Osmosis is the diffusion of water
Water diffuses from a dilute solution to a more concentrated solution through a partially permeable membrane.
Water moves into / out of cells by osmosis through the cell membrane. The cell membrane is partially permeable.
Active Transport - Transport process that is used to move dissolved molecules from an area of low concentration to an area of high concentration.
Active transport allows cells to take in substances, e.g. glucose
Active transport goes against the concentration gradient.
Active transport relies on energy from respiration.
Cells are able to absorb ions from dilute solutions, and other substances like sugar by active transport.
Glucose can be reabsorbed in the kidney tubles by active transport.
In plants, when mineral ions are brought in by active transport, the rate of respiration increases. This is because, for active transport to happen, we need energy, and when we require energy, we require respiration.
The Sports Drink Dilema
Sports drinks are solutions of sugar and mineral ions.
Most soft drinks contain:
* Water to replace water lost by sweating
* Sugar to replace sugar lost/used for energy release in exercise
* Mineral ions to replace those lost in sweating
For normal levels of exercise, water is likely to be as effective as a sports drink.
Water is only able to rehydrate the body. It does not replace lost ions and glucose.
Gaseous Exchange - The exchange of Oxygen and Carbon Dioxide between the blood and the air in the lungs.
Structure: Thorax, Diaphragm (muscle which separates the thorax and the abdomen), Abdomen. The lungs are surrounded by the ribcage which protects them. Between the lungs are the Intercostal Muscles which help ventilate the lungs.
Breathing in and out removes waste Carbon Dioxide produced by the cells and adds Oxygen for respiration in the blood.
The lungs are adapted to be an efficient exchange surface; Large surface area (increased by the Alveoli), Very thin walls (short diffusion distance), Rich blood supply (maintains concentration gradient, Moist lining.
Inhlation / Exhilation
* Intercostal muscles CONTRACT / RELAX
* Ribs move UP and OUT / DOWN and IN
* Diagragm muscle CONTRACTS and MOVES DOWN / RELAXES and MOVES UP
* Volume in thorax INCREASES / DECREASES
* Preassure DECREASES / INCREASES
* Air rushes IN / OUT
Artificial Breathing Aids
Negative pressure - The Iron Lung
+ Keeps patient alive
+ Breathes for the patient
- Patient has to lie inside a large machine
- Doesn't work as well as positive pressure breathing systems
Positive Pressure - Ventilation Bag
+ Quick and easy to use
+ Machine based systems can be portable and can be used for extended periods
+ Only the face is covered
> Alviolus - Carries out the exchange of carbon dioxide and oxygen with the air.
- Rich Blood Supply: Produces a steep concentration gradient for efficient diffusion.
- Large Surface Area: For diffusion.
- Thin Walls: Short distance for diffusion.
> Villi - Finger-like projections of the lining of the small intestine. They are an efficient echange surface for the absorbtion of the soluble products of digestion by diffusion or active transport.
- Rich Blood Supply: Produces a steep concentration gradient for efficient diffusion.
- Large Surface Area: For diffusion.
- Thin Walls: Short distance for diffusion.
In humans, Active transport takes place during the digestion of food in the small intestine. Carbohydrates are broken down into simple sugars like glucose. The glucose is absorbed by active transport into the villi, to be passed into the blood stream.
Exchange Systems in Plants
Carbon Dioxide difuses into the leaf (throught the stomata), as it is required for photosynthesis.
Oxygen duffuses out of the leaf, as a bi-product of photosynthesis.
Water and mineral ions travel into the plant through the roots. The roots increase their surface area by root hair cells
Leaves are very flat and thin with internal air spaces to increase the surface area for the diffusion of gases. Being thin reduces the distance for diffusion.
Plants lose water vapour through the stomata due to evaporation in the leaves.
Transpiration and Water Loss
Transpiration - The evaporation of water from the leaves
Evaporation is more rapid in hot and dry conditions. This is because there is low humidity. In windy conditions, the particles are being moved away from the surface of the leaves, so this also increases the rate of evaporation.
If the rate of evaporation is rapid, and there is not enough water in the soil, the plant could wilt. This can protect the leaf from excessive water loss. The leaves colapse and hang down which reduces the surface area.
