Term
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Definition
| A globular protein functioning as a biological catalyst, speeding up reaction rates by lowering activation energy. |
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Term
| Explain enzyme-substrate specificity. |
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Definition
- each globular enzyme includes an active site with a specific, three-dimensional shape which is complementary to the shape of the substrate
- the globular enzyme active site also includes a specific set of charges which are complementary to the charges of the substrate
-thus, through complementarity of shape and charge, the substrate is attracted to, and fits precisely into, the active site
- the precise interactions between enzyme active site and substrate are essential for the catalytic properties of enzymes to function; the complementarity is often referred to as analogous to the fit between a lock and a key
- enzymes vary in specificity from being exclusive to a single substrate to being generalized to accept any molecule of a certain type |
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Term
Explain the effects of temperature, pH and substrate concentration on enzyme activity.
Reasons why enzymes are altered by environmental conditions. |
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Definition
- each enzyme has a highly specifically shaped active site which is complementary to the shape of its substrate; catalysis depends on this complementarity
- the enzyme active site is a product of its tertiary, or three-dimensional structure, which is in turn produced by a variety of bonds: covalent, ionic and hydrogen bonds as well as hydrophobic interactions
- each enzyme active site best fits its substrate at a set of optimum conditions
- deviation from optimum conditions alter the bonds which produce the tertiary structure of the enzyme, thus altering the shape of the active site and its complementary fit to its substrate |
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Term
Explain the effects of temperature, pH and substrate concentration on enzyme activity.
pH |
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Definition
- both acids and alkalis denature enzymes
- stomach pepsin is optimized at pH = 2
- pancreatic lipase is optimized at pH = 8 |
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Term
Explain the effects of temperature, pH and substrate concentration on enzyme activity.
Temperature |
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Definition
- at lower temperatures, all chemical reactions proceed more slowly, with a general rule of doubling reaction rates with each 10 degrees Celcius increase
- at higher temperatures, the excessive energy break bonds that would otherwise create the shape of the active site; thus denaturing the enzyme |
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Term
Explain the effects of temperature, pH and substrate concentration on enzyme activity.
Substrate concentration |
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Definition
- at low to medium substrate concentrations, enzyme activity is directly proportional to substrate concentration; this is because random collisions between substrate and active site happen more frequently with higher substrate concentrations
- at high substrate concentrations, all the active sites of the enzymes are fully occupied, so raising the substrate concentration has no effect |
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Term
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Definition
| - a change in the structure of an enzyme so that it can no longer carry out its function |
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Term
Explain the use of lactase in the production of lactose-free milk.
Lactase in producing lactose-reduced milk |
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Definition
- lactose is the sugar that is naturally present in milk
- lactase is obtained by artificially culturing a fungus, Kluveromyces lactis
- the fungus grows naturally in milk, where it uses lactase to hydrolyze lactose into glucose and galactose
- biotechnology companies culture the yeast, extract the lactase from the yeast, and purify it for sale to food manufacturing companies |
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Term
Explain the use of lactase in the production of lactose-free milk.
There are several reasons for using lactase in food processing. |
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Definition
- some people are lactose-intolerent and cannot drink ore than about 250mL of milk per day, unless it is lactose-reduced
- galactose and glucose are sweeter than lactose, so less sugar needs to be added to sweet foods containing milk, such as milk shakes or fruit yoghurt
- lactose tends to crystallise during the production of ice cream, giving a gritty texture; because glucose and galactose are more soluble than lactose they remain dissolved, giving a smoother texture
- bacteria ferment glucose and galactose more quickly than lactose, so the production of yoghurt and cottage cheese is faster |
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