2.8 Cell respiration
Essential idea: Cell respiration supplies energy for the functions of life.
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2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.
2.8.U1 Cell respiration is the controlled release of energy from organic compounds to produce ATP.
Be able to:
Define “cell respiration.”
State the reaction for cellular respiration.
State the types of organic compounds used in cellular respiration by animals and plants.
Cell respiration is the controlled release of energy from organic compounds to produce ATP. The main organic compound used for this process is carbohydrates (glucose), although lipids and proteins can also be digested
organic compounds are broken down to release energy, which can be used in cells
source of organic compounds broken down is food
Carried out using enzymes carefully /controlled so that as much as possble is retained in a usable form
Adenosine triphosphate – form is a chemical substance (ATP)
Making ATP phosphate group is lined to ATP or ADP – energy to carry out the reaction comes from the breakdown of organic compounds
There are two main types of cell respiration:
Anaerobic cellular respiration involves the partial breakdown of glucose in the cytosol for a small yield of ATP
Aerobic cellular respiration utilises oxygen to completely break down glucose in the mitochondria for a larger ATP yield
2.8.U2 ATP from cell respiration is immediately available as a source of energy in the cell.
2.8.U2 ATP from cell respiration is immediately available as a source of energy in the cell.
Be able to:
State three example uses of cellular energy.
Outline energy transfer in the formation and use of ATP.
State three reasons why cellular respiration must be continuously performed by all cells.
ATP (adenosine triphosphate) is a high energy molecule that functions as an immediate source of power for cell processes
Used to synthesizing large molecules like DNA, RNA, and proteins
Pumping molecules or ions across membranes by active transport
Moving things within a cell, like chromosomes, vesicles, muscles cells the protein fibres
The energy is immediately available
Released by splitting ATP into ADP and phosphate –> can be reconverted back to ATP through cell respiration.
One molecule of ATP contains three covalently linked phosphate groups – which store potential energy in their bonds
When ATP is hydrolysed (to form ADP + Pi) the energy stored in the phosphate bond is released to be used by the cell
Cell respiration uses energy stored in organic molecules to regenerate ATP from ADP + Pi (via oxidation)Most energy is converted to heat within a cell – no reusable for cell activities/ eventually lost to the environment
Reason way they need ATP because it’s continual
2.8.U3 Anaerobic cell respiration gives a small yield of ATP from glucose.
2.8.U3 Anaerobic cell respiration gives a small yield of ATP from glucose.
Be able to:
Define “anaerobic respiration”
List three situations in which anaerobic respiration is useful.
Compare anaerobic respiration in yeasts and humans.
Both anaerobic and aerobic respiration pathways begin with the anaerobic breakdown of glucose in the cytosol by glycolysis
glucose is broken down in anaerobic cell respiration without oxygen
glycolysis breaks down glucose (6-C) into two molecules of pyruvate (3C), hydrogen carriers (NADH) from an oxidised precursor (NAD+)ATP yield is small but can be produced quickly (net gain of 2 molecules)
when a short but fast burst of ATP production is needed
when oxygen supplies run out in respiring cells
in environments that are deficient in oxygen
In animals, the pyruvate is converted into lactic acid (or lactate)
In plants and yeasts, the pyruvate is converted into ethanol and carbon dioxide
The Link Reaction transports pyruvate into the mitochondria and 'links' the products of glycolysis with the aerobic processes of the mitochondria.
2.8.U4 Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.
2.8.U4 Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose.
Be able to:
Compare the total amount of ATP made from anaerobic and aerobic respiration.
State the location of aerobic respiration.
Mitochondria
Mitochondria
If oxygen is present, glucose can be more fully broken down to release a greater quantity of energy than in anaerobic cell respiration
ATP two molecules per glucose in anaerobic cell respiration
more then 30 per glucose in aerobic cell respiration
Multiple chemical reactions – dioxide and water are produced
eukaryotic cell- this happens inside the mitochondrion
2.8.A1 Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.
