-Occurs in both plants and animals
2 Pathways of Cellular Respiration:
- Both begin with glycolysis
a.) Anaerobic Respiration
- Oxygen = not available
1.) Alcoholic Fermentation - Yeast
2.) Lactic Acid Fermentation - Muscles
b.) Aerobic Respiration
- Most efficient pathway
- Oxygen = available
- Yields large amounts of ATP
- Occurs in mitochondria
Glycolysis
-Takes place in cytosol
- First pathway of cellular respiration
- Begins with glucose
Lactic Acid and Alcoholic Fermentation
Lactic Acid Fermentation
- Muscle cells, yogurt cheese
- Produces NAD+ and
lactic
acid
Alcoholic Fermentation
- Yeast
- Produces NAD+ and
ethyl
alcohol
Aerobic Cellular Respiration
a.) Glycolysis in cytoplasm
b.) Krebs Cycle and ETC in Mitochondria
2 Types of Chemical Reactions:
a.) Oxidation
- Results in many C-O bonds
- Results in compounds with lower potential energy
b.) Reduction
- Results in many C-H bonds
- Results in compounds with higher potential energy
Fe2+à Fe3+
+ electron Oxidation
Fe3+ + electron à Fe2+ Reduction
Terms:
-Phosphorylation: addition of phosphate group to compound/molecule
Ex: Glucose + 2 ATP --> Hexose Bi-phosphate
- Substrate-Level Phosphorylation: way of producing ATP
Ex: ADP + Phosphate --> ATP
- Decarboxylation: removal of carbon atom
- Oxidative Decarboxylation: removal of hydrogen atom and carbon dioxide
- Coenzyme: molecule that aids an enzyme in its action by acting as electron donor/acceptor
Ex: Acetyl CoA
Uses for ATP in Respiration
a.) Releasing energy
- Breaking of chemical bonds
- Loses phosphate
- Bond between 2nd and 3rd phosphate group broken
b.) Substrate Level Phosphorylation
- Forming ATP
- Cells create ATP to store energy
- ADP--> grabs Pi --> Energy stored in ATP bond
- Breaking down ATP to make ADP to release energy
Glycolysis
- Splitting of glucose into two pyruvate (3-carbon molecules)
- One hexose sugar converted into two 3-C atom compounds (pyruvate) with net gain of 2 ATP and 2 NADH + H+
- Both pathways begin with:
- Total of 4 ATP molecules
- Requires 2 ATP to start process -- net gain of 2 ATP per glucose molecule
4 Steps to Glycolysis:
Step 1 - Phosphorylation - Energy Investment Phase
- Phosphates from 2 ATPs are added to glucose to create hexose bi-phosphate molecule
1.) Hexokinase (enzyme that transfers 1st phosphate to sugar)
- Product formed called Fructose-6-Phosphate
2.) Phosphofructokinase (2nd enzyme that transfers 2nd phosphate to sugar) -
- Product formed called Fructose-1, 6-bi-phosphate (hexose bi-phosphate)
-- 6 carbon sugar with 2 phosphates attached
Step 2 - Lysis
1.) 6-carbon phosphorylated fructose splits by enzyme aldolase into two, 3-carbon sugars with phosphate attached
-Product formed: 3-carbon sugars (G3P) - triose phosphate molecules
Step 3 - Oxidation - Energy Payoff Phases begin
1.) Each G3P undergoes oxidation by enzyme triose phosphate dehydrogenase where it loses 2 atoms of hydrogen by reducing NAD+
into NADH + H+
2.) While NADH is formed, releases energy enzyme then uses to add phosphate group to both of 3-carbon molecules with one phosphate group
- Results in a 3-carbon molecule with 2 phosphate groups attached (Phosphogylcerate - PGA)
Step 4 - ATP Formation
1.) Enzyme removes the 2 phosphate groups
