Biology Chapter 6 – Review
Nutrition: taking in useful substances
Photosynthesis: the process by which plants synthesize carbohydrates from raw materials
using energy from light
6CO2 + 6H2O ->> C6H12O6 + 6O2
carbon dioxide + water ->(sunlight and chlorophyll)> glucose + oxygen
**respiration: glucose + oxygen ->> carbon dioxide + water + energy
Process:
1) Light dependent reactions – water is turned to oxygen (2:1 molecules)
- Tested through using isotopes of O2 for water and carbon dioxide; oxygen
contained isotope of oxygen that was used for water
2) Light independent reactions – carbon dioxide and water is turned to glucose
Chlorophyll: the pigment that makes plants look green
- Can absorb solar energy, combine carbon dioxide with water to make glucose
- Requires magnesium ions
- Converts light energy to chemical energy
Uses of glucose
For energy:
- For active transport (moving mineral ions to root hairs)
- Building proteins by amino acids
- (energy is released from glucose by respiration)
Stored as starch:
- Lots of glucose molecules are linked to form starch
- They are stored in the leaf; starch molecules are insoluble in water
o They are not involved in the chemical equations taking place inside the cells
o Do not affect the concentration of the solutions, so water does not enter/leave
by osmosis
- Can quickly and easily be broken down to glucose molecules when needed
Changed to sucrose for transport:
- Glucose is changed to sucrose (larger molecules) and it is carried to other parts
through phloem tubes
o Only leaves make glucose but all parts require it
- Once it reaches its destination, it changed back to glucose and is used in respiration
To make cellulose to build cell walls:
- Hard to be broken down to glucose
o Function of the cell wall is to support the cell
Used to make nectar to attract pollinators:
- Plants need insects, birds and bats to help them sexually reproduce
Used to make proteins and other substances:
- For example, chlorophyll (requires magnesium and nitrate ions *through active
transport, which needs energy*)
Parts of the leaf
Epidermis:
- Do not contain chloroplasts
- Secrete (make and release) a waxy substance, the
cuticle
- Upper and lower
Palisade mesophyll:
- Lots of chloroplasts
- Tall and narrow
- Main function is photosynthesis
Spongy mesophyll:
- Contains less chloroplasts
- Not as tight packed; contains air spaces
o Allows carbon dioxide and oxygen to
diffuse between the air and the cells
o Allows vapor to move from the surface
of the cells to outside the leaf
Stomata:
- On the lower epidermis
- Surrounded by a pair of guard cells
o Contain chloroplasts
o Can change their shape
- Allows the diffusion of carbon dioxide, oxygen and water vapor in and out of the leaf
Vascular bundles:
- Contains xylem and phloem
- Xylem vessels
o Large and thick-walled
o Carries water and minerals TO leaves
- Phloem vessels:
o Smaller and thin-walled
o Carried sucrose and other substances AWAY from leaves
How are plants adapted to increase the efficiency of photosynthesis?
Leaves:
- Large surface area (broad, flat surface)
o Increases the amount of sunlight it contacts
o Increases the diffusion of carbon dioxide
- Thin
o Allows sunlight to pass through
o Reduces diffusion distance of carbon dioxide
- Arranged in patterns so they do not cut off light from one another
Epidermis cells:
- Are transparent so light can easily pass
Cuticle:
- Waterproof to prevent water loss
Chloroplasts:
- Can move around the palisade cell to get the best quality of sunlight
Chlorophyll:
- Is arranged on a flat membrane to allow sunlight to reach
Stomata:
- Can change shape to control substances in leaf
How to test whether photosynthesis happens: test for starch on the leaf
1) Break cell membrane - starch cannot pass partially permeable membrane - by boiling
in water
2) Drop in alcohol - remove chlorophyll so color change is more noticeable
3) Dip in hot water again – soften leaf
4) Put on white tile and cover with iodine solution
If it turns dark blue, there is starch
How to test whether chlorophyll is needed for photosynthesis:
1) Use a leaf that contains part with and without chlorophyll
2) Test for starch
How to test if light is needed:
1) Destarch plant by leaving it in a cupboard for a few days – test one of its leaves for
starch
2) Fold black paper over part of the leaf and put plant in sun for a few days
3) Test for starch
How to test if carbon dioxide is needed:
1) Put two bags around two leaves on a plant; one with distilled water, one with
potassium hydroxide solution
o Make sure seals are airtight
o Water bag gets carbon dioxide by respiration
o Potassium hydroxide solution absorbs the carbon dioxide
o Water is there to control the humidity (other variables must stay the same)
2) After a few days, test for starch
How to explain curves:
1) Describe which curve is above
2) Describe why that curve is above
3) Explain that that reason is why the photosynthesis has changed as it did
Optimum temperature:
1) As the temperature increases, the rate of photosynthesis increases up to __ degrees //
after that it decreases
2) After it reaches the maximum and starts decreasing the rate is steeper
3) Quote of a change between two values (“between x time and x time, the temperature
increased from y degrees to y degrees”)
How do plants make carbohydrates?
1) Carbon dioxide and water react to produce glucose and oxygen
2) They do this by using energy from sunlight (that is absorbed from chlorophyll)
Why did the curve go down?
1) Enzyme molecules denature and the active sites lose their shape
2) No products are from
3) They can no longer form enzyme-substrate complexes
Function of chlorophyll:
1) Absorb energy from sunlight
2) Transfers energy from light to energy from carbohydrates