Biology Unit 3 Notes

Osmosis:

• Diffusion/movement of water
• Across a partially permeable membrane
• Along a concentration gradient
• Cell membrane = partially permeable
• Requires no energy

Diffusion:

• Movement/diffusion of particles
• Along a concentration gradient (high to low)
• Requires no energy
• Includes things like glucose, ions, amino acids-not just water

Active Transport:

• Allows cells to take in substances against a concentration gradient
• Uses energy from respiration
• Tansported by transport proteins
• I.E. Glucose can be reabsorbed into kidney tubules using active transport

Sports Drinks:

• Glucose is used in respiration
• Muscles respire during excercise to release energy
• Your body gets too hot and starts to sweat to cool down
• Sweat contains mineral ions and water
• You may become dehydrated if you sweat too much
• Sports drinks are solutions of sugar and mineral ions
• The water in the drinks rehydrates the cells
• The drinks are meant to help the balance of concentration of body fluids
• If the drink concentration matches the body fluids its called Isotonic

Exchanging materials-the lungs:

• Large organisms (eg humans) need special exchange surfaces
• Oxygen is absorbed by the lungs and carbon dioxide is removed from them
• Large surface area, thins walls, short diffusion path and good blood supply are needed
• The lungs contain the gaseous exchange surface
• The surface area is increased by the alveoli
• They have thin walls (1 cell thick), large surface area and good blood supply
• The lungs are ventilated to keep a high diffusion gradient
• Oxygen diffuses into the blood capillaries around the alveoli
• Carbon dixide diffuses back into the lungs to be removed

Ventilating the Lungs:

• Lungs contain exchange surface of breathing system
• Situated above the diaphragm
• When we breathe in: intercostal muscles between ribs and diaphragm contract, ribcage moves up and out, diaphragm flattens, volume of thorax increases, pressure in the thorax decreases and air moves into lungs
• When we breathe out: intercostal muscles relax, ribcage moves down and in, diaphragm becomes domed, volume of thorax decreases, pressure in thorax increases so air is forced out.
• The movement of air in and out of the lungs is called ventilation

Artificial Breathing Aids

• Reasons why people can't get oxygen into their bloodstream: alveoli are damaged so surface area is reduced, tubes leading to the lungs are narrowed so less air can move through them, person is paralysed so their muscles won't pull the ribcage up/down.

Types of breathing aids:

• Iron Lung: The person lay with the chest sealed in the large metal cylinder. When air was drawn out of the cylinder the person's chest moved out and they breathed in. The vacuum which was formed inside the cylinder created a negative pressure. When air was pumped back into the cylinder it created pressure on the chest and forced air out of the persons lungs.
• Breathing aids that force amounts of air into the lungs, they use positive pressure. Bags of air linked to masks can force air down the trachea
• Positive pressure aids are often smaller, easier to manage in the home and can be linked to computers for control

Exchange in the gut:

• Food is digested in the gut -> small, soluble molecules
• These are absorbed in the small intestine
• The villi line the inner surface of the small intestine-they are the exchange surface
• Villi are finger like projections, they increase the surface area for absorbtion
• The walls of the villi are very thin
• There are many capillaries close to the wall
• The solutes can be absorbed by either diffusion or active transport
• They have a good blood supply

Exchange in plants:

• Gases diffuse in/out of the leaves through stomata
• The stomata are controlled by guard cells
• The gases that diffuse are: Oxygen (needed for respiration, waste product of photosynthesis) and Carbon Dioxide (needed for photosynthesis, waste product of respiration)
• Plants also lose water vapour through the stomata due to evaporation in the leaves
• Leaves are flat and thin so the gases dont need to diffuse very far
• Water and mineral ions are absorbed by the roots
• Root hair cells increase the surface area of the roots for the absorbtion
• If the plant loses water faster that it is being replaced, the stomata can close to prevent wilting

Transpiration:

• Plants take up water through the roots
• The water passes through the plant to the leaves & then evaporates
• The movement of the water through the plant is called the transpiration stream
• The plant could dehydrate if the rate of evaporation in the leaves is faster than the water uptake
• The guard cells can close to prevent excessive water loss
• Wilting can reduce water loss as it reduces the surface area

The circulatory system and the heart:

