SBI4U - Cellular Respiration
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3 overall goals of cellular respiration
- 1) break bonds between 6 carbon atoms and glucose
- 2) move H atoms from glucose to oxygen to form six water molecules
- 3) trap as much free energy released in form of ATP
Describe the process of glycolysis
- Starts with glucose
- Phosphorylation turns glucose to glucose 6-phosphate
- Rearrangement - flucose 1,6 - phosphate
- Phosphorylation - Fructose 1,6 - biphosphate
- Split and conversion - DHAP & G3P (the carbons get split here)
What is produced at the end of glycolysis?
- 2 pyruvate
- 2 NADH
- 4 ATP
- 2 H
- 2 ADP
Why is NADH and FADH2 so important in cellular respiration?
NADH and FADH2 are energy harvesting reactions that will eventually transfer most of their free energy to ATP molecules. They also act as mobile energy carriers within the cell, moving free energy.
The first three stages of cellular respiration form NADH and FADH2, whereas the last stage uses them to transfer free energy
What percentage of free energy does glycolysis transfer in 1 mol of glucose tp ATP?
2.2%; energy is released as heat, majority of energy in pyruvate and NADH molecules
True or false: prokaryotes and eukaryotes have mitochondria
False; only eukaryotes
Describe the process of the Pyruvate Cycle
- 3C pyruvate split; one into CO2 exhaled out, the other two make 2C acetate
- 2C acetate gets attached to coenzyme A to form acetyl CoA (sulfur containing compound)
- NAD is reduced to NADH to move to stage 4
So, during this cycle, two things occur: the formation of acetyl CoA, and the reduction of NAD
Why is acetyl CoA the focal point of cellular respiration?
All nutrients can yield acetyl CoA; can be used for cellular respiration or fat production
What products are produced after pyruvate oxidation?
In pyruvate oxidation, what do the two H+ ions do?
Remain dissolved in the matrix
The chemical potential energy in glycolysis has been transformed to
terminal phosphate bond of ATP
high energy electrons in NADH
CPE in pyruvate
The chemical potential energy in pyruvate oxidation has been transformed to
high energy electrons of NADH
Acetyl – CoA
Of the eight steps, how many steps in the Kreb cycle release energy?
Describe the Kreb Cycle
The Kreb Cycle is a cycle, as the final product in step 8, oxaloacetate, is the reactant in step 1.
Oxaloacetate/acetyl CoA -> citrate (6C) -> Isocitrate (6C) -> alpha Ketoglutarate (5C) -> Succinyl CoA (4C) -> Succinate (4C) -> fumarate (4C) -> malate (4C) -> oxaloacetate (4C)
What are your products at the end of the Kreb Cycle?
Energy stored at end of Krebs, CPE in acetyl-CoA has been transferred to
- high energy electrons of NADH
- high energy electrons of FADH2
- Terminal phosphate bond of ATP
Why is the Kreb Cycle also called the tricarboxylyic acid cycle?
Oxaloacetate has two carboxyl groups, while citrate has three carboxylic groups.
Where is FADH2 produced?
Krebs Cycle ONLY
What is the main purpose of the Kreb Cycle?
To produce NADH and FADH2
How is ATP formed in the Kreb Cycle?
Step 5, by substrate level phosphorylation
What is the difference between substrate level phosphorylation and oxidative level phosphorylation?
Substrate-level is a direct method of ATP production. It does not need oxygen. This process has a substrate attaching a phosphate group to ADP
Oxidative-level phosphorylation is the major source of ATP. It requires oxygen, uses redox reactions using NAD, FAD, ETC, inner mitochondrial membrane, ATPase, and O (basically used in step 4)
Describe the Electron Transport Chain
Now that you have all your NADH and FADH2, let's make some coco
ETC is basically a series of 5 compounds being more electronegative than the rest.
You have a lot of NADH and FADH so they gon transfer their electrons. These electrons will move like cray cray throughout, becoming more and more stable. NADH gives its electrons to NADH dehydrogenase; FADH gives its electrons to Q.
Q and cytochrome c shuttle the electrons until their reach the final protein complex, cytochrome oxidative complex, which has an enzyme to catalyze a reaction between electrons n shit to form water.