Guard cells open and close the stomata, depending on the conditions. When the stomata are closed, it reduces the amount of water that is lost.
Cobalt Chloride paper can be used to indicate whether water has evaporated from the leaf. The paper starts off blue, but when water is present, it turns pink.
To use it in an experiment, we place a small piece into a plastic bag, and seal the bag around a leaf. We then measure the time it takes for the leaf to turn the cobalt chloride paper pink.
By using this experiment, we can see how different conditins affect the rate of evaporation of water from a leaf.
Conditions which increase the rate of evaporation will increase the rate of transpiration.
The Heart - Coronary Arteies
The main point of the heart is to pump blood around the body.
The walls of the heart consist of a lot of mucsle. The coronary arteries are situated inside the muscle and supply the heart with the blood it needs which contains the sugars and the oxygen which give it the fuel in order to keep on pumping.
If we ever have a problem with the coronary arteries, this can lead to a heart attack. Sometimes, heart disease causes blockages in the coronary arteries. This reduces blood flow to the heart and can be quite dangerous.
A stent is a wire mesh in the shape of a tube and is used to open up a narrowed or blocked artery. The stent is inserted into the artery, and then is opened up using a balloon. It causes the artery to be much wider and restores blood flow the the muscle, strengthening the heart.
The Structure of the Heart
* Pulmonary Artery, Vena Cava, Atrium, Valve, Ventricle
* Aorta, Pulmonary Vein, Atrium, Valve, Ventricle
The Heart and Circulation
1) The atria fill up with blood
2) The atria contract and force blood downwards into ventricles
3) The ventricles contract and force blood out of two main blood vessels to various parts of the body
4) Valves in the heart make sure that blood flows in the right direction. The valves are like a one-way door; they allow blood to flow in one direction, but then close to prevent it from flowing backwards.
The Circulatory System
Double Circulation - The separate circulation of the blood from the heart to the lungs and then back to the heart and on to the rest of the body.
- The Pulmonary Artery carries blood from the heart to the lungs, and the Pulmonary Vein carries the blood from the lungs back to the heart.
- The Aorta carries blood away from the heart to the rest of the body, and the Vena Cava brings blood from around the rest of the body back to the heart.
The blood on the left side of the heart oxygenated as it's carrying oxygen, and the blood on the right side is deoxygenated as it has much lower levels of oxygen.
Keeping the Blood Flowing
- Carry blood away from the heart
- Have thick walls to resist the high pressure of blood (contain muscles and elastic tissue)
- Carry blood to the heart
- Have thin walls as blood with low pressure flows through them
- Often have valves in them to prevent the backflow of blood
- Narrow, thin-walled vessels
- Carry the blood through the organs and allow the exchange of sunstances with all the living cells in the body. Substances diffuse between the blood and the cells in the capilaries.
Plasma is the fluid part of the blood. It transports hormones and carries Carbon Dioxide and waste products away from the cells. It also contains blood cells.
Red Blood Cells - Transport oxygen
- They have no nucleus as it provides more space to carry haemoglobin, and are manufactured in bone marrow. Once haemoblobin is exposed to oxygen in the lungs, we have oxyhaemoglobin. When the RBCs travel around the body, oxygen is released to body cells, and it becomes haemoglobin again.
White Blood Cells - Form part of the body's defence system against microorganisms.
Platelets - Help the blood to clot at the site of a wound.
- They are small fragments of cells, without a nucleus.
- Soluble products of digestion are transported from the small intestine to the other parts of the body via the blood plasma.
- Urea is transported from the liver to the kidneys by the plasma, where it will be removed in urine.
Artificial Blood and Hearts
Artificial Blood - Used when there is a loss of blood (surgery)
+ Doesn't contain cells so blood matching is not necessary
+ It is always available
- Can cause unpleasant side effects
- Doesn't mix asily with the blood
Artificial Hearts - These are used when donor hearts are not available, as there is a lack of them. They replicate the function of the heart, but are only used as a short term measure to keep patients alive.
+ Don't need to match patient's tissue, keeps patients alive
- Prone to blood clotting within them, expensive, require long stays in hospital
Transport Systems in Plants
Plants have two transport systems to move food, water and minerals through their roots, stems and leaves.
