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Presentation on theme: "ENZYMES."— Presentation transcript:


2 Prescribed Learning Outcomes
Chapter 6 (p ) and Chapter 20 (p. 375) 1. Demonstrate an understanding of the following terms: metabolism, enzyme, substrate, coenzyme, activation energy. (p ) 2. Identify the source gland for thyroxin and relate the function of thyroxin to metabolism. (p. 375) 3. Explain the “lock and key” model of enzymatic action. (p. 103) 4. Identify the role of vitamins in biochemical reactions. (p. 105) 5. Differentiate between the role of enzymes and coenzymes in biochemical reactions (p. 105) 6. Apply knowledge of proteins to explain the effects on enzyme activity of pH, temperature, substrate concentration, enzyme concentration, competitive inhibitors, and heavy metals. (p )

3 VOCABULARY _____ Homeostasis _____ Activation energy
_____ Hydrogen carrier _____ Hydrolysis _____ Inhibitor _____ Iodine _____ Lock and key analogy _____ Metabolism _____ Optimum pH _____ Optimum temperature _____ Oxidize _____ pH _____ Structural protein _____ Substrate _____ Temperature _____ Tertiary structure _____ Thyroxin _____ Vitamin _____ Activation energy _____ Active site _____ Allosteric inhibitor _____ Apoenzyme _____ ATP energy _____ Catalyst _____ Co-enzyme _____ Competitive inhibitor _____ Concentration _____ Dehydration synthesis _____ Denature _____ Endothermic _____ Enzyme _____ Enzyme-Substrate Complex _____ Exothermic _____ Functional protein _____ Heavy metal ions

4 INTERESTING FACTS... There are approximately 3,000 of enzymes that exist in our body. Each of them with a specific function. Enzymes help to promote metabolism, and help to catalyze every reaction that occurs in the body (ie: replication, transcription…). Digestive enzymes also play a vital role in food digestion. These enzymes act as sharp knives that cut up the complex foods into smaller units so that it can be assimilated easily into the blood stream. The absorption will then enable our body to reassemble to build new cells and every other molecule our bodies need.

5 INTERESTING FACTS... Since the tight control of enzyme activity is essential for homeostasis, any malfunction or mutation of a single critical enzyme can lead to a genetic disease. A lethal illness can be caused by the malfunction of just one type of enzyme out of the thousands of types present in our bodies. Example #1: PKU. Mutation in enzyme phenylalanine hydroxylase, which helps to digest phenylalanine, results in build-up of phenylalanine. This can lead to mental retardation . Can be controlled by a diet low in phenylalanine. Damage done is irreversible so early detection is crucial.

6 INTERESTING FACTS... Example #2: Mutations in genes coding for DNA repair enzymes. Will cause cancer since the body is less able to repair mutations in the genome. This causes a slow accumulation of mutations and results in the development of many types of cancer in the sufferer.

7 ENZYMES An enzyme is a catalyst (a substance that speeds up a reaction without being consumed). Enzymes are proteins and are reusable. They work in low concentrations and speed up the reaction rate. Starch Glucose Lipids Fatty Acids and Glycerol Proteins Amino Acids Amylase Lipase Protease


9 What Enzymes Do You Know About?

10 ENZYMES Enzymes allow reactions to proceed at lower temperatures than they would normally occur. The reactant(s) that an enzyme acts upon is known as the substrate(s). Enzymes work by forming a very temporary complex with the substrate. This is called the ENZYME SUBSTRATE COMPLEX.


12 ENZYME STRUCTURES Enzymes are large globular proteins with very specific 3-D shapes (tertiary structure). Enzymes have grooves (or pockets), which may contain chemically functional groups. These areas are called active sites and this is where the substrate attaches.


14 LOCK AND KEY MODEL Specific groove shapes and chemical groups in an active site means that enzymes can only bond with one specific substrate or reactant. LOCK KEY

15 ENZYMES This is called INDUCED FIT
When the substrate and enzyme join together, the shape of the enzyme changes, which makes it more reactive. This is called INDUCED FIT

16 COENZYMES Many enzymes are made up of 2 pieces.
1) The APOENZYME – the protein portion (inactive) 2) The CO-ENZYME – a non-protein portion When these join together, the enzyme becomes active and the substrate will now ‘fit’ into the active site..

