COPY Photosynthesis and Cellular Respiration

Photosynthesis Equation

6CO2 + 6H2O --> C6H12O6 + 6O2

Solar energy is converted into chemical potential energy and stored in the bonds of glucose through carbon fixation

Relationship between 2 Phases of Photosynthesis

Reciprocal relationship

Products of light dependent are the reactants of light independent and vice versa

Oxidation-Reduction (Redox) Rxns

Example of rxn coupling

Requires reduction and oxidation of 2 reactants at the same time

Relied on in both photosynthesis and cellular respiration to shuttle electrons between the endergonic and exergonic parts

Oxidation

Lose/give up e-

Compound gains positive charge

Reduction

Gain/receive e-

Compounds lose positive charge

Electron Carriers (photosynthesis)

Can be both oxidized and reduced

Shuttle high energy e- from light dependent rxns to light independent rxns

The e- can be from the e- that were excited from photons of light

Ex. NADP+/NADPH

NAD+/NADH

FADH/FADH2

Chloroplast Anatomy

Stroma - has enzymes and suitable pH for Calvin Cycle

Double Membrane - evidence for endosymbiosis

Thylakoid - ETC and ATP synthase

Granum - flat membrane stacks --> increase SA:Vol ratio and small internal volumes quickly accumulate ions

Lamella - connects and separates grana (thylakoid stacks)

What rxns occur in the stroma?

Light independent rxns

What rxns occur in the thylakoid membrane?

Light dependent rxns

Thylakoid Membrane

1. Contains photosystem proteins (have chlorophyll)

2. ATP synthase

Chlorophyll

Light absorbing pigment in photosystem proteins

Absorb all wavelengths except for green - green is reflected

Absorbance Spectra

Peaks = absorbed light used for photosynthesis

Valley = reflected light that is seen by eye but not used for photosynthesis

Exclusion Statement

Memorization of the steps in the Calvin cycle, the structure of the molecules, and the names of enzymes (except ATP synthase)

Origin of Photosynthesis

Ancestral prokaryotes were the first to develop photosynthesis

Evolution of photosynthesis introduced oxygen into early Earth's atmosphere

Eukaryotic cells became capable of performing photosynthesis after evolving (endosymbiosis)

Light Dependent Rxns

Thylakoid membrane

3 parts - ETC, photolysis, and chemiosmosis

Inputs - NADP+, ADP, H2O

Outputs - NADPH, ATP, O2

Electron Transport Chain (photosynthesis)

1. Light strikes an e- in chlorophyll in Photosystem II

2. e- is excited to a high energy state

3. High energy e- moves through a series of proteins until it reaches Photosystem I

4. Energy from moving e- is used to actively transport H+ ions from stroma into the lumen --> creating and maintaining an H+ ion gradient across the thylakoid membrane

5. e- is out of energy when it reaches Photosystem I

6. Another photon of light hits and excites the e-

7. e- is captured by NADP+ and H+ to reduce NADP+ into NADPH

8. NADPH is transported to the stroma and used in light-independent rxns

Photolysis

Water is struck by photon of light and broken into O2, H+, and e-

E- --> replenish photosystem II

O2 --> waste product

H+ --> maintain concentration gradient

Chemiosmosis

1. ETC generated a H+ ion gradient across thylakoid membrane

2. H+ ions diffuse through a channel in ATP synthase

3. Energy of diffusion allows ATP synthase to phosphorylate (add phosphate) to ADP to make ATP

4. ATP is transported and used to power light independent rxns

Light Independent Rxns

Aka Calvin Cycle

Stroma

Inputs - CO2, NADPH, and ATP

Outputs - Glucose, NADP+, ADP

Gist of Calvin Cycle

1. NADPH and ATP are oxidized and energy is released

2. The energy is used by enzyme RuBisCo to reduce and fix inorganic carbon from CO2 into an organic form in glucose

3. NADP+ and ADP are regenerated and recycled back to light dependent rxns

Must occur TWICE before 1 glucose molecule is produced

How to Experimentally Measure the Rate of Photosynthesis

Measure the change in concentration of the substrate or product over time

1. Variable to Measure - oxygen production over time; part of photosynthesis - light dependent rxns; lab applications - submerge a plant/photosynthetic organisms in water and measure rate of bubble production and or change in concentration of oxygen over time

