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 (C 6 H 12 O 6 ) 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 AdenineRibose3 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”

ADPATP Energy Adenosine diphosphate (ADP) + PhosphateAdenosine triphosphate (ATP) Partially charged battery Fully charged battery Comparison of ATP and ADP to a Battery

ADPATP Energy Adenosine diphosphate (ADP) + PhosphateAdenosine triphosphate (ATP) Partially charged battery Fully charged battery 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 Stroma Granum Thylakoid space Chloroplast Inner and outer membranes

The Photosynthesis Equation Chloroplast CO 2 + H 2 OSugars + O 2 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 O2O2 Sugars CO 2 Light Reactions Calvin Cycle NADPH ATP ADP + P NADP + 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 Absorbed light Transmitted light (detected by your eye) Reflected light

What color(s) does Chlorophyll a absorb most? What color(s) does Chlorophyll b absorb most? Why is the color green the least absorbed?