Organisation and the digestive system

• tissue definition

  group of cells, similar structure and function working together
• organ definition


  collection of tissues working together to perform a specific function
• organ system


  groups of organs working together to perform a specific function
• how is the stomach adapted for its role in the digestion of food

  Layer of muscular tissue contracts to churn up food, mixing it with digestive juices to help physical and chemical digestion.

  Glandular tissue produces enzymes to break down food.

  Folded lining provides increased surface area.

  Tough epithelial tissue covers and protects inside and outside of organ
• Explain how organs in an organ system rely on each other to function properly

  -Each part of digestive system relies on preceding parts.

  -Stomach relies on mouth, teeth, and salivary glands to deliver chunks of chewed food.

  -Small intestine depends on stomach to continue digestive process and on enzymes made by pancreas to help with the digestive process. -Large intestine can only deal with remains of food already digested in the small intestine (soluble molecules absorbed into blood, leaving waste material and water), absorbing water and removing faeces from body.
• Proteins carry out many different functions in your body. They act as:

  -structural components of tissues such as muscles and tendons

  -hormones, e.g. insulin

  -enzymes, which act as catalysts

  -antibodies
• what is a protein


  molecule made up of long chains of amino acids
• similarities and differences between carbohydrates, lipids and proteins

  similarities:

  • vital components of a balanced diet

  • contain carbon, hydrogen, and oxygen

  • large molecules made up of smaller molecules joined together differences:

  • carbohydrates made up of sugar units

  • lipids made up of fatty acids and glycerol

  • proteins made up of long chains of amino acids

  • lipids insoluble in water

  • proteins contain nitrogen
• why are carbohydrates good?


  provides us with the fuel that makes all of the other chemical reactions possible
• why are lipids good

  most efficient energy store in body and important source of energy in diet
• proteins are good because

  they build up cells and tissues of your body
• Why are lipids either fats or oils

  Lipids are made up of three molecules of fatty acids joined to a molecule of glycerol. Different combination of fatty acids determines whether lipid is solid (fat) or liquid (oil)
• What do enzymes control?

  metabolism
• Specific metabolic reactions that different enzymes catalyse:

  -Building large molecules from lots of smaller ones e.g. starch from glucose

  -Changing one molecule into another e.g. glucose to fructose

  -Breaking down large molecules into smaller ones e.g. breakdown of lipids
• what is a catalyst


  substance that speeds up a chemical reaction but is not used up or involved in the reaction and can be used many times over
• what is an enzyme 


  large protein molecule that acts as a biological catalyst
• what is an active site


  area in structure of enzyme with unique shape that binds to specific substrate
• how does an enzyme work

  Substrate of reaction to be catalysed fits into active site of enzyme like a lock and key.

  Once in place, enzyme and substrate bind together.

  Reaction takes place rapidly and products are released from active site.

  Enzyme then ready to catalyse another reaction.
• How are enzymes important in the metabolism of a cell

  Chemical reactions needed for life could not take place fast enough without enzymes to speed them up.

  Each reaction controlled by specific enzyme so that many metabolic reactions can take place in same small space without interfering with one another.

  Enzymes enable cells to perform basic reactions (e.g., respiration) and specific reactions to carry out particular functions simultaneously
• what temperature do most human enzymes work best at

  37 degrees C
• what is optimum temperature

  when reaction works as fast as possible
• Describe effect of temperature on an enzyme-controlled reaction

  Rate of enzyme‑controlled reaction initially increases as temperature increases, up to optimum temperature.

  Once temperature exceeds 40 °C, protein structure of enzyme starts to break down.

  Rate of reaction slows and ultimately stops when enzyme is denatured (stops working)
• Why would you bring the temperature of an ill person down?

  -if body temperature increases too much (over 40), proteins making cell structure start to be damaged and shape of protein molecules making up enzymes is affected

  -changes shape of active site

  -enzyme is less effective and denatured, preventing chemical reactions necessary for life

  -reducing temperature in ill people balances act between damaging harmful microorganisms and damaging ill person's own cells
• Where are digestive enzymes produced

  salivary glands and pancreas
• where is amylase produced

  pancreas, small intestine and salivary gland
• where is protease produced

  pancreas, small intestine and stomach
• where is lipase produced

  pancreas and small intestine
• why is nothing broken down by pancreas

  no digestion takes place in pancreas
• what reaction does amylase catalyse?

  carbohydrates into sugar
• which pH does pepsin work best

  2
• what happens to activity of the enzyme as pH increased

  Activity levels increase up to optimum pH then fall fast.]
• Explain what happens as optimum pH is surpassed

  Increase in pH affects shape of active site of enzyme so it no longer bonds to the substrate. Enzyme ultimately denatured and no longer catalyses reaction.
• Importance of digestion of food in terms of molecules involved and role of enzymes in gut

  Large insoluble molecules in food cannot be absorbed into the blood. They have to be broken down to form small insoluble molecules that can be absorbed.

  Role of enzymes is to catalyse breakdown of food so food can be digested at the right speed and in the right region of the gut to be absorbed and used by the body
• how does body create right pH in the stomach for pepsin

  Hydrochloric acid is made in glands in the stomach lining to produce low pH (acidic conditions).
• how does body create right pH in the small intestine for protease enzymes to work

  Liver produces bile, stored in gall bladder and released when food enters small intestine. Bile is alkaline, neutralising stomach acid to create a slightly alkaline environment in small intestine
• Why is it important for bile to emulsify fats

  Fats do not mix with other liquids in digestive system, staying as large globules that are hard for lipase enzymes to act on. Larger surface area produced by bile action allows enzymes to reach more fat molecules and break them down more quickly
• two main functions of digestive system


  absorption of food molecules

  digestion of food molecules