Respiration Flashcards
Where glycolysis fits in the overall process of respiration
-Glycolysis is the first stage of aerobic and anaerobic respiration
-occurs in cytoplasm of the cell
Process of glycolysis
1) glucose converted into phosphorylated glucose by hydrolysis of 2x ATP molecules to ADP (provides energy to activate glucose
and lowers AE for enzyme controlled reactions that follow)
2) Phosphorylated glucose split into 2X triose phosphate (3C molecule)
each triose phosphate oxidised (H removed from each of 2 triose phosphate and transferred to H carrier molecule AKA NAD > NADH
3) enzyme controlled reactions convert each triose phosphate into another 3C molecule (pyruvate) so 2 molecules of ATP are regenerated from ADP
Where does glycolysis occur?
cytoplasm
What is glycolysis involved in?
aerobic AND anaerobic respiration
What are the end products of glycolysis?
-net gain of 2 x ATP
-2 x reduced NAD (NADH)
-2 x pyruvate
How many ATP are hydrolysed for the phosphorylation of glucose?
2
Why does glucose phosphate split?
it is unstable
For 1 GLUCOSE molecule, how many ATP are produced (in the oxidation of triose phosphate(s))
4 (2 per TRIOSE PHOSPHATE)
What is NAD converted into in the oxidation of triose phosphate to form pyruvate?
NADH (2 per GLUCOSE)
How many pyruvate are made for each glucose molecule?
2
What is produced in glycolysis and is needed in the next stages of respiration?
-NADH
-PYRUVATE
How are pyruvate and NADH transported into the mitochondrial matrix?
active transport
Process of link reaction
-pyruvate molecule from glycolysis diffuses from cytoplasm across mitochondrial membrane into mitochondrial matrix
-pyruvate (3c) is oxidised (and decarboxylated) to acetate (2c molecule) so CO2 is produced as a by-product and the 2H lost from pyruvate is accepted by NAD>NADH to be used in ATP later on (in anaerobic resp)
-acetate combined with coenzyme A (CoA) to produce acetyl coenzyme A (2c molecule)
Why does links reaction happen
so pyruvate from glycolysis can be oxidised first before entering kerbs cycle
What reaction makes acetate?
the oxidation of pyruvate
What are the products of the oxidation of pyruvate?
acetate and NADH and CO2
What is produced overall in the link reaction? (per glucose)
2 x Acetyl CoA
2 x NADH
2 x CO2
What is the job of coenzyme A?
to deliver the acetate so it can react with a 4-carbon compound
Process of kerbs cycle
-Takes place in mitochondrial matrix and involves a series of redox reactions
- acetyl CoA from link reaction combines with 4 c molecule, releasing coenzyme A and producing 6c molecule
-in a series of reactions, 6 c molecule loses co2 and H to give 4C molecule
-H+ being lost means coenzymes NAD and FAD are reduced
- 1ATP (adp +pi ) produced as a result of substrate level phosphorylation
-remaining 4c molecule is available t combine with new molecule of acetyl-co-enzyme A a to being cycle again
from each molecule of pyruvate linsk and klerbs produce:
-reduced co enzymes > NADH and FADH > these have potential to provide energy to produce ATP molecule by oxidative phosphorylation so they’re important in kerbs
-one molecule of atp
-3 molecules of co2
roles of coenzymes
-important in carrying H atoms from one molecule to another e.g.
-NAD > important in respiration
-FAD > important in kerbs
-NADP > important in photosynthesis
Why is NAD most important carrier
-works with dehydrogenase enzymes that catalyse removal of H atoms from substrates and transfer them to other molecules involved in oxidative phosphorylation
Significance of Kerbs cycle
-breaks down macromolecules into smaller > pyruvate broken down into co2
-produces H atoms that’s carried by NAD to e- transfer chain > provide energy for oxidative phosphorylation >leads to production of ATP of ATP for metabolic energy for cells
-regenerates 4C molecule that combines with acetyl coenzyme A which would otherwise accumulate
-source of intermediate compounds used by cells in manufacture of other important substances eg fatty acids, amino acids and chlorophyll
Products per glucose of kerbs cycle
useful = 6x NADH
2X FADH
2X ADP
waste = 4x CO2
Products per cycle of kerbs cycle
3x NADH
1X FAD
1x ATP
2x CO2
nature of hydrogen carrier molecules and its role in kerbs cycle
-hydrogen carrier molecules in respiration are co enzymes (molecules that some enzymes require in order to function).
-The molecules specific to Krebs
cycle are FAD and NAD, which work with dehydrogenase enzymes to remove hydrogen atoms from substrates and transfer them to the molecules involved in oxidative phosphorylation.
Process of oxidative phosphorylation
-occurs in the cristae
-NADH and FADH from kerbs, linked and glycolysis are oxidised to release H atoms and split into H+ and e-
-in a series of redox reactions, e- are transferred down e- transfer chain. as e- decrease in energy levels, energy is released
-energy that is released allows active transport of H+ across inner mitochondrial membrane into intermembranal space
-H+ diffuse by facilitated transport into matrix down electrochemical gradient via ATP synthase channel (embedded in inner mitochondrial membrane). so there’s a high conc of H+ in intermembrane space and lower conc in matrix
-releases energy to synthesise ATP from ADP + Pi
-in matrix, at the end of electron transport chain, oxygen is the final electron acceptor (e- can’t pass along otherwise), so protons, electrons and oxygen combine to form water
mechanism of oxidative phosphorylation
some of energy of e- within H atoms is conserved in formation of ATP
What is the energy released (in the electron carrier chain) used for?
actively transporting H+ out of the matrix into the inter-membrane space
What happens to the electrons that are released in OP
they travel along an electron transport chain which releases energy
Anaerobic respiration
-pyruvate converted to lactate (animal cells and some bacteria) or ethanol (+co2 in plants and yeast)
-oxidising NADH > NAD is regenerated
-so glycolysis can continue (which needs NAD), allowing continued production of ATP
How do protons move back into the matrix?
facilitated diffusion through ATP synthase
What does ATP synthase do?
Phosphorylate ADP to form ATP
What does oxygen pick up in this step?
electrons and H+ ions, forming H2O
What is oxygens role in respiration?
it is the final electron acceptor and will form water
Why is NAD and FAD not transferred in one explosive step
-when energy is released a little at a time
-more of it can be harvested for benefit of organism
-transfer of e- down energy gradient allows their energy to be released gradually and more usefully
respiration of lipids
1) lipids hydrolysed to glycerol and fatty acids
2) glycerol is then phosphorylated and converted to triose phosphate which enters glycolysis pathway and kerbs
3) fatty acid component is broken down into 2C which are converted to acetyl co enzyme A
4) this enters kerbs cycle
production of oxidation of lipids
- 2C fragment of carbohydrate and many H atoms
-H atoms used to produce ATP during oxidative phosphorylation - so lipids release more than double energy of same mass of carbohydrate
respiration of protein
1) hydrolysed to constituent amino acids
2) have amino group removed (deamination) before entering respiratory pathways at different points depending on number of c atoms they contain
- 3 c compounds converted to pyruvate
- 4 and 5 c compounds converted to intermediates in kerbs
