Organisation Flashcards
What is Meant by Tissue, Organ and Organ System
Tissue- a group of cells with a similar function.
Organ- a group of tissues working together for a specific function.
Organ System- a collection of organs working together to carry out a function.
Describe the Purpose of Digestion
-Food molecules such as carbohydrates, lipids and proteins are too large to be absorbed directly into the bloodstream.
-Because of this, they have to be digested.
-In digestion, enzymes are used to break down large food molecules into smaller soluble molecules.
-These smaller molecules can then be absorbed into the bloodstream
List the Parts of the Digestive System
-Mouth
-Salivary Glands
-Oesophagus
-Liver
-Stomach
-Pancreas
-Small Intestine
-Large Intestine
-Appendix
-Anus
Describe the Function of the Mouth and Salivary Glands in the Digestive System
-Food is chewed in the mouth and mixed with saliva.
-The enzymes in the saliva begin to digest starch into smaller sugar molecules.
Describe the Function of the Oesophagus in the Digestive System
The oesophagus carries food from the mouth to the stomach.
Describe the Function of the Stomach in the Digestive System
-In the stomach, the food is churned into a fluid. This increases the surface area for enzymes to digest,
increasing the rate of digestion.
-In the stomach, hydrochloric acid helps the enzymes digest the proteins by providing the optimum pH.
-Protein molecules start their digestion in the stomach.
Describe the Function of the Pancreas and Liver in the Digestive System
-The pancreas releases fluid into the small intestine.
-Pancreatic fluid contains enzymes which continue with the digestion of starch and proteins. The enzymes also start the digestion of lipids.
-The liver releases bile into the small intestine.
-Bile emulsifies lipids. It also neutralises the acid released from the stomach. This is important as the enzymes which operate in the small intestine work best under alkaline conditions.
Describe the Function of the Small Intestine in the Digestive System
-The walls of the small intestine releases enzymes. These continue the digestion of proteins and lipids.
-In the small intestine, the products of digestion are absorbed into the bloodstream. This takes place
by diffusion or by active transport.
Describe the Function of the Large Intestine in the Digestive System
-The role of the large intestine is to absorb the water contained in the fluid passing through the digestive system.
-As the fluid passes through the large intestine, it turns into solid faeces.
Describe what Happens to the Products of Digestion Once they are Absorbed into the Bloodstream
-Once the products of digestion are absorbed into the bloodstream, they are carried off to the body cells.
-Here the molecules are used to build new carbohydrates, lipids and proteins.
-Also, some of the glucose is used to release energy in respiration.
What is an Enzyme
-Enzymes are biological catalysts that catalyse specific reaction in living organisms.
-They are large protein molecules.
What is Meant by the Lock and Key Theory
-The lock and key theory states that enzymes are specific because the substrate must fit perfectly into the active site.
-If a substrate does not fit perfectly into the active site, then the enzyme will not be able to break it down.
How do Enzymes Break Down Foods
-The substrate binds to the active site of the enzyme.
-This is because the shape of the active site and substrate are complementary
-Enzymes catalyse the breakdown of the substrate.
-The products are then released from the active site.
Describe the Structure, Function and Products of Proteins
-Proteins build up cells and tissues. They are also the basis of all enzymes.
-They are long chains of amino acids.
-Proteins are broken down by protease (produced in the pancreas, stomach and small intestine) into amino acids.
-Once the amino acids have been absorbed into the bloodstream, they are carried to the body cells. The body cells join the amino acids back together in a different order to make human proteins.
Describe the Structure, Function and Products of Carbohydrates
-Carbohydrates provide energy for cell respiration.
-A simple chain is two glucose molecules joined together. A complex chain is a long chain of simple carbohydrates joined together.
-Carbohydrates are broken down by carbohydrase (produced in the mouth pancreas and small intestine) into glucose or fructose.
Describe the Structure, Function and Products of Lipids
-Lipids are an energy source. they are used in cell membranes and hormones.
-They are made up of three fatty acid molecules joined to a molecule of glycerol.
-Lipids are broken down by lipase (produced in the pancreas and small intestine) into glycerol and fatty acids.
Describe the Purpose of Amylase as a Digestive Enzyme
-Amylase is made in the pancreas, small intestine and salivary glands.
-It works in the mouth, small intestine and stomach.
-It catalyses the chemical reaction breaking starch down into sugars.
Describe the Purpose of Bile
-Bile is produced in the liver and is stored in the gall bladder. It increases the rate of lipid digestion.
-Bile emulsified lipids. This means that bile converts large lipid droplets into small lipid droplets. This increases the surface area for the enzyme lipase to act on which increases the rate of lipid breakdown.
-The enzyme lipase works best in alkaline conditions. However, the stomach releases acidic fluid directly into the small intestine.
-Because bile is alkaline, it neutralises the stomach acid, allowing the lipase in the small intestine to work effectively.
