CH4 enzymes Flashcards
Why are enzymes important
As most of the processes needed for life involve chemical reactions and the conditions required for a fast reaction are not possible in living cells
What are enzymes
Biological catalysts and globular proteins that interact with substrate molecules and cause to react
What is an anabolic reaction
Chemical reaction required for growth
What is a catabolic reaction
Breakdown reaction
What is the vmax
The maximum point at which the rate of reaction can be increased to
What is needed for particles to react
Collision in correct orientation and to have at least the activation energy
What is specificty
An enzyme will only catalyse one specific reaction
Lock and Key hypothesis
- substrate binds to active site forming an enzyme substrate complex
- substrates react forming an enzyme product complex
- products leave enzyme
- substrate held in way that right atom groups are able to interact
- r groups in the active site interact with substrate, forming temporary bonds which puts strain on bonds in substrate
Induced-fit hypothesis
- initial interaction of enzyme and substrate is relatively weak
- weak interactions rapidly induce changes in enzymes tertiary structure that strengthen binding, putting strain on substrate molecule
- weakens bonds, lowering activation energy
Catalase
- intracellular enzyme
- involved in breakdown of hydrogen peroxide into oxygen and water
How do single celled organisms use extracellular enzymes
- release enzymes into immediate environment
- enzymes break down large molecules to small molecules
- absorbed by cells
Digestion of starch
Salivary glands and pancreas- starch (amylase) maltose
Small intestine - maltose (maltase) glucose
Digestion of proteins
Pancreas - proteins (trypsin) smaller peptides and amino acids
What is the initial effect of temperature
- increasing temperature increases reaction rate as collide more frequently
- temperature coefficient says for every 10 degree increase, rate doubles (q10)
What happens if temperature gets too high
- bonds holding protein together vibrate which places strain on them and causes to break
- changes proteins tertiary structure and enzyme is denatured so enzyme can no longer bind to substrate
How are some organisms able to cope with temperature extremes
Cold - have more flexible structures
Hot - have more stable structures due to increased hydrogen bonds and sulfur bridges
What holds proteins in their precise 3d shapes
Hydrogen bonds and ionic bonds between amino acid r groups which result from interactions of polar and charged r groups in primary structure
What does a change in ph refer to
A change in concentration of hydrogen ions
What happens when ph decreases
- more hydrogen ions present
- r groups are less able to interact with eachother
- bonds break and shape of enzyme changes
What happens when substrate concentration is increased
- higher collision rate with active sites
- at v-max, all active sites are occupied and no more enzyme-substrate complexes can form
Why is enzyme inhibition important
Ensures excess amounts of product not formed
How does a competitive inhibitor work
- molecule with similar shape to substrate fits into active site
- substrate cannot enter active site and enzyme cannot function
How does a competitive inhibitor affect reaction rate
Reduces rate of reaction but does not change vmax
Example of competitive inhibition
- statins
- inhibits enzyme used in synthesis of cholesterol
How do non-competitive inhibitors work
- inhibitor binds to enzyme at allosteric site
- binding of inhibitor causes tertiary structure to change and enzyme changes shape
- active site no longer complementary
Effect of non competitive inhibitor on rate reaction
Decreases rate of reaction and vmax
What is end product inhibition
When product of a reaction acts as an inhibitor for the enzyme that produces it
Example of end-point inhibition
- first step of breakdown of glucose involves addition of two phosphate groups
- addition of second is catalysed by PFK which is competitively inhibited by atp
- high levels of atp means more atp binds to allosteric site of pfk so glucose not broken down and vice versa
What is a cofactor
- inorganic
- obtained via minerals
What is a coenzyme
- organic
- derived from vitamins
What is a prosthetic group in an enzyme
- cofactor
- permanent
- example: zinc 2+ is part of carbonic anhydrase
What is precursor activation
- activation of enzymes as may cause harm to cells where produced
- achieved by addition of a cofactor
- apoenzyme to holoenzyme
What is a proenzyme
- enzymes that change shape in certain phs or temperatures
- another form of precursor activation
