B4 The processes of life

Chemical reactions in living things
1. Processes of all living things
  1. Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition
  2. Processes of plants
    1. Cytoplasm
      1. Contains a biological chemistry factory
  3. Enzymes
    1. Speed up chemical reactions
    2. Work best at their optimum temperature, this is why as humans we must keep homeostasis our bodies at 37 degrees.
    3. If the temperature is too high the enzyme becomes denatured
      1. AN ENZYME CANNOT BE KILLED IT BECOMES DENATURED
    4. The rate of reaction increases with the temperature until the enzyme become denatured
    5. Enzymes are specific
      1. Each enzyme has a specific active site, and each active site has a specific substrate that fits, like a lock and key.
        The important part of an enzyme is called the active site. This is where specific molecules bind to the enzyme and the reaction occurs.
        When an enzyme becomes denatured the active site changes and the enzyme substrate complex stops working
      2. The shape of the active site is affected by pH. This is why enzymes will only work at a specific pH, as well as a specific temperature. Change the pH and the enzyme stops working.
  4. Active Transport
    1. Active transport is the process by which dissolved molecules move across a cell membrane from A LOW CONCENTRATION TO A HIGH CONCENTRATION
    2. In active transport, particles move against the concentration gradient - and therefore require an input of energy from the cell.
    3. In humans, active transport takes place during the digestion of food in the small intestine. Carbohydrates are broken down into simple sugars such as glucose. The glucose is absorbed by active transport into the villi, to be passed into the bloodstream and taken around the body.
How Plants make food
1. Photosynthesis
  1. Photosynthesis is a process used by plants in which energy from sunlight is used to convert carbon dioxide and water into molecules needed for growth. These molecules include sugars, enzymes and chlorophyll.
  2. Light energy is absorbed by chlorophyll
  3. Carbon dioxide + water ---------------------------> glucose + oxygen Light energy
  4. 6CO2 + 6H2O ---------------->C6H12O6 + 6O2 Light energy
  5. Glucose made by photosynthesis, is made up of carbon, hydrogen and oxygen atoms
    1. It can be converted into chemicals required for growth of plant cells, e.g. cellulose
    2. It can be converted into starch, a storage molecule, that can be converted back into glucose when the plant needs it.
    3. It can be broken down during the process of respiration, releasing energy stored in glucose molecules
  6. Chloroplasts - containing chlorophyll and enzymes needed for reactions in photosynthesis. Nucleus - containing DNA carrying the genetic code for enzymes and other proteins used in photosynthesis Cell membrane - allowing gas and water to pass in and out of the cell while controlling the passage of other molecules Vacuole - containing cell sap to keep the cell turgid Cell wall - strengthens the cell Cytoplasm - enzymes and other proteins used in photosynthesis made here
2. Diffusion
  1. Diffusion goes from a high concentration, to a low concentration
    1. Going down the concentration gradient
    2. e.g. how the smell of cooking goes from one room to another
  2. Happens when particles are free to move
  3. The movement of oxygen and carbon dioxide in photosynthesis, happens by diffusion
    1. The higher concentration of Carbon Dioxide in the air diffuses into the leaf for photosynthesis.
      1. Oxygen produced through photosynthesis builds up until their is a higher concentration of oxygen in the leaf, then it diffuses out of the leaf into the air where there is a lower concentration of oxygen.
3. Osmosis
  1. For osmosis you need two solutions with different concentrations, and a partially permeable membrane.
    1. Partially Permeable membranes allow some substances to pass through but not others
  2. Osmosis is the movement of water from a less concentrated solution, to a more concentrated solution through a partially permeable membrane.
  3. Osmosis is important to plants. They gain water by osmosis through their roots. Water moves into plant cells by osmosis, making them turgid or stiff so they that able to hold the plant upright.
4. Minerals from the Soil
  1. The concentration of minerals in the soil is very low
    1. They dissolve in water and move around the soil in solution
