5.7 Respiration Flashcards
Respiration
process by which energy stored in complex organic molecules is used to make ATP. This occurs in all living cells.
Purpose of respiration
is to give us ATP = form of energy
Photoautotrophs
plants = use light energy to make their food
Ways respiration releases energy
Chemical energy (atp), thermal energy
Endotherms
Organisms that use physiological processes (vasoconstriction etc) to heat up and cool down
Ectotherms
Organisms that only rely on external surfaces to change their temperatures
2 types of respiration
aerobic (under presence of oxygen) and anaerobic (when oxygen levels are limited)
What happens when ATP is hydrolysed
small manageable amounts of energy are released which won’t cause damage.
What’s done w the heat released
helps keep living organisms warm, and helps enzymes work near their optimum rate
Mitochondria
- site of aerobic respiration = not glycolysis but the rest
- Double envelope
- Matrix = liquid
- Inner membrane folded into Cristae
- Stalked particles = ATP synthase
- Inner membrane contains electron transport channels and ATP synthase
- Space between inner and outer membrane = inter membrane space
- The matrix contains mitochondrial ribosomes, looped DNA and enzymes for respiration
Glycolysis (in anaerobic, aerobic or both?)
Both
Where does glycolysis occur
In the cytoplasm
Glycolysis
- Glucose (6C) enters and gets phosphorylated using 2 ATPs into hexoxe bisphosphate (6C) THIS IS IMPORTANT TO BE DONE ASAP = if glucose stays as glucose in the cell then the concentration gradient would stop so glucose wouldn’t move into the cell anymore. Done immediately to maintain concentration gradient.
- This splits into 2x triose phosphate each w 3C
- 2TP are converted to 2x pyruvate (by enzyme pyruvate kinase) each w 3C this produces 2 reduced NAD (done by using NAD and hydrogens) and 4ATP
- This produces 2x ATP and 2x pyruvate and 2x reduced NAD
What does glycolysis produce?
2x ATP and 2x pyruvate and 2x reduced NAD
NAD and NADP
NAD and NADP are co enzymes for dehydrogenase
Co enzymes are usually made from vitamins
NAD is a nucleotide
NAD forms NADH by accepting electrons and protons
NADH to NAD
If there’s oxygen present, NADH is oxidised back to NAD, so it can be used again in glycolysis. NAD is regenerated further down the respiratory chain
If no oxygen present, NAD woukd run out and the production of ATP would stop. NAD is regenerated by fermentation
Is link reaction in aerobic, anaerobic or both?
Aerobic
Where does the link reaction occur
In the mitochondrial matrix
Link reaction
- Pyruvate (3C) turns into acetyl CoA (2C). 1 reduced NAD and CO2 are produced per pyruvate.
- Pyruvate becomes decarboxylated and dehydrogenated. This is catalysed by pyruvate dehydrogenase.
Where does the Krebs cycle occur?
In the mitochondrial matrix
Krebs cycle
What does the Krebs cycle produce?
2CO2, 3NADH, 1 ATP and 1 FADH (coenzyme for dehydrogenase (FAD accepts 2 hydrogen atom))
Substrate level phosphorylation
when you make ATP in the Krebs cycle
No of molecules produced in link reaction + krebs cycle
1 glucose molecule = … pyruvate
2
What else can happen in the Krebs cycle?
allow other substrates besides glucose to enter respiration e.g. fatty acids can enter the cycle by being converted to acetyl CoA, glycerol can be converted to pyruvate and enter respiration, amino acids can be converted into compounds in the Krebs cycle or into pyruvate or acetyl CoA
Oxidative phosphorylation location
Happens in the inner mitochondrial membrane
Oxidative phosphorylation steps
- Reduced NAD and reduced FAD deliver the hydrogen atom, which breaks into electrons and protons
- Electrons are captured by the electron transport chain, as the electrons pass some of their energy is used to pump protons across the inner mitochondrial membrane into the inter membrane space. This creates a proton gradient / chemiosmotic gradient.
- The protons diffuse down the concentration gradient through protein channels associated with ATP synthase enzyme. This allows ADP and Pi to combine to form ATP.
- in the matrix, oxygen acts as the final electron and proton acceptor, forming water.
Oxidative phosphorylation diagram
Net gain of ATP per molecule of glucose in stages of respiration
Yield of ATP = why’s actual different from predicted
Actual yield = 28 but predicted in 30 bc some ATP used to move the pyruvate into the mitochondria and some is used to transport the NADH into the mitochondria. Also the protons that have accumulated in the inter membrane space might leak out through the outer mitochondrial membrane so not 100% of them are used to produce ATP.
ATP made in aerobic respiration
32
What happens when there’s no oxygen in oxidative phosphorylation
- oxygen cannot act as the final proton and electron acceptor at the end of oxidative phosphorylation
- So the protons diffusing through the channels, accumulate at the matrix.
- So the proton gradient is reduced.
- Oxidative phosphorylation stops. Reduced NAD and FAD aren’t able to unload the hydrogen atoms.
- The Krebs cycle stops and then the link reaction stops.
Anaerobic respiration
- Use glycolysis to produce 2 ATP per glucose
- To do this anaerobic respiration needs NAD
- NAD needs to be regenerated because there’s no oxidative phosphorylation that recycles NAD.
Name the 2 types of stage 2 anaerobic respiration
- ethanol fermentation (plants and fungi e.g. yeast)
- lactate fermentation (humans)