Oxygen is the final electron acceptor bee tee dubs
Note that the free energy released in the process moved protons (H+) from the mitochondrial matrix through proton pumps into the intermembrane space. This converts the chemical potential energy of electron to electrochemical potential energy of a proton gradient across the inner mitochondrial membrane
Distinguish NADH and FADH2 roles in the ETC
NADH passes its electrons on to the first protein complex, NADH dehydrogenase, pumping three protons
FADH2 transfers its electrons to Q, the second component of the chain, pumping two protons into the intermembrane space
2 ATP are formed per FADH2 and 3 ATP molecules are formedper NADH
Distinguish NADH from glycolysis and NADH from pyruvate and Krebs
NADH produced in glycolysis can diffuse from outer mitochondrial membrane into the intermembrance space, but not through the inner membrane into the matrix, so a shuttle is used
Who developed the theory of chemiosmoisis?
Peter Mitchell!!!! :D:D:D:D:D:D:D
Describe the process of chemiosmosis
This section deals with da protons from the electrons becoming more stablized. The free energy moves the protons into the inter membrane space.
Because the inner mitochondrial membrane is impermeable to protons, protons need to be pumped in. This pump creates an electrochemical gradient.
When the protons are shot out, they be like no bitch let me come in, so protons can only come back in the matrix via protein channels associated with ATP synthase using a proton-motive force
Protons moving in creates energy to phosphorylate ADP to ATP!
After chemiosmosis and the good lord ATP is produced, where does ATP go?
Moved by facilitated diffusion out of matrix, out of mitochondria, into cytoplasm of da cell
The theoretical yield of ATP is 36, yet cellular respiration produces less than 36 ATP. Why?
The inner mitochondrial membrane is not completely impermeable to H+; some H+ ions leak through the membrane, reducing the number that go through the ATPase complex to produce ATP
Some of the protons in the H+ reservior are used by the cell for other energy-requiring activities, causing a reduction in the number of ATP molecules produced by chemiosmosis
What is the efficiency percentage of aerobic respiration?
What is the glycerol-phosphate shuttle?
Transfers electrons from cytosolic NASH to FAD to produce FADH2
What is metabolic rate? What is a basal metabolic rate?
Amount of energy converted by an organism over a given period of time; amount of energy needed for an organism to live [minimum] - 60-70% of energy used
Explain how a calorimeter works
The calorimeter is an insulated vessel containing a known mass of water and a thermometer. As the person lies perfectly still in the calorimeter, thermal energy expended by the body is transferred to the water, causing its temperature to rise.The amount of thermal energy released is calculated on the basis that 4.2 J of energy is required to raise the temperature of 1.0 g of water by 1°C. Since the thermal energy expended by the body comes from the oxidation of food, the calculated energy value is proportional to the person’s BMR.
What is protein catabolism?
Proteins -> amino acids; AA deaminized to produce an amino acid skeleton.
- This skeleton can be used for many things,
- eg. Leucine -> acetyl CoA (KREBS)
eg. Alanine -> pyruvate (pyruvate oxidation)
eg. Proline -> Alpha ketoglutannate (KREBS)
How does fat catabolism work?
Digested fats can go into glycerol or fatty acids
In fat catabolism, what happens when the digested fats are turned into glycerol?
The glycerol can be converted in glucose by gluconogenesis to make DHAP and G3P in glycolysis
In fat catabolism, what happens when the digested fats are turned into fatty acids?
It is transported in matrix for oxidation; makes acetyl CoA to enter Krebs
What is ethanol fermentation?
Occurs in small bacteria
2 pyruvate -> 2 acetaldehydes [OH] -> 2 ethanols
In the process, CO2 is produced and exhaled, and NADH is oxidized to NAD+
How do anaerobic pathways work?
Because there's a lot of NADH, in the absence of O, NADH cannot be oxidized to NAD+; rather, it can donate its H to other molecules to make NAD+
What is lactic acid fermentation?
Humans do this!
2 pyruvates -> 2 lactates
In the process, 2 NADH is turned into 2 NAD+
What happens during lactate accumulation?
Eventually, lactate is transported into the liver. Once O is available, lactate will convert back to pyruvate.
How is total physical fitness measured?
aerobic fitness, muscular strength endurance, flexibility, body composition (fat/bone/muscle ratio)
AEROBIC CELLULAR CONTROLS: what inhibits phosphofructokinase and where?
ATP and citrate; step 3 in glycolysis
AEROBIC CELLULAR CONTROLS: what activates phosphofructokinase?
ADP; step 3 in glycolysis
AEROBIC CELLULAR CONTROLS: what activates pyruvate decorboxylase and where?
AEROBIC CELLULAR CONTROLS: what inhibits pyruvate decorboxylase and where?
NADH; pyruvate oxidation (pyruvate)
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