cellular respiration (glycolysis, krebs) Flashcards
sum total of all chemical reactions in living cells
Metabolism
degrade macromolecules and other
molecules to release energy
catabolic reactions
used to synthesize macromolecules for cell growth, repair, and reproduction
anabolic reactions
Can divide metabolism into 4 groups:
carbohydrates, lipids, amino acids, nucleotides
pathways can take different forms: (3)
linear
cyclic
spiral
product of one reaction is substrate for another
e.g. glycolysis
linear
regeneration of intermediates
e.g. Krebs cycle
cyclic
same set of enzymes is used repeatedly
e.g. fatty acid synthesis, beta-
oxidation
spiral
each pathway may have branch points for ??? to enter or leave
metabolites
Reasons why metabolic reactions have many steps:
1) energy input and output can be controlled
2) enzymes can catalyze only a single step of a pathway
3) provides opportunities to establish control points, which are essential for cell function
occurs in discrete steps as it it transferred to acceptors a little at a time
energy transfer
Major Catabolic Pathways
begins with ??? of polymers (exogenous)
extracellular digestion
??? in mouth and intestine work on starch
amylase
??? starts in stomach and finished via ??? and ???
protein digestion;
pancreatic proteases and intestinal peptidases
triacylglycerols hydrolyzed to fatty acids by phospholipases
lipid digestion
absorption occurs in ???—> ???—> ???
intestine
blood
body
major catabolic pathways can also have ??? sources, such as glycogen and triacylglycerols
endogenous
catabolism yields 3 possible compounds:
1) acetyl CoA
2) nucleoside triphosphates
3) reduced coenzymes
major catabolic pathways starts with ??? (glucose catabolism), ???, ???, ???
glycolysis;
citric acid cycle;
polysaccharide mobilization;
oxidative phosphorylation
are metabolized for excretion, not energy production
nucleotides
There are several types of group transfer reactions that involve ATP:
1) phosphoryl group transfer
2) nucleotidyl-group transfer
3) thioesters
Another class of energy-rich molecules.
Energy can be donated in oxidation-reduction reactions
reduced coenzyme
§ Purpose: catabolism of glucose to provide ATPs and NADH molecules
§ Also provides building blocks for anabolic pathways.
glycolysis
glycolysis:
Electrons are transferred to oxidizing agents ??? or ???
NAD+ or FAD.
glycolysis:
glucose➡️???
??? and ??? produced
All enzymes (and reactions) are ???
pyruvate;
2 ATPs and 2 NADH;
cystolic
net reaction of glycolysis
glucose + 2ADP + 2NAD+ +2Pi
➡️
2 pyruvate + 2ATP + 2NADH +2H+ +2H2O
glycolysis can catabolize sugars other than glucose: (3)
fructose
lactose
mannose
glycolysis step 1:
Glucose + ATP → Glucose-6-phosphate + ADP + H+
hexokinase
glycolysis step 2:
Glucose-6-phosphate → Fructose-6-phosphate
glucose 6-phosphate isomerase
glycolysis step 3:
Fructose-6-phosphate + ATP → Fructose-1,6-bisphosphate + ADP + H+
phosphofructokinase-1 (PFK-1)
which steps in glycolysis requires ATP
1 and 3
glycolysis step 4:
Fructose-1,6-bisphosphate → Dihydroxyacetone phosphate + Glyceraldehyde-3-phosphate
aldolase
glycolysis step 5:
Dihydroxyacetone phosphate → Glyceraldehyde-3-phosphate
triose phosphate isomerase
which steps in glycolysis are done twice?
6-10
once for each of the 2 G3P
glycolysis step 6:
Glyceraldehyde-3-phosphate + Pi + NAD+ → 1,3-Bisphosphoglycerate + NADH + H+
glyceraldehyde 3-phosphate
dehydrogenase
glycolysis step 7:
1,3-Bisphosphoglycerate + ADP → 3-Phosphoglycerate + ATP
Phosphoglycerate kinase
which steps in glycolysis produces ATP?
7 and 10
glycolysis step 8:
3-Phosphoglycerate → 2-Phosphoglycerate
phosphoglycerate mutase
glycolysis step 9:
2-Phosphoglycerate → Phosphoenolpyruvate + H2O
enolase
glycolysis step 10:
Phosphoenolpyruvate + ADP + H → Pyruvate− + ATP
Pyruvate kinase
Under anaerobic conditions, cells must be able to regenerate ??? or ??? will stop.
NAD+;
glycolysis
NADH is usually regenerated by ???, but that requires O2.
oxidative phosphorylation
FATE OF PYRUVATE (3)
1) alcoholic fermentation
2) lactate fermentation
3) entry into citric acid cycle
There are 2 anaerobic pathways that use NADH and regenerate NAD+.
1) alcoholic fermentation
2) lactate fermentation
Conversion of pyruvate to ethanol
alcoholic fermentation
Lactate causes muscles to ache.
Also produced by bacterial fermentation of lactose.
lactate fermentation
There are three enzymes that can be regulated:
1) hexokinase
2) phosphofructokinase-1
3) pyruvate kinase
Organisms derive much of their energy from the Kreb’s Cycle, also referred to as the ???. The Kreb’s cycle is an ??? process that comprises ??? definite steps.
Tricarboxylic Acid cycle;
aerobic;
eight
In order to enter the Kreb ‘s Cycle,
pyruvate must first be transformed by ??? complex located in the mitochondria into ???
pyruvate dehydrogenase;
acetyl-coA
In the presence of ??? organisms are capable of using the Kreb’s Cycle. The reason oxygen is required is because the ??? and ???produced in the Kreb’s Cycle are able to be oxidized in the ??? thus replenishing the supply of ???
oxygen;
NADH and [FADH2] ;
electron transport chain (ETC);
NAD+ and [FAD].
net reaction for Kreb’s Cycle
Acetyl-CoA + 3NAD + FAD + GDP + Pi + 2H2O —>
2CO2 + 3NADH + FADH2 + GTP + CoA + 3H+
REGULATION OF KREB CYCLE
There are 2 enzymes that are regulated:
1) isocitrate dehydrogenase
2) a-ketoglutarate dehydrogenase
- allosterically activated by high [Ca2+] and high [ADP]
- allosterically inhibited by high [NADH]
isocitrate dehydrogenase
- allosterically activated by high [Ca2+]
- allosterically inhibited by high [NADH] and high [succinyl CoA]
a-ketoglutarate dehydrogenase
for every molecule of glucose, how many times does the Kreb’s Cycle happen?
twice,
each for every pyruvate
with oxygen, in animals, pyruvate can be converted to?
lactate
TCA cycle products
Acetyl-CoA
Citrate
Isocitrate
a-ketoglutarate
Succinyl-CoA
Succinate
Fumarate
Malate
Oxaloacetate
GTP
(Guanosine Triphosphate)
TCA Cycle net produce every Acetyl CoA
3NADH + FADH2 + ATP
TCA cycle enzymes
citrate synthase
aconitase
isocitrate dehydrogenase
a-ketoglutarate dehydrogenase
succinyl-coA synthetase
succinate dehydrogenase
fumarase
malate dehydrogenase
