Mr. Mirani's Science Blog

Other Metabolites & Control of Respiration

Glycolysis accepts a wide range of carbohydrates.

• Glucose is formed from polysaccharides through hydrolysis
• Other 6C sugars are modified to form glucose as well

Proteins

• Proteins are formed from amino acids through hydrolysis
• The amino group is excreted as waste
• The 2C skeleton enters glycolysis or Krebs cycle at different stages

Fats

• Hydrolysis forms glycerol and fatty acids from fats
• 3C glyercol enters glycolysis as G3P
• 2C fatty acids enter Krebs cycle as acetyl CoA

Carbohydrates vs. Fats

• Fats generate 2x more ATP than carbohydrates
• More carbon in each gram of fat = more energy releasing bonds
• The larger amount of oxygen in carbohydrates means it releases less energy because it is already partly oxidized

Metabolism

• Coordination of chemical processes in the organism
  • Regulating enzymes use feedback mechanisms
• Digestion
  • Catabolism when organism needs energy
  • Energy extracted from every source
• Synthesis
  • Energy is used to link pathways
  • Run pathways backwards (build fat)

Central Role of Acetyl CoA

• Central to energy production and biomolecule synthesis
• Builds ATP of fat depending on the need

Control of Respiration: Feedback Control
Feedback Inhibition

• Regulates production
  • No unnecessary products accumulate
  • Production is self-limiting
  • Final product acts as inhibitor for the first enzyme (allosteric inhibitor)

Respond to Cell’s Needs

• Phosphofructokinase
  • Allosteric regulation of enzyme
  • Cannot turn back at this step

A Metabolic Economy

• Metabolic economy is based on supply and demand
  • Raw materials and products must be balanced
  • These molecules become feedback regulators
• Synthesis must be balanced with energy and raw materials available

Cellular Respiration: Harvesting Chemical Energy

Energy is stored in organic molecules, which are consumed by heterotrophs as food. They digest food for raw materials for synthesis and energy through a series of step-by-step enzyme-controlled reactions. The formula for cellular respiration is: 

glucose + oxygen –> energy + water + carbon dioxide

C₆H₁₂O₆ + 6O₂ –> ATP + 6H₂O + 6CO₂ + heat

Heterotrophs harvest energy from organic molecules by digesting them into smaller molecules. The energy is then stored in another bond, released as heat or harvested to make ATP. In living systems, electrons move as part of H⁺ atom. REDOX reactions release energy as they breakdown organic molecules. For example: breaking down C-C bonds, strip off electrons from C-H bonds by removing H atoms (C₆H₁₂O₆ –> CO₂ = the fuel has been oxidized), electrons attracted to more electronegative atoms (O₂ –> H₂O = oxygen has been reduced). Then, a couple REDOX reactions use the released energy (electrons) to synthesize ATP. 

C₆H₁₂O₆ + 6O₂ –> 6CO₂ + 6H₂O + ATP

OXIDATION                 REDUCTION

LEO the lion says GER

Lose Electrons (Oxidation) [says] Gain Electrons (Reduction)

Electron carriers in cellular respiration move electrons by shuttling H atoms around (e.g. NAD⁺ –> NADH (reduced), FAD_⁺² –> FADH₂ (reduced))

Overall there are 4 stages of cellular respiration:

Anaerobic respiration
1. Glycolysis
-respiration without O₂

Aerobic respiration
-respiration using O2
-in mitochondria

2. Pyruvate oxidation
3. Krebs cycle
4. Electron transport chain

To make ATP, we use the ATP synthase enzyme which allows H⁺ to flow through it. This enzyme changes ADP to make ATP through bonding P_i. ATP synthase enzyme then sets up a H⁺ gradient that allows the H⁺ to flow down concentration gradient through ATP synthase. 

ADP + P_i –> ATP

But… how is the proton (H⁺) gradient formed?

too bad that's part 2 pzpzpz!

-FRAZEEEE + roylan + grace

• Glyceraldehyde-3-P

  • finish product of Calvin cycle

  • 3 carbon sugar

  • “C3 photosynthesis”

• G3P important

  • G3P → glucose → carbohydrates →

    lipids (phospholipids, fats, waves) → amino acids → proteins → nucleic acids → DNA, RNA

• RubisCo

  • enzyme

    • fixes carbon from air

      • ribulose bisphosphate carboxylase

      • most important & abundant enzyme

      • air → into LIFE!

• Photosynthesis summary

  • Light reactions

    • produces: ATP & NADPH

    • produces: O2 as byproduct

    • consumes: H2O

• Calvin cycle

  • consumes: CO2

  • produces: G3P (sugar)

  • regenerates: ADP & NADP