ENKA HIGH SCHOOL
GRADE 10 BIOLOGY
CLASSWORK
Chemosynthesis and Energy – Worksheet KEY
Part 1: Defining Autotrophs and Chemosynthesis
1. Define the two main groups of autotrophic organisms based on their energy source for
synthesizing organic matter from inorganic substances1.
o Group 1: Photosynthetic autotrophs
 Energy Source: Light (or sunlight )
o Group 2: Chemosynthetic autotrophs
 Energy Source Method: Oxidize inorganic substances and synthesize organic
matter using the resulting energy.
2. Define chemosynthesis8.
o Chemosynthesis is the synthesis of organic matter from inorganic substances H2O and
CO2 by some prokaryotes using the chemical energy released by the oxidation of
inorganic substances.
3. Identify the process that removes electrons from an atom or molecule.
o Answer: Oxidation
Part 2: Chemosynthesis Process and Environment
4. List three examples of inorganic substances that are oxidized in chemosynthesis to produce
energy12:
o a) Hydrogen sulfide (H2S)
o b) Ammonia NH3
o c) Iron (Fe) (Other valid answers include: Hydrogen gas, Nitrite, and Sulfur)
5. State the role of ATP in both photosynthesis and chemosynthesis.
o The energy released during oxidation reactions is used to synthesize ATP.
o This molecule plays a role in the production of organic molecules by combining CO2
and hydrogen obtained from various sources.
6. Identify two extreme environments where these energy-producing prokaryotes are commonly
found.
o a) The deep sea (or deep-sea vents)
o b) The oxygen-free mudflats of ocean and swamp bottoms (Other valid answers
include: Landfills, sewage sludge processing tanks, and the digestive systems of some
mammals).
Part 3: Commonalities (Similarities)
7. List three similarities between photosynthesis and chemosynthesis:
o a) Both processes are used by organisms to produce food (organic compounds) from
inorganic substances.
o b) Both use carbon dioxide (CO2) as a carbon source.
o c) Both involve electron transfer chains to generate energy.
(Other valid answers include: Both synthesize ATP by oxidative phosphorylation; Both
are enzymatic reactions; Oxygen is produced in both; Both are the base of a food
chain)
Part 4: Key Differences
8. Complete the table by providing the key difference for each category:
Category
Photosynthesis
Chemosynthesis
Energy
Source
Sunlight
Chemical energy from inorganic
compounds
Pigment
Use
Uses chlorophyll to capture light
Does not use chlorophyll or light
Timing
Occurs during the day
Occurs during the day and night
Organism
Type
Occurs in prokaryotes and eukaryotes
(mostly in plants, algae, and cyanobacteria)
Occurs in only prokaryotes (in
bacteria and archaebacteria)