G: Pathways Flashcards
catabolism pathways:
-Glycolysis:
– Embden-Meyerhof-*Parnas
– Entner-Doudoroff
– Pentose-Phosphate
-Fermentation
-Respiration:
– Aerobic
– Anaerobic
glycolysis:
purpose?
where?
reactants?
products?
-purpose: reactions to break down glucose for energy
-where: cytoplasm of cells
-reactants: 1 glucose, 2 ATP, 2 NAD+
-products: 2 pyruvate , 4 ATP , 2 NADH
-glucose has 6C –> pyruvate has 3Cs (2x) aka pyruvic acid
additional notes on glycoysis:
generates?
uses up? into?
rapid as?
3 stages?
-Generates ATP
–Uses up NAD+ (into NADH)
–Rapid as Oxygen-free [Anaerobic]
– 3 Stages:
* Energy-investment stage (investing of 2 ATP to make more)
* Lysis stage (breaking of 6C to 2 x 3C)
* Energy-conserving stage (oxidation of 3C molecules to yield
4 ATP): Enzyme requires Mg2+ (Co-factor) for SLP
two options after glycolysis:
fermentation
respiration
fermentation:
purpose?
where?
reactants?
products?
-purpose: break down of toxic pyruvic acid (in the absence of oxygen - anaerobic)
-where: cytoplasm of cells
-reactants: 1 pyruvate , 1 NADH
-products: 1 less toxic compound (ethanol or lactate) , 1 NAD+ , 1 CO2
-takes 3C pyruvate into 2C less toxic compound and 1C CO2
fermentation:
Good News
– NAD+ recycled
– CO2 diffuses away
– Compounds produced are weaker than Pyruvate, but still toxic
applying fermentation:
Eukaryotes
–Yeast:
* Bread
* Beer and wine
– Humans:
* Muscle cells without oxygen
– → lactic acid build up – Lock up
we start to make energy through?
-in the absence of O2?
glycolysis to break down sugar and make ATP
-in the absence of O2 (anaerobic: ferment, to rid ourselves of toxic Pyruvate, (Aerobically) Otherwise we can RESPIRE!
respiration: 2-step process
-Two-Step process to complete processing of energy sources:
– Krebs Cycle
– Electron Transport Chain
Krebs Cycle:
purpose?
where?
reactants?
purpose?
purpose: break down of pyruvic acid
-where: mitochondria of eukaryotic cells, plasma membrane of prokaryotic cells
-reactants: 1 pyruvate , 4 NAD+ , 1 FAD+
-products: 4 NADH , 1 FADH2 , 3 CO2 , 1 ATP
krebs cycle aka
the citric acid cycle or TCA cycle
krebs cycle steps:
- stripping off the carbons from pyruvate over and over to get 3 CO2 then ATP
- use of 4 NADHs and 1 FAD used
- producing GTP / energy carrier
- do this two times and you’ll get 8 NADHs and 2 FADs and 6 CO2
good news and bad news of respiration Krebs cycle:
what has been released?
extra?
more?
Good News:
– All carbons from Glucose have been released as
less toxic waste product (CO2 diffuses away)
– Extra ATP
Bad News:
– More NADH and FADH2
ETC stands for
electron transport chain
respiration pt. 2: ETC
purpose?
where?
condition?
reactants?
products?
-purpose: Recycling of used up NAD and FAD
-Where: Mitochondria of Eukaryotic Cells, P.M. of Prokaryotic Cells
-Condition: Collector of electrons (O2)
-reactants: NADH , FADH2
-products: NAD+ , FAD +2
respiration pt. 2: ETLP (Electron Transport Level Phosphorylation)
reactants & reactions:
-Energy is stored in the electrons traveling with
NADH/H+. These electrons must end up somewhere
– TEA → O2
–Some of the energy that is given off is used to
pump H+ across the membrane to make a H+ gradient
–The energy stored in this gradient can be harvested later
respiration pt. 2
H+ are pumped out of membrane
– There is a concentration gradient with more H+
outside the cristae than inside the cristae
ATP synthase allows two H+ back across the membrane to the inside of the cristae at a time.
–When these two H+ come back across the membrane, they are traveling down the concentration gradient, which releases energy
good news of respiration
Water isn’t toxic
* NADH/H+ is recycled
* FADH2 is recycled
* More ATP is made by:
– Each NADH/H+ recycled makes 3 ATP
– Each FADH2 recycled makes 2 ATP
summary on respiration:
ETC occurs via a chain of closely-linked enzymes
– Protein carriers (Cytochromes)
– Protein pumps
ETC occurs in Mitochondria of EUKs (inner membrane –cristae)
–PROKs do not have Mitochondria, therefore use cytoplasmic membrane
Arrangement of enzymes varies from EUKs to PROKs
– Vary amongst PROKs
–Cytochromes) Neisseria and Pseudomonas spp. vs. Escherichia and Salmonella spp.
-May vary by temperature (E. coli)
- ETC changes on the Terminal Electron Acceptor [TEA] chemical
– Most EUKs use Oxygen (Aerobic)
– (Anaerobic) PROKs can use sulfur (desulfovibrio spp.), nitrate (pseudomonas and bacilli spp.), and carbonate (methanogens
what are the two alternatives to glycolysis
pentose phosphate pathway
entner-doudoroff pathway
pentose-phosphate pathway:
aka?
production of?
less?
-aka phosphogluconate pathway, or hexose
monophosphate shunt
-Production of Precursor Metabolites from/for Pentoses:
– Ribulose
– Xylulose
– Ribose
- Less energy than Glycolysis
–BUT, allow the production of nucleotides and amino acids
–Provide precursors to build glucose in anabolism, as well as produce NADPH
entner-doudoroff pathway:
-Reduced ATP production
-Yields precursor metabolites and NADPH
-Primarily* found in PROKs
– Gram-negative: Rhizobium, Azotobacter, Agrobacterium spp., Pseudomonas aeruginosa
–Gram-positive: Enterococcus faecalis
