BIOLOGY IGCSE. PIETRO MIOZZO 4A May 30, the blood passes through the heart twice on one complete journey around body

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1 BIOLOGY IGCSE PIETRO MIOZZO 4A May 30, 2008 Contents Year 3 1 The Variety of Life 2 Cells, diffusion, and Osmosis 3 Enzymes 4 Nutrition and a Balanced Diet 5 Digestion and Absorption 6 Nutrition in Plants Year 4 7 Transport in Animals 7.1 Double circulation the blood passes through the heart twice on one complete journey around body the right side of the heart pumps blood to the lungs. Blood returns from the lungs to the left side of the heart. The left side then pumps blood to every other part of the body. The muscle surrounding the left ventricle is fthicker, enabling it to pump blood around the body. 1

2 when blood is in the lungs, it picks up oxygen > oxygenated blood when blood is in other parts of body (e.g., brain) it gives up oxygen > deoxygenated blood 7.2 The heart (diagram p. 96) made up of cardiac muscle needs constant supply of glucose and oxygen supplied by the blood blood supply from coronary arteries The heart is in 2 sections separated by the septum stops separates oxygenated and deoxygenated sections 7.3 Heartbeat exercise causes the heart to beat faster than at rest, so oxygen and glucose can travel around the body quicker, to where it is needed more. 1. Heart is relaxed and both sides fill up with blood from veins. This relaxation is called DIASTOLE. When relaxed, the heart is slightly larger. 2. The artia contract, and blood is forced into the ventricles through the valves. This is called ATRIAL DIASTOLE. Tricuspid and bicuspid valves are open to allow blood to flow into ventricles. 3. A fraction of a second later, the vantricles contract. The valves between the atria dn the ventricles close, so blood is squeezed into arteries. Ventricle contraction is called VENTRICULAR SYSTOLE. 4. The heart relaxes again, and fills up with blood. This again is DIASTOLE. 7.4 Heart attacks major cause of death in many parts of the world Triggers include food and lifestyle: eating salty foods eating fatty foods not exercising regularly smoking stressful routine sometimes hereditary 2

3 age-related heart attacks happen when one of the coronary arteries gets blocked this stops oxygen and glucose from gettiong to the cardiac muscle 7.5 Blood vessels VESSEL BLOOD STRUCTURE ARTERY High pressure, oxygenated Small lumen, elastic walls (thick layer of muscle) smooth CAPILLARY Low pressure, oxygenated Very small, one cell thick (quick diffusion of O VEIN Low pressure, deoxygenated Large lumen, thin layer of muscle 7.6 Components of the blood cells float in a liquid in the blood called plasma pale yellow mostly water but contains many other substances dissolved in it glucose amino acids hormones &c red blood cells biconcave disc very small carry hemoglobin (blue-purple) > oxyhemoglobin when saturated with oxygen (red) white blood cells: part of the body s immune system phagocytes eat harmful bacteria in the body (phagocytosis) lymphocytes platelets phagocytes engulf bacteria they then digest them with enzymes any useful substances are used by the phagocyte make antibodies made up of fragments of old red blood cells 3

4 sticky vital in clotting when there is a cut, platelets bump into the rough, damaged wall (usually smooth) and stick the walls and the platelets react by producing a protein, causing the soluble fibrinogen to turn into insoluble fibrin long fibers are formed, which precipitate out of the blood plasma these fibers get tangled together and with platelets, wbcs, and rbcs, forming a clot. 8 Transport in Plants 8.1 Root hair cells /Users/michelemiozzo/Desktop/rhairc.gif very delicate, easily damaged hairs are to increased the SA over which minerals and water, etc, cen be absorbed from the soil the hairs move inbetween gaps in the soil water moves from the soil into the cells because the soil has a higher water potential than the root cell s cytoplasm membrane is partially permeable: minerals, proteins, and the like cannot go out of the cell even though they can come in some salts are absorbed by active uptake 8.2 The transpiration stream transpiration is the process by which water diffuses out of a plant s leaves into the air through the stomata 1. water enters root hairs 2. water moves to the xylem vessels in center of root 3. water moves into xylem vessels, which are in vascular bundles near the outside of the stem 4. water moves through the xylem vessels in vascular bundles in the leaves 5. water evaporates inside the leaf, and diffuses into the air through the stomata on the underside of the leaf 4

