Metabolism Flashcards
Regulatory enzymes of Glycolysis
Hexokinase (Glucose → G-6P)- ATP in
PFK (F6P → F 1,6-bisphosphate)- ATP in
Pyruvate kinase (PEP → Pyruvate)- ADP in
Rate-limiting step of glycolysis
PFK catalyzes F6P → F 1,6-bisphosphate
- F6P is phosphorylated using ATP
Net Yield of Glycolysis
2 ATP, 2 NADH, 2 pyruvate
Oxidoreductases
catalyze redox reactions that transfer electrons
Transferases
move a functional group from one molecule to another
Hydrolase
catalyze cleavage with the addition of water
Lyase
catalyze cleavage without the addition of water or transfer of electrons
- synthase is the opposite
Isomerase
catalyze the interconversion of isomers, including both constitutional isomers and stereoisomers
Ligase
join two large biomolecules (often the same type)
NADH vs NADPH
NADPH is used in synthesis pathways (like PPP): fatty acid cholesterol neurotransmitter Nucleotide
It is similar to NADH, except: additional phosphate group enables binding discrimination can be reduced more NADH is used in all other metabolic pathways
Both:
reductive agent
protease
protein that hydrolyzes (cleaves) another protein; hydrolyzes peptide bonds
lipase
enzyme that hydrolyzes fats
kinase
transfers a phosphate group to a molecule from a high energy carrier, such as ATP
polymerase
synthesizes long chains of polymers or nucleic acids
phosphatase
removes a phosphate group from a molecule (“undoes” a kinase)
phosphorylase
transfers a phosphate group to a molecule from inorganic phosphate
ATP synthase
large protein complex that synthesizes ATP from ADP +Pi
exonuclease
cutting a nucleic acid chain at the end
endonuclease
will cut a polynucleotide acid chain in the middle of the chain, at a particular sequence
- ex) repair enzymes and restriction enzymes
caspases
part of the protease family; responsible for carrying out the events of apoptosis; consist of initiator caspases, which respond to extracellular and intracellular signals, which then activate the effector caspases, which cleave a variety of cellular proteins to trigger apoptosis. upon this, there is an amplification cascade. (usually inactive in zymogen form)
Energy input phase of glycolysis
2 phosphate groups from 2 ATP are added to glucose, trapping it inside the cell and split it into DHAP and G3P
Energy output phase
Energy created in the second half of glycolysis
Substrate level phosphorylation
The direct transfer of a phosphate group from a reactive intermediate onto ADP or GDP by kinase enzyme
When glucose is abundant, it comes from the _______________. When it is limited, it comes from the _________________________.
Intestines ; liver
Ammonia goes into the _____ cycle and the carbon chain acts as a substrate for the ________ cycle
Urea cycle—>urine ; citric acid cycle
Why can muscles release glucose for other organs to use?
They do not have the necessary phosphatase to release glucose from the cell.
glycogen synthase
creates alpha 1,4 glycosidic links between glucose molecules (makes glycogen)
- activated by insulin in liver and muscle
Branching enzyme
moves a block of oligoglucose from one chain and adds it to the growing glycogen as a new branch at an alpha 1,6 glycosidic link
Glycogen phosphorylase
removes a single glucose 1-phosphate molecules by breaking alpha 1,4 glycosidic links
- activated by glucagon (liver) to prevent low blood sugar
- activated by epinephrine and AMP (exercising skeletal muscle) to provide glucose for muscle
Debranching enzyme
moves a block of oligoglucose from one branch and connects it to the chain using an alpha 1,4 glycosidic link. it also removes the branch points (an alpha 1,6 glycosidic link)- releases a free glucose
control of pyruvate dehydrogenase
pyruvate dehydrogenase converts pyruvate to acetyl-CoA
- stimulated by insulin
- inhibited by acetyl-coA
When oxygen or mitochondria are absent, NADH from gylcolysis is oxidized by ___.
cytoplasmic lactate dehydrogenase
- in RBCs, skeletal muscle during short, intense bursts of exercise, and oxygen deprived cells
pentose phosphate pathway
- aka the HMP shunt
- occurs in cytoplasm of most cells
- generates NADPH and ribose sugars for biosynthesis
rate limiting enzyme of PPP
glucose-6-phosphate-dehydrogenase
- G-6-PD is activated by NADP+ and insulin
- inhibited by NADPH
dehydrogenases
which remove one or more hydrogen atoms from their substrates
- cofactors are NAD+ and FAD
NAD+ and FAD
- serve as oxidizing agents, accepting a pair of electrons, along with one or more protons, to switch to their reduced forms
- NAD+ accepts two electrons and one H+ to become NADH
- FAD accepts two electrons and two H+ to become FADH2
- NAD+ is the primary electron carrier used during cellular respiration, with FAD participating in just one (or two sometimes two) reactions
Water soluble electron carriers
NADH, FADH2, NADPH
Fat soluble electron carriers
membrane proteins in the electron transport chain (FMN, CoQ, iron-sulfur complexes, cytochromes)
TOTAL net ATP produced per glucose
theoretically 38 (2 from glycolysis, 2 from citric acid cycle, 24 from ETC), actually ~30
Glycolysis product
2 Pyruvate, 2 NADH, and 2 ATP
Regulators of glycolysis
- inhibited by ATP.
Feeder pathways: breakdown of glycogen and starch (in plants) forms glucose units, which feeds into glycolysis
Inhibitor of glycolysis
ATP.
Feeder pathways: breakdown of glycogen and starch (in plants) forms glucose units, which feeds into glycolysis
Steps of aerobic metabolism (needs oxygen)
Glycolysis
Oxidative decarboxylation
Krebs cycle
Electron transport chain.
Net: 6 CO2, 6 H2O, and up to 30 ATP from each molecule of glucose
germ layers and what they produce
ectoderm. Its the most superficial, so think if skin.
Mesoderm, bone and muscles.
Endoderm, gut and reproductive trac
Steps of anaerobic metabolism (don’t need oxygen)
Glycolysis
Alcohol or lactic acid fermentation
Net: 2 ATP, Lactic Acid (animals) or EtOH (plants)
