Photosynthesis: Cellular Biochemistry

Cellular Biochemistry - Photosynthesis

• Cellular biochemistry focuses on photosynthesis as a key process.

Photosynthesis Overview

• Photosynthesis involves light energy transforming CO2 and H2O into organic molecules and O2.
• A chloroplast is where photosynthesis takes place.
• It is thermal energy that powers cellular work.

Study Resources

• Study resources include Campbell Biology textbooks from 2007, 2012, and 2020.
• Key content can be found in Chapter 10, concepts ranging from 10.1 to 10.5.
• There are laboratory exercises 2-2 on page 40.

Course Plan

• Introduction to autotrophs and heterotrophs
• Cellular structures
• Molecular structures and recall
• Location and equation of photosynthesis
• Biochemistry: photochemical reactions
• Photooxidation of chlorophyll
• Non-cyclic electron transport
• Chemiosmosis
• Cyclic electron transport
• Biochemical reactions or Calvin cycle
• Factors influencing photosynthesis
• Photorespiration
• Adaptation of C4 and CAM plants

Learning Objectives in Photosynthesis

• Differentiate autotrophy and heterotrophy.
• Describe the chloroplast, stating its function and structure.
• Express the general equation of photosynthesis.
• Explain the general principle of photosynthesis, considering its two phases.
• Identify the location where each phase of photosynthesis occurs.
• List photosynthetic pigments and their properties.
• Explain photo-oxidation of chlorophyll.
• Describe a photosystem.
• Define photophosphorylation.
• Outline photochemical reactions: reactants, products, and phosphorylation.
• Explain cyclic and non-cyclic electron transport.
• State the role of NADPH + H+ oxidation.
• Compare chemiosmosis in chloroplasts and mitochondria.
• List external factors influencing photosynthesis.
• Describe the Calvin cycle: reactants, products, and phosphorylation.
• Identify the fate of photosynthesis products.
• Illustrate all reactions linking inputs and outputs of photosynthesis molecules, considering the cell and involved organelles.
• Explain photorespiration and how it influences plants.
• Compare photosynthesis and photorespiration focusing on the differences between the two concepts
• Clearly describe adaptations of C₄ and CAM plants.
• Compare metabolic pathways and their energetic balance.

Reminder on Energy and Matter

• Light energy is converted into chemical energy during photosynthesis and is stored in chemical bonds.
• ATP is used for cellular processes such as muscle contraction and transport.

Photosynthesis Role

• The role of photosynthesis is to produce glucose from H₂O and CO2, utilizing energy from sunlight.
• The equation for photosynthesis describes how solar energy, water, and carbon dioxide are converted into glucose and oxygen.

Introduction to Photosynthesis

• Organisms must obtain organic compounds to produce ATP.
• Producers synthesize organic molecules from inorganic materials using CO2 and a light source.
  • Autotrophs are producers, including terrestrial plants and aquatic vegetation, algae, cyanobacteria.
• Consumers absorb organic molecules synthesized by other organisms as an energy and carbon source.
  • Heterotrophs can be animals, fungi, or heterotrophic bacteria.

Photosynthesis Location

• Photosynthesis takes place in the plants.
• The process happens in the chloroplasts of leaves, stems, and unripe fruits.

Chloroplast Structure

• Chloroplasts consist of an outer membrane and an inner membrane.
• Thylakoids are flattened membrane sacs found within, bathed in stroma.
• Thylakoids arranged in stacks form grana.
• The space inside thylakoids is the intrathylakoid space. The inner membrane contains unsaturated fatty acids, and also has liposoluble pigments

Metabolism Reminder

• Metabolism encompasses all biochemical reactions in an organism.
• Anabolism builds complex molecules from simple ones, consuming energy.
• Catabolism breaks down complex molecules into simpler ones, releasing energy.
• Autotrophs make the creation of their own source of food molecules by using light/ thermal energy
• The emergence of life is linked to metabolic interactions within a cell's ordered environment.

Thermodynamics

• Living organisms transform energy, the study of which is thermodynamics.
• The first law of thermodynamics is the conservation of energy, so the amount of energy is consistent.
• The second law states that energy exchange increases disorder (entropy). So energy transfers entail heat loss.

Potential Energy and Electron Arrangement

• Electrons can move between energy levels in electron shells during chemical reactions.
• Kinetic energy from electrons can support cellular work, like ATP synthesis.

Enzyme Function

• Enzymes assemble molecules, degrade them, or modify them.
• Some enzymes increase chemical reactions.

Photosynthesis and Enzymes

• Enzymes can assemble small molecules into larger ones, requiring energy and that's considered anabolism.
• Catabolism is when enzymes degrade larger molecules, liberating energy.
• Enzymes can modify molecules into similar molecules.

Factors Influencing Enzymes

• Cofactors impact the activity of enzymes.
• Enzymes rely on other molecules, cofactors, for catalytic activity
• Cofactors can be inorganic ions or coenzymes like NADH and NADPH.

Role of Coenzymes

• Coenzymes like NADP+/NADPH serve as shuttles for H+ and electrons in physiological processes.
• During photosynthesis, NADP+ captures H+ and electrons, which reduces it to NADPH + H+.
• Cellular respiration follows a similar cycle, reducing NAD+ to NADH + H+.

