Cell Energy: Photosynthesis and Respiration

Cell Energy:
Photosynthesis and Respiration
Section 6-1

Photosynthesis:
Capturing and Converting Energy
Energy is the ability to do work
Potential vs. Kinetic
Point of Reference
How do living things capture, convert, store and use energy?
Main source of energy for ALL living things is the SUN!
Photosynthesis
The process where plants convert the electrical energy of
sunlight into chemical energy.
This energy is stored in the chemical bonds of carbohydrates:
Sugars and starches

Timeline of Discoveries
1600’s - Jan Van Helmont measured the mass of soil and a
tree; he then grew the tree for five years and measured
the masses again.
The soil stayed the same while the tree increased about 75 Kg.
He concluded that most of the mass increase came from the
water that he added.
1700’s - Joseph Priestly discovered that oxygen is
produced by plants.
Jan Ingenhousz - showed that oxygen is only produced
when the plant is exposed to sunlight.

Requirements for Photosynthesis
Chemical equation for photosynthesis:
Reactants ——› Products
Carbon Dioxide + Water ——› Glucose + Oxygen
Unbalanced
CO 2 + H 2 O ——› C 6 H 12 O 6 + O 2
Light
Balanced ??
__CO 2 + __ H 2 O ——› C 6 H 12 O 6 + __ O 2
Light

Sunlight
Nearly all organisms on Earth depend on the Sun for
energy.
Those that directly use the Sun’s energy are called:
Autotrophs; producers
Those organisms that can not use the Sun’s
energy directly must get their energy from
producers. They are called:
Heterotrophs : consumers

Visible light spectrum

Pigments
Chlorophyll absorbs red and blue light

Energy Storing Compounds
Two ways this energy is trapped in plants.
1. As Sunlight strikes a leaf, the energy in the light excites
a pair of electrons. These electrons are passed directly
to an electron carrier [NADP+], which is then
converted into [NADPH]. This process converts
electrical energy into chemical energy.

Second Way
2. Store the chemical energy in the bonds of ATP.
Adenosine Triphosphate
Made of Adenine, ribose [5 carbon sugar] and three phosphate groups

Storing Energy
A molecule of AMP [Adenosine Monophosphate] attaches a
second phosphate group the bond stores energy and the
molecule becomes ADP [Adenosine Diphosphate].
What happens when a third phosphate group is attached?
ATP [Adenosine Triphosphate]
One muscle cell can consume and regenerate over 10,000,000
ATP's a second.
If ATP couldn't be regenerated, humans would have to consume
nearly their body weight in ATP each day.