Lecture 5: Cellular Respiration Flashcards
What is cellular respiration?
Cellular respiration is the process by which cells convert glucose into ATP through glycolysis, the Krebs cycle, and the electron transport chain.
What are electron carriers? Name the ones used in this lecture
Molecules that transport high energy electrons
-Nicotinamide adenine dinucleotide NAD+ gets reduced to NADH
-Falvin adenine dinucelotide
FAD gets reduced to FADH2
-Nicotinamide adenine dinucleotide phosphate hydrogen
NADP+ gets reduced to NADPH
What are two ways ATP can be converted into energy?
- substrate-level phosphorylation: ADP + Pi = ATP
- Oxidative phosphorylation: ATP generation through the ETC and chemiosmosis
What is the overall chemical equation for cellular respiration?
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
Where does glycolysis occur and what are its main products? Does it require oxygen?
Glycolysis occurs in the cytoplasm and produces 2 pyruvate molecules, 4 ATP, 2 ADP, and 2 NADH. Does not require O2.
What are the two phases of glycolysis?
-The energy investment phase (uses 2 ATP) steps 1-5, Energy is consumed. Glucose is split into 2 so everything in the second phase happens twice
-The energy payoff phase (produces 4 ATP and 2 NADH, with a net gain of 2 ATP). steps 6-10. energy is generated
What are the enzymes used in glycolysis?
- Hexokinase
- Phosphoglucose isomerase
- Phosphofructokinase-1
- Aldolase
- Triosephosphate isomerase
- Glyceraldehyde-3-phosphate dehydrogenase
- Phosphoglycerate kinase
- Phosphoglyceratemutase
- Enolase
- Pyruvate kinase
How can you remember the enzymes?
H.P.P.A.T.G.P.P.E.P
Helen
Paints
Pictures
Along the
Training
Grounds
Praying
people
Enjoy
Paintings
What are the steps in phase 1 of glycolysis?
Phase 1 (Energy Investment):
Step 1: Glucose is phosphorylated to glucose-6-phosphate by hexokinase.
Step 2: Glucose-6-phosphate is converted to fructose-6-phosphate by phosphoglucoisomerase.
Step 3: Fructose-6-phosphate is phosphorylated to fructose-1,6-bisphosphate by phosphofructokinase.
Step 4: Fructose-1,6-bisphosphate is cleaved into two three-carbon molecules (dihydroxyacetone phosphate and glyceraldehyde-3-phosphate) by aldolase.
Step 5: Dihydroxyacetone phosphate is converted to glyceraldehyde-3-phosphate by triose phosphate isomerase.
What are the steps in phase 2 of glycolysis?
Phase 2 (Energy Generation):
Step 6: Glyceraldehyde-3-phosphate is oxidized and phosphorylated to 1,3-bisphosphoglycerate by glyceraldehyde-3-phosphate dehydrogenase.
Step 7: 1,3-bisphosphoglycerate is converted to 3-phosphoglycerate by phosphoglycerate kinase.
Step 8: 3-phosphoglycerate is converted to 2-phosphoglycerate by phosphoglycerate mutase.
Step 9: 2-phosphoglycerate is converted to phosphoenolpyruvate by enolase.
Step 10: Phosphoenolpyruvate is converted to pyruvate by pyruvate kinase.
What are the products of glycolysis and how can you remember them?
Products:
Glucose
Glucose-6-phosphate
Fructose-6-phosphate
Fructose-1-6-Bisphosphate
Glyceraldehyde-3-phosphate
1-3-Bisphosphoglycerate
3-phosphoglycerate
2-phosphoglycerate
Phospho-enol pyruvate
pyruvate
Way to remember:
G.G.F.B.G.B.P.P.P.P
Gross
Guys
Favor
Big butts
Good
Boys
Prefer
Pretty girls ion
Pink
Pyjamas
What is the net reaction of glycolysis?
glucose + 2ADP + 2 Pi + 2NAD+ —> 2 pyruvate + 2 ATP + 2NADH
Explain pyruvate oxidation
THIS REACTION OCCURS WITH O2
Pyruvate has to get oxidized into acetyl-CoA before entering the Krebs cycle. Pyruvate reacts with enzyme called pyruvate dehydrogenase, it binds with NAD+ and oxidation occurs
Pyruvate + NAD+ —-> acetyl-CoA + NADH + CO2
pyruvate is a 3-carbon sugar but turns into a 2 carbon sugar so the third carbon leaves and a byproduct of CO2
once oxidized acetyl CoA gets moved into mitochondria through active transport.
What is the Krebs cycle?
Also called the citric acid cycle or the Tricarboxylic acid cycle.
-a biochemical pathway that is used to generate energy through oxidation of acetyl CoA. used for the synthase of NADH and production of amino acids
-takes place in the mitochondria with oxygens
What are the enzymes in the Krebs cycle and how to remember them?
- Citrate synthase
- Aconitase
- Isocitrate dehydrogenase
4.α-Ketoglutarate dehydrogenase - Succinyl-CoA synthetase
- Succinate dehydrogenase
- Fumarase
8.Malate dehydrogenase
How to remember:
S.A.D.D.S.D.F.D (S stands for synthase and D stands for Dehydrogenase)
So
At
Disco
Duck
Slippied
Down
Five Drinks
What are the products and how to remember them?
Citrate
Isocitrate
Alpha Ketoglutarate
Succinyle-CoA
Succinate
Fumerate
Malate
Oxaloacetate
How to remember:
C.I.K.S.S.F.M.O
Can
I
Kill
Someone
Special
For
Money
Officer
What are the results of Krebs cycle?
