acedmia files

• Life processes


  Maintenance functions of living organisms that must go on even when they are not doing anything particular
• Living organisms must keep repairing and maintaining their structures made up of molecules
• Energy is needed for the maintenance processes in living organisms
• Nutrition


  Process to transfer a source of energy (food) from outside the body of the organism to the inside
• Most food sources are carbon-based
• Respiration


  Process of acquiring oxygen from outside the body, and using it to break down food sources for cellular needs
• In multi-cellular organisms, a transportation system is needed to carry food and oxygen from one place to another in the body
• Excretion


  Process of removing waste by-products from the body and discarding them outside
• Diffusion is insufficient to meet the oxygen requirements of multi-cellular organisms like humans
• Criteria used to decide whether something is alive include movement, growth, and molecular movement
• Autotrophs


  Organisms that use simple food material obtained from inorganic sources like carbon dioxide and water
• Heterotrophs


  Organisms that utilise complex substances and have to break them down into simpler ones before use
• Photosynthesis


  1. Absorption of light energy by chlorophyll

  2. Conversion of light energy to chemical energy and splitting of water molecules

  3. Reduction of carbon dioxide to carbohydrates
• Chlorophyll is essential for photosynthesis
• Stomata


  Tiny pores present on the surface of leaves that allow for gaseous exchange
• Guard cells control the opening and closing of stomatal pores
• Plants take up water, nitrogen, phosphorus, iron and magnesium from the soil
• Parasitic nutrition


  Organisms derive nutrition from plants or animals without killing them
• In single-celled organisms, the entire surface can take in food, but in complex organisms different parts become specialised
• Organisms that break-down food material outside the body and then absorb it

  • Fungi like bread moulds, yeast and mushrooms
• Organisms that derive nutrition from plants or animals without killing them (parasitic nutritive strategy)

  • Cuscuta (amar-bel), ticks, lice, leeches and tape-worms
• How organisms obtain their nutrition

  1. Food is taken in by the entire surface (single-celled organisms)

  2. Different parts become specialised to perform different functions (complex organisms)
• Nutrition in Amoeba


  1. Food taken in using temporary finger-like extensions of the cell surface

  2. Food particle enclosed in a food-vacuole

  3. Complex substances broken down into simpler ones which diffuse into the cytoplasm

  4. Remaining undigested material moved to the surface and thrown out
• Nutrition in Paramoecium


  1. Food taken in at a specific spot

  2. Food moved to this spot by the movement of cilia covering the entire surface
• Nutrition in human beings

  1. Food crushed with teeth

  2. Food wetted with saliva to make passage smooth

  3. Saliva contains enzyme salivary amylase that breaks down starch

  4. Food mixed thoroughly with saliva and moved around mouth by tongue

  5. Peristaltic movements push food forward along digestive tube

  6. Food enters stomach through oesophagus

  7. Stomach mixes food with digestive juices (hydrochloric acid, pepsin, mucus)

  8. Food exits stomach in small amounts into small intestine

  9. Small intestine site of complete digestion of carbohydrates, proteins and fats

  10. Bile from liver and pancreatic enzymes aid digestion

  11. Digested food absorbed by intestinal villi

  12. Unabsorbed food enters large intestine where more water is absorbed

  13. Waste material removed from body via anus
• Dental caries (tooth decay) caused by bacteria acting on sugars to produce acids that soften enamel and dentine
• Brushing teeth after eating removes plaque before bacteria produce acids
• If untreated, microorganisms may invade the pulp, causing inflammation and infection
• When air is blown through lime water

  Lime water turns milky
• When air is passed through lime water using a syringe/pichkari


  Lime water turns milky faster
• This indicates a higher amount of carbon dioxide in the exhaled air
• Fermentation


  1. Fruit juice/sugar solution mixed with yeast

  2. Carbon dioxide produced, indicated by lime water turning milky
• Anaerobic respiration breaks down pyruvate to produce ethanol and carbon dioxide
• Aerobic respiration breaks down pyruvate to produce carbon dioxide and water
• Aerobic respiration releases a lot more energy than anaerobic respiration
• Lactic acid builds up in muscles during sudden activity, causing cramps
• ATP


  Energy currency for most cellular processes
• Energy released during respiration is used to synthesise ATP
• ATP can be used in cells for contraction of muscles, protein synthesis, conduction of nervous impulses and many other activities
• Gas exchange in plants

  1. Carbon dioxide and oxygen exchanged by diffusion through stomata and intercellular spaces

  2. At night, CO2 elimination is the major exchange activity

  3. During the day, oxygen release is the major event as CO2 generated is used for photosynthesis