Biology - Nutrition

• Nutrition


  The process by which living organisms obtain or make food
• Types of nutrition


  • Autotrophic nutrition
  • Heterotrophic nutrition
• Autotrophic nutrition


  • Occurs in green plants and some bacteria via photosynthesis
  • Organisms (autotrophs) use simple inorganic compounds to make complex organic food substances
  • Requires energy from sunlight
• Heterotrophic nutrition


  • Occurs in animals, fungi and most bacteria
  • Organisms (heterotrophs) obtain ready-made organic food from their environment
• Types of heterotrophic nutrition

  • Holozoic nutrition
  • Saprophytic nutrition
  • Parasitic nutrition
• Holozoic nutrition


  Organisms obtain food by consuming other organisms, then digest the food within their body
• Saprophytic nutrition


  Organisms (saprophytes) obtain food from the dead remains of other organisms, digest the food outside their bodies and then absorb the simpler substances produced
• Parasitic nutrition


  Organisms (parasites) obtain food from the body of another living organism (the host), usually harming the host
• Conditions needed for photosynthesis

  • Carbon dioxide
  • Water
  • Sunlight energy
  • Chlorophyll
  • Enzymes
  • Suitable temperature
• Certain mineral ions are also indirectly required for plants to manufacture chlorophyll, e.g. magnesium (Mg2+), iron (Fe3+) and nitrate (NO3−) ions
• Leaves


  • Flat part called the lamina made up of several layers of cells
• Environmental factors affecting rate of photosynthesis

  • Light
  • Carbon dioxide
  • Temperature
  • Water
• The rate of photosynthesis is limited by whichever of these factors is in the shortest supply
• Processes in heterotrophic nutrition in humans

  • Ingestion
  • Digestion
  • Absorption
  • Assimilation
  • Egestion or defecation
• Balanced diet


  Diet containing carbohydrates, proteins, lipids, vitamins, minerals, water and roughage in the correct proportions to supply the body's needs
• The amount of energy required daily from the diet depends on a person's age, occupation and gender
• Malnutrition


  Condition caused by eating a diet in which certain nutrients are either lacking, are in excess or are in the wrong proportions
• Macronutrients


  • Carbohydrates
  • Proteins
  • Lipids
• Micronutrients


  • Vitamins
  • Minerals
• Fat soluble vitamins


  Vitamins A and D
• Water soluble vitamins


  Vitamins B and C
• Water


  Essential inorganic compound in a balanced diet, making up about 65% of the human body
• Roughage (dietary fibre)


  • Food that cannot be digested, consisting mainly of plant cell walls, xylem vessels, husks and bran
  • Adds bulk to food, stimulating peristalsis and preventing constipation and colon cancer
• Saprophytes


  Organisms that obtain nutrients from dead or decaying organic matter by secreting enzymes and absorbing simpler substances through their cell walls.
• Mesophytes


  Plants adapted to grow in moderate moisture conditions with moderate water requirements. Examples include deciduous trees, grasses, and many common garden plants.
• Saprophyte nutrient acquisition


  Saprophytes secrete enzymes to break down complex organic matter from dead or decaying organisms into simpler substances, which are then absorbed by the saprophyte through its cell walls. They do not have the ability to photosynthesize.