Riassunto capitoli da 12 a 22 di CAMBRIDGE IGCSE BIOLOGY; Summary of cap 12-22 Biology, Sintesi del corso di Biologia

Scarica Riassunto capitoli da 12 a 22 di CAMBRIDGE IGCSE BIOLOGY; Summary of cap 12-22 Biology e più Sintesi del corso in PDF di Biologia solo su Docsity! CAP 1: CLASSIFICATION Biology is the study of living things, called organisms. Living organisms have 7 features: - Movement = an action by an organism causing a change of position or place; - Respiration = the chemical reactions in the cells that break down nutrient molecules and release energy; - Sensitivity = the ability to detect and respond to changes in the environment; - Growth = a permanent increase in size; - Reproduction = the processes that make more of the same kind of organism; - Excretion = removal from organisms of toxic materials and substances in excess of requirements; - Nutrition = taking in of materials for energy, growth and development. Furthermore, living organisms are all made of cells, which have: - cytoplasm; - a cell membrane; - a chemical called DNA, for the genetic material; - ribosomes, which make proteins; - enzymes, which help the cell to carry out anaerobic respiration. Classifications means putting things into groups. Living things are classified to make it easier to study them. The group of mammals shares certain features that are different from other groups. This is because all mammals have descended from a common ancestor. DNA in classification To decide which organisms are most closely related to each other, we looked at their morphology (form and shape of the body) and their anatomy (body structure). Today we can also study the DNA, the chemical from which our chromosomes are made. The genetic material passes from one generation to the next. It contains 4 different bases: A, C, G, T, that can be arranged in any order. The more similar the base sequences, the more closely related are the species. Classification system All the different kinds of living things are divided into species (that are 12000) —> genera (genus) —> families —> orders —> classes —> phyla —> kingdoms. Species: a group of organisms that can reproduce and produce fertile offspring. The binomial naming system Every living organism has two names, written in Latin. The first name is the one of its genus and has a capital letter. The second name is the one of its species and has a small letter. This two-word name is called a binomial. Animals Characteristics: - multicellular; - cells have a nucleus, but no cell walls or chloroplasts; - feed on organic substances made by other living organisms. Plants Plants have leaves, stems, roots and flowers. They have in common the green color, caused by a pigment = chlorophyll. It absorbs energy from sunlight, and the plant uses this energy to make sugars, by the process of photosynthesis. They don’t need to move but remain in one place. Their shape is spreading to capture as much sunlight energy as possible. Characteristics: - multicellular; - cells have a nucleus, cell walls made of cellulose, and often chloroplasts; - feed by photosynthesis; Fungi We eat them as mushrooms; we use the fungus yeast to make ethanol and bread; we obtain antibiotics from fungi. But some fungi are harmful, they can cause food decay or diseases. Characteristics: - usually multicellular; - have nuclei, cell walls not made of cellulose; - do not have chlorophyll; - feed by saprophytic nutrition (dead plants or animals) or parasitic nutrition. Protoctista This kingdom contains a mixture of organisms. Characteristics: - multicellular or unicellular; - cells have a nucleus, may or may not have a cell wall and chloroplasts; - some feed by photosynthesis and some feed on organic substances made by other organisms. Prokaryotes They are bacteria, with cells very different from other kinds of organisms. Some of them are harmful, they cause diseases such as tuberculosis and cholera. Others are helpful, they have a useful role in the carbon cycle and the nitrogen cycle, in the treatment of sewage and in making insulin. Characteristics: - often unicellular; - have no nucleus , have cell walls not made of cellulose; - have no mitochondria; - some bacteria carry out photosynthesis. Viruses Viruses cause common diseases like colds and influenza, or more serious ones such as AIDS. They are not considered to be alive. After they get inside a living cell, they take over the cell's machinery to make multiple copies of themselves. These new viruses burst out of the cell and invade others, where the process is repeated. The host cell is usually killed when this happens. They are not made of a cell, but simply a piece of DNA or RNA surrounded by a protein coat. Phylum vertebrates These are animals with a supporting rod running along the length of the body. The most familiar ones have a backbone and are called vertebrates. Class Fish The fish all live in water, except the mudskipper, which can spend short periods of time breathing air. Characteristics: • scaly skin; • have gills; • have fins. Class Amphibians Most adult amphibians live on land, but they go back to the water to breed. Frogs, toads and salamanders are amphibians. Characteristics: • moist, scale-less skin; • eggs laid in water, larva lives in water; • adult often lives on land; • larva has gills, adult has lungs. Cell wall helps to protect and support the cell. It's said to be fully permeable because even large molecules can pass through it. Cytoplasm Cytoplasm is a clear jelly, made up of water at 70%. It contains many substances dissolved in it, especially proteins. Many different metabolic reactions take place in the cytoplasm. Vacuoles It's a space in a cell, surrounded by a membrane and containing a solution. Plant cells have large vacuoles called cell sap. A full vacuole presses outwards on the rest of the cell and helps to keep it in shape. Animal cells have much smaller membrane-bound spaces, called vesicles, which contain food or water. Chloroplasts They are found only in plant cells, and they contain chlorophyll. It