Respiration
- It is a chemical reaction that uses oxygen to release energy from glucose.
- In order to respire, we need oxygen.
Word Equation:
Glucose + Oxygen → Carbon dioxide + Water (+energy)
Symbol Equation:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
- Respiration is an enzyme-controlled reaction that occurs in the mitochondria.
- The more active a cell is, the more mitochondria it contains.
- Because respiration is an exothermic reaction that releases energy, it also serves to regulate body temperature.
ATP:
B1. 3b
- The energy released by respiration is mostly captured by a molecule → ATP.
- ATP is the energy carrier of all cells.
- Every cell must make its own ATP. You cannot share.
- You cannot assert the creation or release of energy.
- Cells use ATP to power reactions. E.g., muscle contraction, protein synthesis, and growth.
Exercise:
- Your heart rate increases during exercise as your blood slowly pumps quicker. This means the blood is removing the CO₂ quicker to make room for the O₂ by taking it to the lungs. Your respiration rate is accelerated due to the need for oxygen to reach the muscle cells more quickly.
- After exercise, you need to inhale more air to facilitate faster oxygen delivery to the muscle cells, enabling them to respire more efficiently. You need to get rid of CO₂ and make ATP.
- Cellular respiration is a universal chemical process that continuously occurs and supplies ATP in all living cells.
Anaerobic Respiration
B1. 3c
- During hard exercise, aerobic respiration can’t provide enough energy → ATP for muscle contraction.
→ This is because oxygen can’t get to the muscle quickly enough.
- Therefore, anaerobic respiration must also occur. Aerobic respiration still happens at the same time.
- Anaerobic respiration releases some energy from glucose without using oxygen.
Word Equation:
Glucose → Lactic acid (+ energy)
Symbol Equation:
C₆H₁₂O₆ → 2C₃H₆O₃ (+energy) → Glucose is split in half.
- Anaerobic respiration only partially breaks down glucose molecules compared to aerobic respiration, as glucose releases less energy (per glucose molecule).
- Lactic acid can build up in the muscles.
- This leads to muscle fatigue and soreness.
- The lactic acid in the blood and muscles is toxic and requires oxygen to break down.
- Red blood cells are unable to perform this function; instead, the liver takes them from the muscles. A rapid heart rate allows this to happen.
- The extra oxygen required to remove lactic acid is called the oxygen debt.
- After exercise, you continue to breathe heavier or faster for a few minutes to get enough oxygen and break down lactic acid. It also allows aerobic respiration to continue.
Differences:
Respiration in Yeast
- Anaerobic respiration can happen in yeast. Yeast cells don't have the same enzymes as mammals for anaerobic respiration, so they carry out fermentation.
Equations:
- Word: Glucose → Ethanol + Carbon dioxide
- Symbol: C₆H₁₂O₆ → 2C₂H₅OH (aq) + 2CO₂ (aq)
- This type of respiration provides less ATP for yeast than aerobic respiration because the glucose is not completely broken down, so there is still energy left over in the ethanol.
- Fermentation can be used for rising bread and making alcoholic drinks.
- Plant roots can also respire anaerobically via the fermentation pathway, though it’s a rare occurrence. When the roots lack oxygen, this process might become essential. E.g., when roots are waterlogged.
Biological Molecules
B1.3 d,e,f
- Monomer: A single individual unit.
- Polymer: Lots of monomers joined together.
- Starch: A huge polymer made out of glucose.
Carbohydrates:
- Amino acids are monomers that come in a variety of forms.
- Proteins are polymers.
Lipids
Lipids don’t form polymers and don’t bond with each other.
Respiration Glossary
- Aerobic Respiration: A series of enzyme-controlled metabolic reactions that occur in all cells.
- Amino Acids: The monomers of protein. There are 20 different types of amino acids.
- Anaerobic Respiration: Respiration without oxygen.
- ATP: The molecule that provides energy during respiration.
- Carbohydrase: The type of enzymes used to break down carbohydrates. E.g., amylase.
- Carbohydrates: A polymer of single sugar units bonded together to form a large, complex molecule. Carbohydrates provide the body with energy.
- Heat: Lots of the energy from respiration is used to make ATP, but some is also released as heat, so respiration is an exothermic reaction.
- Lipids: Molecules made of fatty acids and glycerol. Fats and oils contain them, providing insulation and buoyancy. They also serve as a store of energy.
- Monomer: A single unit of a polymer. E.g., sugar units and amino acids.
- O₂ debt: The extra oxygen taken in after exercise, which is used to break down lactic acid in the liver.
- Polymer: Many monomers bonded together. E.g., DNA, starch, and proteins.
- Protease: The type of enzyme that can break down proteins.
- Protein: Polymers of amino acids. Protein comes in various forms, such as insulin, collagen, and keratin. The body uses it for the growth and repair of tissues.
- Sugar: The monomers of carbohydrates.
- Vitamins and Minerals: Required by the body to maintain excellent health.