Cell respiration Flashcards
1
Q
Where does cellular respiration take place?
A
- The cytoplasm (glycolysis) and mitochondria (synthesis of usable energy ATP)
2
Q
What type of reaction transfers chemical energy in the breakdown of organic molecules?
A
- Redox reactions, one compound is oxidized and the other reduced
- Oxidation: gaining oxygen, loss of electrons, loss of hydrogen, loss of potential energy
- Reduction: losing oxygen, gain of electrons, gain of hydrogen, gain or potential energy
- When electrons are gained or lost, the electrons become carriers of energy
- OIL RIG
3
Q
What happens during a redox reaction?
A
- In the oxidation step, the electrons that are lost are used in other parts of the cell. They are transported to a mitochondria where they are used in the electron transport chain to generate ATP
4
Q
What is phosphorylation?
A
- Process that occurs in photosynthesis and cellular respiration. Two types: substrate and oxidative
- A phosphate group is added which makes molecules less stable and hence ATP is a reactive molecule that contains high energy bonds (lots of energy —> unstable), more likely to react
- When ATP undergoes hydrolysis to form ADP + Pi, the energy stored in the phosphate bond is released for use by the cell (more stable)
5
Q
What are two functions of ATP? What energy is used for ATP production?
A
- It releases energy when hydrolysed to ADP (powers metabolism)
- It transfers the released phosphate group to other organic molecules making them less stable and more reactive
- To form ATP, either solar energy of energy from oxidative process is used
6
Q
What steps are required in the breakdown of organic molecules?
A
- The energy requirements are reduced as the activation energy is divided across several steps
- The released energy is transferred to activated carrier molecules by redox reactions
Check book
7
Q
What are carrier molecules? What are the two important electron carriers?
A
- Carrier molecules are called hydrogen carriers or electron carriers as they gain electrons and protons (H+)
- Energy stored in the organic molecule is transported by protons and electrons to the carrier molecules
- NAD+ is a electron carrier which is reduced to form NADH
(NAD+ + 2H+ + 2e– → NADH + H+) - FAD is a electron carrier which is reduced to form FADH2
(FAD + 2H+ + 2e– → FADH2) - The reduced electron carriers (NADH + H+) are transferred to mitochondria where they are used in the electron transport chain to generate ATP
8
Q
How does the energy transfer involving carrier molecules work?
A
- Energy that is released by oxidation reactions, is transported by reduced carrier molecules (NADH) to the cristae of the mitochondria
- The carrier molecules act as taxis
- Cristae: site of the electron transport chain, this chain uses the energy transported by the carriers to synthesize ATP
- The synthesize of ATP, requires oxygen to work so only aerobic respiration can generate ATP from hydrogen/electron carriers
Check book
9
Q
What is the purpose of glycolysis, the link reaction and krebs cycle?
A
- They must produce a high concentration gradient of protons (H+) so that ATP synthase uses them to generate a lot of ATP
- The generating occurs in the electron transport chain (chemiosmosis)
10
Q
What is glycolysis?
A
- First step in the breakdown of carbohydrates a.k.a cellular respiration
- Glycolysis occurs in the cytosol (cytoplasm) of the cell
- It is an anaerobic process (no oxygen needed) and results in a small net gain of ATP (2 molecules)
- Glucose broken down into two pyruvate molecules
11
Q
Explain the first two steps of gylcolysis.
A
- Phosphorylation: Glucose is phosphorylated (add a phosphate group) by two molecules of ATP to from hexose biphosphate which makes glucose less stable and more reactive
- Lysis: The hexose biphosphate (C6) is split into two triose phosphates (C3)
12
Q
Explain the last three steps of glycolysis.
A
- Oxidation: Through oxidation, hydrogen is removed from each C3 to reduce NAD+ to NADH + H+. Two molecules of NADH is produced (one from each C3)
- ATP formation: the energy released from the sugar is used to directly synthesise ATP which is called substrate level phosphorylation. 4 molecules of ATP are generated (2 per C3 sugar)
- Glucose has been broken down into two pyruvates and two hydrogen carriers have been reduced by oxidation. 4 ATP molecules are produced and 2 are used
- Most potential energy from glucose is now kept in the 2 pyruvates
13
Q
What happens when the availability of oxygen varies after glycolysis?
A
- When oxygen is available the pyruvate undergoes aerobic respiration and a further production of ATP (34 molecules)
- When oxygen is not available the pyruvate undergoes anaerobic respiration (fermentation) and no further ATP produced
14
Q
What happens in aerobic respiration after glycolysis?
A
- Pyruvate is transported to the mitochondria for further breakdown, oxidation is completed
- A lot of hydrogen carriers are reduced resulting in: NADH + H+ and FADH2
- The reduced hydrogen carriers release their stored energy to synthesis more ATP
- After this these processes follow: link reaction, krebs cycle and electron transport chain
15
Q
What happens in anaerobic respiration after glycolysis?
A
- Pyruvate is not broken down further and no more ATP is produced, oxidation is not completed. The pyruvate remains in the cytosol and is converted into lactic acid in animals or ethanol and CO2 in plants and yeast
