Respiration part 2

Krebs, oxi phospho, anaerobic

How many NADH molecules are produced by the Krebs cycle?

3

How many CO2 molecules are produced by the Krebs cycle?

3

How many ATP and FADH2 molecules are produced by Krebs cycle?

1

How many times does the Krebs cycle occur for one molecule of glucose and why?

Twice - 2x pyruvate per glucose

What is the 6-carbon molecule in the Krebs cycle called?

Citrate

What 2 molecules is citrate made up of?

Acetyl and oxaloacetate

What 2 molecules are produced every time a carbon is lost from the carbon chain during the Krebs cycle?

NADH and CO2

Why does oxidative phosphorylation require oxygen?

Oxygen acts as the final electron acceptor

What happens if no oxygen is present during oxidative phosphorylation?

Loss of electron acceptor means lots of free electrons, which cancel out H+ charge so electrochemical gradient is lost

Electrons are very reactive

Where does oxidative phosphorylation occur?

inner mitochondrial membrane

Where does the Krebs cycle occur?

mitochondrial matrix

What is the first stage of the electron transport chain?

NADH transfers 2 high energy electrons to a channel protein in inner mitochondrial membrane, and released 2H+ into matrix

What happens to the electrons in the electron transport chain in terms of energy?

They lose energy as they are transferred from protein to protein

Why is the electron transport chain a redox reaction?

Proteins gain then lose electrons (are reduced then oxidised)

Where is the energy lost by electrons in the electron transport chain used?

To pump H+ from matrix into inter membrane space

What happens to the electrons after the electron transport chain?

They have lost all energy so combine with O2 and 2H+ to form water

Give the equation for the formation of water at the end of the electron transport chain

1/2 O2 + 2H+ + 2e- —> H2O

Why does the concentration of protons (H+) build up in the inter membrane space?

The inner membrane is impermeable to protons so they cannot pass back into matrix

How do protons move back into the matrix from the inter membrane space?

They diffuse down their gradient through an ion channel in an ATP synthase enzyme

How are protons used after they diffuse back into mitochondrial matrix through ATP synthase?

Used by ATP synthase to generate ATP from ADP and Pi

What is chemiosmosis?

The process by which the movement of hydrogen ions across a biological membrane generates ATP

What is the main purpose of oxidative phosphorylation?

To produce ATP

What happens to NADH and FADH2 when there are low oxygen levels?

They cannot be oxidised back to NAD and FAD

Why is the absence of NAD an issue in respiration?

It is needed for the first 3 stages which therefore won't take place, so the cell cannot make ATP

Give the equations for anaerobic respiration in mammals

2NAD

What type of reaction is NADH—> NAD?

Oxidation (loss of electrons)

What type of reaction is pyruvate —> lactate/lactic acid

Reduction (gain of electrons)

Which enzyme catalyses the formation of lactate/lactic acid from pyruvate?

Lactate dehydrogenase

Where and when does anaerobic respiration often occur in mammals?

In muscles during intense exercise

What does lactic acid do to the cell?

Lowers its pH causing proteins to denature

How is lactic acid converted back to glucose?

Blood flowing through the muscles transports the lactic acid to the liver where it is converted back into glucose

Why do we continue to breathe heavily after exercise (oxygen debt)?

Because the conversion of lactic acid to glucose in the liver requires oxygen

Describe what happens during anaerobic respiration in mammals

Cell uses NADH produced by glycolysis to reduce pyruvate to lactate/lactic acid and NADH is oxidised back to NAD to go back through glycolysis to produce 2ATP per glucose

Describe what happens during anaerobic respiration in yeast and some plants

Pyruvate is converted to ethanal, which is reduced to ethanol by NADH (so NADH is oxidised to NAD), NAD can then be used in glycolysis producing 2ATP per glucose

Give the equations for anaerobic respiration in yeast and some plants

2 pyruvate —> 2x ethanal (+ 2CO2) —> 2x ethanol

2NAD—>2NADH

Which enzyme catalyses the formation of ethanal from pyruvate

Pyruvate decarboxylase

Which enzyme catalyses the formation of ethanol from ethanal?

Alcohol dehydrogenase