FSE Study Flashcards
T10: What is metabolism and what are the two types of reactions that occur with in cells?
Metabolism: Sum of ALL biochemical reactions w/in cell
Catabolic (exergonic) reactions: energy-liberating (∆G is -ve). Spontaneous.
Anabolic (endergonic) reactions: energy-requiring (∆G is +ve). Not sponaneous.
T10: What is causes thermodynamically unfavourable (endergonic/anabolic) reactions to occur?
They are coupled w/ exergonic/catabolic reactions so overall process has a -ve free energy change and so will occur spontaneously.
T10:What is reciprocal regulation and why does it occur?
Activation of one pathway, suppression of another.
Used to prevent simultaneous synthesis and degradation which is wasteful
T10: When ∆G is -ve, what happens to a reaction?
Reaction:
releases energy
is exergonic/catabolic
thermodynamically favourable
Can proceed in absence of energy -spontaneous
T10: When ∆G is +ve, what happens to a reaction?
Reaction:
Requires energy
is endergonic/anabolic
thermodynamically unfavourable
Energy must be supplied
T10: Please remind yourself of the ∆G’˚/Keq equation, ∆G equation and did you know this is related the free energy change?!
How are they related? *hint use an equation
Keq = [C] [D]/ [A] [B]
products/reactants
- Related because ∆G’˚ = -RT In Keq
- ∆G = G’˚ + RT Ln Keq
R=gas constant 8.315 J/mol. K
T=absolute temp (K) 298
T10: When Keq is
>1.0
1.0
>1.0 = -ve 1.0 = zero
T10: What is reduction potential? What is the equation used to measure energy made available from these reactions?
+ve E (reduc. potent.) =?
-ve E (reduc. potent.) =?
Reduction potential (E) is a measure of a reducing agents affinity for electrons ∆G = -nF ∆E Where n= number of electrons transferred F= Faraday constant (96 480 J/V.mol)
+ve E= Gives rise to -ve ∆G
strong tendency to accept electrons and become reduced
-ve E= strong tendency to lose electrons and become oxidised
T11: Write out the net equation of Glycolysis
Glucose + 2NAD+ + 2ADP + 2Pi
=>
2 Pyruvate + 2NADH + 2ATP + 2H+ + 2H2O
T11: Draw a flow chart giving the brief details of glycolysis
PIPCIRSIDS
- IR, Phosphorylation (6C) COST 1 ATP
- R, Isomerisation 6C
- IR, Phosphorylation (6C) COST 1 ATP
- rate limiting, 1st committed step - R, Cleavage (6C=> 2 x 3C)
- R, Isomerisation 3C=>3C
- R, REDOX (3C) GAIN 2 NADH
- R, Substrate-level phosphorylation (3C) GAIN 2 ATP
- R, Isomerisation (3C)
- R, Dehydration 3C
- IR, Substrate-level phosphorylation (3C) GAIN 2 ATP
T11: What is the cost and yield of:
Glycolysis?
GNG?
Glycolysis:
Cost = 2 ATP
makes = 4 ATP
Net yield = 2 ATP, 2 NADH
GNG:
Cost = 6 ATP
Yield =glucose
T11: How much ATP is generated from..
Aerobic respiration?
Anaerobic respiration?
Aerobic = 30/32 ATP
Anaerobic = 2 ATP
T11: Write out the equation (stoichiometry) for the glycolytic pathway in relation to ATP production & electron balance
Glucose + 2ATP + 2 NAD + 4ADP + 2Pi => 2Pyru + 4 ATP + 2NADH + 2H + 2ADP + 2H2O reduces to Glucose + 2NAD + 2ADP + 2Pi => 2Pyru + 2ATP + 2NADH + 2H + 2H2O
T11: Gluconeogenesis
Describe 1st bypass step
Last step of glycolysis (10)
Pyruvate converted to PEP
T11: Gluconeogenesis
Describe 2nd bypass step
Step 3 of glycolysis
Conversion of fructose 1,6bisphos. (ase) to fructose 6P
=> does not require ATP unlike glycolysis step
∆G˚ = -16.3 kJ/mol
T11: Gluconeogenesis
Describe 3rd bypass step
Step 1 of glycolysis
Conversion of glucose 6P (ase) to glucose
T11: Write the overall GNG equation
2Pyru + 4ATP + 2NADH + 2H + 4H2O
=>
Glucose + 4ADP + 2GDP + 6Pi + 2NAD
T12: Draw flow chart of glycogen catabolism and synthesis.
