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BIOSCI 106 > Section 3: Energetics of Life > Flashcards

Section 3: Energetics of Life Flashcards

1
Q

3 key common features of life

A

Proton gradients
Reducing power (FAD/FADH, NAD+/NADH, Fe2+/Fe3+, FeS compounds)
ATP (energy currency)

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2
Q

Proton gradients

A

Essentially universal for metabolism by all living organisms
An energy-coupling mechanism that uses energy stored in the form of an H+ gradient across a membrane to drive cellular work

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3
Q

Proton gradients - mitochondria

A

Energy for gradient from: food

Proton gradient concentrated in: intermembrane space

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4
Q

Proton gradients - bacteria

A

Energy for gradient from: nutrients

Proton gradient concentrated in: intermembrane space

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5
Q

Proton gradients - chloroplasts

A

Energy for gradient from: light

Proton gradient concentrated in: thylakoid lumen

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6
Q

Electron donor AKA

A

Reducing agent

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7
Q

Electron acceptor AKA

A

Oxidising agent

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8
Q

Oxygen is an example of a(n) _____ agent

A

Oxidising

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9
Q

What is ferredoxin

A

An example of an FeS compound

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10
Q

What does nature use to produce cellular products

A

Both reducing power and ATP

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11
Q

What are NAD(P)H and ATP widely used in

A

Widely used in metabolism to reduce CO2

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12
Q

Structure of NAD+, NADP+ and FAD

A

Share structural similarities
NADP+ is NAD+ except with a phosphate group attached to the ribose sugar
FAD also structurally similar

(must be able to recognise the structures!)

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13
Q

Levels of NAD+ and NADH that indicate energy state of a cell

A

Low NADH compared to NAD+ = low energy

High NADH compared to NAD+ = high energy

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14
Q

What was present in LUCA

A

Proton gradients
Reducing power (ferredoxin)
ATP

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15
Q

What did LUCA’s metabolism rely on

A

Relied on using H2 as an energy source to reduce CO2

O2 was largely absent –> very reducing atmosphere

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16
Q

LUCA genes

A

Those of a strictly anaerobic H2-dependent thermophilic

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17
Q

Genetic data places LUCA in a ___ setting, rich in ____

A

Hydrothermal vent setting
H2, CO2, transition metals, sulfur
Lots of abundant Fe2+

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18
Q

LUCA might have evolved at…

A

Alkaline hydrothermal vents

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19
Q

White smokers

A

Chimneys characterised by barium, calcium and silicon deposit which are white

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20
Q

What did the alkaline vent provide

A

Provided a natural proton gradient

Ocean had pH 6 and vent had pH 9

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21
Q

pH = ?

A

-log10 [H+]

Each pH unit represents a 10-fold change in H+ conc

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22
Q

Hadean ocean - H+ conc

A

Contained 1000x more H+ than the alkaline vent

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23
Q

What led to the reduction of CO2 by hydrogen

A

A combination of proton gradients and reducing power (FeS clusters)

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24
Q

Vents: Reduction of CO2 by H - steps

A

H2 within vent transfers its e- to FeS clusters at vent interface
FeS clusters transfer these e- to CO2 to reduce it to formic acid (HCOOH) and more reduced compounds (CH2O)

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25
Q

Vents: Reduction of CO2 by H - reducing power is generated where?

A

Within the FeS clusters which mediate the reduction of CO2 by H

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26
Q

Reduction of CO2 by H ultimately led to..

A

The development of the building blocks needed for LUCA to evolve
LUCA now had an established genetic code and ability to produce proteins

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27
Q

Protocel membrane

A

Leaky –> provides some protection

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28
Q

LUCA - ATP synthase

A

After reduction of CO2, ATP was produced through ATP synthase utilising proton gradient provided by vent

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29
Q

LUCA: ECh

A

Energy converting hydrogenase
Harnessed power of natural proton gradient by vent to generate reducing power (e- from H2) in the form of ferredoxin
Ancestor of complex I

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30
Q

LUCA: Reduced ferrodoxin and ATP can then be used to…

A 
Reduce CO2 directly to provide the building blocks LUCA needed to function
Forms C(x)H(y)O(z)
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31
Q

