metabolism overview and glycolysis

Question 1

catabolism

Answer 1

-break down of fuels into useable forms of energy
-energy generated by oxidation of carbon to CO2 using O2
-coupled with generation of reducing equivalents

Question 2

anabolism

Answer 2

-biosynthesis of molecules from smaller molecules
-requires input of energy (ATP or NADPH)

Question 3

biochemical reactions ae commonly regulated by ______ or _______ control

Answer 3

feedback or feedforward

Question 4

rate-limiting or commitment steps?

Answer 4

-where metabolic regulation usually occurs
-rate-limiting steps: the slowest step in the pathway
-commitment steps: the first irreversible step unique to the pathway (usually has high energy substrates like ATP)

Question 5

what is a futile cycle? give one example

Answer 5

-formed by irreversible reactions in opposite directions
-activation of both reactions would waste cellular energy
-minimize energy loss, reactions only in one direction should be active at given time (glycolysis vs glucogenesis)
-liver uses between glucose and glucose 1 phosphate to maintain blood glucose levels

Question 6

regulation of metabolism

Answer 6

-transcriptional/translational regulation (slow)
-protein degradation (slow)
-allosteric regulation (fast)
-post translational modification (fast)
-compartmentation (fast)

Question 7

transcription/translational regulation

Answer 7

-slow
-induction of genes

Question 8

protein degradation

Answer 8

-slow
-ubiquitin-proteasome pathway
-lysosomal proteolysis

Question 9

post translational modification

Answer 9

-fast
-phosphorylation

Question 9

allosteric regulation

Answer 9

-activators and inhibitors
-fast

Question 10

compartmentation

Answer 10

-fast
-shuttling substrates to a compartment for biochemical reactions
-fatty acid biosynthesis in the cytosol and oxidation in the mitochrondria

Question 11

difference in metabolism between organs

Answer 11

-different organs utilize metabolic pathways to perform their functions
-organs cooperate tightly to optimize the systemic physiological responses to nutritional status, physical activity, etc

Question 11

glycolysis overview

Answer 11

-happens in the cytosol
-input: glucose
-output: 2 pyruvate
-energy harvested: 2 ATP and 2 NADH

Question 12

_______ increases the number of glucose transporters on the cell membrane

Answer 12

insulin
except on the liver

Question 13

reactions coupled with ATP hydrolysis are usually_____

Answer 13

irreversible

Question 14

glucose 6 phosphate is also used in __________ and _______

Answer 14

glycogen synthesis and pentose phosphate pathway

Question 15

the production of ______ is the commitment step of glycolysis

Answer 15

fructose 1-6 bisphosphate

Question 16

AMP as signaling molecule

Answer 16

-ATP, ADP, and AMP are maintained in equilibrium in cytosol
-[ATP]»[ADP]»[AMP]
-small decrease in [ATP] results in significant increase in [AMP]
-cells sense its energy status using AMP as signal
-AMP activated protein kinase. has a critical role in cellular energy homeostasis

Question 17

____ steps are rarely regulated

Answer 17

reversible

Question 18

enzymes keep the reactions near _____

Answer 18

equilibrium

Question 19

Fructose 1,6 bisphosphate activates pyruvate formation through

Answer 19

feedforward control
pyruvate is also used to make alanine

Question 20

pyruvate

Answer 20

-product of glycolysis
-transported to mitochondria for the conversion to acetyl CoA
-can be used to make glucose through gluconeogenesis

Question 21

glycogen synthesis and breakdown

Answer 21

-liver and muscles store excess glucose as glycogen
-glycogen synthesis and breakdown are tightly regulated
-liver regulates blood glucose levels using glycogen

Question 22

utilization of fructose

Answer 22

-fructose does not increase blood insulin levels
-requires different kinases from glycolysis
-same splitting enzyme as glycolysis is used, but fructose 1 phosphate is poor substrate for enzyme
-excess amounts will accumulate in liver, depleting ATP and phosphate, causing sever liver damage

Question 23

Which of the following metabolites cannot be a carbon source for gluconeogenesis

pyruvate
lactate
alanine
acetyl coa

Answer 23

acetyl CoA