Unit 4 Flashcards
Where does glycolysis occur in a eukaryotic cell?
Cytoplasm
Where does the TCA (or Kreb cycle) occur in a eukaryotic cell?
Mitochondrial matrix
Where does the electron transport chain occur in the eukaryotic cell?
Mitochondrial inner membrane
Glycolysis:
Breaks down glucose (oxidation) into pyruvate to make energy (ATP)
TCA (or Krebs):
Releases energy from acetyl-CoA through a series of reactions that yields energy as NADH, FADH2, and ATP
Substrate-level phosphorylation:
Generates ATP, by direct transfer of phosphate from a metabolic compound to ADP
Photophosphorylation:
The light-dependent reaction of photosynthesis
Oxidative phosphorylation:
The ETC transfers electrons from an organic compound to oxygen
Fermentation:
Lactic acid and ethanol are the end-products of this pathway when pyruvate accepts electrons
What processes does photosynthesis involve?
Light-dependent photophosphorylation
&
Calvin-Benson cycle
What is the Calvin-Benson cycle?
aka Calvin cycle or the light-independent reactions is the part of photosynthesis where plants synthesize glucose from CO₂ using ATP and NADPH produced during the light-dependent reactions
Takes place in the stroma of chloroplasts and doesn’t require light to proceed
This cycle involves three main stages:
1. Carbon fixation: CO₂ is attached to a 5-carbon molecule (RuBP).
2. Reduction phase: The resulting molecules are converted into G3P (glyceraldehyde-3-phosphate), a sugar precursor.
3. Regeneration of RuBP: Some G3P molecules are used to regenerate RuBP, allowing the cycle to continue
Glycolysis yields energy in which form?
NADH and ATP
What are the steps in the Energy Investment phase in glycolysis (1-5)
- Glucose Phosphorylation
- Glucose → G6P
- Enzyme: Hexokinase- 1 ATP is used.
- Isomerization
- G6P → Fructose6P
- Enzyme: Phosphoglucose isomerase - Second Phosphorylation
- F6P → Fructose-1,6-bisphosphate (F1,6BP)
- Enzyme: Phosphofructokinase-1 (PFK-1)- 1 ATP is used.
- Cleavage (Step for which glycolysis is named)
- F1, 6BP → G3P and Dihydroxyacetone phosphate (DHAP)
- Enzyme: Aldolase - Isomerization of DHAP
- DHAP → Glyceraldehyde-3-phosphate (G3P) Enzyme: Triose phosphate isomerase
What are the steps in the Energy Payoff phase in glycolysis (6-10)
- Oxidation and Phosphorylation
- Glyceraldehyde-3-phosphate (G3P) → 1,3-bisphosphoglycerate (1,3-BPG)
- Enzyme: Glyceraldehyde-3-phosphate dehydrogenase
- NAD+ is reduced to NADH.
- First ATP Generation
- 1,3-bisphosphoglycerate → 3-phosphoglycerate
- Enzyme: Phosphoglycerate kinase
- 1 ATP is produced per molecule of G3P.
- Phosphate Shift
- 3-phosphoglycerate → 2-phosphoglycerate
- Enzyme: Phosphoglycerate mutase
- Dehydration
- 2-phosphoglycerate → Phosphoenolpyruvate (PEP)
- Enzyme: Enolase
- Water is removed.
- Second ATP Generation
- Phosphoenolpyruvate (PEP) → Pyruvate
- Enzyme: Pyruvate kinase
- 1 ATP is produced per molecule of PEP.
Which step is the step for which glycolysis is named?
4th (Cleavage)
What is meant by substrate-level phosphorylation?
Production of ATP by transferring phosphates directly from metabolic products to ADP
What is the driving force of energy production in steps 6 and 7?
The oxidation of three-carbon compounds
How much net ATP is produced during glycolysis?
2 ATP
Which of the following is needed as a reactant for the first step of the citric acid cycle?
Oxaloacetic acid
Where does the energy come from to power the formation of GTP?
Succinyl CoA
Which step of the Krebs cycle involves the release of carbon dioxide?
The third and fourth steps
What are the steps of the Krebs cycle? (8)
Krebs Cycle Steps:
- Condensation
- Reactants: Acetyl CoA + Oxaloacetate
- Product: Citrate (citric acid)
- Enzyme: Citrate synthase
- Note: Acetyl CoA donates a 2-carbon acetyl group, and oxaloacetate is regenerated.
- Isomerization
- Reactant: Citrate
- Product: Isocitrate
- Enzyme: Aconitase
- Note: Citrate is rearranged into its isomer, isocitrate.
- First Decarboxylation
- Reactant: Isocitrate
- Products: α-Ketoglutarate + CO₂
- Enzyme: Isocitrate dehydrogenase
- Note: NAD⁺ is reduced to NADH.
- Second Decarboxylation
- Reactant: α-Ketoglutarate
- Products: Succinyl CoA + CO₂
- Enzyme: α-Ketoglutarate dehydrogenase
- Note: Another NAD⁺ is reduced to NADH.
