enzymes Flashcards
what are enzymes
biological catalysts
globular proteins
Interact with substrate molecules causing them to interact
Without the need of harsh conditions
What are metabolic reactions
All the reactions that take place in an organism
What is a catalyst
A substrate rhat increases the rate of reaction bht doesn’t take part
Can be reused
What is the turnover
The number of substrate molecules that an enzyme molecule can catalyse per second
How do catalysts lower the activation energy
Provide an alternative pathway
Vmax
Enzymes can only increase the rate of the reaction up to a certain point
Max initial velocity rate of the enzyme Catalyzed reaction
3 types of enzymes
Catabolic
Anabolic
Modifying
GISELLE
Catabolic acid
Break substrates down into smaller products
Releases energy
Eg energy released from glucose release
Anabolic enezymss
Build up reactions
USE energy e.g. synthesis of polymer based components
Modifying
Changing the substrate slightly
Eg from alpha to beta glucose
Specificity of an enzyme
Many enzymes produced by living organisms
Each enzyme catalysed ONE biological reaction , of which there are 1000’s in any given cell
Active site shape is determined by the tertiary structure and is UNIQUE to each enzyme
Lock and key
When substrate is bound to the active site - enzyme substrate complex is formed
Substrates react and the product is formed = enzymes product complex
Products released and enzyme reused
Substrate held by the enzyme - atom groups are close enough to react , RA GROJPS WITBIN THE ACTIVE SITE of the enzyme will ALSO interact with the substrate, forming temporary bonds - these bonds put strain on bonds within substrate helping the reaction along t
Induced fit hypothesis
Enzyme changes shape slightly as the substrate enters
Initial interaction between the enzyme and substrate is weak - but these weak interactions rapidly induce changes in the enzymes tertiary structure that help strengthen binding - putting strain in substrate molecules
WEAKEN A PARTiCULAR bond in substrate - lowering the activation energy
Mechanism of enzyme action?
Molecule needs to collide in the right orientation
Enzymes help molecules collide successfully
INTRA acellular enzymes
Enzyme action takes place Ainsjfe Cells
Catalase ensures hydrogen peroxide is broke down into 02 and H2O quickly
EXTRA cellular organisms
Work outside th cell that makes them
For some organisms like fungi - work outside the body
Single celled organisms release enzymes into immediate environment
why are extracellular enzymes needed
Nutrients needed to supply subtrates to cells for product making for organisms , but these nutrients are often in te form of polymers and are too large so have to be broken down
How is starch digested
Broken down into maltose using amylase
Amylase produced by salivary glands and pancreas
Maltose broken down in small intestien into glucose by maltase
GLUCOSE - Absorbed by cells lining digestive system = blood stream
Digestion of protein ?
Trypsin breaks down proteins into smaller peptides , then brooken down into aminoacids
Trypsin produced in PANCREAS and released within pancreatic juices into small intestine - amino acids absorbed by cell lining digestive system
What factors affect enzyme activity ?
Temperature
pH
Enzyme and substrate concentration
how does increasing temperature affect enzyme activity
Increasing the temperature of a reaction environment increases KE of the particles
As temperature increases, particles move faster and collide more frequently e.g. enzyme and substrate
Higher reaction rate
What is temperature coefficient
Q10
Measure of how much the rate of reaction increases with a 10 degree rise in temp
Denaturarion w
After optimum temp is reached
Bonds holding protein vibrate - STRAIN AND BREAK
CHANGE IN tertiary structure , active site changes - irreversible and q10 no longer applies
Temperature extremes - hot
Thermophiles
Enzymes present in these .organisms are more stable than other enzymes
Higher number of bonds ( H bonds and sulphur bridges) in tertiary structure
Shape of thee enzymes and active sites are more resistant to change as temp rises
Cold temp
Extreme
More flexible structures
Less stable
Smaller temp changes denature them
How is the enzyme held
H bonds and ionic bonds between amino acid r grojps hold protein in precise 3D shape
BONDS RESULT from interaction polar and charged R groups present on AA forming primary structure
PH
Change in h+ concentration
How does pH affect enzymes
H+ interact with polar and charged R groups
Changing H+ ion concentration changes degree of interaction
Interaction of R groups with H+ also affects interaction of R groups with each other
