Photosynthesis and Cellular Respiration Chapter 5

5.1 Energy and Living Things Remember: Metabolism is either the energy used to build molecules or the release of energy by breaking down molecules

Photosynthesis Turn light energy into chemical energy Autotrophs – make their own food Most are photosynthetic Some are chemosynthetic (get energy from inorganic compounds)

Cellular Respiration Get energy from food Heterotrophs – must ingest energy Produces ATP

Transfer of Energy to ATP Energy from food released gradually in a series of enzyme-assisted chemical reactions Product of 1 reaction becomes the reactant in the next reaction Some energy is released as heat Most energy is stored in ATP which can deliver it where it is needed

How ATP Works (Yes, again) ATP = Adenosine Triphosphate 3 negative phosphates repel each other Energy released when bonds break Produces ADP = adenosine diphosphate

Can be reversed back into ATP If a 2nd phosphate is broken off = irreversible Water is used in breaking H2O + ATP = ADP + P + ENERGY

Photosynthesis Stages of Photosynthesis First 2 are called Light Dependent Reactions Stage 1: Energy is captured from sunlight Stage 2: Light energy is changed to chemical energy Chemical energy stored temporarily in ATP and a carrier molecule called NADPH Stage 3 is called Light Independent or Dark Reactions Energy in ATP and NADPH powers the formation of organic compounds using CO2

Where does all of this take place? In the chloroplasts of plant cells and algae and in the cell membrane of certain prokaryotes 6CO2 + 6H2O light> C6H12O6 + 6O2 Carbon dioxide and water make sugars and oxygen with the help of light energy Some sugars form starch and are stored in stems and roots These can be broken down later to make ATP Sugars break down and make proteins, nucleic acids, and others

Stage 1 Absorption of Light Energy (Light Dependent) Light is a form of radiation Pigments are light absorbing substances But they only absorb certain wavelengths Chlorophyll is the primary pigment Absorbs mostly blue and red Reflects green and yellow which is why we see them as these colors

A few different kinds Chlorophyll a Chlorophyll b Carotenoids Yellow and orange reflecting pigments Absorb different wavelengths than chlorophyll

5.3 Cellular Respiration You eat food and the chemical energy is transferred to ATP This is called Cellular Respiration This is much more efficient with Oxygen and this is called Aerobic When no Oxygen it is called Anaerobic

Cellular Respirations Formula C6H12O6 + 6O2 enzymes> 6CO2 + 6H2O + energy (ATP) How does it compare to the equation for Photosynthesis?

Respiration in the Absence of Oxygen 38 ATPs can be made if there is Oxygen Only 2 ATPs when oxygen is absent When no oxygen is present we have fermentation

Lactic Acid Fermentation During strenuous exercise when oxygen has run out, a chemical (pyruvate) in muscles is converted to lactate If this is not removed quickly it can build up in muscles and cause soreness

Alcoholic Fermentation In other organisms the pyruvate is instead turned into ethanol Used by yeast and fungi to make wine, beer, and bread