5 8.3 Water loss this can be increased by higher/more: light intensity temperatures wind speed water supply leaf SA air spaces stomatae this can be decreased by higher/more: humidity wilting occurs when there is not enough water to support the plant (low turgor pressure), and not enough to sustain it 8.4 The pull of transpiration As water leaves the xylem vessel, it reduces the water presure at the top of the xylem vessels therefore, water moves from a greater pressure to a lower pressure water molecules are sticky and hold each other due to hydrogen bonding the water moves up the xylem due to transpiration, which produces a pull/tension therefore, transpiration can be called the cohesion tension theory 8.5 Plant adaptations ADAPTATION HOW IT WORKS EXAMPLE thick cuticle stops uncontrolled evap. thru leaf cells small leaf SA less SA for evap. conifer needles, cactus spines low stomata density smaller SA for diff. sunken stomata maintains humid air around stomatae marram grass, cacti stomatal hairs maintains humid air around stomatae marram grass, couch grass rolled leaves maintains humid air around stomatae marram grass extensive roots maximizes water uptake (gets to water basin) cacti 5

6 8.6 Translocation translocation is the movement of sucrose and amino acids from regions of production or of storage to regions of utilization in respiration or growth through phloem tubes the substances are also transported to sinks, where they are stored. systemic pesticides are also transported in this way around the plant inthe phloem 9 Respiration and Gaseous Exchange 9.1 Respiration respiration is the release of energy from food substances in all living cells (it is a redox reaction) energy from respiration is needed in the human body for: respiration active transport muscle contraction growth transmission of nerve impulses Aerobic aerobic respiration is the release of energy from food in living cells in the presence of oxygen (the breakdown of glucose using oxygen to release energy which can be used by living cells) glucose + oxygen > carbon dioxide + water + energy C 6 H 12 O 6 + 6O 2 > 6CO 2 + 6H 2 O + 38ATP water and carbon dioxide are by-products, and are not the useful products from this reaction (ATP is) Anaerobic anaerobic respiration is the release of energy from food in living cells in the absence of oxygen (the breakdown of glucose without using oxygen to release energy which can be used by living cells) anaerobic respiration in muscles: glucose > lactic acid + energy C 6 H 12 O 6 > 2C 3 H 6 O 3 + 2ATP 6

7 anaerobic respiration takes over from aerobic respiration in muscles when there is a shortage of oxygen muscle cells can only respire anaerobically for a short time because the build up of lactic acid (toxic) interferes with muscle contraction, causing cramps lactic acid diffuses from muscles into the blood and is taken to the liver in the liver, it is broken down by combining it with oxygen high breathing rate continues long after exercise to break it down REPAYING THE OXYGEN DEBT (the body produces energy first and obtains oxygen to pay for it later) anaerobic respiration in yeast: glucose > carbon dioxide + ethanol + energy C 6 H 12 O 6 > 2CO 2 + 2C 2 H 5 OH + 2ATP can also be called fermentation can be used in bread making: flour contains starch eyast is added to wet flour and the enzymes produced by the yeast break down the starch into sugar yeast respires anaerobically and forms CO 2 bubbles, which are trapped in the dough; these bubbles rise and therefore the bread rises ethanol produced evaporates when the breadi is baked this is the smell of bread breaking the yeast is killed by the high temperartures during baking can be used in brewing yeast is added to a source of sugar, and is kept in warm conditions yeast respires anaerobically to produce ethanol, making the drink alcoholic eventually the ethanol levels rise to a poit which kills the yeast other micro-organisms must not be allowed to enter tje liquid or the ethanol will be converted to ethanoic acid (vinegar) Comparison of aerobic and anaerobic AEROBIC ANAEROBIC SIMILARITIES: needs glucose needs glucose produces ATP produces ATP DIFFERENCES: needs O 2 does not need O 2 produces 38ATP produces only 2ATP can happen for a long time can only happen for a short time CO 2 + H 2 O by-products lactic acid by product, no CO 2 + H 2 O produced 7

8 9.2 Gaseous exchange Alveoli in the lungs the alveoli are well adapted for their role as a gaseous exchange surface: large SA: increased by the alveoli 350 million alveoli = 70m 2 this increases the rate at which diffusion can happen thin epithelium: 2 cell layer separates air in alveoli from the blood in the capillaries onyl a short difusion distance for gases to diffuse moist: gases dissolve in solution before diffusion more efficient diffusion, and keeps the cells hydrated good blood supply to and from lungs by capillary network: maintains concentration gradients by removing oxygenated blood from the lungs quickly and bringing deoxygenated blood to the lungs quickly Inspired and expired air INSPIRED AIR EXPIRED AIR less CO 2 more CO 2 more oxygen less oxygen cooler warmer not much water vapor much more water vapor carbon dioxide can be tested for by passing/bubbling the gas in question through a flask of colorless limewater in the presence of CO 2, the limewater will change color from colorless to milky/cloudy 9.3 What we inhale Cells lining respiratory system Air around us The air around us contains dust particles and bacteria The pathway to the lungs stops a large number of these unwanted things from getting into the alveoli, where they could cause damage Goblet cells Make sticky, slimy mucus Many dust particles and bacteria from the air can get trapped in the mucus 8

