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
Word: carbon dioxide + water → glucose + oxygen
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 during photosynthesis. The
gas will relight a glowing splint as it contains
oxygen.
Give examples of leaf 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 to leaves via xylem, remove photosynthesis
products via phloem.
● Air spaces - allow CO2 to enter and O2 to leave.
● Guard cells - control opening of stomata for gaseous exchange and
prevent water loss.
What are 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 eg.
light intensity.
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.
State 5 uses of the glucose produced
during photosynthesis
● Respiration ● Starch for storage ● Cellulose for strength ● Amino acid and protein synthesis (combined with nitrates) ● Lipids for energy storage in seeds
What is aerobic respiration?
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? (word and symbol)
Glucose + oxygen → carbon dioxide + water (+energy)
C6H12O6 + 6O2 → 6CO2 + 6H2O (+energy)
Where does aerobic respiration take place?
In the mitochondria
Why do organisms require the energy
released by 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 word equation for anaerobic respiration?
Glucose → lactic acid (+energy)
Why is anaerobic respiration less
efficient than aerobic respiration?
Glucose is not completely broken down,
so less energy is transferred.
Why can anaerobic respiration lead to muscle
fatigue?
Lactic acid (product of anaerobic respiration)
builds up in muscles, preventing efficient
contraction.
What is fermentation?
A type of anaerobic respiration that
occurs in yeast cells.
What is the equation for fermentation?
Glucose → ethanol + carbon dioxide (+energy)
Why is the fermentation reaction important?
It is used in the production of bread and
alcoholic drinks.
What are the 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
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?
To continuously carry out enzyme-controlled
processes which lead to the synthesis of new
molecules.
Give 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