Explain why it is Difficult to Digest Fat When the Gall Bladder is Blocked
-Less bile reaches the small intestine so there is less emulsification of fat.
-This means there is a smaller surface area for lipase to break down fat.
-The pH of the small intestine is also not neutralised so lipase is not at its optimum pH to break down fat.
Describe the Effect of Temperature on Enzymes
-As the temperature increases, the reaction gets faster as the activity of the enzyme increases. At higher temperatures, the enzyme and substrate are moving faster.
-This means that there are more collisions per second between the substrate and the active site.
-At the optimum temperature, the enzyme is working at its fastest rate and there are the maximum frequency of collisions between the substrate and the active site.
-Past the optimum temperature, the enzyme’s activity falls to zero. This is because at high temperatures the enzyme molecules vibrate and the active site changes shape. Scientists say that the enzyme is denatured.
-Now the substrate no longer fits perfectly into the active site so the reaction stops.
Describe the Effect of pH on Enzymes
-If the pH is more acidic or more alkaline than the optimum pH for an enzyme, then it interferes with the bonds holding the enzyme together.
-This changes the shape of the active site and at extreme pH values, the enzyme may become denatured
-Because the active site has changed shape, it no longer fits the substrate perfectly so the enzyme does not work e.g. amylase can longer digest starch so the rate of digestion decreases.
-Stomach enzymes often work better in acidic conditions whereas enzymes in the small intestine work better in alkaline conditions.
Why are Safety Goggles an Essential in the Food Tests Required Practical
-This required practical uses a number of chemicals which are hazardous e.g. Benedict’s solution and iodine which are irritant.
-Therefore we need to wear safety goggles to protect our eyes from splashes.
Describe a Method to Prepare a Food Sample in the Food Tests Required Practical
-First, grind the food sample into a paste using a pestle and mortar and a small amount of distilled water.
-Transfer the paste to a beaker. Add more distilled water and stir. Stir the sample to ensure that the molecules present in the food dissolve in the distilled water.
-Next, pass the solution through a filter to remove any undissolved food particles. These could make the sample cloudy and make any colour changes difficult to see.
-At this point, the solution can be tested for the the chemicals present in the sample.
Describe a Method to Test for Starch in the Food Tests Required Practical
-First, place a small volume of the food solution into a test tube.
-Then, add several drops of iodine solution.
-If starch is present in the food sample, the iodine would turn from an orange colour to a blue-black colour.
Describe a Method to Test for Reducing Sugars (Glucose) in the Food Tests Required Practical
-First, add several drops of Benedict’s solution to the food solution.
-Now, place the test tube into a beaker and half fill the beaker with hot water from kettle. Leave the test tube in the hot water for five minutes.
-If reducing sugars are present in the food sample, the Benedict’s solution would turn from a blue colour to:
-green if only a small amount of sugar is present
- yellow if more sugar is present
-brick red if there is a lot of sugar present
Describe a Method to Test for Proteins in the Food Tests Required Practical
-First, place a small volume of the food solution into a test tube.
-Then, add several drops of Biuret solution to the food solution.
-If proteins are present in the food sample, the Biuret solution would turn from a blue colour to a lilac colour.
Describe a Method to Test for Lipids in the Food Tests Required Practical
-When preparing the food sample for lipids, do not filter the food solution. This is because any lipids present will be
absorbed onto the filter paper.
-To test for lipids, add a small amount of ethanol and a small amount of distilled water to the food solution.
-Then, shake the test tube.
-If lipids are present in the food sample, a white cloudy suspension forms.
Describe a Method for the Effect of pH on Amylase Required Practical
-Placer one drop of iodine into each well of a spotting tile.
-Now, set up 3 test tubes, one with 2cm^3 starch solution, one with 2cm^3 amylase solution and one with 2cm^3 pH 5 buffer solution. Leave the test tubes in a water bath for 10 minutes.
-Combine the three solutions into one test tube and mix with a stirring rod. Return the solution to a water bath and start a stop watch. At this point the amylase will start to break down the starch.
-After thirty seconds, use a syringe to transfer one drop of the solution to the first well in the spotting tile containing iodine solution.
-Continue taking samples every thirty seconds, moving onto the next well in the spotting tile until there is no more starch present. This is when the iodine remains orange and does not turn blue-black.
-Record the the well number where the iodine first remained brown then repeat the experiment with different pH buffers.
What is Meant by a Buffer Solution
-A buffer solution has a set pH which is decided when it is made.
-Buffer solutions are used in biology to control the pH.
Why is it Important to Leave the Test Tubes in a Water Bath for 10 Minutes in the Effect of pH on Amylase Required Practical
-By leaving our test tubes in the water bath for ten minutes, we make certain that the solutions in the test tubes reach the same temperature as the water bath.
-This means that all solutions are the same temperature.
Why will the Iodine Initially Turn Blue-Black in the Effect of pH on Amylase Required Practical
-Initially the colour of the iodine solution will turn blue / black.
