Cells to Systems

  • Created by: aysha09
  • Created on: 16-03-15 18:18

Digestive enzymes

Intercellular enzymes work within cells, extracellular enzymes are attached to the gut wall and work on the outside of cells.

Protease (trypsin)

Produced in: small intestine, pancreas

Substrate: protein to amino acids

Used in: small intestine

Protease (pepsin)

Produced in: stomach, pancrease

Substrate: protein to amino acids

Used in: stomach

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The Digestive System

--> Mouth and Tongue- Salivary glands produce saliva, Amylase chemically breaks down food, chewing physically breaks down food

--> Oesophagus/Gullet- Preistalsis moves food into the stomach

--> Stomach- HCl makes right conditions for enzymes, protease breaks down food, acid-resistant mucus lining

--> Small Intestine- villi and microvilli absorb nutrients into the blood, amylase, lipase and protease work and are produced here

--> Large Intestine- water removed + absorbed into the bloodstream

--> Rectum & Anus- excretion

Bile is produced in the liver and stored in the gall bladder.

Bile is used to neutralize acid from the stomach to create alkaline conditions for the intestines.

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Tissues and Organs

Tissue: a group of cells with similar structure and function

Organ: a group of tissues making up a more complicated structure

Organ System: a group of organs working together to perform a particular function

Muscular tissue- contracts to produce movement

Glandular tissue- produce substances e.g enzymes

Epithelial tissue- protects  and covers parts of the body

In the stomach...

  • Muscle for contracting and bringing about movement to break down food
  • Epithelial for protecting the lining of the stomach
  • Glandular for producing enzymes 
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Effect of Temperature and pH on Enzymes

As the temperature increases, so does the rate of reaction. But very high temperatures denature enzymes. Different enzymes have different optimum temperatures.

Changes in pH also alter an enzyme’s shape.The optimum pH for an enzyme depends on where it normally works. A pH too far away from optimum will denature and enzyme.

When an enzyme denatures -

  • The shape of the active site changes shape
  • The enzyme can no longer fit the substrate
  • The enzyme cannot break down the substrate of catalyse the reaction
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Enzymes in Industry

Uses of Enzymes in Industry:

  • Biological washing powders contain proteases and lipases to break down stains made from protein (e.g. blood) and fats (e.g. food)
  • Protease is used to predigest baby food
  • Isomerase is used to convert glucose to fructose for slimming foods (fructose is a lot sweeter so less is needed for the same flavour)
  • Amylase is used to produce glucose for use in wine making 

Enzymes in industry are sourced from bacteria becuase they mulitply quickly and there are no ethical issues involved.

Advantages- reduce energy, can be reused, biodegradeable, easy to control

Disadvantages- can denature, expensive, can be irritant or allergenic

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Aerobic Respiration

Takes place continuosly in plants and animals.

Aerobic respiration takes place in the mitochondria of all cells and is controlled by enzymes.

Glucose + Oxygen --> Carbon Dioxide + Water [+energy]

 Breathing gets oxygen into the circulatory system and removes carbon dioxide from it. The gases diffuse trough the walls of the alveoli to oxygenate and deoxygenate blood.

Circulation carries oxygen and carbon dioxide from and back to the lungs.

Glucose is stored in the body cells as glycogen to be used in respiration when needed.

The energy produced in aerobic respiration is used for growth, repair, movement, thermoregulation, proteinsynthesis etc.

When aerobic respiration cannot meet the demands of the body for energy or oxygen (during exercise) anaerobic respiration takes place. 

Aerobic respiration is an exothermic reaction.

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Anaerobic Respiration

When exercise starts, aerobic respiration first increases with heart rate to try to increase the oxygen to muscles. Vasodilation also occurs.

When muscles are working for a long period of time they need more energy than aerobic respiration can provide. They then start to respire anaerobically.

Anaerobic respiration: The incomplete breakdown of glucose in the absence of oxygen.

Glucose  --> Lactic Acid [+energy]

Anaerobic respiration happens in the cytoplasm of cells.

After exercise has stopped the oxygen debt must be repayed. 

Oxygen debt: volume of oxygen needed to remove the lactic acid from muscles

Lactic acid + Oxygen  --> Carbon Dioxide + Water

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Digestive Enzymes 2


Produced in: salivary glands, pancreas, small intestine

Substrate: Starch to glucose

Used in: mouth, small intestine


Produced in: pancreas, small intestine

Substrate: Lipids to fatty acids and glycerol

Used in: small intestine, stomach

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