Photosynthesis and Chemosynthesis

Energy in a cell  Cells need energy to:  Grow  Reproduce  Live  Energy for these reactions can be stored in glucose  To use energy, though, it needs to be in molecules called ATP

ATP – Adenosine Triphosphate  Energy – carrier molecule  3 phosphate groups  Energy is released when 3 rd phosphate group is cut off  ATP  ADP + P + Energy  Released energy is used to power cell activity

Energy from the Sun  Some organisms gain energy from consuming other organisms – called heterotrophs  Other organisms can make their own food – called autotrophs  Plants, algae, and some bacteria capture about 1% of the sun’s energy  convert it to chemical energy through the process of photosynthesis

Photosynthesis Equation LIGHT LIGHT  6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 Occurs in the chloroplast of plant cells

Chloroplast Structure Little “coin-like” structures called Thylakoids Membrane surrounding thylakoids contains chlorophyll Stacks of Thylakoids called Grana Space surrounding Grana is called the Stroma

Photosynthesis Video

Stages of Photosynthesis 1.Light Reactions 2. Light-Independent Reactions (Calvin Cycle)

Stages of Photosynthesis 1. The Light Reactions  Light energy is absorbed and converted to chemical energy in the bonds of ATP. 1. Light strikes electrons in the chlorophyll 2. Energy from excited electrons used to make ATP molecules 3. Energy now available to do work.

Light Reactions…  Water is split into hydrogen ions, oxygen, and electrons  Electrons replace those lost by the chlorophyll molecule  Oxygen is given off as waste  Hydrogen ions are used to create NADPH (another energy carrier molecule) for use in later steps of photosynthesis

Calvin Cycle Light – Independent reactions  The ‘synthesis’ part of photosynthesis  Takes place in the stroma of the chloroplast  Uses ATP and NADPH from light reactions  Enzymes combine CO 2 with hydrogen (from NADPH) and energy from ATP

Light Energy  Light energy has different wavelengths – we see them as different colors  Pigment – a protein that absorbs light  Chlorophyll – a pigment in the chloroplast  Absorbs red and blue light  Reflects green and yellow light – we see that reflected light.  Carotenoids – pigments that make plants yellow and red in the fall ROY G. BIV

Chemosynthesis  Similar to Photosynthesis – but no light!  Inorganic compounds are used for energy to make sugars  Ex: bacteria can do this in the hydrothermal vents at the bottom of the ocean

Chemosynthesis Video