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| Question | Answer |
| vertebrates | Mammals are vertebrates as they have a backbone. |
| Monotremes | These unusual mammals lay eggs. The echidna and platypus are the only two examples, both of which can be found in Australia. |
| Marsupials | Marsupials are pouched animals. The kangaroo, opossum and koala are examples of marsupials where the young are very immature when born and crawl into a pouch where they attach to a teat to continue their development. |
| Placental Mammals | These mammals have a placenta which attaches to the young in the uterus via the umbilical cord. The placenta supplies them with all the nutrients for development and removes their waste products. |
| Carbohydrates | Carbohydrates are cellulose, starch and sugars. |
| Glucose | Glucose is a monosaccharide or simple sugar. Another monosaccharide is fructose found in fruit and honey. |
| disaccharide | A disaccharide is made up of two monosaccharides joined together. Examples are maltose (glucose and glucose) and sucrose (ordinary table sugar [glucose and fructose]). |
| Polysaccharides | Polysaccharides are made of many single sugars joined together. Examples are starch and cellulose. Both are repeating units (polymers) of glucose molecules. |
| Lipids | Lipids are fats and oils. Lipids are used for ENERGY. They contain about THREE times more energy than the same mass of carbohydrate. |
| Saturated Fats | These fats have a single bond between the carbon atoms in their fatty acids. This makes their melting point higher than unsaturated fats. |
| Unsaturated Fats | These have some double bonds between the carbon atoms in their fatty acids. Their melting point is lower than saturated fats. |
| Proteins | A protein molecule is made up of many amino acids. Proteins are the large molecules that make up the building blocks of cells. They form cell structures. Enzymes are proteins. Proteins control ALL the chemical reactions of cells. |
| Proteins #2 | Proteins are made of amino acids. There are about TWENTY different amino acids. Proteins can be very different from each other because of the combination of the number, type and sequence of amino acids in the protein. |
| Ingestion | Food is taken into the mouth. |
| Digestion | Food particles are being broken down, first by a physical force then by enzymes. |
| Absorption | Small soluble food particles pass through the gut wall into the blood capillaries. |
| Assimilation | The small soluble food molecules enter cells and are used for cell processes such as: -respiration -cell growth -making new cells |
| Egestion | Undigested food which is not used (e.g. fibre) leaves the anus as faeces. |
| A digestive system | A long tube-like system where food is processed along an assembly line of specialised organs producing specific enzymes to break the larger molecules into small soluble ones. |
| Ingestion and Physical digestion. (The Big Picture) | Food is eaten by mammals in big mouthfuls. The big lumps must be broken down into tiny pieces (physical digestion). This increases the surface area of the food bits so enzymes are able to attack the food molecules (chemical digestion) to break the large... -protein molecules to soluble amino acids -carbohydrates to soluble single sugars -lipids to soluble fatty acids and glycerol ...for cells to use for energy and growth. |
| Fact | Some mammals (herbivores) eat plants and some mammals (carnivores) eat the herbivores so they have different adaptations, such as tooth structure and function. |
| Incisors | (I) Incisors are sharp and chisel-like. They are for biting and cutting. |
| Canines | (C) Canines are pointed. They are for tearing. |
| Premolars and Molars | (PM) and (M). Premolars and Molars are flat and have a large surface area for grinding. |
| Fact #2 | The lower jaw moves from side to side which helps incisors to cut through food as well as pulling the ridges of the molars and premolars across each other to grind up food. |
| With the herbivore's teeth | The herbivores teeth move sideways to grind up grass. |
| With the carnivore's teeth | The carnivore's jaw moves up and down making these teeth move like scissors to cut flesh and crack bones. |
| With the Omnivore's teeth | The Omnivore's jaw moves up and down and slightly sideways so these teeth meet to crush and grind food. |
| Fact #3 | Food is chewed and chopped into little pieces by teeth - Physical Digestion |
| Tooth Decay | Occurs when the bacteria in your mouth make acid from your sugary food, this will dissolve the enamel and dentine. |
| Gum Disease (gingivitis) | Occurs when PLAQUE (food and bacteria) gets between the gum and tooth. The plaque rots causing the gum to swell and bleed. |
| Enamel | Makes a hard, biting surface and protects teeth. |
| Dentine | Like bone. |
| Pulp Cavity | Contains blood vessels and nerve endings. |
| Cement | Holds the tooth in the socket of the jawbone. |
| Crown | Top part of tooth that shows above gum. |
| Root | Bottom of tooth that can't be seen, in the gum. |