absorbs energy from the sunlight and this energy is used for making food for the plant by photosynthesis. Chloroplasts often contain starch grains, made by photosynthesis. Animal cells instead have tiny grains (granules) of a substance similar to starch, called glycogen. Nucleus Here the genetic information is stored. In this way the cell can make the right sorts of protein. The information is kept on the chromosomes, made of DNA. They are long and thin; when the cell is dividing, they become short and thick. Mitochondria They are found in almost all cells, except those of prokaryotes. They are the powerhouses of the cell: inside them, oxygen is used to release energy from glucose by the process called anaerobic respiration. So cells that use a lot of energy, like muscle cells, have a lot of mitochondria. Glycogen is a reserve fuel because it can be broken down to glucose. Ribosomes They are like tiny dots attached to a network of membranes that runs throughout the cytoplasm —> rough endoplasmic reticulum. Ribosomes are found in all types of cells. They are the places where proteins are made, by joining amino acids together in a long chain. Cells and organisms Not all the cells are alike, they are all specialized in doing something. Tissue A group of cells with similar structures, specialized in the same activity, working together to perform a shared function. Organ A structure made up of a group of tissues, working together to perform specific functions. Organs system A group of organs with related functions, working together to perform body functions. All organ systems make up organisms. CHAP 3: MOVEMENT IN AND OUT OF CELLS DIFFUSION Atoms, molecules and ions are always moving. The higher the temperature, the faster they move. In a solid substance the particles cannot move very far, since they are held together by attractive forces between them. In a liquid they can move more freely, in a gas they are freer still, with no attractive forces between the molecules or atoms. Molecules and ions can also move freely when they are in solution. DIFFUSION AND LIVING ORGANISMS Living organisms obtain many of their requirements by diffusion. They also get rid of many of their waste products in this way. Plants need carbon dioxide. This diffuses from the air into the leaves, through the stomata.There is a lower concentration of carbon dioxide inside the leaf. Carbon dioxide diffuses into the leaf, down this concentration gradient. Oxygen, a waste product, diffuses out in the same way, through the stomata; there's a higher concentration of it inside the leaf since it’s made there. Diffusion is also important in gas exchange for respiration in animals and plants. Cell membranes are freely permeable to oxygen and carbon dioxide, so these easily diffuse into and out of cells. OSMOSIS Water acts as a solvent for many substances. Every cell in an organism's body has water inside it and outside it. Various substances are dissolved in this water, and their concentrations may be different inside and outside the cell. This creates concentration gradients, down which water and solutes will diffuse, if they are able to pass through the membrane. A sugar solution is separated from a diluted one by a membrane, that has holes or pores (ex: Visking tubing). Each molecule of water is made up of 2 hydrogen atoms and 1 oxygen atom. Sugar molecules are many times larger than this. In Visking tubing, the holes are big enough to let the water molecules through, but not the sugar molecules,so it is called a partially permeable membrane because it will let some molecules through but not others. There is a higher concentration of sugar molecules on the right-hand side, and a lower on the left-hand side. If the membrane was not there, the sugar molecules would diffuse from the concentrated solution into the dilute one until they were evenly spread out.There is a concentration gradient for the water molecules. On the left-hand side of the membrane, there is a high concentration of water molecules. On the right-hand side, the concentration of water molecules is lower because a lot of space is taken up by sugar molecules. There are more water molecules on the left hand side, at any one moment more of them will hit a hole in the membrane and move through to the other side than will go the other way. Over time, there will be an overall movement of water from left to right. This is called osmosis, just a kind of diffusion. It is the diffusion of water molecules, in a situation where the term concentration is normally used to mean the concentration of the solute dissolved in the water. We say that a dilute solution has a high water potential. A concentrated solution has a low water potential. There is a water potential gradient between the two sides. CELL MEMBRANES Cell membranes let some substances pass through them, but are partially permeable membranes. There is always cytoplasm on one side of any cell membrane, a solution of proteins and other substances in water. There is usually a solution on the other side of the membrane, too. OSMOSIS AND ANIMAL CELL The cytoplasm inside the cell is a fairly concentrated solution. The proteins and many other substances dissolved in it are too large to get through the cell membrane. Water molecules can get through. The concentrated solution is the cytoplasm and the partially permeable membrane is the cell membrane. Water molecules will diffuse from the dilute solution into the concentrated solution. As more and more water enters the cell it swells. F lo The cell membrane has to stretch as the cell gets bigger, until eventually the strain is too much, and the cell bursts. If this solution is more concentrated than the cytoplasm, then water molecules will diffuse out of the cell. As the water molecules go out through the cell membrane, the cytoplasm shrinks. The cell shrivels up. OSMOSIS AND PLANT CELL Plant cells do not burst in pure water. Plant cells are surrounded by a cell wall, fully permeable,that will let any molecules go through it.A plant cell also