2.8 Flashcards
Cell respiration
Cell respiration is the controlled release of energy from organic compounds to produce ATP
Main organic compound used in cell respiration
The main organic compound used for this process is carbohydrates (glucose), although lipids and proteins can also be digested
There are two main types of cell respiration:
Anaerobic and Aerobic
Anaerobic cell respiration
Anaerobic respiration involves the partial breakdown of glucose in the cytosol for a small yield of ATP
Aerobic cell respiration
Aerobic respiration utilises oxygen to completely break down glucose in the mitochondria for a larger ATP yield
ATP (adenosine triphosphate) is…
a high energy molecule that functions as an immediate source of power for cell processes
One molecule of ATP contains three…
covalently linked phosphate groups – which store potential energy in their bonds
When ATP is hydrolysed it forms?
ADP + Pi, the energy stored in the phophate 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)
glycolysis
glycolysis begins with the anaerobic breakdown of glucose in the cytosol. Both anaerobic and aerobic respiration pathways begin with this.
Glycolysis breaks down glucose (6-C) into
two molecules of pyruvate (3C), and also produces:
- Hydrogen carriers (NADH) from an oxidised precursor (NAD+)
- A small yield of ATP (net gain of 2 molecules)
Anaerobic respiration proceeds in the absence of…
oxygen and does not result in the production of any further ATP molecules
pyruvate in animals
In animals, the pyruvate is converted into lactic acid (or lactate)
pyruvate in plants and yeast
In plants and yeasts, the pyruvate is converted into ethanol and carbon dioxide
The purpose of anaerobic respiration is to…
restore stocks of NAD+ – as this molecule is needed for glycolysis
- By restoring stocks of NAD+ via anaerobic pathways, the organism can continue to produce ATP via glycolysis
The conversion of pyruvate into lactic acid (animals) or ethanol and CO2 (plants / yeasts) is…
reversible
- Hence, pyruvate levels can be restored once oxygen is present and a greater yield of ATP may be produced aerobically
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. Hence…
the body will begin breaking down glucose anaerobically to maximise ATP production
exercising at high intensity 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
what will undergo anaerobic respiration?
Although carbohydrates, lipids and proteins can all be consumed as energy sources, only carbohydrates will typically undergo it.
how do the conditions of cell respiration change with increasing energy demand?
- At high intensities, the aerobic consumption of fats is decreased while the anaerobic consumption of sugars increases
- Consequently, lactate levels will increase at higher levels of exercise intensity
Aerobic cell respiration requires…
the presence of oxygen and takes place within the mitochondrion
Pyruvate is broken down into…
carbon dioxide and water, and a large amount of ATP is produced (~34 – 36 molecules)
Although aerobic respiration typically begins with glycolysis in carbohydrates…
glycolysis itself is an anaerobic process
Aerobic respiration consists of…
3 things
the link reaction, citric acid cycle (or Krebs cycle) and the electron transport chain
Anaerobic respiration (fermentation) involves the…
breakdown of carbohydrates in the absence of oxygen
In yeasts, fermentation results in the production of…
ethanol and carbon dioxide – which can be used in food processing:
Role of yeast in bread
Carbon dioxide causes dough to rise (leavening), the ethanol evaporates during baking
Role of yeast in alcohol
Ethanol is the intoxicating agent in alcoholic beverages (concentrations above ~14% damage the yeast)
Bacterial cultures can also undergo fermentation to produce a variety of food products
Yogurt / Cheese – Bacteria produce lactic acid anaerobically, which modifies milk proteins to generate yogurts and cheeses
A respirometer is…
a device that determines an organism’s respiration rate by measuring the rate of exchange of O2 and CO2
Factors which may affect respiration rates include…
temperature, hydration, light (plants), age and 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)
Carbohydrates are preferable as a ready-made energy source because:
- They are easier to transport and digest (unlike lipids)
- They don’t produce nitrogenous wastes (unlike proteins)
Carbohydrates can be broken down into…
monosaccharides (e.g. glucose), which are able to be used in glycolysis
Lipids (i.e. triglycerides) can be broken down into…
glycerol and fatty acids, which are able to be used in aerobic respiration
Proteins can be broken down into…
amino acids, which are also capable of being used in aerobic respiration
There are several key differences between anaerobic and aerobic respiration, including:
- Overall energy yield
- Products formed
- Location of processes
