Cell Energy: Photosynthesis & Respiration

Autotroph or Heterotroph? Why? How does it make its own food? PHOTOSYNTHESIS

Overview of Photosynthesis and Respiration Photosynthesis –Use of sunlight to make carbon compounds (food) Cellular Respiration – Turns food into ATP (energy) Autotrophs Photosynthesis and Cellular Respiration Why both? Because autotrophs have to make their food first and then break it down. Heterotrophs Cellular Respiration

How Does a Plant Make It’s Own Food? Plants use carbon dioxide (CO2), water (H2O), and sun’s energy to make food. This is called photosynthesis The food gives plants energy Animals get the energy stored in plants when they eat them.

What “Food” do Plants Make? The “food” plants make is a sugar called glucose (C6H12O6). Glucose and oxygen (O2) are made during photosynthesis.

Overview of Photosynthesis Light energy from the sun is converted to chemical energy. The chemical energy in ATP powers the formation of organic compounds (food) using carbon dioxide.

Some Review…. Chloroplasts – an organelle found in plant and algae cells where photosynthesis occurs

Some Review…. Thylakoid – membrane system within chloroplasts that contains the components for photosynthesis Stroma – fluid surrounding the thylakoid inside chloroplasts

Stage One: Light Dependent Reactions Leaves contain light-absorbing substances called pigments located in the chloroplast. Chlorophyll is the primary pigment used. Why is it green? It absorbs mostly blue and red light and reflects green and yellow. Pigments are stored in thylakoids.

Stage One: Light Dependent Reactions What Happens? Light strikes a thylakoid in a chloroplast, energy is transferred to the electrons in the chlorophyll. The electrons jump to a higher energy level and are said to be “excited”.

Light Dependent Reaction The series of molecules through which excited electrons are passed along a thylakoid membrane are called Electron Transport Chains. What Happens Next: 3. The electron moves down the chain and makes NADPH which carries the electron to the next stage. The excited electrons cause hydrogen to come into the thylakoid. 2. This sets up a concentration gradient of Hydrogen that provides the energy to make ATP.

Stage 2: Light Independent Reaction ATP and carbon dioxide are used to make carbon compounds (food) What Happens? Calvin Cycle- a series of enzyme-assisted chemical reactions that produces a three-carbon sugar (food).

What affects photosynthesis? Light Intensity Temperature Carbon Dioxide Concentration Water Availability

REVIEW What are the stages of photosynthesis, where are they located, and what do they do? 1. Light dependent reactions in thylakoid membrane Captures sunlight Makes ATP (stored energy) 2. Light independent reaction in the stroma Uses CO2 , and ATP to make carbon compounds (food)