Midterm #2 Flashcards
Glucose Polysaccharides
Glycogen
Starch
Cellulose
Classifications of Carbohydrates
Type of carbonyl group
number of carbons
ring size
stereochemistry
Purpose of carbohydrates
energy storage structural support molecular recognition (signaling)
Monosaccharides
glucose
galactose
mannose
fructose
Disaccharides
sucrose
lactose
maltose
Classifications of Glycoproteins
N-linked - use Asn
O-linked - use Ser or Thr
Glycoproteins
oligosaccharides + proteins
Other Roles of Carbohhydrates
Proteoglycan
ABO blood typing
Chitins
Lipopolysaccharides
Why do we metabolize?
Energy
macromolecule synthesis
prevent toxin build up
breakdown xenobiotics
Forms of energy storage
glycogen
triaglycerides
proteins
Catabolism = oxidation Anabolism = reduction
Catabolism = cofactors are reduced Anabolism = cofactors a oxidized
Reduction of Carbon Compounds
Unfavorable
Requires energy
Oxidation of Carbon Compounds
Favorable
releases energy
Common Pathway Intermediates
glyceraldehyde-3-phosphate
pyruvate
acetyl CoA
Essential micronutrients
Nutrients the human body can not make from scratch.
- vitamins
examples of essential micronutrients (vitamins) needed to make cofactors.
Niacin - NAD+
RIboflavin - FAD
ATP Synthesis
Glycolysis
Oxidative phosphorylation
ATP
Membrane impermeable
not exchangable
Short life
at rest, humans consume 40Kg or ATP/day
Coenzyme A
Substrate for acetyl CoA
A nucleotide derivative
Examples of highly favorable reactions frequently coupled to unfavourable reactions
phosphorylated compounds (ATP, glucose-1-phosphate, glycerol-3-phosphate)
Thioesters - Acetly CoA
Reduced Cofactors
electrochemical gradients.
reversible reactions
small delta G forward and reverse rates are similar reaction near equilibrium 1 enzyme for both directions small impact on overall pathway.
Irreversible reaction
large delta G
goes to products, even with few reactants.
large impact on overall pathway
Flux
Controlled by irreversible reactions
Common pathway reactions
group transfer reactions - acylation, phosphorylation, glucosylation, etc. redox elimination/rearrangement - double bond forming carbon-carbon bonding - ring structures?
Common Cofactors
NAD+/NADH
FAD/FADH2
Q/QH2
Oxidative Phosphorylation
O2 reduced to H20
NADH and FADH2 are oxidized
Keq
> 1 = products favoured
Glucose transporter
GLUT
bidirectional transport
only glucose, not any form of phosphorylated glucose.
How is glucose retained in the cell?
Phosphorylation by hexokinase, so glucose-phosphate isn’t transported out.
Glycolysis Phases
Phase 1 = energy investment. Steps 1-5
Phase 2 = ATP production. 6-10
Glycolysis Enzymes
- hexokinase
- phosphoglucose isomerase
- phosphofructokinase
- aldolase
- triose phosphate isomerase
- glyceraldehyde-3-phosphate dehyrdogenase
- phosphoglycerate kinase
- phosphoglycerate mutase
- enolase
- Pyruvate kinase
Glycolysis Intermediates
- glucose-6-phosphate
- fructose-6-phosphate
- fructose-1,6-bisphosphate
4/5. glyceraldehyde-3-phosphate + DHAP - 1,3-bisphosphoglycerate
- 3-phosphoglycerate
- 2-phosphoglycerate
- 2-phosphophenolpyruvate
- pyruvate
Which reactions are different/not reversible between glycolysis and gluconeogenesis?
1 (hexokinase)
3 (phosphofructokinase)
10 (pyruvate kinase)
reverse reaction to pyruvate kinase
pyruvate carboxylase & PEPCK
reverse reaction to phosphofructokinase
glucose-6-phosphatase
reverse reaction to kexokinase
fructose bisphosphatase
Phosphofructokinase 2
Activates phosphofructokinase 1 = activates glycolysis
inhibits fructosebisphosphotase = inhibits gluconeogenesis
Phosphofructokinase regulation
- phosphofructokinase 2 activates
- ATP inhibits
- AMP activates
- fructose-6-phosphate activates
Allosteric control
End product either activates and inhibits its reaction
compartmentation
another means of regulation. Due to location.
Vitamin associated with Coenzyme A
Vitamin B5
pantothenic acid
PDH regulation (pyruvate dehydrogenase)
PDH kinase - inactivates
PDH phosphatase - activates
Which reactions of the TCA are irreversible?
