Chapter 5: Photosynthesis
Learning Objectives:
• Examine the characteristics of sunlight.
• Examine how the wavelength of light affects photosynthesis.
• Examine the role of pigments in photosynthesis.
• Describe the process of photosynthesis using a flowchart.
• Outline the importance of light-dependent reactions in the process of
photosynthesis.
• Outline the pathways involved in energy transportation in photosynthetic
organisms.
• Examine the different methods used by photosynthetic organisms to fix carbon
(C3, C4, and CAM).
5.1 Life Depends on Photosynthesis
Living things are classified as autotrophs or heterotrophs based on how they
get their organic molecules
● Autotrophs produce their own organic compounds from inorganic
starting materials such as CO2 and water. Some obtain energy from
light and others obtain energy through chemical reactions.
● Heterotrophs rely on organic molecules produced by other organisms.
Most autotrophs use photosynthesis: the process of converting solar energy
to chemical energy.
Photosynthetic organisms belong to Domain Bacteria and Eukarya.
● Photosynthetic bacteria conduct photosynthetic reactions in the
cytoplasm. They have photosynthetic pigments, but not chloroplasts.
● Plants and algae are photosynthetic eukaryotes. They conduct
photosynthesis in chloroplasts.
● Domain Archaea doesn’t have any photosynthetic organisms. Some
use light for energy, but not to build carbohydrates.
BIOL 101 Chapter 5 Study Guide Page 1 of 8
, A. Photosynthesis Builds Carbohydrates Out of Carbon Dioxide and Water
During photosynthesis, pigment molecules capture energy from the sun.
● In plants and algae, these pigments are in the chloroplasts.
The overall reaction for photosynthesis is
Carbon dioxide + water glucose + oxygen
Pigments use redox reactions to capture the energy needed for making
glucose.
Photosynthesis provides food for the plant, and energy, molecules, and
oxygen to support most heterotrophs.
B. Plants Use Carbohydrates in Many Ways
● Glucose can be used to quickly make ATP by cellular respiration
(covered in the next chapter.
● Sugar increases the plant’s chance of reproducing. Nectar increases
the spread of pollen by insects and other animals. Fruit attracts
animals, leading to increased distribution of seeds.
● Glucose is used for producing other molecules used by the plant:
cellulose in cell walls, and starch for energy storage.
C. The Evolution of Photosynthesis Changed Planet Earth
● Before the evolution of photosynthesis, Earth’s atmosphere contained
little oxygen.
● Ancient cyanobacteria added oxygen to the atmosphere and levels
increased over time. Increased oxygen levels allowed other organisms
to produce ATP more efficiently (more in the next chapter).
5.2 Sunlight is the Energy Source for Photosynthesis
A. What is Light?
Light moves in waves of tiny particles called photons. The shorter the
wavelength, the more energy.
BIOL 101 Chapter 5 Study Guide Page 2 of 8
Learning Objectives:
• Examine the characteristics of sunlight.
• Examine how the wavelength of light affects photosynthesis.
• Examine the role of pigments in photosynthesis.
• Describe the process of photosynthesis using a flowchart.
• Outline the importance of light-dependent reactions in the process of
photosynthesis.
• Outline the pathways involved in energy transportation in photosynthetic
organisms.
• Examine the different methods used by photosynthetic organisms to fix carbon
(C3, C4, and CAM).
5.1 Life Depends on Photosynthesis
Living things are classified as autotrophs or heterotrophs based on how they
get their organic molecules
● Autotrophs produce their own organic compounds from inorganic
starting materials such as CO2 and water. Some obtain energy from
light and others obtain energy through chemical reactions.
● Heterotrophs rely on organic molecules produced by other organisms.
Most autotrophs use photosynthesis: the process of converting solar energy
to chemical energy.
Photosynthetic organisms belong to Domain Bacteria and Eukarya.
● Photosynthetic bacteria conduct photosynthetic reactions in the
cytoplasm. They have photosynthetic pigments, but not chloroplasts.
● Plants and algae are photosynthetic eukaryotes. They conduct
photosynthesis in chloroplasts.
● Domain Archaea doesn’t have any photosynthetic organisms. Some
use light for energy, but not to build carbohydrates.
BIOL 101 Chapter 5 Study Guide Page 1 of 8
, A. Photosynthesis Builds Carbohydrates Out of Carbon Dioxide and Water
During photosynthesis, pigment molecules capture energy from the sun.
● In plants and algae, these pigments are in the chloroplasts.
The overall reaction for photosynthesis is
Carbon dioxide + water glucose + oxygen
Pigments use redox reactions to capture the energy needed for making
glucose.
Photosynthesis provides food for the plant, and energy, molecules, and
oxygen to support most heterotrophs.
B. Plants Use Carbohydrates in Many Ways
● Glucose can be used to quickly make ATP by cellular respiration
(covered in the next chapter.
● Sugar increases the plant’s chance of reproducing. Nectar increases
the spread of pollen by insects and other animals. Fruit attracts
animals, leading to increased distribution of seeds.
● Glucose is used for producing other molecules used by the plant:
cellulose in cell walls, and starch for energy storage.
C. The Evolution of Photosynthesis Changed Planet Earth
● Before the evolution of photosynthesis, Earth’s atmosphere contained
little oxygen.
● Ancient cyanobacteria added oxygen to the atmosphere and levels
increased over time. Increased oxygen levels allowed other organisms
to produce ATP more efficiently (more in the next chapter).
5.2 Sunlight is the Energy Source for Photosynthesis
A. What is Light?
Light moves in waves of tiny particles called photons. The shorter the
wavelength, the more energy.
BIOL 101 Chapter 5 Study Guide Page 2 of 8