Archaea bacteria producing methane

A

Known as methanogens
Still use H2 as an energy source to reduce CO2
Has similarities in process to LUCA

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32
Q

Methanogens - FeS clusters

A

Methanogens still use FeS clusters within proteins to catalyse reactions (preserved within active sites of proteins)

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33
Q

What could methane indicate

A

Existence of methane on other planets (Mars) could indicate presence of life by microbes

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34
Q

Problem with genetic analysis of LUCA

A

Things like bacteria can transfer its DNA which then becomes incorporated into the genome

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35
Q

Reducing power of FeS complexes

A

Accept e- then donate them to something else

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36
Q

Where is the alkaline vent located

A

Along the mid-Atlantic ridge - the point in the earth’s crust where 2 tectonic plates are moving away from each other

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37
Q

Mid-Atlantic ridge

A

Responsible for breaking up the potent Pangea
Comes to surface in Iceland
Vents form

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38
Q

LUCA: Ocean was rich in..

A

CO2

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39
Q

LUCA: Where were FeS clusters located

A

In wall of the vent itself

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40
Q

What is free energy

A

A quantity used to determine the spontaneity of a process, i.e. what direction a reaction will occur
Refers to change of enthalpy and change of entropy, the combination of which determines whether a process occurs

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41
Q

ΔH

A

Enthalpy change
Describes heat of a reaction
Describes first law of thermodynamics

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42
Q

ΔS

A

Entropy
Change in order to disorder
The entropy (disorder) of any closed system not in thermal equilibrium almost always increases (2nd law of thermodynamics)

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43
Q

Gibbs free energy (G)

A

The energy that can be converted into work at a uniform temp and pressure throughout a system

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44
Q

Free energy - -ve, +ve and 0 values

A

If ΔG -ve (E° +ve), reaction proceeds in direction indicated
If ΔG zero, reaction is in equilibrium
If ΔG +ve (E° -ve), reaction proceeds in opposite direction, i.e. becomes a strong reducing agent

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45
Q

A reaction towards ‘more organised’ can only proceed if…

A

The enthalpy change (ΔH) overrides the decrease in entropy (ΔS)

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46
Q

ATP to ADP - entropy

A

Entropy increases as one ATP molecule is split into one ADP and one Pi (i.e. one molecule to 2 molecules)

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47
Q

First step of glycolysis

A

Reaction is regarded as essentially irreversible as it proceeds with a large -ve free energy change
However, the driving force comes from the free energy change that occurs during the conversion of ATP to ADP
Attaching a phosphate group to glucose doesn’t proceed spontaneously under standard conditions, so couple to ATP hydrolysis to make it spontaneous

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48
Q

Rust - what is oxidised and reduced

A

Iron is oxidised

Oxygen is reduced

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49
Q

Reduction potential

A

A measure of the tendency of a chemical species to acquire from or lose e- to an electrode and thus be reduced or oxidised
i.e. measures free energy changes for REDOX reactions

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50
Q

What reduction potential measured in

A

Volts (V)

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51
Q

Reduction potential - a higher E° value means…

A

It has a higher ‘pulling’ power to accept electrons (i.e. takes e- from other compound reaction)

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52
Q

Standard reduction potential is defined relative to…

A

A standard H reference electrode, given a potential of 0V

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53
Q

Standard reduction potential - concentrations

A

Each compound is at a conc of 1M (pH 0) and H2 is 1 atm

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54
Q

Reduction potential - the half reaction with the more -ve E° value is…

A

Reversed

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55
Q

Reactions - pH

A

Changing the pH (H+ conc) can alter the direction of the reaction

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56
Q

E°’

A

The reduction potential under physiological conc; a H+ conc of 10^-7 mol/litre (i.e. pH 7)

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57
Q

A very large -ve change in free energy essentially means…

A

The reaction is irreversible (steep waterfall)

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58
Q

ATP conversion to ADP and Pi - enthalpy and entropy change

A

Enthalpy change is -ve
Entropy change is +ve (1 –> 2 molecules)
Overall ΔG is -ve

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59
Q

Half reactions have a _____ associated with it

A

Standard reduction potential (E°)

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60
Q

Calculating standard reduction potential - agar bridge

A

Links two solutions for charge neutrality

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61
Q

If calculating reduction of compound x by H2..

