Respiration Flashcards
What are the basic processes of respiration, give brief explanation?
Glycolysis
- Breakdown of glucose into 2 pyruvate, release 2 ATP
Pyruvate Oxidation
- Conversion of pyruvate into acetylcoenxyme A(CoA)
Citric Acid Cycle/Krebs
- Acetyl CoA is oxidised to release energy (2 ATP) and high energy electron carriers (NADH and FADH2)
Electron Transport Chain/Oxidative Phosphorylation
- NADH drives electrons creating 34 ATP
- Proton gradient to transfer electrons across the membrane generates ATP production (oxidative P)
What are the 3 stages in respiration?
- Glycolysis
- Krebs Cycle/Tricarboxylic Acid Cycle (TCA)
- Oxidative phosphorylation
Glycolysis
- catabolism of glucose into pyruvate
- 1 glucose (6C) becomes 2 pyruvate (3C)
- produces 4 ATP and uses 2
Anaerobic glycolysis
- no oxygen available = fermentation
In plants and yeasts: - pyruvate from glycolysis is converted to ethanol and CO2
In animals: - pyruvate is converted into lactate
in both, NADH is oxidised to NAD+
Aerobic glycolysis
- pyruvate is transported across the inner mitochondrial membrane
- is oxidised into acetyl-CoA
- NADH is produced
Components of the Krebs Cycle (4)
Per 2 cycles: 1 glucose = 2 cycles
- 4 carbons enter as acetyl-CoA, are oxidised into 4 CO2
- 2 GDP becomes 2 GTP
- 2 FADH2 and 6NADH produced
The Glyoxylate Cycle only occurs in ___ and includes
plants;
- bypassing steps in the Krebs Cycle to prevent loss of carbon
Oxidative Phosphorylation
- 4th step in respiration
- energy, derived from the oxidation of nutrients, is used to create ATP through a series of redox reactions and a proton gradient
What is the difference between fermentation and cellular respiration?
- Fermentation does not need oxygen but cellular respiration does.
- (cellular respiration is aerobic. Fermentation is anaerobic)
What is the formula for the catabolic degradation of glucose by cellular respiration?
C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP
Cellular respiration and photosynthesis are both what type of reaction?
Redox reactions
What is the difference between oxidation and reduction?
LEO says GER;
- lose electrons oxidation
- gain electrons reduction.
What is the difference between the reducing agent and the oxidizing agent?
- Oxidizing agent is the electron acceptor
- The reducing agent is the electron donor
In cellular respiration, the electrons are not transferred directly from glucose to oxygen. Each electron is coupled with a proton to form a hydrogen atom; these are held in the cell by what electron carrier?
NAD+ which becomes NADH when joined with a hydrogen.
What is a coenzyme?
- A coenzyme is an organic nonprotein helper for catalytic activity.
- NADH+ is a coenzyme.
What is the normal route that electrons follow in cellular respiration?
- Glucose
- NADH
- electron transport chain
- oxygen
What’s the general process of cellular respiration?
- Glycolysis (substrate level phosphorylation)
- Citric Acid Cycle (substrate level phosphorylation)
- Oxidative Phosphorylation (electron transport chain) and chemiosmosis
Where does glycolysis occur?
in the cytosol of the cell
Why is glycolysis an appropriate term ?
It literally means “sugar splitting” which is what happens
- glucose is split into two pyruvate molecules.
The starting product of glycolysis is:
Glucose: a six carbon sugar
The end product of glycolysis is:
two 3 carbon sugars and pyruvate
What are the two stages of glycolysis?
The energy investment phase and the energy payoff phase
What is used in the energy investment phase of glycolysis?
Two ATP molecules are invested with the product of 2 ADP and 2 inorganic phosphate
?
What is the net gain of energy in glycolysis? Where is most of the energy?
- 2 pyruvate molecules, 2 ATP, 2 NADH and 2 H+.
- Most of the energy is still present in the two molecules of pyruvate.
What is the relationship between glycolysis and oxygen?
Glycolysis does not need oxygen it occurs without it
Before pyruvate enters the citric acid cycle it must be converted to___?
acetyl CoA
Oxidative Phosphorylation
- ATP synthase moves H+ ions that were pumped out of the matrix by the electron transport chain back into the matrix.
- The energy from the influx of protons into the matrix is used to generate ATP by the phosphorylation of ADP.
- For every NADH molecule that is oxidized, 10 H + ions are pumped into the intermembrane space ~3 ATP
- Because FADH2 enters the chain at a later stage, only six H+ ions are transferred ~ 2 ATP
- A total of 32 ATP molecules are generated in electron transport and oxidative phosphorylation
How many times does the citric acid cycle occur for each molecule of glucose?
2 times: once for each pyruvate.
How many NADH’s are formed from the citric acid cycle?
6 NADHs
How many total carbons are lost as pyruvate is oxidized in the citric acid cycle?
4: released as CO2 molecules
How many FADH2 are formed in the citric acid cycle?
2
How many ATPs are formed in the citric acid cycle?
2 as GTP
The citric acid cycle is performed twice —> in total how many molecules of each product are formed?
- 6 NADH
- 2 FADH2
- 2 ATP
Explain what happens to the six carbon molecules from the original glucose molecule?
They have broken into pyruvate and then into acetyl coA.
- As these molecules are oxidized the carbon eventually is all lost as CO2.
