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Explain why all life needs to perform respiration.

Cells need energy for three main types of activity -
transport, synthesis and movement.

transport of veisicles, DNA replication, protein synthesis and muscle contraction.


Explain why ATP is a better, immediate source of energy for metabolic reactions than glucose.

- The interconversion of ATP and ADP is happening constantly in cells, meaning cells do not need a large source of ATP. ATP is therefore a good immediate energy source.
- Contains bonds between phosphates with intermediate energy: large enough to be useful for cellular reactions but no so large that energy is waster as heat, potentially causing enzymes to denature.
- Energy released in small bursts
- Easily regenerated.


Describe 4 metabolic activities that require ATP.

- Active transport
- Synthesis of biomolecules
- transport
- movement


Draw, label and annotate a diagram of a mitochondrion.

- Outer mitochondrial membrane: separates the contents of the mitochondrian from the rest of the cell. Creates cellular compartment with ideal conditions for aerobic respiration.
- inner mitochondrial membrane: contains electron transport chain and ATP synthase.
- Cristae: projections of the inner membrane which increase the SA available for oxidative phosphorylation.
- Matrix: contains enzymes for the krebs cycle and the link reaction, also contains mitochondrial DNA.
- intermembranal space: proteins are pumped into this space by the electron transport chain. The space is so small the concentration buids up quickly.


State the site of glycolysis within cells.

Cytoplasm of the cell.


Draw a diagram to show the process of glycolysis.

1) Phosphorylation - the first step of glycolysis requires two molecules of ATP. Two phosphates released from two molecules of ATP, are attached to a glucose molecule forming hexose bisphosphate.

2) Lysis - this destablises the molecule causing it to split into two triose phosphate molecules.

3) Phosphorylation - another phosphate group is added to each triose phosphate forming two triose biphosphate molecules. These photophate groups come from free inorganic phosphate ions present in the cytoplasm.

4) Dehydrogenation and formation of ATP - the two triose biphosphate molecules are then oxidised by the removal of hydrogen atoms (dehydrogenation) to form two pyruvate molecules. NAD coenzymes accept the removed hydrogens - they are reduced, forming two reduced NAD molecules.
5) 4 ATPS molecules are also produced using phosphates from triose biphosphate. (substrate level phosphorylation)


State the molecules required for glycolysis, the products from glycolysis, and the fate of the products from glycolysis.

- 2 ATPs
- Glucose
- Phosphate ions
- Coenzyme NAD
- 4 ATPS
- 2 reduced NADs
- 2 molecules of pyruvate
Fate of products:
- ATP is used for energy
- red NAD is used at a later stage to synthesis more ATP
- Pyruvate used in link reaction.


Give an example of substrate level phosphorylation.

The formation of ATP without involvement of an electron transport chain. ATP is formed by the transfer of a phosphate group from a phosphorylated intermediate (in this case triose biphosphate) to ADP.


Define the term “substrate level phosphorylation”

Synthesis of ATP by transfer of phosphate molecule from another molecule.


Define “dehydrogenation”.

The removal of a hydrogen atom.


State the site of the link reaction within cells.

in the matrix of the mitochondria.


Draw a diagram to show the process of the link reaction.

1) Pyruvate enters matrix by active transport.
2) Pyruvate undergoes oxidative decarboxylation - carbon dioxide is removed along with hydrogen.
3) The removed hydrogen atoms are accepted by NAD to form reduced NAD.
4) The resulting two-carbon acetyl group is bound by coenzyme A to form acetyl CoA.
5) Acetyl CoA delivers the acetyl group to the krebs cycle.
6) The reduced NAD is used in oxidative phosphorylation to produce ATP.
7) The CO2 produce will either diffuse away as metabolic waste or be used as a raw material for photosynthesis.


State the molecules required for the link reaction, the products of the link reaction, and the fate of the products from the link reaction.

