Energy and Life

Energy

• Energy is the ability to do work or the capacity to cause change.

• Autotrophs and Heterotrophs– Autotrophs – make their own food from the

sun’s energy (aka producers)– Heterotrophs – obtain energy from food they

must consume (aka consumers)

Chemical Energy and Food

• Food provides energy for organisms

• One gram of glucose (C6H12O6) can release 3811 calories of heat. A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius

Chemical Energy and ATP

• Energy stored in many forms – light, heat, electricity, and chemical compounds

• ATP and ADP – activities of cells powered by chemical fuels

Adenine Ribose 3 Phosphate groups

An ATP Molecule

ATP & ADP

• Cells store energy in ATP (adenosine triphosphate) – nitrogen, 5-carbon sugar, 3 phosphate groups = fully charged “battery”

• ADP (adenosine diphosphate) – similar to ATP, but with one less phosphate group = ADP used to store energy by adding 1 more phosphate to it = partially charged “battery”

ADP ATP

Energy

EnergyAdenosine diphosphate (ADP) + Phosphate Adenosine triphosphate (ATP)

Partiallychargedbattery

Fullychargedbattery

Comparison of ATP and ADP to a Battery

ADP ATP

Energy

EnergyAdenosine diphosphate (ADP) + Phosphate Adenosine triphosphate (ATP)

Partiallychargedbattery

Fullychargedbattery

Comparison of ATP and ADP to a Battery

Releasing Energy from ATP

• Energy released from ATP when ATP is converted into ADP and phosphate. Because a cell can add or subtract a third phosphate group, this is a great way of storing and releasing energy as needed

• Energy released/used when phosphate bond is broken (phosphate is negatively charged and wants to repel each other = lots of energy)

• ATP carries energy needed by the cell for:– Active transport– Movement within the cell (organelles)– Muscle movement– Chemical reactions

Photosynthesis – An Overview (for now…)

• Photosynthesis – plants, algae, and certain bacteria transform light energy into chemical energy, using carbon dioxide and water as starting materials. This chemical energy is stored in sugars/starches.

Inside a Chloroplast

– Photosynthesis occurs in the chloroplasts• Chloroplasts contain pouch-like photosynthetic membrane

called thylakoids which are arranged in stacks called grana• Thylakoids contain clusters of chlorophyll and other

pigments/proteins able to capture sun’s light• Stroma – space surrounding thylakoids

Interior cell

StromaGranum

Thylakoidspace

ChloroplastInner and outermembranes

The Photosynthesis Equation

6CO2 + 6H2O C6H12O6 + 6O2 Carbon dioxide + water sugar + oxygen

Chloroplast

CO2 + H2O Sugars + O2

Light

A Photosynthesis Road Map

– 1. Light Reactions – aka light-dependent reactions - takes place within thylakoid membranes

• Makes ATP and NADPH for Calvin Cycle

– 2. Calvin Cycle – aka light-independent reactions – takes place in the stroma – a region outside thylakoid membrane

• Makes glucose

A Photosynthesis Road Map

Chloroplast

Light

O2

Sugars

CO2

LightReactions

CalvinCycle

NADPH

ATP

ADP + PNADP+Chloroplast

Light and Pigments

• Photosynthesis requires light and chlorophyll – a molecule in chloroplasts

• Plants gather sun’s energy with light-absorbing molecules called pigments. The major pigment plants use is chlorophyll

• ***Plants are green in color because they absorb all colors of visible light except green light – which is reflected***

• When chlorophyll absorbs light, the sun’s energy is directly transferred to electrons in the chlorophyll molecule, raising the energy levels of these electrons, making photosynthesis work

Light

Chloroplast

Absorbedlight

Transmittedlight (detectedby your eye)

Reflectedlight

What color(s) does Chlorophyll a absorb most?

What color(s) does Chlorophyll b absorb most?

Why is the color green the least absorbed?