Density of an Irregular Solid - Rochford...
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Enzymes
Miss Rochford
Fifth Year Biology
In this topic:
• Sources of Energy
• What are enzymes?
• Enzyme functions and shape
• Role of enzymes in plants and animals
• Effects of pH & temp. on enzyme activity
• Bio-processing
Sources of Energy
Solar Energy
Cellular energy
• Primary source of energy for life on Earth
• Used for photosynthesis
• Energy stored in the bonds of biomolecules (carbohydrates or lipids)
• Used for respiration • Can pass along a food chain
Metabolism
Metabolism: the sum of all of the chemical reactions in an organism
• Enzymes are the driving force of metabolism
• Without enzymes, life would not exist
E
Enzyme: a biological catalyst. It speeds up chemical reactions without being used up or changed
Amylase
Starch molecule Maltose molecules
Enzymes
E
Enzyme: a biological catalyst. It speeds up chemical reactions without being used up or changed
Enzymes
• All enzymes are made of protein
• Most enzymes are globular proteins
• They are folded and have a 3D shape
Enzymes
• Enzymes only work on one type of reaction each
E Product: substance produced as a result of the action of an enzyme
E Substrate: substance enzyme acts on
Starch amylase Maltose
Substrate Enzyme Product
Metabolism Remember:
Anabolism USES energy to build larger
molecules from smaller molecules
Catabolism RELEASES energy by breaking large
molecules into smaller pieces
Catabolic Enzymes
Examples:
Catabolic enzymes: break large molecules into smaller pieces and release energy
Amylase
• Breaks starch into maltose
• Produced by saliva glands and the pancreas
Anabolic Enzymes
Examples:
Anabolic enzymes: use energy to build large molecules from smaller molecules
DNA Polymerase
• Forms and repairs DNA
• Found in almost all living things
Reversibility
• Enzyme reactions are reversible
– They can go in either direction
Active Site and Specificity
• Active sites are ‘specific’ – They will only accept one
substrate or set of substrates
Enzyme active site: where the substrate enters and is changed into a product(s)
Specificity: an enzymes ability to react with only one substrate
Theories of Enzyme Action
Lock and Key Model
Lock and Key Model
• 1894: Emil Fischer
• The theory:
– Enzymes have a rigid shape
– Substrate(s) fits into the active site of the enzyme
(like a key in a lock)
Induced Fit Model
Induced Fit Model
• 1958: Daniel Koshland Jr.
• Favoured by biologists
• The Theory:
– The active site is flexible
– The substrate ‘induces’ the active site to change into the correct shape
Enzyme Inhibitors
• Inhibitors attach to enzymes and destroy their shape
• This is known as denaturing
Nerve Gases
• Some nerve gases are inhibitors that attach to enzymes involved in our nerve transmissions (e.g. Sarin gas)
Cyanide
• Cyanide denatures an enzyme involved in respiration
Beneficial Enzyme Inhibitors
Inhibit nerve transmission enzymes in insects to kill them
Insecticide
Inhibit nerve transmission enzymes to prevent us from feeling pain
Painkillers
Affect bacterial enzyme action causing them to die Antibiotics
Leaving Cert Syllabus
You need to know two environmental conditions that affect enzyme action:
1. pH
2. Temperature
Effect of pH on enzyme activity
pH scale: an indication of how acidic or basic a substance is. It runs from 0 to 14.
Effect of pH on enzyme activity
• All enzymes have a pH at which they work best (optimum pH)
• A slight pH change can have a big effect on an enzyme’s activity
• Most enzymes work best at pH 6 – 8
• Stomach enzymes work best at low pH
Activity 8: To investigate the effect of pH on the rate of catalase activity
(Pg. 65)
Step 1
• Finely chop the celery.
• Weigh 5 g of the chopped celery.
Step 2
Add into a graduated cylinder:
• 20 ml buffer pH 4
• 1 drop wash-up liquid
• 5 g celery
Step 3
Add 2 ml of hydrogen peroxide to a boiling
tube.
Step 4
Put the graduated cylinder and the boiling tube in a
water bath at 25 °C.
