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)
What needs to be generated to keep glycolysis going
NAD
Net product of anaerobic respiration
2 ATP per glucose used
Lactate fermentation
What happens to lactic acid + why
Lactic acid can lower the pH and cause the enzymes to denature so instead the lactate produced in the muscles is carried to the liver which contains enzymes (lactate dehydrogenase) that make it into pyruvate or into glucose
Ethanol fermentation
- when the pyruvate you make gets converted into ethanol
Why’s ethanol fermentation not sustainable for fungi
- if performed for too long the fungi ends up dying
Facultative anaerobe:
if oxygen’s available it will be aerobic, if oxygen isn’t available it’ll become an anaerobic organism
Substrates for respiration and difference between them
Carbohydrates, lipids and proteins
Each of them have different energy value
Main substrate for respiration
Carbohydrates (specifically glucose)
Other carbs usually get broken down into glucose or converted into glucose
Lipids as substrates in respiration
triglyceride’s glycerol component can be converted into TP. and fatty acids are a good source of energy due to the c-h bond
Proteins as substrates in respiration
made of amino acids which can enter the Krebs cycle or diff stages of respiration.
Lipids have sm more energy than other substrates
Respiratory quotient
Fatty acids RQ
0.7
Proteins RQ
0.8/0.9
Glucose RQ
1
How to tell if anaerobic respiration is taking place via the RQ
if overall RQ is more than 1 that means anaerobic respiration is taking place
Respirometer
- one side put organism THATS gonna respire and other side put same mass but in beads
- Organism respires using oxygen + you can see the meniscus changing
- If the meniscus moves towards the side w the organisms that means it’s respiring
Respirometer diagram
Facilitated diffusion - conversion of ornithine into citrulline creates concentration gradients
Oxygen will leak from the connectors so reduce the gas movement
Temperature = use water bath and thermometer to stabilise temperature
Describe how you would add the red fluid to the capillary tube at the start of the experiment.
dipped into a small beaker and allowed to run
Slow metabolic rate
Which amino acid would have the highest RQ
One w highest proportion oxygen atoms
B
The percentage of carbon atoms that a reaction makes available for use in the Krebs cycle can be
described as the efficiency of the reaction. Calculate the efficiency of the link reaction
ii
Substrate level phosphorylation
Coenzyme A = transfers acetyl from link reaction to Krebs cycle
NAD = oxidation of pyruvate in link reaction, oxidation of intermediates in Krebs cycle, addition of electrons to electron transport chain, reduction of pyruvate in lactate fermentation
FAD: oxidation of intermediates in Krebs cycle
What’s R
Krebs cycle
What properties of the mitochondrial inner membrane allow chemiosmosis to occur?
Impermeable to protons
Large surface area
Describe two quantitative changes in inter membrane space which occur as a result of oxidative phosphorylation.
pH decreases and becomes more positively charged
Outline the processes involved in the generation of ATP through chemiosmosis.
Occurs in mitochondria
Involved inner membrane and matrix
Involves movement of hydrogen across membrane
Use of atp synthase
H+ ions pumped out of matrix across membrane in inter membrane space = creates chemiosmotic gradient
Diffuses back to matrix via channel proteins associated ATP synthase - producec ATP from ADP + Pi
H+ ions move from area of high concentration to low concentration (down concentration gradient)
Aseptic techniques
Provide nutrients
Incubate at suitable temp
Use pH buffer
What does the word anaerobic suggest about the bacterium
It respires in the absence of oxygen
It hydrolyses a peptide bond between two amino acids which are joined by a disulfide bond
Role of Pyruvate in anaerobic respiration
Hydrogen acceptor = removed hydrogen from NADH
Why does cheese have the highest energy content compared to other food
High in fat = highest kcal/100g
Fatty acids have many H atoms
Produce many NADH in Krebs cycle
The student concluded the following from the graph:
• The rates of respiration with glucose, maltose and sucrose were very Similar.
• The yeast could not hydrolyse disaccharides.
Evaluate the student’s conclusions.
Supporting = slope of each curve similar
Against = glucose respiration begins sooner than maltose = lag before maltose + sucrose respiration begins
Supporting = no lactose respiration = is a disaccharide and not hydrolysed
Against = maltose + sucrose are disaccharides and are respired
Stir yeast solution
Check temperature of water bath is 35 degrees Celsius