has a cell surface membrane just like an animal cell. The cell membrane is partially permeable. A plant cell in pure water will take in water by osmosis through its partially permeable cell membrane. As the water goes in, the cytoplasm and vacuole will swell. The plant cell has a very strong cell wall around it. The cell wall is much stronger than the cell membrane and it stops the plant cell from bursting. The cytoplasm presses out against the cell wall, but the wall resists and presses back on the contents. Plant cells are said to be turgid,they will lose water by osmosis. The cytoplasm shrinks, and stops pushing outwards on the cell wall.So, the cell becomes floppy. It is said to be flaccid. If the cells in a plant become flaccid, the plant loses its firmness and begins to wilt.If the solution is very concentrated, water will diffuse out of the cell. The cell wall is too stiff to be able to shrink much. So the cell wall gets left behind. The cell membrane, surrounding the cytoplasm, tears away from the cell wall.A cell like this is said to be plasmolysed. Plant cells are not usually surrounded by very concentrated solutions. Plasmolysis usually kills a plant cell because the cell membrane is damaged as it tears away from the cell wall. ACTIVE TRANSPORT Root hair cells in plants take in nitrate ions from the soil. The concentration of nitrate ions inside the root hair cell is higher than the concentration in the soil. Despite this, the root hair cells are still able to take nitrate ions in, They do it by a process called active transport, an energy-consuming process by which substances are transported against their concentration gradient. The energy is provided by respiration in the cell. In the cell membrane of the root hair cells are special transport proteins. These proteins pick up nitrate ions from outside the cell, and then change shape in such a way that they push the nitrate ions through the cell membrane and into the cytoplasm of the cell. Active transport uses energy. The energy is provided by respiration inside the root hair cells. Energy is needed to produce the shape change in the transport protein. In the human small intestine, for example, glucose can be actively transported from the lumen of the intestine into the cells of the villi. In kidney tubules, glucose is actively transported out of the tubule and into the blood. CHAP 4: THE CHEMICALS OF LIFE WATER In most organisms, almost 80% of the body is made up of water. The spaces between our cells are also filled with a watery liquid.Inside every living organism, chemical reactions are going on all the time. These reactions are called metabolism. Metabolic reactions can only take place if the chemicals which are reacting are dissolved in water. Water is an important solvent. If their cells dry out, the reactions stop, and the organism dies.Plasma, the liquid part of blood, contains a lot of water, so that substances like glucose can dissolve in it. These dissolved substances are transported around the body.Is also needed to dissolve enzymes and nutrients in the alimentary canal, so that digestion can take place.We also need water to help us to get rid of waste products. CARBOHYDRATES Carbohydrates include starches and sugars. Their molecules contain three kinds of atoms - carbon (C), hydrogen (H), and oxygen (O). A carbohydrate molecule has about twice as many hydrogen atoms as carbon or oxygen atoms. SUGARS The simplest kinds of carbohydrates are the simple sugars or monosaccharides. Glucose is a simple sugar, their molecules are made of six carbon atoms joined in a ring, with the hydrogen and oxygen atoms pointing out from and into the ring, and contains six carbon atoms, twelve hydrogen atoms, and six oxygen atoms, its molecular formula can be written C₆H₁₂O₆ : stands for one molecule of this simple sugar. They are soluble in water, and they taste sweet.If two simple sugar molecules join together, a complex sugar or disaccharide is made. Two examples of complex sugars are sucrose (the sugar we use in hot drinks) and maltose (malt sugar). They are soluble in water and taste sweet. ● Amylase breaks starch; ● Maltas breaks maltose; ● Sucrase breaks sucrose. In an enzyme-controlled reaction, the substance present at the beginning is called substrate, while at the end is called product. An enzyme works by allowing the molecule of the substance on which it is acting to fit into it, like a lock with a key. They have complementary shapes. An amylase molecule has a dent in it called the active site. The starch fits into it, where it is broken down by the enzyme. All enzymes have active sites, that’s why enzymes can only act on a particular kind of substrate. PROPERTIES OF ENZYMES ● All enzymes are proteins; ● are made inactive by high temperatures; ● they work best at a particular temperature and a particular pH; ● they are catalysts: aren’t changed in the chemical reactions; ● they are specific: they catalyse only one kind of reaction. TEMPERATURE AND pH At higher temperatures reactions happen faster because the molecules have more kinetic energy. However, enzymes are damaged by high temperatures: as temperature increases the enzyme starts to lose its shape, so it can’t catalyse the reaction. In this case, the enzyme is said to be denatured. The temperature at which an enzyme works faster is called its optimum temperature. The same thing for the pH: the optimum pH is about 7 (neutral). If it is different the enzyme is denatured, because it loses its shape. Some enzymes have an optimum pH of about 2: for example a protease enzyme in the human stomach. CAP 6: PLANT NUTRITION The nutrition is taking in useful substances. Animals and fungi feed on substances called organic because they are made by plants from inorganic substances like CO2 or water. Plants make it by a process called photosynthesis.