A

Reverse the H2 reaction

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62
Q

Chiral molecule

A

Non-superimposable on its mirror image

4 diff groups attached

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63
Q

Glucose - numbering of Cs

A

Numbering of Cs starts from aldehyde group

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64
Q

In what forms do glucose and ribose exist in

A

Both exist in equilibrium as open and ring structurse

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65
Q

Glucose and ribose - chiral or non-chiral?

A

Both have chiral Cs and non-chiral Cs

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66
Q

What does the D/L notation tell us

A

Which of the two chiral isomers we are referring to

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67
Q

Glucose and ribose: Determining D/L notation

A

If -OH on highest numbered chiral C points to the right, isomer is D-isomer
If -OH on highest numbered chiral C points to the left, isomer is L

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68
Q

Which D/L form is usually found in nature

A

D form

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69
Q

Fischer projection - right vs left

A

Straight line
Right = below plane of ring
Left = above plane of ring

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70
Q

Haworth projection

A

Ring structure

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71
Q

Cyclic form - aldehyde

A

In cyclic form, the aldehyde group is lost because it’s used to complete the cyclic structure

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72
Q

Equilibrium - cyclic vs straight chains

A

Equilibrium heavily favours cyclic structures, so only a small amount of straight chain form of carbohydrate is present

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73
Q

Cyclic form - forms of glucose

A

2 distinct forms of glucose
C1 can have its attached -OH group either below the plane of the ring (α-glucose) or above the ring (β-glucose)
In aqueous solution, are in equilibrium

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74
Q

How do α and β forms interchange

A

Molecules pass through the straight-chain form to get from one structure to the other

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75
Q

Difference between α and β ring structures

A

Position of hydroxyl group attached to C1
In α form, it’s below plane of ring
In β form, it’s above plane of ring

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76
Q

Anomeric C and anomers

A

Since there can be 2 diff orientations around C1, it’s referred to as the anomeric C, and the two forms of glucose (α and β) are called anomers

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77
Q

Enantiomers

A

Compounds that are mirror images of each other

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78
Q

Diastereomers

A

Other compounds that aren’t enantiomers

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79
Q

Epimers

A

Compounds that differ only in the orientation of ONE hydroxyl group attached to a chiral C
i.e. hydroxyl group can occur on left or right-hand side

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80
Q

Cellulose - α or β?

A

Cellulose is a polymer of glucose monomers, using β-1,4-glycosidic linkages - allows cellulose to form very long and straight chains - tend to be very strong

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81
Q

Cellulose - how do hydroxy groups on glucose molecules align

A

Side-by-side (straight road)

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82
Q

Cellulose - branching

A

Cellulose doesn’t contain a branchpoint

83
Q

Cellulose makes up ___% of organic matter in the biosphere

A

~50%

84
Q

Most of the carbohydrate found in nature occurs as…

A

Polysaccharides

85
Q

How do polysaccharides differ from each other

A

Recurring monosaccharide unit
Length of chains
Types of bonds linking units
Degree of branching of chains

86
Q

Most abundant polysaccharides

A

Cellulose and starch - both made by plants and consist of recurring units of D-glucose, but differ in type of linkage between glucose molecules

87
Q

Examples of α-glucose polymers

A

Glycogen (muscle) and starch (plants)

Form helical-like structures - not straight –> accessible?

88
Q

Glycogen

A

Humans and other vertebrates store glycogen in liver and muscles
During intense exercise, glycogen is degraded in skeletal muscle through glycolysis to produce ATP

89
Q

Glycogen and starch - OH groups

A

Hydroxy groups point outwards

Shaped a bit like a corkscrew

90
Q

Types of α bonds

A

α-1,4,-glycosidic bonds: linear chains of glucose molecules

α-1,6-glycosidic bonds: branch points, form at every ~10 glucose units

91
Q

Glycogen - branching

A

Glycogen is a highly branched molecule

92
Q

Glycolysis: “Rome of metabolism”?

