4.2 Respiration

Is cellular respiration an exothermic or endothermic reaction?

Exothermic

What is aerobic respiration?

Uses oxygen to release energy from glucose

What is anaerobic respiration?

Releases energy from glucose without using oxygen

How can respiration take place in cells to transfer energy?

• Aerobically

• Anaerobically

What do organisms need energy for? (3)

• Chemical reactions — build larger molecules

• Movement

• Keeping warm

What is the word equation for aerobic respiration?

glucose + oxygen → carbon dioxide + water

What is the balanced symbol equation for aerobic respiration?

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

What is the equation for anaerobic respiration in muscles?

glucose → lactic acid

Why is less energy transferred in anaerobic respiration than in aerobic respiration?

Incomplete oxidation of glucose

What is the equation for anaerobic respiration in plant and yeast cells?

glucose → ethanol + carbon dioxide

What does fermentation have economic importance in the manufacture of?

• Bread

• Alcoholic drinks

What is fermentation?

Anaerobic respiration in yeast cells

What does the number if mitochondria in a cell tell you?

How active the cell is

How are mitochondria adapted for aerobic respiration?

• Folded inner membrane → large SA

  • for enzymes

• During exercise the human body reacts to the increased demand for energy.

What increases during exercise and why?

• Heart rate

• Breathing rate

• Breath volume

  • provide muscles with more oxygenated blood

During exercise, what happens if insufficient oxygen is supplied to the muscles?

Anaerobic respiration

During anaerobic respiration in muscles, what does the incomplete oxidation of glucose cause?

A build up of lactic acid → oxygen debt

What happens during long periods of vigorous activity?

Muscles become fatigued → inefficient contraction

What does the body do to reduce the build up of lactic acid from anaerobic respiration?

Blood flowing through muscles transports lactic acid to the liver — converted back into glucose

What is oxygen debt?

Amount of extra oxygen needed after exercise → reacts with lactic acid and removes from cells

What is the equation for oxygen debt repayment?

lactic acid + oxygen → carbon dioxide + water

Fully explain the increase in heart rate during exercise. (5)

• Heart rate increases — pumps greater volume of oxygenated blood → muscles

• Delivers faster and greater supply of oxygen + glucose

• Increased rate of aerobic respiration

• Releases more energy — used for muscle contraction

• Faster blood flow:

  • removes carbon dioxide from muscles more quickly

  • removes lactic acid more rapidly — prevents oxygen debt + muscle fatigue

Fully explain the increase in breathing rate during exercise.

• Breathing rate + breath volume increase — brings more air and oxygen to lungs

• Allows more oxygen to enter blood → delivered to muscles

• Muscles use extra oxygen to increase rate of aerobic respiration

• Increased respiration releases extra energy — muscle contraction

• Faster breathing rate — removes carbon dioxide from blood more quickly

  • carbon dioxide must be removed — waste product continuously produced by increased rate of respiration

During exercise, why is the glycogen stored in the muscles converted back to glucose?

• Muscles need lots of extra energy to contract

• Glycogen converted back to glucose — extra energy

• Increases rate of respiration

What is metabolism?

Sum of all reactions in a cell or the body

How is the energy transferred by respiration in cells is used by the organism?

Continual enzyme controlled processes of metabolism — synthesise new molecules

What does metabolism include? (5)

• Conversion of glucose → starch, glycogen, and cellulose

• Formation of lipid molecules from molecule of glycerol and three molecules of fatty acids

• Use of glucose and nitrate ions to form amino acids — used to synthesise proteins

• Respiration

• Breakdown of excess proteins — forms urea for excretion

• Figure 8 shows an axolotl.

Explain why an axolotl may die in water with a low concentration of oxygen. [4 marks]

• Concentration gradient of oxygen is shallower

• Less oxygen diffuses into blood

• Less aerobic respiration occurs → less energy released so less metabolism