Organisation B2

• Cell organisation


  -Large multicellular organisms are made up of organ systems.

  -Process of which cells become specialised - differentiation, which occurs during the development of multicellular organisms.

  -Large multicellular organisms have different systems inside them for exchanging + transporting materials.
• Tissues


  -Group of similar cells that work together to carry out a particular function.

  Examples:

  -Muscular tissue - contracts to move whatever its attached to.

  -Glandular tissue - which makes and secretes chemicals like enzymes and hormones.

  -Epithelial tissue - covers some parts of the body such as the gut.
• Organs


  -Group of different tissues that work together to perform a certain function.

  Example: Stomach

  -Muscular tissue - moves stomach wall to churn up food.

  -Glandular tissue - makes digestive juices to digest food.

  -Epithelial tissue - covers outside and inside of the stomach.
• Organ Systems


  -Organ System is a group of organs working together to perform a particular function.

  -Example: Digestive System- Breaks down and absorbs food

  -Glands - produce digestive juices

  -Stomach and Small Intestine - digest food.

  -Liver - Produces Bile

  -Small Intestine - Absorbs soluble food molecules

  -Large Intestine - absorbs water form undigested food - leaving faeces.
• Enzymes


  -Are Catalysts produced by living things.

  -Catalyst is a substance which increases the speed of a reaction, without being change or used up in the reaction.

  -Enzymes are all large proteins - all made up of chains of amino acids. These chains are folded into unique shapes - which enzymes need to do their jobs.
• Enzymes


  -Have special shapes so they can catalyse reactions.

  -Chemical reactions involve things either being spilt apart or joined together.

  -Every enzyme has an active site with a unique shape that fits onto the substance involved in a reaction.

  -They usually only catalyse one specific reaction.
• Enzymes


  -For the enzyme to work - the substrate has to fit into its active site.

  -If the substrate doesn't match the enzymes active site - then the reaction won't be catalysed.
• Enzyme Temperature 


  -Changing the temperature changes the rate of an enzyme-catalysed reaction.

  -With any reaction - a higher temperature increases the rate at first.

  -However if it gets too hot - some bonds holding the enzyme together break.

  -This changes the shape of enzymes active site do the substrate won't fit any more - the enzyme then denatures.

  -All enzymes have an optimum temperature that they work best at.
• Enzyme pH


  -If the pH is too high or low - it interferes with the bonds holding the enzyme together.

  -This changes the shape of the active site and dentures the enzyme.

  -All enzymes have an optimum pH that they work best at - often neutral pH 7.

  -However, pepsin is an enzyme used to break down proteins in stomach and works best at pH 2 - means its well suited to the acidic conditions there.
• Investigating Enzymatic Reactions


  -The enzyme amylase catalyses the breakdown of starch to maltose.

  -Easy to detect starch using iodine solution - if starch is present iodine solution changes from browny-orange to blue-black.
• Investigating how pH affects amylase activity 


  1.Put a drop of iodine solution into every well of a spotting tile.

  2.Place a Bunsen burner on a heat-proof mat, and a tripod and gauze over it. Put a beaker of water on top of tripod and heat water until it's 35°C. Try to keep temperature of water constant throughout the experiment.

  3.Use syringe to add 1cm³ of amylase solution and 1 cm³ of buffer solution with pH of 5 to boiling tube - using test tube holders put tube into beaker of water and wait five minutes.
• Investigating how pH affects amylase activity


  4.Next, use different syringe and add 5cm³ of starch solution to boiling tube.

  5.Immediately mix contents of the boiling tube and start a stop clock.

  6.Use continuous sampling to record how long it takes for the amylase to break down all of the starch - to do this use dropping pipette to take fresh sample from boiling tube every 30 seconds and put drop into a well. When iodine solution remains browny orange - starch is no loner present.
• Investigating how pH affects amylase activity


  7. Repeat the whole experiment with buffer solutions of different pH values to see how pH affects the time taken for the starch to be broken down.

  8.Remember to control any variable each time - such as concentration and volume of amylase solution, to make it a fair test.
• Calculate Rate of Reaction

  $Rate =$$1000 / time$
• Enzymes and Digestion 


  -Digestive Enzymes break down big molecules such as starch, proteins and fats.

  -They're too big to pass through walls of the digestive systems - so digestive enzymes break them down into smaller ones like sugars, amino acids, glycerol and fatty acids.

  -These smaller, soluble molecules can pass easily through the walls of the digestive system - allowing them to be absorbed into the bloodstream.
• Carbohydrases


  -They convert carbohydrates into simple sugars.

  -Amylase is an example of a carbohydrase - breaks down starch.

  -Amylase is made in three places: The salivary glands, the pancreas and the small intestine.
• Proteases

  -They convert proteins into amino acids.

  -Proteases are made in three places: The stomach (called pepsin there), the pancreas and the small intestine.
• Lipases


  -Convert lipids into glycerol and fatty acids.

  -Made in two places: The pancreas and the small intestine.
• Products of digestion 


  -The body makes good use of the products of digestion. They can be used to make new carbohydrates, proteins and lipids. Some of the glucose that's made is used in respiration.
• Bile


  -Bile is produced in the liver - stored in the gall bladder before its released into the small intestine.

  -The hydrochloric acid in the stomach makes the pH too acidic for enzymes in the small intestine to work properly.

