Cellular Energy and Photosynthesis

Living Things use Energy

Energy is the ability to do work

Cells use chemical energy to do work.

– Cell growth

– Reproduction

– Active transport

– Movement

– Chemical reactions

Sun is our energy source.

• Energy enters most ecosystems as

sunlight and leaves as heat.

• Photosynthesis: a chemical reaction that

converts solar energy into the chemical

energy stored in the bonds of organic

molecules (food)

• One important product of photosynthesis is

glucose

ATP and Energy

Cellular Respiration is the chemical

reaction that breaks down glucose and

uses the energy to make ATP.

– Glucose is made during Photosynthesis.

ATP is the basic energy source used by all

types of cells.

ATP

ATP = adenosine triphosphate.

This is the compound that directlysupplies the energy to do cellular work.

How ATP Works

The release of one of the phosphate groups makes energy available to do cellular work.

ATP energizes other molecules by transferring one phosphate group.

Autotrophs & Heterotrophs

Autotrophs: organisms able to use light energy from the sun to make their own food.

Examples: plants, algae, and some bacteria.

Heterotrophs: organisms that obtain food by consuming other living things.

Examples: fungi, animals

Both autotrophs & heterotrophs must convert the energy that is stored in the bonds of their food into ATP.

What is Photosynthesis?

The process of photosynthesis is a chemical

reaction

It is the most important chemical reaction on our

planet!!

Life on Earth is made possible by the SUN and

PHOTOSYNTHESIS

What organisms can do photosynthesis?

Light and Pigment

Light is the form of energy that comes from the

sun

Pigment: light absorbing molecules which allow

plants to gather light energy from the sun

absorbs some wavelengths of light but reflects others

to produce color

Pigment: Chlorophyll

Two types: Chlorophyll a and chlorophyll b

Plants are green because the green wavelength is

reflected, not absorbed.

Chlorophyll Absorption Spectrum

Chlorophyll absorbs blue-violet

& red light best

Chloroplasts

Photosynthesis occurs

in plant organelles called

chloroplasts

Describe Photosynthesis

Method of converting

sun energy into

chemical energy usable

by cells

Uses sunlight to

convert H2O and CO2

into sugars and O2

Energy is stored as

sugar

Plants need light

energy, CO2, and H2O

Photosynthesis Reactions

(requires energy,

like driving a car.

Fuel = light)

Why do we need Plants and Other Photosynthetic organisms?

Without Photosynthetic organisms, we’d suffocate : WHY?

– The oxygen released during photosynthesis is necessary for all living things.

Without photosynthetic organisms, we’d starve : WHY?

– We cannot make our own food (glucose, energy), we must get our food from plants.

– Plants are the first step in the food chain.

So: Animals and plants are interdependent

Energy and Matter in Ecosystems