3.3.3 Respiration Flashcards
What do both aerobic and anaerobic respiration start with?
Glycolysis
Where does glycolysis occur?
Happens in cytoplasm
Is glycolysis are anaerobic or aerobic process?
Anaerobic process
Name the 2 stages in glycolysis
- Phosphorylation
- Oxidation
Glycolysis
Describe what happens in phosphorylation
- Glucose is phosphorylated using phosphate from a molecule of ATP
- Creates 1 molecule of glucose phosphate and 1 molecule of ADP
- ATP is then used to add another phosphate = hexose bisphosphate
- Hexose bisphosphate is splits into 2 molecules of TP
Glycolysis
Describe what happens in oxidation
- TP is oxidised (loses H) = 2 molecules of pyruvate
- NAD collects H+ ions = 2 reduced NAD
- 4 ATP produced, but 2 used up in stage 1 ∴ net gain of 2 ATP
What happens to the products of glycolysis in aerobic respiration?
- 2 molecules of reduced NAD go to oxidative phosphorylation
- 2 pyruvate molecules are actively transported into matrix of mitochondria for link reaction
Anaerobic Respiration
Pyruvate is converted into ___ in plants and yeast
Ethanol
(Using reduced NAD)
Anaerobic Respiration
Pyruvate is converted into ___ in animal cells and some bacteria
Lactate
(Using reduced NAD)
Illustrate Alcoholic Fermentation
(i.e. write equation)
Reduced NAD reduces/donate H ions to pyruvate to ethanol
Illustrate Lactate Fermentation
Name the 4 main stages in aerobic respiration
- Glycolysis
- Link Reaction
- Krebs Cycle
- Oxidative Phosphorylation
Describe the link reaction
- Pyruvate is decarboxylated
- (1 C is removed in form of CO₂)
- Pyruvate is oxidised to form acetate
- & NAD is reduced to form reduced NAD
- Acetate is combined with coenzyme A (CoA) to form acetyl coenzyme (acetyl CoA)
- No ATP produced
2 pyruvate molecules are made for every glucose molecule that enters glycolysis. This means that the ____ _____ and _____ _____ happens _____ for every glucose molecule.
2 pyruvate molecules are made for every glucose molecule that enters glycolysis. This means that the link reaction and Krebs cycle happens twice for every glucose molecule.
After Link Reaction
For each glucose molecule, state the quantity of each product and where they go
- 2 molecules of acetyl CoA go into the Krebs cycle
- 2 CO₂ molecules are released as waste product
- 2 molecules of reduced NAD are formed and go to oxidative phosphorylation
Krebs cycle Involves a series of ________ reactions
oxidation-reduction
Where does the Krebs cycle takes place?
In matrix of mitochondria
Krebs cycle happens once for every ______ molecule & goes round 2x for every ______ molecule
Krebs cycle happens once for every pyruvate molecule & goes round 2x for every glucose molecule
Describe the Krebs cycle
- Acetyl CoA combines with 4C to form 6C
- CoA A goes back to link reaction to be used again
- 6C → 5C
- Decarboxylation occurs
- Dehydrogenation occurs
- H is used to NAD → reduced NAD
- 5C → 4C
- Decarboxylation and dehydrogenation occur, produced 1x reduced FAD & 2x reduced NAD
- ATP is produced by direct transfer of phosphate group from intermediate compound to ADP
- Called substrate-level phosphorylation
Define oxidative phosphorylation
- Process where energy carried by electrons, from reduced coenzymes (reduced NAD and reduced FAD), is used to make ATP
- Involves electron transport chain and chemiosmosis
Describe Oxidative Phosphorylation
- Reduced NAD → NAD & reduced FAD → FAD = releases H
- H atoms split into protons and e−
- e− move down electron transport chain, losing energy at each carrier
- Energy is used to pump protons from mitochondrial matrix into intermembrane space
- Conc. of protons is now higher in intermembrane space than in mitochondrial matrix
- Forms electrochemical gradient
- Protons move down electrochemical gradient into mitochondrial matrix via ATP synthase
- Movement drives synthesis of ATP from ADP and P¡
- In mitochondrial matrix, at end of transport chain, protons, electrons and O₂ (from blood) combine to form water
- O₂ = final electron acceptor
____ ATP are made from each reduced NAD and ___ ATP are made from each reduced FAD
2.5 ATP are made from each reduced NAD and 1.5 ATP are made from each reduced FAD
What do mitochondrial diseases affect?
- Affect functioning of mitochondria
- Affect how proteins involved in oxidative phosphorylation or Krebs cycle function = reducing ATP production
Describe the effect of mitochondrial diseases
- May cause anaerobic respiration to increase, to try and make up some of the ATP shortage
- = lots of lactate being produced, which can cause muscle fatigue and weakness
- Some lactate will diffuse into bloodstream = high lactate concentrations in blood
Describe how proteins can be used as respiratory substrates
- Amino acids used as respiratory substances
- Those not used for protein synthesis are deaminated in liver cells
- Remainder of molecule can be converted into glycogen or fat
- If there’s not enough carbohydrates, muscle proteins can be hydrolysed to amino acids
Describe how glycerol can be used as a respiratory substrate
Glycerol oxidised and phosphorylated into TP and then enters end of glycolysis
Describe how fatty acids can be used as a respiratory substrate
Fatty acids are broken down by process known as beta oxidation to produce acetyl CoA when then enters the Krebs cycle
What is produced a lot in beta oxidation?
