CRF own notes

purpose

LIFE IS WORK:

• All living cells require energy from outside sources

• The work of the cell included:

  • Assembling polymers: making carbs, protein, nucleic acids

• An eukaryotic cell reproducing is either mitosis or meiosis (cell splitting)

  • Mitosis is a type of cell division resulting in two genetically identical daughter cells, maintaining the original cell's chromosome number.

  • Meiosis: a specialized form of cell division that produces four genetically diverse daughter cells, each with half the chromosome number of the original cell, and is essential for sexual reproduction.

• Energy flows into the ecosystem as sunlight and leaves as heat

• Photosynthesis generates O2 and organic molecules that are used in cellular respiration.

• Cells use chemical energy stores in organic molecules to generate ATP (cellular energy), which powers work.

Energy Requirements in Cells

• All cells require energy for vital functions

• Forms of cellular work:

  • Assembling polymers (carbohydrates, proteins, nucleic acids)

  • Transporting molecules across membranes (facilitated diffusion using ATP)

  • Cellular movement (via flagella, cilia)

  • Cellular reproduction (mitosis for eukaryotes, binary fission for bacteria)

Energy Source for Animals

• Animals obtain energy by consuming other organisms (fats, lipids, carbohydrates, proteins)

• Note: Nucleic acids are not a direct source of energy

CHLOROPLAST (PHOTOSYNTHESIS)

• The site of photosynthesis in plants where light energy is converted into chemical energy in glucose.

• Producers (plants with chloroplasts) vs. consumers and decomposers (both with mitochondria)

  • light energy produces the organic molecules (glucose) and releases O2

MITOCHONDRIA (CELLULAR RESPIRATION)

The powerhouse of the cell, responsible for cellular respiration, breaking down glucose to generate ATP in Animals/Humans.

• It takes the organic molecules and O2 to produce ATP; the byproducts are CO2 and H2O. (some ATP lost as heat)

• now serves as the substrates for photosynthesis in plants

• Approximately 66% of the energy from ATP is lost as heat

• Mitochondria convert chemical energy (from organic molecules) to cellular energy (ATP)

PRODUCTS AND SUBSTRATES: cellular respiration and photosynthesis

• Cellular Respiration:

  • Substrates of Cellular Respiration: C6H12O6+ O2

  • Products of Cellular Respiration: CO2 + H2O + ATP.

  • Overall Reaction: C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (ATP ,Heat)

    • The addition of 6s is referred to as balancing the equation, ensuring the equation matches on both ends

• Photosynthesis:

  • Substrates of Photosynthesis: CO2+H2O+ Light ENERGY

  • Products: C6H12O6 + O2

  • Overall Equation: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2

  • feed off of each other (equations are the same but reverse)

Catabolic Pathways:

• Releases stored energy by breaking down complex molecules

  • an exergonic reaction

• electron transfer plays a major role in these pathways

• these processes are central to cellular respiration.

Types of Respiration in Celluar Respiration

• Aerobic Respiration

  • This happens in the presence of oxygen in the mitochondria

  • goes from a six-carbon molecule to a one-carbon molecule

    • Glucose (O6) to Carbon Dioxide (CO2)

  • Consumes organic molecules and 02 and yields ATP

  • oxygen is the final electron acceptor

  • Efficiently produces ATP using mitochondria

  • Yeast undergoes alcohol fermentation in the presence of oxygen

    • Alcohol fermentation in yeast (produces ethanol and CO2)

  • The final electron acceptor is O2

• Anaerobic Respiration

  • Occurs in the absence of oxygen,

  • Breaks a 6-carbon molecule in half, resulting in two 3-carbon molecules

    • the energy in glucose is going to be carried to an inorganic molecule. ei. sulfur and iron (replacing oxygen as the final acceptor)

  • Produces ATP in the mitochondria

  • similar to aerobic but consumes compounds other than O2.

  • Humans can perform lactic acid fermentation without oxygen

    • Lactic acid fermentation in humans (produces lactic acid, leads to muscle burn)

  • the final electron acceptor is an inorganic molecule (ex: sulfur, iron)

REDOX REACTIONS: Oxidation-reduction reactions

• the transfer of electrons during chemical reactions releases energy stores in organic molecules

  • the energy is used to synthesize ATP.