A

All catabolic routes lead to glycolysis

Fundamental pathway where many things link in and link out

93
Q

Ways glycolysis produces energy (as ATP)

A
  • Directly via substrate level phosphorylation

- Indirectly through production of reducing power in form of NADH

94
Q

Glycolysis: Substrate level phosphorylation

A

Where a substrate donates a phosphate to ADP to form ATP

95
Q

Glycolysis: ‘Energy’ in released e- is captured by..

A

NAD+ to produce NADH

96
Q

Le Chatelier’s principle

A

The effect of a change in conditions (e.g. substrates or products) will result in a change in equilibrium of the system

97
Q

Glycolysis: High vs low NAD+/NADH ratio

A

High NAD+/NADH ratio (glycolysis) drives reaction forward

Low NAD+/NADH ratio (gluconeogenesis) drives reaction in reverse

98
Q

Hexokinase

A

Inhibited by its product G6P
Has a rather braod specificity - able to phosphorylate to a number of hexode and pentose sugars - enables them to release energy via glycolysis

99
Q

Hexokinase - K(M) for glucose

A

10-20 µm

100
Q

Phosphofructokinase (PFK)

A

Composed of 4 monomeric protein units that are tightly controlled so feeding-in of substrates into pathway can be switched on/off

101
Q

What is PFK activated/inhibited by

A

Activated by several compounds, e.g. ADP, AMP and fructose-2,6-bisphosphate –> stimulates glycolysis
Inhibited by ATP and citrate

102
Q

What is pyruate kinase inhibited by

A

High levels of ATP

Acetyl-CoA

103
Q

What is pyruvate kinase activated by

A

Fructose-1,6-bisphosphate

104
Q

ATP from glycolysis vs from mitochondria

A

Amount of ATP you can generate through glycolysis is more than through the mitochondria

105
Q

Free energy for glucose to pyruvate is…

A

-ve

Used to drive energy production; one in form of ATP and the other in form of reduced co-factors

106
Q

Why are e- transported by a chain

A

Couples the energy in a form of co-factors so you don’t get an ‘explosion’

107
Q

When is glucose completely oxidised

A

When pyruvate is formed, still not completely oxidised

Only when it enters the mitochondria it is completely oxidised to CO2 and H2O

108
Q

ATP yield for 1 molecule of NADH

A

2.5

109
Q

ATP yield for 1 molecule of FADH2

A

1.5

110
Q

Number of protons pumped across membrane by complexes I-IV

A

C I: 4 H+
C III: 4 H+
C IV: 2 H+

111
Q

How mitochondria evolved

A

Archaea engulfed a protobacterium to form a proto-eukaryotic cell
Protobacterium is what evolved into the mitochondrion

112
Q

What is chemiosmosis

A

The diffusion of ions across a selectively permeable membrane
Relates to generation of ATP by movement of H+ ions across a membrane during cellular respiration

113
Q

Cellular respiration generates ____ ATPs per second in one cell

A

10 million

114
Q

Chemiosmotic hypothesis

A

Electron transfer through the respiratory chain leads to pumping of protons from matrix to cytoplasmic side of inner mitochondrial membrane
pH gradient and MP constitute a proton-motive force used to drive ATP synthesis

115
Q

Chemiosmotic coupling

A

Pumping of protons across inner mitochondrial membrane produces a H+ gradient
Membrane is impermeable to protons, so uses channels to allow protons to diffuse back
However, to get back into the matrix, protons are forced to do some work - chemiosmosis

116
Q

ATP synthase - protein complexes

A

Composed of 2 complexes

F(0) and F(1) protein complexes

117
Q

ATP synthase - F(0) complex

A

Incorporated into the membrane
Comprises 3 diff polypeptide chains
Forms the channel through which protons can diffuse from intermembrane space into matrix

118
Q

ATP synthase - F(1) complex

A

Buds into matrix side of membrane

Catalytic known - shaped like a sphere, composed of 5 protein chains, and is the site where ATP synthesis occurs

119
Q

ATP synthase - stator

A 
Connects F(0) and F(1) complexes
Consists of an 'a' subunit, 'b' subunits and the δ subunit
120
Q

