Cellular Energy (8.1-8.2) Cellular Energy

8.1 Energy: The ability to do work

Autotrophs Organisms that make their own food Use sun directly Chemoautotrophs: use inorganic substances instead of sunlight Photoautotrophs: use the sun for photosynthesis

Heterotrophs Organisms that need to ingest food to obtain energy

Metabolism :all of the chemical reactions within a cell Catabolic pathway: releases energy by breaking larger molecules down Example: cellular respiration Anabolic pathway: use energy release from catabolic pathway to build larger molecules Example: Photosynthesis

8.2 Photosynthesis series of reactions that use carbon dioxide to form carbohydrates Examples of carbohydrates: glucose, sucrose Light energy is turned in chemical energy Who undergoes photosynthesis? Autotrophs!

Overview of photosynthesis and respiration SUN RADIANT ENERGY CELL ACTIVITIES PHOTOSYNTHESIS RESPIRATION GLUCOSE ATP(ENERGY)

2 phases of Photosynthesis: Light – dependent reactions: converts light energy into chemical energy Light – independent reactions: ATP from dependent reactions fuel these reactions to produce glucose (sugar)

The Photosynthesis Equation 6CO2 + 6H2O + light energy --> C6H1206 + 6O2 (reactants) (products) CO2 = carbon dioxide H2O = water O2 = oxygen C6H1206 = glucose (sugar)

It Begins with Sunlight!

A. Light-Dependent Reactions Require sunlight Sunlight strikes chloroplasts, and the light energy is captured Thylakoids: flattened sac-like membranes arranged in stacks (called grana) Stroma: fluid-filled space outside of grana (this is where the 2nd phase occurs!)

Light-Dependent Reactions (cont’d) Pigments: molecules that absorb specific-colored light Chlorophyll a and Chlorophyll B: absorb violet/blue and reflect green Carotenoids: absorb blue/green and reflect yellow/orange/red (think of carrots!)

Light-Dependent Reactions (cont’d) What happens to the chlorophyll when leaves change colors? Chlorophyll begins to break down; therefore cannot absorb all other colors, so only the red/orange/yellow is reflected

What is produced in the light reactions? Products of the light reactions (light dependent reactions) go on to the Calvin Cycle NADPH, ATP, and oxygen as byproducts

What’s necessary for the light reactions? NADP, ADP, water, and sunlight.

Light-Dependent Reactions (cont’d) Thylakoid membrane is the key to the electron transport chain (ETC) ETC: series of electrons embedded in the thylakoid membrane -acts as a bucket brigade (electrons lose their energy little by little) Chemiosmosis: Water is broken down to produce ATP in conjunction with electron transport :process by which ATP is produced by the flow of electrons down a concentration gradient

The Light-Independent Reactions Now that the Light reactions (Light-dependent) reactions are complete…these products go to (or feed) the next phase… The Light-Independent Reactions (or Dark Reactions)

Light-Independent Reactions Aka Calvin Cycle Does not need light Takes place in stroma of chloroplasts Named after Melvin Calvin

If there is not enough water or carbon dioxide or sunlight to undergo photosynthesis, what happens? C4 Pathway: helps maintain photosynthesis while minimizing water loss Examples: corn, sugarcane CAM pathway: occurs in water-conserving plants from deserts, salt marshes, etc. Examples: pineapple, orchids, cactus (cacti)

What’s Necessary for the Dark Reactions? The dark reactions cannot take place without the ATP and NADPH that was produced during the light reactions. Recall that ATP and NADPH are energy carriers. Carbon dioxide from the environment is also necessary for the dark reactions.

What’s produced by the dark reactions? Glucose (a 6 carbon sugar) and other energy storing organic compounds are made. NADP+ and ADP are produced to be reused by the light reactions.

Concept Map Photosynthesis Light dependent reactions Light independent includes Light dependent reactions Light independent reactions occurs in uses uses occur in Light Energy Thylakoid membranes Stroma ATP NADPH to produce of to produce ATP NADPH O2 Chloroplasts Glucose

BIG Factors Affecting the Rate of Photosynthesis Amount of available water Temperature Amount of available light energy