Respiration Flashcards
Describe the process of glycolysis
- First stage of aerobic and anaerobic respiration
- Occurs in cytoplasm
Phosphorylation:
- Glucose is phosphorylated to glucose bisphosphate (unstable) by adding 2 phosphates from 2 ATP
- This splits into 2TP
Oxidation:
- TP is oxidised (loses phosphate + H) to form 2 pyruvate
- NAD collects H+ ion forming 2 reduced NAD
- 4 ATP produced but net gain of 2 ATP
Describe the process of the link reaction
- Occurs in the mitochondrial matrix
- CO2 + H+ is removed from pyruvate producing acetate
- Acetate combines with coenzyme A to form acetylcoenzyme A (acetyl CoA)
- Link reaction occurs twice for every glucose molecule so produces:
- 2 reduced NAD
- 2 CO2 released
- 2 acetyl CoA
Describe the process of the krebs cycle
Occurs in mitochondrial matrix
- AcetylCoA reacts with a 4C molecule, releasing CoA, to form a 6C sugar (Coenzyme A goes back to link reaction)
- 6C sugar is decarboxylated + dehydrogenated (CO2 is removed + 2H+ ions are used to reduce 2 NAD
- This forms a 5C molecule + a phosphate is removed + used to generate ATP
- It’s then decarboxylated + dehydrogenated again to produce a 4C molecule, another CO2 + reduced NAD
- 4C compound is dehydrogenated again + 2H+ ions reduce FAD
What are the products of the kerbs cycle?
For each molecule of glucose the krebs cycle turns twice producing:
- 4CO2
- 6 x reduced NAD
- 2 x reduced FAD
- 2 x ATP
What is oxidative phosphorylation?
Occurs within folded inner membrane (cristae)
- Process where energy carried by electrons from reduced NAD + FAD is used to make ATP (relies on chemiosmotic theory)
Chemiosmosis- states that energy in a chemical gradient established by electron movement is used to generate ATP
Describe the process of oxidative phosphorylation
- When reduced NAD + FAD are oxidised they release H+ ions which split into protons + electrons
- Excited electrons pass along ETC through a series of redox reactions, releasing energy
- Energy is used to actively transport protons from matrix into intermembrane space (creates electrochemical gradient)
- They diffuse back down their conc gradient by facilitated diffusion through ATP synthase which combines ADP + Pi to produce ATP
- The electrons, protons + oxygen (from the blood) combine to form water
-O2 is the final electron acceptor
How much ATP is produced from the ETC?
Each reduced NAD can produce 2.5 ATP + each reduced FAD can produce 1.5 ATP
Glycolysis- 2 x reduced NAD = 5 ATP
Link Reaction- 2 x reduced NAD = 5 ATP
Krebs cycle- 6 x reduced NAD = 15 ATP
Krebs cycle- 2 x reduced FAD = 3 ATP
Total ATP produced in ETC = 28 ATP
How much ATP is produced in respiration in total?
-4 ATP produced in glycolysis (net gain of 2)
-2 ATP produced from 2 turns of krebs cycle
+ the 28 ATP produced in ETC
RESPIRATION TOTAL = 32 ATP
Respiration is only about 32% efficient as:
- Some ATP is used up moving hydrogen from reduced NAD made during glycolysis into mitochondria
-Some ATP is used up moving pyruvate into mitochondria by active transport
- Some energy is used to generate heat
How can lipids be used as a respiratory substrate?
-Lipids first hydrolysed into glycerol + fatty acids
-Glycerol is phosphorylated + converted into TP which enters glycolysis pathway + krebs cycle
-Fatty acids are broken down into 2-carbon fragments which are converted into acetylcoenzyme A which enters krebs cycle
How can proteins be used as a respiratory substrate?
-Hydrolysed into amino acids
-Amino group is removed (deamination) before entering respiratory pathway at different points depending on number of carbon atoms they contain
-3C - converted to pyruvate
- 4/5C - converted into intermediates in krebs cycle
Describe anaerobic respiration in animals
The pyruvate produced in glycolysis is reduced to form lactate in animals by gaining the hydrogen from NADH
This oxidises NAD so it can be reused in glycolysis + ensure more ATP is continued to be produced
What happens to the lactate produced in anaerobic respiration?
Lactate us transported to the liver via the bloodstream where its oxidised to pyruvate
It can then enter the link reaction in liver cells or be converted to glycogen
Describe anaerobic respiration in plants + microbes (yeast)
Pyruvate produced in glycolysis is decarboxylated to form ethanal. Ethanal is reduced to ethanol using NADH
This oxidises NAD so it can be reused in glycolysis + ensure more ATP is continued to be produced
Practical 9 - explain why the liquid would move towards the left
The respiring maggots take in O2 from the air in the experimental tube. The CO2 produced is absorbed by the soda lime. Therefore the volume of gas decreases in the experimental tube, causing a decrease in pressure. The pressure in the experimental tube is lower than control tube therefore the coloured liquid will move towards the experimental tube
Practical 9- How do you calculate rate of respiration?
Rate = volume/(mass x time)