| Enzymes. The Big Picture | Enzymes are special proteins made by cells which catalyse (speed up) all chemical reactions in living organisms. Chemical digestion of all large food particles requires the use of enzymes which are secreted (oozed out) by various organs as food passes through the digestive system. -Enzymes are specific. One enzyme will only act on one substance because of its shape. -Enzymes are affected by pH. Each specific enzyme will work at its own optimum pH (works the fastest). |
| Digestion in the Mouth | The pH of saliva is between 6.4 and 7.4 (around neutral). Food is broken into small pieces by the teeth - Physical digestion. It is mixed with saliva made by the salivary glands. Press firmly under the soft part of your bottom jaw with the backs of your fingers. Can you feel the saliva pooling under your tongue? |
| Starch and Saliva | Starch is made up of many glucose molecules. Saliva contains an enzyme called amylase which can break down starch into glucose. |
| Saliva contains: | Mucin - a slimy substance that moistens and softens food. Salivary Amylase - an enzyme which breaks down starch to glucose. |
| The Oesophagus | Food doesn't just slip down - it is pushed along by a process called PERISTALSIS. Remember the smooth muscles which work rhythmically. These smooth involuntary muscles squeeze the bolus (ball of food) along the digestive tract. Once the food is swallowed, the digestive system takes over the movement of the bolus (ball of food) towards the anus by a process called 'peristalsis.' |
| Peristalsis | Peristalsis moves the bolus through the digestive system to be acted on by the different organs to complete chemical digestion. This ensures absorption of small soluble molecules and removal of insoluble waste. The bolus moves by contraction of muscles behind it to squeeze the bolus in one direction only. |
| Digestion in the Stomach | The stomach has thick muscular walls which are constantly contracting and relaxing, mixing and stirring up the food with gastric juice to produce a mixture called chime. This is physical digestion. Gastric juice is made by cells in the stomach walls. Gastric juice contains: -protease enzymes to digest proteins. -hydrochloric acid (HCl) The pH of the gastric juice in the stomach is between 1.0 and 2.0 (very acidic) The acid: -kills bacteria -makes the protease work -stops salivary amylase working |
| Fact #4 | Proteins are very large molecules made of amino acid molecules joined by peptide bonds. Digestion by protease = Individual amino acids are very soluble. |
| Renin | Rennin is an enzyme which acts on milk protein. It is produced in the stomachs of baby mammals. This enzyme causes the milk protein to become solid casein. This ensures that the milk remains in the stomach long enough to be acted on by protein digesting enzymes. |
| Digestion in the Duodenum | Both bile and pancreatic juice ensure the completion of digestion. -The ring shaped muscle (at the entrance to your duodenum) relaxes to let food out of your stomach -Gall bladder: this squirts out bile. -Bile does down this tube (bile duct). -Pancreas juice goes down the tube leading from the pancreas -Bile and pancreatic juice meet at the ends of their tubes into the duodenum and mix to break down large insoluble droplets of fat to soluble droplets. |
| Enzymes, Substrate and Products, produced from the Pancreas | The enzyme lipase. Its substrate is fats and lipids. Its products are Three fatty acids and One glycerol. The enzyme Protease. Its substrate polypeptides. Its products are amino acids. The enzymes Amylase and Maltase. Its substrates starch and maltase. Its products are Glucose particles. |
| Describing 'bile' | Bile is a dark green to yellowish brown fluid, that aids the digestion of lipids in the small intestine. When the organism eats, it is discharged into the duodenum. |
| Describing the nature of pancreatic juices. | The clear alkaline digestive fluid is secreted by the pancreas. It contains its digestive enzymes, lipase, protease, amylase and maltase. It is alkaline in nature due to the high concentration of bicarbonate ions. |
| Digestion is complete | Starch = salivary amylase + pancreatic amylase = maltose = pancreatic maltase = glucose Protein = stomach pepsin = polypeptides = pancreatic trypsin = amino acids Lipid = pancreatic lipase = glycerol and 3 fatty acids DNA molecule = pancreatic nuclease = nucleotides |
| Fact #5 | Other important substances in the diet such as water, vitamins and minerals, are already small and soluble so can readily enter cells without the need for digestion. |
| Absorption in the (Very Long) Ileum. The Big Picture | Digestion is complete. All that is left of the food that has been digested is small and soluble so can now be absorbed into the villi by DIFFUSION. Villi are small finger-like projections that resemble the fabric of a towel. The villus contains 'microvilli' which are folded sections of the cell membrane on the villus surface layer. The ileum wall is also folded. This folding with the villi give the ileum a very large surface area for absorption. The surface of the ILEUM is lined with (many) Villi (Singular: Villus). |