• Humans have a circulatory system that consists of blood vessels, the heart and blood
• The heart is a muscular organ that pumps blood around the body
• The right pump forces deoxygenated blood to the lungs where it picks up oxygen and loses carbon dioxide
• After returning to the heart, the oxygenated blood is then pumped to the rest of the body
• The heart has four chambers
• The upper ones (atria) recieve blood from the vena cava (on the right) and the pulmonary vein (on the left). The atria contract to move blood into the lower chambers (ventricles). When the ventricles contract, they force blood into the pulmonary artery (on the right) and the aorta (on the left)
• The valves in the heart prevent the blood from flowing in the wrong direction
• The heart muscle is supplied with oxygenated blood from the coronary arteries
• The action of the two sides is called double circulation

Keeping the blood flowing:

• There are 3 main types of blood vessel: arteries, veins and capillaries
• Arteries: carry blood away from the heart; have thick walls containing muscle and elastic tissue
• Veins: have thinner walls than arteries; often have valves along the length to prevent the backflow of blood, carry blood into the heart
• Capillaries: are narrow 1 cell thick walls; carry the blood through organs and allow the exchange of substances with all living cells in the body
• If the blood vessels are blocked or too narrow the blood won't flow efficiently and organs will be deprived of nutrients and oxygen
• Stents can be inserted to keep blood vessels open especially when the coronary arteries are blocked due to fatty deposits (i.e. cholesterol) which would cut off the blood to the heart
• Leaky valves could mean the blood could flow in the wrong direction. Artificial/biological (animal) valves can be inserted in the heart to replace damaged valves

Transport in the blood:

• Blood is a tissue. The plasma contains red blood cells, white blood cells and platelets.
• Blood plasma transports many substances: Carbon dioxide (organs to lungs), soluble products of digestion (small intestine to other organs) and urea (from the liver to the kidneys)
• Red blood cells: bi-concave disks; don't have a nucleus; contain the red pigment haemoglobin (which combines with oxygen -> oxyhaemoglobin in the lungs); use the haemoglobin to carry the oxygen to all the organs (then the oxyhaemoglobin splits into oxygen and haemoglobin)
• White blood cells: have a nucleus; form part of the body's defence system against microorganisms
• Platelets: are small fragments of cells; don't have a nucleus; help blood to clot at the site of a wound

Artificial or real:

• Blood from blood donors can be separated into cells and plasma. The plasma can be given to patients in a transfusion to increase blood volume. Donated blood must be refrigerated
• Some blood products can be frozen
• Artificial blood (perfluorocarbons) may be used which does not need to be refreigerated. It doesnt contain cells so blood matching isnt a problem
• Artificial blood is expensive and doesnt carry as much oxygen as whole blood. Some types are insoluble in water so dont mix well with blood and they can cause some side effects
• Patients who suffer heart faliure may need a new heart. The is a lack of heart donors so artificial hearts are being made to keep them alive
• The advantages are that they dont need to match a persons tissue and they dont need immunosuppressant drugs
• The disadvantages are that they a problems with blood clotting, long stays in hospitals and they are expensive

Transport systems in plants:

• Xylem tissue transports water and mineral ions from the roots to the stem, leaves and flowers
• The movement of water from the roots through the xylem and out the leaves is called the transpiration system
• Phloem tissue transports dissolved sugars from the leaves to the rest of the plant, including the growing regions and storage organs

Controlling internal conditions:

• Internal conditions need to be carefully controlled. This is called homeostatis. Temperature, blood glucose, water and ion content and levels of waste products must all be controlled
• Waste products that need to be removed are: carbon dioxide and urea
• Water and ions enter the body when we eat and drink
• If the water or ion content in the body is wrong too much water will move in

The Human Kidney:

• They filter the blood, excreting substances you do not want and keeping the ones you do
• A healthy kidney produces urine by:
• -- Filtering the blood
• -- Reabsorbing all of the sugar
• -- Reabsorbing as much of the dissolved ions that the body needs(selective reabsorbtion)
• -- Reabsorbing as much of the water as the body needs (selective reabsorbtion)
• -- Releasing urea, excess ions and water in the urine
• The urine is temorarily stored in the bladder before being removed from the body
• DIFFUSION AND ACTIVE TRANSPORT

Dialysis - An artificial kidney

• If a person suffers from kidney failiure, they can be kept alive by dialysis
• First, the blood is pumped out of the arm and into the dialysis machine. The blood flows between partially permeable membranes. The dialysis fluid has the same concentration of glucose and mineral ions as the patient's blood does so that these substances don't diffuse out of the blood and need to be reabsorbed. Dialysis fluid has no urea so the urea in the blood diffuses out of the blood into the dialysis fluid. The blood then goes through a bubble trap and the back in to the arm
• The dialysis fliud is moving in the opposite direction to the blood

Kidney Transplants:

