5.2 Respiration Flashcards
What is aerobic respiration?
the process of breaking down a respiratory substrate in order to produce ATP using oxygen
What are the 4 stages of aerobic resp?
- glycolysis
- link reaction
- kreb’s cycle
- oxidative phosphorylation
Where does glycolysis take place?
in the cytoplasm of the cell
What stage of aerobic resp is actually classed as anerobic resp?
glycolysis
Why is glucose not direclty used in aerobic resp?
it would release too much energy for cells which would raise the temp in cells and cells would die
From 1 molecule of glucose how many ATP is produced?
38
What type of phosphorylation occurs in glycolysis?
substrate-level phosphorylation
What is substrate-level phosphorylation?
energy for phosphorylation of ADP is from substrates
What is the process of glycolysis?
- glucose is phosphorylated by the hydrolysis of 2 ATP = hexose diphosphate produced
- hexose diphosphate splits because it is an unstable molecule into 2 triose phosphates
- triose phosphate is oxidised (releases hydrogen) - dehydrogenase enzymes involved
this is an exergonic reaction = releases energy to synthesis ATP - pi from triose phosphate is used to synthesis ATP and pyruvate (3C) is produced
Wha is the NET gain of products from 1 glucose molecule in glycolysis?
2 ATP
2 pyruvate
2 NADH2
What type of reaction happens between the hydrolysis of ATP and the phosphorylation of glucose?
a simultaneous reaction
What are simultaneous reactions?
2 reactions that happen at the same time that rely on each other for the transfer of a product
Where does the link reaction happen?
in the mitochondria matrix
What is the process of the link reaction?
- pyruvate is decarboxylated = releases CO2, decarboxylase enzymes involved
- pyruvate is oxidised by dehydrogenase enzymes - at the same time, NAD is reduced
- acetate is produced
- Co-enzyme A reacts with acetate to form Acetyl Co-enzyme A which is carried to the kreb’s cycle
Wha are the net gains for 1 glucose in the link reaction?
2 acetyle Co-enzyme A
2 CO2
2 NADH
How times does the link reaction happen per 1 molecule of glucose?
x2 = 2 pyruvates are produced from 1 glucose in glycolysis
Where does the Kreb’s cycle happen?
the mitochondrial matrix
Why is glucose phosphorylated?
makes it more reactive and activated
What type of phosphorylation happens in the kerb’s cycle?
substrate-level phosphorylation
What is the process of the Krebs cycle?
- Co-enzyme A brings acetate to the cycle, acetate reacts with a 4C compound
- this 6C compound is oxidised to release H to reduce NAD—> NADH
- the 6C compound is also decarboxylated and releases CO2 producing a 5C compound
- the 5C compound is decarboxylated and releases CO2
- 5C compound is oxidised to release 6H
- 2 NAD are reduced by the 5C compound
- FAD is also reduced
- reduction of FAD releases enough energy for the synthesis of ATP = substrate-level phosphorylation
- the 4C compund is regenerated
What is the net gain from 1 molecule of glucose from the krebs cycle?
4 CO2
6 NADH
2 ATP
2 FADH
How many times does the Krebs cycle happen per 1 glucose molecule?
x2 = 2 acetyl Co-Enzyme A are produced in the link reaction
Is Co-enzyme A an enzyme?
NO
How does pyruvate get into the mitochondrial matrix from the cytoplasm of the cell?
by facilitated diffusion because the mitochondrial membrane has specific carrier proteins for pyruvate
Why does glycolysis need to take place?
glucose cannot cross the mitochondiral membrane - glycolysis takes place to produce pyruvate which can cross the membrane
Why cant glucose cross the mitochondrial membrane?
the membrane has no specific carrier proteins for glucose
Where does oxidative phosphorylation take place?
the mitochondrial cisternae
What is oxidative phosphorylation?
