Chapter 6 Flashcards
Respiration and Fermentation
Cellular respiration definition
A process that releases energy (ATP) from glucose in a series of small steps
- if all the energy were released at once, much of it would be lost as heat and also destroy cells like a bomb
Aerobic cellular respiration
-respiration that requires oxygen
-is used by all plants and animals, as well as many microbes
-the energy from glucose is extracted, that energy is put into ATP so cells can use it
-all 3 domains and all eukaryotic kingdoms use it
Aerobic cellular respiration equation
Glucose and oxygen into carbon dioxide, water and ATP
C6H12O6 + 6O2»_space; 6CO2 + 6H2O + ATP
Krebs cycle
Stage in cellular respiration that completely oxidized the products of glycolysis (oxidize pyruvate)
FADH2
Flavin Adenine Dinucleotide- coenzyme that carries electrons in respiration
Electron transport chain
Membrane bound molecular complex that shuttles electrons to slowly extract their energy
ATP Synthase
Enzyme complex that emits protons through a membrane, triggering the phosphorylation of ADP to ATP
3 stages of cellular respiration
1.) glycolysis
transition step
2.) Krebs cycle
3.) electron transport chain
Glycolysis
Directly means “splitting of glucose”
-during glycolysis, 1 molecule of glucose is split into two 3-carbon molecules of pyruvate
-these reactions release 2 molecules of ATP
-inside the cytoplasm (outside the mitochondria)
Transition step
Comes after glycolysis
-2 molecules of pyruvate are oxidized into 2 molecules of Acetol CoA (a carbon atom is stripped from each and leaves the cell as carbon dioxide)
-this reaction releases 2 molecules of NADH2
-in the mitochondrion (matrix) for eukaryotic cells
-in the cytosol for prokaryotic cells
The Krebs cycle
After transition step
-inside the mitochondria (matrix) for eukaryotic cells, the Acetol CoA molecules are disassembled during the the Krebs cycle
-energy from Acetol CoA is transferred to electrons
-these reactions release 2 molecules of NADH2 (and ATP?)
-inside the cytosol for prokaryotic cells
The electron transport chain step
After Krebs cycle
-electrons from NADH and FADH are unloaded into the electron transport chain, where the potential energy in the electrons are used to produce more ATP
-they create a proton (H+) gradient
-these electrons require oxygen and release water
-inside the mitochondrion (inner membrane) for eukaryotic cells
-inside the cell membrane for prokaryotic cells
-inside thylakoid membranes of chloroplasts
Oxidation of glucose
During glycolysis and the Krebs cycle, electrons are removed from glucose (oxidizing it). NAD+ and FAD+ gain electrons (they are reduced to NADH and FADH2)
Reduction of CO2
In the electron transport chain, electrons from NADH and FADH2 are used to reduce (add electrons to) O2, which bonds with hydrogen atoms to form H2O
Glycolysis definition
A metabolic pathway occurring in the cytosol of cells (prokaryotic and eukaryotic)
-a 6-carbon molecule splits into two 3-carbon molecules of pyruvate
-Yields 2 ATP and NADH
-doesn’t require oxygen
Pyruvate definition
The 3-carbon product of glycolysis
NADH definition
Nicotinamide Adenine Dinucleotide
-a coenzyme that carries electrons in glycolysis and cellular respiration
2 phospholipid bilayers of the mitochondria
Outer membrane and inner membrane
-many enzymes are embedded in the inner membrane, catalyzing the reactions of the electron transport chain
Mitochondrial matrix definition
The fluid enclosed within the inner membrane
-location of the Krebs cycle
Intermembrane compartment definition
The space between the mitochondrial membranes (inner and outer)
Crista
Plural- Cristae
-fold of the inner mitochondrial membrane along which many reactions of cellular respiration occur
5 basic energy investment steps of glycolysis
1.) phosphate is transferred from ATP to glucose
2.) rearrangement
3.) a second phosphate transferred from ATP
4.) a 6-carbon intermediate splits into two 3-carbon intermediates
5.) one of the intermediates is converted into the other type, so there are 2 molecules of PGAL (phosphoglyceraldehyde)
5 basic steps of energy harvest in glycolysis
6.) oxidation and phosphorylation
7.) substrate-level phosphorylation yields ATP
8.) rearrangement
9.) removal of H2O
10.) substrate-level phosphorylation yields ATP and 2 molecules of pyruvate per glucose
Glycolysis- glucose is activated
-glycolysis requires an input of 2 ATP to activate glucose
-the activated glucose is then converted into two 3-carbon intermediated called PGAL
Glycolysis- NADH is produced
-first, each PGAL is oxidized, producing 2 NADH molecules
-NADH is an electron carrier molecule (it carries electrons that store energy)
Glycolysis- ATP is produced from ADP
PGAL (an enzyme) donates its phosphate group to ADP, producing ATP molecules via substrate-level phosphorylation
Glycolysis- a net of 2 ATP are produced
-in total, 4 ATP are produced
-2 ATP were used to start the reactions
-so, the net yield is 2 ATP
Does glycolysis require oxygen?
