Unit 2 - Enzymes Flashcards Preview

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Flashcards in Unit 2 - Enzymes Deck (35)
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1
Q

What does a substrate need to have in order to bind with an active site

A

Complementary shape

Opposite charges to the active site

2
Q

How does change in pH alter the rate of the reaction

A

Electric charges of both the enzyme and substrate are neutralised by the presence of either positive or negative ions so no enzyme-substrate complex is formed

3
Q

Allosteric enzyme regulation

A

An inhibitor can bind to the allosteric site and usually inhibits the activity
However Cyclic AMP can bind to the inhibitor and remove it so the enzyme can be active again

4
Q

Competitive inhibition

A

Competitive inhibitors compete with the substrate to bind with the active site
Has sim shape to part of/all of substrate
A competitive inhibitor occupies the active site only temporarily and so the reaction is reversible
Doe not change Vmax

5
Q

Non-competitive inhibition

A

Non competitive inhibitors binds with the enzyme at allosteric site. Inactivates the enzyme by altering shape (changes 3’ structure)
Can be irreversible

6
Q

Why are heavy metals (e.g. lead and arsenic) poisonous

A

They have such strong affinities for - SH (sulfhydryl) groups and destroy catalytic activity

7
Q

How is enzyme inhibition exploited to control disease

A

Penicillin and other drugs inhibit enzymes that certain diseases use in order to survive

8
Q

2 types of enzymes

A

Intracellular (catalase, converts H2O2 into O2 and H2O)

Extracellular (digestive enzymes)

9
Q

Properties of enzymes

A

Complementary active site to shape of substrate
High turnover no.
Ability to reduce activation energy
Left unchanged after reaction

10
Q

What are enzymes affected by

A

Temperature
pH
Enzyme conc.
Substrate conc.

11
Q

Lock and key hypothesis

A

Shape of active site caused by sequence of amino acids (specific tertiary structure - 3D)

12
Q

Induced fit hypothesis

A

Explains how activation energy is reduced
Active site is not perfectly complementary but when substrate moves into active site, interferes with the bonds holding active site together
Induces changes in 3’ structure to strengthen binding and weaken bonds in substrate
Active site alters to give perfect fit. Changed shape of active site —> bonds in substrate easier to make or break (reduces activation energy)

13
Q

Enzyme controlled reaction

A

Enzyme + substrate (E + S) —> enzyme substrate complex (ESC) —> enzyme product complex (EPC) —> Enzyme and product (E + P)

14
Q

Effects of pH on enzymes

A

Enzymes fully denatures before pH 3 and after pH 11
Enzymes start to denature after pH 7
Hydrogen ions that cause acidity affect interaction between polar and charged R groups and alter tertiary structure

15
Q

Co-enzymes

A

Small, organic, non protein molecules that bind to active site for short time
Take part in reaction and is recycled
Can carry chemical groups

16
Q

Example of co-enzymes

A

FAD
NAD
Co-enzyme A
Vitamin B3 - helps break down carbs and fat

17
Q

Prosthetic groups

A

Co-enzyme that is a permanent part of an enzyme molecule (inorganic ion)
Found in conjugated protein molecules e.g. haemoglobin (Fe^2+)
Contribute to final 3D shape and charge

18
Q

Example of prosthetic groups

A

Carbonic anhydrase contains a zinc based prosthetic group, helps catalyse CO2 and H2O to make carbonic acids (found in rbc)

19
Q

Co-factors

A

Presence of certain ions increase reaction rate
Ions combined with an enzyme or substrate
Binding helps form an ESC more easily, affects shape and charge
e.g. Cl- helps form active site to amylase

20
Q

How are hydrogen bonds formed

A

The slight -ve charge on the oxygen atom attracts the slight +ve charge on a hydrogen atom forming a strong bond

21
Q

Which enzyme group can catalyse oxidation reactions

A

Dehydrogenases

22
Q

What is the approximate temperature coefficient (Q10) of an enzyme controlled reaction

A

2
The rate of reaction typically doubles w/ a 10 degrees C increase
Does not apply to denatured enzymes

23
Q

Which enzyme catalyses the breakdown of triglycerides into glycerol and 3 fatty acids

A

Hydrolase

24
Q

Which type of enzyme catalysed the conversion of a dipeptide into two separate amino acids

A

Hydrolase

25
Q

End product inhibition

A

Where the product made stops the enzyme from making further products and binding to more substrates

26
Q

Measuring the rate of an enzyme-controlled reaction

A

Measure how fast the product appears and use this for comparison
Catalase catalyses H2O2 –> H2 + O2

27
Q

Variables for reaction of breakdown of H2O2

A

IV -Temp (use water baths)
DV - vol of O2. produced
CV - pH (use same type of buffer), vol and conc of H2O2 and catalase (from celery)

28
Q

Precursors (apoenzymes)

A

Enzymes that are inactive because we don’t want the metabolic process to occur
Requires cofactors to be activated (holoenzyme)

29
Q

Vmax

A

Maximum initial velocity/ rate of enzyme controlled reaction

30
Q

Digestion of starch

A

Starch + amylose –> maltose
Occurs in mouth (saliva) and small intestine (pancreatic juice)
Maltose + maltase –> glucose (absorbed directly into bloodstream)
Occurs in small intestine

31
Q

Digestion of proteins

A

Trypsin catalyses breakdown of proteins into smaller peptides in small intestine - release w/ pancreatic juices
AA absorbed by cells lining digestive system and then absorbed into the bloodstream

32
Q

pH of enzymes in small intestine

A
8
Trypsin
Lipase
Amylase
Maltase
33
Q

How to increase Vmax

A

Add more enzyme

Increase temp

34
Q

End product inhibition

A

Example of -ve feedback
Prevents waste of resources to make excess products
Example of non competitive reversible inhibition

35
Q

Precursors (Zymogens)

A

Require action of another enzyme to bring about change in 3’ structure