AP bio Unit 3 bruh

How are cellular processes powered?

Energy released from chemical reactions, mainly through ATP and energy coupling between exergonic and endergonic reactions.

First law of thermodynamics

Energy cannot be created or destroyed, only transferred or transformed.

Second law of thermodynamics

Every energy transfer increases entropy (disorder) in the universe.

How is order (entropy) maintained in a system?

By a constant input of energy that offsets the natural tendency toward disorder.

How are cellular processes powered (ATP focus)?

By exergonic reactions that release energy, often coupled to ATP hydrolysis.

Exergonic reaction

A reaction that releases energy and occurs spontaneously (ΔG < 0).

Endergonic reaction

A reaction that requires energy input and is not spontaneous (ΔG > 0).

Energy coupling

Using energy from exergonic reactions (like ATP hydrolysis) to drive endergonic reactions.

Why is energy coupling needed in cells?

Many essential cellular reactions are endergonic and need energy input.

What happens when energy decreases or order is lost?

Cellular processes fail, homeostasis is lost, and the organism may die.

Metabolic pathway

A series of enzyme-catalyzed reactions where each product becomes the next reactant.

Catabolic vs anabolic pathways

Catabolic pathways break down molecules and release energy; anabolic pathways build molecules and require energy.

Relationship between steps in a metabolic pathway

The product of one step is the reactant of the next.

Effect of decreased tryptophan

Decreased IAA production.

Effect of decreased enzyme Trp-T

Decreased I3PA and IAA production.

Effect of decreased I3PA

Decreased IAA production.

Effect of decreased enzyme YUC

Decreased IAA production.

Effect of decreased IAA

Reduced final product; pathway output decreases.

All organisms perform glycolysis (True/False)

TRUE

Conservation of glycolysis

Occurs in Archaea, Bacteria, and Eukarya, showing it evolved early and is essential.

Why glycolysis evolved early

Does not require oxygen or membrane-bound organelles.

Oxidative phosphorylation in archaea

Occurs across the plasma membrane using an ETC and proton gradient.

Oxidative phosphorylation in bacteria

Occurs across the plasma membrane using an ETC and ATP synthase.

Oxidative phosphorylation in eukaryotes

Occurs in the inner mitochondrial membrane.

Photosynthesis

Using light energy to convert CO₂ and H₂O into sugars, releasing O₂.

Reactants of photosynthesis

CO₂, H₂O, and light energy.

Products of photosynthesis

Glucose and O₂.

Description of photosynthesis

Light reactions produce ATP and NADPH; the Calvin cycle uses them to make sugars.

Photosynthetic organisms

Plants, algae, and cyanobacteria.

First photosynthetic organisms

Prokaryotes (cyanobacteria).

Evidence of atmospheric oxygenation

Banded iron formations.

Origin of eukaryotic photosynthesis

Endosymbiosis produced chloroplasts.

Chloroplast function

Captures light energy to produce sugars.

Stroma

Fluid-filled interior of the chloroplast where the Calvin cycle occurs.

Thylakoid

Membrane sacs containing chlorophyll.

Grana

Stacks of thylakoids.

Thylakoid membrane function

Site of light reactions, ETC, and ATP synthase.

Thylakoid space (lumen)

Region of proton accumulation.

Chlorophyll

A pigment that absorbs light energy.

Location of chlorophyll

Thylakoid membrane.

Light reactions

Light excites electrons, ETC produces ATP and NADPH, and water is split to release O₂.

Calvin cycle

Uses ATP and NADPH to fix CO₂ into sugars.

Connection between light reactions and Calvin cycle

ATP and NADPH from light reactions power carbon fixation.

Electron transport chain (ETC)

A series of proteins that transfer electrons and pump protons.

Location of photosynthetic ETC

Thylakoid membrane.

Linear vs cyclic electron flow

Linear produces ATP, NADPH, and O₂; cyclic produces ATP only.

Photolysis

Splitting of water at photosystem II to replace electrons.

Why photosynthesis stops without photolysis

No electrons means no ETC, ATP, or NADPH.

Chemiosmosis

ATP synthesis driven by proton movement through ATP synthase.

Photophosphorylation

ATP synthesis using light energy.

Cellular respiration

Conversion of glucose into ATP.

Fermentation

ATP production without oxygen.

Stages of cellular respiration

Glycolysis, Krebs cycle, and electron transport chain.

Final electron acceptor in aerobic respiration

Oxygen.

Final electron acceptor in anaerobic respiration

Other molecules such as nitrate.

Location of glycolysis

Cytosol.

Oxygen requirement of glycolysis

Does not require oxygen.

Substrate-level phosphorylation

Direct ATP synthesis from a phosphorylated intermediate.

Location of Krebs cycle

Mitochondrial matrix.

Oxidation

Loss of electrons.

Reduction

Gain of electrons.

Purpose of fermentation

Regenerates NAD⁺ so glycolysis can continue.

Location of fermentation

Cytosol.

Why aerobic respiration is more efficient

Produces much more ATP.