- Endeavour to include sugar nucleotide pathway and names of enzymes
- Try to explain if you can
see book
T12: Reciprocal regulation of reaction 3
Draw the flow chart (sl 35) of RRR3 identifying:
GNG is on or off
Glycolysis on or off
enzymes and energy molecules
Which signal molecules inhibit/activate either side
this is the one with the triangles and X’s
T12: Describe the role of hormones in carbohydrate metabolism
Draw the flow chart showing the influence of insulin (High BGL)
…
T12: Describe the role of hormones in carbohydrate metabolism
Draw the flow chart showing the influence of glucagon (low BGL)
…
T12: Reciprocal regulation of reaction 3
Enzymes
Describe the actions of Glycogen Phosphorylase (look at diagram in book to help with understanding or sl 17)
Catalyses breakdown of glycogen
Activated when BGL. Insulin activity
-inactive form (b) is unphosphorylated
T12: Reciprocal regulation of reaction 3
Enzymes
Describe the actions of Glycogen Synthase (look at diagram in book to help with understanding or sl 17)
Catalyses synthesis of glycogen
Activated when BGL>. Insulin activity
-active form (a) is unphosphorylated
Inactivated when BGL
T13: *Define cellular respiration & ID 3 stages of aerobic respiration
Define aerobic respiration and ID the 3 stages
Complete oxidation of glucose (pyruvate) to Co2 & H2O -30-32 ATP produced Requires O2 =>terminal electron acceptor Occurs in mitchondria 3 stages: 1. Formation of acetyl-CoA (link rxn) 2. Citric Acid cycle 3. Oxidative phosphorylation (e transport chain)
T13: *Describe the “link” reaction incl. components of the pyruvate DH complex & cofactors
Catalysed by pyru DH complex Composed of 3 distinct enzymes to form a multiple enzyme complex: -E1 (thiamine pyrophosphate attached) -E2 (lipolic acid att.) -E3 (FAD att.)
5 cofactors:
- Coenzyme A
- NAD+
- FAD
- Thiamine pyrophosphate (TPP)
- Lipolic acid
3 distinct rxns:
- Decarboxylation rxn
- Acylation rxn
- REDOX rxn
T13: Describe the 8 reactions of the citric acid cycle
RXN 1:
High E, IR condensation. E released by hydrolysis of acetyl-CoA thioester bond
RXN 2:
R, dehydration a) => hydration b)
RXN 3:
High E, IR oxidative decarboxylation. NAD reduced to NADH
RXN 4:
High E, IR oxidative decarboxylation. Similar to link rxn (E1, E2, E3). NAD reduced to NADH
RXN 5:
Substrate-level phosphorylation. Produces ATP/GTP
RXN 6:
Dehydrogenation. C=C produced, FAD reduced to FADH
RXN 7:
Hydration
RXN:
Dehydrogenation. ∆G’ strongly favours malate production -but proceeds to R due to removal of oxaloacetate by highly exergonic rxn 1 to produce citrate.
T13: Look at CA cycle diagram.
Which are the intermediates?
How many carbons do they have?
acetyl-coa = 2C
Citrate = 6C
Isocitrate = 6C
a-ketoglutarate = 5C
Succinyl-CoA = 4C
Succinate = 4C
Fumarate = 4C
Malate = 4C
Oxaloacetate = 4C
T13: *Describe the major controls operating on pyruvate DH & the CC cycle
draw diagram
Pyruvate DH complex Inhibited by high e levels -ATP -Acetyl-CoA -NADH -FA Stimulated by low e levels -AMP -Coenzyme A -NAD+
Citrate Synthase Inhibited by high e levels -ATP -Succinyl-CoA -NADH -Citrate Stimulated by low e levels -ADP
Isocitrate DH Inhibited by high e levels -ATP Stimulated by low e levels -ADP
a-ketoglutarate
Inhibited by high e levels
-Succinyl-CoA
-NADH
T13: Energy released by oxidation of acetyl-CoA in the CA cycle is conserved in the production of….?
