Ch5 – Proteins + Enzymes


Ch5 – Proteins + Enzymes – Please click on this link  for Mrs Smith’s

CHAPTER  4 powerpoint presentation.

Proteins and Enzymes HW1,     Proteins and Enzymes HW2        Proteins and Enzymes HW3      – This is your homework for chapter 2 or, you can use it for revision any time.

Proteins + Enzymes Wordbank – Use this worksheet to familiarise yourself with the vocabulary for the chapter.

Traffic lights – What you should know.

I encourage you to think more carefully about your own learning. Self-assessment is an important tool to achieve this. You can use a thumbs up, medium, down/ traffic lights system. At the end of each lesson consider your learning intentions and grade your understanding.

  • Picture1G (green light – understand this very well), O (amber light) – need a bit of support but understand the basics or…R (red light – help I don’t understand).





The effect of manganese dioxide on the breakdown of hydrogen peroxide.


This is a handy animation which shows how enzymes work.


Enzymes are proteins. They act as catalysts, allowing chemical reactions to take place by lowering the amount of energy needed. They therefore speed up reactions or allow them to happen at low temperatures.

Some enzymes break down substances (e.g. digestive enzymes). The following link shows a degradation reaction.


Some enzymes build up simple raw materials into more complex substances. The following link shows a synthesis reaction.



Enzymes are very specific. The lock and key hypothesis explains this using the idea that each enzyme has a specifically shaped active site. The following link shows the specificity of enzymes.


All enzymes have specific conditions at which they will work the best. These are known as the‘optimum conditions’. Factors which can affect the performance of an enzyme include temperature and pH.  As enzymes are biological, many of them work best at 37°C (body temperature). If the temperature rises too high, this can cause the enzyme to become damaged changing the shape of the active site meaning that the substrate will  no longer fit. The enzyme is described as having become denatured. The following video explains about factors which affect enzyme activity


The lock and key hypothesis explains why high temperatures denature enzymes. The following link shows a denatured enzyme with an active site that no longer fits it’s substrate.




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