2.) Enzyme Enolase extracts water molecule, forming phosphoenolpyruvate (PEP)
3.) Phosphate groups transferred from PEP to ADP (substrate-level phosphorylation_)
4.) ATP is produced
- Product: 2, 3-carbon molecules called Pyruvate
Glycolysis Summary
- 2 ATPs used to start process
- 4 ATP produced (net gain of 2)
- 2 NADH molecules produced (NAD+ converted into NADH + H+
- Includes: phosphorylation, lysis, oxidation, ATP formation
- Pathway controlled by enzymes
- In cytoplasm, one glucose (6C) is converted into 2 pyruvate (3C) molecules
Mitochondrial Structure in Relation to its Functions
1. Cristae folds increase surface area for electron transfer system
2. Double membrane creates small space into which H+ can be concentrated
3. Matrix creates isolated space in which Krebs cycle can occur
Aerobic Cellular Respiration
1.) Glycolysis (see above)
2.) Link Reaction and Krebs Cycle
- Occurs in mitochondrial matrix
- Requires Oxygen
a.) Link Reaction:
- Produces 1 CO2 and 1 NADH for every pyruvate
b.) Krebs Cycle
- 2 ATP produced for life processes
*1 from one Krebs Cycle runs twice
- 6 Molecules of NADH produced
*3 from one Krebs Cycle that runs twice
- 2 Molecules of FADH2 produced
*1 from Krebs Cycle that runs twice
- 4 Molecules of CO2 produced
* 2 from Krebs Cycle that runs twice
3.) Electron Transport Chain
- Requires oxygen
a.) Final electron acceptor
- Where most of ATPs from glucose catabolism produced
- Occurs in intermembrane space and membranes of cristae
- Water = waste product
Aerobic Cellular Respiration Step 2 Part A: Link Reaction
1.) Pyruvate from glycolysis absorbed by mitochondria after glycolysis when oxygen = present
2.) Pyruvate enters matrix of mitochondria by active transport
3.) Oxidative decarboxylation
- Goal = hydrogen and carbon dioxide removed from pyruvate
4.) Enzymes in matrix of mitochondria remove hydrogen and carbon
5.) Pyruvate = decarboxylated to form acetyl group (2C)
- CO2 released
6.) Pyruvate = oxidized
- Hydrogen atom accepted by NAD+ to form NADH + H+
7.) Acetyl group combines with coenzyme (CoA) to form Acetyl CoA
8.) Acetyl CoA then enters Krebs cycle to continue aerobic respiration process in matrix of mitochondria
Acetyl coenzyme A (Acetyl CoA)
- Pyruvic Acid from Glycolysis converted to Acetyl CoA - 2C compound
- Fatty acids = source of energy in cellular respiration
CH3(CH2)nCOOH
** Glycolysis = not needed; goes straight to link reaction **
- Fatty acids have long chain of carbon atoms.
- CoA can oxidize this chain and break it down
- Fatty acids make Acetyl CoA with two carbons and carries them to Krebs Cycle
- If odd number of carbons, remaining carbon atom released as CO2
Krebs Cycle
—Acetyl CoA (CH3CO) yields 2 CO2
C2
+ C4 = C6 → C5 +
CO2 → C4 + CO2
Aerobic Cellular Respiration Step 2: Part B: Krebs Cycle
1.) Formation of citrate
- Acetyl CoA from link reaction combines acetyl group (2C) with oxaloacetate (4C)
2C + 4C = 6C
- Results in 6-carbon molecule called citrate/citric acid
2.) Citrate converted to isocitrate by removal of one water molecule and addition of another
3.) Oxidation
- Isocitrate (6C) goes through oxidative decarboxylation to form a 5C compound (Alpha-ketoglutarate)
NAD+ is reduced to NADH + H+ (oxidized).