17 Co-enzymes usually fit into the ALLOSTERIC site, which changes the shape of the active site so the substrate can “fit.”

18 COENZYMES The co-enzymes are often large molecules that the body cannot make on its own. Most co-enzymes are VITAMINS which we get from food or supplements.

19 COENZYMES A typical balanced diet gives you all the vitamins you need, so there is little or no benefit from taking additional vitamin pills. The main exception to this is the vitamin folate, or folic acid, which is mainly found in dark green vegetables like spinach or collard greens. Not surprisingly, this is often deficient in the diet, and so in January 1999 the US government required companies making basic products like flour to add folate to the flour. So now when you eat bread, or pizza, or other common foods you are getting the folate your body needs. So pizza really is health food!

The active site of an enzyme is not an exact perfect fit to the substrate. When the substrate attaches to the enzyme, this causes stress in the substrate, which will cause: A substrate to break apart (in a hydrolysis reaction). Another word for this is CATABOLISM: breaking big molecules in to smaller ones.

21 sucrase

2. Two substrates to form a bond (in a synthetic reaction). Another word for this is ANABOLISM: putting small molecules together to make bigger ones.

23 Anabolism + Catabolism Metabolism

24 Intermediate products
METABOLISM Definition: Metabolism is the constantly occurring chemical reactions that take place in a cell. These chemical reactions occur in organized sequences from reactants to end products with the help of enzymes. This organized sequence of reactions is known as a metabolic pathway. REACTANT Intermediate products PRODUCT

25 ENZYME ACTION Usually, heat is used to speed up chemical reactions by increasing the number of collisions that occur between reactants. Excessive heat, however, destroys the tertiary structure of protein (denatures it). Therefore, heat cannot be used to speed up reactions within living organisms.

26 ENZYME ACTION Enzymes operate by lowering the energy of activation needed for a reaction to occur.

27 no enzyme

28 enzyme

29 ENZYME ACTION Enzymes act as a CATALYST and are not consumed in a reaction. This means that they can be used over and over again.

1. Concentration: The amount of enzyme and/or substrate available to react can affect enzyme activity.

The reaction speeds up as the [substrates] increases, and it levels out when the enzymes are working at the maximum speed (saturation). What can you do to cause an increase in reaction rate? Add enzymes!

The reaction speeds up as you increase the [enzyme], and slows down as the substrate has all been turned into product. What can you do to cause an increase in reaction rate? Add substrate! Enzyme Concentration

2. Temperature: As temperature rises, the reaction rate will increase as the enzymes and substrates bump into each other more often (kinetic molecular theory). At a certain point, the rate of these collisions will be at the fastest rate. This is the OPTIMUM TEMPERATURE. However, once you get above the optimum temperature, the enzyme becomes denatured (changes shape) and no longer functions properly.

34 Most of our enzymes have an optimal temperature of 37oC (body temperature).


36 The antarctic fish trematomus lives under the ice in the antactic ocean. It has large, bulging eyes to collect as much light as possible from the dim sea underneath the ice. The enzymes from these fish are so well adapted to cold environments that they denature (and the fish dies) if the temperature reaches only 5oC. As well as having enzymes that are adapted to the cold, these fish also have special glycoproteins that act as an antifreeze in their blood. This natural antifreeze is 300 times more effective than the antifreeze in your car.

3. pH: The 3D shape of an enzyme can be affected by pH. All enzymes have an optimal pH to work at depending on where they are in the body. Saliva pH 7 Stomach pH 2.5 Intestines pH 8.5 Vagina pH 2.5

When the pH is too low, the positive hydrogen ions interact with the negative R groups in the protein and tear them away. This denatures the enzyme by changing its shape. When the pH is too high, the negative hydroxide ions interact with the positive R groups in the protein and tear them away. This denatures the enzyme by changing its shape. H+ OH-


40 When an animal dies, the body is decomposed by bacteria or fungi
When an animal dies, the body is decomposed by bacteria or fungi. If conditions prevent enzymes in the bacteria from working, the body will be preserved. This photo (Tollund man) shows a body that was discovered in Demark in a peat bog in 1950. The person had been strangled, and at first the police thought it was a recent murder. But peat bogs are very acid, and it turned out that the body was 2,000 years old, and had been very well preserved in the peat. Archaeologists believe the body is from a ritual murder, but they are not sure if the person was killed as a punishment, or whether the body was a sacrifice to the gods.