Krebs cycle happens twice so the products are doubled:
-2 ATP
- 6 NADH
- 2 FADH₂
- 4 CO₂
What is the electron transport chain?
series of protein complexes and electrons carriers that transfer electrons from electron donors (NADH & FADH2) to electron acceptors (OXYGEN) facilitating a series of redox reactions and creating an electrochemical gradient across the inner mitochondrial matrix.
Explain what happens in complex l.
Complex l AKA NADH dehydrogenase which consist of 46 polypeptides. Accepts high energy electrons form NADH, hydrogen is pumped through and into the intermembrane space. The NADH transfers electron onto coenzyme Q Ubiquinone.
What is coenzyme Q ubiquinone?
Lipid soluble and moves freely takes electrons form protein complex l and moves them to complex lll
Explain what happens in complex ll.
Complex ll also called succinate reductase. It accepts the high energy electrons from FADH2. It contains succinate dehydrogenase enzyme which transforms succinate into fumigate acid and form FADH+. Is not a proton pump
Explain complex lll.
Complex lll also called cytochrome c oxidoreductose. It accepts electrons from coenzyme q and takes the electrons and transfers them to cytochrome c. It also take H+ ions and creates an electrochemical gradient.
What is Cytochrome C?
Small water-soluble proteins that transfer electrons between complex lll and complex lV.
Explain complex lV.
The electrons are used to reduce O molecules into water molecules, it continues to pump protons out of the matrix into the intermembrane space which creates a proton gradient which ATP synthase uses.
Explain chemisomosis.
-Chemisomosis is the diffusion of ions down their electrochemical gradient across a semipermeable membrane.
-due to the higher proton concentration in the intermembrane space compared to the matrix the protons move down an additional membrane protein called ATP synthase.
-H+ binds to the rotor it rotates and moves into a second channel that leads to the matrix, it goes into the catalytic knob and ADP binds with Pi and ATP is released.
What is anaerobic respiration?
Process of producing energy without oxygen.
Cells undergo anaerobic respiration or fermentation to regenerate NAD+ for glycolysis.
Explain what occurs during anaerobic respiration.
-glycolysis yields 2 ATP through substrate-level phosphorylation and 2 NADH molecules
-The final electron acceptor can be organic or inorganic molecules
Why is there less ATP produced in anaerobic respiration compared to aerobic respiration?
Less ATP is produced because oxidative phosphorylation generates majority of ATP and requires oxygen as the final electron acceptor in aerobic respiration but in anaerobic respiration oxygen is not the final electron acceptor.
What is fermentation?
-When the final electron acceptor is an organic molecule.
-purpose is to regenerate NAD+ from NADH that was produced in glycolysis so that glycolysis can have a supply of NAD+ to continue producing ATP.
What is Lactic Acid fermentation?
-pyruvate gets reduced into lactate and is catalyzed by dehydrogenase. NADH is oxidized to NAD+ allowing glycolysis to continue.
Where does lactic acid fermentation occur in the body?
occurs primarily in muscle cells when oxygen levels are low, such as during intense exercise. When your muscles work harder than your oxygen supply can keep up with, they switch from aerobic respiration to anaerobic respiration, producing lactic acid as a byproduct. This can lead to muscle fatigue and the “burning” sensation you feel during strenuous activity.
What is alcohol fermentation?
-pyruvate is converted into acetaldehyde releasing CO2 which is catalyzed by pyruvate decarboxylase
-acetaodehyde is converted into ethanol which is catalyzed by alcohol dehydrogenase and NADH is oxidized into NAD+
How is cellular respiration regulated?
-GLUT4 (glucose transporter) controls the amount of glucose entering the cell for respiration.
-Phosphofructokinase regulate glycolysis based on ATP and ADP levels.
-pyruvate dehydrogenase regulates the conversion of pyruvate to acetyl-CoA inhibited by ATP, NADH, and acetyl-CoA
-several enzymes within Krebs cycle are responsible for regulation (high levels of ATP and NADH inhibit these enzymes, ADP and NAD+ can act as activators when ATP and NADH are too low.
-oxidative phosphorylation control depends on ADP levels, too high levels of ATP are too high the rate of oxidative phosphorylation slows down.
Explain how the levels of ATP and AMP affect phosphofrutokinase regulations.
-high levels of ATP can act as allosteric inhibitors slowing down glycolysis
-high levels of AMP can act as allosteric activator speeding up glycolysis
-citrate provides feedback regulation that links glycolysis to the later stages of respiration
Explain feedback inhabitation
Cellular respiration is regulate through feedback loops to prevent excess ATP regulation.
ATP and citrate inhibit phosphorylation
Explain metabolic connections.
- carbohydrates—>glucose used in glycolysis to form pyruvate
-lipids—> fats broken down into glycerol and fatty acid —-> fatty acids are broken down into process called beta-oxidation forming acetyl-CoA which enters TCA cycle
-proteins—> broken down into amino acids which convert to pyruvate and enter glycolysis or acetyl-CoA for TCA cycle
-nucleic acid can be broken down into nucleotides and can be metabolized
How can cellular respiration help build macromolecules?
-glycolysis intermediates help produce sugars
-acetyl-CoA helps form fatty acids and steroids
-amino acids are synthesized from intermediates in glycolysis and TCA cycle
-pentose sugar for nucleotides come from glycolysis
