What is the main substrate in energy production and how is it obtained?
glucose, obtained through digestion of carbohydrates form the food eaten
What is cellular respiration?
- oxidation process of organic molecules through several stages to release energy
What are the 2 types of respiration?
- aerobic respiration (occurs in presence of oxygen)
- anaerobic respiration (occurs in the absence if oxygen)
- fermentation: alternative pathway to obtain energy besides cellular respiration (breakdown of glucose is incomplete in conditions of limited/without oxygen)
What is aerobic respiration? (2)
- breakdown of glucose involving oxygen to produce chemical energy
- oxygen is used to oxidise glucose to produce CO2, water & energy
What is the first process in aerobic respiration? (3)
- begins with glycolysis process (breakdown of glucose by enzymes)
- occurs in the cytoplasm
- 1 glucose molecule break down into 2 pyruvate
What is the following process of aerobic respiration after glycolysis? (3)
- occurs in mitochondrion
- pyruvate oxidised through a series of reaction to produce CO2, water & energy
- large amount of energy used to produce adenosine triphosphate (ATP) molecules
word equation for glycolysis and oxidation of pyruvate?
Glycolysis Oxidation of Pyruvate
Glucose → pyruvate → CO2 + water + energy
(occurs in cytoplasm) (occurs in mitochondrion)
How does aerobic respiration occur? ()
- ATP molecules produced when a group of non-organic phosphate is added to adenosine diphosphate (ADP)
ADP + phosphate (use energy) → ATP
- ATP molecules have weak phosphate links.
- When the phosphate links on ATP molecules are broken, the energy
released is supplied to cells to help us carry out our daily activities.ATP (release energy) → ADP + phosphate
Word equation for complete process of glucose oxidation.
Glucose + oxygen → Carbon dioxide + water + energy (2898 kJ)
What is fermentation? (3)
- incomplete breakdown of glucose in conditions of limited oxygen or
without oxygen. - different from aerobic respiration in its metabolic pathway after the glycolysis stage.
- After glycolysis, the pyruvate produced will undergo either
alcohol fermentation or lactic acid fermentation.
What is alcohol fermentation?
The incomplete breakdown of glucose to ethanol, carbon dioxide and energy.
Glucose → Ethanol + carbon dioxide + energy (210 kJ)
What are the 2 examples of alcohol fermentation? (5)
Yeast:
• Ethanol is used in the making of beer and wine.
• The released carbon dioxide makes bread dough rise.
Plants:
• Paddy plants that grow in waterlogged areas with less oxygen are able to carry out alcohol fermentation.
• Ethanol produced in the tissues during the fermentation process is toxic to most plants but the cells of paddy plants have a higher tolerance for ethanol compared to other species.
• Paddy plants produce plenty of alcohol dehydrogenase enzymes that can break down ethanol molecules into non-toxic carbon dioxide.
What is lactic acid fermentation?
The breakdown of glucose into lactic acid and energy.
Glucose → Lactic acid + energy
What are 2 examples of lactic acid fermentation? (lactobacillus-3)
Lactobacillus
• The bacteria Lactobacillus carries out milk fermentation to produce yoghurt.
• Lactobacillus acts on the lactose (milk sugar) and turns it into lactic acid.
• The lactic acid will then coagulate casein (milk protein) to produce yoghurt.
• Lactic acid is the source of a sour taste in yoghurt.
What are 2 examples of lactic acid fermentation? (human muscle cells-7)
• This process is carried out by the muscle cells during vigorous training.
• During vigorous training, the rate of oxygen used exceeds the oxygen supplied by the blood circulatory system.
• The muscle is in an oxygen-deficiency state and is said to undergo oxygen debt.
• During this process, glucose cannot break down completely. For each glucose molecule that is broken down, only two ATP molecules/150 kJ energy will be produced.
• The produced lactic acid accumulates until it reaches a level of concentration that can cause fatigue and muscle cramps.
• Once the vigorous activity stops, the intake of excess oxygen will oxidise the lactic acid into carbon dioxide, water and energy.
- When all the lactic acid has been expelled, the oxygen debt is repaid.
What are the similarities between aerobic respiration and fermentation? (5)
- The breakdown process of glucose and its conversion to chemical energy
- Produces chemical energy in the form of ATP
- The process begins with glycolysis when glucose is converted to pyruvate
- Occurs in yeast, bacteria, animals and plants
- The process begins in the cytoplasm
What are the differences between aerobic respiration and fermentation? (5)
Aerobic Respiration(AR) Fermentation (F) *not actual abbreviations
AR: The breakdown process of glucose is completed in the presence of oxygen.
F: The breakdown process of glucose is incomplete without oxygen or in limited oxygen conditions.
AR: Occurs in cytoplasm and mitochondrion.
F: Occurs in cytoplasm.
AR: Produces water.
F: Does not produce water.
AR: Glucose is oxidised completely into carbon
dioxide and water.
F:Glucose is not oxidised completely into ethanol
and carbon dioxide or lactic acid.
AR: One molecule of glucose generates 2898 kJ of energy
F: One molecule of glucose generates 210 kJ (alcoholic fermentation) or 150 kJ (lactic acidfermentation) of energy
