5.2.2 Respiration Flashcards
What is ATP composed of?
- A nitrogenous base - Adenine
- A pentose sugar - Ribose
- Three phosphate groups
What is meant by ATP being a universal energy currency?
It is used for energy transfer in all cells of all living organisms
Full name of ATP
Adenosine triphosphate
Why is ATP not a good long term store of energy?
The phosphate bonds are not stable
Main Aspects of ATP
- Transfer energy/energy currency
- Phosphates removed by hydrolysis
- 30.6kJ released per mole of ATP molecules
- Phosphates added via chemiosmosis - ADP + Pi = ATP
- ATP released in small packets that don’t damage the cell
How is energy released from ATP?
When a phosphate is removed by hydrolysis
Uses of ATP in the cell
- Active transport
- Muscle contraction
- Glycolysis
- Protein synthesis
- DNA replication
- Secretion
- Endocytosis
Properties of ATP
- Small - moves easily into + out of cells
- Water soluble- Energy requring proccesses take place in aqueous solution
- Energy contained in bonds between phosphates is large enough for cell reactions but not too big that energy would be lost as heat
- Releases energy in small quantities
- Easily regenerated
How is ATP created and turned into ADP?
Creation of ATP
- ATPsynthase
- ADP + Pi = ATP
- Condensation reaction = H20 made
Creation of ADP
- ATPase
- ATP - Pi = ADP
- H20 used
- Hydrolysis reaction = H20 used
What is respiration
The process by which organic molecules are broken down in a series of stages to synthesise ATP
How does temperature affect enzyme controlled reactions?
Below optimum = enzyme + substrate have less kinetic energy = less collisions with active site = less ESCs formed per second
Above optimum = enzymes denature = substrates can’t fit into active site = Fewer ESC’s created
Word equation for respiration
Glucose + Oxygen = Carbon dioxide + Water + Energy
Balanced symbol equation for respiration
C6H1206 + 602 = 6C02 + 6H20 + (ATP)
What coenzymes are used in respiration?
NAD, FAD, Coenyzme A
Where are NAD, FAD + Co-enzyme A used?
NAD
- Hydrogen acceptor in glycolysis, link reaction + krebs cycle
Reduced NAD
- A hydrogen supplier for oxidative phosphorylation
- An electron supplier for oxidative phosphorylation
Coenzyme A
- Carries acetate to Krebs cycle
FAD
- Similar to NAD but only used in Krebs cycle
Reduced NAD + reduced FAD used to make ATP
Stages of respiration
- Glycolysis
- Link reaction
- Krebs cycle
- Electron transport chain
Where does glycolysis take place?
Cytoplasm of cells
What happens in glycolysis?
1 molecule of glucose split into 2 molecules of pyruvate
- Doesn’t require oxygen
- First stage of anaerboic + aerobic respiration
Explain the composition of glucose and pyruvate
- Glucose = Hexose sugar
- Pyruvate = Triose molecule (also called pyruvic acid)
Explain the stages of Glycolysis
Stage 1: Phosphorylation
1. 2 ATP molecules hydrolysed to release 2 phosphates
2. Phosphates added onto glucose to make Hexose -1,6-biphosphate
Stage 2: Splitting of Hexose 1,6-biphosphate
1. Each molecule split into 2 triose phosphate
Stage 3: Phosphorylation of triose phosphate
1. A phosphate from the cytoplasm is added to each triose phosphate molecule to form 2 triose biphosphates
Stage 4: Oxidation and formation of ATP
1. The two triose biphosphate molecules are oxidised by removal of hydrogen atoms to form 2 pyruvate molecules
2. NAD accepts hydrogens, forming reduced NAD
3. 4 ATP molecules produced using phosphates from the triose biphosphates
By what process is ATP created in glycolysis?
Substrate level phosphorylation
ATP is made without an electron transport chain
ATP formed by transfer of phosphate group from a phosphorylated intermdiate (triose biphosphate) to ATP
Why is pyruvate able to enter mitochondria but glucose isn’t?
Mitochondrial membrane contains protein carriers that allow pyruvate to enter
Mitochonddriah as no specific protein carreirs for glucose in it’s membrane
What are the net products of glycolysis
2 x Reduced NAD
2 x ATP
2 x Pyruvate
Explain the structure of the mitchondira and where each other stage of respiration takes place
Structure
- 2 phospholipid membranes (outer + inner)
- inner membrane folded into cristae - increases SA
- cristae separates matrix from intermembrane space
Locations
- link reaction + krebs cycle take place in matrix
- oxidative phosphorylation in cristae + intermembane space
What proccess occurs in the link reaction?
