B3 - Living Together - Food and Ecosystems

• Enzymes are made from protein so coded for by DNA
• The enzyme is specific to the substrate it acts on, which means that there will be many different types of enzymes in an organism.
• Each type of enzyme has its own shape and active site where the substrate fits into
• An enzyme's shape can change when it binds with the substrate, this causes a chemical reaction to occur
• An example of this is amylase, which breaks down starch into glucose molecules.
• Lipases break down fats into fatty acids and glycerol.
• Enzymes are catalysts (speeds up) for reactions
• A denatured enzyme means that the active site is no longer able to bind to the substrate due to temperature or pH not being optimum.
• The rate of an enzyme-controlled reaction increases as more enzymes are added because there will be more active sites available for the substrates to bind to.
• Increasing the concentration of the substrate also increases the rate of an enzyme controlled reaction because there will be more substrate molecules available to bind to the active sites on the enzymes.
• If the temperature is too high, the enzyme becomes denatured and loses its shape so cannot function properly anymore.
• If too many substrates are present compared to the number of enzymes, then some substrates may have to wait until they can bind to an active site on an enzyme. This reduces the overall speed of the reaction.
• If the substrate concentration becomes too high, it can become saturated with enzymes meaning all active sites have been filled so increasing the substrate concentration further won't increase the rate any further.
• Photsynthesis equation


  Carbon dioxide + water --> Glucose + oxygen
• Glucose is used by plants for respiration or stored as starch
• Photosynthesis is an endothermic reaction
• Photsynthesis occurs in the chloroplasts
• Osmosis is the movement of water molecules from high concentration to low concentration and requires a partially permeable membrane but does not need an energy supply (passive process)
• Diffusion is the movement of molecules of gas and liquid from a high concentration to a low concentration and does not require a cell membrane or energy supply (passive process)
• Active transport is the movement of nitrates and glucose from low concentration to high concentration and requires a cell membrane and ATP (energy) so is an active process
• An example of osmosis is in root hair cells uptake
• An example of diffusion is in leaves, alveoli (CO2 in, CO2 out) and in the stomata
• An example of active transport is when roots take up nitrates
• The xylem is made up of dead cells in a continious tube and. It transports minerals and water from the roots and too the leaves and flowers which travels in one direction and is known as transpiration.
• The phloem is made up of living cells and has companion cells. It transports sugars from the leaves or storage system to the root or developing fruit in both directions. This process is known as translocation
• Energy flow diagrams show where energy comes into an ecosystem and where it goes out of the ecosystem. They also show what happens to the energy within the ecosystem.
• In a food web there are many interconnected food chains that show how energy moves between all the species in an ecosystem.
• A food chain shows how energy flows through different organisms in an ecosystem.
• Food webs show all the different ways organisms interact with each other and can be shown using lines connecting the producers and consumers. This allows us to see who relies on whom.
• A food chain shows how organisms are linked by feeding relationships. The arrows point towards the consumer that eats the producer. A food web shows all the different ways that organisms can be eaten.
• Bioaccumulation is the process by which a substance is taken up by a living organism and stored in its tissues and accumulates as it moves up the food chain
• The process of eutrophication is when excess nitrogen from fertiliser are added to a body of water which causes extra growth of algae which then blocks off light so plants cannot photosynthesise thus a lack of oxygen which causes the ecosystem of the body of water to die
• The carbon cycle is the movement of carbon from the atmosphere to the biosphere and back to the atmosphere through, respiration, decomposition, combustion and photosynthesis
• The water cycle is the continuous movement of water from the atmosphere to the ground and back to the atmosphere through an uptake by roots then transpiration or precipitation which causes a run off then evaportation from the new formed body of water
• Equation for capture mark recapture

  Estimated population = Number of individuals x Number of individuals captures/number of recaptured individuals that have the mark
• Iodine solution tests for starch. To carry out the test, you need to put iodine on the sample. The results are that if it is positive, the colour would be black and if it is negative, it would be yellow/brown.
• Benedict's solution tests for reducing sugars. To carry out the test, you need to put solution for testing in the test tube then add Benedict's solution and shake gently to mix. Heat it for 15 minutes at 95 degrees with a heat baths. The results are that if positive, the colour would be red/brown and if negative, the colour would be dark blue
• Buiret's solution tests for protiens. To carry out the test, you need to put solution that needs to be tested in a test tube then add Buiret's solution by carefully dropping it down the side then shake gently to mix. The results are that if it is positive, the colour would be lilac and if it is negative then it would be blue
• Ethanol tests for lipids. To carry out the test, you need to add solution needing to be tested and ethanol then seal and shake. After add it in a test tube with water. The results are that if it is positive then the colour would be white and if it is negative then it would be clear