biol 107

Prokaryotic Cytoskeleton

Simpler, with proteins like MreB (actin-like), FtsZ (tubulin-like), and Crescentin (intermediate filament-like) for shape, division, and structure.

Eukaryotic Cytoskeleton

More complex, with microtubules, actin filaments, and intermediate filaments for shape, movement, intracellular transport, and division.

Key Difference in Prokaryotic Cytoskeleton/

Eukaryotes have a highly organized cytoskeleton with motor proteins (dynein, kinesin, myosin), while prokaryotes have structural proteins with more limited roles.

How Plants & Animals Move Organelles in the Cell (plants)

Use actin filaments + myosin for cytoplasmic streaming (e.g., chloroplast movement). Microtubules help position organelles but play a smaller role in transport.

How Plants & Animals Move Organelles in the Cell (animals)

Use microtubules + motor proteins (kinesin & dynein) for long-distance transport (e.g., moving vesicles, mitochondria). Actin filaments also assist in local movement.

What does Rubisco do?

Catalyzes the first step of the Calvin cycle by fixing CO₂ into an organic molecule.

Where does glycoysis take place?

takes place in the cytoplasm of the cell

What is the purpose of the citric acid cycle?

Extract energy from acetyl-CoA 🔥
✔ Generate electron carriers (NADH & FADH₂) for the electron transport chain ⚡
✔ Produce ATP (or GTP) for cellular energy 💪
✔ Provide intermediates for biosynthesis

How does the first law of thermodynamics affect the cell

🔄 Energy Conversion: Cells transform chemical energy from food (glucose) into ATP.
🔥 Heat Release: Some energy is always lost as heat during metabolism.
⚡ Energy Storage & Use: Energy from ATP powers cellular processes like movement, transport, and biosynthesis.

What is an enzyme

A protein that speeds up chemical reactions by lowering activation energy, without being used up

What does sucrase do

An enzyme that breaks down sucrose (table sugar) into glucose and fructose.

What is the activation engery of a reaction

minimum amount of energy required to start a chemical reaction. It is the energy needed to break bonds in reactants so that new bonds can form in products.

How enzyme help reactants react

help reactants react by lowering the activation energy, making it easier for the reaction to occur.

What is an exergonic reaction

chemical reaction that releases energy, usually in the form of heat or light.

What is an endergonic reaction

chemical reaction that requires an input of energy to proceed, as the products have more energy than the reactants.

CO2 + 2H2X → (CH2O) + H2O + X2

This is a simplified version of the photosynthesis equation, showing carbon dioxide and hydrogen atoms being converted into sugars.

2 H2O + 4 γ + 2 NADP+ + 3 ADP + 3 Pi → O2 + 2 NADPH + 3 ATP

This is the light reaction equation in photosynthesis, where water, light energy, NADP+, and ADP are used to produce oxygen, NADPH, and ATP.

6CO2 + 12H2O → C6H12O6 + 6H2O + 6O2

This is the overall photosynthesis equation, showing how carbon dioxide and water are converted into glucose and oxygen with the help of light energy.

Relevance of Photosynthesis

• Organism: Produces glucose (energy) for plants.

• Ecosystem: Provides energy for the entire food chain.

• Civilization: Supplies oxygen and food for humans and other species.

Light

Visible electromagnetic radiation that powers photosynthesis.

Wavelength & Frequency

Longer wavelength = lower frequency & energy; shorter wavelength = higher frequency & energy.

Pigments

Molecules that absorb light energy (e.g., chlorophyll), used in photosynthesis.

Atmospheric Effects on Light

The atmosphere absorbs and scatters certain wavelengths, allowing only specific parts of the spectrum (like visible light) to reach the surface.

Chloroplast

Organelles in plant cells that contain thylakoids where photosynthesis occurs

Photoelectric Effect

When light hits a molecule, it excites electrons, causing them to move to a higher orbital.

Z-Scheme

A simplified diagram of the electron transport chain, showing the flow of electrons through photosystem II, cytochrome b6f, photosystem I, and NADP+.

Linear Flow

Electrons flow through photosystem II and I, producing ATP and NADPH

Cyclic Flow

Electrons flow only through photosystem I, producing only ATP

ATP Creation

ATP is produced in the thylakoid membrane as protons flow through ATP synthase during electron transport

ATP in the Dark

ATP can be forced in the dark by increasing proton concentration in the thylakoid space.

Coupling of Reactions

Light-dependent reactions produce ATP and NADPH; these products are used in the light-independent (Calvin) cycle

Light-Independent Reactions (Calvin Cycle)

1. Carboxylation: CO2 is fixed onto ribulose 1,5-bisphosphate (RuBP).

2. Reduction: ATP and NADPH reduce 3-phosphoglycerate (PGA) to G3P.

3. Regeneration: RuBP is regenerated from G3P, using ATP.

Rubisco

Enzyme that fixes CO2 in the Calvin cycle.

Ribulose 1,5-bisphosphate

5-carbon molecule that reacts with CO2.

PGA (3-Phosphoglycerate)

Product after CO2 fixation.

1,3-bisphosphoglycerate

Reduced form of PGA.

G3P (Glyceraldehyde 3-phosphate)

Final product used to regenerate RuBP and form glucose.

NADPH

Provides electrons for the Calvin cycle.

ATP Synthase

Enzyme that synthesizes ATP.

Cytochrome b6f

Protein complex in the electron transport chain.

Photosystem I & Il

Light-harvesting complexes involved in electron transport.

Oxygen-evolving complex

Splits water to release oxygen during photosynthesis.

Carboxylation vs. Oxygenation

• Carboxylation: RuBisCO adds CO2 to RuBP, producing PGA (used in the Calvin cycle).

• Oxygenation: RuBisCO adds O2 to RuBP, producing a toxic byproduct (photorespiration), reducing efficiency.