Cellular Respiration and Photosynthesis Flashcards

Flashcards covering cellular respiration and photosynthesis, generated from lecture notes.

Cellular Respiration

The breakdown of complex molecules to release energy in the form of ATP.

3 Main Types of Catabolic Pathways

Aerobic respiration, anaerobic respiration, and fermentation.

Overall Equation for Aerobic Respiration of Glucose

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy (ATP + heat).

Oxidation and Reduction in Cellular Respiration

Glucose is oxidized and O2 is reduced.

NAD+

A coenzyme that accepts 2 electrons and 1 proton, forming NADH — an electron carrier.

4 Main Stages of Aerobic Cellular Respiration

1. Glycolysis 2. Pyruvate oxidation 3. Citric acid (Krebs) cycle 4. Oxidative Phosphorylation (ETC + Chemiosmosis)

Glycolysis

Cytosol; converts 1 glucose into 2 pyruvate, 2 net ATP, and 2 NADH.

Pyruvate Oxidation

Mitochondria; converts 2 pyruvate into 2 Acetyl CoA, 2 CO2, and 2 NADH.

Products Formed in Citric Acid (Krebs) Cycle Per Glucose

2 ATP, 6 NADH, 2 FADH2, 4 CO2.

Location of the ETC in Eukaryotic Cells

Inner mitochondrial membrane (cristae).

Chemiosmosis

H+ flow through ATP synthase, driving production of ATP from ADP.

Final Electron Acceptor in Aerobic Respiration

Oxygen (forming water).

Difference Between Anaerobic Respiration and Fermentation

Anaerobic uses an ETC with non-O2 electron acceptor; fermentation directly converts pyruvate to products.

The process that converts solar energy into chemical energy in chloroplasts.

Photosynthesis

They produce organic molecules from CO₂ and other compounds — nearly all plants, algae, and cyanobacteria.

Photoautotrophs

Organisms that consume organic material from photoautotrophs; includes humans and decomposers.

Heterotrophs

6 CO₂ + 6 H₂O + Light energy → C₶H₁₂O₶ + 6 O₂

Simplified Overall Equation for Photosynthesis

Inside mesophyll cells in chloroplasts.

Where Photosynthesis primarily takes place

Chlorophyll a

The main green pigment in chloroplasts

Chlorophyll reflects green light and absorbs blue-violet and red.

Why Leaves Appear Green

Accessory pigments that absorb excess light and provide photo-protection.

Carotenoids

A light-capture complex composed of chlorophyll and proteins.

Photosystem

Pair of specialized chlorophyll a molecules plus a primary electron acceptor.

Reaction Center

PSII (P680) first, then PSI (P700).

The two photosystems

Thylakoid membrane of chloroplasts.

Light Reactions

Oxygen, ATP, and NADPH.

Products of Light Reactions

Linear electron flow.

Main Path of Electron Flow in Light Reactions

Electrons from PSI cycle back to produce additional ATP without making NADPH.

Cyclic Electron Flow

It converts O₂ instead of CO₂, consuming energy and reducing sugar output.

Why Photorespiration is Wasteful

PEP carboxylase fixes CO₂ into a 4-carbon compound first.

How C4 Plants Avoid Photorespiration

They take in CO₂ at night and release it during the day.

How CAM Plants Minimize Water-Loss

Inside the stroma of chloroplasts.

Calvin Cycle

1. Carbon fixation, 2. Reduction, 3. Regeneration of RuBP

3 Phases of the Calvin Cycle

3

CO₂ Molecules required to Produce 1 G3P

9 ATP and 6 NADPH.

Energy consumed to produce 1 G3P

They minimize photorespiration under low CO₂ and water stress.

Advantage of C₄ and CAM Mechanisms

To produce energy (ATP and NADPH) for the Calvin Cycle.

Main Role of the Light Reactions

Thylakoids provide membrane for light reactions; stroma is site of Calvin Cycle.

Importance of Chloroplast Structure

It likely arose when Earth's atmosphere had less oxygen and more CO₂.

Photorespiration as an 'Evolutionary Relic'

Organelles in plant cells where photosynthesis occurs.

Chloroplasts

Fluid in chloroplasts where the Calvin Cycle occurs.

Main Role of the Stroma

Disk-shaped structures within chloroplasts that contain chlorophyll.

Thylakoids

Stacks of thylakoids.

Grana

The range of all types of electromagnetic radiation, including visible light.

Electromagnetic Spectrum

Each has a unique structure that interacts with specific light energies.

Why Different Pigments Absorb Different Wavelengths

A graph that shows which pigments absorb which wavelengths of light.

Absorption Spectrum

A graph that shows the rate of photosynthesis at different light wavelengths.

Action Spectrum

It directly converts light energy into chemical energy.

Why Chlorophyll a is the Main Photosynthetic Pigment

They absorb additional light and transfer energy to chlorophyll a.

Role of Accessory Pigments

Chlorophyll breaks down, allowing other pigments to become visible.

Why Leaves Change Color in the Fall

Between PSII and PSI in the light reactions.

Location of the Two Electron Transport Chains

The process of adding a phosphate to ADP to form ATP using light energy.

Photophosphorylation

Model depicting flow of electrons from water to PSII to PSI and then to NADP+.

Z-Scheme

To provide electrons and release oxygen as a byproduct.

Why Water is Split During Light Reactions

Ribulose bisphosphate; the molecule that CO₂ attaches to in the Calvin Cycle.

RuBP

Rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase).

Enzyme that Catalyzes Carbon Fixation

It does not require light directly, although it depends on products of light reactions.

Why the Calvin Cycle is Called 'Dark Reactions'

Glyceraldehyde-3-phosphate, a 3-carbon sugar produced in the Calvin Cycle.

G3P

3 turns.

Turns of the Calvin Cycle to Produce 1 Molecule of G3P

To minimize photorespiration under stress conditions (like dryness).

Why C₄ and CAM Plants use Different Mechanisms

C₄ and CAM plants; it fixes CO₂ efficiently under low CO₂ conditions.

Where PEP Carboxylase is Used

To concentrate CO₂ in specialized cells and reduce photorespiration.

Why C₄ Plants Separate Carbon Fixation and the Calvin Cycle

To avoid water-loss by keeping stomata closed during the day.

Why CAM Plants Perform Carbon Fixation at Night