Biology repsiration

Catabolic

a type of metabolic reaction that breaks down complex molecules into simpler ones and releasing energy

Respiratory substrate

an organic molecule that can be broken down in respiration to release energy for ATP synthesis (glucose)

oxidised

when a substance loses electrons, hydrogen, or gains oxygen during a chemical reaction

Respiration

a catabolic metabolic process in which respiratory substrates are oxidised to release energy which is used to synthesise ATP 

Aerobic respiration

The complete breakdown of glucose in the presence of oxygen, releasing energy which is used to produce carbon dioxide, water, ATP. involving glycolysis, link reaction, Krebs cycle, oxidative phosphorylation

Dehydrogenation

The removal of hydrogen atoms (and their electrons) from a molecule which are transferred to coenzymes (NAD/FAD). Catalysed by dehydrogenase enzymes

Decarboxylation

The removal of a carboxyl group (COOH) from a molecule releasing it as carbon dioxide. Catalysed by decarboxylase enzymes

Oxidative phosphorylation

the production of ATP using energy released from the transport of electrons along the electron transport chain, with oxygen as the final electron acceptor.

Coenzyme

a non-protein molecule that works with an enzyme by accepting or donating chemical groups or electrons during a reaction

Substrate-level phosphorylation

The direct synthesis of ATP from ADP and inorganic phosphate using energy released from a chemical reaction involving a substrate (glycolysis or krebs)

stages of aerobic respiration in order

glycolysis, link reaction, krebs cycle, ETC

where does glycolysis take place in the cell?

cytosol/cytoplasm

where does the link reaction take place in the cell?

mitochondrial matrix

where does the Krebs cycle take place in the cell?

mitochondrial matrix

where does the ETC take place in the cell? 

on the inner mitochondrial membrane 

state the coenzymes that are important in aerobic respiration

NAD , FAD, CoA

describe the role of NAD in aerobic respiration

Accepts hydrogen atoms from substrates during glycolysis, link reaction and krebs cycle to form reduced NAD (NADH). Reduced NAD donates electrons to ETC to help generate ATP

describe the role of FAD in aerobic respiration

accepts hydrogen atoms during krebs cycle to form reduced FAD, reduced FAD donates electrons to the ETC later than reduced NAD and so produces slightly less ATP

Explain why reduced FAD produces slightly less ATP than reduced NAD during aerobic respiration

Reduced FAD enters the electron transport chain later than reduced NAD, 

what is phosphorylation?

the addition of a phosphate group to a molecule

what is ATP hydrolysis?

the breaking of the bond between the 2nd and 3rd phosphate group of ATP, converting ATP back into ADP and inorganic phosphate with the addition of one molecule of water, releasing energy

state what happens in stage 1 of glycolysis

glucose is phosphorylated

explain what happens in stage 1 of glycolysis

glucose is phosphorylated using the phosphate groups from 2 hydrolysed ATP molecules, forming Hexose bisphosphate

state what occurs in stage 2 of glycolysis

the splitting of hexose bisphosphate in 2 triose phosphate molecules

explain what happens in stage 2 of glycolysis 

Hexose bisphosphate is split due to it having 2 phosphate groups attached, making it unstable and more reactive and therefore easier to split. 

how many carbons does a triose phosphate molecule have?

3

state what happens in stage 3 of glycolysis

the oxidation of triose phosphate into pyruvate

explain what happens in stage 3 of glycolysis

As a result of splitting hexose bisphosphate, 2 triose phosphate molecules are produced which have 3 carbons each. Each triose phosphate molecule is oxidised and its hydrogens are accepted by NAD to form NADH. catalysed by dehydrogenase enzymes

Explain why the type of phosphorylation happening in glycolysis is substrate-level 

oxidation of triose phosphate in stage 3 releases enough energy to allow for the direct synthesis of ATP from ADP and Pi 

how many molecules of ATP does one triose phopshate molecule produce in glycolysis?

2

What is the net total of ATP molecules formed in stage 3 of glycolysis during the oxidation of triose phosphate?

4

What is the total amount of ATP molecules produced in glycolysis?

4 by substrate-level phosphorylation

What is the net gain of ATP molecules from glycolysis and why?

net gain is 2 ATP molecules due to 2 molecules of ATP being used for the initial phosphorylation of glucose. 

what happens when the 2 triose phosphate molecules are oxidised in stage 3 of glycolysis?

they are converted into 2 pyruvate molecules by a series of enzyme-controlled reactions

what are the products of glycolysis per glucose molecule?

2 molecules of ATP, 2 molecules of NADH, 2 molecules of pyruvate 

what happens to pyruvate when oxygen is present?

Pyruvate will enter the link reaction and will be converted into Acetyl coA

What happens to pyruvate when oxygen is absent?

Pyruvate stays in the cytoplasm

What conditions need to be present in order for pyruvate to enter the link reaction?

Presence of oxygen in the mitochondria 

Whats the importance of the link reaction?

It links glycolysis to the krebs cycle by converting pyruvate into acetyl coA which can then enter the krebs cycle as pyruvate cannot enter the krebs cycle directly

Whats the first step in the link reaction?

oxidative Decarboxylation of pyruvate

explain what happens during the decarboxylation of pyruvate

each pyruvate loses a carbon as carbon dioxide which results in the formation of a 2 carbon molecule called acetate

whats the second step of the link reaction?

Dehydrogenation of pyruvate 

Explain what happens during the dehydrogenation of pyruvate

hydrogen atoms are removed and accepted by NAD to form NADH

whats the 3rd step in the link reaction?

Formation of Acetyl-CoA

Explain how Acetyl-CoA is formed in the link reaction?

Each pyruvate molecule is decarboxylated to form a 2-carbon acetate. The acetate then undergoes dehydrogenation, reducing NAD to NADH, and combines with coenzyme A to form acetyl-CoA. For one glucose, this happens twice, producing 2 acetyl-CoA, 2 NADH, and 2 CO₂

what re the products per molecule of glucose in the link reaction?

2 carbon dioxide, 2 NADH, 2 Acetyl-CoA

what are the products of the krebs cycle per molecule of glucose?

4 carbon dioxide, 6 NADH, 2 reduced FAD, 2 ATP

how many times does the krebs cycle turn per molecule of glucose and why?

twice because each glucose molecules produces 2 acetyl-CoA via the link reaction and the purpose of the krebs cycle is to oxidise acetyl-CoA completely to carbon dioxide and to produce reduced coenzymes and ATP

What happens in the first stage of the krebs cycle?

Acetate from acetyl-coA combines with a 4c compound to form a 6c compound, coenzyme A is released (regenerated) and can be reused in the link reaction

what happens in the second stage of the krebs cycle?

The 6c compound is gradually converted back into a 4c compound through several enzyme-catalysed steps, the 6c compound undergoes 2 decarboxylation reactions losing 2 carbon atoms as carbon dioxide which regenerates the 4c compound

how many dehydrogenation reactions happen in the krebs cycle per acetyl-coA and how many pairs of hydrogen atoms are accepted by NAD and FAD

4 pairs of hydrogen atoms are dehydrogenated, NAD accepts 3 pairs and FAD accepts 1 pair

If there are 2  acetyl-coA per glucose molecule how many dehydrogentaion reactions happen in total in the krebs cycle and why?

8 because each acetyl-coA undergoes 4 dehydrogenation reactions 

What do reduced NAD and FAD do with their accepted hydrogen atoms once they’ve left the krebs cycle?

the hydrogen atoms are donated to the ETC

When can the krebs cycle only take place?

under aerobic conditions because oxygen is needed to reoxidise reduced NAD and FAD in the ETC allowing the cycle to continue