Enzymes and digestion

additional biology

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  • Created by: Bennett
  • Created on: 21-04-10 18:36

Enzymes and Digestion

  • Enzymes are biological catalysts which speed up the rates of reactions in the body. They are proteins which are made up of long layers/chains of amino acids.
  • They are denatured above 45˚C and certain pHs (specific to each type) can also denature enzymes.
  • Enzymes are designed to act on certain materials called substrates. Each enzyme is specialized and only targets a specific set of substrates.
  • The reactions allow processes such as cellular respiration, cell growth, digestion and tissue repair to take place.
  • Each type of enzyme works best at different pHs and temperatures, so it is important that they have the right environments in order to work efficiently and prevent being denatured.
  • Enzymes are proteins which are folded into complex shapes that allow smaller molecules to fit into them. The place where these SUBSTRATE molecules fit is called the active site.
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They are BIOLOGICAL CATALYSTS. Catalysts are substances that increase the rate of chemical reactions without being used up.

  • Smaller molecule substrates can join together to form a larger molecule substrate at the active site or a larger molecule can be broken down into smaller substrates.

Only certain substrates can be catalyzed by certain enzymes. If the shape of the enzyme changes (due to too high temperatures or the wrong pHs conditions) then its active site may no longer work. We say the enzyme has been denatured.

  • Enzymes are very important in respiration. Aerobic respiration releases energy from glucose.>

Oxygen + Glucose = Carbon dioxide +water + energy

Respiration is a chemical process in which energy is released from food substances, such as glucose (a sugar)

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Enzymes continued.

  • Enzymes in cells catalyze photosynthesis ,protein-synthesis (joining amino acids together which form proteins), and aerobic respiration.

Enzymes in the intestine have an optimum pH of about 7.5, which are alkaline conditions

Enzymes in the stomach have an optimum pH of 2, which is an acidic environment

  • The energy releaed by respiration is used to make large molecules from smaller ones. e.g. proteins from amino acids.

In plants > sugars, nitrates and other nutrents are converted into amino acids which can then build up into proteins

In animals > the energy is used to allow muscles to contract

  • In Birds and mammals > the energy is used to maintain a constant core body temperature.

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Amylase = This is an enzyme which breaks starch down into sugars.

  • Catalyzes the reaction between starch and sugars
  • For example it helps starch be broken down into glucose.

It is produced in the-


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Protease = is an enzyme which breaks proteins down into amino acids

  • Catalyzes the reaction between proteins and amino acid.

It is produced in the-


STOMACH>(where it is called pepsin)

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Lipase and BILE

Lipase = is an enzyme which breaks down lipids(oils and fats) into glycerol and fatty acids.

  • Catalyzes the reaction between lipids and fatty acids and glycerol.




THIS IS RELEASED INTO THE SMALL INTESTINE TO NEUTRALIZE THE STOMACH ACID. It also emulsifies fats(Breaks them down into tiny droplets) this gives a bigger surface area for the lipase to work on which makes the digestion faster.

Hydrochloric acid in the stomach makes it too acidic for enzymes in the small intestine to work well. Bile neutralizes the acid because it is an alkaline and makes the conditions alkaline which is where the enzymes work best.


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Uses of enzymes

Biological detergants

  • Biological washing powders
  • Mainly protein-digesting enzymes(proteases) and fat-digesting enzymes(lipases)
  • Enzymes attack animal and plant matter which means they are useful for removing stains like food and blood.

Changing foods

  • Baby foods> these are pre-digested, using proteases, to make it easier for babies to digest.
  • Carbohydrate-digesting enzymes(carbohydrases) are used tpo turn starch syrup into sugar syrup
  • Glucose syrup can be turned into fructose syrup using an isomerase enzyme. Fructose is sweeter so you can use less of it, which is good for slimming foods and drinks.
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  • They speed up reactions without a need for high temperatures and pressures
  • are reusable which saves money and resourses. But they can be washed away buy substanses in industry so they cn be trapped in an ALGINATE BEAD or in a lattice of SILICA GEL
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Victoria Haines

Omg thank you sooo much - you are my life saver ;D ! ***x


no problem :)



Brilliant notes, helped so much,

much better than the teacher!!!

Than**....** =)


Thats ok, glad they helped! :)

Bex Steele

soo helpful :) thankyou


That's awesome, thanks! :)

amy froshaug

really helpful! thanks x


yay! thank you!!XD


Rukhsar wrote:



These notes have changed my life forever. I will never look at enzymes (or in fact life) the same way again.

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