3 NADH & 1FADH2 1 GTP (ATP)
T14: Give a brief overview of the ETC
Occurs in IMM
e from NADH/FADH2 transferred along chain to O2
Exergonic transfer of e is coupled w/ endergonic pumping of p to intermembrane space (IMS)
P move down their gradient back to matrix. This exergonic process is coupled w/ endergonic synthesis of ATP from ADP and Pi
T14: *Outline the sequence of e carriers
Draw the diagram of e carriers as shown in lecture with labels!!
Dont forget: IMS, p and n, matrix, succinate, fumarate, Cyt C, NADH, NAD+ etc
…
T14: *Account for the production of ATP during e transport according to chemiosmotic theory
e transport results in H transport -pumping of H ions out of matrix
Creates proton gradient -protons pass back through IMM through H+ pore in ATP synthase
Flow of H+ down [ ] leads to ATP synthesis -passage of h+ down proton-motive gradient causes a conformational change in 3D structure of ATP synthase, causing synthesus & release of ATP
T14: Calculate ATP yields for various substrates, given the stoichiometry of the reactions of these substrates in terms of yields of NADH & FADH2
10 protons are pumped per pair electrons from NADH
- 4 at CI
-4 at CIII
-2 at CIV
6 protons are pumped per pair electrons from FADH2
-4 at CIII
-2 at CIV
~ 4 protons are required to drive synthesis of one ATP molecule ::
-2.5 ATP are formed from one pair of electrons from NADH
-1.5 ATP are formed from one pair of electrons from FADH2
T14: The chemiosmotic theory
Flow of 2 electrons from NADH through ETC to O2 can be written as?
This net reaction is highly ……
?? kJ/mol?
How many H+ ions are pumped?
NADH + H+ + 1/2O2 => NAD+ + H2O
Highly exergonic
-220kJ/mol
For each 2 electrons transferred from NADH to O2 through ETC, 10 H+ ions are pumped from matrix to IMS
T14: *Describe the role of the malate-aspartate & glycerol 3P shuttles in transport of NADH from the cytoplasm
Describe the process of the malate-aspartate shuttle
NADH transferred as NADH
Generates 2.5 ATP
T14: *Describe the role of the malate-aspartate & glycerol 3P shuttles in transport of NADH from the cytoplasm
Describe the process of the glycerol-3P shuttle
NADH entered as FADH2
Bypasses CI; generates 1.5 ATP
T14: Regulation points
Energy (ATP) producing pathways are reciprocally regulated.
When ATP high/ADP low=?
When ATP low/ADP high=?
High ATP/Low ADP -glycolysis inhibited -CAC inhibited -Oxidative phosphorylation inhibited Low ATP/High ADP -Glycolysis activated -CAC activated -Oxidative phosphorylation activated
T15: *Describe action of lipases in hydrolysis of triacylglycerols
Describe a basic overview of the fate of dietary triacylglycerols
TAG’s are digested by pancreatic lipase
Produce FA, glycerol
Products are absorbed by intestinal cells
IC convert them back into TAGs and chylomicrons
Chylomicrons are released into blood stream/lymph sys to adipose/skeletal muscle
TAGs are hydrolysed to FAs & glycerol by lipoprotein lipase
Skeletal muscle = FA degraded (b-oxidation), producing ATP
Adipose = FA are re-esterified to TAGs for storage
T15: *Describe action of lipases in hydrolysis of triacylglycerols
Describe the function of hormone-sensitive lipase
Found in adipose
Catalyses breakdown of stored TAGs to FFA & glycerol
Regulation:
-activated by glucagon & adrenaline
-Glycerol is transported via blood to liver, enters glycolysis or gluconeogenesis
-FAs transported in blood to liver/skeletal muscle, used as fuel for b-oxidation
T15: *Outline processes of b-oxidation in FA catabolism