In the electron transport chain as the electron travels the molecules become ___ in free energy and ___ in electronegativity
Lower; higher
The molecule at zero free energy (end of the electron transport chain) is?
Oxygen
- the lowest in free energy and highest in electronegativity
Oxygen stabilizes the received electrons by:
Combining with two hydrogen ions to form water.
Explain the overall concept of how ATP synthase uses the flow of hydrogen ions to produce ATP
- H+ builds up outside of the membrane (intermembrane space) creating a hydrogen gradient.
- The hydrogen naturally wants to go to an area of lower concentration so it travels back in the mitochondrial matrix.
- As it does this it goes through the ATP synthase which causes the motor of the synthase molecule to spin and activates catalytic sites to form ATP from ADP and inorganic phosphate.
What is chemiosmosis? (3)
- Movement of ions across a semipermeable membrane
- Driven by an electrochemical gradient
- Generates ATP
Define proton motive force
- driving force that facilitates the movement of H+ protons across a membrane,
How many molecules of ATP can NADH form? FADH2?
Oxidation of NADH creates 3 ATP, whereas oxidation of FADH2 creates 2
Why does the total count of ATP produced vary?
- depends on the shuttle used to carry electrons from the cytosol to the mitochondrion. NADH is more effective than FAD
- not all of the energy from the proton motive force is used to create ATP
Fermentation allows the production of ATP without __?
Oxygen or an electron transport chain
What is the ultimate electron acceptor in fermentation since there is an absence of oxygen?
NAD+
Explain how alcohol fermentation starts with glucose and yields ethanol
Glucose is made into pyruvate then acetaldehyde. This is reduced by NADH into ethanol creating NAD+ once more (it is recycled)
Explain how lactic acid fermentation starts with glucose and yields lactate
- Glucose to pyruvate → reduced by NADH to make lactate. (no CO2 release)
- NADH reducing pyruvate creates NAD+ again
What three organic molecules are often utilized to make ATP in cellular respiration?
proteins carbohydrates and fats
The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is___
H+ concentration across the membrane that holds the ATP synthase
Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?
Glycolysis
In mitochondria exergonic redox reactions ___
provide the energy needed to establish the proton gradient
The final electron acceptor of the electron transport chain in aerobic oxidative phosphorylation is?
Oxygen
What is the oxidizing agent in lactic acid fermentation?
NADH which is used to produce Pyruvate as it is oxidised into NAD+
When electrons flow along the electron transport chains of the mitochondria what change occurs?*
The pH of the matrix increases as a H+ gradient is formed
Most CO2 from catabolism is released during ___
the citric acid cycle
Why is the citric acid cycle called a cycle?
The four carbon acid that accepts the acetyl CoA in the first step of the cycle is regenerated by the last step of the cycle
During glycolysis which molecule has the most chemical energy?
Fructose -1 with 6-bisphosphate
If mice were fed glucose with radioactive oxygen where would this oxygen appear again in a few minutes?
As carbon dioxide ( by product of cellular respiration)
A molecule becomes more oxidized when it__?
loses an electron
Most of the ATP produced in cellular respiration comes from which of the following processes?
Oxidative phosphorylation
A chemist has discovered a drug that blocks an enzyme that catalyzes the second reaction of glycolysis. He wants to use the drug to kill bacteria in people with infections. Why is this a bad idea?
Human cells also perform glycolysis and the drug will poison them as well.
Most of the NADH that delivers electrons to the electron transport chain comes from which part of cellular respiration?
The citric acid cycle (6 molecules produced)
What accompanies the conversion of pyruvate to acetyl coA before the citric acid cycle?
The release of CO2 and the synthesis of NADH
In preparing pyruvate to enter the citric acid cycle what steps occur?
- pyruvate is oxidized and decarboxylated
- then the removed electrons are used to reduce NAD+ into NADH
What is reduced in cellular respiration?
Oxygen
The function of cellular respiration is to
extract usable energy from glucose
Why is oxygen one of the strongest oxidizing agents known?
It is extremely electronegative
Where do the reactions of the citric acid cycle occur in eukaryotic cells?
the matrix of the mitochondrion
A small amount of ATP is made in glycolysis when?
transfer of a phosphate group from a fragment of glucose to ADP by substrate level phosphorylation.
What happens to the energy in glucose that does not become ATP?
It is converted/ released as heat
After the completion of the citric acid cycle most usable energy is in the form of?
NADH
How many molecules of ATP are gained by substrate level phosphorylation in cellular respiration?
4
What happens in a closed room full of people?
Temperature rises and CO2 levels rise. these are products of cellular respiration
In cellular respiration what is oxidized and what is reduced?
Glucose is oxidized and oxygen is reduced
Why is there no production of carbon dioxide in glycolysis?
the products of glycolysis have the same total number of carbon atoms as the glucose started with
What are most of the electron carriers in the electron carrier chain?
NADH, FADH2
accepts and donates electrons
What are obligate anaerobes?
they carry out only fermentation or anaerobic respiration. cannot survive in the presence of oxygen.
What are facultative anaerobes?
Many yeasts and bacteria - they use both fermentation and respiration
What is beta oxidation?
The process in which fatty acids are broken down to two carbon fragments that enter the citric acid cycle as acetyl CoA. other examples:
Where is the electron transport chain for cellular respiration located?
the inner membrane of the mitochondria (the cristae)
