Exam Survival Guide IGCSE Biology Study Notes Topic
Exam Survival Guide IGCSE Biology Study Notes Topic 4 Respiration and the Human transport System TEXT BOOK CHAPTER 9 (P 112 -125) AND 8 (P 84 -99)
Energy released from respiration In animals In plants ▪ Contracting muscles ▪ Growth and repair ▪ Active transport ▪ Reproduction ▪ Making protein molecules ▪ Transporting food materials between cells and inside cells ▪ Transmitting nerve impulses ▪ Producing heat ▪ Cell division
Types of respiration Aerobic respiration Anaerobic respiration ▪ Main source of energy ▪ Secondary source of energy ▪ Produces 38 molecules of ATP for each molecule of glucose broken down ▪ Produces 2 molecules of ATP for each molecule of glucose broken down ▪ Involves plenty of oxygen and produces plenty of carbon dioxide ▪ Doesn’t involve oxygen, and the product depends on two types of anaerobic respiration: 1, yeasts and plants alcohol and carbon dioxide 2, animals lactic acid
Chemical equations 1. Aerobic respiration: Glucose + Oxygen Carbon dioxide + Water C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O 2. Anaerobic respiration (in plants and yeasts) (=fermentation): Glucose Alcohol + Carbon dioxide C 6 H 12 O 6 2 C 2 H 5 OH + 2 CO 2 3. Anaerobic respiration (in animals): Glucose Lactic acid C 6 H 12 O 6 2 C 3 H 6 O 3
Anaerobic respiration and lactic acid u. Muscles only respire anaerobically when exercising vigorously. u. The product of anaerobic respiration, lactic acid, may cause cramp or muscle fatigue. u. Muscle cramp would stop the athletes running. u. So a sprinter has to pant to get enough oxygen to the muscles to repay the oxygen debts. u. And a long distance runner has to pace to prevent muscles respire anaerobically. u. An oxygen debts is created because oxygen is needed to convert lactic acid back to harmless chemical – pyruvic acid.
The respiratory system Nose Trachea Bronchi • warm • Moist • Filter • Contains ciliated cells and goblet cells • = windpipe • Supports by rings of cartilage • Divided trachea into two bronchi • Support by rings of cartilage • Lined with a mucus membrane
The respiratory system • Smaller tubes where the bronchi are divided into • Not held by rings of cartilage Bronchioles • Lined with a mucus membrane Alveoli • Small air sacs • Where gas exchange takes place pulmonary arteries alveoli pulmonary veins
The respiratory system Other important organs: 1. Pharynx 2. Epiglottis – separating the trachea and the oesophagus 3. Larynx – under the epiglottis, containing vocal cords which can be tightened by muscles so that they make sounds when air passes over them ▪ Goblet cells – secrete mucus to moist air and trap bacteria ▪ Ciliated cells – trap bacteria and dust and waft them with mucus to the back of the throat to be swallowed
Features of alveoli for gas exchange 1. Thin – wall of alveolus is one cell thick 2. Close to an efficient transport system – oxygenated blood can be transported to body cells as soon as the gas exchange finishes 3. Kept moist – prevent cells from drying out 4. Large surface area – more gases can diffuse across at the same time 5. Good supply of oxygen – the breathing movement keep your lungs well supplied with oxygen
Breathing remember that air moves from high pressure to low pressure Inspiration Expiration • Diaphragm contracts, moves downwards • External intercostal muscles contract, pull the rib cage upwards and outwards • Volume of the thorax increases creating low pressure and air spaces (lungs expand) • Diaphragm relaxes, springs up into its domed shape • External intercostal muscles relax, return the rib to their original position • Volume of the thorax decreases creating high pressure and forcing the air out (lungs shrink) Force breathing, (e. g. coughing) • The internal intercostal muscles contract strongly, making the rib cage drop down further • The muscles of the abdomen wall also contract, helping to squeeze extra air out of the thorax
Inspired and expired air (number in %) oxygen carbon dioxide 1 1 4 0, 04 16 21 79 expired 79 inspired other noble gases nitrogen
p. H and Breathing rate ▪ If the concentration of carbon dioxide or lactic acid in the blood (both acidic) is high, the p. H will fall which can be sensed by the brain. The brain is then send nerve impulses to the diaphragm and the intercostal muscles, stimulating them to contract harder and more often, which results a faster breathing rate. ▪ THE DIAGRAM AND THE INTERCOSTAL MUSCLES WON’T WORK WITHOUT A SIGNIFICANT AMOUNT OF CARBON DIOXIDE OR LACTIC ACID.
