chapter 5: enzymes Flashcards
what are catalysts?
- it is a substance which can alter or speed up a chemical reaction, without itself being chemically changed at the end of the reaction
describe how a catalyst helps the breakdown of potassium chlorate (VII).
- eg. potassium chlorate (VII) naturally breaks down into potassium chloride and oxygen gas
> very slowly and at a high temperature - when potassium chlorate (VII) is heated strongly in a test tube, oxygen in given off
> gentle heating only melts the potassium chlorate (VII) and no oxygen is produced - if a little Manganese(IV) oxide is added to the melted substance, reaction is speeded up and oxygen is rapidly given off
- Manganese(IV) oxide
> allows the reaction to be carried out at a lower temperature
> speeds up reaction
-at the end of the reaction, the same mass of Manganese(IV) oxide remains, not changing in the reaction
> it is an inorganic catalyst
> inorganic catalyst - are not destroyed by boiling or by changes in the pH of the solution
what are enzymes?
- proteins that function as biological catalysts
- they can alter or speed up chemical reactions
> they remain chemically unchanged at the end of the reaction
how does enzymes lower the activation energy? and its function in our bodies.
- enzymes provide an alternative pathway with lower activation energy required to start a chemical reaction
> lower the ‘height’ of the ‘hill’ (page73) - in our bodies, enzymes speed up the breakdown of glucose and fats to carbon dioxide and water at body temperature
> 37°C - no strong heat is required to start the reaction
what is an example of an enzyme catalyst process?
Digestion is an enzyme catalyst process
- some food molecules are large and insoluble in water
> these food molecules cannot diffuse through cell surface membrane
- large molecules must first be converted into simpler and smaller substances which are
> soluble in water and
> small enough to diffuse through cell surface membrane
- process is known as the digestion of food
> food digested by enzymes
eg.
-amylase: digests starch to maltose
- maltase: digests maltose to glucose
- protease: digests protein to amino acids
- lipase: digests fats to fatty acids and glycerol
What is activation energy?
It is the minimum amount of energy needed to start a chemical reaction
What can enzymes-catalyst reactions classified into?
- reactions that build up complex substances
>(Anabolic reactions) - reactions the break down complex substances substances
> catabolic reactions
What are anabolic reactions?
- the build up or synthesis of complex substances from simpler ones.
> eg. Amino acids taken into cells may be used to build up proteins
> cytoplasm contains special enzymes o catalyse such reactions
What are catabolic reactions?
- the breakdown of complex substances into simpler substances
- eg: pg 75
1. large molecule in food converted to smaller molecules by digestive enzymes
2. In cell respiration, glucose broken down
> release energy and form carbon dioxide and water > enzymes act together to completely break down glucose
3. Hydrogen peroxide is sometimes produced during chemical reaction in the cells
> substance toxic to cells
> plants and animals produce the enzyme catalase to break down hydrogen peroxide to water and oxygen
> removing the toxic effect
How are enzymes classified?
- classified according to the chemical reactions they catalyse
-enzymes that catalyse hydrolytic reactions are known as hydrolytic reactions
> hydrolases
Types of hydrolases: - carbohydrases ( digests carbohydrates)
- proteases ( digests proteins)
- lipases ( digests fats)
What are the characteristic of enzymes?
(Pg 77)
- speeds up chemical reactions
> alter rates of chemical reactions that occur in a cell
> speed up chemical reaction by lowering the activation energy needed to start the reaction - required in minute amounts
> enzymes are very efficient molecules
> remained unchanged in reactions so enzyme molecules can be used over and over again
> small amount of enzyme can catalyse a large number for chemical reactions - specific in action
> enzyme specificity: each chemical reaction inside a cell is catalyse by a unique enzyme
> is specific due to its 3-D shape
what are substrates?
the substances which enzymes act on
what are active sites?
- depressions or ‘pockets’ on the surface of an enzyme molecule which complimentary substrate molecules can fit
how is an enzyme substrate complex formed?
1.enzymes have as specific 3D shape
> have depressions called active sites
> substances that enzymes act on are substrates
- only the substrates with a 3D shape complementary to the active site can fit into the enzyme
> formation of: enzyme substrate complex - while the substrate is attached to the enzyme, a chemical reaction occurs
> substrate is converted into products - products leave the active site
& remains unchanged
what is the specificity of an enzyme due to?
- 3D shapes of the substrate and the enzyme being complimentary to each other
what is optimum temperature? and what is the optimum temperature of enzymes?
- every enzyme has an optimum temperature at which it is most active
- for most enzymes, 40-50°C or around 37°C
how are enzymes affected when the temperature is increased from low to high?
- enzymes have optimum temperature which it is most active
> 40-50°C - enzymes are inactive at low temps
> kinetic energy is low & chances of the substrate colliding with enzymes is low- increasing temp from low to optimum
> increases rate of enzyme reaction & higher temperature increases the kinetic energy of molecules
> higher chance of substrates fitting into active sites
- increasing temp from low to optimum
- increases the rate of formation of enzyme-substrate complex
- for every 10°C increase, the rate of enzyme reaction is doubled until the optimum temperature is reached
what happens to an enzyme when the temperature is increased above the optimum temperature?
- causes a rapid decrease in the rate of reaction
- enzymes are made of proteins
> high temps breaks the bonds that keep enzyme in shape - active site of the enzyme loses its original shape
> substrate molecule can no longer fit into the active site
( enzyme is denatured) - the higher the temp, the faster the rate of denaturation
- most enzymes completely denatured by 60°C
> enzyme lost its ability to catalyse
what is denaturation?
definition: its the change in the three-dimensional structure of an enzyme or any other soluble protein, caused by heat or chemicals such as acids and alkalis
-3D structure plays an impt role in its function
- denaturation results in the loss or alteration of the enzyme’s active site
> substrate can no longer fit into the enzyme’s active site
> no reaction will occur
> no longer act as a catalyst
how are enzymes affected by pH?
- affected by the acidity or alkalinity of the solutions in which they act
- some works best in acidic solutions and some works best in alkaline solutions
-extreme changes in the acidity or alkalinity of the solutions denature the enzyme
