Download Cell Notes Part 4

Cell Notes
Part 4
How do cells use energy?
o
o
All of the activities of an organism involve
chemical reactions in some way. The total
of all chemical reactions is called
metabolism.
Cells need enzymes for these chemical
reactions to occur. Enzymes are special
proteins that regulate how fast chemical
reactions occur.
How do cells use energy?
o
Living things are divided into two
groups, Producers and Consumers, based
on how they obtain food.
1. Producers make their own food.
2. Consumers need to obtain food
from an outside source.
o
The three processes that cells use to
release stored energy are
photosynthesis, respiration, and
fermentation.
Photosynthesis
1.
During photosynthesis, producers such as
plants use light energy from the sun to make
sugars, which can be uses as food.
- photosynthesis begins in plant cells with
chlorophyll located inside chloroplasts. The
sun’s energy is stored in these pigments and
used to power the chemical reactions.
- The cells then use water(H2O) and carbon
dioxide(CO2) and the stored energy from the
sun to make sugars that the cells use for
energy to carry out cell function.
Photosynthesis cont’d
- the water in soil enters the plants
through the roots and moves up the
stem to the leaves and inside the
chloroplasts where the stored energy
from the sun fuels the following
chemical reaction:
6CO2 + 6H2O + light energy  C6H12O6 + 6O2
Carbon dioxide + Water + sunlight (chlorophyll) Sugar (glucose) + oxygen
Photosynthesis cont’d
Reactants
Products
6CO2 + 6H2O + light energy  C6H12O6 + 6O2
Carbon dioxide + Water + sunlight (chlorophyll) Sugar (glucose) +
oxygen
- The materials on the left side of the equation, which you start with are
called reactants.
- The materials at the end of the equation are called the products. The oxygen
is a waste product emitted into the air and the glucose is used by the plant to
carry out its functions.
Respiration
2. During respiration, cells break down simple
food molecules such as glucose(C6H12O6)
and release the energy they contain. It is
the process by which cells “withdraw”
energy from glucose. We call it cellular
respiration so it is not confused with
breathing respiration.
Respiration cont’d
o
In the first stage of respiration, which takes
place in the cytoplasm, the glucose molecules
are broken down into smaller molecules where
only a small amount of energy is released.
o
In the second stage of respiration, the
mitochondria use oxygen to break down the
glucose molecules into even smaller molecules
to release even more energy. When this occurs,
water and carbon dioxide are released as waste
products of the reaction.
Respiration cont’d
o
o
The carbon dioxide and water diffuse
out of the cell and are released into the
air when animals breathe out.
The following equation represents this
chemical reaction inside the cell:
Reactants
Products
C6H12O6 + 6O2  6CO2 + 6H2O + energy
Sugar (glucose) + oxygen  Carbon dioxide + Water + energy
Plants make their own glucose while animals get it from food. Oxygen
comes from the air.
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Fermentation
3. During fermentation cells are able to
obtain energy from food without using
oxygen. The amount of energy released
during fermentation, however is much lower
than respiration.
- Fermentation begins in the cytoplasm
where glucose molecules are broken down
into smaller molecules.
- Unlike respiration, the molecules do not
move into the mitochondria. Instead more
chemical reactions keep occurring in the
cytoplasm.
Fermentation cont’d
- Depending on the type of cell, the waste products
may be lactic acid or alcohol and carbon dioxide.
* When your muscle cells use fermentation,
lactic acid is a waste product that builds up and
makes muscles sore.
* Some bacteria that use fermentation to
release energy release lactic acid are used to make
things like yogurt and cheese. The acid gives the
food some of its flavor.
* When yeast cells use fermentation they
produce alcohol and carbon dioxide as a waste
product. This is used to make bread rise. This type
of fermentation is also how ancient peoples learned
to make the first alcoholic beverages.
Fermentation cont’d
- The following equation represents
fermentation:
Reactants
Products
C6H12O6  2C2H5OH + 2CO2 + Energy
Glucose  Ethanol + Carbon dioxide +
energy