2. Structure and Function in Living Things

• Organelles make up cells
• Cells make up tissues
• Tissues make up organs
• Organs make up organ systems
• Nucleus:

  • contains the genetic information of cell in the form of chromosomes (DNA)
  • parts of chromosomes (genes) determine substances made
  • therefore the nucleus controls cell activities
• Cell membrane:

  • the boundary between the cytoplasm and the outside of the cell
  • partially permeable
  • can control what goes in and out
• Cytoplasm:

  • watery jelly-like liquid that contains organelles and enzymes
  • many chemical reactions happens here (metabolic reactions)
• Mitochondria:

  • carries out reactions of aerobic respiration
  • releases energy
• Ribosomes:

  • very small particles in the cytoplasm
  • makes proteins (protein synthesis) --> determined by genes
• Chloroplasts, cell wall and vacuoles only appear in plant cells
• Chloroplasts:

  • contains chlorophyll (green pigment)
  • allows photosnythesis
• (Plant) Cell wall:

  • made of cellulose
  • protects the cell
  • keeps its shape
  • freely permeable
• Vacuole:

  • filled with cell sap
  • store of dissolved sugars, mineral ions and water
  • keeps cell shape
• Carbohydrates are made of carbon, hydrogen and oxygen
• Lipids are made of carbon, hydrogen and oxygen
• Proteins are made of carbon, hydrogen, oxygen and nitrogen
• Carbohydrates act as our store of energy, released during aerobic respiration
• Lipids help keep the shape of our cell membranes and act as our store of energy
• Proteins keep our cell shape, acts as a biological catalyst, helps with antibodies, receptors and hormones
• Carbohydrates break down into simple sugars (glucose)

  For animals, glucose is further broken into glycogen

  For plants, glucose is further broken into starch
• Lipids break down into glycerol and fatty acids
• Proteins break down into amino acids
• 1 protein is made of 12 amino acids
• Glucose is formed by glycosidic bonds
• Lipids are formed by ester bonds
• Proteins are formed by peptide bonds
• Enzymes are biological catalysts
• Enzymes are proteins coded for by genes
• How enzymes break down polymers:

  1. Substrate collides with the active site
  2. The substrate is the correct shape to fit into the active site
  3. A reaction takes place
  4. The product is released and the enzyme can be used again
• Factors that affect enzymes:

  • temperature
  • pH
• Enzymes and temperature:

  • Higher temperatures increase the kinetic energy
  • More collisions for substrate and active site
  • Makes more enzyme-substrate complex

  However...

  • If temperatures are too high, enzymes become denatured
  • Substrate can no longer bind to the active site
• The optimum temperature for enzymes: 37 degrees C
• Enzymes and pH:

  • Acid/alkali interferes with bonds
  • If the pH is too acidic or alkaline, the enzyme becomes denatured
  • The substrate can no longer bind to the active site
• The optimum pH for most enzymes: 7

  The optimum pH for pepsin: 2
• Starch food test:

  • Put a small sample into the test tube
  • Add a few drops of iodine
  • If the food goes blue/black, it contains starch
• Glucose food test:

  • Put the food sample into a boiling tube
  • Make sure it is in liquid form
  • Add a squirt of Benedict's solution
  • Heat the boiling tube in a water bath at 80 degree celsius for 5 minutes

  The sample goes from green to orange to brick red depending on how much glucose there is
• Protein food test:

  • Put the food sample into a test tube
  • Add a squirt of Biuret solution
  • If the food goes purple/lilac, it contains proteins
• Lipids food test:

  • Put the food sample into a test tube
  • Add a small volume of ethanol
  • Shake the test tube and the fat is dissolved into the ethanol
  • An equal volume of water is added
  • If the solution turns cloudy, it contains lipids
• Cells carry out chemical reactions by having substances leave and enter
• Cells carry out chemical reactions in 3 ways:

  1. Diffusion
  2. Osmosis
  3. Active transport