slides 8-13 - physiology Flashcards
what are enzymatic cofactors and coenzymes?
a non protein substance required for catalytic activity of some enzymes
examples of cofactors or coenzymes
Mg2+, Zn2+, Mn2+ . . . and
NAD+, FAD
study of metab. in vitro advantages and disadvantages:
isolated , defined and modifiable conditions, quantative results
loss of compartmentation
- doesn’t reflect the actual cell (eg running out of Pi
study of metab. in vivo advantages and disadvantages:
in cell - realistic
hard to quantify (many variables)
why do we need metabolic pathways?
multistep pathway that allows control
what is a metabolic crossroad?
most pathways lead to the same common intermediates eg (Glucose - 6 - P)
what are some key cofactor carriers?
ATP, NAD+, FAD, NADPH , CoA
outline the two stages of glycolysis:
invstment and pay out
uses: 2 ATP
then produces: 4 ATP & 2 NADH
NET=2ATP
What happens if cofactors run out?
glycolysis stops
outline how NAD+ is regenerated in aerobic vs anaerobic:
pyruvate is oxidised and NADH gives e- to O2 forming H2O and NAD+
anaerobic : Glucose oxides to pyruvate and Pyruvate is reduced to ethanol or lactic acid
what makes glycolysis central to carbohydrate breakdown?
it is the original way of making energy and leads to many other pathways essential for modern organisms
outline the main stages of control and why of glycolysis:
1 stage –> not main regulation step as glucose is needed in other pathways
3 stage : main regulatory point
10 step : not main but needed as metabolic branch point.
name the enzymes in the control stages:
Hexokinase - feedback inhibition
Phosphofructo Kinase - energy levels (AMP/ATP) + Metabolic intermediates
Pyruvate Kinase - feed forward activation
what happens when there is a high level vs low level of ATP in glycolysis?
high = PFK inactivated
Low = PFK activated
liver control in glycolysis?
yes - liver regulates blood glucose
Fructose - 2, 6-P increases when blood glucose is high
makes a feed forward and reduces inhibition by ATP
sources for metabolism:
Galactose, Fructose
Outline gluconeogenesis:
pyruvate –> glucose
liver and kidney
uses: ATP and GTP
shares steps with glycolysis but not all because it is Anabolic pathway
what is generated from the hydrolysis of fructose -1, 6 bisP and glucose - 6- Pi?
not ATP (not regenerated) –> futile cycle
therefore tight regulation occurs –> PFK and Fructose -1, 6- bisphosphatase = oppositely regulates
what are the starting materials for gluconogenesis?
Lactate , amino acids, and glycerol –> pyruvate oxaloacitate dihydroxyacetone
– triacylglycerides (fat) –> glycerol but only one not considered a source
what is the pentose phosphate pathway?
converts glucose to pentoses releasing NADPH
also produces ribose - 5 P
key stages of PPP:
oxidative stage (2 NADPH) and non oxidative stage( ribose -5-P+ glycolytic intermediates)
how is PPP controlled?
by NADP+ availability (the substrate)
steps for PPP:
step 1 : glucose 6 P
step 2 :gluconolactonase
step 3 : 6-P gluconate DH
what kind of pathway is the PPP?
cyclic - completely oxidises glucose to CO2
how many different modes does the PPP cycle have?
- No NADPH (ribose)
- (NADPH + ribose)
- NO Ribose (NADPH)
4 NADPH and ATP
what is the ^G of glucose –> co2 and h20?
-2.9x10^3
what was the sparker effect?
the effect is that of an organic acid on the use of O2. the more O2, the more
inhibitors of the Krebs cycle?
malonate (competitive)
conversion of pyruvate to acetal CoA steps
irreversible
pyruvate + coenzyme a + NAD+
what are the components of the pyruvatedehydrogenase complex and function
E1, decarboxylates pyruvate
E2, transfers to CoA
E3, regenerates lipoamide
what are multi enzyme complexes?
non covalent bonded enzymes that catalyse 2+ sequential steps
citric acid cycle regulation points:
- pyruvate to acetal Coa
- acetal Coa to citrate
- isocitrate to alpha ketoglutarate
- alpha ketoglutarate to succinyl CoA
what reaction occurs to replenish oxaloacitate if it is pulled out of citric acid cycle?
carboxylation of pyruvate
explain the electron transport chain in oxidative phosphorylation:
free energy release
role of the complex 1, 3, and 4
1, 2 ,3 4 complexes and function of each should be on paper
proton motive force:
delta p –> each proton moving back = -22kj/mol
3 H+ are needed for 1 ATP
what does complex V do and why is it coupled?
F0 = proton pump
F1 = ATP synthesis (condensation?)
not coupled= F0 pumps H+ but does not make ATP and if just F1, it hydrolyses ATP
how does ATP synthase work?
F0 rotates, Y rotates ADP and P are trapped and T site
what are the components of beta
O: binds and release of ADP and P
Y rotates
L: ADP and P bound
y rotates
T: ATP formed
y rotates
O: atp leaves
what moves the electrons from NADH into the mitochondria from glycolysis?
glycerol phosphate shuttle = carried by FADH2 into complex 2 therefore only 6 H+ pumped total
malate shuttle =complex and goes to complex 1
how are the nucleotide carriers used? / how does the ADP and P end up in the matrix where they are needed?
P-OH antiporter
ATP-ADP antiporter
equation to calculate the energy of a photon?
e=HC/lamda
what was the hill reaction?
isolated chloroplast was illuminated - primary event in photosynthesis occurred
explain the light harvesting complex:
photons hit chlorophylls and auxiliary pigments
electron gets excited
transfered to reaction centre
explain the reaction centre:
photons end up at reaction centre chlorophylls
energy used for charge separation
the resulting e- can be given to other molecules
how is light energy converted?
by photosystem 1 and 2