More H+ ions = less R grojps are able to interact = bonds break REVERSE FOR LESS
PH buffer
Resists a change in pH
Mops up excess h+ ions
Eg haemoglobin in blood
Substrate and enzyme concentration
When the conc of substrate is increased the number of substrate molecules , atoms or ions in a particular area or volume increases
The increased number of substrate particles leads to a higher collision rate between susbraye and active site
More enzyme substrate complexes and EPCS formed
Renatursrion - pH
When pH changes from optimum
Enzyme and active site shape altered
HOWVEER if it returns to optimum protein will resume orgnila shape
Why do we need inhibitors
So reactions don’t happen too fast
Leads to build up of excess products
Ensure nto wastig products and substrates
What is an inhibitor
A molecule that prevents enzymes calaysing reactions
How do NON competitive inhibitions work
Inhibitor binds the enzyme at a location other than the active site ( allosteric)
The binding of the inhibitor causes the tertiary structure of the enzyme to change meaning the active site changes shape
ACITVE SITE AND SUBSTRATE NO LONGER COMPLEMENTARY
Some bind reversibly, others irreversible
how does increasing temperature affect enzyme activity
Increasing the temperature of a reaction environment increases KE of the particles
As temperature increases, particles move faster and collide more frequently e.g. enzyme and substrate
Higher reaction rate
What is temperature coefficient
Q10
Measure of how much the rate of reaction increases with a 10 degree rise in temp
Denaturarion w
After optimum temp is reached
Bonds holding protein vibrate - STRAIN AND BREAK
CHANGE IN tertiary structure , active site changes - irreversible and q10 no longer applies
Temperature extremes - hot
Thermophiles
Enzymes present in these .organisms are more stable than other enzymes
Higher number of bonds ( H bonds and sulphur bridges) in tertiary structure
Shape of thee enzymes and active sites are more resistant to change as temp rises
Cold temp
Extreme
More flexible structures
Less stable
Smaller temp changes denature them
How is the enzyme held
H bonds and ionic bonds between amino acid r grojps hold protein in precise 3D shape
BONDS RESULT from interaction polar and charged R groups present on AA forming primary structure
PH
Change in h+ concentration
How does pH affect enzymes
H+ interact with polar and charged R groups
Changing H+ ion concentration changes degree of interaction
Interaction of R groups with H+ also affects interaction of R groups with each other
More H+ ions = less R grojps are able to interact = bonds break REVERSE FOR LESS
PH buffer
Resists a change in pH
Mops up excess h+ ions
Eg haemoglobin in blood
Substrate and enzyme concentration
When the conc of substrate is increased the number of substrate molecules , atoms or ions in a particular area or volume increases
The increased number of substrate particles leads to a higher collision rate between susbraye and active site
More enzyme substrate complexes and EPCS formed
Renatursrion - pH
When pH changes from optimum
Enzyme and active site shape altered
HOWVEER if it returns to optimum protein will resume orgnila shape
Why do we need inhibitors
So reactions don’t happen too fast
Leads to build up of excess products
Ensure nto wastig products and substrates
What is an inhibitor
A molecule that prevents enzymes calaysing reactions
How do NON competitive inhibitions work
Inhibitor binds the enzyme at a location other than the active site ( allosteric)
The binding of the inhibitor causes the tertiary structure of the enzyme to change meaning the active site changes shape
ACITVE SITE AND SUBSTRATE NO LONGER COMPLEMENTARY
Some bind reversibly, others irreversible
examples of irreversible non competitive inhibitors
often very toxic
Organophosphate used as insecticides and herbicides inhibit the enzyme acetyl cholinestease - an enzyme necessary for nerve impulse transmission and can lead to muscle cramps and paralysis
non competitive inhibition - indegestion
protein pump inhibitors
long term indegestion
Irreversibly block an enzyme system responsible for secreting hydrogen ions into the stomach
This makes PPI’s effective in reducing the production of excess acid which if left untreated can lead to stomach ulcer formation
What is end product inhibition
Enzyme inhibition that occurs when the product of a reaction acts as an inhibitor go the enzyme that produces it
serves as NEGATIVE FEEBACK
Excess products are not made and resources not used
NON COMPETITIVE REVERSIBLE INHIBITION
example of end product inhibition - respiration
GLUCOSE BROKEN DOWN
