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CHAPTER 5: ENZYMES (Biological Catalyst (Function: Speed up reactions - as…
CHAPTER 5: ENZYMES
Biological Catalyst
Function: Speed up reactions - as catalyst
Speed up
= INCREASE the rate of reaction
Catalyst NOT being used up in the progress
End product: substrates + enzymes
NOT needed in metabolic reactions
Called as enzymes - biological
Without enzymes: reaction very slow/impossible
NOT all enzymes breakdown substances
Starch phosphorylase: build starch molecules from glucose molecules
Examples of enzymes
Animal cells
Amylase: starch :arrow_right: sugar maltose
Lipase: lipids :arrow_right: fatty acids
Protease: protein :arrow_right: amino acids
Catalase: hydrogen peroxide :arrow_right: water + oxygen (in liver cells)
Plant cells
Amylase: starch :arrow_right: maltose (during germination - activated when seed absorbed water)
Catalase: hydrogen peroxide :arrow_right: water + oxygen (in potato cells)
Starch phosphorylase: glucose molecules :arrow_right: starch molecules
Naming Enzymes
According to
general reaction
catalysed
Carbohydrases
: break down carbohydrates
Proteases
: break down proteins
Lipases
: break down lipids (fats)
According to
specific reaction
catalysed
Amylase
: break down starch
Maltase
: break down maltose
Sucrase
: break down sucrose
The
Lock and Key Mechanism
Getting that 'perfect fit' - like lock and key
Shape of enzyme (active site)
fits
the shape of part of the enzymes and substance
The
Active Site
Terms
Substrate
: substance present at the beginning of a reaction
Product
: substance made by reaction
Example of Reaction: Saliva
Saliva: contains amylase - break down starch into complex sugar maltose
:red_flag:
Mechanism:
Amylase has dent called as active site
Starch molecule has shape that complement the active site of amylase
By collision theory, once starch molecule fits into the amylase's active site, enzyme will breaks the starch molecule apart.
End products of starch molecule will leave the amylase enzyme
Amylase enzyme free to bind other starch molecules
Properties of Enzymes
Effects of Temperature on Enzyme
Low temperature
Enzyme and substrate moving (very) slowly - low energy (less likely to collide with right amount of energy for reaction)
Rate of reaction: low
Increasing temperature
Enzyme and substrate moving faster - higher energy (more collisions with appropriate amount of energy for reaction)
Rate of reaction: high (increased)
Having more energy for reaction to take place
Optimum temperature
Most suitable temperature for reaction to take place - maximum temperature
In
human body
: 37 C (mostly)
Temperature where reaction peaks
High temperature
Exceeding maximum temperature for enzyme to work - reaction slows down
Enzyme denatured - enzyme's active site lose shape (substrate no longer fits active site)
At
60 C
: enzyme denatured completely - reaction stops
In
every 10 C temperature rise
,
rate of enzymatic reaction doubled
(until optimum temperature reached)
Example of enzymes around us
Human enzyme: 37 C to 40 C
Plants: 28 C to 30 C
Bacteria living in hot springs (thermophiles): 70 C onwards (depending to their respective habitat temperature)
Effects of pH on Enzyme
Introduction
Enzymes work in neutral pH (pH 7)
Too acidic or alkaline: enzyme denatured - active site no longer fit)
pH: measurement of acidity or alkalinity of a solution
How does pH alters the efficiency of the enzyme?
Charge in pH alters active sites - decrease ability of substrate - enzyme binding
Low pH value: excess hydrogen ions bind to active sites - altering ionic charges
Defects (from pH alteration): reversible (normally)
Example of enzyme + pH
Pepsin [a type of protease] in stomach: pH 2 (hydrochloric acid)
Amylase in mouth & duodenum: pH 7 (neutral)
Trypsin in duodenum: pH 8.5 (bile)
Effects of substrate concentration on enzyme
Low substrate concentration, high enzyme concentration
Reaction will increase exponetially
Higher collision rate between enzymes & substrate :arrow_right: more substrate catalysed per unit time :arrow_right: higher product formed per unit time
Condition: Concentration of enzyme > concentration of substrate
Limiting factor: substrate
High substrate concentration, low enzyme concentration
Excess substrate will compete for enzymes
Reaction will increase exponentially until maximum reaction rate is reached (all active sites are engaged) and become constant
Condition: Concentration of enzyme < concentration of substrate
Limiting factor: enzyme
Effect of enzyme concentration on substrate
Low enzyme concentration, high substrate concentration
Reaction rate is same as in 'High substrate concentration, low enzyme concentration'
Doubled the enzyme concentration :arrow_right: rate of reaction doubled = number of substrate convert to products per unit time doubled
Condition: concentration of substrate > concentration of enzyme
Limiting factor: enzyme
High enzyme concentration, low substrate concentration
Reaction rate is same as in 'Low substrate concentration, high enzyme concentration'
Limiting factor: substrate
Condition: concentration of substrate < concentration of enzyme
Enzymes in Industries
Laundry
e.g.: biological washing powders
Greasy stains
Able to wash off by detergent - dissolving grease in water
Non-greasy stains
(blood stains, egg yolk, etc)
Protein stuck in clothes' fibre (unable to be washed)
Enzyme in biological washing powder - break down molecules
Example: Egg yolk stain on cotton cloth
Enzyme trypsin breaks down coloured protein molecules of the egg yolk.
Bigger molecules of coloured protein (insoluble in water) :arrow_right: non-coloured smaller molecules of amino acid (soluble in water)
Amino acids dissolve in water and washed away.
Example of enzyme in biological washing powder:
Trypsin (protein)
Lipase (grease)
Food & Beverage
(food manufacturers)
Pectinase
(in apple juice production)
Pectinase: enzyme that breaks down substance (pectin) that holds apple cells together (which make produced apple juice cloudy)
Effect of pectinase:
more juice produced
turning apple juice from cloudy to clear (prefered by majority)
Lactase
(in milk production)
Lactase: breaks down lactose (intolerable by some) into glucose and galactose (both to be tolerable by all).
Lactase-added milk: called as lactose-reduced milk
safer for people with lactose intolerance
People with lactose intolerance: lacking of lactase in digestive tract
Amylase & Protease
(in brewing)
Example of
enzymes used in brewing
:
Proteases
Amylases: α-amylases, β-amylases
Glucanases: β-glucanases,
Barley (cereals) malt kernels contains:
starch :arrow_right: enzyme amylase
protein :arrow_right: enzyme protease
glucans (a type of polysaccharide - cellulose) :arrow_right: enzyme glucanase
pentosans (a type of polysaccharide) :arrow_right: enzyme pentosanase/xylanase
Using Microorganisms for Enzymes
Positive attributes
easy to manipulate: microbes grown and controlled in a fermenter
culture specific type of microbe to get a certain type of enzymes (produced as metabolic by-product)
Negative attributes
requires frequent supervision (avoiding drastic drop in environmental factors: temperature, pH, etc)
requires high-end purification to harvest usable products
Example:
Penicilin antibiotic
produced by fungi,
Penicillium
able to kill bacteria but not our human cells