Cell respiration

Question 1

For what functions of the body is energy required?

Answer 1

• 20-25% of all energy is needed by brain cells, muscle movement, cell repair, digestion of food, pumping ions across a membrane, etc.
• Energy in the form of ATP

Question 2

What is cellular respiration? What controls the process and which 3 processes generate energy (ATP)?

Answer 2

• The gradual and controlled release of energy by breaking down organic compounds to produce ATP
• It involves enzymes that control the process to ensure that energy is produced when it is needed
• Glucose is mainly used (lipids and proteins too)
• Glycolysis, Krebs cycle and electron transport chain that generate energy in the form of ATP

Question 3

Where does glycolysis, the Krebs cycle and electron transport chain occur?

Answer 3

• Glycolysis: in the cytoplasm
• Krebs cycle: mitochondria, in the matrix
• Electron transport chain: mitochondria, inner membrane of the mitochondrial envelope

Question 4

What is the chemical equation of respiration?

Answer 4

C6H12O6 + 6O2 —> 6CO2 + 6H20 + ATP (energy)

Question 5

What is ATP?

Answer 5

• Adenosine triphosphate, a high energy molecule that functions as an immediate source of power for cell processes
• An ATP molecule is made of three phosphates which store potential energy in their bonds
• ATP is immediately available as a source of energy in the cell

Question 6

How is ADP formed?

Answer 6

• ATP is hydrolyzed (water added), to form ADP + Pi and energy
• The energy stored in the phosphate bond is released and used by the cell
• The stored energy in organic molecules is used to generated ATP from ADP + Pi by oxidation
• Energy is generated during respiration and stored in the high energy bond
  Check book

Question 7

What is anaerobic cell respiration?

Answer 7

• Partial breakdown of glucose in the cytosol by glycolysis for a small yield of ATP
• Glycolysis breaks down glucose into two molecules of pyruvate
• Occurs in the absence of oxygen, no further ATP produced
• Takes place in the cytoplasm
• Conversion from pyruvate to lactate or ethanol/CO2 is reversible

Question 8

How does anaerobic respiration take place in animals? What is the equation?

Answer 8

• The pyruvate is converted into lactic acid (lactate) when there is insufficient supply of oxygen during exercise
• This is however done to maximize the power of muscle contractions
• Small amount of ATP produced, the lactic acid might cause soreness in the muscles which is caused by microscopic damages in the muscle fibres

Glucose → lactate + 2 ATP molecules

Question 9

How does anaerobic respiration take place in yeast? What is the equation?

Answer 9

• Alcoholic fermentation, to produce types of food and beverages
• Yeast respires anaerobically to produce ethanol and CO2, the CO2 makes the bread rise and ethanol evaporates

Glucose → ethanol + carbon dioxide + 2 ATP molecules

Question 10

How is anaerobic respiration used in yeast?

Answer 10

• Form of fermentation which involves the breakdown of carbohydrates
• The products are ethanol and carbon dioxide which are used in bread making and alcohol
• In bread making, CO2 makes the dough rise and ethanol evaporates
• In alcohol, ethanol acts as an intoxicating agent

Question 11

What is aerobic cell respiration?

Answer 11

• Requires oxygen and takes place in the cytoplasm and mitochondrion
• Pyruvate broken down into CO2 and H2O and a lot of ATP (34-36 molecules)
• It begins with glycolysis (which is anaerobic) but aerobic involves more steps
• All 4 steps of cellular respiration are completed: glycolysis, link Rxn, Krebs cycle and chemiosmosis
• C6H12O6 + O2 –> 6CO2 +6H2O + ATP production

Question 12

Why is the yield of ATP molecules greater in aerobic respiration compared to anaerobic respiration?

Answer 12

• Glucose is systematically and gradually broken down to 6CO2 molecules
• Each step produces potential energy, which can be converted into ATP in the electron transport chain
• The ATP is the used to perform the activity, whereas in anaerobic respiration only produces ATP in glycolysis

Question 13

What is a respirometer? How does it measure respiration rates?

Answer 13

• It determines an organism’s respiration rate by measuring the rate of exchange of O2 and CO2
• The organism is in sealed container. The CO2 production is measured with a data logger or when an alkali is included to absorb CO2
• The oxygen consumption can be measured by a change in pressure within the system
• Factors affecting respiration rates: temperature, hydration, light, age and activity levels, increase CO2 concentration and decrease O2 levels means increased respiration rate
• Temperature must remain constant, by placing it in a water bath