B4 - Bioenergetics Flashcards
What is Photosynthesis?
An endothermic reaction in which energy is transferred from the environment to the chloroplasts by light.
Word equation for photosynthesis:
(Light)
Carbon dioxide + water -> Glucose +
Oxygen
What factors affect photosynthesis?
Light intensity
Temperature
Amount of chlorophyll
Carbon dioxide concentration
Effect of temperature on photosynthesis
• As temp increases, enzymes involved in photosynthesis work faster (rate of photosynthesis increases)
• If temp keeps increasing, enzymes will denature & rate of photosynthesis falls
Describe how the glucose produced in photosynthesis is used
• Used for respiration
• converted into insoluble starch for storage
• used to produce fat or oil for storage
• used to produce cellulose, which strengthens the cell wall
• used to produce amino acids for protein synthesis.
To produce proteins, plants also use nitrate ions that are absorbed from the soil.
Explain how greenhouses are used to increase the rate of photosynthesis
• Farmers light & heat greenhouses as well as adding extra carbon dioxide.
• Expensive process - extra cost has to be justified by the increase in yield.
Describe cellular respiration
• An exothermic reaction which is continuously occurring in living cells
• The energy transferred supplies all the energy needed for living processes
Organisms need energy for:
• Chemical reactions to build larger molecules
• movement
• keeping warm
Why does aerobic respiration release a great deal of energy?
Because the glucose molecule has been fully oxidised.
Anaerobic respiration in muscles:
• Glucose -> Lactic acid
• As the oxygen is incomplete in anaerobic respiration much less energy is transferred than in aerobic respiration.
Anaerobic respiration in plant & yeast cells:
• Glucose -> ethanol + carbon dioxide
• Anaerobic respiration in yeast cells is called fermentation & has economic importance in the manufacture of bread & alcoholic drinks
Describe what happens in the body during exercise
• Heart rate, breathing rate & breath volume increase to supply muscles with more oxygenated blood
• If insufficient oxygen is supplied anaerobic respiration takes place in muscles. The incomplete oxidation of glucose causes lactic acid to build up & creates oxygen debt.
• During long periods of vigorous activity muscles become fatigued & stop contracting efficiently.
Describe what is meant by the term oxygen debt
The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid & remove it from the cells
Define metabolism
The sum of all the reactions in a cell or the body.
Describe how metabolism converts between different molecules
• Conversion of glucose to starch, glycogen & cellulose
• Formation of lipid molecules from a molecule of glycerol & 3 molecules of fatty acids
• the use of glucose & nitrate ions to form amino acids which are used to synthesise proteins
• respiration
• breakdown of excess proteins to form urea for excretion
