B4: Bioenergetics Flashcards
What is photosynthesis?
- the process by which plants synthesise glucose using light energy from the sun
- light energy is converted into chemical energy
Where does photosynthesis take place?
- within chloroplasts in leaf palisade cells
- they contain chlorophyll, a pigment which absorbs light energy
State the equations for photosynthesis ( word and symbol)
carbon dioxide + water → glucose + oxygen
(light)
symbol: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Is photosynthesis an endothermic or exothermic reaction and Why?
endothermic: energy is transferred from the environment to chloroplasts by light
How can you show that a plant gives off oxygen during photosynthesis?
- using a water plant (eg Elodea), collect gas bubbles produced by photosynthesis
- the gas will relight a glowing splint as it contains oxygen
Give 6 examples of lead adaptations which maximise the rate of photosynthesis
- broad leaves: maximise surface area
- thin leaves: short diffusion distance
- chlorophyll present: trap light energy
- veins: transport water and food substances from xylem and phloem
- air spaces: allow CO₂ to enter and O₂ to leave
- guard cells: control opening of stomata for gaseous exchange and prevent water loss
give the four main factors that affect the rate of photosynthesis
- temperature
- light intensity
- carbon dioxide concentration
- amount of chlorophyll
How does temperature affect the rate of photosynthesis?
- increasing the temperature increases the rate of photosynthesis as the kinetic energy of particles is increased
- the rate decreases past a certain temperature as enzymes become denatured
How does light intensity affect the rate of photosynthesis?
- increasing the light intensity increases the rate of photosynthesis until another factor becomes limiting
How does carbon dioxide concentration affect the rate of photosynthesis?
- increasing the carbon dioxide concentration increases the rate of photosynthesis ( until another factor becomes limiting) as CO₂ is required to make glucose
How does the amount of chlorophyll affect the rate of photosynthesis?
- decreasing the amount of chlorophyll (eg. due to a lack of magnesium) decreases the rate of photosynthesis as chlorophyll is required to absorb light energy
What is a limiting factor?
- an environmental factor which can restrict the rate of photosynthesis
Explain how you can calculate the rate of photosynthesis by measuring oxygen production
- set up bubble potometer apparatus (pondweed in a sealed tube of water attached to a capillary tube and a gas syringe)
- oxygen gas produced causes the bubble in the capillary tube to move. The distance moved by the bubble is used to calculate the volume of oxygen produced
How can farmers use their knowledge of limiting factors to increase their profits?
- they can control temperature, light intensity and CO₂ concentration to achieve the fastest possible rate of photosynthesis
- leading to a greater yield
State the law which describes the relationship between the distance of a light source from a plant and light intensity
inverse square law
- light intensity = 1/distance₂
State 5 uses of the glucose produced during photosynthesis
- respiration
- starch for storage
- cellulose for strength
- amino acid and protein synthesis ( with nitrates)
- lipids for energy storage in seeds
what is aerobic respiration? is it exo or endo
- an exothermic reaction in which glucose reacts with oxygen to release energy which can be used by cells
What are the equations for aerobic respiration? chemical and symbol
glucose + oxygen → carbon dioxide + water ( + energy)
C₆H₁₂O₆ + 60₂ → 6CO₂ + 6H₂O (+ energy)
where does anaerobic respiration take place?
- in the cytoplasm
give 4 uses of the energy released in respiration
- synthesis of larger molecules
- muscle contraction
- maintenance of body temperature
- active transport
what is anaerobic respiration?
- an exothermic reaction in which glucose is broken down to release energy in the absence of oxygen
what is the equation for anaerobic respiration?
glucose →lactic acid (+energy)
Why is anaerobic respiration less efficient than aerobic respiration?
- it is the incomplete breakdown of glucose
- so less energy is transferred
Why can anaerobic respiration lead to muscle fatigue?
- lactic acid builds up in muscles
- preventing efficient contraction
what is oxygen debt?
the amount of oxygen needed to convert lactic acid back into glucose after anaerobic respiration
What is fermentation?
- a type of anaerobic respiration that occurs in yeast cells
What is the equation for fermentation?
glucose → ethanol + carbon dioxide ( + energy)
what is the fermentation reaction used for
- it is used in the production of bread and alcoholic drinks
Give three differences between aerobic and anaerobic respiration?
- aerobic requires oxygen ; anaerobic does not
- aerobic produces CO₂ and water ; anaerobic produces lactic acid or ethanol + CO₂
- aerobic transfers a greater amount of energy
How do muscles store glucose?
As glycogen
Give three changes that take place when muscular activity increases in the body
- heart rate increases and arteries dilate - increases flow of oxygenated blood to muscles
- breathing rate increases and breathing is deeper - increases the rate of gaseous exchange
- stored glycogen is converted back into glucose
How is lactic acid transported away from the muscles?
- blood flowing through the muscles transports lactic acid to the liver, where it is oxidised back to glucose
What is metabolism?
- the sum of all the reactions that take place in a cell or an organism
How do cells use the energy transferred by respiration?
- carry out enzyme-controlled processes
- leading to the synthesis of new molecules
Give 6 examples of metabolic reactions
- glucose into starch / glycogen / cellulose
- glycerol and fatty acids into lipids
- glucose and nitrate ions into amino acids
- photosynthesis
- respiration
- breakdown of excess proteins into urea