Step 5
• Pour the hydrogen peroxide into the graduated cylinder
• record the volume immediately.
Step 6
• Time for 2 minutes
• Record the final volume.
Step 7
Repeat the steps for
different pH buffer solutions
e.g. 6, 7, 9, 10
Table of results:
pH of buffer
Initial volume (ml)
Final volume (ml)
Volume of foam produced
(ml)
Expected Graph
Effect of temperature on enzyme activity
• Why do we keep food in a fridge?
• Lower temp = slower enzyme activity
• Higher temp = faster enzyme activity
• This is to do with the speed of molecular movement
Effect of temperature on enzyme activity
Low Temperature Slows enzyme activity
Higher Temp. Speeds up enzyme activity
Too high a temp. Stops enzyme activity by changing
its shape (denaturing)
Effect of temperature on enzyme activity
Effect of temperature on enzyme activity
Optimum temperature
Human enzymes 37 °C (body temp)
Plant enzymes 20 - 30 °C
Activity 9: To investigate the effect of temperature on the rate of catalase activity
(Pg. 71)
Step 1
• Finely chop the celery.
• Weigh 5 g of the chopped celery.
Step 2
Add into a graduated cylinder:
• 20 ml buffer pH 9
• 1 drop wash-up liquid
• 5 g celery
Step 3
Add 2 ml of hydrogen peroxide to a boiling
tube.
Step 4
• Put the graduated cylinder and the boiling tube in an ice bath.
• Leave until they reach 4 °C
Step 5
• Pour the hydrogen peroxide into the graduated cylinder
• record the volume immediately.
Step 6
• Time for 2 minutes
• Record the final volume.
Step 7
Repeat the steps for
water baths at different
temperatures
e.g. 20°C, 30°C, 45°C, 60°C,
Table of results
Temperature (°C)
Initial volume (ml)
Final volume (ml)
Volume of foam produced (ml)
Expected Graph
Denaturation
How enzymes are denatured:
• High temperatures
• pH values outside the enzyme’s optimum
• Some chemicals
• Radiation
Denatured enzyme: an enzyme that has lost its shape and no longer functions properly
Activity 11: To investigate the effect of heat denaturation on catalase activity
(Pg. 82)
Step 1
• 5 g chopped celery into two boiling tubes
• Water baths at 100°C and 20°C for 10 minutes.
• Remove and cool.
Step 2
Add 20 ml of buffer pH 9 to two graduated
cylinders.
Step 3
Add one drop of washing up liquid to each graduated
cylinder.
Step 4
• Add the 5 g of boiled celery to one cylinder and label ‘A’.
• Add the 5 g of un-boiled celery to the other cylinder and label ‘B’.
Step 5
• Add 2 ml of hydrogen peroxide to two new boiling tubes.
• Place both tubes in the water bath at 25 °C
Step 6
Stand cylinders and boiling tubes
into the water bath until the
desired temperature is
reached.
Step 7
Add the hydrogen peroxide from each boiling tube to the
corresponding graduated cylinder.
Expected result:
Note the presence or absence of foam in each graduated
cylinder.
Table of results
Boiled
enzyme
Un-Boiled
enzyme
Foam present
or absent
Immobilised Enzymes
Immobilised Enzymes
Bioprocessing: The use of enzyme-controlled reactions to produce a product
Bioreactor: a vessel or container in which living cells or their products are used to make a product
Bioprocessing
Traditional Bioprocessing
• Used microorganisms (yeast and bacteria) to produce foodstuffs
Cheese Yoghurt Bread Wine & Beers
Modern Bioprocessing
• Uses purified enzymes
• Produces a vast range of products:
Antibiotics
Vaccines
Food colouring & flavours
Vitamins Enzymes
Perfume
Immobilised Enzymes
• Using freely dissolved enzymes is very wasteful
• They get removed at the end
• Immobilising means they can be used again
Immobilised Enzymes
Immobilised enzymes: enzymes attached to or trapped in an inert insoluble material
Physical Methods
Immobilised Enzymes
Immobilised enzymes: enzymes attached to or trapped in an inert insoluble material
Chemical Methods
Immobilising Techniques
Adsorption • Enzymes physically attached to inactive
supports • E.g.: glass beads, ceramics, cellulose
particles, polymers
Enclosed in a gel
• Gel used: sodium alginate comes from algae Holds enzyme in place Permeable to entry of substrate & exit of products
Advantages of Immobilised Enzymes
• Can be reused
• Cheaper process
• Product doesn’t need to be separated from enzymes
• Increased stability of the enzyme
Use of Immobilised Enzymes
• Expensive sweetener • Use glucose isomerase to convert
cheaper glucose to fructose
Fructose production
• Expensive enzyme that alters penicillin in antibiotic research
• Cheaper to use when immobilised
Penicillin acylase
• Expensive enzyme • Converts lactose to glucose & galactose • Used in soft toffee and caramel
Lactase
Activity 10: To prepare an enzyme immobilisation and examine its application
(Pg. 76)
Step 1
In a beaker:
• 10 ml distilled water
• add 0.4 g sodium alginate
• stir.