- citrate synthase
- isocitrate dehydrogenase
- alpha ketogluterate dehydrogenase
TCA Reaction 1 - Citrate synthetase
inhibited by NADH, succinyl CoA, and citrate.
Vitamin B1
NOT SURE! D:
Vitamin B2
Riboflavin
FAD/FADH2
Vitamin B3
Niacin
NADH/NAD+
Vitamin B5
pantothenic acid
where is NADH re-oxidized?
mitochandrial matrix.
Stays there for use in glycolysis
Oxidative PHosphorylation
A series of redox reactions generating a proton gradient used to fuel ATP synthesis.
How is NADH from glycolysis transported into mitochondria?
Malate-aspartate shuttle
Matrix - malate -> aspartate + NADH
Cytosol - aspartate -> malate + NAD+
* Oxaloacetate intermediate.
Complex I
NADH -> NAD+
Q -> QH2
4 protons transfered
Redox Active cofactors that help with oxidative phosphorylation (transport electrons)
Fe-S
Q
FMN
Alpha heme
Complex II
Succinate Dehydrogenase from the TCA cycle.
succinate -> fumerate
FAD -> FADH2
Q -> QH2
Reactions forming QH2
- Succinate dehydrogenase (TCA)/COmplex II (oxidative phosphorylation)
- complex I (oxidative phosphorylation)
- Fatty acid oxidation
- glycerol-3-phosphate shuttle
Complex III
QH2 -> Q
CytoC Fe3+ -> CytoC Fe2+
4 protons transfered
Complex IV
Cytochrome C oxidase complex
CytoC Fe2+ -> CytoC Fe3+
O2 -> H2O
2 protons transfered
Problem with Complex IV
Sometimes oxygen escapes/isn’t converted to H20 -> produces oxygen free radicals.
Problem with free radicals?
Can damage nucleic acids, proteins and lipids.
Efficieny of the electron transport chain
Should be able to make 7 ATP, actually make ~ 2.5 ATP.
Energy used in proton transfer.
Complex V
ATP Synthase/F1F0-ATPase requries... - ADP (ATP translocase) - Pi (symport protein - Pi and H+) in the mitochondrial matrix
1 full rotation of the F0 complex
translocates 8 protons
Which subunit of F1 ATP synthase binds ADP?
beta
Alpha/beta subunit conformations
Open
Tight
Loose
P:O
number of phosphorylated ADP per oxygen atom reduced
UCP
uncoupling proteins
- NADH is still oxidized
- electrons are transported
- oxygen is reduced to H20
- NOT ATP FORMED
- reduces liklihood of free radical formation
- generates heat
Pigments/photoreceptors
light absorbing groups in chloroplast
Chlorophyll A and B
absorb red and blue light
Reactions powered by energy release from excited chlorophyll to ground state chlorophyll
- heat
- light
- exciton transfer (excite another molecule)
- oxidized -> reduced. Chlorophyll+
When fluorescence is high…
Photosynthesis is low
Excitation of reaction centres in Photosynthesis
- Oxidizes H20 -> O2
- reduction of NADP+ -> NADPH
- transmembrane proton gradient
photosystem II
P680+ -> P680 -> P680* -> P680+ chlorophyll dimer H2O -> O2 PQ -> PQH2 4 protons transfered
Strongest organic, biological oxidizing agent known
P680+ (reduced chlorophyll dimer in photosystem II)
Cytochrome B6F
PQH2 -> PQ
PC(Cu2+) -> PC(Cu+)
4 protons tranfered
brings P700 back to ground state
Photosystem I
P700
PC(Cu+) -> (PC(Cu2+)
ferredoxin (oxidized) -> ferredoxin (reduced)
NADP+ -> NADPH
Final outcomes of the photosystems
PSII - water -> oxygen
PSI - NADP+ -> NADPH
ferredoxin
a small peripheral membrane protein used to catalyze the reduction of NADP+ -> NADPH.
NADPH
Final acceptor of the electrons removed from H20 in PSII.
Photophosphorylation
Same as ATP synthesis in mitochondria.
Dark reactions
Reactions that use the products of light-dependent reaction (NADPH, O2, ATP)
Atherosclerosis
Build up of lipoproteins in arterial walls
Purpose of lipoproteins
Transport water-insoluble lipids in hydrated environments.
Types of lipoproteins
Chylomicrons
Very Low Density Lipoproteins (VLDL)
Low Density Lipoproteins (LDL)
High Density Lipoproteins (HDL)
Triacylglycerols
Glycerol-3-phospahte + fatty Acyl CoA
Sources of substrates for triacylglycerol
Glycerol-3-phosphate - DHAP (form glycolysis or glyceroneogenesis) - Glycerol kinase in the liver. fatty acyl CoA - acyl CoA synthetase
