Ch 9 Metabolism

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Syllabus – What do you need to know…..

1.Define the term: metabolism.2.State that solar energy is source of energy

on Earth.3.State that cellular energy sourced from

chemical energy in ATP

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4. Define the term: enzymes5. State the nature, folded shape & functions of

enzymes.6. Explain the role of enzymes in plants and

animals including role in metabolism7. Explain the effects of pH & temperature on

enzyme activity.8. State the procedure and advantages of Bio-

processing.9. State the use of Bio-processing.

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10. Explain the active site theory to examine enzyme function & specificity.11. Explain the term optimum activity with reference to temperature.12. Explain the nature of heat denaturation13. Explain the active site theory to examine enzyme function & specificity.14. Explain the term optimum activity with reference to temperature.15. Explain the nature of heat denaturation

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MetabolismQuestion:When we speak about metabolism what do we

mean?

Answer:Metabolism describes all the chemical

reactions in our bodies

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Question:What kind of chemical reactions do you think

take place in our bodies?

Answer:1.Growth (making proteins)2.Response (nerve reactions)3.Movement (energy needed from respiration)

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Homeostasis • 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.

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Learning check1. What is meant by metabolism?2. Can you name some example of metabolism

in the human body3. What word describes the maintenance of

reactions in our body?

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Cellular Energy• is contained in bonds found in molecules such

as carbohydrates• When the bonds are broken down, energy

is released during respiration in the mitochondria

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Catabolic Reactions break down complex substances into simpler ones and release energy. E.g. respiration and digestion

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Anabolic Reactions consume energy as they build larger, more complex, molecules from smaller ones e.g. Photosynthesis and muscle growth from amino acids are examples of anabolic reactions.

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Enzymes can be either anabolic or catabolic.•An example of a catabolic enzyme is amylase. Amylase converts starch into maltose.•An example of an anabolic enzyme is DNA polymerase. This enzyme repairs (rebuilds) DNA.

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In SummaryCatabolic: Respiration breaks down glucose and releases this energy from the bonds

Anabolic: Photosynthesis in plants builds up molecules with energy rich bonds (glucose)This is how plants provide energy from the sun for everything else on earth!

Remember C.R.A.P. ! 13

Learning check1. Where does cellular energy refer to?2. In which organelle does it occur in?3. What does the term catabolic reaction

mean?4. What does the term Anabolic reaction

mean?5. Can you give an example of each type?

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EnzymesEnzymes

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EnzymesEnzymesQuestion:What are enzymes?Answer:Proteins that function as biological catalysts

are called enzymes.Enzymes control cellular reactions.A catalyst speeds up a reaction without being

used up in the reaction.

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are named by adding ‘-ase’ to the name of their substrateExamples:•The enzyme that acts on Amylose (starch) is called amylase•The enzymes that act on proteins are called proteases

Naming Enzymes

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Examples are:• Lactase – breaks down lactose (milk sugars)• diastase – digests vegetable starch • sucrase – digests complex sugars and starches • maltase – digests disaccharides to monosaccharides (malt

sugars) • glucoamylase – breaks down starch to glucose• protease – breaks down proteins found in meats, nuts, eggs,

and cheese• lipase – breaks down fats found in most dairy products, nuts,

oils, and meat • cellulase – breaks down cellulose, plant fibre; not found in

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EFFECTS OF ENZYMES

1. Enzymes lower the activation energy. This is the energy input needed to bring about the reaction. Enzymes enable the reaction to occur with less energy than would be needed if the enzyme were not present.

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EnzymesEnzymes

FreeEnergy

Progress of the reaction

Reactants

Products

Free energy of activationFree energy of activation

Without Enzyme

With Enzyme

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2. Regulate the thousands of different metabolic reactions in a cell and in the organism.

3. The cell activity is determined by which enzymes are active in the cell at that time.

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Learning Check1. What is an Enzyme?2. What are catalysts?3. To what group of bio-molecules do enzymes

belong?4. Name 3 enzymes.5. What are 3 effects of enzymes?