Define steps of FA catabolism
- FAs are activated by attachment of CoA
Converted to fatty acyl-CoA by acyl-CoA synthetase in cytoplasm
Requires ATP - The activated FA (fatty acyl-CoA) is transported to mitochondrial matrix via the carrier carnitine
see diagram in book = draw it
3. B-OXIDATION In final cycle, 2 acetyl-CoA released 1 NADH & 1 FADH2 produced 1. Oxidation acyl-CoA-DH
- Hydration
enoyl-CoA-hydratase - Oxidation
hydroxyacyl-CoA DH - Thiolytic cleavage
thiolase
T15: Please check lecture for slides 37 & 39 this is VERY IMPORTANT YOU CAN DO THIS CALCULATION
(n-2) / 2
C10 - 2 = 8
8 / 2 = 4 (4 rounds b-oxidation)
Always 1 round less than number of acetyl groups (or no# rounds + 1 = no# acetyl-CoA)
So = 5 acetyl-CoA
………………………………………………………
C14 = 7 rounds b-oxi 1 FADH2 & 1 NADH produced for every round per FADH2 = 1.5 ATP per NADH = 2.5 ATP No# ATP ultimately formed for NADH = 7x2.5 = 17.5 for FADH2 = 7x1.5 = 10.5
T15: *Outline synthesis of triacylglycerols from surplus CHD
Describe the actions of acetyl-CoA carboxylase & FA synthase complex
see book
A-CoA carboxylase=>uses cofactor biotin
Acetyl-CoA (2C) + HCO3 + ATP => Malonyl-CoA (3C) + ADP + Pi
FA synthase complex (reverse of b-oxi) 2c + 3c => 4c + 3c => 6C condensation reduction (NADPH consumed) dehydration reduction (NADPH consumed)
T15: *Describe regulation of FA metabolism
What do high glucose levels lead to?
> FA synthesis
inhibits carnitine acyl-transferase :: inhibits FA degradation
T15: *Describe regulation of FA metabolism
What do low glucose levels lead to?
FA degradation Glucagon release ∆PKA => GNG ∆hormone sensitive lipase =>mobilises stored FA X acetyl-CoA carboxylase;
T16: Describe amination
Glutamine synthetase catalyses addition of NH4+ onto glutamate => glutamine
Allows transport of NH4+ in blood
Liver; NH4+ re-released by glutaminase => urea
T16: Describe deamination
reverse of amination
Glutaminase (liver, kidney cortex)
-removes NH4+ from glutamine => glutamate
Glutamate DH (liver) -removal of amino group from glutamate => a-ketoglutarate
T16: Describe Transamination
aa transfers its amino group to a-ketog & is converted to keto acid
glutamate formed
no net deamin.
need PLP as cofactor
T16: Describe aa catabolism. When is it a energy source?
Is NOT a major energy source under NORMAL conditions Significant under 3 conditions: -dietary protein ingested in excess -severe starvation -stress situations
Catabolism in 4 easy steps!
- catabolism of protein w/in muscle results in formation of aa’s glutamine & alanine
- Transport of Glu & Ala into blood
- Ala => liver
- Glu => liver & kidney - Kidney - Glu deaminated twice => a-keto g. Ammonium excreted in urine. C skeleton used in glucose formation
- Liver - Ala & Glu from muscle, & all 20 aa from diet are deaminated => glutamate. C skeleton => glucose or ketone body. Glutamate deamin. in mitochondria & NH4+ converted to urea. Urea => liver => blood => kidney => excretion
T16: DRAW THE DIAGRAM THAT SUMMARISES AA CATABOLISM
Remember to include: Where there us organic or inorganic N transamination rxns deamination rxns PLP Where NH4+ is produced/released muscle/kidney/liver cell section mitochondria cell section
…
T11/12: Name, in order, the 11 enzymes of GNG
could use flow chart?
- Pyruvate carboxylase
- PEP carboxykinase
- Enolase
- Phosphoglycerate mutase
- Phosphoglycerate kinase
- Glyceraldehyde phosphate dehydrogenase
- Triose phosphate isomerase
- Aldolase
- Fructose 1, 6 Bisphosphatase
- Phosphohexose isomerase
- Glucose-6-phosphatase