• Often a better option than dialysis
• The diseased kidney is replaced with a healthy one
• The new kidney has to be a very good tissue match to prevent rejection
• There are proteins called antigens on the surface of cells. The recipients antibodies may attack the antigens on the donor organ because they recognise the anitgens as being foreign
• Following the transplant the recipient must take immunosuppressant drugs to stop the immune system to prevent rejection
• Despite the advantages of a transplant there are some risks from the operation. Treatment before and after the transplant involves suppressing the immune system which leaves the recipient vulnerable to infections

Treatment and temperature issues:

• The two main treatments are dialysis and kidney failiure
• The doctors have to  consider: the general health of the patient; how long the patient has been on dialysis; the total cost of the treatment (long term costs of dialysis or expensive operation with drugs afterwards); the risks of a transplant operation and the availability of donor kidneys
• There are ethical issues too: should everyone be automatically placed on a transplant register or should they opt in; should people be paid to be donors?; should people pay for a new kidney so they can jump the queue?
• Extreme temperatures can be very dangerous. Small children have a large surface area to volume ratio which means they transfer energy to the surroundings very quickly and can become dehydrated or suffer from hypothermia quickly
• Elderly people suffer from hypothermia in cold consitions because they don't move around to release energy from respiration.

Controlling body temperature:

• Human body temperature must be kept at about 37*C so that the enzymes will worrk efficiently. The core body temperature must be kept stable (homeostatis)
• The body temperature is monitored and controlled by the thermoregulatory center in the brain. This has receptors which detect the temperature of the blood flowing through the brain
• Temperature receptors are also in the skin, they send impulses to the brain to give information about skin temperature
• If the core temperature rises the blood vessels near the skin dilate allowing more blood to flow through the skin capillaries. Energy is trasferred by radiation and the temperature falls. Sweat glands produce more sweat. The water evaporates from the skins surface and we cool down. Also the hairs lie flat
• If the core temperature falls the blood vessels near the skin constrict and less blood flows through the skin capillaries so less energy is radiated. We shiver, which means the muscles contract quickly. This requires respiration and some of the energy released warms the blood. Also the hairs are pulled erect to trap an insulating layer of air

Controlling blood glucose:

• The pancreas moniter and controls the level of glucose in our blood
• If there is too much glucose in our blood the pancreas produces the hormone insulin
• Insulin causes the glucose to move from the blood into the body cells
• In the liver, excess glucose is converted into glycogen for storage
• If none or too little insulin is being produced the blood glucose level can get too high (Type 1 diabetes)
• Type 1 diabetes is controlled by injections of insulin and careful attention to diet/excercise
• Insulin causes the blood glucose level to fall
• If the levels get too low, receptors in the pancreas detect it and releases glucagon (hormone). The glucagon causes the glycogen in the liver to change into glucose and the glucose gets released back into the blood to restore the blood glucose level to the right level

Treating diabetes:

• Type 1 diabetes is normally treated with human insulin produced by genetically engineered bacteria
• The person has to inject before every meal for the rest of their lives
• Very active diabetics have to match the amount of insulin injected with their diet and excercise
• Some diabetics use pumps attached to the body. They can adjust the level of insulin injected by the pump
• Doctors and other scientists are trying to develop new methods of treating and maybe curing Type 1 diabetes:
• pancreas transplants
• transplanting pancreas cells
• using embryonic stem cells to produce insulin secreating cells
• using adult stem cells from diabetic patients
• genetically engineering pancreas cells to make them work properly

The effects of the population explosion

• The world population is about 7 billion
• Many people want and demand a better standard of living
• We are using up raw materials and many non-renewable ones
• When goods are produced there is a lot of industrial waste
• We are producing lots of pollution and waste
• Humans reduce the amount of land for animals and plants by building, quarrying, farming and dumping waste
• This is affecting the ecology of the Earth
• Humans pollute: waterways with sewage and fertiliser and toxic chemicals; air with smoke and gases such as sulfur dioxide; land with toxic chemicals such as pesticides and herbicides and these can be washed into water

Land and water pollution:

• Sewage contains human body waste and waste water from our homes. Sewage must be treated properly to get rid of gut parasites and toxic chemicals so they dont get on the land
• Large quantities of household and industrial waste are placed in landfill and toxic chemicals leak out. Some industrial waste such as radioactive waste is very hazardous
• Farming methods can pollute the land: herbicides and pesticides are also poisons and they can get into food chains and rivers
• Water pollution: herbicides, pesticides and chemical fertilisers all get washed into river and streams; fertilisers and untreated sewage can cause a high level of nitrates in to the water; toxic chemicals from landfill also leak into the waterways and pollute the water, killing organisms such as fish