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How do Enzymes work• Enzymes are folded in GLOBULAR SHAPES. • The enzyme’s shape enables it to receive only

one type of molecule; that molecule that will fit into it’s shape.

• The place where the substance fits into the enzyme is called the active site and the substance that fits into the active site is called the substrate.

• Enzyme action occurs when the enzyme and substrate collide forming a product.

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What Affects Enzyme Activity?Factors that affect enzymes include:1.pH2.Temperature3.Substrate concentration4.Enzyme concentration

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pH

• pH scale goes from 0 -14• 0-7 is acidic • 7-14 is basic (or alkaline)

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acid neutral base

0 7 14

• Most enzymes work best at a pH of 6-8.• A change in pH disrupts an enzyme's shape

and structure, causing it to become less effective.

• The ideal (optimum) pH for most enzymes is 7.

• Stomach enzymes e.g. Pepsin work in an acidic environment of pH 2

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• At 0°C enzyme action is low because the movement of molecules is low.

• Increasing the temperature, speeds up the movement of molecules and increases enzyme activity.

• Human enzymes work best at 37°C.• Plant Enzymes work best at 20-30°C.

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Temperature

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TEMPERATURE AND RATE OF ENZYME ACTION

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Industrial use of Enzymes• 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.

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Some products of Bioprocessing

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Immobilised enzymes • 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:1.attached to each other or 2.an insoluble substance or 3.enclosed in a membrane or gel.

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The benefits of immobilised enzymes are:

1. they may be reused2. they are easy to separate from the product

(therefore it is easy to purify the product)3. they are often more stable than the natural

enzyme4. the process is cheaper5. their efficiency is not reduced6. can provide increased resistance to

changes in conditions such as pH or temperature.

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How to immobilise enzymes• The enzyme is held

in place / trapped in a gel e.g. Sodium alginate.

• This allows substrates in and products out.

• Immobilised enzymes are then used in bioreactors.

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USES OF IMMOBILISED ENZYMESProducts derived from immobilised enzyme action:1.Fructose produced from glucose: Fructose is sweeter than glucose and is used in soft drinks and other sweet products.2.Antibiotics: Enzymes are used to change penicillin into new, wider used, antibiotics.3.Sewage Treatment: Instead of bacteria enzymes can be immobilised and used.

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Learning Check1. What is bio-processing?2. What type of organisms are usually used in

bio-processing?3. Why is bio-processing advantageous?4. What are the advantages of immobilising

enzymes?5. Can you name 3 things immobilised

enzymes are used for?39

Enzymes – Advanced Study

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The place where the substance fits into the enzyme is called the active site and the substance that fits into the active site is called the substrate.

Enzyme

Substrate

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Active Site

• Enzyme action occurs when the enzyme and substrate collide.

• The substrate slots into the active site of the enzyme.

• When the substrate joins with the enzyme the entire structure is called the enzyme-substrate complex.

• The substrate becomes changed by the enzyme’s action and is then releases as the product.

• The enzyme is then free to join another substrate. 42

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Induced Fit Model.• Sometimes the shape of the active site must

be slightly changed. This situation is called the Induced Fit Model.

• The enzyme’s active site has a shape closely complementary to the substrate.

• The substrate locks into the active site of the enzyme.

• The active site alters its shape holding the substrate more tightly and straining it.

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• An enzyme-substrate complex is formed. • The substrate undergoes a chemical change

and a new substance, product, is formed. • The product is released from the active site.• The free unaltered active site is ready to

receive a fresh substrate.