Photosynthesis Equations

• Photosynthesis involves displacing electrons and is considered an oxidoreduction reaction.
• It captures energy by reducing carbon dioxide and oxidizing water
• A coenzyme for this system would be NADP+/ NADPH,H+

Pigments

• Grana is the process that fuels photosynthesis with energy
• Functional units of photosynthesis, are the site of chlorophylls, carotenoids, and other pigment molecules that are required for ATP synthesis.

Photosynthesis

• The goal of photosynthesis and cellular respiration is to produce ATP
• Cellular respiration oxidizes the food molecules, releasing chemical energy in the process
• The ATP generated from the cycle then fuels cellular activities and molecular motion

Photosystem: Cyclic and Noncyclic Photophosphorylation

• Photosystems contain a light-harvesting complex.
• It also has a reaction center complex.
• The light-harvesting complex comprises many pigments to harvest
• A reaction system then directs that energy to the center and then drives photosynthesis

Enzyme Regulation

• Metabolic regulation involves controlling enzyme activity.
• Feedback inhibition is where an end product inhibits an enzyme in the pathway.

Enzyme Inhibitors

• Enzyme inhibitors can be competitive, binding site, or non-competitive, altering the enzyme's shape.

ATP Function

• ATP drives cellular transport.
• ATP is then converted to cellular material
• Hydrolysis releases energy, fueling cellular processes; this process regenerates ATP by adding phosphate back to ADP.
• ATP is also required by molecular motors to facilitate directional movement within the cytoplasm and cellular respiration.
• This process will then feed back to the electron process

ATP Synthesis

• ATP is formed from oxidized nutrients linked to ADP and a phosphate group en route to forming ATP.

Oxidoreduction Reminder

• Oxidoreduction involves the transfer of electrons between molecules.
• One substance is always reduced by the other.

Equation of Photosynthesis

• Photosynthèse occurs through the process of oxidoreduction.
• This means that water oxidation and carbon dioxide reduction is performed
• The proton motive force creates ATP production by coupling the proton gradient between the thylakoid lumen and the stroma during photosynthetic redox reactions.

Chlorophylle

• The chlorophylls absorb light for photosystem function
• It contains a hydrophobic tail and other components for the production of ATP

Chlorophyll and Light

• Chlorophyll a absorbs blue and red light, while chlorophyll b absorbs other wavelenghts within the color spectrum
• Each variation of the molecule absorbs varying lengths depending on their properties
• Engelmans experiment demonstrates the efficiency for light during photosynthesis

Engelmann's Experiment

• Employing filamentous algae, Engelmann's work revealed photosynthesis's effectiveness is linked to wavelengths.
• He observed aerobic bacteria clustered around algae areas exposed to red and blue light, marking those areas efficiency
• Engelmans experiment is a standard measurement of photosynthesis

Investigating Light

• To investigate photosynthesis a method for light filtration must be performed

Light

• Various light filters allow scientist to measure the rate and process of the molecules during the stage.
• This is due to the interaction of the light
• The spectrophotometer log all information, resulting in a detailed report

Pigment Concentration

• Chlorophyll pigment is degraded and synthesized throughout the life cycle of most vegetation.
• There are three degradation and synthesis cycles within plants
• The rate of chlorophyll production determines the final color outcome

Stages of Metabolism

• The two stages of metabolism is the production of ATP in light reactions
• This will start phase 2 of using that energy

Metabolism Cycle Stage 1

• Light-dependent reactions occur in the thylakoids.

Metabolism Cycle Stage 2

• The Calvin cycle has carbon fixation and organic production in the stroma.

Photosystems in Photosynthesis

• Photosystems are in the thylakoid membranes and associate with proteins to form photosystems I and II.
• Each photosysem is present in extremely high numbers
• The P680 and P700 dictate what the range for light is for the final process

Two Parts of Photosynthesis

• Complex light is harvested by molecules such as chlorophyll
• That energy can then be used in the central reaction to facilitate the process to the next stage

Light

• The correct use and wavelenghts of light facilitate the process of photosynthesis

Electron Transit

• Non-cyclic electron movement is caused by the action of chlorophyll, and other molecules to harness the reaction to its conclusion.
• This cycle is also required because it releases stored light waves to be stored into protons

Noncyclic Electron Transport

• Light initiates the transport of electrons from H2O to NADP+.
• ATP and NADPH are formed during reactions.

ATP Sources

• I'ATP contributes molecular energy
• ATP uses light in the correct portions to power the process of photosynthesis

Calvin Cycle

• A cyclic cycle, using a variety of substances to produce oxygen
• Used in conjunction with P680 and P700, the cycle harvests light for energy
• It then produces NADPH and H+ to store the extra light

Overview

• The most important thing about the calvin cycle its its capability to determine the rate of process of carbon intake and light intake

The two Processes

• Cyclic transit of electrons to facilitate the other functions throughout the spectrum

Cyclical Transportation

• It can be used for the Calvin cycle and many other process
• All of these are essential for the production of light in different portions

Cyclic Transfer of Electrons

• Photosystem 1 harvest more oxygen
• This is done to help produce the high amounts of ATP

Electron Movement

• ATP can be transferred or returned depending on the gradient

Photosynthesis, and Molecules

• Chlorophyll, and other particles must be kept in good nutritional order to facilitate reactions properly