  -Bile is alkaline - it neutralises the acid and makes conditions alkaline. The enzymes in the small intestine work best in these alkaline conditions.

  -It also emulsifies fats - gives them a bigger surface area of fat for the enzyme lipase to work on, making its digestion faster.
• Breakdown of Food


  -Enzymes used in the digestive system are produced by specialised cells in glands and in the gut lining.

  -Different enzymes catalyse the breakdown of different food molecules.
• Salivary glands


  -These produce amylase enzyme in the saliva.
• Liver


  -Where bile is produced - bile neutralises stomach acid and emulsifies fats.
• Gall Bladder


  -Where bile is stored, before it's released into the small intestine.
• Large intestine 


  -Where excess water is absorbed from the food.
• Rectum


  -Where the faeces (made up of indigestible food) are stored before being released through the anus.
• Small Intestine


  -Produces protease, amylase and lipase enzymes to complete digestion.

  -This is also where the digested food is absorbed out of the digestive system into the blood.
• Pancreas


  -Produces protease, amylase and lipase enzymes. It released these into the small intestine.
• Stomach

  -Pummels the food with its muscular walls.

  -Produces the protease enzyme, pepsin.

  -Produces hydrochloric acid: To kill bacteria and to give the right pH for the protease enzyme to work (pH 2 - acidic)
• Food Tests (Preparing Food Sample)


  -Get a piece of food and break it up using a pestle and mortar.

  -Transfer the ground up food to a beaker and add distilled water.

  -Give mixture a good stir with glass rod to dissolve some of the food.

  -Filter solution using funnel lined with filter paper to get rid of solid bits of food.
• Benedicts Test (Testing for Sugars)

  -You test for reducing sugars in the Benedict's test.

  1.Prepare a food sample and transfer 5cm³ to a test tube.

  2.Prepare a water bath that's set to 75℃.

  3. Add 10 drops of Benedict's solution to test tube - using a pipette.

  4. Place test tube in water bath using test tube holder and leave in for 5 minutes - making sure tube is pointing away from you.

  5. If food sample contains reducing sugar - solution in test tube changes from normal blue colour to green, yellow or brick red (depending how much sugar is in the food)
• Iodine Solution (Testing for Starch)


  -Make a food sample and transfer 5cm³ of your sample to a test tube.

  -Add a few drops of iodine solution and gently shake tube to mix contents.

  -If sample contains starch - colour of solution changes from browny-orange to black or blue-black.
• Biuret Test (Testing for Proteins)


  -Prepare sample of food and transfer 2cm³ of your sample to a test tube.

  -Add 2cm³ of biuret solution to the sample and mix the contents of the tube by gently shaking it.

  -If the food sample contains protein - solution will change from blue to purple. If no protein is present - solution will stay blue.
• Sudan III Test (Testing for lipids)


  -Prepare a sample of food being tested (don't need to filter it). Transfer 5cm³ into a test tube.

  -Use pipette to add 3 drops of the stain solution to the test tube and gently shake the tube.

  -Sudan III solution stains lipids - if sample contains lipids the mixture will separate into two layers and the top layer will be bright red.

  -If no lipids are present there will be no separate layers formed.
• Lungs


  -Lungs are found in the thorax - the thorax is the top part of your body.

  -It's separated from the lower part of the body by the diaphragm.

  -Lungs are like pink sponges, protected by the ribcage - surrounded by the pleural membranes.

  -Air that you breathe in goes through the trachea - this splits into two tubes called bronchi - one going to each lung.

  -Bronchi split into progressively smaller tubes called bronchioles.

  -Bronchioles end at the alveoli - where gas exchange takes place.
• Alveoli 


  -Carry out gas exchange in the body.

  -Blood passing next to alveoli has just returned from kings from rest of body - contains lots of carbon dioxide and very little oxygen.

  -Oxygen diffused out of alveolus (high concentration) into the blood (low concentration).

  -Carbon dioxide diffuses out of the blood (high concentration) into the alveolus (low concentration) to be breathed out.
• Alveoli 


  -When blood reaches body cells oxygen is released from the red blood cells (high concentration) and diffuses into body cells (low concentration).

  -At the same time, carbon dioxide diffuses of of the body cells (high concentration into the blood (low concentration) - then carried back to the lungs.
• Circulatory System 


  -Made up of the heart, blood vessels and blood.

  -Humans have double circulatory system (two circuits joined together).

  -In first one, right ventricles pumps deoxygenated blood to lungs to take in oxygen - blood then returns to heart.

  -In second one, left ventricles pumps oxygenated blood around all other organs of the body - blood gives up its oxygen at the body cells and the deoxygenated blood returns to the heart to be pumped out to the lungs again.
• Heart


  -The heart is a pumping organ that keeps blood flowing around the body - walls of the heart are mostly made of muscle tissue.

  -Heart has valves to ensure that blood flows in the right direction - they prevent it flowing backwards.

  -Heart has fours chambers: right atrium, right ventricle, left atrium and left ventricle - which pump blood around.
• Heart


  1.Blood flows into the two atria from the vena cava and the pulmonary vein.

  2.The atria contract, pushing the blood into the ventricles.

  3.The ventricles contract - forcing the blood into the pulmonary artery and the aorta, and out of the heart.

  4.Blood then flows to the organs through arteries and returns through veins.

  5.The atria fill again and the whole cycle starts over.