Oxidative carboxylation
Brief overview of link reaction
- takes place in matrix of mitochondria
- pyruvate oxidised, removing hydrogen (NAD to reduced NAD)
- Co2 made and released
- 2c molecule created (acetyl group)
- acetyl group + coA combine to make Acetylcoenzyme A
Explain the 4 stages of the link reaction
- Pyruvate loses 1c as CO2 (decarboxylation by pyruvate decarboxylase)
- Pyruvate oxidised by removal of hydrogen by NAD (forming reduced NAD)
- 2c molecule acetate left
- Combines with CoA to form Acetly CoA
Products of link reaction
2 x Acetyl CoA
2 x reduced NAD
2 x CO2
NO ATP
Where does the krebs cycle take place and what proccesses does it involve?
Location
Matrix of mitochondria
Processaes
Breakdown of an acetly group
- decarboxylation
- dehydrogenation
- substrate level phosphorylation
- involves NAD + FAD
Explain the stages of the krebs cycle
- Acetate(2c) joins Oxaloacetate (4c) to form Cirate (6c) - CoA released to be used in the link reaction
- Citrate decarboxylated + dehydrogenated (Co2 removed + reduced NAD made)
- 5c compound decarboxylated + dehydrogenated (Co2 removed + reduced NAD made)
- 4c compound - ATP made (substrate level phosphorylation) + NAD & FAD further dehydrogenation
- Oxalocetate created
What are the products of the krebs cycle one time?
3 x reduced NAD
1 x reduced FAD
1 x ATP
2 x CO2
Compare NAD + FAD
Similarities
- Both are coenzymes
- Both accept hydrogen
- Both used in the krebs cycle
Differences
- FAD only in krebs vs NAD in all stages
- NAD accept 1 H vs FAD accepts 2
- Reduced NAD oxidised at start of electron transport chain vs Reduced FAD oxidised further along the chain
- Reduced NAD results in 3 ATP molecules
- Reduced FAD results in synthesis of 2 ATP molecules
What does the cristae surface contain?
Electron carriers + ATP synthase
Electron carriers contain Fe3+ haaem group that accepts electrons (reduction) to become Fe2+ and losaes electrons to be Fe3+ (oxidation
H+ protons move down proton gradient through ATPsynthase to create ATP
Explain the stages of oxidative phosphorylation
- Reduced NAD combines with proten complex 1 (NADH dehydrogenase)
- NAD is resused in glycolysis, link reaction + krebs cycle
- Hydrogen atoms donated become 2H+ & 2e-
- The 2e- pass along electron transport chain providing energy to pump more H+ into intermembrane space
- Reduced FAD oxidised at 2nd complex but H+ remain in matrix to combine with O2 to form water
- More H+ pumped into intermembrane space due to electron movement
- Proton gradient formed so H+ moves down through ATP synthase enzyme (chemiosmosis)
- 2H+ combine with two H+ + 4e- + oxygen to form water (O2 is final electron acceptor)
- H+ passing through ATP synthase causes rotation to join ADP + Pi to make ATP
Define oxidative phosphorylation
Production of ATP using oxygen as the final electron acceptor in an electron transport chain
Define chemiosmosis
Diffusion of protons from a high concentration to a low concentration through a partially permeable membrane, releasing energy to make ATP
Define the electron transport chain
A series of electron carriers weach with progressively lower energy levels
Total amount of molecules made from 1 glucose molecule
- 10 NADH
- 2 FADH2
- 6 CO2
- 4 ATP
How much reduced NAD + reduced FAD is used to create ATP?
1 reduced NAD = 3 ATP
10 x 3 = 30 ATP
1 reduced FAD = 2 ATP
2 x 2 = 4 ATP
(+4 ATP from substrate phosphorylation in glycolysis + krebs)
38 total ATP molecules for every 1 glucose
Why can’t the entireity of respiration occur in anaerobic conditions?
- no oxygen (final electron acceptor)
- reduced NAD can’t be oxidised back to NAD
- NAD not available for use in glycolysis, link reaction & krebs
- no synthesis of ATP by chemiosmosis
How is ATP produced anaerobically?
