B2.2 - Animal Tissues, Organs and Organ Systems

• What is the digestive system?

  The digestive system is an example of an organ system in which several organs work together to digest and absorb food.
• Enzymes are proteins that have a complex 3D shape. Each enzyme has a region called an active site. The substrate – the molecule or molecules taking part in the chemical reaction – fits into the active site. Once bound to the active site, the chemical reaction takes place.

  In an organism, the active site of each enzyme is a different shape. It is a perfect match to the shape of the substrate molecule, or molecules. This is essential to the enzyme being able to work. One enzyme is therefore specific to one substrate's chemical reaction, or type of chemical reaction.
• Enzymes linked to metabolism

  Metabolism = The sum of all chemical reactions within the body.

  Enzymes are catalysts of reactions. They speed up reactions without having to increase the temperature, so it can happen at body temperature, which is relatively low (37 degrees). Enzymes remain unchanged at the ends of reactions. Enzymes increase metabolism.
• Factors affecting enzyme activity

  Enzyme activity can be affected by a variety of factors, such as temperature, pH, and concentration. Enzymes work best within specific temperature and pH ranges, and sub-optimal conditions can cause an enzyme to lose its ability to bind to a substrate.
• What is denaturing?

  Denaturation defines the unfolding or breaking up of a protein, modifying its standard three-dimensional structure. Proteins may be denatured by chemical action, heat or agitation causing a protein to unfold or its polypeptide chains to become disordered typically leaving the molecules non-functional.
• What is amylase and where is it produced?

  Amylase is a type of carbohydrase that breaks down starch. It is produced in the salivary glands, small intestine and pancreas and found in the mouth and small intestine.
• What is protease and where is it produced?

  Protease is an enzyme that breaks down proteins into amino acids. It's produced in the gastric glands in the stomach, pancreas and small intestine and found in the stomach and small intestine.
• What is lipase and where is it produced?

  Lipase is an enzyme that breaks down fats into fatty acids and glycerol. It's produced in the pancreas and found in the small intestine.
• What do digestive enzymes do?

  Digestive enzymes convert food into small soluble molecules that can be absorbed into the bloodstream.
• What are products of digestion used for?

  State that the products of digestion are used to build new carbohydrates, lipids and proteins. Some glucose is used in respiration.
• What is bile and where is it produced?

  Bile is produced by your liver and stored in the gall bladder. This is released into the small intestine to break down large molecules of lipids into smaller ones. It has a pH of 8.2
• Conditions for increased rate of fat breakdown through lipase

  The alkaline conditions and large surface area increase the rate of fat breakdown by lipase.
• Lung structure

  The lungs are sealed within two airtight pleural membranes. These wrap around the lungs and line the rib cage.The trachea, or windpipe, branches into two bronchi – one bronchus to each lung. Rings of cartilage in the walls of the trachea help to keep it open as air is drawn in. The bronchi split into smaller branches and then into smaller tubes called bronchioles. Each bronchiole ends in a cluster of microscopic air sacs called alveoli.
• What is the heart?

  The heart is an organ that blood around the body in a double circulatory system. The right ventricle pumps blood to the lungs where gas exchange takes place. The left ventricle pumps blood around the rest of the body.
• What is the main artery?

  There are blood vessels throughout your body. The main artery is your aorta, which connects to the left side of your heart. It runs down through your chest, diaphragm and abdomen, branching off in many areas. Near your pelvis, your aorta branches into two arteries that supply blood to your lower body and legs.
• What is the main vein?

  The main vein in your body is the vena cava. The superior vena cava is in the upper right part of your chest. It carries blood from your head, neck, arms and chest back to your heart. The inferior vena cava is near the right side of your diaphragm. It brings blood from your legs, feet, abdomen and pelvis back to your heart. 
• What is a natural pace maker?

  Specialised cells in the right atrium generate electrical signals that make the heart contract independently of the nervous system. These specialised cells act as a natural pacemaker.

