Cellular Process
Quick Review of Chloroplast Structure
Chloroplasts contain thylakoids, grana, outer and inner membranes.
Light Dependent Reactions and Photosystems
Activated by light, which excites the process needed to synthesize glucose.
Photosystems produce ATP and NADPH, required for light-independent reactions (Calvin Cycle).
Splitting water molecules () releases Hydrogen ions, Oxygen atoms, and electrons; electrons replace those in PS2.
Oxygen molecule is produced during this process.
Steps in Light-Dependent Reactions
Hydrogen (H^+$) ions are released.
Photoactivation excites electrons transferred to NADP+ to generate NADPH.
NADP+ reductase helps electrons from PS1 join NADP+ to generate NADPH (NADP+ is reduced).
Higher concentration of H+ in the thylakoid.
Facilitated diffusion of H^+H^+CO_2 to RuBP.
1 carbon atom in carbon dioxide, 5 carbon atoms in RuBP.
The resulting 6-carbon molecule splits into two 3-carbon molecules (GP or PGA).
Step 2: Reduction of GP
Electrons from NADPH are added to GP, reducing GP molecules.
NADPH is oxidized (loses electrons).
ATP is required for GP reduction.
Reduced GP molecules become TP molecules.
One TP molecule goes to make Glucose, while others regenerate RuBP.
Reduction of GP Details
GP is reduced to TP (3-carbon molecule).
NADPH is oxidized, ATP is used.
Step 3: Regeneration of RuBP
One TP molecule makes glucose; the other five regenerate RuBP.
Since TP is a 3-carbon molecule and RuBP is a 5-carbon molecule, five TP molecules are needed to create three RuBP molecules.
G3P is TP.
Regeneration of RuBP Details
Five TP molecules (5 x 3C) create three RuBP molecules (3 x 5C) with the help of ATP.
Calvin Cycle Products
One molecule of Glucose has 6 carbons.
The Calvin Cycle diagram needs to occur twice to make one glucose molecule, since we need 2 TPs to make 1 Glucose
The Calvin Cycle produces Carbohydrates, Lipids, and proteins.
Light Independent Reactions and the Calvin Cycle
The Calvin Cycle
Calvin Cycle Review
ATP, NADPH, G3P.
Calvin Cycle & Light Reactions
Light-dependent reactions use light energy to generate ATP and NADPH, which are required to shuffle carbon atoms in the Calvin Cycle to make glucose and regenerate RuBP.
ATP and NADPH are limiting factors for photosynthesis.
Carbon dioxide is also a limiting factor.
Factors Affecting Photosynthesis
Light Intensity, Carbon Dioxide Concentration, and Temperature.
Measuring Photosynthesis
Measure the rate of oxygen production or carbon dioxide intake.
Track changes in biomass (indirect reflection of photosynthetic rate).
Factors Influencing Rate of Photosynthesis
Photosynthesis is a metabolic pathway influenced by: carbon dioxide concentration, light intensity, and temperature.
Carbon Dioxide Concentration
Carbon dioxide is a substrate for the enzyme Rubisco.
An initial increase in CO2 concentration increases the reaction rate.
Eventually, enzymes saturate, and further CO2 increase does not increase the rate of reaction.
Rubisco and Saturation
Enzymes reach a saturation point.
Once all active sites are filled, the speed reaction cannot proceed faster unless you increase the amount of enzyme rather than substrate (CO2).
Light Intensity
Light is needed for light-dependent reactions to create ATP and NADPH for the Calvin Cycle.
Initially, increased light intensity leads to more photoactivation and photosynthesis.
At a certain point, all photosystems are activated, and the reaction plateaus.
Light Intensity and Photoactivation
Increasing light intensity increases photoactivation, ATP/NADPH production, and photosynthesis rate, up to a point.
Once all photosystems are activated, increasing light intensity does not further increase the reaction.
Temperature
Photosynthesis relies on enzymes, so temperature affects the reaction rate similarly to enzymatic activity.
Temperature and Enzyme Activity
Increased temperature increases collisions and the reaction rate.
Above a certain temperature, enzymes denature, and the reaction slows down.
A factor is limiting if an increase in that factor increases the reaction rate.
Limiting Factors Overview
Light, carbon dioxide, temperature.
Limiting Factors and CO2 levels
At 800 Wm^{-2}CO_2CO2CO2CO2O2.
Oxygenated blood returns to the heart and is pumped around the body.
Electron Carrier Review
Reusable molecules produced during cellular respiration: ADP & ATP, NAD+ & NADH, FAD & FADH2.
ATP Importance
ATP stands for adenosine triphosphate.
Any cellular processes needing energy require ATP.
ATP is generated by Hydrolysis (catabolic reactions).
Energy Source
Photophosphorylation relies on light energy, and oxidative phosphorylation relies on the movement of electrons.
Cellular Respiration Relevance
All living things generate ATP through cellular respiration.
Cellular Respiration equation: C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O$$
Cellular Respiration is a combustion reaction that releases energy stored in glucose to create ATP.
Overview of Cellular Respiration
Four steps: Glycolysis, Pyruvate Oxidation, Citric Acid Cycle, ETC
Cellular Respiration Steps
Glycolysis, Link Rxn, Kreb’s Cycle, ETC
ETC (oxidative phosphorylation).
Kreb’s Cycle.
ETC (oxidative phosphorylation).
ETC yields about ~36 ATP.
Step 1: Glycolysis
"Glyco" refers to sugar, and "lysis" refers to splitting, meaning