Step 2
Separate beaker:
• add 2 g of yeast to 10 ml of distilled water
• Stir
Step 3
Separate large beaker:
• dissolve the calcium chloride in water
Step 4
Add:
• yeast suspension
• to the alginate solution
Step 5
Draw the mixture into a 20 ml
syringe.
Step 6
Height of 10 cm:
• Drop from the syringe into the calcium chloride
• Only one drop at a time.
• Leave to harden for 10 minutes.
Step 7
• Filter the hardened beads through a sieve
• Rinse with water.
Step 8
• Mix 2 g of yeast in 10 ml of distilled water
• Pour into one of the separating funnels
Step 9
Pour the beads into the second funnel.
Step 10
Separate Beaker
• Dissolve 1 g of sucrose in 100 ml of distilled water.
• Pour 50 ml into each separating funnel.
Step 11
Immediately test the
products in the beakers with
glucose strips.
Step 12
Repeat glucose strip test every 2
minutes until glucose
appears in both beakers.
Step 13
• Empty each funnel into the beakers
• Compare the turbidity
Table of results Time
(minutes)
Free yeast –
presence of glucose
Immobilised yeast –
presence of glucose
0
2
4
6
8
10
Free yeast Immobilised yeast
Turbidity of solution
Energy Carriers
ATP
• Found in all organisms
• Most important energy carrier
• Directly supplies energy for metabolism
ATP = Adenosine triphosphate
ATP
• Made of:
Adenine base (also found in DNA)
Ribose: a 5-carbon sugar
3 phosphates
ATP and ADP
• This is an anabolic reaction
• Energy in ATP is stored in the 3rd phosphate bond
ADP = Adenosine diphosphate
Releasing energy from ATP
• When the 3rd phosphate bond is broken:
Energy is released
ADP is formed again
A phosphate is released
Where does this all happen?
Mitochondria Cells
ATP
ADP P
Energy
water
Oxidation and Reduction
Oxidation
Is
Loss of electrons
Reduction
Is
Gaining electrons
OIL RIG
NAD+ and NADP+
• Electrons and protons are really important parts of respiration and photosynthesis
• Protons are represented as H+
NAD+ and NADP+
• When electrons gain energy, H+ are released
• H+ are too unstable to exist on their own
– They get transferred by the energy carrier molecules
NAD+ NADP+
Respiration energy carrier
Photosynthesis energy carrier
NAD+ and NADP+
NAD+ Nicotinamide adenine dinucleotide
NADP+ Nicotinamide adenine dinucleotide
phosphate
NAD+ and NADP+
• Each energy carrier can gain an electron (e-) by reduction
NAD+
NADP+
e-
e-
NAD
NADP
NAD+ and NADP+
• They gain another electron (e-) by reduction
NAD
NADP
e-
e-
NAD-
NADP-
NAD+ and NADP+
• They then attract a Hydrogen Ion (H+) because of their negative charge
NAD-
NADP-
H+
H+
NADH
NADPH
In summary:
In photosynthesis:
In respiration:
To release energy for anabolic reactions:
In respiration:
In photosynthesis:
Chapter 9: Enzymes
DONE!!