| Diagram of a villus | |
| In the Liver | The liver has many functions. Some of them are: -to produce substances that break down fats -to convert glucose into glycogen for storage -to produce urea -to make amino acids (to build proteins) -to filter harmful substances from the blood (e.g. alcohol, poisons) -to store vitamins and minerals (vitamin A, D, K and B12) -to maintain a proper level of glucose in the blood -to produce cholesterol (80%) -Bile is produced all the time in the liver but is stored in the gall bladder until it is stimulated by the presence of food. It is made up of the by-products of the destruction of haemoglobin and cholesterol in the liver. Bile acts as a detergent to break up fats. It is reabsorbed in the hepatic portal vein and returned to the liver. |
| Summary of the digestive system |
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digest_sys (image/jpg)
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| Liver activity | -The Liver acts as the control centre that controls the secretion of some molecules (blood clotting enzymes) but the destruction of others (red blood cells) -The Liver is supplied with blood from two vessels: the Hepatic Artery carries oxygenated blood from the heart (25%) and the Hepatic Portal Vein (60-80%). -Blood leaves the liver via the Hepatic Vein to the heart. |
| Liver #2 | Digestion Product: -Glucose is stored as glycogen -glucose maintains level -amino acids builds protein -vitamins and minerals are stored Actions of liver: -breaks down haemoglobin into bile -breaks down protein into urea -filters harmful substances e.g. alcohol/poisons -destroys substances/cells e.g. poisons, proteins -secretes substances e.g. cholesterol |
| Veins | Veins carry blood towards the heart. Most veins carry deoxygenated blood except for the pulmonary vein from the lungs. Veins are flexible, with thin walls which collapse when they are not full of blood. Veins have a thick outer layer of connective tissue with thin bands of smooth muscles inside. The interior is lined with endothelial cells. Veins carry dark red blood rich in carbon dioxide (except the pulmonary vein that carries bright red oxygen-rich blood from the lungs.) They have valves in the walls of the vessels to prevent back flow. The blood is moved along veins by the contraction of the surrounding muscles. |
| Arteries | -Arteries carry blood away from the heart. -Most arteries carry blood rich in oxygen with the exception of the pulmonary artery, which carries blood rich in carbon dioxide from the heart to the lungs. -Arteries have thick walls of elastic tissue to withstand the high pressure of the blood. Elastic membranes surround the inner layer of endothelial tissue. A smooth muscle layer followed by more elastic tissue surrounds this. On the outside there is a layer of dense connective tissue to prevent rupturing. |
| Arterioles | Small arteries are called arterioles. These carry blood to the individual cells of the tissues by connection with the fine capillary network. |
| Circulation around the body | -Arteries carry blood away from the heart, veins carry blood to the heart. -Veins and arteries are found side-by-side in the body. Many veins and arteries have the same names to indicate that they are related to the same organ. e.g. renal artery and renal vein both are associated with the kidneys. -Heart pumps blood to the body. It pumps deoxygenated blood back to the lungs. |
| Capillaries | Capillaries are the smallest, thinnest and most common vessels in the body. Their walls are one cell thick. There are gaps between the epithelial cells that allow molecules to escape into the tissues. Plasma and its proteins can be transported across the layer. The thin layer allows small molecules to move by DIFFUSION across into the cells or from the cells into the blood. Red cells of the blood can pass in single file. The narrow diameter produces a large surface area to volume ratio that aids diffusion. |
| Diagram of a capillary | |
| Why are the walls of the capillaries so thin? | To allow diffusion of small molecules into and out of the vessel. |
| Why do we need a circulatory system? | -In most animals that are made up of more that two layers of cells, diffusion of substances from the outside into the cells is no longer enough to provide the food the animal needs. The more complicated the animal becomes, the more it needs an efficient transport system around the body. -Humans are very complicated animals so their circulation system is also complicated. -Blood is the liquid part of a transport system designed to circulate food, waste and essential substances including hormones around the body. It also has other functions such as preventing disease and temperature control. |
