Metabolism Metabolism describes all the chemical reactions in our bodies e.g. growth, response, movement etc. Metabolism: is sum of all the chemical reactions in the body. The way our metabolism functions is extremely important as our bodies need to have constant and stable conditions The maintenance of stable conditions in our bodies is called homeostasis

Reactions that involve breaking big molecules into smaller molecules and release energy and are called catabolic Eg. Respiration Reactions that involve making bigger molecules out of smaller ones molecules and use up energy and are called Anabolic Eg. Photosynthesis

Sources of Energy: 1. Solar Energy The main source of energy for all life is the sun Solar Energy = is energy from sun Certain pigments such as chlorophyll can absorb light When they absorb light they use it to form the chemical bonds in biomolecules such as carbohydrates

2. Cellular Energy This is the energy released by the reactions in a cell from energy stored in bonds of biomolecules (food) When bio molecules such as carbohydrates are broken down the bonds are broken and energy is released = Respiration Some of this energy is used by the cell and the rest is lost as heat

Photosynthesis in Plants builds up molecules with energy rich bonds (glucose) Respiration breaks down glucose and releases this energy from the bonds This is how plants provide energy from the sun for everything else on earth!

Enzymes Catalysts: chemicals that speed up reactions without getting used up themselves in the reaction Enzymes are catalysts made of protein they speed up a reaction without being used up themselves in the reaction Because enzymes are made in living things they are called biological catalysts (or organic catalysts)

An Anabolic Enzyme: enzyme involved in an anabolic reaction (building up reaction) DNA Polymerase forms and repairs DNA Anabolic as it converts simpler molecules into more complex molecules Found in almost all living things

A Catabolic Enzyme: an enzyme involved in an catabolic reaction (breaking down reaction) Amylase converts starch to maltose Catabolic as it breaks a big molecule into a smaller one It is produced by saliva glands in mouth and by the pancreas

Naming Enzymes Enzymes are named by adding the suffix ase to the name of their substrate Eg. Enzyme that acts on Amylose (starch) is called amylase Enzymes that act on proteins are called proteases

Most reactions take place in a number of steps which need to be carefully controlled if the cell is to function properly Enzymes are the most important controllers of cellular reactions

The function of a protein is decided not only by the sequence of amino acids but also by the way the protein folds Most enzymes are globular proteins Enzymes are not flat they have a 3D globular folded structure

How enzymes work.. Each enzyme has its own specific shape that will only “fit” the molecule that the enzyme is designed to work on If the enzyme that breaks starch into glucose meets a fat molecule it will not fit it and will not be able to work on it

Enzyme Specifity Enzymes are specific to a substrate. This means that each enzyme fits a particular substrate so will only work on a particular substrate.

Enzyme Action The substance that an enzyme acts on is its substrate The substance(s) that the enzyme forms is called the product(s)

Enzymes will only work if they have the correct shape to fit the substrate. They have a complex 3 dimensional folded shape to fit the substrate pH and temperature can change the shape of enzymes so can effect how they work.

How enzymes work? (Basic) When enzymes and their substrates meet and come together they form an Enzyme/Substrate complex When they product is formed the Enzyme/Substrate complex breaks up. The products are released and the enzyme remains unchanged ready to be used again.

How enzymes work? (Basic)

Enzyme Reactions are reversible Like a key can open or close a lock enzymes can make reactions go in either direction

In the following example the enzyme can break molecule X into Y+Z but it can also combine Y+Z to form X X Y + Z

The Active Site The Active site is the part of the enzyme that combines with the substrate

Lock and Key vs. Induced Fit Model Lock and Key: Active site is fixed shape/ rigid Contrary to belief the active site is not a rigid shape that is fixed to fit the substrate Induced Fit Model: Active site moulds around substrate When the substrate enters the active site it causes it to change shape slightly The enzyme then fits more precisely around the substrate this is known as the Induced Fit model of enzyme action

The Bean Bag Theory! The induced fit model can be compared to the way a bean bag will adapt to fit snugly around our body shape when we sit in it

Mechanism of Enzyme action (Induced fit model) 1.The substrate combines with the active site of the enzyme Active Site Substrate Enzyme

