Chapter 4
Cell Processes and Energy
4.1 Photosynthesis
photosynthesis
• The process by which a cell
captures energy in sunlight
and uses it to make food.
autotroph
•An organism that
makes its own food.
heterotroph
• An organism that cannot make its
own food.
–Many heterotrophs obtain food by
eating other organisms. (lion, zebra,
human)
–Some absorb their food from other
organisms. (fungi)
pigment
• A color chemical
compound that absorbs
light and can be used to
color other materials.
chlorophyll
• The main photosynthetic
pigment found in the
chloroplasts of plants, algae,
and some bacteria.
stomata
• Small openings on a leaf
through which oxygen and
carbon dioxide can move.
Series (SIHR eez)
• Noun
• A number of things or events of the
same class coming one after another
in a spatial or temporal succession.
• Ingesting food is the first step in a
long series of mechanical and
chemical steps.
Photosynthesis
• Like baking cupcakes:
– Mix ingredients together
– Bake in oven
– Yields 12 cupcakes
• “Recipe” for photosynthesis:
– Combine carbon dioxide and water
– Use energy from sunlight
– Yields a sugar molecule and 6 oxygen molecules
Photosynthesis and Food Chains
• How do autotrophs get their food?
– They make their own food using sunlight and
photosynthesis.
• How does the sun supply heterotrophs with
energy?
– Heterotrophs get energy by eating plants or other
animals that eat plants. The plants get their
energy from sunlight, so heterotrophs get their
energy from sunlight indirectly.
What Happens During Photosynthesis?
• What are the two stages of
photosynthesis?
– Capturing the sun’s energy and producing
sugars
• What is the energy captured in the first
stage used for?
– To produce sugars in the second stage
What Happens During Photosynthesis?
• What pigment in chloroplasts
absorbs light?
–Chlorophyll
• How is chlorophyll like a solar cell?
–Both chlorophyll and solar cells absorb
light energy and use it to power a
process.
What Happens During Photosynthesis?
• What happens in the second stage?
– Water and carbon dioxide combine chemically to
form sugars, and oxygen is released.
• How are roots and stomata important for
photosynthesis?
– Roots take up water, and stomata take in carbon
dioxide, both of which are needed for
photosynthesis.
The Photosynthesis Equation
6 Carbon Dioxide molecules combine with 6 water molecules due to a chemical reaction
from light energy and produce one sugar molecule and 6 oxygen molecules!
6 CO2 + 6 H2O
C6H12O6 and 6 O2
Section 2
•Respiration
respiration
• The process by which cells obtain energy from
glucose.
• During respiration, cells break down simple
food molecules such as sugar and release the
energy they contain.
fermentation
• The process by which cells
break down molecule to
release energy without using
oxygen.
Constant (KAHN stunt)
• Noun
• Something invariable or unchanging.
• When birth and death rates are equal, a
closed population will remain at a constant.
Background Knowledge
• What does a fire need to burn?
–Fuel and oxygen
• What is released when fuel is
burned?
–Energy in the form of heat and
light
Respiration
• A similar chemical process, called
respiration, “burns” food molecules in
cells.
• Like combustion, respiration uses fuel
and oxygen to produce energy.
• The fuel comes from food, and the
energy is used for cellular functions.
What is Respiration?
• The process by which cells obtain energy from
glucose.
• During respiration, cells break down simple
food molecules such as sugar and release the
energy they contain.
• All cells respire.
Storing and Releasing Energy
• Like money in a bank
– Store it until you want to use it
• Store energy
– Plants: photosynthesis captures light energy and
then stores it as sugar and carbohydrates.
– Animals: eat a meal – add to your energy savings
account.
• Withdraw energy when needed
Breathing and Respiration
• Respiration has two meanings.
– 1. breathing – moving air into and out of lungs
– 2. the process that takes place inside cells –
sometimes called cellular respiration
• Connection
– Breathing brings oxygen, which is usually
necessary for cellular respiration, into your lungs.
The Two Stages of Respiration
• Stage 1
– Takes place in the cytoplasm
– Glucose molecules broken into smaller molecules
– Small amount of energy released
• Stage 2
– Takes place in the mitochondria
– The small molecules are broken down even
smaller
– Large amount of energy released
The Two Stages of Respiration
• Two products of respiration
– Carbon Dioxide
– Water
The Respiration Equation
• C6H12O6 + 6 O2
6 CO2 + 6 H2O + energy
• Raw materials for Respiration:
– Sugar
– Oxygen
Comparing Photosynthesis and
Respiration
• Equations are opposite.
• Opposite processes
• These two processes form a cycle that keeps
the levels of oxygen and carbon dioxide fairly
constant in Earth’s atmosphere.
Two
methods of
producing
and using
energy.
These
methods
work
together to
keep the
atmosphere
constant.
Events During Respiration
• Reminder:
– The food you eat must be broken down to release
energy it contains.
• What is the process called that releases
energy from food?
– Respiration
• Why is respiration important to cells?
– It provides cells with the energy they need to
carry out their functions.
Events During Respiration
• What happens in the first stage of respiration?
– Glucose is broken down into smaller molecules
and a small amount of energy is released.
• What happens in the second stage of
respiration?
– The smaller molecules are broken down into even
smaller molecules and a large amount of energy is
released.
Apply It!
• Why do you think muscle cells have many
mitochondria?
– The second stage of respiration, which produces
lots of energy, takes place in the mitochondria.
– The large numbers of mitochondria in muscle cells
supply a great amount of energy for movement.
Fermentation
• Some cells are able o obtain energy from food
without using oxygen.
– Some single-celled organisms that live deep in the
ocean or in the mud of lakes or swamps.
• Through fermentation, an energy-releasing
process that does not require oxygen.
Alcoholic Fermentation
• Occurs when yeast (and some single-celled
organisms) break down sugars.
• Products of this process:
– Alcohol
– Carbon dioxide
– Small amounts of energy
• Important to Bakers and Brewers
– Bread rises and has air pockets
– Creates bubbles in in alcoholic drinks
Lactic Acid Fermentation
• Occurs when muscle use up oxygen faster
than it can be replaced
• Fermentation occurs without oxygen to supply
energy.
• Lactic Acid is a product of this type of
fermentation
• You would have sore and tired muscles.
Obtaining Energy Without Oxygen
• What is the process in which energy is
released without using oxygen?
– Fermentation
• What are the products of alcoholic
fermentation?
– Alcohol, carbon dioxide, and energy
Obtaining Energy Without Oxygen
• What is a product of lactic-acid fermentation?
– Lactic Acid
• When might your body release energy using
fermentation?
– If you are exercising so hard or long that your
muscle cells cannot take up oxygen faster than it is
being used.
Section 3