No, it doesn’t require oxygen
-glycolysis can occur in anaerobic conditions
Glycolysis reactants and products
Requires: 1 glucose, 2 NAD+, and 2 ADP
Yields: 2 pyruvate, 2 electron carrying NADH molecules, and 2 ATP
Acetol CoA
Acetyl Coenzyme A- molecule that enters the Krebs cycle
-product of partial oxidation of pyruvate
How many times does the Krebs cycle turn for 1 glucose?
The Krebs cycle turns twice for each glucose
-1 glucose=2 pyruvate
What is the net output for the Krebs cycle?
-2 ATP
-6 NADH
-2 FADH
-(4 CO2 is released)
Chemiosmotic Phosphorylation definition
Reactions that produce ATP using ATP synthase and the potential energy of a proton gradient
What is ATP synthase?
It is an enzyme that uses the potential energy in a proton gradient (H+) to produce ATP
6 steps of the Krebs cycle
-Acetol CoA combines with a 4-carbon molecule called oxaloacetate, yielding a 6-carbon citrate
-citrate is rearranged and oxidized, converting it into several intermediates (for each turn of the cycle, these reactions give off 2 molecules of carbon dioxide)
-as citrate is converted, each turn of the cycle produces 1 ATP via substrate-level phosphorylation
-as citrate is converted, each turn of the cycle transfers electrons to different electron carrier molecules, yielding 3 NADH and 1 FADH2
Krebs cycle, what is citrate converted into
Citrate is converted into isocitrate, a-ketoglutarate, succinyl CoA, succinate, fumarate, and oxaloacetate
-CIKSSFMO
How many ATP does the electron transport chain yield?
34 ATP
What happens at the end of the electron transport chain?
Electrons are donated to an oxygen atom, which combines with hydrogen atoms to form water
(oxygen is the final electron acceptor. Without it, the chain shuts down)
Aerobic cellular respiration math on how to get the yield of ATP
-glycolysis produce 2 ATP and 2 NADH
-NADH transferred to mitochondrion (2 ATP lost)
-transition step produce 2 NADH
-Krebs cycle produce 2 ATP, 6 NADH, and 2 FADH2
-electron transport chain produce 34 ATP (theoretical yield), cashed in 10 NADH (30/34 ATP), cashed in 2 NADH (4/34 ATP)
-36 ATP produced per glucose molecule (theoretical yield)
-30 actual yield because of loss of energy
What other food molecules enter the energy extracting pathways and how?
-polysaccharides like glycogen and starch are digested to glucose which enter at glycolysis
-proteins are digested as amino acids, which enter as pyruvate, acetol CoA, or Krebs cycle intermediates
-fats are digested to glycerol and fatty acids. Glycerol is converted to pyruvate and fatty acids are broken down to Acetyl CoA molecules (both of which enter the Krebs cycle)
Anaerobic Respiration definition
-includes the Krebs cycle and the electron transport chain
-ETC uses electron acceptor molecules other than oxygen (like CO2, NO3- nitrate, and SO4^2- sulfate)
-many prokaryotes like bacteria and archaea use it
-Produce less ATP than aerobic respiration
Fermentation definition
-no Krebs cycle or electron transport chain
-simply allows glycolysis to continue producing small amounts of ATP
-alcohol, lactic acid, and other byproducts
-yields only 2 ATP
How does fermentation regenerate itself?
-electrons from NADH are transferred to pyruvate, this regenerates NAD+ for glycolysis to continue
Alcoholic fermentation definition
-microbes carry out alcoholic fermentation
-NADH reduces pyruvate from glycolysis to ethanol and CO2 and then its recreated
Lactic acid fermentation definition
-bacteria and muscle cells both carry out lactic acid fermentation
-NADH reduces pyruvate to lactic acid and NAD+ and then recreated
Compare photosynthesis and respiration
Photosynthesis:
-food- produced
-energy- stored as glucose and other sugars
-light- required
-H2O- consumed
-CO2- consumed
-O2- released
Respiration:
-food- consumed
-energy- released from glucose and other food molecules
-light- not required
-H2O- released
-CO2- released
-O2- consumed
