Chapter 12 - Respiration Flashcards
What is aerobic respiration?
Respiration in plentiful supplies of oxygen
What is anaerobic respiration?
Respiration where oxygen supplies are limited
Products of aerobic respiration
Carbon dioxide, water and ATP
Products of anaerobic respiration
Lactate and a little ATP
What are the four stages of respiration?
Glycolysis
The Link reaction
The Krebs cycle
Oxidative phosphorylation
General description of glycolysis
6C glucose splits into 2x 3C pyruvate
General description of the Link reaction
2C Acetylcoenzyme A is formed from the 3C pyruvate
General description of the Krebs cycle
ATP, FAD and NAD are produced through the oxidation and reduction of acetylcoenzyme A
General description of oxidative phosphorylation
The use of electrons to synthesise ATP and water
Where does glycolysis occur?
Cytoplasm
What happens during glycolysis?
Two ATP molecules are hydrolysed into ADP and P
These phosphate molecules phosphorylate the glucose, making it more reactive
The glucose molecule is split into two molecules of triose phosphate
Triose phosphate is oxidised and this hydrogen reduces a hydrogen carrier called NAD
The triose phosphate molecules are converted into 2 molecules of 3C pyruvate
This process also regenerates 2 molecules of ATP
What happens to the pyruvate during anaerobic respiration?
It is converted into ethanol in plants and yeast or lactate in animals using reduced NAD
What are the overall products from glycolysis?
2 molecules of ATP
2 molecules of reduced NAD
2 molecules of pyruvate
Does glycolysis require oxygen?
No
What happens during the link reaction?
The pyruvate is oxidised to form acetate
It loses one carbon dioxide molecule and two hydrogen atoms
These hydrogen atoms are accepted by the NAD, reducing it
The 2C acetate combines with coenzyme A to form acetylcoenzyme A
Overall equation for the link reaction
Pyruvate + NAD + CoA -> CO2 + reduced NAD + acetyl CoA
How many times will the link reaction occur per glucose molecule?
Twice
What are enzymes?
Molecules that other enzymes require in order to function
What are the three coenzymes in photosynthesis and respiration?
NAD, FAD, NADP
What are the three main functions of the Krebs cycle?
Breaks down macromolecules (pyruvate) into smaller ones (CO2)
The hydrogen atoms are carried to the electron transfer chain and provide energy to make ATP
Regenerates the 4C compound that combines with acetylcoenzyme A
How many pyruvate molecules are formed per molecule of glucose?
2
What is produced during the Krebs cycle and the link reaction?
Reduced coenzymes
One molecule of ATP
Three molecules of CO2
The yield for a single glucose molecule is double this
What happens during the Krebs cycle?
Acetyl CoA combines with a 4C compound to produce a 6C compound
This 6C compound releases one CO2 molecule and hydrogen atoms to form a 5C compound
These hydrogen atoms are used to form reduced NAD
The 5C compound has another molecule of CO2 removed to form a 4C compound
This time, one molecule of reduced FAD, one molecule of ATP, and two molecules of reduced NAD are produced
The 4C compound combines with the CoA to repeat the cycle again
How are hydrogen atoms transported to the site of oxidative phosphorylation?
By the coenzymes FAD and NAD
What is the site of oxidative phosphorylation?
The cristae of the mitochondria
What is oxidative phosphorylation?
The process by which the energy contained in the H+ ions carried by FAD and NAD is used to make ATP
How does oxidative phosphorylation work?
Reduced NAD and FAD are oxidised, losing a hydrogen atom in the process. This atom splits into protons and electrons
The electron from these molecules is donated to the first carrier in the electron transfer chain
In a series of redox reactions, this electron is passed through the carrier molecules, each at a lower energy level to the last.
The energy released by this process is used to actively transport protons into the inter-membranal space
The protons accumulate here and diffuse back into the matrix of the mitochondria through ATP synthase molecules embedded in the wall
At the end of the transport chain, protons, electrons and O2 combine to form water. Oxygen is the final acceptor of these electrons
What is the important function of oxygen?
It acts as the final acceptor of the electrons and so keeps the process moving
Why is energy released from ATP gradually?
The electron moves along the transfer chain and gradually loses energy at each level, rather than in one go
How many ATP molecules can be made from one glucose molecule?
32
How are proteins used for respiration?
First, they are hydrolysed into amino acids
Then they are deaminised to remove the amino group
They enter the respiratory pathway at different points depending on the number of carbon atoms they contain - 3C compounds are converted to pyruvate and 4 or 5 C compounds are converted to intermediates in the Krebs cycle
how are lipids used for respiration?
Hydrolysed into glycerol and fatty acids
Glycerol phosphorylated and converted to TP which enters glycolysis
Fatty acids converted to 2C acetyl coenzyme A, which is used in the Krebs cycle
Why do lipids release much more energy than carbohydrates?
Oxidising lipids produces many hydrogen atoms which are used in oxidative phosphorylation to produce ATP
What two processes can’t take place without oxygen?
The Krebs cycle and the electron transfer chain
Why can the Krebs cycle and the electron transfer chain not take place without oxygen?
There is no FAD and NAD - it will all be reduced. This means that the H+ produced during the Krebs cycle won’t be taken up by the molecules so the enzymes stop working
What is the only process that doesn’t require oxygen?
Glycolysis
What must occur for glycolysis to continue happening?
Pyruvate and hydrogen must be removed constantly
How is NAD regenerated?
The H+ is removed from reduced NAD and donated to pyruvate
Why is it important that NAD is regenerated?
There is only a tiny supply of NAD in cells as it is and without regenerating NAD, the hydrogen produced during glycolysis won’t be absorbed, so glycolysis stops
What is pyruvate converted to during anaerobic respiration in microorganisms?
Ethanol and CO2
What is pyruvate converted to during anaerobic respiration in animals?
Lactate
How is ethanol produced?
During anaerobic respiration in yeast, the pyruvate loses a CO2 molecule and gains a hydrogen atom
What is the equation for the production of ethanol?
Pyruvate + reduced NAD -> ethanol + oxidised NAD + CO2
What happens during strenuous exercise?
Oxygen is used up more rapidly than it is supplied leading to an oxygen debt
How is lactate produced during anaerobic respiration?
NAD from glycolysis accumulates when oxygen is in short supply. To overcome this, pyruvate takes two hydrogen atoms from the reduced NAD to form lactate and oxidised NAD
What is the equation for the production of lactate?
Pyruvate + reduced NAD -> lactate + oxidised NAD
What will happen after the oxygen debt is repaid?
Lactate is oxidised to re-form pyruvate
Why is lactate bad?
It is acidic so affects enzymes
Causes cramp and muscle fatigue
Where is lactate removed from the body?
The liver
How is ATP produced during anaerobic respiration?
Glycolysis - pyruvate is used up so neither the Krebs cycle nor the electron transfer chain can use it
