Topic 4- Bioenergetics Flashcards
What is photosynthesis?
Photosynthesis is the process by which plants make glucose from sunlight
Where does photosynthesis take place?
Within chloroplasts in leaf palisade cells. They contain chlorophyll, a pigment which absorbs light energy
State the word equation for photosynthesis
Carbon dioxide + water —(light)—> glucose + oxygen
State the symbol equation for photosynthesis
CO2 + H2O —> c6H12O6 + O2
Is photosynthesis an endothermic or exothermic reaction and why?
It is an endothermic reaction in which energy is transferred from the environment to the chloroplasts by light
How can you show that a plant gives off oxygen during photosynthesis?
Using a water plant like Elodea
Collect gas bubbles produced during photosynthesis
The gas will relight a glowing splint as it contains oxygen
What do you have to do in order to carry out an experiment measuring the oxygen production of a plant?
Pond weed is placed in a test tube full with water
The top is sealed with a bung
A capillary tube also containing water leads into the tube and it is attached to a syringe
A lamp is placed at a measured distance from the tube
As it photosynthesises, oxygen is produced, forming a gas tube in the capillary tube
The distance the bubble has moved is measured using a ruler to calculate the volume of oxygen produced
How does temperature affect the rate of photosynthesis?
With an increase in temp, the rate of photosynthesis increases as the kinetic energy of particles is increased.
As the reaction is controlled by enzymes , this trend continues up to a certain temperature until the enzymes begin to denature and the rate of reaction decreases
How does light intensity affect the rate of photosynthesis?
For most plants, the higher the light intensity, the faster the rate of reaction
How does carbon dioxide concentration affect the rate of photosynthesis?
Carbon dioxide is also needed to make glucose
As the concentration of carbon dioxide increases, the rate of reaction increases
How does amount of chlorophyll affect the rate of photosynthesis?
Chlorophyll is a pigment in the leaf that converts light energy to food for the plant and is therefore essential
If, for example, chlorophyll levels are reduced through a magnesium deficiency, then the rate of photosynthesis would decrease
Give examples of leaf adaptations which maximise the rate of photosynthesis
Broad leaves - maximise surface area
Thin leaves - short diffusion distance
Guard cells- control opening of stomata for gaseous exchange and prevent water loss
Chlorophyll present - trap light energy
What is a limiting factor?
An environmental factor which can restrict the rate of photosynthesis e.g light intensity
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 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 which glucose reacts with oxygen to release energy which can be used by cells
What are the equations for aerobic respiration?
Glucose + Oxygen —> carbon dioxide + water (+ energy)
C6H12O6 + 6O2 —-> 6CO2 + 6H2O
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 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
