Respiration

Question 1

Che cosa è respirazione?

Answer 1

La respirazione cellulare è un processo di combustione nel quale i nutrienti, ridotti dalla digestione a componenti elementari come zuccheri semplici, amminoacidi e acidi grassi, vengono demoliti in molecole ancora più semplici ottenendo energia disponibile alla cellula sotto forma di ATP.

Question 2

What is the first step in respiration?

Answer 2

Glycolysis

Question 3

What happens first in glycolysis?

Answer 3

We have a glucose molecule (6 carbons). It attaches one phosphorus particle to itself to become glucose-6-phosphate. Phosphate particle comes from the step when ATP is changed to ADP (high energy to low).

Question 4

After rearrangement of glucose-6-phosphate, what is the name of the molecule?

Answer 4

Fructose-6-phosphate

Question 5

How fructose-6-phosphate is changed to fructose-1,6-bisphosphate?

Answer 5

It adds another phosphate particle which again comes from the change is ATP to ADP.

Question 6

What happens with fructose-1,6-bisphosphate?

Answer 6

It splits into 2 parts: 1) dihydrooxacetone 2) glyceraldehyde-3-phosphate.

But then, dihydrooxacetone rearranges itself into glyceraldehyde-3-phosphate.

And so we are left with 2 molecules of glyceraldehyde-3-phosphate.

Question 7

What happens with 2 molecules of glyceraldehyde-3-phosphate?

Answer 7

2NAD+ are changed to 2NADH as it would give energy for 2 phosphate particles to join with 2 glyceraldehyde-3-phosphate.

Now, we have 2 molecules of 1,3-bisphospho-glycerate.

Question 8

What happens to 1,3-bisphospho-glycerate?

Answer 8

2ADP are changed to 2ATP by taking away 2 phosphates from 1,3-bisphospho-glycerate.

Now, we have 2 molecules of phospho-glycerate.

But then, again, it rearranges itself to 2 molecules of phospho-enolpyruvate.

Question 9

Describe last step of glycolysis.

Answer 9

2ADP are changed to 2ATP by taking away 2 phosphates from phospho-enolpyruvate. Now, we are left with 2 pyruvate molecules.

Question 10

What are the products of glycolysis?

Answer 10

2ATP (total number of ATPs is 4 but 2 of them are used up), 2NADH, 2 pyruvates

Question 11

What happens during link reaction or pyruvate decarboxylation?

Answer 11

1) CO2 is removed from pyruvate while NAD+ is converted into NADH. This is OXIDATION REACTION.
2) Acetyl group is added to coenzyme A resulting in acetyl CoA.

Question 12

What is the first step of Kreb’s cycle or Citric acid Cycle?

Answer 12

Condensation reaction of acetyl CoA and oxaloacetone resulting in formation of citric acid.

Question 13

What are the next steps of Kreb’s cycle?

Answer 13

Oxidation of NAD+ to NAD and decarboxylation forming alpha-ketoglutarate.

Question 14

To what alpha-ketoglutarate is changed?

Answer 14

To Fumarate by oxidation of NAD+ to a reduced NAD and decarboxylation.

Question 15

What happens during REGENERATION step?

Answer 15

1) ADP is changed to ATP
2) FAD is changed to FADH2 forming Malate
3) NAD+ is changed to NAD forming Oxaloacetate

Question 16

What are the products of Kreb’s cycle?

Answer 16

1 ATP, 2CO2, 3NADH, 1FADH2

BUT!!!

Kreb’s cycle happens twice as there are 2 acetyl CoA molecules. Therefore products are doubled resulting in: 2ATP, 4CO2, 6NADH, 2FADH2

BUT!!!

If we also consider products from previous reaction (link reaction) we should also add 2NADH and 2CO2.

Question 17

Where does glycolysis happen?

Answer 17

In the cytoplasm

Question 18

Where does the link reaction take place?

Answer 18

In the mitochondrial matrix

Question 19

Where does the Kreb’s cycle happen?

Answer 19

In the mitochondrial matrix

Question 20

Where does electron transport chain happen?

Answer 20

In the matrix, inner mitochondrial membrane, and inter membrane space.

Question 21

What happens during electron transport chain?

Answer 21

1) NADH + H+ gives pairs of hydrogen atoms to the first carrier in the chain, and NAD+ remains in the matrix.
2) Hydrogen atoms are split and this release 2 electrons which are carried by carriers in the chain.
3) Electrons release energy which helps H+ to be pumped across inner mitochondrial membrane.
4) Electrons are transferred to a terminal electron acceptor at the end of the chain. Here, they bind to oxygen which then bonds to 2 H+. Water is formed in this way.
5) H+ pass back to the matrix through ATP synthase. During their movement energy is released and so ADP is phosphorylated to form ATP.

Question 22

What does amphibolic mean?

Answer 22

In the certain process we have both anabolic and catabolic reactions (ex: Kreb’s cycle)