Respiration (WIP)

eduqas alevel biology

ATP structure

Formation of ATP

phosphorylation. ADP becomes ATP by the addition of a phosphate molecule. Endergonic as 30.6KJ/mol is taken in

Hydrolysis

ATP to ADP + Pi. Exergonic as it releases 30.6KJ/mol

ATPase

catalyses the hydrolysis of ATP. This is an advantage as it is the ONLY enzyme needed for the reaction

Why is ATP better than glucose

glucose has many high energy bonds so the uncontrolled release of energy from it would result in an increase in temperature that would destroy cells. Instead living organisms use the gradual release of energy in small steps to produce ATP. ATP can transfer free energy from energy rich compounds as and when it is needed

universal energy currency

ATP acts as an energy carrier in all living cells for nearly all chemical reactions

what type of process is respiration?

catabolic process from a series of enzymes

movement of electrons and H

passed from chemical to an electron or hydrogen carrier

dehydrogenase enzymes remove H from a substance

NAD+

one of the most important electron carriers- nicotinamide adenine dinucleotide

Glycolysis process

• “sugar splitting:

• occurs in cytosol in cells

• no oxygen required- anaerobic

• net ATP production of 2ATP

glycolysis step1

The glucose is phosphorylated to make it more reactive

Glycolysis step 2

hexose phospahte is unstable so it splits

glycolysis step 3

triose phosphate is converted into pyruvate as it loses 2 hydrogens to NAD. Energy released is used to produce 4 ATP (2 are used in the first step to 2 ATPs are produced overall)

why is oxygen is present in glycolysis

the NADH/H+ and pyruvate will diffuse into the mitochondria

link reaction

takes place in the matric of the mitochondria which contains the enzymes needed- happens twice as there are 2 pyruvates from glycolysis)

link reaction step 1

(decarboxylase) converted into acetate with the formation of NADH/H and the loss of CO2 (decarboxylation)

link reaction step 2

acetate combines with coenzyme A

krebs cycle information

release energy from carbon bonds via reduced intermediates

reduced NAD and FAD deliver hydrogen to the electron transport system

Krebs cycle 1

The acetylke CoA combines with a 4C acid to make a 6C acid

Krebs cycle 2

citrate undergoes a series of reactions where CO2 and Water are released. The 4C acids are regenerated via citrate and 5C intermediate

Electron transport chain 1 (happening in mitrocondria inner membrane)

a molecule in a reduced form is oxidised

Electron transport chain 2

the hydrogen atom (proton) passes through a proton pump. As it is passed through, an electron is removed and the remaining proton is pumped to the other side

Electron transport chain 3

the electrons are passed from one electron carrier protein to another. The energy lost/ released when this happens is used by the proton pumps to pump more protons across the membrane

Electron transport chain 4

a higher concentration of protons build up on one side of the membrane. They cannot get back across as the membrane is impermeable to H+. The concentration difference makes a difference in pH and charge. Stalked particles contain ATP synthetase

Electron transport chain 5

the protons can pass down a concentration gradient though a channel in the enzyme

Electron transport chain 6

the H+ have high energy. This is used by ATP synthetase to combine ADP with inorganic phosphate to form ADP

Electron transport chain 7

some H+ are pumped back across the membrane to maintain the concentration gradient

Electron transport chain 8

the e- passed through the electron carrier proteins are picked up by a final electron acceptior. it also picks up some H= and is reduced

how much atp is produced when NAD is oxidised when it is the initial electron acceptor?

3 ATP

how much atp is produced when FAD is oxidised when it is the initial hydrogen carrier?

2

what is oxidative phosphorylation

the addition of phosphate to ADP using energy obtained from the oxidation of glucose and intermediate molecules

oxidative phosphorylation= ETC

the movement of H+ and e- is used to generate ATP but this will only occur with oxygen acting as the final electron acceptor

substrate level phosphorylation

the molecules of ATP generated during Glycolysis are formed directly from phosphate compounds and ADP

Animal tissue -anaerobic respiration

glucose——> lactic acid

anaerobic respiration- fungi/plants

glucose———> ethanol + carbon dioxide

why is glycolysis the only stage that can happen aerobically

it is substrate level phosphorylation. Reduced NAD cannot be reoxidised and made available to pick up more oxygen

Fermentation

Pyruvate gets decarboxylated into ethanal. The reduced NAD passes the hydrogen to ethanal whcih is reduced to ethanol

lactic acid formation

efficiency of only 2%

oxygen debt

-build up of lactic acid in muscle causing cramps

-when oxygen is available again lactic acid is broken down in the liver

-most of it is converted into glycogen to be stored

what is the role of oxygen in the electron transport chain?

It is the final electron acceptor and maintains the flow of electrons

why is it important to convert pyruvate into lactate?

oxidises the reduced NAD meaning it gets replaced and glycolysis can continue and produce ATP

Alternative respiratory substrates: lipids

provide energy store and can be used when carbohydrate levels are low. Fat is split into glycerol and fatty avuds before being used in the Krebs cycle and ETC

Alternative respiratory substrates: proteins

only when an individual is starving. Tissue protein is mobilised to supply energy. If energy supplies in died aren’t enough protein in food is diverted to respiration. Protein is split into keto acids and ammonia whcih is fed into respiration. Ammonia> urea> kidney

gAlternative respiratory substrates: glycogen and starch

hydrolysed to release glucose. Sucrose can be broken down into glucose and fructose, Fructose can be convereted into hexose biphosphate and enter glycolysis

acetyl coenzyme A- importance

most metabolic pathways lead here. Formed during oxidation of carbohydrates, fats, proteins. Represent a common pathway by which the products are fed into the krebs cycle