Bioenergetics: Photosynthesis and Cellular Respiration Key Processes

What are the two main bioenergetic processes discussed?

Photosynthesis and cellular respiration

What is the primary role of photosynthesis?

To convert solar energy into chemical energy within chloroplasts

What type of organisms are autotrophs?

Organisms that produce their own food using sunlight and CO2

What is the general equation for photosynthesis?

Light Energy + CO₂ + Water → Glucose + Oxygen

What is the primary role of cellular respiration?

To produce ATP by breaking down chemical energy from food

What type of organisms are heterotrophs?

Organisms that consume organic material for energy and carbon

What is the general equation for cellular respiration?

Glucose + Oxygen → CO₂ + Water + ATP Energy

How do cellular respiration and photosynthesis relate in terms of redox reactions?

They involve inverse redox reactions

What is the first phase of cellular respiration?

Glycolysis

Where does glycolysis occur?

In the cytosol/cytoplasm

What are the products of glycolysis per glucose molecule?

2 net ATP, 2 NADH, and 2 pyruvate

What occurs during the oxidation of pyruvate?

Each pyruvate is oxidized to form CO₂ and NADH, producing Acetyl-CoA

What is the second phase of cellular respiration?

Citric Acid Cycle (Krebs Cycle)

Where does the Citric Acid Cycle occur?

In the mitochondrial matrix

What are the products of the Citric Acid Cycle per glucose molecule?

4 CO₂, 6 NADH, 2 FADH₂, and 2 ATP

What is the third phase of cellular respiration?

Oxidative Phosphorylation

Where does oxidative phosphorylation take place?

In the inner membrane of the mitochondrion

What is the main purpose of the Electron Transport Chain (ETC)?

To facilitate the flow of electrons and generate ATP

What is the total ATP yield for eukaryotes during cellular respiration?

30 ATP (net)

Where does photosynthesis occur in plants?

In the chloroplasts

What are thylakoids?

Flattened sacs in chloroplasts where light-dependent reactions occur

What is the stroma in chloroplasts?

The fluid outside the thylakoids where the Calvin Cycle occurs

What is the role of stomata in leaves?

To allow gas exchange, accepting CO₂ and expelling oxygen

Why do plants appear green?

Because chlorophyll absorbs all colors of visible light except green

What is the key light-capturing pigment in plants?

Chlorophyll a

What are accessory pigments in plants?

Chlorophyll b and Carotenoids, which absorb energy and pass it to chlorophyll.

What happens when a pigment absorbs a photon of light?

An electron goes from a ground state (low energy) to an unstable excited state (high energy).

Where do light reactions occur in the chloroplast?

In the thylakoid membrane (granum).

What is the goal of the light reactions in photosynthesis?

To oxidize water to oxygen and generate ATP and NADPH for the Calvin Cycle.

What is the first step in linear electron flow during photosynthesis?

Light energy is captured by Photosystem II (PS II, P680) and transferred to the special chlorophyll pair (P680).

What byproduct is released during water splitting in photosynthesis?

Oxygen (O₂)

What is photophosphorylation?

The process of producing ATP as protons diffuse back into the stroma through ATP Synthase.

What happens to electrons in Photosystem I (PS I)?

They are excited by light and passed to NADP+ reductase, reducing NADP+ to NADPH.

What is the purpose of cyclic electron flow?

To generate extra ATP when needed by cycling electrons back to the cytochrome complex.

Where does the Calvin Cycle take place?

In the stroma of the chloroplast.

What is the primary goal of the Calvin Cycle?

To use ATP and NADPH to reduce CO₂ to sugar.

What enzyme is responsible for carbon fixation in the Calvin Cycle?

Rubisco

What is produced during the reduction phase of the Calvin Cycle?

3-carbon sugars (PGAL/G3P) which eventually lead to glucose.

What is the main difference between chloroplasts and mitochondria in terms of ATP synthesis location?

Chloroplasts synthesize ATP in the stroma, while mitochondria synthesize ATP in the matrix.

What is the terminal electron acceptor in aerobic respiration?

Oxygen (O₂)

What is the net ATP yield from aerobic respiration in eukaryotes?

30 ATP

What is the purpose of fermentation?

To use an alternative pathway to reduce pyruvate and replenish the NAD⁺ pool when oxygen is absent.

What type of fermentation occurs in animals?

Lactic Acid Fermentation

What is a wasteful process that occurs under high temperatures or low CO₂ concentration?

Photorespiration

How do C₄ plants reduce photorespiration?

By using an extra step (Hatch-Slack pathway) to pump CO₂ into internal bundle sheath cells.