2. Variable to Measure - CO2 consumption over time; Part of photosynthesis - light independent rxns; Lab applications - put plant/photosynthetic organism in an enclosed space and measure the change in concentration of CO2 over time

Mitochondrion Anatomy

Inner Membrane - ETC and oxidative phosphorylation

Outer Membrane - linking step (pyruvate oxidation)

Matrix - citric acid cycle

Cristae - highly folded so as to increase SA:Vol ratio

Origins of Aerobic Cellular Respiration

Exact same theory regarding photosynthesis applies to cellular respiration

Early prokaryotes capable of respirating formed a symbiotic relationship with ancient cells

Cellular Respiration

Process that organisms use to turn glucose into ATP

All living organisms utilize respiration

2 types - aerobic and anaerobic

Anaerobic Respiration

Aka fermentation - alcohol fermentation (plants, bacteria, yeast) and lactic acid fermentation (animals)

No oxygen needed

Purpose - breaking down ATP to oxidize NADH to regenerate NAD+ for glycolysis to occur

Aerobic Respiration

Aka respiration

Purpose - generate ATP for use in cellular processes that maintain homeostasis

1. Glycolysis (anaerobic)

2. Pyruvate oxidation (aka linking step)

3. Krebs cycle

4. ETC and Oxidative phosphorylation

Potential chemical energy in the bonds of glucose is converted into usable chemical energy in the bonds between the phosphates in ATP

C6H12O6 + 6O2 --> 6CO2 + 6H2O

Glycolysis

Anaerobic

Cytoplasm

1. Oxidizes glucose into 2 molecules of pyruvate

2. Requires reduction of 2 NAD+ to NADH --> NADH carries high energy e- to later parts of aerobic respiration

3. Needs 2 ATP but makes 4 ATP so net gain is 2 ATP

4. Must occur before any form of respiration can occur bc pyruvate is NEEDED

All living organisms utilize glycolysis, which is a major evidence for common ancestry

Pyruvate Oxidation aka The Linking Step

Pyruvate is converted to acetyl-coA as it is transported from the cytoplasm, across the mitochondrial membranes, and into the matrix

Krebs Cycle

Acetyl-CoA goes through a series of exergonic chemical rxns that reduce NAD+ to NADH and FADH to FADH2

Electron Transport Chain (Cellular Respiration)

Inner mitochondrial membrane

NADH and FADH2 are oxidized releasing e- and energy --> NAD+ and FADH are recycled back into the cell environment

e- move through the ETC, losing energy until they combine with O2 and H+ ions to form water as a waste product

Energy released is used to maintain an H+ ion gradient across the inner mitochondrial membrane

Oxidative Phosphorylation

Coupled with the ETC

Similar to chemiosmosis

1. H+ ions diffuse through ATP synthase from the matrix to the intermembrane space

2. Energy from this diffusion is captured and used to phosphorylate ADP into ATP

3. Generates 32-34 ATP

Oxidative Efficiency

Cells are not 100% efficient at capturing all of the energy released from oxidation of NADH during the ETC

Energy not captured is given off as heat

Homeothermic organisms will decouple the ETC and oxidative phosphorylation to generate more heat and regulate body temp

How to Experimentally Measure the Rate of Aerobic Respiration?

Measure the change in concentration of the substrate or product over time

1. Variable to Measure --> oxygen consumption over time; part of aerobic respiration --> oxidative phosphorylation

2. Variable to Measure --> CO2 production over time; Part of Aerobic Respiration --> glycolysis and the citric acid cycle