F4 Biology teaching notes Ch 4: NE 14 - 16

1^st Term NE 14
4    Enzyme and metabolism酶和新陳代謝                             

4.1  Metabolism新陳代謝 (Book 1A, p. 4-3)

Metabolism = the sum of (1) chemical reactions that take place in an organism
Catabolism (分解代謝)	Anabolism (合成代謝)
Ø   The (2) breaking-down / building-up reactions in an organism. Ø  Energy is (3) released / required.	Ø   The (4) building up reactions in an organism. Ø  Energy is (7) required.

4.2  The role of enzymes酶 in metabolism (Book 1A, p. 4-4)

http://www.sumanasinc.com/webcontent/animations/content/enzymes/enzymes.html (動畫: 激活反應)

Ø  For every reaction, a certain amount of energy must be supplied to the reactants before the reaction can

occur. This is called the (1) activation energy (活化能).

Ø  In our body, (2) enzymes function as (3) catalysts (催化劑):  

n to (4) raise / lower the activation energy

n so that chemical reactions can take place at body temperature at a faster rate. 

A How do enzymes work? (Book 1A, p. 4-7)

Ø Enzymes are (1)protein in nature and have a (2)specific 3-D structure (三維構造).

Ø On each enzyme molecule, there is an (3) active site (活性部位) which allows he enzyme only binds to (4)substrate (受質) molecules that fits shape.t

Ø The substrate molecule(s) bind to the active site of an enzyme to form an (5)enzyme-substrate complex (酶受質複合物).

Its formation (6)lowers the activation energy of the reaction.

Ø The substrate(s) are converted into (7) products. The enzyme molecule is released in its (8) original form. Its structure has no change after the reaction.

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html (動畫: 酶受質複合物)

Ø The specificity (專一性) of enzyme actions can be explained by

the (9)lock-and-key hypothesis (鎖鑰假說).

nThe active sites of enzymes only bind with specific (10)substrates

nThe fitting process is similar to that between key and (11)lock

http://www.kscience.co.uk/animations/anim_2.htm (動畫: 鎖鑰假說及解釋)

1^st Term NE 15

C What are the properties of enzymes? (Book 1A, p. 4-8)                                 

Property	Description / Explanation
Enzymes are biological (12)catalysts.	Enzymes speed up metabolic reactions by lowering the (13)activation energy of the reactions.
The actions of enzymes are (14) specific.	An enzyme only acts on substrates that fit into its (15) active site.
Enzymes are (16) proteins.	n  The structures and hence the activity of enzymes are easily affected by (17)temperature and pH. n  Most enzymes are (18) denatured (變性) and lose their functions at high temperatures and extreme極端 pH conditions
Enzymes are (19) reusable.	n The binding between enzymes and substrates is (20) permanent永久 / temporary暫時性 n Enzymes remain (21) unchanged after reactions. They can bind to other substrate molecules after the reaction is complete.
Enzymes are needed in relatively (22) small amounts.	because enzymes can be (23) reused.

4.4  Factors affecting the rate of enzymatic reactions (Book 1A, p. 4-10)

Ø  The (1)rate of enzymatic reaction reflects the activity (活性) of enzyme. It can be measured by the rate of:

n  the consumption of substrates

n  the formation of products (生成物) DSE-2014-IB Q6)(c), CE-2003-I Q3(b)

A  Temperature (Book 1A, p. 4-10)  CE-2008-I-A Q6

Temperature	Effect on the rate of enzymatic reaction
Low temperature	n enzymes are (2) inactive (不活躍). The enzyme and substrate molecules move slowly and the chance for them to (3) collide with each other is low. Therefore, the reaction rate is (4)low.
As the temperature rises	n both enzyme and substrate molecules move around more rapidly and (5) collide with each other more frequently n the chance of formation of (6) enzyme-substrates increases n as a result, the rate of enzymatic reaction (7) increases.
(8) (最適溫度)	The rate of enzymatic reaction reaches a maximum
High temperatures	n may cause (8) conformational change (i.e. a change in shape) in the active site of the enzyme molecule. n The enzyme is said to be (9)denatured. n The substrate molecule can no longer fit into the active site of the enzyme. As a result, the rate of the enzymatic reaction (10)decreases.

https://www.youtube.com/watch?v=EOu394F8gIA (蛋白結構與變性)

http://www.youtube.com/watch?v=3IL_Df5ouUc&feature=PlayList&p=E2AF1FC6A4091D0B&playnext=1&playnext_from=PL&index=28 (youtube: 蛋白變性)

B  pH (Book 1A, p. 4-12)   AL-2005-I-A Q5 

n   Most enzymes work in a (11) wide / narrow range of pH. They work best at their (12) optimum pH.

n   An unsuitable pH will cause (13) denaturation of the enzyme, and therefore (14)decreasing the rate of the enzymatic reaction.

1^st Term NE 16

C  Inhibitors抑制劑 (Book 1A, p. 4-15) 

AL-2007-I-A Q3, AL-2004-I-A Q4, AL-2003-II-A Q2

n (15) Inhibitors (抑制劑) are chemicals that can decrease

the rate of enzymatic reactions.

nExamples: Cyanides and (16) heavy metals (重金屬)

such as mercury ions, lead(II) ions and copper(II) ions

4.5  Applications of enzymes (Book 1A, p. 4-18)

Ø Enzymes produced by organisms also work well outside the organisms.

Ø They are extracted and used to produce various commercial products.

Ø Examples of products and the enzymes used:

Products	Enzyme used and its action
Biological washing powders 生物活性洗衣粉	Protease蛋白酶 and lipase脂肪酶 help remove stains污漬.
Stonewashed jeans (石磨藍牛仔褲)	Cellulase纖維素酶 breaks down cloth fibres.
Contact lens cleaners	(1)Proteases can remove the protein dirts on contact lens.
Meat tenderizers 鬆肉粉	(2)Papain extracted from papaya木瓜 (a kind of protease) can soften meat.
Cheese	Rennet (a kind of protease) can (3)coagulate凝結milk.
Fruit juices	Pectinase (果膠酶) can break down pectin of plant cells and clarify fruit juices

Ø Advantages and limitations of using enzymes in the production of commercial products:

Advantage

Limitation

n Enzymes can speed up chemical reactions. This (4) shortens the production time and allows the (5)mass production of products. n Enzymes are (6) specific in action. This can reduce the production of (7) unwanted products. n Enzymes are (8)reusable and are needed in small amounts only. This lowers the (9)cost of production. n Many enzymes work at (10) moderate conditions. Using enzymes in the production processes does not require extreme conditions.

nEnzymes are sensitive to (11) temperature / pH and (12) pH / temperature changes. High temperatures and unsuitable pH can cause (13) denaturation of enzymes. n Enzymes are easily affected by (14) inhibitors. All containers that are used in the production processes have to be (15) cleaned. This prevents the containers from (16) contaminating with inhibitors.