Only made by substrate level phosphorylation in glycolysis
Where and how does fermentation take place?
Alcoholic fermenattaion: Yeast + plants, producing ethanol
Lactate fermentation: Mammals, producing lactate (cramps in muscles)
How is NAD regenerated so glycolysis can continue?
Hydrogen acceptor used
Humans:
Lactate dehydrogenase reversible glycolysis reaction (no atoms lost)
Yeast:
Pyruvate decarboxylase - CO2 lost to air - one direction
How does alcoholic fermentation work?
- non reversible
- pyruvate converted to ethanol
- ethanol acceptrs hydrogen atom to frorm NAD + ethanol made
- NAD can continue to act as conezmye - glycolysis can continue
- no ATP made in conversion of pyruvate to ethanol
How does lactate fermentation work?
- pyruvate acts as hydrogen acceptor - takes hydrogen from reduced NAD
- pyruvate converted to lactate by lactate dehydrogenase
- NAD regenerated
- oxygen debt created to convert lactate back to glucose in liver
What molecules can be respired?
- fats
- proteins
- carbohydrates
- proteins
How are proteins used in respiration?
- made from amino acids which have more hydrogens for NAD to accept using oxidative phosphorylation
- once proteins are hydrolysed into amino acids they are deanimated
- amino acids broken down into keto acids which then form pyruvate
- pyruvate used to make AcetylCoA in link reaction
How are triglycerides used in respiration?
- made from glyercol + fatty acids which have many hydrogens
- lipase enzyme hydrolyses triglycerides into glycerol + fatty acids
- glycerol converted to pyruvate before oxidative phosphorylation
- fatty acids have to go through beta oxidation
What is beta oxidation?
CoA added to each fatty acid to form many 2c acetyl coenzymes
What molecule has ther most energy content and where is this used?
Lipids
Seen in seeds to provide energy in form of ATP for germination
Why is the ratio of carbon to hydrogen atoms important in respiratory substrates?
Hydrogen atoms attached to NAD + FAD
More hydrogen aroms = more NAD/FAD + more hydrogen ions travelling through ATP synthase
More energy released to form ATP from ADP +Pi
How is respiratory quotient (RQ) calculated?
Volume of cargbon dioxide produced / volume of oxygen consumed
RQ for each respiratory quotient and why?
Lipids
- ratio of H+ to C much higher than carbs
- more ATP produced
- more O2 required to breakdown
- releases less carbon dioixde
- RQ less than 1.0
- RQ is 0.7
Protein
- Slightly hifgher tha carbs
- rarely used - last resort
- RQ is 0.9
How is rate of respiration measured?
Volume of Co2 produced in givem time (Cm3 Min-1)
Volume of oxygen used in given time (Cm3 Min-1)
What apparatus used to measure Co2 production?
- water bath at constant temperature
- contains test tubve of yeast + sugar solution
- delivery tube laving leads into inverted measuring cylinder
- cylinder measures volume of CO2 gas
- cylinder located in trough of water
Why are experiments repeated?
- identify + remove anomalous results (reduce imapct of anomalies)
- measure + increase repeatab ility
- calculat a mean
- standard deviation + statistical test
- improves confidence in results
Advantages of using data logging equipment
- greater degree of precision
- small percentage error
- produces quantitative not subjective data
- results stored for later use + processing
- time intervals more frequent + continous readings taken
What apparatus is used to measure rate of oxygen uptake?
Respirometer
1. Organisms placed in tube + non-living material of same mass in other tube
2. Soda lime placed ineach to absorb CO2
3. Cotton wool used to prevent contact of soda lime with organisms
4. Coloured liquid poured into resivouir of each manometer + flows into capulary tube
5. No air bubbles + same volume used in each manometer
6. Rubber bungs fitted + spring clips closed
7. Open spring clips so pressure is equal to atompsheric pressure
8. Close clips
9. Each minute record levels of fluid in each tube
10. As organisms respire, O2 is removed from the air + CO2 given out
11. Removal of O2 from air reduces volume + pressure causing manometer fluid to move trowards organisms
12. Manometer fluid in tube will not move but organism tube will
13. Calculate mean distance moved per minute (Can calculate gas volume if know radius of tube)
How can a respirometer be used to investigate ther effect of temperature on the rate of respiration?
- placed in water baths at different temperatures
- same respirometer used for whole experiment
- each temp requires control respirometer with no organisms in it
