Chapter 5 Microbial Metabolism

Metabolism

sum of all chemical reactions within an organism

Catabolism

release energy, breakdown of compounds

Anabolism

require energy, build molecules

Enzymes

Catalyze reactions, speedup/enable chemical reactions

• Bring substrates together in a specific orientation so electrons can interact

• Affects the energy required for a reaction

End in “ase”

Activation energy

amount of free energy required to start a reaction

Active site

where the substrates binds to the enzyme, and where catalysis occurs

“lock and key mechanism”

Induced fit

Change in enzyme shape resulting in tight fit of enzyme and substrate

Substrates bind to the enzyme’s active site using Hydrogen bonds or interactions with enzyme’s R groups

Cofactors

metal ions

Coenzymes

small organic molecules

Enzymes effected external conditions

Temperature

• affects enzyme movement and substrate energy

pH

• Can change amino acid charges in active site

Substrate concentration

• more substrate=faster reaction, until all enzymes are full

Competitive inhibition

a molecule similar to the substrate binds to the active site, blocking the site

Allosteric regulation

a molecule binds to a site other than the active site and changes the enzyme shape so that the active site is no longer available

Feedback inhibition

process where we take the final product and use that product as a allosteric inhibitor to turn off enzyme number 1

Reduction-oxidation reactions (REDOX reactions)

Gain or loss of electrons

Atom that loses electron: Oxidized

Atom that gains electrons: Reduced

NADH

electron carrier

donates electrons to other molecules

Potential energy

energy stored in a molecule that can be used

To make ATP

glucose must be directly consumed

fats and carbs have to be converted back to glucose

Substrate

P is transferred from phosphorylated compound to ADP

a phosphate from molecule is transferred from ADP to make ATP

Oxidative phosphorylation

Electrons are transferred from compounds and passed along electron carriers to Oxygen

Electron transport chain

Transfer of electrons releases energy

Photophosphorylation

Photosynthetic cells

Light energy to ATP

Aerobic respiration

Depends on Oxygen as the electron acceptor

Anaerobic

electron acceptors other than Oxygen (less atp)

Cellular Respiration

glucose to make energy

a suite of reactions that produces ATP in an electron transport chain

4 steps of cellular respiration

1. Glycolysis: Glucose → 2 ATP + 2 NADH + 2 Pyruvate

2. Pyruvate processing: 2 pyruvate → 2CO₂ + 2NADH + 2Acetyl CoA

3. Citric Acid cycle: 2 Acetyl CoA → 6 NADH + 2 FADH 2 + 2ATP + 4CO₂

4. Electron transport and chemiosmosis: 10 NADH + 2 FADH₂ → 34 ATP

Glycolysis

First Step

10 reactions in the cytosol

Glucose → 2ATP +2NADH + 2 Pyruvate

Enzyme catalyzes transfer of phosphate group to form ATP

Made through Substrate Level Phosphorylation

Pyruvate processing

Second step

2 pyruvate → 2CO₂ + 2NADH + 2 Acetyl CoA

Turns pyruvate to Acetyl CoA

Citric Acid Cycle

Third Step

8 carboxylic acids: Contain COOH group

AKA: Krebs cycle or tricarboxylic acid (TCA)

2 acetyl CoA → 6 NADH + 2 FADH2 + 2ATP + 4CO₂

Mitochondria in eukaryotes, cytoplasm in prokaryotes

Electron transport chain (ETC)

NADH and FADH₂ deliver electrons to ETC

Electrons are passed from one protein to another in the chain

Protons Being pumped down to the powerhouses (mitochondria, plasma membrane)

Drives ATP production

10 NADH + 2 FADH₂→ 34 ATP

Carbon Source

Autotrophs: use CO₂

• make their own food, “self feeders”

Heterotrophs: use organic matter

• “different feeder”, obtain sugars and macromolecules from other organisms

Energy source

Phototrophs: use light

Chemotrophs: use redox reactions

Photoheterotrophs

Light for energy and organic compounds for carbon

Chemoautotrophs

use inorganic compounds for energy and CO₂ for carbon

Chemoheterotrophs

Organic compounds for energy and carbon; electrons from H atoms in compounds for energy

Photoautotrophs

light for energy and CO₂ for carbon

Calvin Cycle

Fixation: RuBP → phosphoglycerate

Reduction: 3-phosphoglycerate → G3P(6)

Regeneration

• 1G3P→ Glucose

• 5 G3P → regeneration of RuBP

Produces sugar from CO₂