Inhibitors: Chemicals that interfere with the enzyme action. There are two types of INHIBITORS: a) Competitive Inhibitors b) Non-Competitive Inhibitors

Allosteric Site

44 Competitive Inhibitors are chemicals that so closely resemble an enzyme’s normal substrate that it can attach to the enzymes active site. The substrate and inhibitor “COMPETE”. If the inhibitor occupies the active site of the enzyme, the substrate will not be able to join and no product will form from that enzyme. If the Inhibitor is removed, the enzyme will become active again.



47 Enzyme inhibitors are important commercially in many ways
Enzyme inhibitors are important commercially in many ways. For example pesticides kill bugs by inhibiting essential enzymes that are present in insects ( these enzymes are not found in humans) and herbicides kill weeds by inhibiting some of their important enzymes.

48 Similarly many medications, such as aspirin and antibiotics are inhibitors.
The enzyme substilin digests proteins, and is used in laundry detergent. Rennin, an enzyme extracted from calves, is used in curdling milk to make cheese. Glucose oxidase detects glucose in the urine (for example in diabetics).

49 Non-Competitive Inhibitors are atoms or molecules that attach to an enzyme at an allosteric site and this denatures the enzyme. Non-competitive inhibitors will sometimes destroy an enzyme by permanently binding to the allosteric site. An example of this is heavy metals, such as lead in the nervous system.



52 Rate of Reaction [substrate]

53 The enzyme will be denatured and the reaction will stop.
Another type of non-competitive inhibition is when a metabolic product can feedback on a metabolic pathway to control how much product is made. The final product can temporarily attach to the allosteric site on the first enzyme. The enzyme will be denatured and the reaction will stop.

When the concentration of the final product gets low again, there will be less inhibition on the enzymes and the metabolic pathway is reactivated.

55 Feedback Inhibition & Control of Metabolic Rate
Thyroxin, the hormone that controls the metabolic rate of all of the cells in your body, is produced by the thyroid gland in the neck. If the concentration of thyroxin in your body is high, your metabolic rate will be raised, and if thyroxin levels are low, your metabolic rate will be low. The thyroid gland is stimulated to release thyroxin by a hormone produced in the pituitary gland called TSH (thyroid stimulating hormone). But the enzymes in cells of the pituitary that make TSH are inhibited by thyroxin.

56 Feedback Inhibition & Control of Metabolic Rate
Therefore, if thyroxin levels are high, the pituitary stops producing TSH, and if thyroxin levels are low, the pituitary makes the TSH. Thus, the metabolic rate of cells in your body are maintained by the feedback inhibition of an enzyme



59 (Increased Metabolic Rate)
- Pituitary Gland TSH Thyroid Gland Thyroxin Body Cells (Increased Metabolic Rate)

60 Hypothyroid


62 Hyperthyroid Palpitations Heat intolerance Nervousness Insomnia
Breathlessness Increased bowel movements Light or absent menstrual periods Fatigue Fast heart rate and trembling hands Weight loss Muscle weakness Warm moist skin Hair loss Staring gaze Hyperthyroid


