is called Southern blotting

  1. Using UV light

The gel is then viewed under UV light. If the gene is present, the gel will glow at that point. The gene has therefore been identified as being present in the person’s DNA.

Nanotechnology means manipulating and using particles of materials that are very small – about the size of some molecules.

Nanotechnology can be used in food packaging. For example, silver nanoparticles are anti-microbial and can be used to prevent harmful bacteria from growing inside food packaging. This extends the shelf life of the food.

Nanotechnology can also be used to build biosensors into packaging. These help to identify when food has started to deteriorate as a result of microorganisms releasing harmful substances as they break down the food.

 

Stem cells are being used to reverse damage to the body

Leukaemia – stem cells can help to treat leukaemia, a disease that kills white blood cells – traditionally a leukaemia patient would need to have their own bone marrow removed and replaced with that from a tissue-matched donor

However, using stem cells that have been harvested from the patient’s own body has a significant advantage – it means that the patient has new complement of blood cells that are genetically the same as him/her

Biomedical engineering involves solving medical problems using new materials and man-made parts.

The human heart has its own pacemaker, which sends an electrical signal to the heart muscle cells that makes them contract at the right time. In some people, this natural pacemaker doesn’t work properly. Doctors can insert an artificial pacemaker into a patient’s chest which controls the contraction of the heart.

Heart valves can sometimes become faulty. If this happens it can stop the heart from effectively pumping blood to the lungs and body.

Doctors can now replace faulty heart valves with artificial valves. To do this the patient must first be connected to a heart-lung machine to maintain circulation. The heart is then stopped by the surgeon, cut open, and the damaged valve is replaced.

 

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B7.4 What can we learn from natural ecosystems?

B7.4 What can we learn from natural ecosystems?

In a perfect closed loop system no material enter or leave the system – waste products from one organism or process are used by another organism or process – the output from one part of the system becomes the input to another part.

In reality, it is impossible to have a perfect closed loop system in an ecosystem – this is because organisms migrate out of the area and some nutrients are transported away by the wind, rain or rivers.

In stable ecosystems including rainforests, the output (loses) is balanced by gains.

An ecosystem is a type of closed loop system since most waste materials are not lost but are used as food or reactants.

Within a natural ecosystem, most waste materials are not lost – they can be used as food or reactants for animals, plants and microorganisms:

  • Oxygen is waste product from photosynthesis – it is used in respiration
  • Carbon dioxide is a waste product from respiration – it is used in photosynthesis
  • Dead organic matter (e.g. fallen leaves, fruits, flowers, faeces, remains of bodies) is used directly as food or processed into useful nutrients by microorganisms – these microorganisms use digestive enzymes to break down complex molecules into simpler nutrients.

Different organisms have very different approaches to achieving successful reproduction

To reproduce successfully, organisms need to maximise the chances of the offspring reaching adulthood and reproducing themselves.

Females usually produce a large number of eggs, while males produce large quantities of sperm – this ensures a high chance that at least one successful fertilisation will occur.

When organisms produce large numbers of reproductive cells (such as pollen, sperm and eggs) or reproductive structures (such as flowers and fruit), these ensure that reproduction is likely to be successful.

The unsuccessful cells and structures are recycled into the ecosystem – they are usually used as nutrients for animals or microorganisms.

In stable ecosystems the production of large quantities of these reproductive structures is not wasteful, since the surplus (the number of animals in a given population that are “above” the carrying capacity.

 

 

 

Vegetation is an essential part of many ecosystems:

  • Roots help to stabilise the soil – preventing it from being eroded by heavy rain (especially in rainforests). Vegetation also reduces soil erosion since foliage protects the soil from direct rainfall
  • Trees provide shade from the sun and help to insulate the forest floor at night – therefore stabilising the temperature
  • Transpiration from trees helps to promote cloud formation

Humans benefit from and depend on ecosystems to provide a huge range of resources and processes – these are known as “ecosystem services” – for example:

  • Providing clean water and air
  • Pollination of crops
  • Fertile soil
  • Mineral nutrients
  • Fish
  • Game – wild animals that are hunted for their meat, such as grouse, wild salmon and deer

However, human activities often affect ecosystems in negative ways because human systems are not closed loop systems because some waste leaves the system.