(the process by which plants manufacture carbohydrates from raw material using energy from light) During this process: - The sunlight energy is absorbed by a substance in chloroplast called chlorophyll (it makes plants green) - The substance releases this energy making CO2 combine with water with the help of enzymes inside chloroplast. - glucose and oxygen are made, - light energy is transferred to chemical energy. Chloroplasts are in the cells of the leaves. Leaves are made of: - lamina: the flat part - petiole. a stalk which contains vascular bundles (fasci vascolari) - veins: created by bundles, carry substances to and from the leaf - several layers of cells - Top and bottom covered by epidermis do not contain chloroplasts Cells of upper epidermis often secrete cuticle, a waxy (cerosa) substance which helps to stop water evaporation. The middle layer is the mesophyll, and it is divided into the palisade layer, nearer to the top and similar to a fence; and the spongy layer, with large air spaces between cells. In this layer there are veins, which contain both large xylem vessels for carrying water and smaller phloem tubes for carrying other substances that the leaf has made. The lower epidermis (no chloroplasts) contains small openings called stomata delimited by 2 guard cells which can open or close the hole. DURING PHOTOSYNTHESIS: Carbon dioxide: it is needed by mesophyll cells; it gets into the leaf through stomata by diffusion. Water: it is absorbed by root hairs and carried up from the xylem vessels to the mesophyll cells by osmosis. Sunlight: it is needed by mesophyll cells. The absence of chloroplasts in epidermal cells and the thinness of the leaf allows the sunlight to penetrate in as much quantity as possible. The aim of this process is to create glucose, but which are the uses of glucose? - Some of it will be broken down by respiration to release energy. - It may be turned into starch: glucose is a simple sugar, so it is not good for storage because it is reacted, so it might be involved in chemical reaction where it is not wanted or it would dissolve in water increasing the concentration of the solution in the cell. For these reasons it is converted into starch (a polysaccharide not very reactive and not very soluble) to be stored. - It may be used to make other organic substances like: 1. Amino acids: A plant absorbs nitrate ions from the soil with roots hairs, these ions combine with glucose to make amino acids for proteins. 2. Chlorophyll: Glucose + nitrate ions + magnesium, both obtained from the soil, make chlorophyll. - It is small and soluble, but reactive. So to be transported it has to be converted into complex sugar sucrose, which is also small and soluble but it is not reactive. TESTING STARCH A way to test if a leaf is photosynthesized or not is to control if there is starch. For this test iodine solution is used, if with this solution the leaf becomes blue, starch is present. But there are 2 problems: - Starch is inside the chloroplasts in the cells, so the solution can't get through the cell membranes to reach the starch and react with it - The green color of the leaf and the brown iodine solution can look black together, also if there is not starch The solutions to these problems are: - Cell membranes are broken down by boiling water - The chlorophyll is removed by dissolving it out with alcohol In this way starch can be used also for test which substances are necessary for photosynthesis: - In an investigation 2 plants are considered, one with all substances it needs and the other with all substances except one. - Both plants are then treated in exactly the same way. - At the end of the investigation all the differences between them must be because of the substance being tested. - If the tested leaf has no starch, it means that the substance it didn't have is necessary for photosynthesis. It is important to control that the tested leaf doesn't already have starch before the experiment, and therefore that it doesn't photosynthesize. So you have to destarch the plant and the easiest way to do this is to leave it in a dark cupboard for at least 24 hours. LIMITING FACTORS The rate at which a plant can photosynthesise is its ability to absorb sunlight, carbon dioxide and water. - Sunlight: as light intensity increases the rate of photosynthesis will increase, until it arrives at the point in which the plant is photosynthesising as fast as it can. At this point even if light becomes brighter the plant can't be photosynthesise any faster - Carbon dioxide: it is the same as sunlight: the more carbon dioxide a plant is given the faster it photosynthesise up to a maximum. - Temperature: less temperature less rate, but if the temperature is too high stomata often close to prevent too much water being lost, and if stomata are closed photosynthesis can't take place, so the rate will decrease. When plants are growing outside we can't control and change conditions, for this reason exist glasshouses, in which you can change the temperature, the light and also the carbon dioxide concentration. CAP 7: ANIMAL NUTRITION DIET The structure: 1. Root embedded in the gum. 2. crown be seen. 3.The crown is covered with enamel. Enamel is the hardest substance made by animals. It is very difficult to break; it can be dissolved by acids. 4.Under the enamel is a layer of dentine, which is rather like bone. Dentine is quite hard, but not as hard as enamel. It has channels in it which contain living cytoplasm. 5.In the middle of the tooth is the pulp cavity. It contains nerves and blood vessels. supply food and oxygen. 6.The root of the tooth is covered with cement. This has fibres growing out of it. These attach the tooth to the jawbone, but allow it to move slightly when biting or chewing. TYPES OF TEETH Most mammals have four kinds of teeth. 1.Incisors at the front of the mouth. They are used for biting off pieces of food. 2.Canines pointed teeth. 