Unit B: Plant Respiration and Metabolic Pathways Lecture 1 & 2

Respiration

Process of energy release from carbon compounds.

Dark Respiration

Energy release in absence of light conditions.

Photorespiration

Process minimizing CO2 loss via RUBISCO activity.

Glycolysis

First step of respiration, occurs in cytoplasm.

Krebs Cycle

Series of reactions generating energy in mitochondria.

Oxidative Phosphorylation

ATP production via electron transport chain.

Respiratory Quotient (RQ)

Ratio of CO2 released to O2 consumed.

Sucrose

Main sugar used in plant respiration processes.

2-Phosphoglycolate

Intermediate formed during photorespiration.

3-Phosphoglycerate

Product of converting 2-Phosphoglycolate in photorespiration.

ATP

Adenosine triphosphate, energy currency of cells.

Carbon Skeletons

Molecules generated for biosynthesis during respiration.

Respiratory Capacity

Maximum rate at which a plant can respire.

Energy Demand

Amount of energy required for plant processes.

Substrate Availability

Presence of organic molecules for respiration.

Oxygen Supply

Availability of O2 affecting respiration rates.

Pyruvate Dehydrogenase

Enzyme decreasing activity in light conditions.

Basal RQ Rate

Expected RQ value around 1 for plants.

Phosphoglycolates

Compounds formed when CO2 is limited.

Electron Transfer

Process required for ATP generation in respiration.

Environmental Conditions

Factors influencing respiration rates in plants.

Energy Storage

Transient storage of energy in ATP during respiration.

RQ Value of 1.0

Indicates complete oxidation of substrates.

Oxidized Substrates

Increase RQ due to more CO2 release.

Reduced Substrates

Decrease RQ due to more O2 required.

Aerobic Respiration

Process using O2 to convert substrates into energy.

Oleic Acid Respiration

Produces RQ of 0.7 during oxidation.

Sucrose Respiration

Produces RQ of 1.0 during oxidation.

Carboxylation Reactions

Consume CO2, decreasing the RQ value.

De-carboxylation Reactions

Release CO2, increasing the RQ value.

Fermentation

Produces CO2 without O2, increasing RQ.

Nitrate Influence on RQ

More nitrates lead to increased CO2 and RQ.

Malate Utilization

Increases RQ when oxidized in roots.

Glycolysis

Breakdown of glucose to produce energy.

Krebs Cycle

Citric acid cycle in mitochondrion matrix.

Oxidative Phosphorylation

Uses proton gradient in inner mitochondrial membrane.

Pentose Phosphate Pathway

Pathway for glucose metabolism in plastids.

Invertase Pathway

Converts sucrose to fructose-6-P using ATP.

Energy-Conserving Phase

Produces ATP and NADH from G3P to pyruvate.

Substrate-Level Phosphorylation

Direct ATP production during metabolic pathways.

ATP Cost in Glycolysis

Up to 3 ATPs used to form G3P.

Alternative End Product

PEP can convert to malate in plants.

NADH Production

Occurs during energy-conserving phase of glycolysis.

Respiration

Biochemical process converting nutrients into energy.

Glycolysis

First step in glucose metabolism, producing pyruvate.

Krebs Cycle

Cyclic series of reactions producing NADH and FADH2.

Oxidative Phosphorylation

ATP production via electron transport chain and chemiosmosis.

Pyruvate Dehydrogenase

Enzyme converting pyruvate to Acetyl-CoA.

Fermentation

Anaerobic process generating energy without oxygen.

Pentose Phosphate Pathway

Pathway generating NADPH and ribose-5-phosphate.

ΔG0′

Standard Gibbs free energy change; -5,760 kJ/mol sucrose.

ATP Production

60 ATP generated per sucrose molecule during respiration.

NADH

Electron carrier produced in glycolysis and Krebs cycle.

FADH2

Electron carrier produced in Krebs cycle.

CO2 Release

Carbon dioxide produced during Krebs cycle per pyruvate.

Complex I

NADH dehydrogenase transferring electrons to ubiquinone.

Complex II

Succinate dehydrogenase oxidizing succinate, no protons pumped.

Complex III

Cytochrome bc1 complex oxidizing ubiquinone, pumping protons.

Complex IV

Cytochrome c oxidase, terminal oxidase in electron transport.

Complex V

ATP synthase generating ATP from proton gradient.

Uncoupling Protein

Protein reducing ATP synthesis by dissipating proton gradient.

Alternative Oxidase

Plant-specific enzyme bypassing Complexes I and II.

Electron Transport Chain

Series of complexes transferring electrons to produce ATP.

Energy Loss

48% of energy lost as heat during respiration.

Mitochondrial Matrix

Site of Krebs cycle and pyruvate conversion.

Intermembrane Space

Region where protons are pumped during oxidative phosphorylation.

Acetyl-CoA

Key substrate entering the Krebs cycle from pyruvate.