AP Biology - Unit 3: Energy Flashcards

Energy

Heterotrophs

• Heterotrophs obtain energy by taking in organic compounds.
• The process is represented by the equation: C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O + ATP
• Mitochondria are key organelles with:
  • Cristae: folded membranes that increase surface area.
  • Endosymbiotic origin: They were once independent cells.

Cellular Respiration Steps

1. Glycolysis:
   • Glucose is broken down into pyruvate, producing ATP.
2. Krebs Cycle:
   • Pyruvate is further broken down.
   • CO2 is released.
   • NADH and FADH are produced.
   • ATP is generated.
3. Electron Transport Chain:
   • Electrons are transferred to create a proton gradient, leading to water formation.
   • Produces ~32 ATP.

Anaerobic Problem

• Lactic acid fermentation occurs when pyruvate is converted to lactate.

6.1 Metabolism

• Metabolism: the total sum of an organism's chemical reactions.
• Metabolic pathways:
  • Catabolic pathways: release energy by breaking down complex molecules (e.g., cellular respiration).
  • Anabolic pathways: consume energy to build complex molecules.

Energy Forms

• Kinetic energy: energy of relative motion.
• Thermal energy: random movement of atoms and molecules (a form of kinetic energy).
• Potential energy: stored energy.
• Chemical energy: potential energy available for release in a chemical reaction.
• Spontaneous processes occur without energy input.

6.2 Free Energy

• Free Energy: the portion of a system's energy available to perform work when temperature and pressure are uniform.
• Formula: \Delta G = \Delta H - T\Delta S
  • \Delta G: change in free energy
  • \Delta H: change in enthalpy (total energy)
  • T: absolute temperature (in Kelvin)
  • \Delta S: change in entropy (disorder)
• \Delta G = G{final} - G{initial}
• Systems move towards equilibrium, the state of maximum stability.
• Metabolic Rate:
  • Systems at equilibrium have a minimum \Delta G and do no work; cells at metabolic equilibrium are dead.
  • Cellular respiration breaks down glucose in a series of steps, where the product of one reaction is the reactant for the next.
  • Waste products are generated.

6.3 ATP for Cells

• ATP powers cellular work:
  • Chemical work: driving non-spontaneous reactions.
  • Transport work: moving substances across membranes.
  • Mechanical work: movement of body structures.

Energy Coupling

• Energy Coupling: using an exergonic process to drive an endergonic one.
• Phosphate bonds of ATP are often referred to as high-energy bonds because their hydrolysis releases energy.

ATP Regeneration

• ATP is renewable through the addition of phosphate to ADP.
• Free energy comes from exergonic breakdown to be consumed.

7.1 Catabolic Pathways by Oxidation

• Fermentation: degradation of sugars without oxygen.
• Aerobic respiration: oxygen is consumed as a reactant along with organic fuel.
• Anaerobic respiration: substances other than oxygen are used.
• Overall equation: organic \ compounds + oxygen \rightarrow carbon \ dioxide + water + energy
• Carbohydrates, fats, and proteins can be processed and consumed as fuel.

Redox Reactions

• Redox reactions: electron transfers in chemical reactions.
  • Oxidation: loss of electrons.
  • Reduction: addition of electrons.
  • Reducing agent: reduces a reactant by donating electrons.
  • Oxidizing agent: accepts electrons.
• Respiration: oxidation of glucose and other food molecules.
  • C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O + ATP
  • Glucose is oxidized, oxygen is reduced.
  • Electrons lose potential energy, and energy is released.
• Hydrogen is a good fuel molecule because its bonds are a source of hilltop electrons.
• Energy is released as electrons move down an energy gradient.

Activation Energy

• Energy released from fuel cannot be immediately harnessed without enzymes.
• Enzymes lower activation energy, preventing uncontrolled combustion.

NADH

• NADH carries high-energy electrons.
• Electron Transport Chain: molecules in the inner mitochondrial membrane facilitate the controlled fall of electrons to oxygen.
  • NADH delivers electrons to the top of the chain (high energy).
  • Oxygen captures electrons at the bottom (low energy).

