Respiration Flashcards
What processes require energy
- Movement e.g. flagella and muscle contraction
- Cell division and growth
- Anabolic processes e.g. synthesis of polysaccharides
- Catabolic processes
- Maintaining constant body temp
- Active transport
- Bioluminescence e.g. glow worms
- Secretion e.g. insulin in pancreas
Whats the role of ATP
- Short term energy store of cell
Describe the structure and full name of ATP
- Adenine (base)
- Ribose (pentose sugar)
- 3 phosphate groups
- Adenosine triphosphate
How does ATP release energy
- 3 phosphate groups joined by 2 high energy bonds
- ATP hydrolysed to break a bond releasing a large amount of energy
- Hydrolysis of ATP to ADP (later to AMP) is catalysed by enzyme ATPase
Outline the process of glycolysis
- Occurs in cytoplasm
- First stage of both aerobic and anaerobic respiration
- Glucose is phosphorylated to form Glucose-6-phosphate as ATP is hydrolysed to form ADP
- Next Glucose-6-phosphate is changed to Fructose-6-phosphate
- Then Fructose-6-phosphate is phosphorylated to form Hexose-1,6,-bisphosphate (ATP hydrolysed to ADP)
- Each molecule of hexose is split into two triose phosphates
- Two H atoms removed from each triose phosphate (dehydrogenase enzyme) - aided by coenzyme NAD which reduced to NADH and two ADP used to form two ATP
- Two intermediate compound formed and four enzyme catalysed reactions convert each into a molecule of pyruvate and two ADP phosphorylated to two ATP.
Describe the role and structure of the outer membrane in mitochondria
- A barrier that stops entry of large molecules that could interfere with Krebs cycle and oxidative phosphorylation
- Pyruvate can pass freely into matrix
Describe the role and structure of the inner membrane in mitochondria
- Holds both electron carriers and ATP synthase molecules.
- Prevents small molecules from cytoplasm from entering matrix
- Pyruvate passes freely
Describe the role and structure of the inter membrane space in mitochondria
- Activity of electron carriers in the inner membrane causes a reservoir of H+ to build up in the space as a temporary energy store before being used to make ATP
Describe the role and structure of the crista in mitochondria
- Inner membrane largely folded to create large SA to hold electron carriers and ATP synthase molecules
Describe the role and structure of the matrix in mitochondria
- Where enzymes of the Krebs cycle are found
- Krebs cycle removes electrons from the intermediates of the cycle and produced reduced NAD and FAD
Describe the role and structure of the ATP synthase in mitochondria
- Molecule that makes ATP from ADP and P using energy from electrons obtained from reduced NAD and FAD
- Molecules span the inner membrane and have channels that allow H+ ions to pass through
Outline the link reaction
- Occurs twice per glucose and no ATP involved
- Occurs in matrix
- CO2 is released in a decarboxylation reaction catalysed by pyruvate decarboxylase to produce a molecule of acetate
- This immediately combines with coenzyme A to produce acetyl CoA and carry it to Krebs cycle
- A molecule of NAD is reduced to form NADH, by pyruvate dehydrogenase
Outline the Krebs Cycle
- Acetate combines with oxaloacetate to form citrate
- Citrate is decarboxylated and dehydrogenated to form a 5C compound releasing CO2 and NADH
- 5C compound is decarboxylated and dehydrogenated to form a 4C compound releasing CO2 and NADH
- ATP is released under substrate level phosphorylation to form another 4C compound
- 4C compound is dehydrogenated releasing FADH to form another 4C compound
- The 4C compound is dehydrogenated, releasing NADH
Describe the importance of coenzymes
- coenzymes to transfer protons, electrons and functional groups
- coenzymes mostly derived from vitamins hence why vitamins are essential micronutrients
Describe the differences between NAD and FAD
- NAD takes part in all stages of cellular respiration but FAD only accepts hydrogens in the Krebs cycle
- NAD accepts one H whereas FAD accepts two
- reduced NAD oxidised at start of electron transport chain releasing protons and electrons whereas reduced FAD is oxidised further along the chain
- Reduced NAD results in synthesis of three ATP molecules but reduced FAD results in synthesis of only two ATP molecules
Outline the process of oxidative phosphorylation
- NADH releases its H which dissociates into H+ and e- (high energy electrons)
- The e- transported between e- carriers found within four protein complexes on IMM (cristae)
- The e- transfer between e- carriers releases a small amount of energy which is used to pump the H+ from the matrix into the IMM
- The H+ build up in the IM space creating a electrochemical gradient
- H+ flow down the electrochemical gradient through ATP synthase
- The movement of H+ thru ATP synthase creating a proton motive force causing head of ATP synthase to rotate allowing it to add Pi to ADP creating ATP
- H+ and e- rejoin in matrix and combine with O2 (final e- acceptor) to produce H2O
Outline the process of chemiosmosis
- The ATP produced in respiration is synthesised primary by chemiosmosis
- It involves the diffusion of protons from region of high conc to low conc through partially permeable membrane
- The movement of protons as they flow releases energy that is used in the attachment of an inorganic phosphate (Pi) to ADP forming ATP
- This depends on the creation of a proton conc gradient and this energy comes from high-energy electrons
Why is the theoretical yield of ATP per glucose rarely ever achieved?
- Some of the NADH formed between glycolysis and the Krebs cycle is used in other reduction reactions in the cell rather than in oxidative phosphorylation
- Some ATP used up in actively transporting substances such as pyruvate, ADP and Pi into the mitochondria during respiration
- The inner membrane of the mitochondria is leaky - some protons leak into the matrix without passing through ATP synthase and without making ATP
Why does anaerobic respiration produce a much lower yield of ATP than aerobic respiration
- Only ATP made in anaerobic respiration is in glycolysis
Contrast anaerobic respiration in mammals and in yeast
MAMMALS:
- pyruvate hydrogenated to lactate (lactate dehydrogenase)
- NADH oxidised to NAD
YEAST:
- Pyruvate is decarboxylated by pyruvate decarboxylase by releasing a molecule of CO2 producing ethanal
- Ethanal hydrogenated by ethanol dehydrogenase and NADH is oxidised to NAD to produce ethanol
State the similarities of anaerobic respiration in mammals and yeast
BOTH:
- start with glycolysis
- no final electron acceptor
- H+ conc in matrix increases so electrochemical gradient reduces
- Oxidative phosphorylation stops
- NADH and FADH can’t be oxidised
- Link reaction and Krebs cycle stop
Why are glass beads needed in the container with the dry beans in an investigation of respiration
- Dry beans take up less room than the germinating beans
- There should be a constant volume