In the stem and roots of a plant, their are vascular bundles containing cells called Xylem and Phloem. In the stem, the phloem is is on the outside of the oval shaped structure in the centre,, whereas the xylem is on the inside of the structure. In the roots, the phloem is the small circular shapes, and the xylem is the 'x' shape in the centre.
* Made of Living cells. Transports sugars that are made from photosynthesis in the leaf. The substances can be transported around the plant, either towards growing regions (for energy) or storage areas.
* Made of Dead cells. Transports water and minerals from the soil around the plant. The water is required for photosynthesis and also the fact that cells are packed with water makes them turgid and they can support the plant. The minerals are used for healthy growth. These are transported up the plant, through the xylem.
Transpiration Stream = (Soil --->) Roots ---> Xylem ---> Leaves ---> Evaporation - This is the pathway that the water takes
Waste products must be removed from the cells.
Internal conditions in the body must be kept constant.
Temperature, blood, glucose, water and ion content must be controlled.
* Carbon Dioxide - A product of aerobic respiration. Removed via the lungs when breathing out.
* Urea - Made in the liver from the breakdown of amino acids. The kidneys remove it from the blood stream and make urine.
* Temperature - Increased by shivering ---> Lost by sweating
* Ion Content - Increased by eating ---> Lost by sweating and in urine
* Water Content -Increased by drinking ---> Lost by sweating and in urine
* Blood Glucose - Increased and decreased by hormones
The body has two kidneys. They filter the blood by excreting substances you do not want and keeping those that the body needs.
A Healthy Kidney works by: Filtering the blood as it goes into the kidney, and them removing it once it has been filtered. Any waste products removed from the blood are then removed through urine.
How do your Kidneys work?
* The blood is filtered so glucose, mineral ions, amino acids, urea and water diffuse into the kidney tubules.
* Everything the body needs is reabsorbed. All the glucose, and amino acids are reabsorbed, and the mineral ions and water are selectively reabsorbed depending on your body's needs.
* Urea and excess water and ions are realesd as urine, to the bladder, where it is stored temporarily before being removed from the body.
A kidney transplant is an alternative method for treating renal failure. The diseased kidney is replaced with that of a donor kidney.
+ No more dialysis
+ Extends life
+ No need to control diet
- Need to find a donor with a tissue match
- Rejection of kidney
- Need to take drugs (immunosupressants)
l---> This makes you prone to illness as your immune system has been suppressed.
The kidneys remove urea and excess ions and water from the blood. If the kidneys don't work, then these waste products can build up in the body and over a period of time that can cause illness or even lead to death.
If a person sufferes from kidney failure, they can be kept alive by dialysis. A dialysis machine carries out the same job as the kidneys.
In a dialysis machine, a person's blood flows between partially permeable dialysis membranes. The dialysate contains the same concentration of useful substances as the blood. This ensures that glucose and useful mineral ions are not lost. Urea diffuses out from the blood into the dialysate. The blood flows down the the machine, and the dialysate flows up.
The blood becomes cleaneras salts and urea move down the concentration gradient. Blood cells are unable to pass throught the dialysis membrane.
Dialysis restores the concentration of substances in the blood back to normal, but needs to be carried out at regular intervals.
The Advantages and Disadvantages of Dialysis
+ More available than donor kidneys
+ No need to take drugs
+ No need for surgery
- Multiple sessions a week (2-3 times)
- Long sessions (4-8 hours)
- Less freedom (holidays/trips/careers)
- Need to follow a specific diet
Controlling Body Temperature
Blood carries heat around the body. The normal human body temperature = 37*C . Body temperature is monitored and controlled by the thermoregulatory centre in the brain. Also, temperature receptors in the skin send impulses to the thermoregulatory centre, giving information about skin temperature.
Sweating helps to cool the body. More water is lost when it's hot so more has to be taken in from food or drink to balance this loss. This may also lead to less urine.
When the Body is too Hot:
* Vasodilation - Blood vessels supplying the skin cappilaries dialate. More blood flows through the capillaries so more heat is lost by radiation. This results in the skin looking red.