Human waste from households, agriculture and industry leaves the system as non-recycled waste, as well as through pollution from burning fossil fuels – this means the system is losing resources.

Sometimes the waste can build up to harmful, which then affect other organisms – bioaccumulation is when toxins build up in a food chain – the animals at the top of the food chain are affected most severely:

Human activities can unbalance an ecosystem, changing the inputs and outputs so much that the ecosystem can no longer adapt – this means that the system is no longer a closed loop.

Eutrophication is where an excess of nutrients is put into a system, causing the productivity of the system to increase while causing the balance of organisms to change, often drastically and irreversibly.

When humans take away too many resources as biomass, then this reduces the amount available to be recycled within the ecosystems.

For example cutting down a rainforest for wood removes a large number of trees – the tree canopies would have protected the soil from rainfall and the roots would have bound the soil together – the tress would have also provided habitats for other organism.

Removing too many trees causes the closed ecosystem to become open – the soil dries out and is blown away and the organisms that relied on the trees for survival die

Another example is overfishing

In some parts of the world, natural vegetation has been removed and replaced with crops for food or the production of fuels (called biofuels) or by grazing animals

As well as destroying the natural habitat and reducing biodiversity, soil erosion can cause rivers to become clogged up with silt, plus the lack of shade and moisture in the soil can cause desertification.

The use of natural resources by humans can only be sustainable if used at a rate at which they can be replaced

Crude oil is formed from the remains of plants and animals that died millions of years ago – the biomass is covered by silt and rock and subjected to immense pressure and heat – over millions of years this causes the biomass to be converted into oil.

The use of crude oil does not fulfil the requirements of a closed loop system because:

  • Crude oil takes millions of years to form from the decay of dead organisms
  • Energy released from burning crude oil originated from the Sun when these organisms were alive (“fossil sunlight energy”).

Sunlight is a sustainable source of energy – it will not run out for another five billion years – and it allows sustainable agriculture and the growth of natural ecosystems.

Fish populations can be preserved if quotas (a limited amount of something, often specified by law – e.g. there are quotas on fishing that cannot be exceeded) are observed which means that each country has an entitlement to catch only a certain number of each type of fish. Some animal population can be restocked

Forests can be preserved if the trees are replanted – sustainable cropping of forests – involves cutting down selected trees in an area – can also be adopted to maintain the forest ecosystem.

Sometimes, there are tensions between conservation efforts and the needs of local communities. For example, even though the process of mining for gold in the Brazilian rainforest damages the natural ecosystem, the people employed as miners still need to earn money to support their families.

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B7.3 Peak performance – energy balance

B7.3 Peak performance – energy balance

Homeostasis is the maintenance of a constant internal environment – it is achieved by balancing bodily inputs and outputs, while removing waste products.

In order to maintain a constant body temperature, the heat produced within the body (e.g. from respiration) or absorbed from the environment must be balanced by the heat lost from the body.

Sensors in the body are called receptors – they are often located in the sense organs such as the ear, eye and skin. Receptors are groups of specialised cells that can detect changes in the environment – these changes are called stimuli.

Temperature receptors in the skin detect external temperature and send nerve impulses to the brain.

There are also temperature receptors in the brain (in the hypothalamus) which monitors the temperature of the blood flowing through it. The brain processes this information and send impulses to the effectors – parts of the body (e.g. sweat glands and hair muscles) which produce a response to a stimulus.

The hypothalamus acts as a processing centre

 

If the temperature of the body is TOO HIGH then heat needs to be transferred to the environment – this is achieved through sweat being produced by sweat glands which cools the body when it evaporates.

Vasodilation is the widening of the blood vessels (capillaries) that run very close to the surface of the skin.

When the hypothalamus senses hot conditions, it sends impulses which cause blood vessels supplying the capillaries in the skin to dilate (vasodilation) – the increased blood flow to the surface tissues under the skin means that more heat is lost

Dehydration can be caused by increased sweating – dehydration stops sweating from taking place which leads to the core temperature (37˚C) increasing even further.

If the temperature of the body is TOO LOW then the body starts to shiver – shivering is the rapid contraction and relaxation of muscles – these contractions require energy from increased respiration and heat is released as a by-product, warming surrounding tissue.

