Energy, Life, and Photosynthesis

Energy• the ability to do work

• Energy comes in many forms.• Can we list some?

– Light – Heat – Electrical– Chemical

Energy

• Living things use chemical energy to get work done

Which type of energy do living things use?

• muscle contraction• nerve impulses• membrane pumps (active transport)• making proteins and nucleic acids• cell growth and repair• make and maintain order in the cell

Uses of Chemical Energy in the Body

Where in chemical compounds (FOOD) is the energy located?

• Energy in a molecule is in the chemical bonds formed between the atoms of that molecule.

• When a high-energy bond is broken and lower energy bonds are made, energy is released.

But how do living things release store and release chemical energy?

Energyfromfood

Energyfor cellwork

• Adenosine Diphosphate• a molecule by which one phosphate attaches

to create ATP– like an uncharged battery

ADP

ATP • Adenosine Triphosphate• an important chemical in life's never ending

need for energy • acts as a carrier of energy

• extremely useful as the basic energy source of all cells

• the third phosphate on an ATP molecule can readily be broken (releasing energy) and reformed (requires energy)

• cells possess only small amounts of ATP– it is used for cell work very quickly– cells need to constantly make it

ATP

Animation

Using the Energy in ATP and Converting ADP into ATP

Photosynthesis

Textbook pages 97 – 103

Photosynthesis • process used by plants

using light energy to create sugar (glucose, C6H12O6) from carbon dioxide (CO2) and water (H2O)

• oxygen gas (O2) is produced as a waste product and the light energy used is stored as chemical energy

Investigating Photosynthesis

• Jan Van Helmont (1643)– Carefully massed soil,

and tree seedling and watered over 5 years.

– Determined most of the mass of the tree came from water.

Investigating Photosynthesis• Joseph Priestley (1771)

– Lit a candle and placed a bell jar over it, watching the flame go out.

– Reasoned that there was something in the air necessary to keep the flame going.

– When a plant was placed under the bell jar, discovered that the candle could be relit after several days.

– Reasoned that the plant released something into the air necessary for the flame.

Investigating Photosynthesis• Jan Ingenhousz (1779)

– Showed the effect observed by Priestley only occurred when plants were exposed to light.

Investigating Photosynthesis• Julius Robert Mayer

(1845)– Proposed that plants

convert light energy into chemical energy

Photosynthesis Equation

Leaves• organs where

photosynthesis takes place

• provide a place for gas exchange

Chloroplast• oval shaped organelle in plant leaf cells where

photosynthesis takes place

Light• plants use visible light to power photosynthesis in

chloroplasts– visible (white) light is actually ALL visible colors of light– plants absorb energy from many different colors of light

Pigment• material that changes the color of reflected light• plants gather the sun’s energy with light absorbing

pigments

Pigment• the primary plant pigment is chlorophyll

Chlorophyll• plant pigment that

absorbs light energy very well in the blue, violet and red wavelengths of visible light

• Why are plants green?– chlorophyll reflects

green light

Carotenoids• secondary pigments• absorb different wavelengths of light

– produces fall leaf colors as plants break down chlorophyll– produces colors of many fruits and vegetables

Factors that affect Photosynthesis*think of the “ingredients” necessary for photosynthesis*

• characteristics of the ecosystem that a plant grows in can affect how well it can perform photosynthesis– some factors allow plants to make sugar quickly

while other factors slow down their ability to make sugar• light

– length of exposure, color, intensity or brightness (distance from source)

• CO2 concentration

• water amounts

Photosynthesis and Enzymes• plants use many enzymes to produce their

food made in the process of photosynthesis– enzymes are proteins that speed up chemical

reactions• enzyme efficiency can be affected by many factors

– Temperature– pH

• these factors can also speed up (or slow down) photosynthesis

Connection to ATP• But what do living things do with the sugar

made in photosynthesis?– Eventually…living things will break down sugar

and convert the energy into ATP– More on this later when we learn about cellular

respiration

Summary• Sometimes plants in a community will slow

down or stop performing photosynthesis. This can be brought on by drought, human activities, disease, or many other factors. Describe what would happen to other members of the plants’ community.