-This is because the amylase will not have had time to break the starch down.
-Because our solution still contains a high level of starch, this will turn the iodine blue / black.
Why is Taking Sample Every Thirty Seconds a Problem in the Effect of pH on Amylase Required Practical
-Because we are taking samples every thirty seconds, it is only possible to state when the starch was all broken down to the nearest thirty seconds.
-This makes our experiment inaccurate.
-A way to address this is to take samples more frequently, for example every ten seconds.
Why is Observing when the Reaction has Finished a Problem in the Effect of pH on Amylase Required Practical
-It can be difficult to see when the reaction has finished as the blue / black colour of the iodine solution tends to show a gradual change.
-There is no clear cut-off point where the iodine solution stays orange showing that the starch has all been broken down.
-A way to address this problem is by asking several people to look at the spotting tile and decide when the reaction has completed. A mean can be taken of their answers.
Why is it Important that the Small Intestine is Long
-The length of the small intestine in humans is 5 metres.
-Because the human small intestine is so long, this provides a very large surface area for absorption of the small soluble molecules produced in digestion.
-Also, it takes several hours for the molecules to make
their way down the small intestine.
-This means that there is plenty of time for the molecules to be absorbed into the bloodstream.
Describe how the Small Intestines are Adapted as an Effective Exchange Surface
-Villi and microvilli massively increase the surface area for the absorption of the products of digestion.
-The good blood supply rapidly takes away the molecules that are absorbed into the bloodstream. This makes the concentration gradient very steep, which makes diffusion faster.
-The thin membrane on the villi make the pathway for diffusion very short. This increases the rate of diffusion.
Why do the Cells Lining the Surface of the Villi Have a Large Number of Mitochondria.
-The cells lining the surface of the villi have a large number of mitochondria.
-This is because they use active transport to move certain molecules from the small intestine into the bloodstream.
-Active transport requires energy from respiration. The large number of mitochondria ensure that there is always a large
amount of energy available for active transport.
Describe the Key Structures in the Lungs and Their Functions
Trachea- carries air down the throat
Rings of Cartilage- prevent the trachea from collapsing when inhaling
Bronchi- one bronchus carries air down into each lung
Bronchioles- these tiny tubes carry air down to the alveoli
Alveoli- these are where gases diffuse in and out of the bloodstream
Describe how the Lungs are Adapted as an Effective Exchange Surface
-Each lung contains millions of alveoli: This means that there is a huge surface area to volume ratio for diffusion of gases in and out of the blood so the rate of diffusion is high.
-Alveoli have very thin walls. This makes the diffusion pathway very short, which increases the rate of diffusion.
-Alveoli have a very efficient blood supply. This ensures that once oxygen diffuses into the blood, it is rapidly removed. This means that the concentration gradient for oxygen is very steep, which keeps the rate of diffusion high.
-The same applies to carbon dioxide. By constantly providing more carbon dioxide, thisex ensures the maximum rate of diffusion from the bloodstream into the air.
Describe the Exchange of Gases when Breathing
-When breathing in, oxygen-rich air moves into the lungs. This maintains a steep concentration gradient with the blood.
-Oxygen continually diffuses into the bloodstream though the gas exchange surfaces on the alveoli.
-When breathing out, carbon dioxide-rich air is removed from the lungs.
-This maintains the concentration gradient so that carbon dioxide continually diffuses out of the bloodstream into the air of the lungs.
Describe how the Lungs Take in Air
-When breathing in, the intercostal muscles contract. As this happens, the ribs move up and down, the diaphragm contracts and the volume of the chest increases.
-The increased volume means there is lower pressure in the chest.
-Air outside the chest is now at a higher pressure than inside so air is drawn into the lungs.
Describe how the Lungs Remove Air
-When breathing out, the intercostal muscles relax. As this happens, the ribs fall, the diaphragm relaxes and the volume of the chest decreases.
-The decreased volume means there is higher pressure in the chest.
-Air inside the chest is now at a higher pressure than outside so air is forced out of the lungs.
What is Meant by a Single Circulatory System
-Fish have a single circulatory system.
-This is because the blood only passes through the heart once per cycle before going to the gills to collect oxygen and then on to the body organs.
Describe what Happens to Blood when it Passes Through the Gills and Organs of a Fish
-When the blood passes through the gills, the red blood cells collect oxygen. The blood is now oxygenated.
-When the blood passes through the organs, the red blood cells give up their oxygen.
-The oxygen diffuses from the blood to the cells of the organs where it is used for respiration. This means that the blood becomes deoxygenated.
Describe the Disadvantage of a Single Circulatory System
-The main disadvantage of the single circulatory system is that the blood loses pressure as it passes through the gills.
-This means that the blood travels relatively slowly from the gills to the organs.
-Because of this, the blood cannot deliver oxygen rapidly to the organs.