Oxidative phosphorylation: For every 2 e- carriers…

A

One O2 molecule is reduced to 2 water molecules

121
Q

Does ETC generate ATP

A

Not directly, but flow of e- through complexes is used to pump H+ from matrix into intermembrane space

122
Q

ETC - free energy

A

ETC breaks the large free energy drop from food to oxygen into a series of smaller steps that release energy in manageable amounts

123
Q

Electronegativity

A

The tendency of an atom to attract e- to itself

124
Q

Direction of e- flow in electron transport chain

A

O2 > IV > C > III > Q > I and II > NADH and FADH2

125
Q

ETC: NADH electrons

A

E- carried by NADH lose very little of their potential energy in this process
This energy is tapped to synthesise ATP as e- ‘fall’ from NADH to O2

126
Q

Where are copies of ETC found

A

In extensive surface of cristae (inner membrane of mitochondrion)

127
Q

ETC: Are proteins fixed?

A

Most components are proteins that are bound with prosthetic groups that can alternate between reduced and oxidised states as they accept and donate e-

128
Q

ETC: Free energy change from ‘top’ to ‘bottom’

A

-53 k.cal/mol of NADH

129
Q

Complex I - what does it contain

A

An FMN prosthetic group and an Fe-S cluster

130
Q

Complex I - process

A

NADH –> NAD+ and the e- are passed onto an Fe-S protein where Fe3+ is reduced to Fe2+
E- make their way via additional Fe-S centres to UQ / coenzyme Q
Fe within Fe-S clusters alternate between Fe2+ and Fe3+
Complex Q ultimately becomes reduced to CoQH2

131
Q

Complex II - what does it contain

A

Succinate dehydrogenase (from CAC)

132
Q

Complex II - process

A

H+ ions obtained from conversion of succinate to fumerate are transferred to CoQ along with 2e-
FADH2 is re-oxidised and e- are transferred to an FeS-containing protein where Fe3+ is reduced to Fe2+
FeS containing protein donates e- to coenzyme Q –> CoQH2
Fe2+ of FeS containing protein is re-oxidised to Fe3+

133
Q

Complex II - FADH2

A

FADH2 produced by succinate DH is very tightly bound

FAD is covalently bound to enzyme so the FADH2 produced can’t be released into the medium

134
Q

Complex III - what does it contain

A

Heme groups and Fe-S containing proteins

135
Q

Complex III - process

A

E- from reduced CoQH2 are passed through FeS proteins and eventually to cyt C
Q cycle takes place
E- from either NADH or FADH2 end up on a cytochrome c enzyme, which is attached to intermembrane space side of membrane

136
Q

Complex III - Q cycle

A

Indicates the flow of e- from CoQH2 doesn’t take a simple direct path

137
Q

Complex IV - what does it contain

A

Fe-S containing proteins

2 copper ions - participate in flow of e- and lie between cyt a and cyt a3

138
Q

Complex IV - process

A

Transfers e- from cyt c to oxygen through Fe-S containing proteins, producing water

139
Q

Brown fat cell

A

Converts chemical energy to heat to protect against cold weather

140
Q

Beige fat cell

A

Immature cell in white fat tissue matures to burn fat

141
Q

White fat cell

A

Most common fat cell
Used to store fat
Found beneath skin and abdomen
Stores triglycerides

142
Q

Uncoupling protein (UCP)

A

Process that simply lets protons back in without having to drive ATP synthase - generates heat

143
Q

Brown fat in adults

A

Humans do have brown fat stores, but are only activated in cold temperatures

144
Q

Brown fat in adults

A

Humans do have brown fat stores, but are only activated in cold temperatures

145
Q

ETS: Q and C

A

Soluble mediators

Shuttle e- from complexes to each other

146
Q

ATP synthase: Where does catalysis occur

A

At interface between dimers

147
Q

Brown and beige fat cell vs white fat cell

A

Brown and beige fat cells have more mitochondria

148
Q

Glycolysis: Net equation

A

Glucose + 2NAD+ + 2ADP + 2Pi –> 2 pyruvate + 2NADH + 2ATP

149
Q

Glucogeneogenesis - pyruvate

A

Pyruvate (generated in muscle and other tissues) is converted/transanimated to alanine, which is then returned to the liver for gluconeogenesis
Known as transamination reaction

