Metabolism 1

Question 1

What is the first and second law of thermodynamics?

Answer 1

-1st law = energy cannot be created or destroyed
-2nd law = entropy always increases

Question 2

What does metabolism involve?

Answer 2

-making things - anabolism
-breaking things down - catabolism

Question 3

Are anabolic processes ender or exergonic?

Answer 3

-endergonic
-not spontaneous - +ΔG

Question 4

Are many catabolic processes ender or exergonic?

Answer 4

-exergonic
-spontaneous - -ΔG

Question 5

What are metabolic pathways?

Answer 5

A series of linked reactions usually involving a discrete enzyme at each step that catalyses the conversion of 1 molecule in the pathway to another

Question 6

What must all metabolic pathway be?

Answer 6

-physically possible - all enzymes present + accessible
-thermodynamically likely - net -ive ΔG
-kinetically feasible
-shielded from unwanted side reactions

Question 7

What are the benefits of metabolic pathways?

Answer 7

-make complex transformations kinetically possible
-allow multiple energy production sites by releasing free energy in manageable ‘packets’
-generate a diverse range of chemical structures
-allow a high level of control

Question 8

Why do metabolic pathways allow for a higher level of control?

Answer 8

More steps = more potential control sites

Question 9

What are the common features of metabolism?

Answer 9

-involves many common pathways shared by most living things
-has 6 basic types of reactions
-has common organisational paradigms - each reaction can be divided to different organelles
-involves a common set of regulatory principles
-involves use of common set of cofactors that evolved in RNA world
-uses ATP as an energy source

Question 10

What are the 6 basic types of reaction?

Answer 10

-oxidation reduction
-ligation requiring ATP cleavage
-isomerisation
-group transfer
-hydrolytic
-addition or removal of functional groups

Question 11

What happens in an oxidation reduction reaction?

Answer 11

Electron transfer

Question 12

What happens in a ligation requiring ATP cleavage reaction?

Answer 12

Formation of covalent bonds

Question 13

What happens in an isomerisation reaction?

Answer 13

Rearrangement of atoms to form isomers

Question 14

What happens in a group transfer reaction?

Answer 14

Transfer of a functional group from 1 molecule to another

Question 15

What happens in a hydrolytic reaction?

Answer 15

Cleave bonds by addition of water

Question 16

What happens in an addition or removal of functional groups reaction?

Answer 16

Addition of functional groups to double bonds or their removal to form double bonds

Question 17

What can common organisational paradigms have?

Answer 17

-physically separate, soluble enzymes with diffusing intermediates
-a multienzyme complex (metabolons) with substrate channels between them sequentially before product release
-a membrane bound multi-enzyme system

Question 18

What are the benefits of having organisational paradigms?

Answer 18

-substrate channelling - substrate moved directly from enzyme of 1 active site to the next without releasing it into the bulk solution
-increases rate - effective conc. of enzymes + reactants are increased
-avoids unwanted side reactions + futile cycling

Question 19

How can we discover and study different pathways?

Answer 19

-cell fractionation
-inhibitors
-radiotracers
-mutants

Question 20

How can cell fractionation be used to study different pathways?

Answer 20

-homogenise tissue to break open cells
-density gradient ultracentrifugation
-test which components have particular enzyme activity of interest - localisation of pathways

Question 21

How can inhibitors be used to study different pathways?

Answer 21

-specific compounds can be tested for inhibitive properties
-inhibited step identified due to build up of reactants
-inhibitors sometimes bind irreversibly to proteins, allowing enzyme to be identified

Question 22

How can radiotracers be used to study different pathways?

Answer 22

-radioactive C14 can be converted to CO2
-can follow which plants incorporate the radioactive carbon into their molecules

Question 23

How can mutants be used to study different pathways?

Answer 23

-specific genes knocked out, preventing synthesis of the protein it encodes
-allows the step catalysed by the protein to be identified as reactant builds up

Question 24

How can energy be obtained from reduced carbon sources?

Answer 24

-reactions performed step wise - release energy from source in controlled way
-energy can be captured + stored in activator carrier molecules
-total free energy change the same in both routes

Question 25

Describe the stability of C-H bonds compared to C-O and C=O bonds

Answer 25

Less stable