9 Ciliated cells Have tiny microscopic hairs on them called cilia Not the same as human hair Much smaller Cannot be seen by even the best of school microscopes The cilia on the cells beat in unison Sweep mucus upwards, towards back of throat The mucus is swallowed Within the mucus are all the dust particles and the bacteria Mucus digested, and the bacteria are killed by the HCl and enzymes in the stomach Errant bacteria and dust Even though the respiratory system has an excellent filtering system, some bacteria and dust particles get to the alveoli On the surface of the alveoli, patrolling white blood cells constantly move around The WBCs take in and digest any foreign material they encounter Cigarette smoke Effects of Contains many harmful substances Nicotine Tar Carbon dioxide Carbon monoxide Cigarette smoke (and other kinds of smoke) can cause harmful and sometimes fatal damage and disease These effects can be manifested as a result of passive/second hand smoke as well 9

10 Harmful substances Nicotine Tar It is a drug that affects the brain Makes people feel more relaxed It is an addictive drug Regular smokers can not easily give up, as their bodies demand more nicotine Affects the blood system Increases heart rate Increases blood pressure These two effects can put strain on the heart Smokers are more likely to suffer from heart disease than nonsmokers Can cause cancer Most common cancer caused by smoke is lung cancer lung cancer is difficult to cure Smoking can also increase the risk of suffering other cancers as well, though Cancer happens when cells divide uncontrollably Normally, cells only divide when necessary sometimes the DNA in a cell can be damaged in a way that causes the cell to divide repeatedly If this does not happen (if they multiply erratically), a mass of cells called a tumor form If the tumor spreads, it is called a cancer Many cancers can be cured if caught early on The tumor can be removed by surgery or the cancerous cells can be killed with radiation or chemicals The tar can cause cancer by damaging the DNA in the cells, most likely in the lungs or the tubes leading to them The tar can also go into the blood and be carried to other parts of the body, damaging the DNA in the cells there, causing cancer Also can affect the lining of the tubes leading to the lungs 10

11 It can destroy or paralyze the cilia If this happens, they can no longer sweep mucus up to the throat The tar can stimulate the goblet cells to make more mucus than normal Carbon monoxide The mucus slides into the lungs, where bacteria may breed in it, causing disease To remove the mucus, the person can try coughing, damaging the lungs and the lining of its tubes even further This is called bronchitis Sometimes the damage is so bad that the the walls of the alveoli, stopping oxygen and carbon dioxide from in and out of the blood easily This causes the person to not get enough oxygen This is called emphysema CO in cigarette smoke diffuses into the blood from the alveoli It combines with hemoglobin, like oxygen However, unlike oxygen, the CO does not separate from the hemoglobin, combining irreversibly Up to 7% of a smoker s hemoglobin is combined with CO 9.4 Ventilation Inhalation This CO cannot be used for carrying oxygen So, smokers are likely to run short of oxygen if they attempt anything energetic They may feel short of breath the ribcage is moved upward and outward by the contraction of the external intercostal muscles the diaphragm is pulled down flat to help increase the volume of the thorax The volume inside the airtight thorax is increased, causing the pressure to drop. Air is pushed in by the higher pressure outside, via the nose and mouth. 11

12 9.4.2 Exhalation the ribcage is moved downward and inward by the contraction of the internal intercostal muscles the diaphragm returnes to a domed state The volume of the thorax decreases and the pressure increases as the stretched elastic tissue of the lungs recoils and the cotents of the abdomen push upward. Air flows outwards. 9.5 Change in breathing from exercise the frequency and depth of breathing increases after exercise more O 2 is supplied to respiring tissue/muscle more CO 2 is removed from respiring tissue/muscle if necessary, the oxygen debt can be repayed the presence of CO 2 in the lungs is detected by chemoreceptors found in the medulla, the carotid arteries, and in the aorta send impulses to the medulla, which then sends impulses to the intercostal muscles and the diaphragm, causing them to contract more frequently as rate of respiration increases increased respiration causes increased production of CO 2 CO 2 dissolves in H 2 O to form carbonic acid CO 2 + H 2 O H 2 CO 3 H + + HCO 3 hydrogen ions lower blood ph, which could disrupt enzyme activity hydrogen ions are taken up by oxyhemoglobin, and the oxygen is released, further disrupting body processes 10 Excretion and Homeostasis 11 Coordination and Response to Stimuli 12

Biology Notes. Homeostasis

Biology Notes. Homeostasis Biology Notes Homeostasis Homeostasis is defined as the maintenance of constant internal conditions within organisms. The principle can be developed in a wide range of contexts, including the maintenance