Photosynthesis

Photosynthesis in Overview Process by which plants and other autotrophs store the energy of sunlight into sugars. Requires sunlight, water, and carbon dioxide. Overall equation: 6 CO2 + 6 H20  C6H12O6 + 6 O2 Occurs in the leaves of plants in organelles called chloroplasts.

Leaf Structure Most photosynthesis occurs in the palisade layer. Gas exchange of CO2 and O2 occurs at openings called stomata surrounded by guard cells on the lower leaf surface. Palisade Spongy

Chloroplast Structure Inner membrane called the thylakoid membrane. Thickened regions called thylakoids. A stack of thylakoids is called a granum. (Plural – grana) Stroma is a liquid surrounding the thylakoids.

Pigments Chlorophyll A is the most important photosynthetic pigment. Other pigments called antenna or accessory pigments are also present in the leaf. Chlorophyll B Carotenoids (orange / red) Xanthophylls (yellow / brown) These pigments are embedded in the membranes of the chloroplast in groups called photosystems.

Photosynthesis: The Chemical Process Occurs in two main phases. Light reactions Dark reactions (aka – the Calvin Cycle) Light reactions are the “photo” part of photosynthesis. Light is absorbed by pigments. Dark reactions are the “synthesis” part of photosynthesis. Trapped energy from the sun is converted to the chemical energy of sugars.

Light Reactions Light-dependent reactions occur on the thylakoid membranes. Light and water are required for this process. Energy storage molecules are formed. (ATP and NADPH) Oxygen gas is made as a waste product.

Dark Reactions Dark reactions (light-independent) occur in the stroma. Carbon dioxide is “fixed” into the sugar glucose. ATP and NADPH molecules created during the light reactions power the production of this glucose.

Copyright Cmassengale ATP to ADP Copyright Cmassengale

Copyright Cmassengale What Is ATP? Energy used by all Cells Adenosine Triphosphate Organic molecule containing high-energy Phosphate bonds Copyright Cmassengale

Chemical Structure of ATP Adenine Base 3 Phosphates Ribose Sugar Copyright Cmassengale

Copyright Cmassengale What Does ATP Do for You? It supplies YOU with ENERGY! Copyright Cmassengale

How Do We Get Energy From ATP? By breaking the high- energy bonds between the last two phosphates in ATP Copyright Cmassengale

Copyright Cmassengale How Does That Happen? An Enzyme! ATPase Copyright Cmassengale

Copyright Cmassengale How is ATP Re-Made? The reverse of the previous process occurs. Another Enzyme is used! ATP Synthetase Copyright Cmassengale

Cellular Respiration A quick review… When we eat, we get energy (glucose and other sugars) Food energy is broken down into usable energy Energy used to bond phosphate groups to ADP to make ATP

Cellular Respiration What is cell respiration??? Respiration: the process of breaking down food molecules into usable energy. THE GOAL : Create ATP for cells to use Free up electrons – have high energy

Other Cellular Respiration Facts Metabolic Pathway that breaks down carbohydrates Process is Exergonic as High-energy Glucose is broken into CO2 and H2O Process is also Catabolic because larger Glucose breaks into smaller molecules Copyright Cmassengale

Where Does Cellular Respiration Take Place? It actually takes place in two parts of the cell: Glycolysis occurs in the Cytoplasm Krebs Cycle & ETC Take place in the Mitochondria Copyright Cmassengale

What are the Stages of Cellular Respiration? Glycolysis The Krebs Cycle The Electron Transport Chain Copyright Cmassengale

Copyright Cmassengale Glycolysis Summary Takes place in the Cytoplasm Anaerobic (Doesn’t Use Oxygen) Requires input of 2 ATP Glucose split into two molecules of Pyruvate or Pyruvic Acid Copyright Cmassengale

Copyright Cmassengale Glycolysis Summary Also produces 2 NADH and 4 ATP Pyruvate is oxidized to Acetyl CoA and CO2 is removed Copyright Cmassengale

Copyright Cmassengale Fermentation Occurs when O2 NOT present (anaerobic) Called Lactic Acid fermentation in muscle cells (makes muscles tired) Called Alcoholic fermentation in yeast (produces ethanol) Nets only 2 ATP Copyright Cmassengale