150
Q

Glucose-alanine cycle

A

An indirect way for muscle to get rid of nitrogen while replenishing its energy supply
Allows non-hepatic tissues to deliver the amino portion of catabolised amino acids to liver for excretion as urea by kidneys

151
Q

Transamination reaction

A

Glucose-alanine cycle

Requires transfer of an amino group

152
Q

Glucose-alanine cycle - liver

A

Alanine is converted back to pyruvate and used to make glucose or be oxidised further through CAC

153
Q

In the liver, what is the first step of gluconeogenesis

A

Conversion of pyruvate to oxaloacetate

154
Q

Conversion of pyruvate to oxaloacetate

A

Anabolic reaction

Catalysed by pyruvate carboxylase which uses CO2 and ATP as the free energy source –> enters Krebs cycle

155
Q

Carboxylation

A

Addition of CO2

156
Q

Conversion of pyruvate to oxaloacetate is stimulated by…

A

Acetyl CoA

157
Q

Pyruvate - if O2 is present…

A

Pyruvate can enter the mitochondria and be completely oxidised to CO2 and H2O

158
Q

Pyruvate - if O2 isn’t present…

A

Pyruvate can’t be completely oxidised
Cell needs other ways to regenerate NAD+ for glycolysis to proceed
To do this, pyruvate can be reduced to alcohol/ethanol (fermentation) or lactate

159
Q

Without mitochondria or oxygen…

A

NADH builds up and exhausts the NAD+ pool, causing glycolysis to shut down
Thus, cells must have a way of reconverting NADH to NAD+ - fermentation

160
Q

Alcohol fermentation

A

Occurs under anaerobic conditions

Allows generation of ATP by glycolysis and regenerates NAD+ by transferring e- from NADH to acetaldehyde

161
Q

Alcohol fermentation: How is pyruvate converted to ethanol

A
  1. Pyruvate is converted to acetaldehyde by removal of CO2

2. Acetaldehyde is reduced by NADH to ethanol

162
Q

Alcohol - acetaldehyde

A

Quite toxic

163
Q

Lactic acid fermentation

A

Pyruvate is directly reduced by NADH to form lactate

Allows a way for NAD+ to be regenerated

164
Q

Lactate

A

Ionised form of lactic acid

165
Q

Lactic acid fermentation in humans

A

Strenous exercise –> anaerobic conditions
O2 in muscles is depleted
Lactate builds up as glycolysis continues
Muscles tire and become painful
Breathing rate increases

166
Q

In animals under anaerobic conditions, where is lactate produced

A

In muscles

167
Q

Lactate dehydrogenase

A

Catalyses reduction of pyruvate

168
Q

Transport of lactate

A

In human muscles, lactate can be readily transported across cell membrane via bloodstream to liver where there is good oxygen supply

169
Q

Cori cycle

A

Transfer of lactate from muscle to liver, and transfer of glucose from liver to muscle
i.e. lactate –> pyruvate –> glucose –> resupplied to muscle by bloodstream

170
Q

In the liver, lactate can be converted to glucose by…

A

Gluconeogenesis

171
Q

Operation of glycolysis and gluconeogenesis

A

Possible to have both operating simultaneously in body, i.e. diff tissues can operate in diff ways

172
Q

Aerobic respiration: Conversion of pyruvate to acetyl CoA - enzyme

A

Pyruvate dehydrogenase converts pyruvate to acetyl CoA

Occurs in mitochondria, so requires transport of pyruvate into mitochondrial matrix

173
Q

Pyruvate dehydrogenase

A

Converts pyruvate to acetyl CoA

Regulates entry of pyruvate into CAC

174
Q

How much of the original energy in glucose is still present in two molecules of pyruvate

A

More than 3/4

175
Q

Aerobic respiration - NADH

A

e- of NADH are ultimately passed to O2, generating ATP by oxidative phosphorylation

176
Q

Pyruvate dehydrogenase catalyses these sequence of reactions

A

A CO2 is removed from pyruvate - 3C –> 2C in form of an acetyl group
NAD+ is reduced to NADH
CoA is coupled to acetyl group molecule to form acetyl CoA, which is ready to be completely oxidised through CAC

