Respiration (complete)

Question 1

Define respiration

Answer 1

• A series of reactions in which energy is transferred from organic compounds such as carbohydrates to the temporary energy store, ATP

Question 2

Define Co-enzymes

Answer 2

• complex organic molecules that are used by enzymes to accept or donate molecules involved in a reaction.
• carry chemical groups or ions about.

Question 3

What are the four stages of respiration?
Where do they occur?

Answer 3

• Glycolysis - occurs in the cytoplasm
• Link Reaction - occurs in the mitochondrial matrix
• Krebs Cycle - occurs in the mitochondrial matrix
• Electron transport chain - occurs in the mitochondrial cristae.

Question 4

Describe the process of glycolysis.

Answer 4

• Phosphorylation - glucose is phosphorylated by adding 2 phosphates from 2 ATP molecules, forming glucose phosphate (GP).
• Hydrolysis - GP is hydrolysed using water to form triose phosphate (TP), which donates e- and H+ to form NADH. 2 molecules of TP are formed and 2 molecules of ATP are used up.
• Oxidation - TP is oxidised, forming 2 molecules of pyruvate. Co-enzyme NAD+ collects the H+ ions, forming NADH.

Question 5

What is the overall net gain of products of glycolysis?

Answer 5

• 2 molecules of NADH
• 2 molecules of pyruvate
• 2 molecules of ATP

Question 6

Describe the Link reaction.

Answer 6

• A pyruvate molecules is decarboxylated, forming and releasing CO2. It is then dehydrated, forming NADH and a H+ ion which are released.
• An Acetate molecule is produced, which combines with co-enzyme A to form Acetyl Coenzyme A, which enter the krebs cycle.
• The Link reaction occurs twice for every glucose molecule that undergoes respiration.

Question 7

What is the overall net gain of products for the link reaction?

Answer 7

• 2 molecules of NADH
• 2 molecules of Acetyl Coenzyme A
• 2 molecules of C02

Question 8

Describe the process of the Krebs cycle

Answer 8

• The Acetyl Coenzyme A has 4 carbons combine to it to form a 6 carbon compound.
• NADH is formed and C02 released, forming a 5 carbon compound.
• This occurs again to form a 4 carbon compound.
• ATP is formed and released.
• FADH is formed and released.
• NADH is formed and released again, and the 4 carbon compound can be recycled and go through the krebs cycle again, attaching to the next pyruvate molecule.
• The Krebs cycle occurs twice for every glucose molecule that goes through respiration.

Question 9

What is the overall net gain of products from the Krebs Cycle?

Answer 9

• 1 molecule of ATP
• 2 molecule of CO2
• 3 molecule of NADH
• 1 molecule of FADH

Question 10

Describe the process of the electron transport chain

Answer 10

• Electrons with high energy enter the chain and travel through the electron carriers, donating their energy to pump hydrogen ions across the mitochondrial membrane by active transport.
• Once across the hydrogen ions travel to the ATP synthase molecule in the membrane, and pass through the channel, causing a shape change which catalyses the formation of ATP by oxidative phosphorylation.
• Oxygen as a final electron acceptor binds with spare e- and H+ ions to form water, allowing for the continuous production of ATP as there is a constant downward gradient of H+ ions to travel through the ATP synthase.

Question 11

What is the effect of anaerobic respiration on ATP synthesis.

Answer 11

• At then end of the ETC, Oxygen acts as the final electron acceptor, so if no oxygen available it cannot accept electrons from the last carrier protein, causing a build up of NADH and FADH as they are unable to give away their electrons and protons, therefore no more FAD+ and NAD+ being recycled back to the krebs cycle, which then shuts down, causing ATP synthesis to cease.
• Due to this the NADH produced during glycolysis has nowhere to go, so will donate its hydrogen ions and electrons to pyruvate, forming lactic acid in animals (which can be toxic) or ethanol and CO2 in plants.