• in oxidation, a substance loses electrons (is oxidized)

• in reduction, the substance gains electrons

• molecules being oxidized are the reducing agents.

  • the electron donor

• molecules being reduced is the oxidizing agent

  • the electron receptor

• During cellular respiration, the fuel (glucose) is oxidized, and O2 is reduced

• organic molecules with an abundance of hydrogen are excellent sources of high-energy electrons

  • when breaking the covalent bonds it produces more energy.

• Energy is realized as electrons associated with hydrogen ions are transferred to oxygen, a lower energy state.

The Carbon Cycle and Energy Flow

• Energy flows into the biosphere from the sun

• Photosynthesis produces oxygen and organic molecules, which are used in cellular respiration

• Oxygenic photosynthesis generates oxygen as a by-product

Energy Harvesting in Absence of Oxygen

• Only glycolysis functions under anaerobic conditions

• Produces small amounts of ATP, leading to fermentation processes

• Energy released pumps protons (H+) into the intermembrane space, creating a gradient

Role of NAD+ and FAD+

• Electron carriers (NAD+ → NADH, FAD → FADH2)

• Essential for transporting electrons to the electron transport chain

• Balancing Chemical Equations: Ensure reactants equal products

4 STEPS OF CELLULAR RESPIRATION

Glycolysis

• Breakdown of glucose (6-carbon) into two pyruvates (3-carbon) (sugar splitting) and ATP

• then generates an electron

• occurs whether or not O₂ is present

• Is a Catabolic Reaction

• Occurs in the Cytoplasm, with two major phases:

  1. Energy investment phase - the amount of energy required to break glucose bonds

     • uses 2 ATP to produce 4 ADP +2 P

  2. Energy payoff phase - the stage where ATP is generated and the high-energy electrons are transferred to electron carriers.

     • uses the 4 ADP + 4 P to produce 4 ATP (gross amount)

     • Produces 2 ATP (net gain) and 2 NADH

• Substrates: Glucose and ATP

• Products: 2 Pyruvate, 2 NADH, 2 ATP and H₂O

• the products are going to serve as substrates for pyruvate oxidation and the electron transport chain.

• Glycolysis during aerobic respitation.

Pyruvate Oxidation: removing electrons from pyruvate

• in the presence of O2, pyruvate enters a mitochondrial (in eukaryotic cells) where the oxidation of glucose is completed

• CO2 is released (releasing 1 carbon from three-carbon chain that is pyruvate) leaving a 2 carbon chain (acety CoA)

• Converts pyruvate to acetyl CoA before entering the Krebs cycle

• occurs within the mitochondria

• Substrates: Pyruvate and Coenzyme A

• Products: CO2, NADH, Acetyl CoA

• The products will serve as substrates for the citric cycle and the electron transport chain.

• Afterward, the citric acid cycle completes the energy-yielding oxidation of organic molecules

Krebs Cycle (Citric Acid Cycle): generates more elctron carriers

It takes place in mitochondria

• Krebs cycle has eight steps and three phases:

  1. Citreatee Formation: the acetyl group of acetyl CoA ( 2 carbons) joins the cycle by combining with oxaloacetate (4 carbons), forming citrate (6 carbons).

  2. Oxidation: the following seven steps decompose the citrate (breaking bonds, releasing energy) back to oxaloacetate, making the process a cycle

  3. Regeneration of Oxaloacetate: the NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain.

• Converts acetyl CoA to carbon compounds, generating NADH, FADH₂, ATP, and CO₂

• completes the breakdown of pyruvate to CO2

• oxygen is the final electron acceptor

• substrates: Acetyl CoA

• products: ATP, CO2,NADH and FADH2

  • FADH2 is only produced in the Krebs cycle.

• the products serve as a substrate in the electron transport chain.

Oxidative Phosphorylation:

• Takes place in the electron transport chain (in the mitochondria), producing the majority of ATP (90% of ATP)

• Chemiosmosis couples electron transport to ATP synthesis

  • after glycolysis and Krebs cycle, NADH and FADH2 account for most of the energy extracted from food.

• These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis

Substrate Level Phosphorylation:

• Occurs in glycolysis and Krebs cycle, producing less ATP (2)

• A molecule with a phosphate transports the phosphate group to a molecule without a phosphate group, and so on, transferring energy.

• the enzyme responsible for adding a phosphate group is called kinase.