3.Premolars and molars are the large teeth towards the back of the mouth. They are used for chewing food. wisdom teeth (denti del giudizio). Mammals have two sets of teeth. The first set is called the milk teeth or deciduous teeth.begins to fall out. Make up a complete set of permanent teeth. There are 32. DENTAL DECAY Caused by bacteria. large numbers of bacteria living in your mouth, most are harmless. some with substances from your saliva, form a sticky film, next to the gums and in between the teeth. This is called plaque. Plaque is soft and easy to remove at first, but if it is left it hardens to form tartar, which cannot be removed by brushing. GUM DISEASE If plaque is not removed, the bacteria in it may infect the gums. Gums may bleed when you brush your teeth. This is usually painless, bacterias work down around the root of the tooth. The tooth becomes loose, and needs removing. TOOTH DECAY Sugar left on teeth, bacteria in the plaque will feed on it. They use it in respiration, changing it into acid. The acid dissolves the enamel and the dentine is dissolved away more rapidly than the enamel. the tooth needs to be taken out. keep your teeth and gums healthy. 1 Don't eat too much sugar. 2 Use fluoride toothpaste regularly. Fluoride makes your teeth more resistant to decay. 3 Make regular visits to a dentist. Prevents getting a hold. THE ALIMENTARY CANAL The alimentary canal is a long tube which runs from the mouth to the anus. It is part of the digestive system including the liver and the pancreas. The wall of the canal contains muscles, which contract and relax to make food move along. This movement is called peristalsis. To keep the food in one part of the alimentary canal for a while, muscles can close the tube. They are called sphincter muscles. To help the food to slide through the canal, it is lubricated with mucus. Each section has its own part to play in the digestion, absorption, and egestion of food. THE MOUTH Food is ingested using the teeth, lips and tongue. 1.Teeth bite smaller pieces, increasing its surface area. 2.The tongue mixes the food with saliva, and forms it into a bolus. The bolus is then swallowed. 3.Saliva is made in the salivary glands. It is a mixture of water, mucus and the enzyme amylase. -Water dissolves substances allowing us to taste them. -Mucus slides easily down the esophagus. -Amylase begins to digest starch in the food to the sugar maltose. THE OESOPHAGUS Takes food down to the stomach. When you swallow, epiglottis covers the entrance to the trachea, and it stops food from going down into the lungs. The entrance to the stomach from the esophagus is guarded by a ring of muscle called a sphincter. This muscle relaxes to let the food pass into the stomach. THE STOMACH the stomach has strong muscular walls they contract and relax, to churn the food and mix it with the enzymes and mucus (secreted by goblet cell). The mixture is called chyme. other cells produce protease enzymes and hydrochloric acid. situated in pits in wall. The main protease enzyme is pepsin. It digests proteins by breaking them down into polypeptides. Works best in acid conditions. The acid helps to kill bacteria in food. The stomach can store food for a long time. After, the sphincter at the bottom of the stomach opens and lets the chyme into the duodenum. THE SMALL INTESTINE The small intestine is the part of the alimentary canal between the stomach and the colon. It is about 5 m long, "small" because it is narrow. The first part, nearest to the stomach, is the duodenum. The last part, nearest to the colon, is the ileum. enzymes are secreted into the duodenum,made in the pancreas, which is a cream-coloured gland, lying just underneath the stomach. The pancreatic duct leads from the pancreas into the duodenum. Pancreatic juice (amylase,enzymes, protease and lipase) , flows in this tube. -Amylase breaks down starch to maltose. -Trypsin is a protease, which breaks down proteins to polypeptides. -Lipase breaks down fats (lipids) to fatty acids and glycerol. These enzymes do not work in acid environments, but the chyme coming from the stomach contains hydrochloric acid. Pancreatic juice contains sodium hydrogencarbonate which partially neutralises the acid. BILE fluid flows into the duodenum. Bile is a yellowish green, alkaline, watery liquid, which helps to neutralise the acidic mixture from the stomach. made in the liver, and then stored in the gall bladder. It flows to the duodenum along the bile duct. It does, however, help to digest fats. by breaking up the large drops of fat into very small ones, then lipase digest them into fatty acids and glycerol. This is called emulsification (a type of mechanical digestion), done by bile salts. Bile contains yellowish bile pigments,are made from hemoglobin. VILLI enzymes made in the pancreas and the small intestine,they are made by cells in its walls. The inner wall of the small intestine is covered with millions of tiny projections. They are called villi (singular: villus). Each villus is about 1 mm long. Cells covering the villi make enzymes. The enzymes stay close to the cells. enzymes complete the digestion of food. -maltase breaks down maltose to glucose -Proteases breaking down any polypeptides into amino acids -Lipase completes the breakdown of fats to fatty acids and glycerol. TRANSPIRATION=evaporation of water from a plant The mesophyll cells in leaves are covered with a thin film of moisture (pellicola di umidità) that evaporates from cells and the vapor diffuses out of the leaf through stomata. Water in xylem vessels will travel to replace it: it is constantly taken by the top of vessels and so the pressure at the top decreases and water flows up. WATER POTENTIAL (POTENZIALE IDRICO) GRADIENT The water potential in the soil is greater, the one in the leaves is smaller because of losses of water vapor. Bigger is the concentration and less is water, lower is the water potential. The structure of plants has characteristics that help water transport: - The surface of root hair increase the amount of water that can be absorbed - The hollow (vuoti) and narrow (stretti) xylem vessels provide an easy pathway for water, of which molecules stay together thanks to cohesion. - The air spaces inside the leaf increases the rate of evaporation, and so more water comes from vessels. - The stomata allow water