Higher Biology - Unit 2.2

​Unit 2.2

Cellular respiration​

​A T P

​Adenine Triphosphate

​ATP is an energy carrying molecule used in cells. It can release energy very quickly.

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​Energy is released from ATP when the end phosphate is removed. Once it has released energy it becomes ADP (adenine diphosphate) which is a low energy molecule.

​Tip: The phosphate has Died, so it becomes (Adenine)Diphosphate

​A T P & A D P

​ADP can be transferred back into ATP, however energy will be required.

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​These molecules can be recycled so that a constant stream of energy rich ATP is available for all metabolic pathways in the cell.

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​ATP can transfer energy to other molecules in processes such as muscle contraction, DNA replication, Active transport, and Synthetic pathways

Multiple Choice

When ATP becomes ADP...

• Energy is released

• Energy is required

Multiple Choice

What happens when ATP releases energy?

• It gains a phosphate molecule

• It looses a phosphate molecule

• It becomes ACP

Multiple Choice

When ADP becomes ATP...

• Energy is required

• Energy is released

​Respiration

​ Respiration (a metabolic pathway) can be split up into 3 stages:

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-Glycolysis

-Citric acid cycle

-Election transport chain ​

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​Respiration

​Glycolysis occurs in the cell's cytoplasm

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Citric acid​ cycle occurs in the matrix of the mitochondria

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Electron transport chain ​occurs in the inner membrane of the mitochondria

​Glycolysis

​Glycolysis is the breakdown of glucose into 2 pyruvate molecules.

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​During this process, several intermediate molecules are produced and ATP molecules in an energy investment stage are required

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​Glycolysis

​After the energy investment stage, more ATP is then regenerated than what was used in the production of the intermediates.

Therefor their is a net gain ​of ATP molecules.

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​Dehydrogenase enzymes hydrogen ions and electrons from intermediates of the cycle, which are then past on to the co-enzyme NAD. This forms NADH.

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The hydrogen ions and electrons are then passed on to the electron transport chain on the inner mitochondrial membrane.​

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​Fermentation - Citric cycle

​If oxygen is available: The pyruvate molecules will progress to the citric acid cycle stage.

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​If oxygen is not available: The pyruvate molecules will undergo fermentation in the cytoplasm of the cell.

​Fermentation

​There are 2 types of Fermentation:

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​​Alcoholic Fermentation - The pyruvate is converted into ethanol and CO2. This occurs in plant cells and fungi

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Lactace Fermentation - The pyruvate is converted into lactate. This occurs in animal cells

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Fermentation produces a lot less ATP than aerobic respiration​

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​Cirtic Acid Cycle

​The pyruvate enters the matrix of the mitochondria and the carbon dioxide is removed.

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​Carbon is removed to form an acetyl group, which is combined with an enzyme to form acetyl coenzyme A.

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​The acetyl from the coenzyme A combines with a molecule called Oxaloacetate to form Citrate (hence the name of this stage).

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​Citric Acid Cycle

​Intermediate molecules are formed from this process because the enzymes remove carbon and hydrogen/electrons. Carbon dioxide is released as a by-product, and ATP is produced.

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​These intermediate steps gradually convert Citrate back into Oxaloacitate, which is then able to combine into another acytel group.

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​Electron Transport Chain

​The last stage of respiration, produces the most ATP, occurs in the inner membrane of the mitochondria where a collection of proteins are found.

​NADH will release the hydrogen ions and electrons into the transport chain. The electrons transfer their energy to the proteins in the membrane.

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This provides energy for the hydrogen ions to be pumped across the inner mitochondrial membrane. The flow of ions across the membrane synthesises a protein calls ATP synthase

El​ectron Transport Chain

​The oxygen then combines with the hydrogen Ions and electrons to form water.

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​38 ATP molecules are produced in total from this process.

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​Glucose and Respiration

​If glucose isn't available in the respiration pathway, other respiratory substrates can be used via alternative metabolic pathways.

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​Starch , glycogen , proteins (amino acids) , and fats can all be broken down into intermediate molecules during glycolysis or the citric acid cycle.

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​This provides alternative metabolic pathways to make ATP!

Multiple Choice

During glycolysis, what is the glucose broken down into?

• Glycogen

• Ethanol

• CO2

• 2 Pyruvate molecules

• 5 Pyruvate molecules

Multiple Choice

After glycolysis, there is a ... of ATP

• net gain

• loss

• breaking down

• production

Multiple Choice

Fermentation will take place instead of respiration if the conditions are...

• Aerobic

• Anaerobic

Multiple Choice

Citric acid cycle: Which molecule does the acetyl from the coenzyme A combine with to form citrate?

• Pyruvate

• Hydrogen

• Phospholipids

• Oxaloacitate

Multiple Choice

Which respiration stage produces the most ATP? (38 ATP)

• Glycolysis

• Fermentation

• Citric acid cycle

• Electron transport chain

Multiple Choice

Where in the membrane do the electrons transfer their energy to?

• The phospholipids

• The nucleus

• The proteins

• The pores

​List of Terms

​Acetyl group - Produced by the breakdown of pyruvate, joins with oxaloacetate in the citric acid cycle

ATP synthase - Enzyme produced during the electron transport chain by the flow of ions in the mitochondrial membrane

Citrate - Substance produced in the citric acid cycle

Glycolysis - First stage in respiration which occurs in the cytoplasm

Citric acid cycle - Second stage in respiration which occurs in the matrix of the mitochondria

Electron transport chain - Third stage in respiration which occurs in the inner membrane of the mitochondria

Oxaloacetate - Combines with acetyl group to form citrate in the citric acid cycle

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​END OF KEY AREA

Thank goodness!​