Vasoconstriction is the narrowing of the blood vessels (capillaries) that run very close to the surface of the skin

When the hypothalamus senses the body is in cold conditions – it sends impulses which cause blood vessels supplying the capillaries in the skin to contract (vasoconstriction) and it reduces the blood flow to the surface tissues under the skin – as a result less heat is lost.

This an example of  effectors working antagonistacally – which means that they do opposite things – this allows a more sensitive and controlled response.

Glucose is needed for respiration – when we eat foods containing carbohydrates, enzymes are needed to break them down into monomers.

Processed foods, compared to fresh foods are foods that have been changed from their naturally occurring state to make them healthier and/or for convenience.

After a meal, the digestion of carbohydrates in the intestines release sugars – these sugars are absorbed into the blood.

High levels of sugar, common in some processed foods are quickly absorbed into the blood stream causing a rapid rise in the blood sugar level

The brain, the pancreas and the liver are all involved in regulating blood glucose.

Insulin is a hormone which is released by the pancreas in the response to rising blood sugar levels – insulin causes sugars to be stored in the liver in the form of glycogen and this in turn lowers your blood sugar level.

If the body does not produce insulin, or the insulin does not work properly, then this is called diabetes

A balanced diet which includes complex carbohydrates and fibre can help to maintain a steady blood sugar level

This is because complex carbohydrates take longer to digest, so the release of sugar happens over a long period of time – fibre meanwhile cannot be digest and therefore does not affect the concentration of sugar in the blood.

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B7.2 Peak performance – circulation

B7.2 Peak performance – circulation

The HEART is a muscular organ in the circulatory system. It beats automatically, pumping blood around the body to provide cells with oxygen and dissolved food for RESPIRATION.

Humans – and all other mammals – have a double circulatory system which comprises two separate circuits.

Blood pumps through the heart twice during a complete journey around the body – some blood is sent to the lungs and some blood is sent to the rest of the body each time the heart beats.

The blood in each circuit is kept separate – this is called a double circulation and is a more efficient way of delivering oxygen to the tissues than single circulation.

The blood carries glucose molecules and oxygen TO molecules – this is because all cells respire and need a supply of dissolved food and oxygen for this to take place.

The blood then carries AWAY from the cells waste products such as carbon dioxide (taking it back to the lungs so that it can leave the body).

 

 

Blood is a mixture of different components:

  • Plasma – the liquid part of the blood – it transports:

  • Platelets – are tiny particles found in blood plasma – when a blood vessel is damaged, platelets are triggered to clump together to form a clot and prevent blood leaving the body.
  • Red blood cells – transport oxygen from the lungs to the body – they have no nucleus which means they have more space to be packed full with the red pigment haemoglobin, which binds to oxygen to form oxyhaemoglobin

Their biconcave shape increases the surface area for oxygen exchange

The heart is mainly made from muscle with the following features

  • The artia (atriums) are the top chambers of the heart – they collect blood as it flows back to the heart through the veins
  • Two ventricles which are the larger, more muscular lower chambers
  • The vena cava is a larger vein that returns blood from the body into the right atrium
  • The pulmonary arteries (one for each lung transport blood to the lungs. Blood travels from the right ventricle to the lungs – the pulmonary arteries to carry deoxygenated blood
  • The pulmonary vein returns blood from the lungs to the left atrium – it is the only vein that transports oxygenated blood
  • The aorta is the largest artery in the body – taking oxygenated blood at high pressure to the whole body from the left ventricle
  • The coronary artery is a branch of the aorta which transports blood to the heart muscle itself.

The pressures that build up inside the atria and ventricles are very high – valves between each chamber and the arteries leaving the heart, prevent the back flow of blood. Valves are also found in veins in the rest of the body. Blood must only travel in one direction – if it moves back it causes the valve to close.

Blood flows at high pressure from the heart in the artery – the blood reaches its destination via arterioles that branch off the artery and into the capillary beds that surround cells

By the time blood reaches the capillary beds from an artery, it is at high pressure and this forces blood plasma out – the plasma leaves the capillary and becomes tissue fluid.

As the blood plasma moves through the capillary bed towards the vein pressure drops and stops plasma being squeezed out.

 

Tissue fluid acts as a bridge in the diffusion of chemicals between the capillaries and the cells of the tissue.