vapor to diffuse easily out of the leaf. MEASURING TRANSPIRATION RATES It is difficult to measure how much water is lost from the leaves of a plant, but we can measure how fast the plant takes up water. In fact they are directly proportional. The apparatus that can measure it is called a potometer. This rate is affected by; - temperature: directly proportional - humidity: inversely proportional - wind speed: directly proportional - light intensity: directly proportional (more sunlight means more carbon dioxide for photosynthesis, so stomata open more) - water supply: inversely proportional (stomata close) If leaves lose too much water, the roots may not be able to take up enough to replace it, so leaves become flaccid. UPTAKE OF IONS: THE ACTIVE TRANSPORT Roots absorb water, but also mineral salts in the form of ions dissolved in the water in the soil. They travel into the xylem vessels with water. The concentration of these ions in the soil is lower than the one in the root hairs, so for diffusion it may go from the roots to the soil. But special cell surface membranes of root hairs transport these minerals in the cells against their concentration gradient. This is called active transport. TRANSLOCATION: SOURCES AND SINKS The transport of organic substances in phloem tubes from leaves to other parts is called translocation. The part of the plant from which food materials are being translocated is called a source, the one to which they are being translocated is called a sink. The sinks are especially: - roots, that change some of the sucrose produced into starch to store it. - flowers, that use sucrose to make fructose. Later, when fruits are developing large amounts of sucrose are used to produce sweet juicy fruits ready to attract animals. Many plants have a time of the year when they become dormant, so they don’t photosynthesize but survive on their stored starch and other materials. For example potatoes: CAP 9: TRANSPORT IN ANIMALS CIRCULAR SYSTEMS Also called the blood system, it is a network of blood vessels (tubes) that we can find in mammals. Blood starts in the lungs, where it takes oxygen, goes into the left-hand side of the heart, through vessels going to the rest of the body. Some of the oxygen is taken up by the body cells, which need it for respiration. Then deoxygenated blood comes back into the right-hand side of the heart. At the end it arrives in the lungs and the cycle starts again. The system is divided into 2 parts: from heart to lungs and back is called pulmonary system, from the heart to the rest of the body and back is called systemic system. Pressure of blood is greater from heart to cells and less from cells to heart. Fish have a single circulatory system, where blood is slower. THE HEART It is made of a special type of muscle called cardiac muscle, that contracts and relaxes regularly during life. It is divided into 4 chambers, 2 upper called atria and 2 lower called ventricles, and they are divided by one-way valves. Left ones and right ones are divided by a septum. The left atrium receives blood from the pulmonary veins and right one from the venae cavae. From the atria it goes to ventricles and it is pumped out: left one through the aorta and right one through the pulmonary artery. Ventricles have more muscular walls than atria. CORONARY ARTERIES They are blood vessels outside of the heart who constantly supply blood to the heart muscles: nutrients and oxygen inside it don't be able to diffuse to all the muscles quickly enough. If the coronary artery gets blocked, heart muscles can't pump blood anymore. This is called coronary heart disease and there are some factors which increase a person's risk of getting it: - Smoking cigarettes - Diet - Obesity - Stress - Genes It causes heart attack or cardiac arrest PREVENTING CHD (coronary heart disease) - not to smoke cigarettes - taking care of diet: variety of food and fats - regular exercise: to prevents excessive weight - people with high cholesterol (high quantity of fat in blood) may be prescribed a type of drug called statin, that reduces it. But it has some harmful effects, so it is only for severe cases (casi gravi). TREATING CHD Drugs: - statin - drugs that helps to lower blood pressure - drugs that decrease risk of blood clots (coaguli) inside blood vessels, like aspirin If drugs fails, is needed a surgery: - coronary bypass operation: the damaged artery is replaced with a length of blood vessels from another part of the body - insert a little tube called stent to keep it open - angioplasty: insert a tiny balloon which inflated (riempito) of water pushes the artery open. So balloon is removed Even if all of this isn't enough, patients require a heart transplant. It's difficult to find organs for all patients and sometimes the organ is rejected by the body. HEART BEAT: PACEMAKER Most people's hearts beat about 60 to 75 times a minute. Each complete "lub-dup" represents one beat. A way to measure beat is to take your pulse rate. A pulse is caused by the heart pushing blood. We can find a pulse wherever there is an artery near to the surface of the skin. Activity of the heart is recorded by electrocardiographs. Electrodes are stuck into the body and the electrical activity of the heart is recorded. A fast rate means more oxygen in the muscles. Rate is controlled by a patch of muscle in the right atrium called pacemaker. Brain sends electrical signals of a carbon dioxide increase in the body, so oxygen decreases, along nerves to the pacemaker and it makes the heart contract. Sometimes the pacemaker stops working, so it's possible to place an artificial one in the person's heart. It produces electrical impulse (1 per second). It is made by all the cells in the body as they respire and it diffuses through the walls of capillaries into the blood. - Most is carried by the plasma like hydrogencarbonate - A small amount is carried in Hb in red cells. It returned to heart, so to lungs, where it passed out of the body on expiration. Food materials Digested food is absorbed in a part