Adaptation for nutrition

• Nutrition 


  • The process by which organisms obtain energy to maintain life functions, and matter to maintain structure.
• Autotrophic nutrition 


  • Autotrophic organisms synthesise their own organic molecules from simpler molecules using light or chemical energy:
  • Photoautotrophic: Use energy from sunlight to carry out photosynthesis and synthesise complex organic molecules through simple inorganic molecules such as carbon dioxide and water.
  • Chemoautotrophic: use energy from chemical reactions to synthesise organic molecules. Eg bacteria respiring in deep sea hydrothermal vents.
• Why must food be digested?

  • Food molecules are too large and insoluble to cross membranes and be absorbed into the bloodstream.
  • Polymers must be broken down into monomers so they can be re-built (assimilated) into molecules needed by the body cells.
• Digestion 


  • The breakdown of large insoluble molecules into small soluble molecules that can be absorbed into the blood, there are two types :
  • Mechanical digestion: Cutting and crushing with teeth and contractions by gut, increases surface area for enzyme action.
  • Chemical digestion: breakdown via digestive enzymes. eg bile and stomach acid.
• Peristalsis 


  • This is a wave of muscular contraction and relaxation in the gut wall which propel the content along the whole length of the gut.
  • Circular muscles behind The bonus of food contract and then relax after the wave of contraction has passed.
  • Dietary fibres aid peristalsis in the intestines.
• What does saliva contain?

  • Amylase
  • Bicarbonate ions which create an optimum pH for amylase (slightly alkaline).
  • Mucus to lubricate food.
• What does gastric juice contain?

  • Mucus, secreted by goblet cells which like the mucosa, it forms a protective lining which protects the stomach from digestive enzymes and hydrochloric acid and helps to lubricate the food.
  • Hydrochloric acid, secreted by oxyntic cells, lowers the pH of the stomach to pH 2 to create an optimum environment for enzymes and kills bacteria.
  • Pepsin , secreted as inactive pepsinogen, This is a peptidase that works optimally in the acidic environment of the stomach. It Is activated by hydrochloric acid.
• Why are enzymes in the stomach secreted in an inactive form?

  • So they don’t digest the stomach cells or tissues.
• What does pancreatic juice contain?


  • Amylase, breaks down any remaining starch into maltose.
  • Trypsin, secreted in an inactive form, and then it Is activated by enterokinase (which is secreted in the duodenum) to form trypsinogen, it is an endopeptidase.
  • Lipase, breaks down lipids.
  • Pepsidases, breaks down proteins to shorter polypeptides
• Bile


  • Bile contains bile salts which are both hydrophobic and hydrophilic, it is produced in the liver and stored in the gall bladder, it is transported into the duodenum through the bile duct.
  • It emulsifies lipids into smaller soluble molecules and increases the surface area for lipase enzymes to break down the lipid into fatty acids and glycerol.
  • It neutralises the acidic content from the stomach as it is alkaline.
• Adaptations of the ileum for absorption.

  • It is very long ( around 6 metres)
  • It has a folded lining
  • On the surface of the folds are villi.
  • The epithelial cells on the villi have microscopic projections called micro-villi.
  • All of these features increase its surface area.
• Specialised cells in the mucosa of the ileum:

  • Columnar epithelial cells have, microvilli and large numbers of mithocondria.
  • Goblet cells secrete mucus, which lubricates and protects the lining of the intestine.
• Absorption in the ileum

  • Fatty acids and glycerol, diffusion into the lymphatic capillary.
  • Glucose and galactose, co-transport with Na+ into the blood capillaries.
  • Water, osmosis into the blood capillaries.
  • Amino acids, active transport into blood capillaries.
• Uses of products of digestion

  • Glucose, required for respiration , excess is stored as glycogen.
  • Amino acid, Used for protein synthesis, excess is deaminated in the liver to form urea.
  • Lipids, energy storage, protection of vital organs, thermal insulation.
• Substances absorbed in the large intestine.

  • Water
  • Mineral ions
  • Vitamins produced by symbiotic bacteria eg vitamin K and folic acid.
• Pork Tapeworm 


  Tapeworms are highly evolved and specialised, they have no predators and no competition.

  • Ribbon like, 10 metres long.
  • Has a scolex (head) made of muscle that has hooks and suckers.
  • Primary host is humans and secondary host is pigs.
  • The larval form is found in pigs, pigs become infected by eating from drainage channels that contain human faeces with eggs.
  • humans become infected by eating undercooked contaminated pork.
  • It’s body is a linear series of sections.
• Pork tapeworm, adaptations 


  • It has suckers and hooks that attach to the gut wall during peristalsis.
  • It has a thick cuticle and produces inhibitory substances (anti enzymes) to prevent digestion by enzymes.
  • It has both reproductive organs and can self fertilise it produces many eggs with resistant shells.
  • It is long and thin and so it has a large surface area to volume ratio so it can just directly absorb digested food in the small intestine.
• Human dentition


  • Humans have incisors (the front of teeth) for cutting and biting food
  • Canines for tearing and ripping food.
  • Molars and premolars for grinding and chewing food.
• Herbivore dentition.


  • A herbivore diet is cellulose based. Cellulose is difficult to digest. Herbivores teeth are specialised for grinding to increase surface area for bacterial cellulase enzyme action.
  • It has horny pad, tongue wrap around the grass and pulls it tightly across the horny pad.
  • Diastema, it is the gap between the front teeth and cheek.
  • Incisiors for slicing through grass.
  • Molars and pre molars, W and M interlock and grind food to increase surface area
  • Lower jaw moves from side to side to grind food in circular motion.
• Carnivore detention.


  • Small incisors, to grip and tear flesh from bone.
  • Large curved canines, to seize and hold prey.
  • Pre molars and molars for cutting and crushing food.
  • Carnasials, slide each other like blades and crush bones.
  • Vertical haw movement, jaw can open very wide and cannot be dislocated while prey is struggling In its grip.