  A wave of contraction spreads across the heart - to the left atrium and then to the ventricles. This enables the ventricles to contract together.
• What is an artificial pace maker?

  An artificial pacemaker is a small, battery-operated electronic device implanted in a person's chest that sends out regular, adjustable electrical impulses to produce normal contractions of the heart.

  There are several types of artificial pacemaker, which have electrical leads connected to different chambers of the heart.

  Wires are guided along a vein to the chamber of the heart that needs to be stimulated. The lead extends to the pacemaker, which is fitted between the skin of the upper chest and the chest muscle.
• Arteries structure and adaptations

  Arteries and arterioles have thicker walls than veins and venules because they are closer to the heart and receive blood that is surging at a far greater pressure. Each type of vessel has a lumen—a hollow passageway through which blood flows. Arteries have smaller lumens than veins, a characteristic that helps to maintain the pressure of blood moving through the system. Together, their thicker walls and smaller diameters give arterial lumens a more rounded appearance in cross section than the lumens of veins.
• Veins structure and adaptation

   In other words, in comparison to arteries, venules and veins withstand a much lower pressure from the blood that flows through them. Their walls are considerably thinner and their lumens are correspondingly larger in diameter, allowing more blood to flow with less vessel resistance. In addition, many veins of the body, particularly those of the limbs, contain valves that assist the unidirectional flow of blood toward the heart. This is critical because blood flow becomes sluggish in the extremities, as a result of the lower pressure and the effects of gravity.
• Capillaries structure and adaptations

  Capillaries connect the smallest branches of arteries and veins

  The walls of capillaries are just one cell thick. Capillaries therefore allow the exchange of molecules between the blood and the body's cells - molecules can diffuse across their walls. This exchange of molecules is not possible across the walls of other types of blood vessel.
• Components of blood

  • Plasma is the main component of blood and consists mostly of water, with proteins, ions, nutrients, and wastes mixed in.
  • Red blood cells are responsible for carrying oxygen and carbon dioxide.
  • Platelets are responsible for blood clotting.
  • White blood cells are part of the immune system and function in immune response.
• How to separate blood

  Plasma, the liquid component of blood, can be isolated by spinning a tube of whole blood at high speeds in a centrifuge. The denser cells and platelets move to the bottom of the tube, forming red and white layers, while the plasma remains at the top, forming a yellow layer.
• Functions of plasma

  Some of the molecules found in the plasma have more specialized functions. For example, hormones act as long-distance signals, antibodies recognize and neutralize pathogens, and clotting factors promote blood clot formation at the site of wounds. (Plasma that’s been stripped of its clotting factors is called serum.) Lipids, such as cholesterol, are also carried in plasma, but must travel with escort proteins because they don’t dissolve in water.
• Adaptations of red blood cells

  These characteristics allow red blood cells to effectively perform their task of oxygen transport. Small size and biconcave shape increase the surface area-to-volume ratio, improving gas exchange, while lack of a nucleus makes additional space for hemoglobin, a key protein used in oxygen transport. Lack of mitochondria keeps red blood cells from using any of the oxygen they’re carrying, maximizing the amount delivered to tissues of the body.
• How do platelets work?

  When the lining of a blood vessel is damaged (for instance, if you cut your finger deeply enough for it to bleed), platelets are attracted to the wound site, where they form a sticky plug. The platelets release signals, which not only attract other platelets and make them become sticky, but also activate a signaling cascade that ultimately converts fibrinogen, a water-soluble protein present in blood plasma, into fibrin (a non-water soluble protein). The fibrin forms threads that reinforce the platelet plug, making a clot that prevents further loss of blood.
• Role of white blood cell

  White blood cells, also called leukocytes, are much less common than red blood cells and make up less than   of the cells in blood. Their role is also very different from that of red blood cells: they are primarily involved in immune responses, recognizing and neutralizing invaders such as bacteria and viruses.White blood cells are larger than red blood cells, and unlike red blood cells, they have a normal nucleus and mitochondria. 
• What is CHD?

