Cellular Energetics
Essential Question: How is matter transferred or
energy transferred in living systems?
Energy
Without the ability to use and get energy cells
would die
They use energy to make molecules (building
blocks for biological molecules) and get rid of
waste
Cells carry out all the jobs in your body:
circulation oxygen, breaking down food,
contracting muscles, etc.
All of these jobs require energy.
ATP
• Living things use chemical energy
• ATP (Adenosine Triphosphate) – one of the
most important chemicals the cell uses to
store and give off energy
– It is made up of adenine, a sugar called ribose and
three phosphate groups
– The phosphate groups are the key to how ATP
stores and releases energy
ADP
Adenosine diphosphate is similar to ATP
ADP only has two phosphate groups instead of
3
This is how living things store energy
When a cell has extra energy it stores it by
adding a phosphate group to ADP turning it
into ATP
Releasing Energy
Cells can give off energy that is stored in ATP
by breaking the chemical bond between the
second and third phosphate groups
Using Chemical Energy
ATP is used to power active transport
Helps to move protein in muscle helping them
to flex
Makes proteins, carbohydrates, lipids
Responds to chemical signals
If cells move they use this energy
Short-Term Storage
ATP is good for giving off a small amount of
energy very quickly
It is not good at storing large amounts for a
long time
For that we have the sugar glucose
ATP comes from food
• Once cells use up their ATP they must make
more of it somehow
• Cells use the energy from the food we eat to
make more ATP
• Different living things get their food from
different sources
Heterotrophs
Living things that get food by eating other
organisms
Some eat plants
Some eat other animals
Some break down the tissues of dead things
Autotrophs
Make their own food
Plants, algae and some bacteria use light
energy from the sun to make their own food
The energy in nearly all food molecules came
from the sun
All life on earth depends on autotrophs
making their own food using energy from the
sun
This process is called photosynthesis
Light From The Sun
• The sun gives off energy called visible light
• Visible light appears white but actually
contains every color
Plant Pigments
• Autotrophs – organisms that make their own
food using the sun’s energy
– They have specific pigments
– Pigments – absorb certain wavelengths of light
and reflect others – absorb certain colors, reflect
others.
• The color that is reflected is the color you see, all other
colors are absorbed.
• Pigments determine what is absorbed and what is
reflected
• Autotrophs need pigments to trap energy from the sun
to carry out photosynthesis
Chlorophyll
The most common and important
photosynthetic pigment
It absorbs violet, blue and red light which
provide energy for photosynthesis
It reflects green light which is why most plants
look green
Found in the cholorplasts of plant cells
This is where photosynthesis takes place
Other Plant Pigments