Air pollution:

• Burning fuels can produce sulfur dioxide and other acidic gases. Power stations and cars release acidic gases
• The sulfur dioxide dissolves in water in the air and then falls as acid rain
• Acid rain kills organisms. Trees can be damaged if the leaves are soaked in acid rain for long periods
• Acid rain can change the soil pH, which damages roots and may release toxic minerals. I.e. aluminium ions are released which also damages organisms in the soil and waterways
• Enzymes are very sensitive to pH
• When trees are damaged, food and habitats for other organisms are lost

Deforestation and peat destruction:

• Due to the need of timber and land for farming, large scale deforestation is needed
• Normally in tropical rainforests (like the Amazon)
• Deforestation has: increased the release of carbon dioxide because of thee burning/decay/respiration of microorganisms; reduced the rate that carbon dioxide is being removed by photosynthesis; reduced the biodivesity due to loss of food and habitats
• Deforestation has occurred so that: crops can be grown to produce ethanol-based biofuels; there can be an increase in cattle and rice fields for food
• Cattle and rice produce methane, so methane levels have risen in the atmosphere
• The destruction of peat bogs also results in the release of carbon dioxide because the peat is either burnt for fuel or used as compost so microorganisms respire whilst they are decaying it
• Using peat-free composts means that peat bogs will not be destroyed

Global warming:

• Normally carbon dioxide is released into the atmosphere by respiration and removed by plants and algae in photosynthesis
• Carbon dioxide also dissolves in oceans, rivers, lakes and ponds
• This is known as carbon dioxide being sequestered by plants and water
• Levels of carbon dioxide and methane are increasing. They are called greenhouse gases and contribute to the greenhouse effect. This causes global warming
• An increase in the Earths temperature may: cause big changes in the Earths climate; cause a rise in sea level due to the melting of ice caps and glaciers; reduce biodiversity; cause changes in migration patterns; result in changes in the distribution of species

Biofuels:

• Biofuels are made from natural products
• The two types of biofuels are ethonal-based fuels and biogas
• Ethanol-based fuels can be produced by fermentation
• Microorganisms respire anaerobically to produce the ethanol, using sugars from the corps as the energy source
• Glucose is produced from maize starch by the action of a carbohydrase
• The glucose and sugar cane juices can be fermented by yeast to produce ethanol
• The ethanol is extracted by the process of distillation and can then be used as a fuel in motor vehicles
• Using ethanol as a fuel could replace fossil fuels in the future. In terms of the greenhouse effect, using ethanol as a fuel is much more carbon friendly
• Ethanol is described as carbon neutral because only the carbon dioxide used for photosynthesis by the crops is returned to the atmosphere when the ethanols is burned

Biogas:

• Biogas is mainly methane. It can be produced during anaerobic fermentation by bacteria
• Plants and any waste materials containing carbohydrate (cattle dung) can be broken down in biogas generators
• The generators provide the ideal conditions for bacteria to reproduce and ferment the carbohydrase. They must be maintained at a suitable temperature in oxygen free conditions. Some generators are designed to mix the contents. Generators are eiter buried in the ground for insulation or have insulating jackets
• Large scale generators can use waste from sugar factories or sewage works
• Smale scale generators can be used by a home or farm
• The gas produced is a fuel and provides energy for heating. The more methane in the gas mixture, the better the quality of the gas

Making food production efficient:

• The shorter the food chain, the less energy will be wasted so therefore it is more efficient for us to eat plants than it is to eat animals
• We can produce meat more quickly by: preventing the animal from moving so it doesn't waste energy on movement, and keeping the animal in warm sheds so it doesn't use as much energy from food to maintain its body temperature

Sustainable food production:

• Sustainable food production involves managing resources and finding new types of food such as mycroprotein.
• Fish stocks in the oceans are monitered. Fishermen can only remove a strict quota of fish per year and must use certain sized nets to avoid catching small young fish
• The fungus fusarium is grown to produce mycroprotein. This is a protein rich food suitable for vegetarians. Fusarium is grown aerobically on cheap sugar syrup made from waste starch and the mycroprotein is harvested.
• Microprotein is grown in large scale fermenters. The conditions in a fermenter must be controlled to ensure maximum growth of the fusarium
• Industrial fermenters have: an air supply providing oxygenfor respiration; a stirrer used to keep the microorganisms spread out and to provide an even temperature (agitate); a water cooler around the outside and sensors to monitor both pH and temperature