  The coronary arteries may become blocked by a build-up of fatty material, caused by certain kinds of 'bad' cholesterol. As the fatty material increases, one or more coronary arteries narrow, and can become blocked.

  If a blockage builds up, the amount of oxygen reaching the heart muscle is reduced. A person will develop chest pain, and if left untreated, a heart attack is the result. Heart attacks result in damage to, or death of the heart muscle. Part of the heart muscle, or the whole heart, will die.
• Ways of curing CHD

  Statins are drugs that help to lower cholesterol in the blood. They do this by lowering its production in the liver.

  Coronary arteries that are blocked or have become narrow can be stretched open and have a stent inserted to restore and maintain blood flow. The stent is inserted into a coronary artery in a catheter.
• Impacts on/of illness

  Defects in the immune system mean that an individual is more likely to suffer from infectious diseases. Immune reactions initially caused by a pathogen can trigger allergies such as skin rashes and asthma. Severe physical ill health can lead to depression and other mental illness.
• Lifestyle factors can increase risk at different levels. If you decide to increase your alcohol intake, smoking or worsen your diet, you would increase your risk of non-communicable diseases on a local level. If an area is more impoverished, there may be an increase in alcohol intake and smoking. This would lead to a greater incidence of non-communicable diseases on a national level. If a country is less economically developed, it may have a worse diet, higher rate of smoking and greater alcohol intake on the whole, thus leading to higher rate of non-communicable disease in that nation.
• Impact of lifestyle factors on non communicable disease

  Lifestyle factors can increase risk of non-communicable disease. Lifestyle factors, such as diet, exercise, alcohol intake and smoking, can change the risk of suffering from certain non-communicable diseases
• Causes of tumors

  Benign tumours and malignant tumours result from uncontrolled cell division. Malignant tumour cells are cancers.
• Lifestyle risk factors for various types of cancer including smoking, obesity, common viruses and UV exposure. There are also genetic risk factors for some cancers.
• Iodine test for starch


  Method:

  1. Place one spatula of the food sample on a dish or 1 cm3 if the sample is liquid.
  2. Using a dropper, place a few drops of iodine solution onto the food.
  3. Record any change in the colour of the solution.

  Starch is detected using iodine solution. This turns blue-black in the presence of starch and stays orange if no starch is detected.

  
• Bennedict's test for reducing sugars 


  Place two spatulas of the food sample into a test tube or 1 cm3 if the sample is liquid. Add about 1 cm3 depth of water to the tube and stir to mix.

  1. Add an equal volume of Benedict's solution and mix.
  2. Place the tube in a water bath at about 95°C for a few minutes.
  3. Record the colour of the solution.

  Reducing sugars are detected using Benedict's solution. These include glucose, fructose, and maltose, but not sucrose. Benedict's solution gradually turns from blue to cloudy orange or brick red when heated with a reducing sugar.
• Biuret test for proteins

  1. Place one - two spatulas of the food sample into a test tube or 1 cm3 if the sample is liquid. Add about 1 cm3 depth of water to the tube and stir to mix.
  2. Add an equal volume of potassium hydroxide solution to the tube and stir.
  3. Add two drops of copper sulfate solution and stir for two minutes.
  4. Record the colour of the solution.

  Proteins are detected using Biuret reagent. This turns a mauve or purple colour when mixed with protein.
• Emulsion test for lipids

  1. Place two spatulas of the food sample into a test tube or 1 cm3 if the sample is liquid.
  2. Add 2 cm3 of ethanol to the tube. Cover the end of the tube and shake the tube vigorously.
  3. Allow the contents to settle.
  4. Pour the liquid from the top of the mixture into a test tube half-filled with water.
  5. Record the level of the food and whether the water is cloudy or clear.
  6. A milky-white emulsion forms if the test substance contains lipids.
• What does the plasma carry?

  Nutrients e. G. Glucose, amino acids, proteins, and hormones

  Waste products e. G. Carbon dioxide and Urea

  Antibodies