Photosynthesis and Cellular Respiration

Photosynthesis Basics

• Purpose – to make food• Place – Chloroplast• Energy Conversion – Light (Sun) to Cellular

(ATP to Chemical Potential (Glucose)• Steps:

1. Light Independent Reactions2. Light Dependent Reactions

Light Dependent Reactions

• Also called “Light Reactions” or “Electron Transport”

• Purpose – to convert water and sunlight to ATP and NADPH

• NADPH is a high energy electron carrier• Place – across thylakoid membranes in the

chloroplasts

Light is a type of electromagnetic radiation

• Electromagnetic radiation are energy waves emitted by different processes around us all the time

• Radio waves, infrared waves, ultraviolet, gamma rays, x rays are examples

• Most of them we cannot see, but our eyes are able to detect a very small range of wavelengths we call visible light

• Colors appear different because they are different wavelengths of light

Sunlight or “white” light

• “White” light is a combination of all the wavelengths of light mixed together (our eyes can’t separate them)

Visible Light Spectrum

• Chlorophyll is a pigment molecule found in plant cells

• Carotenoids and other pigments are called accessory pigments

• Together they absorb most of the wavelengths of light in the visible spectrum

• They do not absorb green and some yellow• Those wavelengths are reflected back to our

eyes making plants appear to be green

Light Independent Reactions

• Also called “Dark reactions” or “Calvin Cycle”

• Purpose – To use the ATP and NADPH from the Light reactions and the CO2 absorbed from the atmosphere to make glucose

• Place – Stroma of the chloroplasts

Cellular Respiration

• Purpose – to break down molecules from the food you eat and convert the energy stored in them to ATP

• Place – mainly in the mitochondria• If oxygen is not present – Anaerobic Respiration

(Fermentation)• If oxygen is present – Aerobic (2 steps)

1. Kreb’s Cycle2. Electron Transport

Glycolysis

• Purpose – to split glucose in half• Place – Cytoplasm• Products – 2 NADH, 2 Net ATP

• If oxygen is present in the cell, the two halves of glucose will enter the Mitochondria

Aerobic Respiration

• Occurs when oxygen is present• After glycolysis the two halves of glucose enter

the mitochondria and are completely broken down to carbon dioxide molecules by 1. Kreb’s Cycle2. Electron Transport Chain

Kreb’s Cycle

• Purpose – to break down glucose to 6 carbon dioxide molecules

• Place – Matrix of the mitochondria• Products – 2 ATP, 6 NADH, 2 FADH2• NADH and FADH2 areHigh energy electron carriers(still carrying some of theEnergy from glucose)

Electron Transport

• Purpose – to make ATP from high energy electrons

• Place – across the inner membrane of the mitochondria

• Products – 28-34 ATP• Electron Transport uses the high energy

electrons from all the NADH and FADH2 that have been made to make ATP

Electron Transport

Bookkeeping

• Each NADH molecule carries enough energy to make 3 ATP

• Each FADH2 molecule carries enough energy to make 2 ATP