Characteristics of living organisms

• Mechanical digestion


  Chewing, churning or grinding to break food down
• Nutrition in humans


  Balanced diet includes appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre
• Components of a balanced diet

  • Carbohydrate (sugars and starch)
  • Protein (long chains of amino acids)
  • Lipid (fatty acid and glycerol)
  • Vitamins: A, C, D
  • Mineral ions: Calcium, Iron
  • Water
  • Dietary Fibre
• Sources of diet components

  • Carbohydrate: Bread, pasta, rice
  • Protein: Meat, fish, cheese, nuts
  • Lipid: Butter, eggs, cheese
  • Vitamins A: Fish liver oils, butter, carrots
  • Vitamin C: Fresh fruit and veg
  • Vitamin D: Fish liver oils, butter, made in skin in sunlight
  • Calcium: Dairy products, fish, veg
  • Iron: Red meat, liver, eggs, green leafy veg
• Functions of diet components

  • Carbohydrate: Provide energy for cells
  • Protein: Growth and repair, making enzymes
  • Lipid: Used as energy store/insulation/protection
  • Vitamins A: Synthesis of retinal chemicals
  • Vitamin C: Sticks cells lining surface of body together
  • Vitamin D: Helps bones absorb calcium and phosphorus
  • Calcium: Make bones and teeth
  • Iron: Makes haemoglobin
• Water


  Important solvent and for hydrolysis of large molecules
• Dietary Fibre


  Needed for bulk in peristalsis
• Characteristics of living organisms

  • Composed of units called cells
  • Simplest organisms are unicellular (single celled)
  • More complex organisms are multicellular, with different types of cells working together
  • Require nutrition
  • Excrete
  • Move
  • Grow and develop
  • Respire
  • Respond to stimuli
  • Reproduce
  • Control
• Life processes common to most living things

  • Require nutrition
  • Excrete
  • Move
  • Grow and develop
  • Respire
  • Respond to stimuli
  • Reproduce
  • Control
• Plants


  Make own food; animals need to eat other organisms
• Excretion


  Removal of toxic waste
• Growth


  Slow growth in plants; action of muscles in animals
• Development


  Increase in size and mass, using material from food
• Respiration


  Release of energy from food through chemical reaction
• Response to stimuli


  Sensitive to changes in environment
• Reproduction


  Produce offspring
• Control


  Able to change internal conditions
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• Enzymes


  • Biological catalysts (speed up metabolic reactions)
  • Not used up in reaction
  • Specific to each reaction
  • Made of protein
• Enzyme action


  1. Substrate (key) enters enzyme's active site (lock)

  2. Forms "enzyme-substrate complex

  3. Reaction takes place

  4. Products form and leave active site
• As temperature increases


  Kinetic energy increases so enzyme and substrate collide more often
• Optimum temperature


  Temperature at which reaction occurs most rapidly
• Beyond optimum temperature


  Rate decreases rapidly as protein is broken down by heat. Enzyme is denatured
• Optimum pH


  pH at which that enzyme works best
• Either side of optimum pH

  pH affects shape of enzyme's active site so substrate will not fit so well, so rate of activity decreases
• Cell structure


  • Nucleus: Controls activities of cell; contains chromosomes which carry genetic information
  • Cytoplasm: Site of chemical reactions
  • Cell membrane: Selectively permeable, controls entry and exit of substances
  • Cell wall: In plants made from cellulose, fully permeable, gives support to cells
  • Chloroplast: Site of photosynthesis
  • Vacuole: In plant cells, contains cell sap
• Mitochondria


  • Site of aerobic respiration
• Differences between animal and plant cells

  • Animal: Only small, temporary vacuole; No chloroplasts; Usually irregular
  • Plant: Cellulose cell wall; Large vacuole; In green parts of plant; Usually regular
• Levels of organisation


  • Organelles
  • Cells
  • Tissues
  • Organs
  • Organ systems
• Organelles


  Structures found within cytoplasm
• Cells


  Basic building blocks of life
• Tissues


  Cells with same function grouped together
• Organs


  Collection of several tissues carrying out a particular function
• Organ systems


  Several different organs working together
• Examples of organ systems

  • Digestive
  • Respiratory
  • Circulatory
  • Excretory
  • Nervous
  • Endocrine
  • Reproductive
• Digestive system


  Gut, pancreas, gall bladder; Digest food, absorb digested products into blood
• Respiratory system


  Lungs, trachea; Exchange oxygen and carbon dioxide
• Circulatory system


  Heart, blood vessels, blood; Transport of substances around body
• Excretory system


  Kidneys, bladder; Filter toxic waste materials from blood