Unit 2 Chapter 9: Cell Respiration + Photosynthesis Flashcards
What is the first step in a metabolic pathway
almost always a multisubunit enzyme negatively regulated by cooperative allostery
How are metabolic pathways regulated
negative feedback loops/feedback inhibition
What is phosphorylation
the addition of a phosphate group to a substrate
-exergonic because ADP and phosphate group have much less pot. E than they did in ATP
What is an activated substrate
- phosphorylated compound
- contain a phosphate group and have high free E
What drives the formation of ATP
redox reactions
What is NADH
an electron carrier that readily donates electrons to other molecules
-has reducing power
What is the change in free energy that occurs during glucose oxidation used for
synthesizing ATP from ADP and a phosphate group
What is the structure of ATP
3 phosphate groups (high pot.E), adenine and ribose
What is glycolysis
- occurs in the cytosol
- exergonic
- the breakdown of glucose into 2, 3-C pyruvates (occurs twice); 2 ATP made from ADP and 1 NAD+ is reduced to form NADH
steps:
1. starts by using 2 ATP(which are reduced to ADP), glucose phosphorylated to form glucose-6-phosphate by hexokinase, then phosphohexoisomerase rearranges it to become fructose-6-phosphate, a second phosphate is added to form fructose-1,6,biphosphate (catalyzed by phosphofructokinase), then G3P is made
- 2 NAD+ are reduced to NADH, 4 ATP produced (net=2) (phosphate group transferred from phosphorylated substrate to ADP which oxidizes it into ATP), 2 pyruvates are produced
What is pyruvate oxidation
- in eukaryotes occurs in pyruvate dehydrogenase in mitochondrial matrix
- pyruvate form acetyl coA by reacting with CoA (coenzymeA), one of the carbons from the pyruvate is oxidized to form CO2and one more NADH is made (from NAD+)
What is the citric acid cycle
- occurs in mitochondrial matrix (in eukaryotes), acetyl coA is oxidized into 2 molecs of CO2, 1 more ATP and 3 NADH are made, 1 FAD is reduced to form FADH2
- cycles twice for each glucose
What is the ETC
- electron transport chain
- occurs in inner mitochondrial membrane
- electrons from NADH and FADH2 move through a series of proteins, doing work to release H+ and create a proton gradient
- flow of protons back across the membrane through ATP synthase = prod. of ATP from ADP and phosphate group (oxidative phosphorylation)
- molecules pass from protein with lower electroneg. to one with higher electroneg. via redox rns
- potential energy decreases with every rxn
- NADH donates electrons to complex 1, FADH2 donates them to complex 2
- at complex 3 electrons are passed from coenzyme Q to cytochrome c
- Q also carries a proton across the membrane
What is the diff. between cellular resp and fermentation
cell resp:
- aerobic
- complete ox.
- waste=H2O and CO2
- 29 ATP made(net)
ferment:
- anaerobic
- incomplete ox
- waste=org. compounds
- 2 ATP made(net)
What is the general rule of thumb about oxidation
it decreases the number of C-H bonds
What is substrate level phosphorylation
enzyme-catalyzed reactions that result in ATP production (energy comes from phosphorylated substrate)
How does feedback inhibition regulate glycolysis
-phosphofructokinase has 2 binding spots for ATP, one at the active site and one at the regulatory site, if ATP levels are high then the enzyme will bind to both; when it binds to the regulatory site the enzyme changes shape which lowers the reaction rate at the active site. Therefore ATP acts like an allosteric regulator in this case.
What happens to pyruvate oxidation when there is a lot of ATP
it is shut down (when pyruvate dehydrogenase become phosphorylated and changes shape)
-phosphorylation increases when there is a lot of acetly coA and NADH
What happens to pyruvate oxidation when there are high amounts of NAD+,CoA
these indicate low ATP, so it speeds up pyruvate ox.
Pyruvate ox is run by positive or negative control?
both (high amounts inhibit, low amounts stimulate)
What is energy produced from pyruvate ox. used for
production of NADH
How is the citric acid cycle regulated
- speeds up when low ATP
- slows when high ATP
- enzyme that converts acetyl coA to citrate is shut down when ATP binds to it
- NADH binds to another enzymes active site later (inhibition) (1st dehydrogenase)
- even later, ATP binds to an allosteric regulatory site
What is energy produced from citric acid cycle used for
production of NADH, FADH2, ATP/GTP
For each molecule of glucose what does the the cell produce from gylcolysis, pryruvate ox and citric cylce
6 CO2, 10NADH, 2 FADH2, 4 ATP
What is the final electron acceptor in the ETC and what does it produce
oxygen, produces H2O
Why does hexokinase add a phosphate group to glucose to make glucose-6-phosphate
- adds a neg. charge which traps it in the cell
- remove more glucose from cytoplasm to allow more to enter
Why does phosphohexoisomerase rearrange glucose-6-phosphate to make fructose-6phosphate
to create symmetry in the 6-C sugar to prepare for break up into two 3-C pyruvates
Does the citric acid cycle directly require oxygen
not directly, but the amount of NADH generated can only be oxidized with O2 so yes it needs to be present
What is chemiosmosis
the production of ATP via a proton gradient
Can ATP be produced without the ETC
yes, it really only depends on the flow of protons back into the membrane
How many protons make 1 ATP
about 3
How is the ETC regulated
by H+ gradient, low gradient = faster electron transport
What is fermentation
- anaerobic resp
- occurs when no oxygen is present
- regenerates NAD+ from stockpiles of NADH
- NAD+ used for glycolysis
- pyruvate accepts electrons from NADH
Difference between lactic acid and ethanol fermentatin
lactic: pyruvate accepts electrons directly from NADH and makes lactate
ethanol: pyruvate is converted to acetylaldehyde and 2CO2 are produced; acetylaldehyde accepts electrons from NADH, makes ethanol
Can pyruvate ox, , the citric acid cycle and ETC occur without oxygen
yes, many bacterial and archaeal species rely on electron acceptors other than O2 and donors other than glucose
What happens if there aren’t enough food molecules in the body to be broken down
stored carbs used first, then fats, then proteins
Where are carbs, fats, proteins used in catabolic pathways
carbs: sugars into glucose and then glycolysis
fats: glycerol into G3P in glycolysis+fatty acids into Acetyl CoA in citric
proteins: amino acids into pyruvate, acetyl CoA into citric
Where are glucose, glycolysis, pyruvate, acetyl coA and products from citric cycle used in anabolic pathways
glucose; glycogen of starch
glycolysis: pathway for synthesis of RNA and DNA
pyruvate: lactate used to make glucose
acetyl CoA into fatty acids into phospholipids and fats
products from citric acid: substrates for amino acid synthesis