- Substrate-Level Phosphorylation
- Reactant: Succinyl CoA
- Product: Succinate + GTP (or ATP)
- Enzyme: Succinyl-CoA synthetase
- Note: The high-energy thioester bond in succinyl CoA is used to generate GTP.
- Oxidation
- Reactant: Succinate
- Product: Fumarate
- Enzyme: Succinate dehydrogenase
- Note: FAD is reduced to FADH₂.
- Hydration
- Reactant: Fumarate
- Product: Malate
- Enzyme: Fumarase
- Note: Water is added to fumarate.
- Second Oxidation
- Reactant: Malate
- Product: Oxaloacetate
- Enzyme: Malate dehydrogenase
- Note: NAD⁺ is reduced to NADH, and oxaloacetate is regenerated for the cycle to continue
How many molecules of ATP can be generated from 1 molecule of NADH?
3
Which step(s) of the Krebs cycle does (do) not produce any usable energy?
2nd (Isomerization)
&
7th (Hydration)
Why does FADH2 yield less ATP than NADH?
FADH2 electrons enter the ETC at a lower energy level
What can be used as a final electron acceptor for aerobic respiration?
Molecular oxygen
What is one difference between cytochromes and ubiquinones?
Cytochromes are made of protein; Ubiquinones are not
How does the proton gradient help ATP synthase to make ATP?
Protons move from outside the membrane to inside the membrane.
Iron is considered an essential element for many bacteria. Based on the steps of the electron transport chain, how would lack of iron affect energy production of a bacterium?
Lack of iron -> lack of heme -> lower amounts of functioning cytochrome proteins -> lower energy yields
What is an alternative way to return electron carriers to their oxidized state?
Fermentation
What is the role of pyruvic acid in fermentation?
Oxidizes NADH back into NAD+
What is the fate of the NAD+ newly regenerated by fermentation?
It returns to glycolysis to pick up more electrons
What are two acids produced by fermentation?
Lactic acid & acetic acid
propionic acid
What is the intermediate product formed by pyruvic acid during alcoholic fermentation?
Acetaldehyde
Chemiosmosis uses __________ to supply the energy necessary to phosphorylate ADP to ATP
a protein gradient
What is Chemiosmosis?
ATP is generated in cells through the movement of protons (H⁺ ions) across a membrane, driven by an electrochemical gradient; leading to the phosphorylation of ADP to ATP via ATP synthase
Where is the majority of ATP generated in prokaryotic cells?
In the cytoplasmic membrane;
because that’s where the ETC is
Methanogens are bacteria that ____
convert CO2 and hydrogen to methane
Green sulfur bacteria oxidize ___ to ___.
Green sulfur bacteria oxidize hydrogen sulfide to sulfate
Nitrification:
Ammonia is converted to nitrite, then nitrate.
Denitrification:
Nitrate is converted to nitrogen gas
Ammonification:
Amino acids are converted to NH3 (ammonia)
Nitrogen fixation:
Nitrogen gas -> ammonia
What does Oxidation of sulfur result in?
The production of sulfate
What are Sulfate and nitrate?
The most readily used forms used by plants
How does Reduction of sulfur occur?
Sulfate is converted by bacteria to Hydrogen sulfide
What can leaching of sulfate produced by bacteria cause?
It can cause waterways to become acidic
What bacteria do Photoheterotrophs contain?
Green and purple non-sulfur bacteria
What bacteria do Photoautotrophs contain?
Use H2O to reduce CO2?
Yes: Cyanobacteria
No: Green and purple sulfur bacteria
Which type of organism uses hydrogen sulfide for reducing power?
Purple sulfur bacteria;
Purple sulfur bacteria employ anoxygenic photosynthesis with hydrogen gas, sulfur compounds such as hydrogen sulfide, or sulfur as an electron donor (reducing power) in photosynthesis
In which organism would you likely find a chlorosome?
Green sulfur bacteria;
Chlorosomes, or chlorobium vesicles, house bacteriochlorophylls
What is a bacterium that performs oxygenic photosynthesis?
Cyanobacteria;
Like plants and algae, cyanobacteria are oxygenic; meaning that their photosynthetic process generates oxygen
What is the key difference between photoheterotrophs and photoautotrophs?
Photoheterotrophs use organic compounds as their carbon source;
photoautotrophs use CO2 as their carbon source.
What is a trait unique to photosynthetic eukaryotes?
The presence of chloroplasts;
Chloroplasts are membrane-bound organelles, and thus unique to eukaryotes
Lipases break down ____
lipids
The Pentose Phosphate Pathway ____
(process)
is an example of anabolism
What is fermentation considered as?
(process)
Catabolism
What kind of reaction is photosynthesis? (process)
Anabolic
What process is oxidative phosphorylation?
A catabolic process
The reactions that occur between glucose and pyruvic acid can be either ____
anabolic or catabolic
Which location is LEAST likely to contain methanogens?
Surface of ice in the Antarctic;
Methanogens are anaerobic microorganisms the surface of ice in the Antarctic is an extreme environment with low temperatures and low organic matter availability
Without the light-dependent reactions of photosynthesis, the Calvin-Benson cycle would not be possible because it would lack which molecules?
ATP and NADPH
