Enzymes

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Give an example of a intracellular enzyme.
DNA polymerase
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What is the function of catalase?
To break down hydrogen peroxide- a biproduct of many biochemical reactions into oxygen and water
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Where is catalase found?
In vesicles called peroxisomes in eukaryotic cells, in WBC to kill pathogens
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What is catalase made up of?
4 polypeptide chains and a haem group.
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How does an enzyme form an enzyme-substrate complex?
Inside the active site there are a few amino acids with reactive R groups and these are able to form temporary bonds with part of the substrate molecule
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Why is the induced-fit hypothesis now the theory which is most widely accepted?
Because when the active site changes shape slightly this puts strain on the bonds in the substrate, allowing them to be broken more easily (requiring less energy)
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What is an anabolic reaction? What do they require?
A reaction of metabolism which constructs molecules from smaller units. These reactions require energy from the hydrolysis of ATP.
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Define metabolism
Sum of all the different reactions and pathways happening in a cell/ in an organism
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What is Vmax?
The maximum rate of initial reaction
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How many amino acids usually make up the active site?
about 6-10
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What happens if an enzyme catalysing a metabolic reaction is deficient?
A metabolic disorder occurs e.g. Galactosemia: Impaired breakdown of the sugar galactose leads to jaundice, vomiting, and liver enlargement after breast or formula feeding by a newborn.
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What is stone man disease?
Rare connective tissue disease caused by a mutation of the body's repair mechanism, which causes fibrous tissue (including muscle, tendon, and ligament) to be ossified spontaneously or when damaged injuries can mean joints are permanently frozen.
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What is the turnover number of catalase
6 million per second
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How does the optimimum pH for catalase vary?
In humans it is around pH 7 but in other species it varies between 4-11
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How does the optimum temperature for catalase vary?
In humans it is 45 degrees, but in some thermophilic archea it is 90 degrees
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What is a reason why some people go grey earlier in life?
They have lowered levels of catalase and so more hydrogen peroxide bleaches their hair shafts from the inside
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Give an example of an extracellular enzyme which works OUTSIDE the BODY.
Bread mould, mucor (a fungi) releases hydrolytic enzymes from thread-like hyphae
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Which two enzymes are involoved in starch digestion?
amylase and maltase
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Where do bacteria and yeasts release their extracellular enzymes to?
their immediate environment
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What are the two enzymes involved in protein digestion?
Pepsin and trypsin
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Why does being held in an active site make two substrate molecules more likely to bind?
The right atom groups are held close enough to react
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List the non-covalent forces which bind a substrate molcecule to an active site.
H bonds, ionic attractions, Van der Waals forces, Hydrophobic interactions
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What is a synomym for hydrolysis?
Digestion
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What is the temperature coefficient Q10?
A measure of how much the rate of reaction changes when the temperature is increased by 10 degrees
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What is the Q10 for enzymes below their optimum temperature?
2- i.e for every 10 degree rise in temperature the rate of reaction doubles
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What are psychrophilic organsims? What would be their optimum temperature?
Bacteria which live in very cols environments e.g. deep oceans, high altitudes and polar regions. Their optimum temperature is around 5 degrees
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What happens when the temperature goes above the optimum level?
Vibrations break some of the weak bonds e.g. H bonds and ionic bonds which hold the tertiary structure of the active site meaning it will no longer be complementary.
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What part of an enzyme isn't affected by increased temperature?
The enzymes primary strucutre because heat does not break the peptide binds between amino acids
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Give two examples of organic acids
Lactic acid and pyruvic acid
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How is pH calculated?
1/concentration of hydrogen ions
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Why can normal rate of reaction be restored if there were only minor changes to pH
H bonds can reform and so the active sites shape can be reformed
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what is the optimum pH of pepsin?
1-2
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Why does rate of reaction decrease over time?