* Sweat glands release more sweat. The water in the sweat evaporates, carrying heat energy away, and cooling the skin.
When the Body gets too Cold:
* Vasoconstriction - Blood vessels supplying the skin cappilaries constrict. Less blood flows through the cappilaries so less radiation of heat energy. This results in the skin looking pale.
* Shivering - Muscles contract and relax involuntarily in an attempt to warm up. Some heat energy is releases as contraction of muscles requires respiration.
Control of Blood Glucose
Glucose is needed to provide energy for the body (respiration).
If the levels of glucose in the body get too high or too low, it can be dangerous.
Too High: Thirst, Hunger, Need to Urinate, Blurred Vision, Dizziness, Nausea.
Too Low: Hunger, Weakness, Inabillity to Concentrate, Dizziness, Convulsions, Unconsious
The pancrease secretes insulin into the blood to allow glucose to enter the cells. It also converts glucose (solubel) into glycogen (insoluble). When glucose levels are low, less insulin is released. Insulin is a hormone, made from proteins.
Type 1 Diabetes
* Pancreas make too little insulin. This means that glucose cannot enter cells, and cannot be converted to glycogen for storage in the liver.
* Type 1 Diabetes can be treated with insulin injections throughout the day, along with attention to diet and exercise.
How the Body Responds to Blood Glucose Levels
When the Blood Glucose Levels are too High:
* Too much glucose in blood
* Pancreas produces insulin which enters the blood
* Insulin allows glucose to be absorbed by body cells
* Blood glucose is reduced
When the Blood Glucose Levels are too Low: Blood glucose levels can be lowered by not eating or exercise. The hormone glucagon is released from the pancreas and converts glycogen back to glucose
* Too little insulin in blood
* Insulin not produced by the pancreas
* Less glucose absorbed by body cells
* Blood glucose increased
Human Population Growth
The human population is growing rapidly. We are using more resources and producing more waste and pollution. Unless waste is handled properly, more pollution will be created.
Water Pollution: Sewage, Fertiliser, Toxic Chemicals
Air Pollution: Smoke, Gases (sulpher dioxide - dissolves in rain water and produces acid rain, CO2)
Land Pollution: Toxic Chemicals, Pesticides, Herbicides
Humans reduce the amount of land available for other animals and plants, by building, farming, quarrying and dumping waste. All of this reduces biodiversity in the environment.
Disposing of Solid Waste:
* Landfill sites, Composting
* Incineration - + Reduces volume, - Produces toxic fumes
* Recycling - + Reduces the need for raw materials
Deforestation - The destruction/removal of areas of forest.
* Reduces the amount of Carbon Dioxide taken in from the air, as carbon sink stores are being removed.
* Vegetation cycle adds CO2 to the air, as does the burning of trees.
* Reduces biodiversity / Destroys habitats
Deforestation has occured so that:
- Crops can be grown
- Biofuels can be produced
Methane is produced from rice fields, as well as farm animals such as cows.
Peat bogs are areas of partially decayed plant material (marshy ground). They can be burned as fuels and used to improve the quality of soil. It releases Carbon Dioxide.
A rise in Carbon Dioxide and Methane levels could lead to global warming, and this could cause:
- Climate Change
- Rises in Sea Levels
- Change in Species Distribution
- Change in Bird Migration Patterns
A lot of Carbon Dioxide has been dissolved in oceans, lakes and ponds, and we say it has been Sequestered.
How is Global Warming created?
1) Heat from the sun enters the atmosphere and warms the Earth's surface.
2) The Earth's surface becomes hotter and radiates more heat out.
3) Some of the heat is absorbed by greenhouse gases. These gases then radiate the heat back towards Earth.
4) The Earth then becomes warmer.
Biofuels are fuels comprised of organic matter, available on a renewable / reccuring basis.
Biofuels can be produced by anaerobic fermentation of sugars from plants
l---> The ethanol distilled from the fermentation product can be used as fuel in motor vehicles.
Ethanol is made from crops by anaerobic fermentation.