Electron Transport Chain Details

• Each step is an exergonic reaction of hydrogen with oxygen to form water, releasing energy.
• Cellular respiration uses the ETC to break the fall of electrons into small steps, storing released energy to make ATP.
• Process: Glucose → NADH → ETC → Oxygen
• Oxygen:
  • Final electron acceptor.
  • High affinity for electrons and highly electronegative, facilitating the fall down the energy gradient.

7.2 Glycolysis

• Glycolysis: sugar splitting.
• Phases:
  • Energy investment: cell spends ATP.
  • Energy payoff: ATP is produced through substrate-level phosphorylation.
• Glucose is converted to pyruvate, and NAD+ is reduced to NADH.

7.3 Krebs Cycle

• Pyruvate undergoes enzymatic reactions, releasing CO2 and oxidizing the remaining fragment.
• Products include acetyl CoA, NADH, and FADH2.
• Citric Acid Cycle: oxidizes organic fuel from pyruvate –a metabolic process.
• Energy-rich molecules produced:
  • NADH (from NAD+).
  • FADH2 (from FAD).
  • ATP, produced via oxidative phosphorylation.

7.4 Electron Transport Chain

• Prosthetic groups: non-protein components essential for the catalytic functions of certain enzymes.
• Cytochromes: proteins with iron atoms that accept and donate electrons.
• ETC does not directly make ATP; it eases the fall of electrons from food to oxygen.

Chemiosmosis

• Chemiosmosis: energy stored in a hydrogen gradient is used to drive cellular work (ATP synthesis).
• Osmosis: flow of water across a membrane.

Proton-Motive Force

• Proton-motive force: force promoting movement of protons across membranes.
• Several variables reduce the yield of ATP in the energy cycle.
• Approximately 34% of the potential energy from glucose is transferred to ATP.

Cellular Energetics (AP Bio Unit 3)

• Living systems require constant energy input and exchange of macromolecules.
• Energy is essential in living organisms.
• Life maintains order without violating the second law of thermodynamics.
  • The second law of thermodynamics: energy transformations increase entropy (disorder).
  • Energy input exceeds energy loss for maintaining order and powering cellular processes.
  • Energy-releasing processes couple with energy-requiring processes.
  • Loss of order or energy flow leads to death.
• Two main processes:
  • Photosynthesis.
  • Cellular respiration.
• First law-energy is constant, entropy (inefficient) measure randomness.
• Photosynthesis & cellular respiration. Reusable form of energy spontaneous.

Reactions Types

• Endergonic (endothermic): requires energy input.
• Exergonic (exothermic): releases energy and heat.
• Enzymes lower activation energy, speeding up reactions.

Coupled Reactions

• Reactions are often coupled, with exergonic reactions driving endergonic reactions.
• Example: ATP hydrolysis (exergonic) coupled with ion transport against a concentration gradient (endergonic).
• Absorbs energy, stores outward max amount of work preformed uphill favorable.
• + energy requires energy energetically.
• Downhill lower releases energy.
• ATP mediates coupling and serves as an immediate energy source.

ATP

• ATP – Adenosine Tri-Phosphate
• The energy currency of the cell.
• Phosphate group breakage is favorable (exothermic) and coupled with endergonic reactions.
• ATP is constantly generated via cellular respiration.

ATP Production Overview

• Aerobic vs. anaerobic respiration.
• Glycolysis : cytoplasm, universal process (all cells).
• Krebs Cycle & Electron Transport chain: intermembrane, inner membrane mito, mitochondrial matrix.
• Ethanol fermentation alcohol (yeast) anaerobic.
• Lactic Acid fermentation anaerobic human, bacteria.
• Aerobic Respiration uses O_2 in ETC.
• Anaerobic Respiration uses other molecules, no O_2 in ETC (e.g., sulfate, nitrate, carbon dioxide).

Cellular Respiration

• Cellular respiration captures energy from biological macromolecules via enzyme-catalyzed reactions.
• Factors affecting enzymes affect respiration and photosynthesis rates.
• Energy in glucose: comes from H transfer to O_2, releasing electrons.
• Organic molecules with abundant H make excellent fuels (especially fats).
• Glucose breaks down in a series of steps catalyzed by coenzymes.

Coenzymes

• Coenzymes: electron carriers shuttling high-energy electrons from glucose intermediates to the ETC.
  • NAD+: reduced to NADH, oxidized back to NAD+.
  • FAD+: reduced to FADH2, oxidized back to FAD+.
  • NADP+: photosynthesis electron carrier.
  • Hydrogen = CH1206 +CO2 + H2O and ( It atoms pass through Cycle easily between oxidized areduced states, oxidizing
• Agent is H+ in respiration carry ( photosyn.