energy for the phosphorylation of ADP comes from an oxidation reaction
Describe the process of oxidative phosphorylation
- NADH2 is oxidised and H2 is removed, NAD does back to the other reactions
- H2 atoms dissociates into 2H+ and 2e-
- relatively high energy e- goes to an e- carrier this gives enough energy for a proton pump to actively pump 2H+ into the inner membrane space
- there is an increase in conc of H+ in the inner membrane space = conc grad for facilitated diff through a stalkd particle containing ATP synthase
- facilitated diff of H+ releases enough electrical potential energy to synthesis ATP
- the remaining e- and H+ associate to form H2 again
- O2 reacts with the H2 as the final electron acceptor to form water - O2 is reduced
What is oxidised in oxidative phosphorylation?
the H carriers = NADH2 and FADH2
What is the stalked particles role in oxidative phosphorylation?
in the cell-surface membrane on the matrix = contains ATP synthase
What is reduced in oxidative phosphorylation?
O2
What do you have at the start of oxidative phosphorylation?
4 ATP
10 NADH2
2 FADH2
How many molecules of ATP is produced from 1 molecule of NADH2 and why?
1 NADH2 activates 3 proton pumps - 6H+ are being pumped = 3 ATP
How many ATP are produced from 1 molecule of FADH2 and why?
1 FADH2 activates 2 proton pumps - 4H+ being pumped = 2 ATP
Why does the oxidation of FADH2 only activate 2 proton pumps?
the e- released from the oxidation of FADH2 and dissociation of H2 do not have as higher energy so they are accepted by a lower energy level e- acceptor further along the membrane
Why might cells not actually produce 38 ATP molecules from the oxidation of 1 glucose molecule?
used as energy to:
- transport pyruvate
-transport H carriers
-active transport to pump protons
In a respirometer why would the coloured liquid move down the scale?
organism is aerobically respiring so they take in O2
Co2 is produced but is absorbed by potassium hydroxide
vol of gases in the tube decreases and pressure also decreases
What is anaerobic respiration?
respiration that occurs when there is no oxygen present
What are obligate anerobes?
orgs that only resp anaerobically as O2 inhibits resp
What are facultative anaerobes?
can anaerobically respire to survive when needed for short periods of time
Why can only glycolysis take place in anaerobic respiration?
no O2 = no final electron carrier = no e- transport chain
so there is no oxidation of H carriers so they cannot be returned to other reactions
How many molecules of ATP are produced per 1 glucose in anerobic resp?
2 ATP per 1 glucose
What is the process of anaerobic resp in animals?
- glucose is phosphorylated by 2ATP –> 2ADP
- hexose diphosphate is made
- hexose diphosphate breaks down into 2x triose phosphates
- 2 NAD are reduced and 4ATP molecules are synthesised
- 2x pyruvate are formed
- 2 NADH are oxidised to 2NAD
- 2x lactate is formed
What is the process of anaerobic resp in plants and fungi?
- glucose is phosphorylated by 2ATP –> 2ADP
- hexose diphosphate is made
- 2 NAD are reduced –> 2NADH and 4 ATP molecules are made from hexose diphosphate being oxidised
- x2 pyruvate are formed
- pyruvate is decarboxylated and 2NADH are oxidised –> 2NAD
- x2 ethanal is produced
- x2 ethanol is produced when aerobically respiring
What are are 2 alternative respiratory substrates?
proteins and lipids
How is the glycerol of lipids used as a respiratory substrate?
- glycerol is hydrolysed
- produces 3C sugar - phosphorylised
- triose phosphate formed
- pyruvate is made to enter the link reaction, krebs cycle and oxidative phosphorylation
How are the fatty acid chains of lipids used as a resp substrate?
- long fatty acid chains are split into 2C fragments
- these produce Acetyl Co-enzyme A
- can enter aerobic resp = Kreb’s –> oxidative phos
How are proteins used as a resp substrate?
- NH3 removed in deamination
- remaining is an organic acid which can enter the Kreb’s cycle