- Coenzyme A
- pyruvate

- reduced NAD
- acetyl CoA
- CO2

- reduced NAD used in oxidative phosphorylation to produce ATP.
- acetyl CoA passes on acetyl group to kreb cycle
- CO2 produce will either diffuse away as metabolic waste or be used as a raw material for photosynthesis.


Define the term decarboxylation

Removal of a CO2


Define the term oxidative decarboxylation

Removal of carbon dioxide along with hydrogen.


State the site of the Kreb cycle within the cells

Mitochondrial matrix


Draw a diagram to show the process of the kreb cycle.

1) acetyl CoA delivers an acetyl group.
2) the 2 carbon acetyl group combines with the 4C oxaloacetate to make 6C citrate.
3) The 6C citrate molecules undergoes decarboxylation and dehydrogenation, producing 1 red NAD and 1 CO2. The loss of the carbon produces a 5C compound.
4) The 5C compound undergoes further decarboxylation and dehydrogenation reactions eventually regenerating the 4C oxaloacetate, and so the cycle continues.
5) While producing oxaloacetate, ATP is produced by substrate-level phosphorylation. This is the direct transfer of a phosphate group from an intermediate compound to ADP. In this phase, one more CO2, 1 red FAD and 2 red NAD are produced.


State the molecules required.

- Acetyl CoA (the acetyl group)
- Oxaloacetate (regenerated from the cycle)


State the products of the kreb cycle. (From two simultaneous cycles)

- 6 red NAD (coenzyme that delivers electrons to electron transport chain)
- 2 red FAD (coenzyme that delivers electrons to electron transport chain)
- 2 ATP (for energy)
- 4 C02 (by-product)
- 2 Oxaloacetate (combines with acetyl in the kreb cycle)


Draw a table to summarise the products of glycolysis, link and kreb.

Look at notes.


Name three coenzymes involved in respiration and explain the function of each.

FAD and NAD: delivers electrons to electron transport chain.
Acetyl CoA: delivers acetyl group to kreb cycle.


Draw a table to show similarities and differences between NAD and FAD.

NAD - Takes part in all stages of cellular respiration. Accepts 1 hydrogen. Red NAD is oxidised at the start of the electron transport chain, releasing protons and electrons. Results in the synthesis of 3 ATP molecules.
FAD - only accepts hydrogen in the Kreb cycle. Accepts 2 hydrogens. Red FAD is reduced further along the chain. Results in synthesis of only 2 ATP molecules.


Define oxidative phosphorylation.

Oxidative phosphorylation is the process where energy carried by electrons, from coenzymes (NAD and FAD), is used to make ATP.


Define the term electron carrier.

Proteins that accept and release electrons.


Define electron transport chain.

An electron transport chain is made up of a series of electron carriers, each with progressively lower energy levels. As high energy electrons move from one carrier in the chain to another, energy is released.


Define the term chemiosmosis.

The synthesis of ATP driven by the flow of protons across a membrane.


State the site of oxidative phosphorlyation within the cells.

The inner folded membrane (the Cristae) of mitochondria.


Describe the process of oxidative phosphorlyation.

1) Hydrogen atoms are released from coenzymes FAD and NAD and are delivered to the electron transport chain, present in the Cristae of the mitochondria.
2) The hydrogen atoms dissociate into H+ ions and electrons.
3) The high energy electrons are used in the synthesis of ATP by chemiosmosis.
4) Energy is released in redox reactions as the electrons reduce and oxidise electron carriers as they flow along the transport chain.
5) The energy is used to create a proton gradient, leading to the diffusion of protons through ATP synthase, resulting in the synthesis of ATP.
6) At the end of the chain, electrons combine with hydrogen ions and oxygen to form water. Oxygen is called the final electron acceptor and the electron chain cannot operate unless oxygen is present.


Describe the role of the mitochondrial Cristae in oxidative phosphorlyation

The Cristae is the foldings in the inner mitochondrial membrane, which contains the electrons transport chain. The folding increases the SA available for respiration.


State the molecules required for oxidative phosphoprlyation

- Oxygen