177
Q

Total yield from one glucose

A 
4 ATP (2 from glycolysis, 2 from CAC)
10 NADH (2 from glycolysis, 8 from CAC)
2 FADH2 (from CAC)
178
Q

CAC aka

A

Krebs cycle

TCA cycle

179
Q

Breakdown of glucose to CO2 and H2O is coupled to…

A

ATP production and generation of reducing power (NADH and FADH2)

180
Q

Pyruvate dehydrogenase - switch

A

Acts as a switch

If switched off, pyruvate can’t be converted to acetyl CoA, so instead is made into lactate

181
Q

What is pyruvate dehydrogenase regulated by

A

Metabolic conditions within the cell

182
Q

Net ATP yield from diff stages of cellular respiration

A

Glycolysis: 2 ATP
CAC: 2 ATP
ETS: 26-28

183
Q

Cellular respiration is very efficient in…

A

Energy conversion

184
Q

A single 6C glucose molecule is oxidised to..

A

6 CO2 molecules

185
Q

Gluconeogenesis

A

The generation of glucose from other organic molecules (e.g. pyruvate and lactate)

186
Q

Where does gluconeogenesis take place

A

Mostly in liver, and to a smaller extent in the kidney

187
Q

What does gluconeogenesis require

A

An investment of energy in the form of ATP and NADH

188
Q

How are glycolysis and gluconeogenesis regulated

A

Reciprocally regulated
Both pathways don’t operate at the same time
Occurs through:
- local allosteric control (Determined by cell’s energy status)
- global control (circulating hormones which can activate cellular signalling cascades that override local metabolic conditions)

189
Q

Can skeletal muscle make glucose

A

No - it traps glucose from bloodstream and stores it as glycogen or metabolises it

190
Q

Gluconeogenesis: How does oxaloacetate leave the mitochondria

A

By a specific transport system in the form of malate, which is re-oxidised to oxaloacetate in the cytoplasm

191
Q

Gluconeogenesis: Bypass I

A

First step:
Involves carboxylation of pyruvate to produce oxaloacetate
Adds a CO2

Second step:
Catalyses phosphorylation and decarboxylation of oxaloacetate to yield phosphoenol pyruvate
Phosphate group is derived form GTP or ATP

192
Q

Hexokinase vs glucokinase

A

Glucokinase has a much lower affinity for glucose, so glycolysis is less prone to proceed in the liver - the main site for gluconeogenesis

193
Q

Gluconeogenesis: Bypass III

A

Removal of phosphate from G6P to give glucose, which can then pass through the cell membrane into the blood

194
Q

Gluconeogenesis: Increased conc of acetyl CoA leads to…

A

Inhibition of pyruvate kinase –> helps prevent futile cycle
Inhibition of pyruvate DH –> pyruvate doesn’t enter oxidative route to acetyl CoA
Stimulation of pyruvate carboxylase

195
Q

Glycolysis equation

A

Glucose + 2NAD+ + 2ADP + 2Pi –> 2 pyruvate + 2NADH + 2ATP

196
Q

Gluconeogenesis equation

A

2 pyruvate + 2 NADH + 4ATP + 2GTP –> glucose + 2NAD+ + 4ADP + 2GDP + 6Pi

197
Q

Gluconeogenesis expends how many ATP/GTP?

A

6

198
Q

A futile cycle of both pathways (glycolysis and gluconeogenesis) would waste how many ATP/GTP per cycle?

A

4

199
Q

Regulation of bypass I, II and III

A

Bypass III isn’t as regulated compared to I and II

200
Q

Hexokinase and glucokinase - G6P

A

Glucokinase is NOT inhibited by G6P

201
Q

What can be used as a carbon source

A

Alanine
Lactate (from muscle)
Glycerol

202
Q

Is glucokinase required for glycogen degradation

A

No

203
Q

Glucokinase is a(n) _____ of hexokianse

A

Isoform

204
Q

What can be used as a carbon source for gluconeogenesis

A

Alanine
Lactate
Glycerol

Not fatty acids

BIOSCI 106 (6 decks)

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