Summary of Cellular Respiration

1. Glycolysis:
   • Goal: Oxidation of glucose into 2 pyruvates.
   • Location: Cytoplasm.
2. Transition Reaction:
   • Goal: Convert 2 pyruvates to 2 acetyl CoA.
   • Location: Cytoplasm to mitochondrial matrix.
3. Krebs Cycle (Citric Acid Cycle):
   • Goal: Transfer high energy electrons from sugar intermediates to lots of NADH + FADH2.
   • Location: Mitochondrial matrix.
4. Electron Transport Chain (ETC):
   • Goal: Make lots of ATP using electrons dropped off by coenzymes, used to generate a Hydrogen electrochemical gradient.
   • Location: Innermembrane of mitochondrion (cristae – increase Surface Area for more ATP synthases).

• Aerobic Respiration (w/0)) high energy es Lots of used to make lots of ATP high energy e- accepted by NAD+.
• Acetyle - A & 000 + 0-0-0 - CoHi20o (1->3C, 3->2 C).
• = 2 pyruvates & Or net of 2 + 2 2 ATPs.
• Each acetyl CoA goes thru Krebs once* Lots ! ! + CO z + 1 ATP shuttle cargo channel protein & inorganic reverse of ion pump.

Electron Transport Chain Steps

1. Coenzymes drop off electrons.
2. Electrons are relayed from carrier to carrier.
3. Electron flow is exergonic; released energy pumps H^+ ions from the matrix into the intermembrane space (coupled reaction).
4. H^+ electrochemical gradient is established.
5. O2 is the final electron acceptor, forming water (H2O).
6. Chemiosmotic phosphorylation: H^+ ions flow down their concentration gradient, providing energy for ATP synthase to make ATP.
   • aka oxidative phosphorylation in cellular respiration.
   • Decoupling generates heat for thermoregulation in endotherms.

• Prokaryotes: ETC across prokaryotic plasma membrane.

Electron Transport Chain

• (NADH-ETC molecule (flaroprotein) -> FeS protein -> COQ (hydrophobic , mobile -> cytochromes adding phosphate gp to ADP -> uses E stored in H + to drive cellular work release thru sweat gradient across membrane movement of chemical (H) from tod.

Electron Transport Chain Goal

1. Transport High energy es from food to 02 in a series of steps that release energy in manageable amounts:
   Outer mem. -- e carriers - 1 - innermembrane - echondrion.
   O2 + 2H^+ + 2e^- -> H2O

• Each carrier has a greater final e- acceptor attraction for es greatest attraction for e-s flow of e- is exothermic.

1. Energy (E) that is released is used to pump H + ions (aka proteins) across intermembrane into intermembrane space coupling exothermic flow of es to endothermic pumping of Ht against its concentration gradient.

Fermentation

• Fermentation allows glycolysis to proceed without oxygen, producing organic molecules (alcohol, lactic acid) as waste products.
• Goal: Produce NAD+ to return to glycolysis for ATP production.
• Location: Cytoplasm.

Disadvantage of Fermentation

• Lactic acid is toxic, decreases pH, causes acidosis.
• Doesn’t solve O_2 debt.
• Only 2 ATP produced.
• reduced to aerobic ETC anaerobic direct drop off e- to make lactic acid/ethanol Krebs d returns to glycolysis to keep it going.
• Human, bacteria ethanol lactic acid Or + CO2 (yeast).
• Must have enough NAD+ & regens NAD+ by transferring electrons.

Fermentation

• Anaerobic vs Fermentation
  • Anaerobic Uses ETC, for oxidation.
  • No cellular resp., no ETC used.
• Obligate anaerobes: use sulfate ion as final electron acceptor in the respiratory chain (ETC).
• Alcohol Fermentation: CO2 leaves pyruvate → acetaldehyde (final acceptor) to regenerate NAD+ for glycolysis.
• Lactic acid fermentation: Pyruvate → lactate (final acceptor) with no CO2 release; in humans, ATP production outpaces muscle supply of O2 from blood, enhancing muscle performance.