of the intestine, and it dissolves into blood capillaries. These capillaries join up to form the hepatic portal vein. It takes nutrients to the liver, which processes it and returns some of it to the blood, so nutrients dissolve to all parts of the body. Urea It is a waste substance made in the liver. It dissolves in the blood plasma and it goes into kidneys, which excrete it in the urine. Hormones They are made in endocrine glands, they dissolve in the plasma and they are transported all over the body, Heat Some parts of the body such as muscles make heat. It goes into the blood, so into all the parts of the body and it helps to keep the body warm. Plasma proteins They are dissolved in plasma. An example is fibrinogen. LYMPH AND TISSUE FLUID TISSUE FLUID Between blood cells and elements there are some gaps (spazi vuoti). So white cells and plasma can move out of capillaries, but red cells can't. So plasma and white cells are continually leaking out of the capillaries. The fluid formed in this way is called tissue fluid. FUNCTIONS It diffuses nutrients to the cells and diffuses waste products in the opposite direction. (fa da tramite tra i capillari e le cellule) LYMPH In the new tissue there are new vessels called lymphatic capillaries that join up to form larger lymphatic vessels. The fluid inside it is called lymph. It flows into the new vessels and it returns in the blood from the arm's vein called the subclavian vein. These vessels have several lymph nodes, in which a part of white blood cells are produced. The lymphatic system doesn't pump to make the lymph flow, but it has valves. So lymph is slower than blood. CAP 10 PATHOGENS A pathogen is a microorganism that causes disease. Many diseases are caused by pathogens that get into our bodies and breed there. viruses—>infuenza bacteria—-->cholera tetanus protoctist—->malaria dissentery fungi—->ringworm Diseases passed from one person to another. They are called transmissible diseases. pathogens may damage our cells using their resources or by producing waste products, called toxins, which spread around the body and cause symptoms such as high temperature and rashes and make you feel ill. HOW PATHOGENS ENTER THE BODY Several ways DIRECT CONTACT The passing of a pathogen to an uninfected person is called transmission. The entry of the pathogen into the body is known as infection. The person in which the pathogen lives and breeds is said to be a host for that pathogen. Diseases transmitted are contagious diseases. -the virus of AIDS, called HIV (the human immunodeficiency virus),infected person's blood comes into contact with another person's blood. -The fungus that causes the skin infection, athlete's foot, can be passed on by sharing a towel with an infected person. INDIRECT TRANSMISSION Through the respiratory passages Cold and influenza viruses are carried in the air in tiny droplets of moisture.you can be infected If you breathe in the droplets, if you touch a surface on which they are present, and then put your hands to your face. In food or water Bacteria such as Salmonella can enter your alimentary canal with the food that you eat. If you eat a large number of these bacteria, you may get food poisoning. You can wash or Cook to destroy bacteria.Virus that causes poliomyelitis and the bacterium that causes cholera, are transmitted in water. By vectors A vector is an organism that carries a pathogen from one host to another. bats are vectors for the rabies virus, which is transmitted in their saliva when they bite. Anopheles mosquitoes are the vector for malaria. BODY DEFENCES The human body has many natural defenses against pathogens. Mechanical barriers These are structures that make it difficult for pathogens to get past them and into the body. For example,the skin has a thick outer layer of dead cells, containing a protein called keratin, that is very difficult to penetrate. When the skin is cut, blood clots seal the wound, which not only prevents blood loss but also prevents pathogens from getting into the blood through the cut. Chemical barriers Many parts of the body produce sticky mucus that can trap pathogens. In the stomach, hydrochloric acid is secreted, it kills many of the bacteria in the food that we eat. Pathogens can be destroyed by white blood cells or by phagocytosis or with the production of chemicals called antibodies.Vaccination helps antibodies to be produced very quickly. Food hygiene Good food hygiene makes it hard to get ill. Most food poisoning is caused by bacteria, keep conditions for bacteria to grow under control . Keep your own bacteria and viruses away from food. Always wash your hands. Keep your hair out of food, Never cough over food. Keep animals away from food. Covering food to keep flies and other animals from touching it is always a good idea. Do not keep foods at room temperature for long periods. Keeping food in the fridge will slow down bacterial growth. Cooking it at a high temperature will kill most bacteria. Keep raw meat away from other foods. Personal hygiene Personal hygiene means keeping your body clean. Waste disposal We produce an enormous amount of rubbish each year. This waste is collected and taken to landfill sites where there is space to put the rubbish. The rubbish is added in layers, and is compacted (pressed down) to reduce the space it takes up. Some of the rubbish in the landfill site is rotted by decomposers, especially bacteria. This produces a gas called methane, which is Eventually, when the landfill site is full, it can be covered over with soil and grass and trees allowed to grow. One of the hormones produced by the pancreas is insulin. This hormone is made when blood glucose concentration rises above normal, and it brings about events that cause the concentration to fall. Insulin is made by a particular type of cell in the pancreas called beta cells. Cells of their immune system attack the beta cells and destroy them. The loss of beta cells means that insulin is no longer produced, so blood glucose concentration is not controlled. Most