Respiration and Lipid Metabolism - 11 Flashcards
Define aerobic respiration
a biological process which organic compounds are oxidized in a slow and controlled manner to make energy from carbohydrates. The released energy is stored in ATP to be used later.
Sucrose respiration is the reversal of what process
photosynthetic process
(instead uses sugar and water to make carbon dioxide and H+ and oxygen)
what are the 4 main processes of respiration
- glycolysis
- oxidative pentose phosphate pathway
- TCA cycle
- oxidative phosphorylation (ETC and ATP synthesis)
Glycolysis starts with _____ and splits it by what two pathways and explain each with their products
sucrose
1. Invertases = hydrolyzes sucrose in cell wall, vacuole and cytosol to split and produce 1 glucose and 1fructose. Which then creates 2 ATP by enzyme hexokinase turning into fructose-6-phosphate or glucose-6-phosphate.
2. sucrose synthase = combines sucrose with UDP to produce 1 fructose and 1 UDP-glucose in cytosol. UDP-glucose then converted to UTP and glucose-6-phosphate.
Explain metabolic redundancy
that invertases and sucrose synthatase pathways both exist with similar function and can replace each other without clear loss of function
After creates fructose-6-P and 2 glucose-6-P turns into ____ through what 3 catalytic reactions
then turns into triose phosphates
turns into fructose 1,6-bisphosphate
reactions:
1. ATP-dependent phosphofructokinase
2. fructose 1,6-bisphosphate phosphotase
both irreversible
3. PPi-dependent phosphofructokinase
reversible
Once the triose phosphate (glyceraldehyde 3-phosphate) is created, it is then converted to produce ____ by what enzyme
then what enzyme makes ATP
1,3-bisphosphoglycerate
3-phosphate dehydrogenase allows phosphorylation of G-3-P into 1,3-bi
phospoglycerate kinase
For every sucrose entering glycolysis pathway, how many ATP are generated
4
What happens in next 2 steps after it becomes 1,3-bisphosphoglycerate and what is produced
phosphate group is transferred, water molecule is removed to yield phosphoenolpyruvate (PEP)
What are the 2 alternative pathways for metabolizing PEP
- PEP carboxylase forms oxaloacetate, then reduced to form malate (and NADPH)
- pyruvate kinase produces pyruvate and yields ATP
What process occurs when molecular oxygen is unavailable
glycolysis can be main source of energy through fermentation to reduce pyruvate to regenerate NAD+ for glycolytic ATP production
glycolysis occurs in
cytosol!
Define gluconeogenesis
synthesis of sugars through the reversal of glycolysis, using the breakdown of lipids or proteins instead of carbohydrates. important for seed germination
What additional enzyme is in gluconeogenesis
fructose 1,6-bisphosphate phosphatase
Why is gluconeogenesis either reversible or irreversible
irreversible because it is catalyzed by ATP-dependent phosphofructokinase
Function of the oxidative pentose phosphate pathway (OPPP)
it oxidizes sugars just like glycolytic pathway, an alternative route
where does OPPP occur
cytosol and plastids
Explain first 2 reactions in OPPP
glucose-6-phosphate into ribulose 5-phosphate with the loss of 1 CO2 and generation of 2 NADPH
Explain remaining reactions of OPPP after it is in ribulose 5-phosphate form
converts into glycolytic intermediates of glyceraldehyde 3-phosphate and fructose-6-phosphate
can be further metabolized into pyruvate by glycolysis
For every 6 glucose 6-phosphate molecules entering OPPP, how many NADPH are formed and regenerated
12 formed
5 regenerated
What percentage of glucose breakdown does OPPP contribute
10-25%, rest from glycolysis
What are the 3 roles that OPPP plays in plant metabolism
- generates NADPH in cytosol
- generates NADPH in plastids (lipid biosynthesis and N assimilation)
- generates supply of substrates for biosynthetic processes (aromatic AAs, lignin, flavonoids)
Where does TCA cycle take place
mitochondrial matrix
Where does pyruvate need to move through in order to reach the TCA cycle
after glycolysis transported through inner mitochondrial membrane barrier by specific transport proteins to mitochondrial matrix
First step of TCA and what are the products
start is pyruvate decarboxylated in oxidation reaction by pyruvate hydrogenase to give acetyl-CoA (cofactor coenzyme A and pyruvate), NADH, and CO2
Second and third steps in TCA
citrate synthase combine acetyl-CoA with oxaloacetate to give citrate
citrate to isocitrate by enzyme aconitase
Where does the energy conserved in synthesis of ATP come from in TCA
large amount of free energy comes from thioester bond of succinyl-CoA is conserved in synthesis of ATP
after succinyl-CoA into succinate, what is the next step
succinate to fumarate by succinate dehydrogenase and also makes 1 FAD
What are the final 2 steps of TCA cycle
fumarate forms malate, malate is then oxidized by malate dehydrogenase to regenerate oxaloacetate and produces another NADH.
What product is generated in order to continue the TCA cycle
oxaloacetate
As 1 molecule of pyruvate enters TCA cycle, what is produced as biproducts
3 molecules of CO2, and free energy released is conserved to form 4 NADH, 1 FADH2, and 1 ATP
How does plant tissues use malate
they store malate in their vacuoles and the degradation of malate is important in regulating levels of organic acids in cells
Instead of malate being degraded, what else is malate used for
malate can be produced via the PEP carboxylase which can replace TCA cycle intermediates that were used in biosynthesis, known as anapleurotic
ATP is important because? and where do we generate more of it from
it is the energy carrier used by cells to drive life processes, and the energy conserved in the TCA in the form of NADH and FADH2 must be converted to ATP for useful work
Define oxidative phosphorylation
occurs in the inner mitochondrial membrane and is the process of reducing oxygen to generate ATP
How are the individual electron transport proteins organized
organized into 4 transmembrane multiprotein complexes (I through IV) all localized in the inner mitochondrial membrane