2. The active site is induced or caused to change shape slightly Active Site Substrate Enzyme

3. The substrate and enzyme form an enzyme substrate complex The bonds in the substrate are altered so that the substrate changes into the products Enzyme Substrate complex Substrate changed to products which are released

4. The products leave the active site. The active site returns to its original shape and is ready for a new substrate molecule Active Site New Substrate Enzyme Products

Enzymes at work! Enzymes work best in certain conditions Factors that affect enzymes include: Temperature pH Substrate concentration Enzyme concentration

Optimum Conditions Optimum temperature refers to the temperature at which the enzyme will work best Optimum pH refers to the pH at which the enzyme will work best and so on What do you think body enzyme’s optimum temperature is?

Temperature At very low temperatures ice forms, liquids become solids and enzymes can’t work As temperature increases molecules start to move and bump into each other causing the rate of reaction to increase

Human enzymes work best at body temperature (37°C) Plant Enzymes work best at °C Above certain temperatures enzymes start to lose their shape the rate of reaction falls When the shape is fully lost the enzyme is said to be denatured this is usually a permanent condition

Temperature Enzyme activity increases with an increase in temperature until the enzyme reaches it’s point of denaturing when it stops working permanently

pH pH scale goes from is acidic 7-14 is basic (or alkaline)

Enzymes work over a very narrow pH Most enzymes work at pH 6-8 Outside this they lose shape and get denatured The optimum or best ph is usually pH 7

An Exception! Is our stomach acid or basic? Do you think there are enzymes in our stomach? Pepsin is an enzyme in the stomach that works best at pH 2!

Denaturation When most proteins are heated to high temperatures or treated with certain chemicals or radiation they will gradually lose their 3 dimensional shape This means they will not be able to form the enzyme / substrate complex

Denaturing: When an enzyme has permanently lost it’s shape and no longer works it is denatured (generally due to heating too much) Questions: How does heat denature an enzyme? Did you do this in an experiment?

Inhibitors Inhibitors attach to enzymes and destroy their shape When this happens the enzymes are said to be denatured

Nerve Gases The nerve gases we hear of terrorists using are often inhibitors that attach to enzymes involved in our nerve transmissions

Poisoning people the old fashioned way! Cyanide denatures an enzyme involved in respiration

Beneficial Inhibitors Insecticides affect enzymes in insects causing their death Drugs can affect enzymes involved in pain causing the pain to stop Antibiotics can affect enzymes in bacteria causing the bacteria to die

Bioprocessing Bio-processing is the use of enzyme controlled reactions to produce a product Bio-processing can be used to produce a vast range of products such as cheeses, beer, antibiotics, vaccines, methane gas, food flavours, vitamins and perfumes

Traditionally micro-organisms such as bacteria and yeast were used but since the 1900’s and especially since the 1950’s enzymes are being used

Bioreactor : a vat/ vessel in which biochemical reactions take place

Immobilised Enzymes An immobilised enzyme is an enzyme that is trapped inside a gel.(Substances can diffuse in and out of the gel however the enzyme is trapped inside)

If enzymes are used freely dissolved in a vessel it can be very wasteful as they are lost at the end of the process To prevent this problem enzymes are often immobilised or fixed This means they are attached to each other or an inert substance and can be used repeatedly

How to immobilise enzymes Physical methods Adsorption where enzymes are physically attached to inactive supports such as glass beads or ceramics Enclosed by a membrane when enzymes are kept within a membrane Trapped in a gel, sodium alginate is commonly used this allows substrates in and products out

Chemical Methods Bonded to a support enzymes chemically bonded to a support such as glass beads or ceramics Bonded to each other Enzymes are chemically bonded to each other

Advantages of Immobilised Enzymes Efficiency of enzyme is not affected Immobilised enzymes can be easily recovered from the product so you can get a pure sample of product easily Immobilised enzymes can be reused this cuts costs Enzymes frequently become more stable when immobilised

Uses of Immobilised Enzymes Used to convert corn starch to corn syrup Immobilised isomerase converts glucose to fructose which is used to sweeten drinks

Penicillin acylase changes the structure of penicillin to make more antibiotics that will fight a wider range of bacteria

Lactase converts lactose to sweeter sugars glucose and galactose which are then used by food manufacturers