Nutrition Part 1
Nutrition in flowering plants
Photosynthesis is an endothermic reaction. This means that energy from sunlight is transferred to
the chloroplasts in green plants. It happens inside chloroplasts. The sunlight is absorbed by the
green pigment chlorophyll in plants.
Oxygen is also produced in photosynthesis, and although some of it is used in the plant for
respiration, most is not needed and is given out as a waste product.
Most of the glucose formed in photosynthesis is converted into other substances, including starch.
Starch molecules are large carbohydrates made of lots of glucose molecules joined together.
Starch is insoluble and so can be stored in cells without affecting water movement into and out of
the cell by osmosis.
The products and raw materials in a plant from photosynthesis
- Produce starch for storage
- Forms cellulose to make cell walls
- Produce amino acids when combined with nitrogen and other mineral ions absorbed by
roots
Raw materials: carbon dioxide and water
, Questions - page 70
1. Write the balanced symbol equation for photosynthesis
2. Annotate the equation to show where each of the reactants comes from and where each of
the products go to.
3. Give four examples of how glucose is used in a plant.
Adaptations for Photosynthesis
Photosynthesis takes place mainly in the leaves, but also any place with green chlorophyll.
External Adaptations of the leaf that help maximise the rate of photosynthesis
1. Leaf is broad and long to give a large surface area to absorb a lot of light
2. Leaf stalk (petiole) holds the leaf so that is faces the Sun
3. Network of veins (vascular bundles) carry water and mineral ions to the leaf, and food
away from it
4. Leaf is thin to allow substances to move quickly between and into cells
5. Leaf is green - cells contain chlorophyll to absorb light energy
Internal Adaptations of the leaf also helps to maximise the rate of capture of light energy so
maximise the rate of photosynthesis
1. The transparent epidermis allows as much light as possible to reach the photosynthesising
cells within the leaf
2. The palisade cells, where most photosynthesis takes place, are tightly packed together in
the uppermost half of the leaf so that as many as possible can receive sunlight
3. Chloroplasts containing chlorophyll are concentrated in cells in the uppermost half of the
leaf to absorb as much sunlight as possible
4. Air spaces in the spongy mesophyll layer allow the movement of gases (co2 and 02)
through the leaf to and from cells
5. A leaf has a large internal surface area to volume ratio to allow the efficient absorption of
carbon dioxide and removal of oxygen by the photosynthesising cells.
6. Many stomata allow the movement of gases into and out of the leaf
7. Phloem tissue transports sucrose, formed from glucose in photosynthesizing cells, away
from the leaf. Xylem tissue transports water and mineral ions to the leaf from the roots.
Questions - page 72
1. List as many adaptations of a plant
leaf for photosynthesis as you can
2. Explain why a large surface area
inside the leaf is essential for
photosynthesis
3. Explain why a transparent epidermis
is an adaptation for photosynthesis
Nutrition in flowering plants
Photosynthesis is an endothermic reaction. This means that energy from sunlight is transferred to
the chloroplasts in green plants. It happens inside chloroplasts. The sunlight is absorbed by the
green pigment chlorophyll in plants.
Oxygen is also produced in photosynthesis, and although some of it is used in the plant for
respiration, most is not needed and is given out as a waste product.
Most of the glucose formed in photosynthesis is converted into other substances, including starch.
Starch molecules are large carbohydrates made of lots of glucose molecules joined together.
Starch is insoluble and so can be stored in cells without affecting water movement into and out of
the cell by osmosis.
The products and raw materials in a plant from photosynthesis
- Produce starch for storage
- Forms cellulose to make cell walls
- Produce amino acids when combined with nitrogen and other mineral ions absorbed by
roots
Raw materials: carbon dioxide and water
, Questions - page 70
1. Write the balanced symbol equation for photosynthesis
2. Annotate the equation to show where each of the reactants comes from and where each of
the products go to.
3. Give four examples of how glucose is used in a plant.
Adaptations for Photosynthesis
Photosynthesis takes place mainly in the leaves, but also any place with green chlorophyll.
External Adaptations of the leaf that help maximise the rate of photosynthesis
1. Leaf is broad and long to give a large surface area to absorb a lot of light
2. Leaf stalk (petiole) holds the leaf so that is faces the Sun
3. Network of veins (vascular bundles) carry water and mineral ions to the leaf, and food
away from it
4. Leaf is thin to allow substances to move quickly between and into cells
5. Leaf is green - cells contain chlorophyll to absorb light energy
Internal Adaptations of the leaf also helps to maximise the rate of capture of light energy so
maximise the rate of photosynthesis
1. The transparent epidermis allows as much light as possible to reach the photosynthesising
cells within the leaf
2. The palisade cells, where most photosynthesis takes place, are tightly packed together in
the uppermost half of the leaf so that as many as possible can receive sunlight
3. Chloroplasts containing chlorophyll are concentrated in cells in the uppermost half of the
leaf to absorb as much sunlight as possible
4. Air spaces in the spongy mesophyll layer allow the movement of gases (co2 and 02)
through the leaf to and from cells
5. A leaf has a large internal surface area to volume ratio to allow the efficient absorption of
carbon dioxide and removal of oxygen by the photosynthesising cells.
6. Many stomata allow the movement of gases into and out of the leaf
7. Phloem tissue transports sucrose, formed from glucose in photosynthesizing cells, away
from the leaf. Xylem tissue transports water and mineral ions to the leaf from the roots.
Questions - page 72
1. List as many adaptations of a plant
leaf for photosynthesis as you can
2. Explain why a large surface area
inside the leaf is essential for
photosynthesis
3. Explain why a transparent epidermis
is an adaptation for photosynthesis