Carbon dioxide removed decarboxylation process to form waste product
4.) 5C = oxidized and decarboxylated again
- Coenzyme A added to form 4C compound (succinyl-CoA)
- CO2 released
5.) This 4C undergoes various changes to be converted back into oxaloacetate (4C)
- Phosphate group displaces CoA from succinyl-CoA which produces succinate (4C)
- Substrate-Level Phosphorylation
6.) Succinate is oxidized by molecule FAD (Flavin adenine dinucleotide)
- Creates Fumarate (4C) FAD--->FADH2
7.) Enzyme adds water to fumarate to form malate (4C)
8.) Malate oxidized by NAD+ molecule reducing NAD+ to NADH + H+ and regenerating oxaloacetate
Produces:
- 2 ATP
- 6 NADH
- 2 FADH2
- Oxaloacetate
- 4 CO3
Oxaloacetate will begin cycle again
- Phosphate group displaces CoA from succinyl-CoA which produces succinate (4C)
- Substrate-Level Phosphorylation
6.) Succinate is oxidized by molecule FAD (Flavin adenine dinucleotide)
- Creates Fumarate (4C) FAD--->FADH2
7.) Enzyme adds water to fumarate to form malate (4C)
8.) Malate oxidized by NAD+ molecule reducing NAD+ to NADH + H+ and regenerating oxaloacetate
Produces:
- 2 ATP
- 6 NADH
- 2 FADH2
- Oxaloacetate
- 4 CO3
Oxaloacetate will begin cycle again
- Cycle follows one acetyl group
- Each glucose that enters will produce 2 acetyl groups
- Each glucose that enters will produce 2 acetyl groups
Aerobic Cellular Respiration Step 3- Electron Transport Chain
- Pathway where most of ATPs from glucose catabolism are produced
- Contains series of electron carriers
- Carriers will form "chain" to pass electrons and proteins from one another
- - As electrons are transported, small amounts energy released
- NADH and FADH2 from Krebs Cycle will pass electrons to ETC
- Electrons passed as H+ ions to be pumped out of matrix --> cross into inner mitochondrial matrix --> travel into intermembrane space
- Proton gradient = produced
- Energy = released in process
ETC Steps
1.) NADH supplies 2 electrons to first carrier in chain (initially flavoprotein - FMN) and then series of Fe-S proteins
- Drops off H2 in inner mitochondrial space
- Turns into NAD+ again
2.) The 2 electrons pass along chain of carriers because they give up energy each time they pass from one carrier to next
3.) At 3 points along chain enough energy is given up for ATP to be made by ATP synthase
4.) Proteins move from inner membrane space to matrix and produce ATP (Oxidative Phosphorylation)
- ATP synthase = located in inner mitochondrial membrane (look on ppt for detailed arrows)
* In the chain, electrons pass from one carrier to another because receiving molecule has a higher electronegativity (stronger attraction of electrons)
- Process accomplishes pumping of four protons across inner mitochondrial membrane to inner membrane space (used to generate ATPs)
5.) The iron sulfur protein then passes electrons to compound ubiquinone (Q - lipid (only member not a protein)
- Most of remaining electron carriers between Q and oxygen are proteins - cytochromes (cyt)
- Cytochromes prosthetic group = heme (iron atom)
6.) FADH2 enters ETC further along --> sufficient energy released for ATP production by electrons for FADH2
- FADH2 passes electrons to electron carrier
- Hydrogen = moved from matrix to intermembrane space
- Products: Carbon dioxide, water, and ATP
Role of Oxygen
- Final electron acceptor in ETC
- Oxygen accepts hydrogen ions to form water
- If oxygen = not available, electron flow along ETC stops
- Glycolysis can still occur
- Process that occurs at inner membrane
- Chemiosmosis involves movement of protons (H2 ions) moving across membrane (down its concentration gradient) to provide energy so that oxidative phosphorylation (ATP synthesis) can occur
A.) ATP synthase:
- too many H2 ions are in intermembrane space (high concentration)
- creates overall positive charge
- Accumulation of H2 will cause proton force
- Allows movement of H2 ions through ATP synthase --> uses energy from H2 flow to couple phosphate with ADP to produce ATP
- The Production of ATP
- ATP synthase uses energy from H2 flow to phosphorylate with ADP
- ATP = produced
* Each NADH pumped 3 pairs of H2 atoms --> produces 3 ATPs
Protons move from inner membrane space to matrix
1 comment:
Sarah,
Your blog post looks great! I really like how you included the pictures from the ppt, and how you added information about the metabolism of lipids. Way to go! If possible, I would like to see some of the information condensed from the ppt so that it is just the "nuts and bolts" of what needs to be studied. :)
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