• the enzyme responsible for removing a phosphate group is phosphatases

ELECTRON TRANSPORT CHAIN/ CHEMOSMOSIS

• where the majority of ATP is produced.

• is in the inner membrane (cristate) of the mitochondrion

• electrons drop free energy as they pass down the chain of proteins and are finally passed to O2, forming H2O

• electron carriers alternate between reduced and oxidized states as they accept and donate electrons.

  • gaining an electron, they’re being reduced

  • when giving an electron away, they’re oxidized

PROTIENS OF THE ELECTRON TRANSPORT CHAIN:

• Complex 1 - NADH dehydrogenase

• Complex 2 - succinate dehydrogenase

• Q Enzyme - ubiquinone

• Complex 3 - cytochrome bc1 complex

• Cytochrome C

• Complex 4 - cytochrome c oxidase

  • Complexes 1, 2, and 4 pump Hydrogen protons out of the matrix into the intermembrane space.

THE MATRIX:

• The matrix is where the citric acid cycle occurs, providing substrates for the electron transport chain.

• hydrogen protons have a charge, therefore, cannot go through the phospholipid bilayer. the hydrophobic tails do not want to interact with charges.

  • requires another protein(binds) to get to the matrix

    • any molecule that requires a protein to get across the membrane is called facilitated diffusion.

    • pumps the hydrogen proton through ATP Synthase into the matrix via facilitated diffusion.

ATP SYNTHASE:

• where ATP is generated

• 90% of the cellular energy from aerobic respiration is produced

  • intermembrane has a greater concentration of hydrogen protons

  • mitochondrial matrix has a lesser concentration of hydrogen protons

• as a hydrogen proton enters, its turns the ATP synthase

  • known as mechanical energy.

  • building more and more potential energy

• the hydrogen proton is released back into the mitochondrial matrix.

  • energy has to be released from the built of energy

  • goes to ADP (inorganic phosphate) to produce ATP (building bonds)

  • this is known as Chemosmosis

• a chemical that allows hydrogen protons to move back into the matrix affects ATP synthase because it sends fewer molecules of hydrogen, which causes reduced production of ATP, ultimately impacting the energy supply for cellular processes.

• about 34% of the energy of glucose molecules is transferred into ATP during cellular respiration, making about 32 ATP.

  • the rest is lost as heat

• Fermentation and aerobic respiration enable cells to produce ATP without oxygen

• most cellular respiration depends on electromagnetic oxygen to pull electrons down the electron transport chain.

• When removing oxygen, the only stage in cellular respiration that will occur is Glycolysis.

• without oxygen, the electron transport chain will cease to operate.

  • in this case, glycolysis couples with anaerobic respiration for fermentation to produce ATP.

    • only produces a 2 carbon molecule

    • the 3 carbon pyruvate is going to lose CO2

      • the process is called Decarboxylation

    • which forms the two-carbon molecule Aceraldehyde

FERMENTATION:

• Fermentation consists of glycolysis plus the reactions that regenerate NAD+, which can be reused by glycolysis.

• Fermentation still allows ATP production but a lot less.

  • relys on substrate level

• two common types

  • Alcohol Fermentation (yeasts):

    • pyruvates is converted to ethanol in two steps:

    • Releases CO2 from pyruvate

    • produces NAD+ and ethonal

    • yeasts have a protein that we do not have

    • the DNA that will produce RNA to produce protei

  • Lactic Acid Fermentation (animals/fungi/bacteria):

    • pyruvate is reduced by NADH, forming NAD+ and lactate as end products with no release of CO2

    • lactic acid formation by some fungi and bacteria is used to make cheese and yogurt

    • human muscle cells use lactic acid fermentation to generate ARP during strenuous exercise when O2 is scarce.

    • we don’t have the DNA that will produce RNA to produce protein.

ELECTRON CARRIERS

Electron Carriers: molecules on the cell that transport electrons from one molecule (protein) to the next

• In Aerobic respiration, the electron carriers are NADH and FADH2

• electrons are transferred through protein complexes (NADH, FADH2) in the mitochondrial membrane

• ex NAD+ is an electron carrier that functions as an oxidizing agent

each NADH (reduced from NAD+, so it receives 2 electrons and one hydrogen proton.) represents stored energy that is turned into synthesizing ATP.