Edexcel IGCSE Human Biology Answers Assignment

Edexcel IGCSE Human Biology Answers Assignment Words: 1250

About 75 oc. Human Biology 2 b) At 60 oc the molecules of enzyme and substrate have more kinetic energy and move around more quickly. There are more frequent collisions between nzyme and substrate molecules, so more reactions are likely to take place. c) The microorganism lives at high temperatures, so it needs ‘heat-resistant’ enzymes with a high optimum temperature. d) It is denatured. 4 Diffusion is the net movement of particles (molecules or ions) from a high to low concentration. It does not need energy from respiration. Active transport uses energy from respiration to transport particles against a concentration gradient. The function of the motor neurone is to send nerve impulses to muscles and glands. It has a long axon which conducts these impulses. It has a cell body ith many extensions called dendrons and dendrites, which link with other neurones at synapses. At the other end of the neurone, the axon branches and forms connections with muscle fibres, called nerve-muscle junctions. The function of the red blood cell is to transport oxygen around the body. Its biconcave disc shape gives it a large surface area to absorb oxygen. It contains the pigment haemoglobin, which combines with oxygen.

The red blood cell has no nucleus, to allow it to carry more haemoglobin. 6 They carry out most of the reactions of respiration in the cell, providing it with energy. ) Active transport. This uses the energy from the mitochondria. @ Pearson Education Ltd 2010 7 d) b) 8 Diffusion. The removal of glucose at A lowers the concentration inside the cell, so that the concentration at B is higher than inside the cell. Therefore glucose can diffuse down a concentration gradient. Increases the surface area for greater absorption. Tube B/ 0. 85% salt solution. Tube A – no cells visible (they have burst).

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Tube B ” normal red blood cells seen. Tube C – shrunken red blood cells with crinkly edges visible. In A (water) the cells absorb water by osmosis. They burst, releasing the red aemoglobin into solution. In B (0. 85% salt solution) there is no net water movement in or out of the cells, so they remain normal in appearance. In C (3% salt solution) water is lost from the cells by osmosis, so they shrink. 0. 85% salt solution is the same concentration as blood plasma, so it will not cause osmotic damage to the blood cells. Water would cause the blood cells to burst (due to entry of water by osmosis).

The artery is an organ because it is made of several tissues; the capillary is made up of only one type of cell. Breaks down large insoluble molecules into smaller soluble molecules that an be absorbed. ii) Three from: mouth: chews / breaks down food into smaller pieces / produces saliva; oesophagus (gullet): move food from mouth to stomach; stomach: produces digestive enzymes; pancreas: produces digestive enzymes; liver: makes bile; ileum (small intestine) produces digestive enzymes / absorbs products of digestion; colon (large intestine): absorbs excess water; rectum: stores waste (faeces). ii) Two from: Breathing system: trachea, lung, diaphragm; Circulatory system: artery, vein, heart; Musculoskeletal system: muscle, joint, (named) bone; Nervous system: brain, spinal cord; Reproductive system: testis, ovary, uterus, penis; Excretory system: kidney, bladder. Feature Active transport Osmosis Diffusion particles must have kinetic energy requires energy from respiration particles move down a concentration gradient process needs special carriers in the membrane O Pearson Education Ltd 2010 10 a) So that each of the two cells produced will have the correct number of chromosomes / correct amount of DNA after the division. The nucleus has divided into two. As the glucose moves out of the cell, the concentration inside the cell ecreases and increases the concentration gradient for diffusion of glucose into the cell.

They (further) increase the surface area for absorption. @ Pearson Education Ltd 201 0 Chapter 2 Action during inhalation Action during exhalation External intercostal muscles (contract) relax Internal intercostal muscles contract Ribs move up and out (move down and in) Diaphragm contracts and flattens relaxes and becomes dome-shaped Volume of thorax increases decreases Pressure in thorax Volume of air in lungs Increases When we breathe in, the external intercostal muscles between our ribs contract, pulling the ribs up and out.

The diaphragm muscles contract, flattening the diaphragm. This increases the volume in the chest cavity, lowering the pressure there, and causing air to enter from outside the body, through the nose or mouth. This is called ventilation. In the air sacs of the lungs, oxygen enters the blood. The blood then takes the oxygen around the body, where it is used by the cells. The blood returns to the lungs, where carbon dioxide leaves the blood and enters the air sacs.

When we breathe out, the external intercostal muscles relax and the ribs move down and in. The diaphragm muscles relax, and the diaphragm returns to a dome shape. These changes decrease the volume of the chest cavity, increasing the pressure in the cavity, pushing the air out of the lungs. When the volume of the chest is increased by the movements of the ribs and diaphragm, the drop in pressure in the chest cavity draws air into the pleural cavity through the puncture in the chest wall, instead of through the mouth or nose into the lung. ) Each lung is isolated from the other by being in a separate pleural cavity, so a pneumothorax on one side will not affect the opposite lung. A tube is inserted through the chest wall into the pleural cavity on the side of the injured lung. This stops ventilation in that lung while the other lung will be ventilated normally. The rings support the trachea so that it does not collapse during inhalation. The gap in the ‘C’ allows food to pass down the oesophagus, which runs next to the trachea, without catching on the rings. ) The short distance allows easy diffusion of oxygen into the blood, and diffusion Of carbon dioxide out Of the blood. The mucus traps bacteria and dirt particles. The cilia beat backwards and forwards to sweep these towards the mouth, preventing them entering the lungs. d) Smoke contains carbon monoxide, which displaces oxygen from the aemoglobin of the red blood cells of the smoker. The addictive drug in tobacco smoke is nicotine. Smokers who are trying to give up can use patches or gum to provide the nicotine they normally get from cigarettes, reducing the craving to smoke. ) The large surface area is provided by the alveoli. It allows for efficient diffusion of oxygen into the large blood supply, and efficient removal of the waste product, carbon dioxide. Gas Inhaled air Exhaled air nitrogen (78) (79) oxygen 21 16 carbon dioxide 0. 04 other gases (mainly argon) b) It increases in exhaled air because carbon dioxide is produced in respiration. ) Excretion is getting rid of a waste product; carbon dioxide is a waste product. Short distance allows rapid diffusion of oxygen and carbon dioxide.

Blood brings carbon dioxide and takes away oxygen maintaining a diffusion iii) Increases the surface over which diffusion of oxygen and carbon dioxide can occur. 6 Bronchitis is an irritation or infection of the bronchial tree. It blocks normal air flow, so the person suffering from bronchitis has difficulty breathing. Emphysema is a lung disease where the walls of the alveoli break down and fuse together, forming enlarged air spaces with reduced area for gas xchange. The patient cannot get enough oxygen into his blood and has difficulty carrying out any form of exercise.

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