Respiration 3.5.2 (Energy transfers in and between organisms 3.5) Flashcards
What are the 4 key stages of aerobic respiration ?
Glycolysis ~> Link reaction ~> Krebs cycle ~> Oxidative phosphorylation
What is glycolysis ?
It’s the first stage of aerobic and anaerobic respiration
Where does glycolysis take place ?
In the cytoplasm and is an anaerobic process
What happens to NAD in glycolysis
It’s reduced so therefore gains a H+ .
Becomes NADH
EQ : Describe the process of glycolysis (4)
1) Phosphorylation of glucose using ATP.
2) Oxidation of triose phosphate to pyruvate
3) Net gain of ATP
4) NAD reduced
What are the products of glycolysis ?
2 x pyruvate
Net gain of 2 ATP
2 x NADH
what are co-enzymes?
Molecules that airs in the function of an enzyme by transferring a chemical group from one molecule to another
where does link reaction take place
mitochondrial matrix
where does the krebs cycle take place
mitochondrial matrix
where does oxidative phosphorylation take place
cristae ( mitochondrial inner membrane)
what are the products made per krebs cycle ?
• 3x NADH
• 1x FADH
• 1x ATP
• 2x Co2
what are the products per glucose molecule in the krebs cycle ?
• 6x NADH
• 2x FADH
• 2x ATP
• 4x Co2
what are the products for every glucose molecule in the link reaction
• 2x Acetylcoenzyme A
• 2x Co2 released
• 2x NADH
what are the stages of the link reaction
• pyruvate made in glycolysis gets oxidised to acetate
• NAD is reduced to NADH
• Acetate then combined with Co enzyme A to produce acetylcoenzyme A
How does pyruvate transport from the cytoplasm to the matrix ?
By active transport
How many NADH are made in total after glycolysis , link reaction and krebs cycle from one glucose molecule
10
How many FADH2 are made in total after glycolysis , link reaction and the krebs cycle from 1 glucose molecule
2
what was the main point of the krebs cycle
To make electrons available for oxidative phosphorylation
Where do the electrons and protons come from in phosphorylation
From the H+ in NADH and FADH2
what do electrons do in oxidative phosphorylation
They provide energy to make ATP
What is anaerobic respiration
In the absence of oxygen respiration occurs anaerobically
Where does anaerobic take place
Cytoplasm
What is the only process that occurs in anaerobic respiration
Glycolysis
What are the products of glycolysis in anaerobic respiration in animals
lactate
What are the products of glycolysis in anaerobic respiration in plants
Ethanol and carbon dioxide
What happens after pyruvate is produced in glycolysis in anaerobic respiration of animals
- Pyruvate produced in glycolysis is reduced to form lactate in animals by gaining the hydrogen from NADH.
- This oxides NAD so that it can be reused in glycolysis and ensure more ATP is continued to be produced
Why do plants produce different products to animals in anaerobic respiration
Because of the different enzymes involved
What happens after pyruvate is produced in glycolysis in anaerobic respiration of plants and microbes
- Pyruvate produced in glycolysis is reduced to form ethanol and carbon dioxide in plants by gaining the hydrogen from NADH.
- This oxides NAD so that it can be reused in glycolysis and ensure more ATP is continued to be produced
What percentage is aerobic respiration efficient and why
32% efficient
• Some protons leaking across mitochondrial membrane during oxidative phosphorylation
• ATP being used to actively transport pyruvate and NADH into matrix because some energy is lost as heat .
Why is anaerobic respiration less efficient than aerobic respiration
Only 2 ATP molecules are produced from one glucose molecule
EQ : Without oxygen , less ATP is produced by respiration. Explain why. (2)
Only glycolysis is able to take place
Only produces 2 ATP molecules
EQ : Explain why converting pyruvate to ethanol is important in allowing the continued production of ATP in anaerobic respiration (2)
so NAD can be reused
So glycolysis can proceed
EQ : Give two ways in which anaerobic respiration of glucose in yeast is similar to anaerobic respiration of glucose in a muscle cell (2)
1) produces NAD
2) ATP formed
EQ : Give two ways in which anaerobic respiration of glucose in yeast is different from anaerobic respiration of glucose in a muscle cell (2)
1) Ethanol is formed in yeast whereas in a muscle cell , lactic acid is formed
2) Carbon dioxide is produced in yeast , whereas in a muscle cell , it doesn’t produce Carbon dioxide
Why is respiration important
Respiration produces ATP
For active transport , protein synthesis etc
summarise the stages of anaerobic respiration
Glycolysis
NAD regeneration
Explain what happens after glycolysis if respiration is anaerobic
1) Pyruvate converted to lactate (animals) or ethanol (plants and yeast)
2) oxidising reduced NAD - NAD regenerated
3) So glycolysis can continue allowing continued production of ATP
Suggest why anaerobic respiration produced less ATP per molecule of glucose than aerobic respiration
- Only glycolysis involved which produced little ATP (2 c molecules )
- No oxidative phosphorylation which forms majority of the ATP ( around 34 molecules )
Describe the krebs cycle
1) acetyl coenzyme A reacts with a 4C molecule
• releasing coenzyme A
• producing a 6C molecule that enters the krebs cycle
2) In a series of oxidation - reduction reactions , the 4C molecule is regenerated and :
• 2 x CO2 lost
• Coenzymes NAD and FAD reduced
• Substrate level phosphorylation
• ATP produced
Describe the process of oxidative phosphorylation
1) NADH / FADH oxidised to release H atoms => split into protons and electrons
2) Electrons transferred down electron transfer chain by redox reactions
3) Energy released by electrons used in the production of ATP from ADP + Pi ( chemiosmotic theory )
• Energy used by electron carried to actively pump protons from matrix to intermembrane space
• Protons diffuse into matrix down an electrochemical gradient via ATP synthase
• Releasing energy to synthase ATP from ADP + Pi
4) In matrix at the end of electron transport chain , oxygen is final electron acceptor
• So protons , electrons and oxygen combine to form water
Give examples of other respiratory substrates
Breakdown products of lipids and amino acids , which enter the Krebs cycle . For example :
• Fatty acids from hydrolysis of lipids => converted to Acetyl Coenzyme A
• Amino acids from hydrolysis of proteins => converted to intermediates in Krebs cycle
EQ: Pea plants respire aerobically , producing ATP which can be used for amino acid synthesis . Describe the role of oxygen in aerobic respiration (2)
• Terminal electron acceptor
• forms water
EQ: The bacteria respire anaerobically . This produces hydrogen and ATP used in nitrogen fixation. The hydrogen comes from reduced NAD . Explain how the regeneration of NAD in this way allows ATP production to continue (2)
• oxidised NAD can accept more electrons
• This continues process of glycolysis
EQ : Oxygen is needed for the production of ATP on the cristae of the mitochondrion . Explain why (3)
- forms h2O
- Electrons cannot be passed along electron transfer chain if no oxygen accepts them
- ATP formed as electrons pass along transport chain