Large amounts of FADH2 and NADH
Fatty acids can only be broken down _______
aerobically
Why can fatty acids only be broken down aerobically?
∵ oxygen will be required as final electron acceptor
Why do red blood cells only respire glucose?
Have no mitochondria - only respire anaerobically
(lipids and proteins require aerobic conditions)
What is the respiratory quotient
Is the ratio of CO₂ to O₂ in relation to a given respiratory substrate
Describe how RQ values can be determined experimentally
By measuring O₂ consumption and CO₂ production using a respirometer
By calculating RQ value, what can you find out?
- Substrates being used in respiration by an organism
- Type of respiration being carried out can be deduced
State the equation for calculating RQ
RQ = moles of CO₂ given out
—————————————
Moles of O₂ taken in
Work out the RQ for glucose
RQ = 6CO2
———
6O2
oxidised and phosphorylated RQ = 1
RQ < 1, it’s a ____ or ___
protein or lipid
The production of ethanol or lactate regenerates oxidised NAD. Why is this good?
- Means glycolysis can continue when there isn’t much oxygen around
- ∴ small amount of ATP can be produced to keep some biological processes going
Describe how you would investigate the effect of temperature on the rate of respiration of yeast
- Set water bath at 35°C
- Label 5 test tubes
- Shake yeast and glucose mixture
- Add 2 cm3 of yeast and glucose mixture to each test tube
- Place all test tubes in water bath and wait until their contents reach 35°C
- Add 1 cm3 of methylene blue to test tube 1
- Shake test tube for 10s
- Time how long it takes for solution to change from blue to colourless
- Repeat steps 6-8 for other 4 tubes
- Repeat steps 1-9, but use temperatures of 40°C, 45°C, 50°C, 55°C
Explain why methylene blue changes from blue to colourless
- During aerobic respiration, transport of electrons is linked to synthesis of ATP
- Electrons are taken up by methylene blue
- When methylene blue is reduced, changes from blue to colourless
What is a respirometer is used for?
Used to indicate rate of aerobic respiration by measuring amount of oxygen consumed by organism in one period of time
Respirometer
What happens to the volume of air in test tube with e.g. woodlice & why?
- Volume of air decreases due to oxygen consumed during respiration
- All CO₂ absorbed by potassium hydroxide
Respirometer
What happens when the volume of air in the test tube with e.g. woodlice decreases (as oxygen is taken up)?
- Decrease pressure in test tube
- Causes coloured fluid in capillary tube of manometer to move toward it
Describe what happens to reduced NAD produced in Krebs cycle (3)
- Enters mitochondria
- NADH → oxidised to NAD
- Used to produce ATP
Describe the part played by the inner membrane of mitochondrion in producing ATP (3)
- electrons transferred down electron transport chain
- provides energy to take protons into intermembrane
- protons pass through membrane, ATP synthase
Glucose _______ ______ the mitochondrial _______
Glucose cannot cross the mitochondrial membrane
Human synthesise more than their body mass of ATP each day. Explain why it is necessary for them to synthesise such a large amount of ATP. (2)
- ATP cannot be stored/is an immediate source of energy
- ATP only releases a small amount of energy at a time
What measurements should the student have taken to calculate the rate of aerobic respiration in mm3 of oxygen g-1 h-1 (3)
- Distance (drop moves) and time
- Mass of organism
- Diameter of tube
Draw Glycolysis. Include no. of carbon.
Draw the Link Reaction. Include no. of carbon.
Draw the Krebs Cycle. Include no. of carbon.
The mitochondria in muscles contain many cristae. Explain the advantage of this. (2)
- Larger surface area for oxidative phosphorylation
- Provide ATP / energy for contraction
Explain why cells gain more energy from lipid than from carbohydrate (3)
- More H in lipid
- More protons so more reduced FAD/NAD/(more protons) move across inner mitochondrial membrane
- More ATP produced
- More electrons moving down ETC
Explain why less energy is released in anaerobic respiration (1)
Glucose only partly broken down/broken down to lactate
At the end of a sprint race, a runner continues to breathe rapidly for some time. Explain the advantage of this. (2)
- Lactate built up
- Oxygen used to break down lactate/convert it back to pyruvate
Respiration Experiment
State how temperature could be controlled
Using a water bath
Respiration Experiment
State how pH could be controlled
Using a buffer solution
Explain why the scientist adds pyruvate rather than glucose to the isolated mitochondria (2)
- Glycolysis occurs in cytoplasm
- Glycolsis produces pyruvate
Explain why muscles become fatigued when insufficient oxygen is available (2)
- build up / increased concentration of lactate lowers pH / increases H / increases acidity
- enzymes / named protein inhibited(not denatured)
