B8 Photosynthesis Flashcards
Which product produced in photosynthesis is ‘food’ for the plant?
Glucose
What gas is used in photosynthesis?
Carbon dioxide
Name the part of a plant cell that contains chlorophyll
Chloroplasts
Which gas is produced in photosynthesis?
Oxygen
What role does chlorophyll play in photosynthesis?
Absorbs energy from light
Write the word equation for photosynthesis
Carbon dioxide + water –> Glucose + oxygen
Why is photosynthesis so important for humans?
- Photosynthesis produces oxygen, without this, we would not be able to breathe and survive.
- Photosynthesis also produces sugars and provides food for us either directly when we eat plants or indirectly as it feeds the animals when we eat meat.
Photosynthesis
The process by which plants make food using carbon, dioxide, water, and light
Chloroplasts
The organelles in which photosynthesis takes place
Chlorophyll
The green pigment contained in the chloroplasts, that absorbs energy from sunlight
Where do plants get carbon dioxide from?
The air
Where do plants get water from?
The soil
Which happens to excess glucose produced in photosynthesis?
It is converted to starch
Leaf adaptations
- Broad leaves, captures more sunlight
- Thin leaves, short diffusion distances
- Veins (containing xylem and phloem), xylem supply water and minerals, phloem transports sugars to other parts of the plant
- Palisade cells, packed full of chloroplasts containing chlorophyll to absorb sunlight for photosynthesis
- Stomata, allows gases in and out of cells
- Air spaces, allows faster diffusion of gases
Diffusion
The movement of particles from an area of high concentration to an area of lower concentration
Is photosynthesis endothermic or exothermic?
Endothermic
The law of limiting factors
At any given moment, the rate of a physiological process is limited by the factor that is at its least favourable value
Which molecule is used to strengthen cell walls?
Cellulose
The rate of photosynthesis - Light
- If there is plenty of light, lots of photosynthesis can take place
- If there is very little or no light, photosynthesis will stop, whatever the other conditions are around the plant
- For most plants, the brighter the light, the faster the rate of photosynthesis
The rate of photosynthesis - Temperature
- Temperature affects all chemical reactions, including photosynthesis
- As the temperature rises, the rate of photosynthesis increases as the reaction speeds up
- However, photosynthesis is controlled by enzymes. Most enzymes are denatured once the temperature rises to around 40-50 degrees
- If the temperature gets too high, the enzymes controlling photosynthesis are denatured and the rate of photosynthesis will fall
The rate of photosynthesis - carbon dioxide concentration
- Plants need carbon dioxide to make glucose
- The atmosphere is only about 0.04% carbon dioxide, this means carbon dioxide often limits the rate of photosynthesis
- Increasing the carbon dioxide concentration will increase the rate of photosynthesis
Carbon dioxide concentration on a sunny day
- On a sunny day, carbon dioxide concentration is the most common limiting factor for plants. The carbon dioxide concentrations around a plant tend to rise at night, because in the dark a plant respires but doesn’t photosynthesise
- As light intensity and temperature increase in the morning, most of the carbon dioxide around the plant gets used up
Light intensity and the inverse square law
- As the distance of the light from the plant increases, the light intensity decreases. That is an inverse relationship
- However the relationship between distance and light intensity is not linear
- light intensity = 1 / distance²
Uses of glucose in plants
- Respiration
- Make and strengthen cellulose cell wall
- Make starch for storage
- Make lipids as energy store
Factors maintained in a greenhouse for optimal plant growth
- High carbon dioxide levels
- Constant light
- Appropriate temperatures
- Regulate watering