The Advantages and Disadvantages of Biofuels:
+ Reduces ai pollution
+ Reduces greenhouse gas emmisions
- Land has deen deforested
- Plants aren't used for food
Biogas Production is a way of generating a fuel that can be used for many things: Cooking, Heating, Fuel, Electricity Production. Furthermore, when the substances have been broken down by bacteria, the remaining substance is a good fertiliser, so can be used to fertilise soil.
How Biogas is Produced:
- Waste food, plants, animal waste and human waste goes in to the biogas generator. In here, a substance called 'slurry' is produced. It is important that the generator has anaerobic conditions and is kept at a warm temperature (30*C). It is important that no oxygen is present so we can grow a certain type of bacteria that produces the biogas. We call this Anaerobic Fermentation.
- The biogas is under pressure in the tank, and the tank is made so that no air can get in. If no air can get in, the pressure can build up and when the biogas is ready, it can be pushed out.
- The process is exothermic, but keeping the generator underground provides insulation.
The gases present in Biogas include: Methane (80%), Carbon Dioxide (10-15%), Water Vapour, Hydrgen, Hydrogen Sulfide.
In many countries, giant anaerobic fermenters have been built to produce large amounts of fuel, as it more environmentally friendly than fossil fuels.
Food Production: The Efficiency of Food Chains
Food production is important as the human population is increasing. Plants and Animals are the main sources of food for humans.
When animals eat plants, they use the biomass (energy content) for itself. The energy is used for movement, heat production, growth, faeces and waste material. The entire mass of the product is not passed on, therefore the human will get less enrgy than the animal did.
If a human was to eat the plant first, skipping a stage in the food chain, then all of the biomass and energy content would be available to the human. We say that the food chain is more efficient.
Humans now try to reduce the amount of energy used by the animals. Thsi has led to a process known as factory farming. The movement of animals is restricted, and we heat the environment, which means less energy is used for movement and heat, and more can be used for growth.
Free Range / Organic
Free Range animals are kept in less cruel conditions, and are lft to live in large open spaces (fields). Thsi means that more energy goes to movement and heat, and less goes to growth, therefore they will take longer to grow.
Food Production: Fishing
Fishing provides a lot of food for people, but there are problems in that humans are reducing the number of edible fish stocks drastically. Some breeds are endangered and may possibly become extinct.
A number of regulations are put in place in order to make sure fish stocks are preserved:
* Net Size (smaller net sizes means we catch less fish)
* Quotas (having a number limiting the amount we're allowed to catch)
* Avoiding fishing during mating season (this allows fish to reproduce and replenish stocks)
* Avoiding fish breeding grounds ( so that the fish are free to reproduce)
* Mesh size (the size of the wholes in the nets. Allows fish to grow to get bigger and reproduce)
Unfortunately, it hard to monitor all of the regulations.
Food Production: Mycoprotein
Mycoprotein comes from a type of fungus that is very high in protein and very low in fat. It is called Fusarium. It contains lots of different kinds of amino acids that make proteins, but are very low in fat, therefore some people view it as a healthy product, and an ideal substitute for meat. It is grown in aerobic conditions.
How it is Produced:
Oxygen is provided from air. Air goes into a fermentation vessel and bubbles through the mixture, providing oxygen. There is a filter at the entrance to prevent any bacteria from getting in, as, if this occured, it could contaminate the mixture. The air also has the job of mixing all the glucose syrup and minerals and the fungus that are in there, and also distributing the heat that's generated in there. After a period of time, the mycoprotein is released at another point in the fermentation vessel. The aerobic respiration produces Carbon Dioxide, so that can escape at the top of the F/V. As the aerobic respiration produces a great amount of heat, if it goes above 35-37*, it could slow the growth of the Fusarium fungus. As we don't want this to happen, we have a solution for keeping the F/V cool; a cooling water jacket is kept on the outside of the main part where the fermentation process is happening, ad a stream of cold water is constanly flowing. The end product of Mycoprotein is sterilised, to desroy any bacteria.
Food Production Evaluation
+ Faster growth + Cheaper + More Food
- Diseases spread - Cruelty (poor conditions)
+ Less cruelty + Growth in natural conditions
- More food - More expensive - Longer to grow
(local food) + Less travel, less CO2 emmisions + Less affect on global warming
- Weather: less availablity in winter - Greenhouses: heat/light produces CO2