      1. Root hair cells are adapted to absorb the water out of soil by osmosis – they have a large surface area, thin walls and are close to the xylem cells used for transporting water up the plant.
        Minerals such as nitrate ions cannot be absorbed by osmosis (which is the movement of water only) or diffusion (because the minerals are in very low concentration).
        The root hair cells have carrier molecules on their surface that pick up the minerals and move them into the cell against the concentration gradient. This requires energy, and is called active transport.
5. Factors affecting the rate of photosynthesis
  1. Light Intensity
  2. Carbon Dioxide levels
  3. Temperature
  4. Farmers can use their knowledge of these limiting factors to increase crop growth in greenhouses. They may use artificial light so that photosynthesis can continue beyond daylight hours, or in a higher-than-normal light intensity. The use of paraffin lamps inside a greenhouse increases the rate of photosynthesis because the burning paraffin produces carbon dioxide, and heat too.
6. Fieldwork Techniques
  1. Quadrats
    1. Used to survey the amount of plants present in a square metre
  2. Equipment one with lamp under water plant gas tubing attached to a syringe ext...
Obtaining Energy
1. Energy from Respiration
  1. Glucose is produced during photosynthesis. This energy is released from cells by a series of chemical reactions. This process is called respiration.
  2. Energy from respiration is used in reactions that produce different molecules. Examples of these molecules include starch and cellulose, which are polymers of glucose required by plant cells.
2. Aerobic Respiration
  1. Respiration is a chemical process in which energy is released from food substances such as glucose
  2. Aerobic respiration requires oxygen, and most of the chemical reactions happen in the mitochondria in the cytoplasm
  3. glucose + oxygen → carbon dioxide + water (+ energy)
  4. The energy from respiration can be used in plants to sugars nitrates and other nutrients are converted into Amino Acids. Amino acids can join together to make proteins. The energy from respiration also allows animals muscles to contract and maintain a constant body temperature in birds and mammals.
  5. C6H12O6 + 6O2 → 6CO2 + 6H2O
  6. Releases more energy per glucose than anaerobic Respiration
3. Anaerobic Respiration
  1. Anaerobic respiration is a type of respiration that does not use oxygen. It is used when there is not enough oxygen for aerobic respiration.
  2. glucose → lactic acid (+ energy released)
  3. This type of respiration can be used when an animal is being chased by a predator
  4. Anaerobic respiration also takes place in plants and some microbial cells in the presence of little or no oxygen. Examples of this include the roots of plants in waterlogged soils and bacteria in puncture wounds.
    1. Anaerobic respiration in plant cells and some microorganisms (such as yeast) produces ethanol and carbon dioxide, as opposed to lactic acid.
      1. glucose → ethanol + carbon dioxide (+ energy released)
      2. Has been known to make foods like yoghurt, bread and vinegar
4. Useful products from respiration
  1. During anaerobic respiration sugars are converted into ethanol. This is called fermentation.
    1. When fermentation happens on a large scale using yeast water sugar and some other nutrients, bioethanol can be made and used as fuel.
  2. Sustanibility
    1. Sustainability is the idea of using resources to meet the needs of the present without damaging the Earth or using up resources people might need in the future.
    2. Biofuel is seen as a renewable resource that would seem to be more sustainable. However, there is more to it. The large areas of land used to grow crops on for biofuel could be used to grow food. As well as this, trees can be cut down to make space to grow crops for biofuel.
      1. Also the burning will release Carbon dioxide into the air,but there will be less green plants to get rid of it
  3. Biogas
    1. Biogas is a fuel manufactured using animal manure (or sometimes human waste). Biodigesters are used to convert the manure into biogas. Bacteria inside the biodigester break down parts of the manure and produce methane gas. This gas can then be used as a fuel to run generators and heat buildings. This method of fuel production is more commonly used in developing countries.

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B4 The processes of life

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