Because over the course of a reaction substrate concenration is decreased as more of it is converted to product molecules
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What are the advantages of constant enzyme synthesis and degredation?
Elimination of abnormally-shaped proteins that may accumulate and harm the cell/ Regulation of metabolism by eliminating any surplus enzymes
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How long does a haemoglobin molecule 'live' for?
120 days
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What shape do competitive inhibitors have?
A SIMILAR shape to the subsrate
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What is an irreversible competitive inhibitor called?
An inactivator
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What is a prosthetic group?
A co-factor which binds permanently to the enzyme
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What co-factor does the enzyme carbonic anhydrase require?
A zinc ion.
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In what way can co-factors act?
As co-substrates which bind to the substrate making it the correct shape to fit into the active site. Alter charges-on surface of substrate/AS making temp bonds enable ESC to form more easily.
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What is pellagra caused by?
A lack of vitamin B3 (nicotinamide) which is needed for the enzyme pyruvate dehydrogenase to work during respiration.
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What are chloride ions needed for?
for amylase to digest starch into maltose
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Why do coenzymes need to be continually recycled?
Because they are chemically changed in the reaction
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What is a coenzyme?
An organic cofactor
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What is vitamin B5 used for?
To make Coenzyme A which is essential in the breakdown of fatty acids and carbohydrates in respiration
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What are the symptoms of pellagra?
Described as the 4D's diarthoea, dermatitis, dementia and death
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What is an apoenzyme?
What a precursor protein is called before the cofactor is added
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What is the enzyme known as once the cofactor has been added?
A holoenzyme
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How has zinc deficiency been combatted in East Africa?
Through the implementation of genetically-modified plantain a staple crop in areas where meat is often too expensive.
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How are body tissues protected from being digested themselves?
It is only when the inactive pepsinogen is released into the acidic conditions of the stomach that it becomes the active pepsin enzyme. The change in pH changes pepsinogen's tertiary structure
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What type of enzyme is thrombin and what reaction does it catalyse?
A protease which catalyses the conversion of soulble fibrinogen into insoluble fibrin
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What process does potassium cyanide inhibit and how?
Inhibits aerobic respiration and catalase. when injested it is hygrolysed producing hydrogen cyanide gas- readily dissociates- the CN- ions bind irreversibly to enzyme found in mitochndria- inhibiting final stage of respiration.
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What happens if snake venom enters the body?
inhibits action of acetylcholinsterase- important for neuromuscular synapses-break down Ach. If inhibited Ach stays attached and muscle remain contracted leading to paralysis and suffcoation
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How does aspirin work?
binds and inhibits enzymes responsible for producing prostaglandins- cell signalling molecules which make nerve cells more sensitive to pain and increase swelling
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Where do we get ATPase inhibitors from?
Extracted from foxglove leaves. The compunds have now been identified as cardiac glycosides/digitalis/digitoxin
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What are ATPase inhibitors used to treat and how do they work
used to treat heart failure & atrial arryhtmia. Inhibits Na/K pump in heart muscle cells allowing more Ca2+ ions to enter inc. muscle contraction=stronger heartbeat
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Which type of drugs can prevent viral infections, how do they work?
Protease inhibitors- they prevent replication of virus particles within host cells by inhibiting protease enzymes so that viral coats can't be made
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What types of drugs are used to treat HIV positive patients?
Nucleoside reverse transcriptase inhibitors e.g. Zidovudine and abacavir. They inhibit enzymes involved in making DNA using viral RNA as a template.
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What is the purpose of ACE inhibitors?
To lower the blood pressure of patients with hypertension who cant take beta-blockers
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What does ACE stand for?
angiotensin converting enzyme
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Other cards in this set

Card 2

Front

What is the function of catalase?

Back

To break down hydrogen peroxide- a biproduct of many biochemical reactions into oxygen and water

Card 3

Front

Where is catalase found?

Back

Preview of the front of card 3

Card 4

Front

What is catalase made up of?

Back

Preview of the front of card 4

Card 5

Front

How does an enzyme form an enzyme-substrate complex?

Back

Preview of the front of card 5
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