64 SLOTHS Because of their sloe rate of metabolism they only need to go the bathroom once a week. Sloth digestive processes work very slowly, because their food is difficult to process, and because their body temperatures fluctuate every day. Wild sloths have been found to have deep body temperatures ranging from 28 degrees C to 40 degrees C. They can raise their body temperature by basking in sunlight, but must also move to shade as they become too warm. Thus they practice thermoregulation in much the same way that lizards do. They depend on chemical processes used by bacteria in their gut to digest their food. Since chemical processes slow down as temperatures decrease, the night-time drops in temperature which usually cause a body temperature drop of about 7 degrees C, reduce their rates of digestion. Indeed, the rainy season weather is thought to present problems for sloth digestion, and most dead sloths on BCI are found in the October- December rainy period. Also, few trees have new leaves at this time, which means that although there are many leaves, they are difficult to digest. Sloths may starve at this time of the year, even with full bellies. Their digestion is so slow that it takes several days or longer for food to pass through their gut, and they eliminate waste only about once every 8 days, moving to the ground briefly to defecate. Compared with other mammal species that eat plants, sloths have the slowest rate of passage of food through the gut, a process that usually takes hours. The three-toed sloths use their short tail to dig a hole and then bury their feces, but the two-toeds have no tail and dig no latrine hole. This is a very odd behavior for arboreal animals that otherwise rarely descend to the ground Likewise the sloth. Their metabolism is so slow that they may take a half a minute to move a leg a few inches. Their digestive system is so slow that they need only defecate about once a week. They even sneeze slowly. Being so slow, and indeed entirely immobile for much of the time, they are almost invisible to predators. By keeping such a low profile they avoid running into dangerous confrontations. As a result, they enjoy a high survival rate, and are one of the commoner animals in the rainforests. By keeping a slow and low profile, sloths save themselves from many dangers. But such a lifestyle has serious drawbacks. Sloths just don't get much done in life. Their birthrate is low, with a single young born once a year. They can't do much for their kids anyway -- a mother rushing to help her threatened infant was timed at 14 feet per minute. They don't get to see much of the jungle, and while it's true that animals don't really achieve things anyway, sloths achieve less than most. The three-toed sloth has very unusual habits. It lives high up in trees of the canopy, sleeping and eating buds, leaves and young twigs. In fact the three-toed sloth sleeps for 19 hours a day hanging up-side down on branches. The three-toed sloth doesn't move around a lot because it can only move 6 feet a minute, so sometimes the three-toed sloth has to stay in the same tree for years. Even though the three-toed sloth is so slow, it is a preety good swimmer. If you think the three-toed sloth is related to monkeys, then you're wrong. The three-toed sloth is actually not related to monkeys but to anteaters and armadillos. All of them are apart of a group called Edentata which means without teeth. Even though the three-toed sloth is related to anteaters and armadillos, it sure doesn't look like one. The three-toed sloth has almost no tails or ears, its nose is blunt, and it has a grayish color which makes it hard to see among the branches. The three-toed sloth is a very strange animal and home to a variety of other creatures. One sloth was discovered to have three beetles, six mites, and three moths living in its fur. Another sloth was found to have 978 beetles living on it. Although the sloth is so slow it can escape its predators pretty easily. The sloths main predators are jaguars and ocelots, but for them it's hard to see the sloth with green algae on its fur that camouflages with green leaves.

65 Modern sloths live upside-down in the forests of South America and eat leaves in trees.
They have claws to help them remain sleeping and suspended underneath branches for hours.  A sloth's grip on its branch is so secure that in death it continues to hang unless it is forcibly unhooked. Sloths are generally nocturnal and move around little when awake.  When they do move, it is at a slow and deliberate speed. 

66 Sloths have a very slow metabolism and take their sweet time digesting food (1-2 weeks per meal) and consequently, only defecate once in a one week period.  Their metabolism is so slow that they may take a half a minute to move a leg a few inches. Their digestive system is so slow that they need only defecate about once a week. They even sneeze slowly. Being so slow, and indeed entirely immobile for much of the time, they are almost invisible to predators. By keeping such a low profile they avoid running into dangerous confrontations.

67 However, sloths just don't get much done in life
However, sloths just don't get much done in life. Their birthrate is low, with a single young born once a year. They can't do much for their kids anyway -- a mother rushing to help her threatened infant was timed at 14 feet per minute. The slow or low rate of metabolism in sloths effects their ability to fight off illness.  Most sloths have difficulty surviving when in captivity outside of their natural range because they cannot fight off new diseases or adapt to a colder climate. 

68 Metabolism and ATP Most cell reactions (metabolism) require energy to occur. The energy ‘currency’ of cells is a molecule called ATP. ATP has 3 phosphates, the last two of which are held together by a high energy bond. It takes a lot of energy to make this phosphate bond, and energy is released when the bond is broken.

69 Metabolism and ATP

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