- Addition of 2 phosphates to the glucose molecule
- Addition of the 2nd phosphate group , which results in the initial breakdown of the glucose molecule is catalysed by the enzyme PFK and this enzyme is COMPLETELY inhibited by ATP
when ATP is HIGH - more ATP binds to all obstetric site of PSK, prevents 2nd addition of 2nd phosphate group to glucose, glucose NOT broken down adn ATP not produced at the same rate
As ATP is used up- less binds to PSK - enzyme can catalyse the addition of 2nd phosphate group for glucose respiration resumes and more production of ATP
Competititive inhibition
Molecule of part of molecule has similar shape to the substrate of enzyme
Can fit into the active site of an enzyme
This blocks the substrate from entering the active site, preventing the enzyme from catalysing the reaction
The enzyme can’t carry out its function
Binds temporarily - effect is reversible ( FEW exception e.g. Aspirin)
What is the effect of non competitive inhibition on reaction rate , as your add more enzyme/ substrate
Increasing the conc of substrate/ enzyme has NO effect
This is because the substrates don’t compete with inhibitor for active site - so the non competitive inhibitor binds and the active site can no longer be used
Effect on reaction rate of competitive inhibitor
Substrate and inhibitor molecules present in solution will compete with each other to bind to active sites
This reduces number of substrate molecules binding to Clive sites in given time and reduce rate
Vmax can still be reached - when the eh substrate con centenarian is increases somuch that it overcomes inhibitor number by. A huge amount
Examples of competitive inhibitors
Statins are competitive inhibitors of an enzyme used in the synthesis of cholesterol
Help pooeple reduce blood cholesterol concentration
High bloo cholesterol = heart disease
Aspirin irreversibly inhibits the active site of COX enzymes, preventing the synth is of prostaglandins and thromboxane , the chemicals responsible for producing pain and fever
What are cofactors
Non protein helper
May form part of the active site or transfer atoms or routs from 1 reaction to another in multi steps pathways
WHAT are coenzymes
Organic molecule cofactors
Inorganic ion cofactors
- Presence of an ion is required for a fast reaction
- The ion makes the ESC form more readily
- Temporarily binds to the substrate of the enzyme
- Some cofactors act as cosubstrate , cofactors+ substrate = correct shape to bind to active site for the enzyme
- Some cofactors change the charge distribution on the surface of the sub rate molecule/surface of enzymes active site, making the temporarily bonds in the ESC form more readily
Example of inorganic ion cofactors
Making Amylase function properly (active site shape)
ONLY with CL- ions
Where can you get inorganic ion cofactors from
Via diet as minerals including iron, calcium, chloride and zinc ions
Prosthetic group cofactors
A COFACTOR that is permenantly bound - but by covalent bonds to an enzyme
PERMENANT
Example of pros ethic group COFACTOR
E.g. Zinc based pros ethic group in carbonic anhydrase, an enzyme CRUCIAL in the transport of co2 in the blood
Coenzyme
An organic non protein molecule that binds temporarily with substrate, to an enzyme active site - ESSENTIAL for enzyme acidity
Type of COFACTOR
Contain C
How do coenzymes work? - changed?
Chemically changed
During the reaction and they need to be recycled to this original state
-this may sometimes be a different enzyme
Coenzymes - examples
Vitamin b3 - used to synthesis and ( a coenzyme responsible for the transfer of H atom between molecules involved in reposition)
How can you get coenzymes
Derived from vitamins, a class of organic molecule found in the diet
Precursor activation ?
Many enzymes produced in an inactive form
Known as inactivate precursor enzymes, particularly enzymes that can cause damage within the cells producing them or to tissue where they are released , or enzymes whose action needs to be controlled and onlyactivated under certain conditions
How do precursor enzymes get activated - what happened to them
Undergo a change in shape ( tertiary )
Particularly to the active site
Achieved by addition of a COFACTOR
Precursor enzymes - before COFACTOR is added ?
APO enzyme
After COFACTOR is affecting ? (Precursor enzymes )
Halo enzyme
What are zymogens and pro enzymes
Precursor enzyme that are activated by….
- A change in tertiary structure by the action of another enzyme( e.g. Protease which cleaves certain bonds in the molecule)
- A change in condition such as pH or temp results in a change in tertiary structure and activated in a precursor enzyme