The heart Pulmonary vein Left atrium Left ventricle Vena cava Right atrium Body cells Right ventricle Aorta Pulmonary artery
The heart p. Septum – separating the right and left ventricles p. Semilunar valves – controlling the blood going OUT of the heart (the vessels that bring blood away are pulmonary artery and aorta) p. Tricuspid valve – controlling the blood flowing from the right atrium to the right ventricle p. Bicuspid valve – controlling the blood flowing from the left atrium to the left ventricle p. The coronary arteries supply the hear muscle (cardiac muscle) with food and oxygenated blood *the heart attack or cardiac arrest happens when a coronary artery gets blocked by blood clot or saturated fat, which stops the heart beating and supplying the body with oxygenated blood
Factors increasing a person’s risk of getting coronary heart disease ① Smoking cigarettes nicotine ② Diet too much salt, saturated fats or cholesterol ③ Obesity ④ Stress ⑤ Genes
Cardiac cycle Atrial systole • All muscles are relaxed, blood flows into the heart • The atrioventricular valves open (to let blood comes into the atria from veins) • The semilunar valves shut (to prevent blood flows into the ventricles from arteries) Diastole venae cavae and pulmonary atria ventricles • Atria contract, ventricles relax, blood is forced into the ventricles from the atria • The atrioventricular valves open (to let blood comes into the ventricles from atria) • The semilunar valves shut (to prevent blood flows into the ventricles from arteries) • Ventricles contract, atria relax, blood is forced out of the ventricles into the arteries • The atrioventricular valves shut (to prevent blood pumps back to the atria by the ventricles) • The semilunar valves open (to let blood goes into the arteries) Ventricular systole ventricles pulmonary artery and aorta
Quick note on blood vessels ▪ Arteries: 1. 2. 3. 4. 5. Thick, strong, elastic walls Lumens are narrow No valves High pressure Carry blood away from the heart (oxygenated blood, except pulmonary artery) ▪ Veins: 1. 2. 3. 4. 5. Thin walls with less muscle and elastic tissue Wide lumen Valves present Low pressure Return blood to the heart • Capillaries: 1. 2. 3. 4. Walls that are one cell thick Very narrow lumen No valves Contact with body tissues
Components of blood plasma ▪ Plasma protein • Fibrinogen blood clotting • Antibodies destroy invading pathogens ▪ Lipids • Cholesterol and fatty acids storage and energy sources ▪ Carbohydrates energy sources for respiration ▪ Hormones from endocrine glands to target organ, then broken down by the liver and excreted by the kidneys ▪ Excretory substances to kidneys ▪ Dissolved gases most CO 2 is carried as hydrogen carbonate ions in the blood plasma (note that O 2 is carried in haemoglobin of red blood cells, not blood plasma) ▪ Mineral ions and vitamins ▪ Heat ▪ Water
Red blood cells ▪ Made in the bone marrow ▪ Producing rate: 9000 million/hour ▪ Life approx. 4 months ▪ Broken down when old, in the liver, spleen and bone marrow, resulted in bile pigment and excreted
White blood cells ▪ Made in the bone marrow and in the lymph nodes 1. ▪ ▪ ▪ Phagocytes: Targets: pathogens and damaged body cells Appearance: lobed nuclei Method used to destroy targets: phagocytosis (enclose the target in a vacuole, and digest it) 2. ▪ ▪ ▪ Lymphocytes: Targets: pathogens/antigens Appearance: large nucleus Method used to destroy targets: secrete antibodies (divide itself first before secrete antibodies, one cell to continue the secretion and one cell for memorise the antigen type)
Main blood vessels u. Lungs • pulmonary artery • pulmonary vein u. Liver • hepatic artery • hepatic portal vein • hepatic vein u. Kidney • renal artery • renal vein u. Heart • venae cavae • pulmonary artery • pulmonary vein • aorta
Platelets ▪ Small fragments of cells with no nucleus ▪ Made in the red bone marrow ▪ Blood clotting to stop pathogens getting into the body, and prevent from blood loss by forming a protective layer at the surface of the damaged blood vessels ▪ They also release chemical to change soluble fibrinogen to insoluble fibrin forms fibre which helps in blood clotting
Tissue fluid and the lymph system ØBlood plasma from capillaries bath the muscle tissues for exchange substances by diffusion becomes tissue fluid either goes to the lymphatic capillaries or back to the veins of the circulatory system ØAnother function of tissue fluid is to keep the body temperature and osmotic concentration constant (homeostasis) Ø Lymph is when tissue fluid drains into the lymphatic capillaries Ø The lymph vessels have similar functions as the veins, and they both have valves Ø The lymph system also prevents the blood in the form of lymph fluid builds up in the tissues Ø The lymph vessels contain many lymph nodes and each lymph nodes contain many white blood cells Ø Digested fat from the ileum are moved into the lymph vessels through lacteals
Experiments üFormula for comparing the energy content of two kinds of food: heat energy (J) = change in temperature (ºC) * volume of water (cm 2) *4. 2 üTest for carbon dioxide: use limewater (clear cloudy) or hydrogen carbonate (red yellow)
Glossary (text book definitions) ▪ Breathing: muscular movements which cause air to move into and out of the lungs • Lumen: the space in the centre of a tube; the veins have larger lumen than the arteries ▪ Gas exchange: the entry of oxygen into an organism's body, and the loss of carbon dioxide • Homeostasis: the maintenance of a constant internal environment ▪ Respiration: the chemical reactions that break down nutrient molecules in living cells to release energy ▪ Diaphragm: a sheet of muscles that increases and decrease air pressure inside chest cavity of body ▪ Intercostal muscle: muscles between the ribs, which help to produce breathing movements ▪ Double circulatory system: a system in which blood passes twice through the heart on one complete circuit of the body ▪ Systole: the stage of a heart beat in which the muscles in the walls of the heart chambers contract ▪ Diastole: the stage of a heart beat in which the muscles in the heart relax • Lymph: the fluid found inside lymph vessels, formed from tissue fluid • Lymph nodes: organs in which larger numbers of white blood cells (which can destroy bacteria or toxins) collect • Pathogens: a microorganism that causes disease • Antigens: chemicals on the surface of pathogens, which are recognised as foreign by the body • Antibodies: chemicals secreted by lymphocytes, which attach to antigens and help to destroy them
- Slides: 25