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Life Processes (8 life processes (Movement (Actions of muscles in animals…

- - - - Enzymes in the human body work best at body temp. (37°c), and denature at 40°c
      - Optimum temperature – the temp. the enzyme works best at
      - Higher temperatures
        => molecules have more KE
        => more collisions
        => more frequent reactions
      - Enzymes are proteins
        –> proteins are broken down by heat
        => above the optimum temperature, enzymes are denatured
        –> changes the shape permanently of the active site
      - Practical: how temperature affects the activity of amylase
        
        Amylase: breaks starch into maltose
        
        Speed at which starch disappears = measure of amylase activity
        
        Method:
        
        Place 5cm3 amylase solution and 5cm3 starch suspension in a beaker of water at 20°c for 5 minutes and record the temperature
        
        Pour the amylase solution into the starch solution
        
        Put spots of iodine solution on a spotting tile
        
        Immediately take a small sample with a pipette and add to the first drop of iodine. Record colour
        
        Repeat every 30 seconds until the iodine solution remains yellow
        
        Repeat the whole experiment with different temperature water baths from 20°c to 60°c
        
        Rate of reaction = volume of starch / time
    - - Enzymes work best at their optimum pH
      - Either side of the optimum pH, the active site is changed so the substrate doesn't fit as well
        –> bell curve on a graph
      - Not permanent
      - Most enzymes work best at pH 7 – neutral
        –> pepsin works best at pH 2 – adapted to work in stomach acid
    - - Buffer solution: solutions of salts that resist changes in pH
        –> different solutions can be prepared for different pH values
        –> Useful for finding the affect of pH on enzyme activity
      - Catalase: breaks hydrogen peroxide (toxic) into water and oxygen
      - Method:
        
        Chop a large potato into small pieces and place in a blender with an equal volume of distilled water
        
        Blend potato and water to release the catalase from cells. Let potato debris settle and remove the liquid extract above
        
        Place 5cm3 of the extract and 5cm3 of a buffer solution in a boiling tube
        
        Leave for 5 minutes, then add 5cm3 of 5% hydrogen peroxide solution
        
        Fit a bung and delivery tube into a beaker of water
        
        Count the bubbles of oxygen gas produced in the first minute
        
        Repeat experiment with different buffer solutions
      - number of oxygen bubbles in the first minute = initial reaction rate
- - - - Nucleus present in all cells except for a few
        eg. red blood cells (doesn't live long), xylem vessels (dead)
      - Controls the activities of the cell
      - Contains chromosomes, which carry genetic material
    - - Structures inside a cytoplasm KA organelles
      - Living material that makes up a cell
      - Chemical reactions controlled by enzymes
    - - Very small – a cell can contain thousands
      - Synthesises proteins, eg. enzymes
    - - AKA cell surface membrane
      - Is selectively permeable
      - Controls the movement of substances into and out of the cell
    - - Carry out some of the reactions of respiration
      - Most of the energy from respiration is released in the mitochondria
  - - - A layer of non-living material found outside the cell membrane
      - Mainly made of cellulose
      - Helps the cell keep its shape – pushes back against water pressure
      - Freely permeable
    - - Large central space surrounded by a membrane
      - Filled with cell sap – store of dissolved sugars, mineral ions and other solutes
      - Permanent feature of a plant cell (there are small, temporary vacuoles present in animal cells)
    - - Absorb light energy to make food as part of photosynthesis
      - Contain chlorophyll – a green pigment
      - Non-green parts of the plant have no chloroplasts, eg. flowers, roots, woody stems
- - - - Steeper concentration gradient => faster diffusion
      - Larger surface area to volume ratio => faster diffusion
      - Greater distance => slower diffusion
      - Higher temperature => faster diffusion
    - - Agar: a jelly used for growing culture of bacteria
      - Potassium permanganate is purple
        –> reaction with HCl => loses purple colour
      - Method:
        
        Prepare a petri dish with 2cm deep agar jelly, dyed purple with potassium permanganate
        
        Cut three different-sized cubes out of the jelly (0.5cm, 1cm,2cm) – different surface area : volume
        
        Drop into a beaker of dilute HCl and record the time taken for each cube to turn colourless
  - - - eg. villi of the small intestine, alveoli of lungs
      - eg. spongy mesophyll of leaves, root hairs
- - - - Certain genes become switched on/off
      - eg. nerve cell, sperm cell, leaf palisade cell, guard cells, xylem vessel
  - - - Digestive system
      - Gas exchange system
      - Circulatory system
      - Excretory system
      - Nervous system
      - Endocrine system
      - Reproductive system
  - - - Embryonic stem cells: found in the early stages of development in the embryo – can differentiate into any type of cell
      - Adult stem cells: found in certain adult tissues, have lost the ability to differentiate into any type of cell but can form a number of specialised tissues