Oxygen and glucose diffuse from the blood into the tissue fluid and then into the cells.

Carbon dioxide and urea diffuse from the cells into the tissue fluid and then into the blood.

 

 

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B7.1 Peak performance – movement and exercise

B7.1 Peak performance – movement and exercise

Vertebrates are animals that have an internal skeleton – those that do not have an internal skeleton are called invertebrates. In humans and other vertebrates, the skeleton has two functions:

  • Support – the skeleton enables us to stand as well as enclosing important organs for protection e.g. the brain is enclosed by the skull and the ribs enclose and protect the heart and lungs
  • Movement – the skeleton enables complex movement, from standing to sitting and from walking to running

Muscles can only move bones by contracting – so two muscles working in opposition to one another are needed to move an arm up and down, i.e one muscle contracts while the other muscles contracts relaxes – they work in antagonistic pairs.

For example:

  • To lift the lower arm, the biceps contracts and the triceps relaxes
  • To lower the arm, the triceps contracts and the biceps relaxes

 

A joint is where two bones meet and work together – the bones have to be connected in some way that allows them to move also staying in the same place relative to each other. Joints are adapted to allow smooth movement and to resist the effects of wear and tear

The different components serve different functions:

Taken together, the specific properties of each part of a joint enable it to function correctly – if there is a problem with one part, the joint will not work correctly.

Exercise programmes can be put together by doctors, nurses, physiotherapists, personal trainers or other experienced specialists – these exercise regimes can be used to train for a sport or to treat a condition such as obesity.

Before starting a new exercise programme it is important to find out:

  • Current symptoms – may indicate an existing injury
  • Current medication – e.g. use of inhaler – gentle exercise could be better than strenuous exercise
  • Alcohol and tobacco consumption – may affect the cardiovascular and respiratory systems
  • Level of current physical activity – to prevent over-exertion which may cause injury
  • Family medical history – e.g. if heart attack is present in the family history – care should be taken before strenuous exercise
  • Previous treatments – e.g. surgery after a dislocated shoulder may limit the range of movement

This helps to ensure that the exercise regime is effective and safe e.g. it does not make any health problems worse or does not trigger any other ones.

A person’s height and mass can be used to determine their body mass index (BMI) – the BMI is a guideline that helps to identify whether a person is a healthy body mass – it is calculated by the following formula:

The BMI does not take into account the proportion of body fat – a person’s body mass (BMI) and the percentage of their body fat can be used to assess their weigh and fitness

In order to know whether a new training programme has made a positive impact on fitness, it is important to record measurements regularly – these measurements include: blood pressure, resting heart rate, BMI, percentage of body fat, weight lost or gained etc.

Any assessment of progress needs to take into account the accuracy of the monitoring technique and the repeatability of the data obtained.

The human body can withstand a lot of exercise – however excessive exercise (over-exertion or not being properly prepared for exercise) can put the body under a lot of strain, which can lead to injuries including sprains, dislocations and torn ligaments or tendons.

A sprain is where an activity causes a stretch in a ligament beyond its natural capacity – ankles, knees and wrists are all vulnerable to strains.

A sprained ankle can occur when the foot turns inward because this puts extreme tension on the ligaments of the outer ankle

A sprained knee can be the result of a sudden twist

A wrist can be sprained by falling on an outstretched hand

The symptoms of sprains include the following:

  • Swelling – due to fluid building up at the site of the sprain
  • Pain – the joint hurts and may throb
  • Redness and warmth – caused by the increased blood flow to the injured area
  • Being unable to move the joint or put weight on it

When someone suffers a sprain the priority is to reduce swelling and pain and aid rapid recovery and rehabilitation – the treatment follows the principle RICE:

  • Rest – avoid moving the joint which could make the injury worse
  • Ice – carefully cooling the injured joint can help to prevent swelling
  • Compression – a carefully applied support bandage can prevent swelling and support the joint
  • Elevation – raising the injured joint lowers blood pressure in that part of the body and prevents swelling

A physiotherapist is a healthcare professional who specialises in treating people who have skeletal-muscular injuries – physiotherapists understand how the body works and can help a patient to re-train or reuse a part of the body that is not functioning properly. This is normally achieved through various exercises to strengthen muscles that may have become weakened.

 

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