B9: Respiration


B9.1 Aerobic Respiration

During aerobic respiration glucose reacts with oxygen transferring energy. Carbon dioxide and water are the waste products of the reaction. This reaction is exothermic since it transfers energy to the environment, more so when bonds form than when bonds are broken. The energy transferred heats the environment and is used for cellular reactions.

glucose + oxygen -> carbon dioxide + water

C6H12O6 + 6O2 -> 6CO2 + 6H2O

More muscle cells means more mitochondria are needed so the amount of aerobic respiration needed is met.

The cytoplasm is the site of anaerobic respiration and is where enzymes are made.

The nucleus has the genetic code for enzymes involved in respiration.

Mitochondria is the site of aerobic respiration. They have a folded inner membrane for a larger surface area for the enzymes involved in respiration.

The cell membrane allows substances to enter and exit the cell freely.

The positive test result for carbon dioxide is when limewater goes cloudy: the higher the concentration of CO2, the quicker it goes cloudy.

The energy transferred in respiration has several uses.

  • Build up large molecules from smaller ones
  • Break larger molecules down into smaller ones
  • Contraction of muscles
  • Maintain a constant internal body temperature
  • Move mineral ions (plants)
  • Convert nutrients into amino acids which are used to make proteins (plants)
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B9.2 Response to exercise

Glucose is stored as glycogen and is converted back when it is necessary to transfer energy needed for contraction.

During exercise:

  • Muscles produce more carbon dioxide.
  • Heart rate increases and arteries dilate. Oxygen and glucose are supplied faster for the increased rate of cellular respiration. Also, carbon dioxide is removed from the muscles faster.
  • Breathing rate increases and breathing becomes deeper. Oxygen is picked up by red blood cells faster and carried to muscles faster. Carbon dioxide is removed from the muscles faster.
  • Glycogen is converted into glucose to supply fuel.
  • Respiration rises to supply muscle cells with increased energy levels for exercise.
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B9.3 Anaerobic Respiration

When blood cannot supply oxygen to the muscles quick enough, glucose is still transferred to muscle cells (anaerobic respiration).

Anaerobic respiration isn't as efficient as aerobic respiration since the breakdown of glucose molecules is incomplete and so less energy is transferred. The product is lactic acid.

glucose -> lactic acid + energy

Lactic acid causes fatigue as it builds up in muscles (oxygen debt). You are less likely to get anaerobic respiration if you're fit since the body can keep a good supply of oxygen going to the muscles for a long time.

Lactic acid is broken down by oxygen to produce carbon dioxide and water. Heart rate and breathing rate stay high to supply extra oxygen needed to pay off the oxygen debt. The bigger the debt, the longer the heart rate and breathing rate stay high.

lactic acid + oxygen -> carbon dioxide + water

When plants respire anaerobically, ethanol and carbon dioxide are made. Microorganisms are used to make bread and alcohol through respiration.

glucose -> ethanol + carbon dioxide

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B9.4 Metabolism and the Liver

Metabolism is the sum of all the reactions occurring in a cell or body. The most common metabolic reactions include:

  • respiration
  • photosynthesis
  • forming urea from excess proteins
  • forming nutrients from amino acids
  • forming lipase
  • conversion of glucose to glycerol, cellulose, and starch

The liver has several purposes:

  • detoxifies poisons
  • passes breakdown products into the blood
  • breaks down worn out blood cells and stores the iron until more blood cells are needed

The liver's role in respiration:

  • Lactic acid is transported to the liver, where it is converted into glucose.
  • If the glucose isn't needed, it's stored as glycogen.
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