2.8.A1 Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.
Be able to:
Outline how anaerobic respiration in yeast is used in baking.
Outline how anaerobic respiration in yeast is used in ethanol production.
Some organisms such as yeasts only undergo anaerobic respiration and do not require Oxygen. During anaerobic respiration pyruvate from glycolysis is made into Lactate in animals, and Ethanol and Carbon Dioxide in yeast. This is why when yeast is added to bread dough bubbles form and it rises.
2.8.A2 Lactate production in humans when anaerobic respiration is used to maximize the power of muscle contractions.
2.8.A2 Lactate production in humans when anaerobic respiration is used to maximize the power of muscle contractions.
Be able to:
State the condition in which humans would perform anaerobic respiration.
Outline production of lactate in humans during anaerobic respiration.
Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose. 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 maximize the power of muscle contractions
Muscle contractions require the expenditure of high amounts of energy and thus require high levels of ATP. When exercising at high intensity, the cells’ energy demands will exceed what the available levels of O2 can supply aerobically. Therefore the body will begin breaking down glucose anaerobically to maximise ATP production. This will result in an increase in the production of lactic acid, which leads to muscle fatigue.
When the individual stops exercising, oxygen levels will increase and lactate will be converted back to pyruvate. Although carbohydrates, lipids and proteins can all be consumed as energy sources, only carbohydrates will typically undergo anaerobic respiration
2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer.
2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer.
Be able to:
Outline the use of a respirometer to measure cellular respiration rate.
A respirometer is a device that determines an organism’s respiration rate by measuring the rate of exchange of O2 and CO2. The living specimen (e.g. germinating seeds or invertebrate organism) is enclosed in a sealed container
Carbon dioxide production can be measured with a data logger or by pH changes if the specimen is immersed in water
When an alkali is included to absorb CO2, oxygen consumption can be measured as a change in pressure within the system. The pressure change can be detected with a data logger or via use of a U-tube manometer
Factors which may affect respiration rates include
temperature
hydration
light (plants)
age
activity levels
An increase in carbon dioxide levels will indicate an increase in respiration (CO2 is a product of aerobic respiration)
A decrease in oxygen levels will indicate an increase in respiration (O2 is a requirement for aerobic respiration)
2.8.A1 Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.
2.8.A1 Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking.
Be able to:
Outline how anaerobic respiration in yeast is used in baking.
Outline how anaerobic respiration in yeast is used in ethanol production.
Some organisms such as yeasts only undergo anaerobic respiration and do not require Oxygen. During anaerobic respiration pyruvate from glycolysis is instead made into Lactate in animals, and Ethanol and Carbon Dioxide in yeast. This is why when yeast is added to aa cake bubbles form in the bread and the cake rises. Because of the Carbon Dioxide being produced.
2.8.A2 Lactate production in humans when anaerobic respiration is used to maximize the power of muscle contractions.
2.8.A2 Lactate production in humans when anaerobic respiration is used to maximize the power of muscle contractions.
Be able to:
State the condition in which humans would perform anaerobic respiration.
Outline production of lactate in humans during anaerobic respiration.
Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose. 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 maximize the power of muscle contractions
Muscle contractions require the expenditure of high amounts of energy and thus require high levels of ATP. When exercising at high intensity, the cells’ energy demands will exceed what the available levels of O2 can supply aerobically. Therefore the body will begin breaking down glucose anaerobically to maximise ATP production. This will result in an increase in the production of lactic acid, which leads to muscle fatigue.
When the individual stops exercising, oxygen levels will increase and lactate will be converted back to pyruvate. Although carbohydrates, lipids and proteins can all be consumed as energy sources, only carbohydrates will typically undergo anaerobic respiration
2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer.
2.8.S1 Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer.
Be able to:
Outline the use of a respirometer to measure cellular respiration rate.
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