Proteins and Enzymes Protein movie

Starter – NCEA 2009

Proteins Make up the cell structures and enzymes that control all life processes

Proteins Contain C, H, O, and N Are polymers of amino acids Polymers are long chains of smaller organic molecules (monomers) Peptide bonds link amino acids Proteins make all enzymes (regulate chemical reactions in our bodies)

Haemoglobin is a protein made of 4 polypeptide chains Peptide bond Is formed between amino acids by removing a water molecule ( A condensation reaction) Many amino acids linked by peptide bonds - polypeptide Haemoglobin is a protein made of 4 polypeptide chains

Proteins cont… Functions: storage, transport (haemoglobin in red blood cells) contraction (myosin in muscles), membrane pores, structural support (keratin in hair), enzymes A typical plant or animal cell will have several thousand different proteins, each with a unique role.

Protein Denaturing The weak hydrogen bonds are easily broken, so heat and chemicals can easily denature (destroy the shape of) a protein Proteins can no longer function after being denatured When a protein is denatured the same sequence of amino acids exist, because the peptide bonds were not destroyed Denatured section of a protein, where only the peptide bonds are present

Is a biological catalyst that speeds up biochemical reactions. Enzymes Is a biological catalyst that speeds up biochemical reactions.

What are enzymes? Biological catalysts. Substances that speed up chemical reactions that occur in the cells of living organisms, without them the reactions would occur at a much slower rate. Catalysts are not used up in a reaction, therefore can be used over again and again. They are specific Sensitive to temp, pH and are easily inactivated by certain chemicals.

How Do Enzymes Work? Think of two chemicals Triangle Rectangle The chemicals involved are called substrates Each has a small area in which reactions can occur with other chemicals. This is called the reactive site. For a reaction to occur, these two reactive sites have to be brought together.

How Do Enzymes Work? The chances of the two reactive sites coming together by the random movements of particles in a solution is remote. Eventually it may occur but at a very slow rate that would be useless for an organism. This is where an enzyme comes into action. Active site Enzyme

How Do Enzymes Work? Because of its shape, the enzyme has an area called an active site. This can bring the reactive sites of the triangle and the rectangle (the substrates) together, forming an enzyme-substrate complex.

How Do Enzymes Work? This is known as the lock and key theory. A + B + ENZYME ENZYME- ABCOMPLEX AB PRODUCT + ENZYME This is known as the lock and key theory.

How Do Enzymes Work? The two substrates chemically react, joining together. The enzyme detaches unchanged. The two substrates when detached from the enzyme, joined together. An enzyme can catalyse the splitting of a large molecule in a similar way. Note: the enzyme is very specific (it can only join the rectangle to the triangle)

Model time

Enzymes 2 Use diagrams to illustrate the lock and key model Include the following words in your diagrams Substrate Enzyme – substrate complex product

Induced Fit Theory A more updated theory is the induced fit. When the substrates bind to the enzyme, this may induce a change of shape of the enzyme molecule. The change in shape puts strain on the chemical bonds between the substrate molecules, causing them to react. When the product is released, the enzyme returns to its original shape. The active site is not rigid it changes shape slightly when the substrate is bound

Induced Fit Theory

Millions of reactions take place on the surface of an enzyme in one minute. As there are many reactions going on in a cell, each has its own specific enzyme. There are thousands of enzymes in each cell.

How enzymes work – Lowering the Activation Energy Barrier. In cellular reactions a certain amount of energy is required to get a reaction to start. This is called the activation energy barrier. In an experiment, you can heat two chemicals together, giving them enough energy to react with each other. The bunsen burner, provides the energy required to overcome the activation barrier. What happens in the body???

Lowering the Activation Energy Barrier. The body uses enzymes. Enzymes lower the activation energy barrier and allow molecules with low energy, to take part in reactions at body temperature.

Lowering the Activation Energy Barrier. Overall energy change. Activation energy for the uncatalysed reaction Energy level Activation energy for the same reaction, catalysed by an enzyme. Progress of reaction

Types of Enzymes Some enzymes normally function within body cells (intracellular enzymes) Others work outside cells (extracellular enzymes)

Lesson 2 - starter I have who has NCEA 2008

Lesson 2 - starter I have who has

Factors Affecting Enzymes Temperature pH Concentration Enzyme Substrate Co enzyme ( cofactor) inhibitors

Temperature At low temperatures, the reaction rate is slow. As temperature increases, the action speeds up, as there are more successful collision between the reactants and the enzyme UNTIL an optimum temperature is reached. Action is slowed down until a temperature that is above 50oC, when the protein is denatured – the active site is destroyed or altered so substrate doesn’t fit THIS IS NOT REVERSIBLE.

Temperature Body temis maintained about 37 so biochemical process are maintained. Higher – denature enzymes reactions cease lower temp leads to slowing down of metabolic function

pH pH in cells is usually btwn 7.2 and 7.4 Enzymes are specific to the pH and general work well with in a small pH range

Enzyme Concentration and Substrate Concentration An increase in either concentration increases the rate of enzyme reaction. Higher the substrate more collisions so faster the reaction. But active site becomes saturated with substrate so under these conditions the enzyme cant work any faster.

Co-enzymes/ Co-factor Some enzymes cannot work on their own, require an additional organic molecule – co-enzyme They alter active site or act as a bridge so substrate is more effectively bound Increase the rate of reaction Without them the enzyme wont work or its at a very low rate.

inhibitors Inhibitors or poisons prevent many enzymes working properly eg cyanide, lead or mercury Alter or block the active site so the substrate can not combine properly Prevents the reaction or stops it occurring Enzyme animation