people with type 1 diabetes have to take insulin. This can keep blood glucose concentration within normal limits. CHAP 11: RESPIRATION RESPIRATION Our cells need energy for: ● contracting muscles, ● making protein molecules by linking together amino acids into long chains ● cell division ● active transport ● transmitting nerve impulses ● producing heat inside the body All of this energy comes from the food that we eat. The food is digested - broken down into smaller molecules - which are absorbed from the intestine into the blood. The blood transports the nutrients to all the cells in the body. The cells take up the nutrients that they need. The main nutrient is glucose. Cells have to break down the glucose molecules and release the energy from them in a series of metabolic reactions called respiration, the action of enzymes is involved. AEROBIC RESPIRATION Our cells release energy from glucose by combining it with oxygen. This is called aerobic respiration, this happens in a series of small steps, each one controlled by enzymes,that take place inside mitochondria. ANAEROBIC RESPIRATION It is possible to release energy from sugar without using oxygen. But not much energy is released per glucose molecule. It is called anaerobic respiration.Yeast, a single-celled fungus, can respire anaerobically. It breaks down glucose to alcohol.Carbon dioxide is made.Plants can also respire anaerobically,also muscle cells can respire anaerobically for a short time. They make lactic acid instead of alcohol and no carbon dioxide is produced. This happens when your lungs and heart cannot supply oxygen to your muscles as quickly as they are using it. GAS EXCHANGE SURFACES Two substances are needed. They are glucose and oxygen. Animals get sugar from carbohydrates which they eat. Plants make theirs by photosynthesis One gas is entering, and the other leaving, so these are surfaces for gas exchange. These surfaces are permeable. Characteristics: 1. They are thin to allow gasses to diffuse across them quickly. 2. They are close to an efficient transport system to take gases to and from the exchange surface. 3. They have a large surface area, so that a lot of gas can diffuse across at the same time. 4. They have a good supply of oxygen HUMAN BREATHING SYSTEM We have two lungs, each lung is filled with many tiny air spaces called air sacs or alveoli. Lungs feel very light and spongy to touch are supplied with air through the trachea. THE PATHWAY TO THE LUNGS NOSE AND MOUTH Air can enter the body through either the nose or mouth, separated by the palate. It is better to breathe through your nose, because the structure of the nose allows the air to become warm, moist and filtered before it gets to the lungs. Hairs in the nose trap dust particles in the air. Inside the nose are some thin bones called turbinal bones which are covered with a thin layer of cells. Some of these,called goblet cells, make a liquid containing water and mucus which evaporates into the air in the nose and moistens it. Other cells have very tiny hair-like projections called cilia,always moving and bacteria or particles of dust get trapped in them and in the mucus; are found all along the trachea and bronchi, too.Here they waft the mucus, up to the back of the throat, so that it does not block up the lungs. TRACHEA The air then passes into the windpipe or trachea. At the top of it is a piece of cartilage called the epiglottis. This closes the trachea and stops food going down the trachea when you swallow. Just below the epiglottis is the voice box or larynx,containing the vocal cords,can be tightened by muscles so that they make sounds when air passes over them. The trachea has rings of cartilage around it which keep it open. BRONCHI The trachea goes down through the neck and into the thorax, where it divides into two.The two branches are called the right and left bronchi. One bronchus goes to each lung and then branches out into smaller tubes called bronchioles. ALVEOLI At the end of each bronchiole are many tiny air sacs or alveoli ,where gas exchange takes place. GAS EXCHANGE IN LUNGS The walls of the alveoli are the gas exchange surface. Tiny capillaries are closely wrapped around the outside of the alveoli . Oxygen diffuses across the walls of the alveoli into the blood. Carbon dioxide diffuses the other way. The walls of the alveoli have several features: ● They are very thin.The capillary walls are also only one cell thick. ● They have an excellent transport system. Carbon dioxide in the blood can diffuse out into the air spaces in the alveoli and oxygen can diffuse into the blood. The blood is then taken back to the heart in the pulmonary vein, ready to be pumped to the rest of the body. ● They have a large surface area. The total surface area of all the alveoli in your lungs is over 100 m2 ● They have a good supply of oxygen. BREATHING MOVEMENTS To make air move in and out of the lungs, you must keep changing the volume of your thorax.This is called breathing.The intercostal muscles between the ribs and the diaphragm. The diaphragm is a large sheet of muscle and elastic tissue which stretches across your body, underneath the lungs and heart. INSPIRATION When breathing in, the muscles of the diaphragm contract. This pulls the diaphragm downwards, which increases the volume in the thorax . At the same time, the external intercostal muscles contract.This pulls the rib cage upwards and outwards, also increases the volume of the thorax.As the volume of the thorax increases, the pressure inside it falls below atmospheric pressure. EXPIRATION When breathing out, the muscles of the diaphragm relax. The diaphragm springs back up into its domed shape because it is made of elastic tissue. This decreases the volume in the thorax. The external intercostal muscles also relax. The rib cage drops down again into its normal position.When you breathe out more forcefully the internal intercostal muscles contract strongly, making the rib cage drop down even further. The muscles of the abdomen wall also contract.