7.6 Metabolic Pathways

• Foods convert into glucose.
• Deamination: amino groups removed to feed into the Krebs cycle.
• Beta oxidation: breaks down fatty acids.
• Glycolysis & Krebs Cycle function as metabolic interchanges, letting cells convert molecules as needed.

Catabolism of Various Food Molecules

• Lipids, glycogen source makes organic molecules for cell respo source #makes organic molecules for cell respo.

Photosynthesis and Cellular Respiration

• In presence of light.
• Green parts produce organic compounds, CR is oxygen.
• Photosyn. Energy from sugar/Water is split & electrons transported electron transferrer to 02 redox reaction from H2O -> CO2.
• Fall down gradient, down gradient makes sugar.
• H2O = by product, H2O = by H_2O product increases potential energy lowers is potential energy.
• Endergonic need light (photosynthesis).

Photosynthesis

• Photosynthesis captures & stores energy.
• First evolved in prokaryotic organisms support the claim photosynthesis was responsible for oxygenated atmosphere.
• Prokaryotic pathways were the foundation of eukaryotic.
• Chemical energy of glucose comes from.
• Chloroplast absorbs light.
• Thylakoids contain pigments and molecule absorbs certain wavelength of light Absorption Spectra of Pigments.

Pigment Types

1. Chlorophyll a: absorbs red wavelength, directly involved in light reaction!
2. Chlorophyll b
3. Carotenoids yellow, red, orange pigments.

• 6 CO 2 + 6H +8 S CoHizOy + 602 energy of Sun (photon-packet light of ein waves& photosynthetic * leaves are most major site :thylakoid sacs mesophyll and Sacs mesophyll: tissue ininterior cell: Dense cell fluid of membrane -green pigment Dies Dies in cold weather.

Photosystem

• Photosystem (PS) - made of pigment antenna, reaction center, and electron acceptor.
• Solar energy is absorbed and passed from pigment to pigment light it reaches the reaction center chlorophyll a.
• Here electrons become excited and escape to electron acceptor molecule

Photosystem Types

1. Photosystem I (PS I) reaction center has a pair of chlorophyll a called P700
2. Photosystem II (PS II) reaction center has a pair of chlorophyll a called P680:

• outside primary as chlorophyll b + cartenoids antennas accept excited es in reaction center low thylakonens E as chlorophyll b + Cartenoids transfer light E to reaction center are made up of chlorophyll a where can boots E of a pair of es are:

Photosynthesis Overview

• involved in the series coordinated reaction pathways used to capture energy in light to yield ATP and NADPH, which power the production of organic molecules.

Types of reactions

1. Light (Light-dependent) Reaction. Use energy from sun to energize electrons removed from water (this is done by PS pigments). Make ATP and NADPH in electron transport chain (ETC) to drive dark reaction. Light in ETC in dark reaction.
2. Dark Reaction (Light-independent) Reaction - aka Calvin Cycle. Dark Reaction (Light-independent) Reaction - aka Calvin Cycle Takes inorganic CO2 and FIXES it (Carbon Fixation) the to organic sugar to be used in mitochondria for energy.

• Thylakoids in Granan + inorganic - NADP. H20 split -> electrons for ETC CO2 (Calvin Cycle Clark reaction)- Penzyme Rubisco NADP+ & Light reaction Stroma thato reactionbraneS + T and ATP -> CoH ,200 02 organic in storma convert solar energy in thylakoids to of energy carbon compounds. Needs NADHEATP from light reaction to occur occurs.

1.) Light Reaction

• Steps O ⑪ ⑬ picks up high acidic go to facilitated diffusion: Calvin to Cycle: H + H+, H + H+.
  Photosystem Steps. Light and Carbon Fixation.

Light Reaction Steps

1. PS II absorbs solar energy which excites electrons (taken from the splitting of H2O) to high energy state at the reaction center (P680).
2. Excited electrons from P680 are accepted by primary electron acceptor and flow down ETC.
3. Electrons arrive at PS I where solar energy that the electron acceptor is boosted to high.
4. Excited in the energy state at P700.
5. Electrons From Photosyn are used ( along With H endergonic.
6. Return to light + e since from light reaction reaction 75% 1980s with To build Incose molecule, one a 16 cycles.

2.) Dark Reaction (Calvin Cycle or C3 Cycle)

• Stroma