Photosynthesis Unit 3 – Part 1

Homeostasis -What is homeostasis? ____________________________________ ____________________________ -Organisms and the cells within them have to grow and develop, move materials around, build new molecules, and respond to the environmental changes. -It’s hard work! -What power so much activity and where does that power come from?

Chemical Energy and ATP - Energy is the ability to work! What makes a car go? When happens when a car runs out of energy? -The need for energy is always there! Even when we’re sleeping! -One of the most important compounds that cells use to store and release energy is, adenosine triphosphate

Storing and Releasing Energy - To get power = release of the phosphate at the tip - What is left = ADP It’s like ATP, but with one less phosphate! -ADP can store small amounts of energy. It’s like a rechargeable battery for your cells. The phosphate group can be added or subtracted. -Because it can do that is has an efficient way of storing and releasing energy.

So what do our cells actually use ATP for? It energizes three main kinds of work: -Mechanical Work -Transport Work -Chemical Work

The ATP Cycle - Your cells spend ATP continuously. - It’s renewable! …That’s where food comes into play!!! YUM - Chemical energy that cellular respiration harvests from sugars and other organic fuels is put to work regenerating a cell’s supply of ATP.

Energy Flow and Chemical Cycling in the Biosphere - All energy in food can be traced back to energy from the sun. -Photosynthesis uses light energy from the sun to power a chemical process that puts together organic molecules. -Autotrophs (producers) are organisms that make their own food.

Chemical Cycling -Photosynthesis and cellular respiration are interrelated. - Humans and other animals depend on plants to convert the energy of sunlight to the chemical energy of sugars and other organic molecules. -Heterotrophs (consumers) are organisms that cannot make their own food.

Sunlight and Photosynthesis

The sun, light and pigments! - Energy from the sun travels in the form of light - Sunlight is a type of energy called radiation - The “white light” is actually a mixture of different wavelengths - The visible spectrum - Plants gather the sun’s energy with light- absorbing molecules called pigments. - There are several different pigments found in chloroplasts.

Chloroplast Pigments - The plants’ principle pigment is chlorophyll. Chlorophyll a and Chlorophyll b -Does not absorb light well in the green region of the spectrum. -All built into thylakoid membranes. -Absorbs light = absorbs energy = transfer that energy to electrons

Equation for Photosynthesis

What is a photon of light? Photon is a fixed quantity of light energy. When a pigment absorbs a photon, electrons gain energy and become excited! It doesn’t last long… Most pigments release heat energy and some emit light… like a glowstick for example.

Photosystems…remember the electron cliff hanger?? HERE IT IS! Photosystems are clusters of few hundred pigment molecules (including chlorophyll a and chlorophyll b and carotenoids) Act like a light gathering antenna

Amoeba Sisters Video For your viewing pleasure “Photosynthesis and the Teeny Tiny Pigment Pancakes”

2 major reactions that occur in the chloroplasts Light Dependent Water splitting photosystem and NADPH- producing photosystem Light and Water go in Produces ATP, NADPH and Oxygen In the thylakoid membrane Light Independent (aka DARK REACTION, aka CALVIN CYCLE) CO2 must be fixed and produces GLUCOSE Not in the thylakoid, in the STROMA

Light Dependent Reaction

Light Independent Reaction (Calvin Cycle)

Light Independent Reaction

Photosynthesis Wrap-up Photosynthesis provides organic material and chemical energy for life on earth. Lots of hungry critters need this energy! It also swaps oxygen for carbon dioxide in the atmosphere. Photosynthesis moderates global warming.