1. Textbook Chapter 8 Review Book Topic 2
Photosynthesis
Textbook Chapter 8
Review Book Topic 2

2. Transformation of Energy
Energy – the ability to do work
All organisms need energy to live and to carry out all chemical processes within (metabolism)
Recall:
Autotrophs can make their own food (energy)
Heterotrophs need to eat food to obtain energy

3. Metabolism Photosynthesis Cellular Respiration
Light energy from the sun is converted to chemical energy for use by the cell
Cellular Respiration
Organic molecules are broken down to release energy for use by the cell

4. History
1770s
In sealed container, a candle can only burn for a short amount of time
Within this container
Animals could not survive
Candle could not be relit
Plants could survive and allow a candle to burn in their presence

5. 1770s continued…
First evidence that plants interact with the air by using the CO2 produced from the burning candle to replace the O2 which is being used by the candle and animals

6. 1880s
Basic needs for plant growth:
Carbon dioxide
Water
Light
Did you know that most energy enters the Earth’s biosphere through photosynthesis?
Over 150 billion tons of sugar is produced by plants yearly!

7. Photosynthesis
The process of capturing and transforming the sun’s energy into chemical energy in the form of glucose
Carried out by green plants (producers)
Uses CO2, H2O and light energy to make glucose and O2
Most of the O2 in the atmosphere is the result of photosynthesis

9. Remember plants are autotrophs, which means they make their own food from simple inorganic compounds
Two major types:
Photoautotrophs
Use light energy to make food (ex. Green plants, algae)
Chemoautotrophs
Uses inorganic chemicals for their food-making reactions to produce energy (Ex. mostly bacteria)

10. Light Energy Sunlight is a form of energy known as radiation
Travels in waves
Wavelength is the
distance between
the crest of two
different
wavelengths
Sunlight is a mixture of all visible wavelengths

11. Sunlight is called “white light”
Colors:
White
All wavelengths of light are reflected equally by an object
Black
All wavelengths of light are being absorbed equally by an object
The color you see is the wavelength which is being reflected by an object
Ex. Red – all wavelengths are being absorbed but red is being reflected by the object
Sunlight is called “white light”

12. Spectrum – white light passes through a prism and each wavelength is bent in different amounts
Causes the light to spread out showing the order of their wavelengths
Shortest – violet
Longest – red
The shorter the wavelength of light, the more energy available

13. Pigment – substance that absorbs light
Different wavelengths of light are absorbed by particular pigments

14. Photosynthetic Pigments
Chlorophyll
Most abundant and important photosynthetic pigment
In plants there are two types:
Chlorophyll a
Chlorophyll b
Absorb red and blue light
Reflect green light (this is why plants are green!)

15. Other pigments
absorb light in
regions not
associated with
chlorophyll a,
increasing the
range of the
spectrum
Carotenes (orange)
Xanthophylls (yellow)

17. The presence of chlorophyll a hides the carotenes and xanthophylls in leaves
Are not seen until autumn when chlorophyll starts to break down and leaves begin to turn color

18. Chloroplasts
In green plants, photosynthesis occurs within chloroplasts
Contain:
Photosynthetic membranes arranged in flattened sacs called thylakoids
Stacks of thylakoids are called grana
Regions between the grana are known as stroma

20. In order for photosynthesis to occur it requires photosynthetic pigments AND the proteins in the thylakoid membrane

21. Main Ideas
Some organisms produce their own food, whereas others obtain energy from the food they ingest
Cells store and release energy through two reactions: photosynthesis and cellular respiration
Energy is used to drive all cellular activities (metabolism)
Plants contain chloroplasts with light-absorbing pigments that convert light energy into chemical energy

22. Leaf Structure
Leaves are specialized to capture light for photosynthesis
Wide
Flat
Large surface area for absorption
Arrangement around stem maximizes exposure to light
Environment determines leaf structure

23. Simple
Compound

24. Internal Structure Outermost layer is a clear waxy cuticle Epidermis
Protects inner tissues
Slows down water loss from leaf
Epidermis
Below cuticle
One cell thick
Little or no pigment to allow light to reach photosynthetic pigment in inner leaf tissues

26. Inner Structure Continued
Epidermis continued…
Contains stomates
Small openings on the underside of the leaf
Allow the exchange of carbon dioxide, oxygen and water vapor between the leaf and the environment

27. A pair of guard cells surround each stomate
Epidermis continued…
A pair of guard cells surround each stomate
Regulate the opening and closing of stomates (caused by osmosis)
Closed when little water available, low temperatures or little light available

29. Internal Structure Continued…
Mesophyll is located between the upper and lower layers of the epidermis
Photosynthesis occurs here in a leaf

30. Mesophyll continued… Two layers Palisade mesophyll
One to two cells thick
Tall, tightly packed
Filled with chloroplasts
Spongy mesophyll
Irregular shaped cells
Large air spaces in between cells (stomates located near this layer to allow for gas exchange)
Fewer chloroplasts

32. External Structure
Each leaf contains a network of veins:
Xylem: transports water and minerals
from the roots upward to the stem
Phloem: transports
food and dissolved
materials in both
directions along the
length of the plant

33. External Structure Continued…
Veins are located throughout the mesophyll layer
Vein patterns are a characteristic of a species

34. Chemistry of Photosynthesis

35. Chemical Reactions
Summary of converting light energy to chemical energy:
(light)
6 CO H2O  C6H12O6 + 6 O2 + 6 H2O
Occurs in chloroplasts in the presence of light, carbon dioxide and water
Produces sugar, oxygen and water

36. Both reactions depend on each other
Occurs in two phases:
Light dependent reactions
Light independent reactions
Both reactions depend on each other
Light dependent reactions produce ATP that the light-independent reactions use to make glucose

37. ATP: The Unit of Cellular Energy
Energy exists in many forms:
Light energy
Mechanical energy
Thermal (heat) energy
Chemical energy
ATP = Adenosine triphosphate
Most abundant biological energy-carrying molecule in all organisms

38. ATP Structure Contains: Adenine base Ribose sugar
Three phosphate groups

39. ATP  ADP + P (releases energy)
ATP Function
Releases energy when the bond between the 2nd and 3rd phosphate is broken, releasing a phosphate
ATP  ADP + P (releases energy)
ADP = adenosine diphosphate
ADP + P  ATP (stores energy)

40. SEE GUIDED NOTE SHEET AND REACTION DIAGRAMS FOR LIGHT-DEPENDENT AND LIGHT-INDEPENDENT REACTIONS

41. Factors Affecting Photosynthesis
Light Intensity
↑ intensity, ↑ rate of photosynthesis
Temperature
Specific optimum temperature depending on plant
At extremes enzymes are damaged, ↓ rate of photosynthesis

42. Slows photosynthesis if in low supply
Water availability
Slows photosynthesis if in low supply
If severe shortage, photosynthesis stops
Mineral availability
If in short supply affects the rate of photosynthesis