| What does the blood do? | Functions of the blood: -To carry oxygen from the lungs around the body to cells so they can carry out respiration. -To remove carbon dioxide and water from cells (a product of respiration). -To supply essential molecules to cells for protein production or body metabolism. -To remove waste products of cell metabolism. -To circulate hormones from endocrine glands to their target audience. -To remove heat from muscles and the gut to the skin for release as sweat. -To transport urea waste from the liver to the kidneys. -To transport absorbed food molecules from the gut to the liver and then to the rest of the body. |
| Capillaries | Capillaries are the smallest, thinnest and most common vessels in the body. Their walls are one cell thick. There are gaps between epithelial cells that allow molecules to escape into the tissues. Plasma and its proteins can be transported across the layer. The thin layer allows small molecules to move by diffusion across into the cells or from the cells into the blood. Red cells of the blood can pass in single file. The narrow diameter produces a large surface area to volume ratio that aids diffusion. |
| Why are the walls of the capillaries so thin? | To allow diffusion of small molecules into and out of the vessel. |
| How Food is Delivered to the Cells and Waste Removed. | Food and waste travel in the plasma of the blood and oxygen is carried in the red cells. At the cells, food and oxygen flow out of the capillaries by a process of diffusion. Waste and carbon dioxide flow into the blood by the same method. |
| Why Do We Need a Circulatory System? | -In most animals that are made up of more than two layers of cells, diffusion of substances from the outside into the cells is no longer enough to provide the food the animal needs. The more complicated the animal becomes, the more it needs an efficient transport system around the body. -Humans are very complicated animals so their circulation system is also complicated. -Blood is the liquid part of a transport system designed to circulate food, waste and essential substances including hormones around the body. It also has other functions such as preventing disease and temperature control. |
| What does the blood do? | Functions of the Blood: -To carry oxygen from the lungs around the body to cells so they can carry out respiration. -To remove carbon dioxide and water from the cells (a product of respiration). -To supply essential molecules to cells for protein production or body metabolism. -To remove waste products of cell metabolism. -To circulate hormones from endocrine glands to their target organs. -To removed heat from muscles and the gut to the skin for release as sweat. -To transport urea waste from the liver to the kidneys. -To transport absorbed food molecules from the gut to the liver and then to the rest of the body. |
| Absorption of Glucose | 1. Glucose in ileum 2. Glucose in hepatic vein 3. Liver: Some glucose may be changed to glycogen and stored here. 4. Glucose in blood system. 5. Glucose diffuses into cells. 6. The glucose is used to release energy by respiration. |
| Absorption of Amino Acids | 1. Amino acids in ileum. 2. Amino acids in hepatic portal vein. 3. Amino acids in blood system. 4. Amino acids diffuse into cells. 5. Amino acids used for making new proteins for growth, repair and enzymes. 6. Amino acids not needed by your body are changed into urea. |
| Absorption of Fatty Acids and Glycerol | 1. Fatty acids and glycerol in ileum. 2. Fatty acids and glycerol in lymph vessel. 3. Fatty acids and glycerol go into your blood system. 4. Cells use fatty acids and glycerol for energy. 5. Fat not needed is stored under the skin and around kidneys. |
| Respiration: The Big Picture | Every living organism and every living cell inside it, needs energy to stay alive. This energy is used for movement (even inside the cell), growth, repair, reproduction, excretion and transport. Mammals are warm blooded so they need to carry out respiration to produce body heat. The energy in food must be released by chemical reactions inside cells. This energy release process is called respiration. |
| Aerobic and Anaerobic respiration | Aerobic uses oxygen to release lots of energy. Glucose + Oxygen -> Carbon dioxide + Water + Lots of energy Anaerobic respiration does not use oxygen and only releases a small amount of energy. Glucose -> Lactic Acid + little energy After exercise, the oxygen can break down lactic acid to carbon dioxide and water to release more energy. |
| Cellular Respiration | This is the chemical process of reacting oxygen and sugar together to produce carbon dioxide and water and release energy. It takes place in every living cell of the body in the mitochondria. |
| Respiratory Organ System | The respiratory organ system combines with the circulatory system to deliver the raw materials for respiration to the cells and to remove waste products. |
| Diffusion of Gases | Gases flow from an area of high concentration to an area of low concentration until the concentration on each side is equal. |
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