Bio Test 3

Cellular respiration pt1- 2

  • Cellular Respiration

All the metabolic reactions that a cell uses to get energy from organic molecules, while releasing waste; cellular energy

  1. it is an aerobic reaction which means it uses O2

  2. it releases CO2 waste via the oxidation of orgnic molecules

    1. Glucose + Oxygen → Carbon Dioxide + water

    2. C6H12O6 + 6O2 → 6CO2 + 6H2O

      1. Redox reaction

      2. exergonic reaction

  3. Some is lost as heat, but most of that energy will be utilized

    1. ATP

    2. NADH

    3. FADH2

  • Steps in Cellular Respiration

  1. Glycolysis → Pyruvate

    1. releasing free energy as NADH and ATP

  2. Breakdown of pyruvate → Acetyl-CoA (cytosol)

  3. Citric acid cycle (this is in the mitochondria)

    1. this releases CO2, ATP, NADH, FADH2

  4. Electron transfer

    1. oxidative Phosphorylation

    2. produces the most ATP

  • Glycolysis

Glucose (6-C) becomes metabolized to form 2 pyruvate (3-C) molecules in the cytosol, utilizing ATP

this process releases a net energy of 2 ATP and 2 NADH molecules

ATP at this stage is formed by substrate-level phosphorylation, directly transferring a phosphate from a phosphorylated organic molecule to ADP

  • Breakdown of Pyruvate Overview

Two pyruvate molecules formed from glycolysis enter the mitochondrial matrix

once inside, pyruvate is broken down to an acetyle group (2-C) and one CO2

Each o=pyruvate brokken down produces 1 NADH molecule by the reduction of the NAD

  • Citric Acid Cycle Overview

Each acetyl group produced from the breakdown of pyruvate is incorporated into an organic molecule, which is larer oxidized to from 2 CO2 molecules

during the cycle 1 ATP, 3 NAdh and 1 FADH2 molecule is made per acetyl group

since there is 2 acetyl groups one cycle produces 2 atp, 6 nadh, and 2 fadh2 molecules

  • Oxidative Phosphorylation overview (electron transfer)

NADH and FADH2 made in the first 3 steps contain high energy electrons and can be readily transferred into a redox reaction to other molecules

once high energy electrons are removed energy is released and through a =n electron tranport chain energy is used to produce H+ electrchemical gradient

like photsynthesis, chemiosmosis utilizes stored energy in the H+ electrochemical gradient to synthesize ATP

this produces 30-34 atp molecules

  • Glycolysis part 2 (deeper dive)

involves the metabolism of glucose into two pyruvate molecules which can occur in the presence or absence of O2

glycolysis is characterized as a 10-step pathway with different enzymes at each step, a common pathway across bacteria, archaea and eukaryotes

the 10-steps of this pathway can be lumped into 3 phases:

  1. Energy investment phase (1-3)

    1. phosphates from 2 atp molecules attach to glucose, then convert to fructose-1, 6-biphosphate. the phase raises the free energy of glucose allowing future reactions to be exergonic

      1. 1,glucose becomes phosphorylated utilizing ATP, (ATP-ADP)

      2. 2-3, structure rearrangements lead to production of fructose-6-phosphate and further to fructose-1,6-biphosphate

  2. Cleavage phase (4-5)

    1. fructose -1,6-biphosphate is cleaved into 2 glyceraldehyde-3-phospate (G3P) molecules

      1. 4, fructose-1,6-biphosphate cleaves into G3P and dihydroxyacetone phosphate

      2. 5, Dihydroxyacetone is rearranged to form another G3P

  1. energy liberation phase (6-10)

    1. produce 4 ATP, 2 NADPH and 2 pyruvate molecules. since the energy investment phase used 2 ATP, the net yield is 2 ATP molecules

      1. 6-10:

Glucose to a G3P and then G3P through a variety of redox reactions and unstable phosphorylation to becoming 2 pyruvate via 1glucose

  • Regulation of Glycolysis

  1. availability of substrates

  2. the enzyme phsphofruktinase which catalyzes step 3, which is believed to be the rate limiting step

  3. ATP itself can lead to feeback inhibition at high concentrations, binding to phosphofruktinase and inactivating the enzyme

  • Breakdown of Pyruvate

  1. pyruvate is tranported from the cytosol into the mitochondria matrix by a transport protein

  2. once pyruvate is trandported through an outer membrane channel and inner membrane channel (H+ active tranport) into the mitochondria matrix is oxidized or broken down by pyruvate dehydrogenase

  3. CO2 is removed from pyruvate

  4. 2 high energy electrons are removed from pyruvate and transferred to NAD+ with H+ produces NADH

  5. 5. Remaining acetyl is attached to coenzyme coa and organic molecule which produces acetly coa, via covalent bond to sulfur


Cellular Respiration pt 3

  • ATP Synthase

  • ATP production

  1. H+ enters one at a time through a cahnnel in the a subunit and binds to c subunit

  2. An adhacent H+ bound to a c subunit is released and travels through a channel in the a subunit

    1. The binding and releasing of a H+ in the c subunit leads to a clockwise

      rotation. The y and δ subunits rotate with the c subunit as well.

  3. rotation of y changes its contact with the 3 b subunits, causing the b subunit to change their structure

  • Structural Changes of B Subunits

Conformation 1. ADP and P bind with good affinity

Conformation 2: ADP and P bind tightly, strainging bonds to form ATP

conformation 3. ATP binds weakly and is released, cycle is continued

  • Diet and Cellular Respiration

2 main sources of cellular respiration are proteins and fats

variations in diets can lead to dramatic changes in metabolism