In-depth section 2.8 notes for IB Biology HL students. I took my exams in July 2022 and got a 7 in Biology HL. The notes are a combination of information from lots of different sources with a main focus on the IB Biology Textbook.
2.8 Cell Respiration
Objectives:
❏ Understanding:
❏ Cell respiration is the controlled release of energy from organic compounds to produce ATP
❏ ATP from cell respiration is immediately available as a source of energy in the cell
❏ Anaerobic cell respiration gives a small yield of ATP from glucose
❏ Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose
❏ Applications:
❏ Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking
❏ Lactate production in humans when anaerobic respiration is used to maximise the power of
muscle contractions
❏ Skills:
❏ Analysis of results from experiments involving measurement of respiration rates in germinating
seeds or invertebrates using a respirometer
❏ Nature of Science
❏ Assessing the ethics of scientific research: the use of invertebrates in respirometer experiments
has ethical implications
Release of energy by cell respiration:
- Cell respiration is a function of life that all living cells perform
- Cell respiration = organic compounds are broken down to release energy, then used in cell
- E.g. energy released in muscle fibres by breaking down glucose into CO2 and water (energy then
used for muscle contraction)
- Source of energy for humans is food
- Carbohydrates and lipids often used
- Amino acids from proteins may be used if we eat more protein than needed
- Plants use carbohydrates or lipids previously made by photosynthesis
- Cell respiration is carried out using enzymes in a controlled way (so that as much possible of the energy
released is retained in a usable form - ATP)
- Adenosine triphosphate
- To make ATP, a phosphate group is linked to adenosine diphosphate (ADP)
- Respiration IS NOT breathing
- ATP is not transferred from cell to cell and all cells require a continuous supply, therefore, cell respiration
is essential in all cells
- Overview of the cellular respiration process in the cell:
, ATP is a source of energy:
- Cells require energy for three main types of activity:
1. Synthesizing large molecules like DNA, RNA and proteins
2. Pumping molecules or ions across membranes by active transport
3. Moving things around inside the cell (e.g. chromosomes, vesicles) or in muscle cells, the protein
fibres that cause muscle contraction
- Energy for all these processes is supplied by ATP
- Advantages of ATP:
- Energy is immediately available
- Released by splitting ATP into ADP and phosphate (ADP and phosphate can then be reconverted
to ATP by cell respiration)
- Why do cells need a continual source of ATP?
- When energy from ATP is used in cells, it is all converted to heat
- Heat energy is useful for keeping organism warm but cannot be reused
- Heat energy lost to environment eventually
- Structure of ATP
- Hydrolysis of ATP to produce energy
- Energy is produced when ATP is hydrolysed
- The same energy was generated during respiration and stored in the energy-rich phosphate bond of
ATP
Glycolysis:
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