BSCI330 cellular energetics Flashcards
what are catabolic reactions
taking big molecules and breaking them down into small molecules (anabolic is reverse)
how is glucose catabolyzed
via glycolysis in cytosol and citric acid cycle in mitochondria
what is cellular metabolism
process by which cells transfer energy from one source to another to do work
where does cellular metabolism energy come from
chemical breakdown (catabolism) of nutrients
what does it mean when something is oxidized
electrons are removed
what is reduction
opposite of oxidation - addition of electrons
why do enzymes reduce activation energy
to avoid the release of large quantities of heat
how do enzymes allow energetically unfavorable reactions to occur
by coupling them with energetically favorable reactions
what are the two types of coupling reactions
catabolism - energetically favorable
anabolism - energetically unfavorable
both reactions are coupled for ATP
what happens in glycolysis
in cytosol - one molecule of glucose is converted to two molecules of pyruvate with the net production of 2 ATP and 2 NADH molecules (“reducing power”)
energetically unfavorable
what are the three phases of glycolysis
investment: 2 ATP are spent to activate glucose
cleavage: glucose is split into 2 3-carbon sugars
energy generation: 4 ATP molecules are generated
what does glycolysis yield
2 ATP molecules/glucose molecule. further metabolism of pyruvate will generate more
also yields 2 NADH molecules. in the presence of O2, they can be oxidized back to NAD+, regenerating the cofactor required for glycolysis
why must cells use fermentation
in the absence of O2, cells must use fermentation to oxidize NADH or they will run out of NAD+ and be unable to do glycolysis
what are the two modes of fermentation
first leads to excretion of alcohol and CO2, second leads to excretion of lactate
what are the two oxidation steps of pyruvate that can occur with oxygen
citric acid cycle (aka Krebs): matrix
electron transport chain: inner mitochondrial membrane
what does the Citric Acid Cycle begin with
the transport of pyruvate into the mitochondrial matrix, where it’s oxidized to form Acetyl CoA plus carbon dioxide
how is citrate formed in the citric acid cycle
the 2-carbon acetyl group is added to oxaloacetate
how is CO2 generated in the citric acid cycle
a series of steps rearrange the bonds and oxidize citrate to generate CO2, reducing power (NADH/FADH2) and GTP
what is the net result of the citric acid cycle
one turn of the cycle produces 3 NADH, 1 GTP, 1 FADH2, and releases 2 CO2 molecules
the citric acid cycle generates 6 NADH and 2 FADH2 per glucose molecule (add that to the 2 NADH from glycolysis)
what do proton pumps do
create a proton gradient across the inner mitochondrial membrane
what does the krebs cycle generate
4 ATP
what are the steps of the krebs cycle to generate ATP
stage 1: electron transport drives pump that pumps protons across membrane
stage 2: protein gradient is harnessed by ATP synthase to make ATP
the energy of the proton gradient is used by the F-type proton pump (aka ATP synthase) to convert ADP to ATP
what does photosynthesis do
uses light energy to generate chemical energy (ATP) and reducing power (NADPH) to allow carbon dioxide to be fixed into organic molecules
what is photosynthesis
synthesis of simple sugars from CO2 and H2O
