Light Reactions and The Calvin Cycle Flashcards
Describe the process of photosynthesis and where it occurs.
Photosynthesis is process of plants converting light energy (from sun) into chemical energy.
-Uses energy of sun to convert carbon dioxide and water into Carbohydrates and oxygen
Photosynthesis occurs in chloroplasts.
What are the two parts of photosynthetic process. Describe each part.
Photosynthesis has two parts:
1. Light Reactions- transform light energy into ATP and Biosynthetic REDUCING POWER, NADPH (occurs in thylakoid discs)
2. Dark reactions (light-independent): The Calvin cycle.
- Use the product of light reactions (ATP, NADPH) to reduce carbon atoms from fully oxidized state (CO2) to their more reduced state such as hexose
(drive reduction of CO2 to glucose and other sugars)
NADPH carries and donates electrons.
What are Dark reactions also known as?
Dark reactions also known as Calvin Cycle or light -independent reactions. This reaction takes place in the STROMA.
List and describe the structural parts of chloroplast.
Similar to mitochondria, Chloroplast have three membranes:
inner membrane, outer membrane, thylakoid membrane
-have stroma (contain enzymes that use NADPH to convert CO2 to sugar)
-have stroma (like matrix of mito)
-the thylakoid membrane and inner membrane are impermeable to ions; outer membrane of chloroplast are highly permeable to and small molecules ions.
Thylakoid membranes (like cristate in mito are site of oxidation-reduction reactions)
What occurs in the Calvin Cycle? What are the three stages?
The Calvin cycle traps CO2 gas as 3-PHOSPHOGYLCERATE, a precursor to hexose sugars
Three stages of Calvin Cycle:
1. Fixation of Co2 by Ribulose 1,5-bisphosphate to form two molecules of 3-phosphoglycerate
2. reduction of 3-phosphoglycerate to hexose sugars
3. The regeneration of ribulose 1,5 bisphosphate
How are electrons carried in the light reactions?
In light reactions, photosystems absorb photons to generate reducing power and ATP for biosynthetic processes.
describe the functions of the two main photosystems used in light reactions.
Photosystem I- absorb photon to capture electrons for reducing NADP+ to NADPH
Photosystem II- send electrons through cytochrome b6f to generate proton gradient and produce ATP.
photosystem II -send electrons through cytochrome then on to PSI so it can be replaced by NADP (e- replaced when 2 molecules of H20 oxidized to O2).
What is the flow of electrons in the photosystems?
Electrons flow from water through PSII to cytochrome b6f complex and PSI and are finally accepted by NADP+.
This flow leads to formation of proton gradient.
Describe the regulations of three main hormones: Insulin , Glucagon and epinephrine/adrenaline.
High insulin, you store glucose, and NADPH will increase. Cell will start biosynthesis, glucose synthase activated. Drives the synthesis of glycogen and turn off glycogen cleavage.
High glucagon- you are in fasting state, turn on all enzymes to degrade glycogen to glucose. Activate phosphorylase
High epinephrine- glycolysis increases, breakdown of triacylglycerides, fatty acids, and more acetyl coa needed. seen in exercising muscles (releasing adrenaline).
What happens when there are high levels of NADPH?
High levels of NADPH, Catabolic (breakdown) pathways stop, CAC and glycolysis stops and the transfer of electrons are blocked.
compare and contrast regulation of glucose in blood vs other cells.
insulin regulates glucose levels in blood
Liver- provide glucose to the rest of the body; including the brain which can use ketone bodies to obtain glucose.
*Understand that photosynthesis is composed of two parts; the light reactions and the dark
reactions.
Light reactions:
o Energy from light is used to boost electrons from a low energy state to a high energy
state.
o These electrons are used to reduce NADP+ to NADPH (for biosynthesis).
o The electrons through, an electron-transport chain, are also used to generate a
proton-motive force which drives the synthesis of ATP.
• Dark reactions:
o Understand that the Calvin cycle takes place in the stroma of chloroplasts.
o Carbon dioxide gas is trapped as an organic molecule, 3-phosphoglycerate.
o 3-phosphoglycerate undergoes reduction reactions (using NADPH and ATP) to
synthesize hexose sugars.
