Review: Energy CurrencyWe already know: The energy currency for the cell is a molecule calledAdenosine Triphosphate (ATP)
A = Adenosine ATP = A ~ P ~ P ~ P P = Phosphate ADP = A ~ P ~ P ~ = chemical bond AMP = A ~ P The breaking of a bond (~) in ATP releases energy
A~P~P~P A~P~P + P + ENERGY
The making of a bond (~) in ATPbottles up energy for later userequires energy input
A~P~P + P + ENERGY A~P~P~P
Energy and LifeAll living things have a need for energy(this is a characteristic of life!)
Scientists classify living organisms into two groups based on how they get their food
Autotrophs : organisms (like plants) that produce their own food from the energy in sunlight Are there any other autotrophs besides plants?Heterotrophs : organisms that cannot make their own food and must consume in order to obtain energy
A Story of EnergyOn a sunny plain in Africa, a herd of zebras peacefully eat the grass. But watch out! the unsuspecting grazers are about to be harshly interrupted. A group of lions is stalking the herd, creeping ever closer, and nearly ready to pounce. Suddenly, the lions strike forward, killing one of the zebras and devouring its carcass. Answer the following questions in your notebook:How many different types of living things (organisms) are featured in this story?Which (if any) are heterotrophs? autotrophs?Where is the energy of this system coming from?Without producers, what would happen to consumers?
Photosynthesis, Respiration, the formation of ATP, and the breakdown of ATP form a fundamental biological cyclePhotosynthesis Stores energy from sunlight in glucose moleculesRespiration Releases the energy from glucose molecules and generates ATPATP breakdown Powers cell activities
Biochemical Pathway: A series of chemical reactions, in which the product of one reaction is the reactant in the next reaction Example: Photosynthesis
Intro to: PhotosynthesisPhotosynthesis the cellular process by which solar energy is stored in chemical bondsOverall, the reaction is as follows: Reactants Products6 CO2 + 6 H2O + (light) energy C6H12O6 + 6 O2Photosynthesis is a complicated, 2-step processLight ReactionsLight is capturedOxygen is releasedATP is formed Dark ReactionsCarbon dioxide is combined with hydrogen in order to form glucose
ChloroplastsStructureDouble membraneInterior is organized into flattened sacs (thylakoids)A stack of thylakoids is called a granum (plural grana)Lumen : interior space of a thylakoidStroma : protein-rich solution found between the thylakoid membrane and the outer membrane of the chloroplastLight reactions occur on the thylakoid membranesDark reactions occur in the stroma
The Nature of LightLight from the sun appears white, but it is actually composed of a variety of colors
Violet Indigo Blue Green Yellow Orange Red
Light is made of particles of energy that move in waves (dual nature)
Each color has a different amount of energy Each color has a different wavelength
When striking something, colors may be: - Absorbed (we no longer see it) - Reflected (we see it) - Transmitted (it passes through)
The Biology of Autumn ColorsPigment a colored chemical compound that absorbs light The main photosynthetic pigment found on the membranes of the chloroplasts is called CHLOROPHYLL (Two types: a and b)Responsible for the green appearance of plantsIn the fall, photosynthesis slows down, as does chlorophyll production This reveals other pigments(Example: caroteniods, which appear orange/yellow/brown)
Question: What color(s) do chlorophyll a and b each absorb and reflect?
Plant Pigment Separation by Chromatography
Light (Dependent) Reactions
Question: Why do they call it this?
Three Steps of the Light Reactions:Electron Transport Chain- Restoring Photosystem II- Chemiosmosis
I. Electron Transport ChainPhotosystem: a cluster of pigment moleculesA light photon excites an electron in Photosystem IIThis electron travels from molecule to molecule along the transport chain, losing energy along the wayThe energy lost by the electron is used to pump protons (H+) into the thylakoid lumenSimilarly, light excites an electron in Photosystem I, which is passed along another transport chainAt end of this chain: e- + H+ + NADP+ NADPH
II. Restoring Photosystem IIThe answer is. WATER !!!!!A thylakoid enzyme splits water molecules as follows: 2H20 4H+ + 4e- + O2This creates: ELECTRONS for the transport chain, as well as OXYGENWe know that the electron departing from Photosystem I is replaced by the electron finishing Photosystem IIs transport chainBUThow are the electrons leaving Photosystem II replaced?
Chemiosmosis synthesizes ATPRemember : the high concentration of protons built up inside the thylakoids as a result of the transport chainThe protons diffuse (which direction?) through a carrier enzyme called ATP synthase The protons passing through this enzyme cause it to synthesize ATP from ADP + P
The 2 Main Products of the Light Reactions:NADPHATP(Both will be needed in the dark reactions)
Photosynthesis: The Big Picture
Remember this is called a biochemical pathway