B2.3 Enzymes and B2.4 Respiration

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  • Created by: lucylulou
  • Created on: 14-01-16 18:16

Enzymes

Enzymes are biological catalysts (catalysts produced by living things)

Living things always have many chemical reactions going on

They can be carefully controlled- to get the right amount of substance

Raise the temperature - speed up reaction - but also speed up the unwanted ones

Temperature too high - denature the enzymes

By using enzymes, there's less need for high temperatures, and they can speed up the useful chemical reactions alone

ENZYMES SPEED UP REACTIONS without being USED UP or CHANGED

Enzymes are proteins. Proteins are made up of chains of amino acids.

Proteins also act as parts of tissues (muscles), hormones and antibodies

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Special Shapes

Enzymes have SPECIAL SHAPES to CATALYSE REACTIONS

Chemical reactions = splitting or joining substances

Every enzyme has a unique shape which fits a certain subatance in a reaction

If the substance doesn't match the enzyme's shape, the reaction won't be catalysed

                        (http://waynesword.palomar.edu/images/enzyme5.gif)

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Temperature and pH

ENZYMES need the RIGHT TEMPERATURE and pH                                                               Change the temerature. - changes the rate of an enzyme-catalysed reaction

The higher the temperature the faster the rate -too high, enzymes are denatured                     Too hot - bonds holding the enzyme together break- loses its special shape - denatured

Enzymes in humans work best at around 37ºC

pH has the same effect as temperature - too high or low - denatures enzymes

All enzymes have an optimum pH that they work best at - often neutral 7, others like pepsin works best at 2 because it breaks down proteins in the stomach (acid conditions)

                                                         (http://www.s-cool.co.uk/assets/learn_its/gcse/biology/enzymes/enzymes/optimum_conditions.gif)

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Digestion

Digestive enzymes - produced by cells, work outside of cells                                          they break BIG molecules into SMALLER ones ▾

AMYLASE - starch to glucose                   made in the pancreas, salivary glands, small intestine

PROTEASE - proteins to amino acids       made in the pancreas, stomach, small intestine

LIPASE - lipids to fatty acids & glycerol    made in the pancreas, small intestine

Bile - neutralises stomach acid and emusilfies fats                                                                       produced in liver, stored in gall bladder, released into small intestine

Hydrochloric acid in stomach - too acid (pH) for enzymes in small intestine                                       Bile is alkaline - neutralises the acid - better conditions for enzymes (alkaline)                               Breaks down fat into tiny droplets - bigger surface area for LIPASE - digestion is faster

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Digestive System

                                    (http://a.files.bbci.co.uk/bam/live/content/zttrwmn/large)

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About the Digestive System

Salivary glands - produces amylase

Oesophagus - food pipe

Liver - produces bile - neutralises stomach acid & emulsifies fat

Stomach - pummels food with muscular walls - produces protease (pepsin)

Gall bladder - stores bile before releasing into small intestine

Pancreas - produces amylase, protease, lipase, releases them into small intestine

Small intestine - produces amylase, protease, lipase - absorbs digested food into blood

Large intestine - excess water absorbed from food

Rectum - stores faeces, before released from ****

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Respiration

RESPIRATION is the process of  RELEASING ENERGY from GLUCOSE in all CELLS

Involves many reactions - catalysed by enzymes                                                                             Respiration releases energy needed for everything                                                                                        Happens in all living things - plants, animals - it's how they get energy for food

AEROBIC RESPIRATION - needs lots of oxygen                                                                                    more efficient - takes place in mitochondria in cells                                                            Oxygen + glucose  ☛  carbon dioxide + water

ANAEROBIC RESPIRATION - lack of oxygen                                                                                  not efficient - produces lactic acid - toxic to cells                                                                        glucose  ☛  lactic acid + energy

ENERGY FOR...                                                                                                                                                                   building up small molecules into bigger ones                                                                                                                                             to keep body temperatures constant                                                                                                                                              building sugars, nitrates & other nutrients into amino acids, then proteins in plants

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