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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

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Mechanism of Enzyme action (Induced fit model)

1. The substrate combines with the active site of the enzyme

Active Site

Substrate

Enzyme

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2. The active site is induced or caused to change shape slightly

Active Site

Substrate

Enzyme

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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

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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

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Enzyme ReactionEnzyme Reactionsubstrate (sucrose) + enzyme (sucrase)

enzyme-substrate complex

and +sucrase

glucose fructose

products + enzyme

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Consider This• Amylase is an enzyme found in saliva. It

breaks starch molecules into smaller maltose molecules

• What is the substrate?• What is the product?• Will amylase break fats into fatty acids +

glycerol? Why?• Is this an example of a catabolic or an

anabolic reaction? Why?52

Learning Check

1. What is meant by saying that “enzymes are specific”?

2. What is meant by a substrate?3. What is the area of the enzyme that the

substrate combines with called?4. What is meant by the Induced Fit model?

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Learning Check

1. Can you describe how enzymes and their substrates fit together?

2. What is this model of enzyme action called?

3. Can the enzyme work on more substrate once the products have been formed?

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The effect of pH on Enzyme action

• When the pH changes an enzyme's structure, the enzyme can't do its job.

• Changes in pH break the Hydrogen bonds that maintain an enzyme's shape.

• An enzyme will unravel, or denature, and become useless in a different pH.

• Each enzyme has an optimum pH.

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• Increasing the temperature will increase the rate of reaction of the enzyme and substrate.

• But too much heat can damage the bonds that hold the shape of the proteins

• This could lead to denaturation of the protein and thus inactivate the protein

• Causing a decrease in the rate of the enzyme catalysed reaction.

• Each enzyme has an optimum temperature.56

The effect of Temperature on Enzyme action

DenaturationProteins lose their 3 dimensional shape when they are 1.heated above 50 C⁰ or 2.treated with certain chemicals or 3.radiation This means they will not be able to form the enzyme substrate complex

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Learning Check

1. What factors affect enzyme action?2. What is the best temperature for (a) human

enzymes and (b) plant enzymes to work at?3. What is meant by pH?4. What is meant by Optimum?5. What is meant by denaturation?

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• Yeast contains the enzyme sucrase. • This enzyme is immobilised by:1.mixing yeast with sodium alginate2.adding beads of the mixture to calcium

chloride3.filtering and rinsing the hardened beads

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• The application of an immobilised enzyme is shown by:

• adding sucrose solution to immobilised yeast

(containing sucrase) in a separating funnel

• testing for the production of glucose

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A movie on the action of Enzymes!

• http://www.bishopstopford.com/faculties/science/arthur/?sortby=3

• http://www.angelo.edu/faculty/nflynn/Biochemistry/

http://www.angelo.edu/faculty/nflynn/Biochemistry/

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• To investigate the effect of pH on catalase activity

• mix blended or chopped celery (catalase), hydrogen peroxide, pH buffer 4 and washing-up liquid

• note the volume of froth formed after 2 minutes at different pH values.

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• To investigate the effect of temperature on the rate of catalase activity:

• mix blended or chopped celery (catalase), hydrogen peroxide, pH buffer 9 and washing-up liquid

• note the volume of froth formed after 2 minutes at different temperatures

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• The effect of heat denaturation on catalase can be investigated by:

• boiling catalase• testing if it will then form froth when it reacts

with hydrogen peroxide

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• ADP (adenosine diphosphate) is a low-energy molecule;

• ATP (adenosine triphosphate)

is an energy-rich molecule.

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• ATP is the source of energy used for most cell reactions.

• ADP and ATP are interconvertible, i.e.• ADP + energy + P → ATP + water• ATP + water → ADP+ energy + P• Phosphorylation

is the addition of phosphate to a molecule.

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• NADP+ is a low-energy molecule;

• NADPH is a high-energy molecule.

• Both molecules are involved in photosynthesis.• NADP+ and NADPH are interconvertible i.e.• NADP+ + energy (high-energy electrons) + H+→ NADPH• NADPH → NADP+ + energy (high-energy electrons)

+ H+• Respiration uses

NAD+ (instead of NADP+)and NADH (instead of NADPH).

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END

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