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Source: Ck-12 Photosynthesis and Cellular Respiration, Section: 1.1 Energy of Life, pg. 2-7.
Objectives:
 State why living things need energy.
 Describe how autotrophs and heterotrophs obtain (get) energy.
 Compare and contrast glucose and ATP.
 Outline how living things make and use food.
Why living
things need
energy:
How organisms
get energy:
Autotrophs:
Heterotrophs:
Energy molecules: Glucose
and ATP:
Energy of Life
Every life process, such as breaking down and building up molecules and
transporting molecules across plasma membranes requires energy.
Because this is a major part of life function, all living things need energy to
survive. Without energy, none of the things that have to take place in order
to keep living things going could happen.
The energy used to carry out all life processes is chemical energy, which
comes from food. There are two primary ways organisms get food.
Autotrophs are organisms that use photosynthesis to make their own food.
Through photosynthesis, sunlight, CO2 , and water are converted into
glucose (sugar), which is stored chemical energy for plants to use as
energy. Plants are called producers because the “produce” or make their
own food.
Heterotrophs are living things that cannot make their own food and must
get energy from consuming other living things. These type of organisms
are called consumers because they must consume (or eat) other things to
get energy.
There are mainly two types of chemical energy that organisms use: glucose
and ATP. Both act as fuel and are both a major part of photosynthesis.
Glucose (C6H12O6) is a simple carbohydrate and store concentrated
chemical energy in a stable form. In humans, it is carried in your blood and
distributed throughout the cells in the body. In plants it is the end product
of photosynthesis.
ATP (adenosine triphosphate) is what cells use for energy. ATP is made
during the first half of photosynthesis and then use up during the second
half to make glucose.
Both are needed because glucose helps in the transfer or packaging of
molecules, while ATP is helps with providing the energy for the life processes.
Making and
Photosynthesis begins the flow of energy through all living things, because
using food:
is stores energy from the sun by creating chemical bonds in glucose.
Cellular respiration is the process where glucose is broken down to make
ATP. The products of photosynthesis are the reactants of respiration and
visa versa.
Draw Figure 1.3 Below:
Photosynthesis:
Cellular
Respiration:
SUMMARY:
Photosynthesis is the process where plants use sunlight (light energy) and
converts it into stored chemical energy and oxygen (O2). The chemical
equation is: 6CO2 + 6H2O + Light Energy  C6H12O6 + 6O2
Producers (autotrophs) convert light energy from the sun, CO2, and water
(the reactants) and produce oxygen and glucose.
Cellular respiration is where glucose is used as slowly released energy in
the process of making ATP. The chemical equation for cellular respiration
is: C6H12O6 + 6O2  6CO2 + 6H2O + Chemical Energy (in ATP). This process
happens in the cells of all organisms. They all use glucose to form ATP.
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