Ch. 10: Intro to Metabolism

what is metabolism

total of all biochemical reactions in the cell (most of which involve enzymes) and is divided intwo 2 parts

what are the two parts of metabolism?

catabolism and anabolism

what does catabolism do

• fueling reactions

• energy-conserving reactions

• provide reducing power

• generate precursors

what does anabolism do

• synthesis of complex organic molecules

  • requires energy

What are two key features of microbial metabolism in terms of nutrition and ecological function?

1. Microbes exist in all five major nutritional types.

2. They cycle essential elements (CHONPS).

example of elemental cycling

nitrogen cycle

• 4 steps are solely done by microbes

• microbes are part of the other four steps

what are the energy units?

• calorie (cal)

• joules (j)

• kilocalorie (kcal) or Calorie, big “C”

calorie

• cal

• energy needed to raise 1 gram of water up 1ºC

joules

• J

• 1 cal of heat = 4.1840 J of work

kilocalorie/Calorie

• kcal/C

• 1000 calories = 1 Calorie or Kilocalorie

• 1 kcal/C is enough energy for a person weighing 70kg to go up 35 steps

what is the unit for standard free energy change

ΔGº’

exergonic reactions

• ΔGº’ is negative

• reaction proceeds spontaneously

endergonic reactions

• ΔGº’ is positive

• reaction will not proceed spontaneously

What are the nucleoside triphosphates involved in metabolism?

ATP, GTP, CTP, UTP

ATP is…

• main energy currency of the cell

• ATP + H₂O → ADP + Pi + H⁺

GTP is involved in…

protein synthesis

CTP is involved in…

lipid synthesis

UTP is involved in…

peptidoglycan synthesis

What does it mean that ATP has a high phosphate transfer potential?

It can donate a phosphoryl group to other molecules, activating them for metabolic reactions

Why can ATP transfer its phosphate group to other molecules?

Because high-energy phosphorylated compounds (like ATP) have a large amount of free energy

What is substrate-level phosphorylation (SLP)?

A metabolic process where a phosphate group is directly transferred from a high-energy compound to ADP, forming ATP.

What is required for biochemical reactions involving phosphate transfer?

Enzymes — they catalyze the reactions

redox reactions are made up of

oxidizing and reducing reactions

which is the oxidized form and which is the reduced form in a conjugate redox pair?

acceptor is oxidized form

donor is reduced form

oxidized form + e- → reduced form

• Oxidized form accepts e-

unit for standard redox potential (E’₀)

volts

is a more negative E₀ a better electron donor or acceptor?

more negative E₀ → better electron donor

more positive E₀ → better electron acceptor

what is the first rule of redox pairs

the reduced member of the pair that is more negative donates electrons to the oxidized member of the pair that is more positive

aka

reduced member: more negative

- donates electrons to -

oxidized member: more positive

what is the second rule of redox pairs

the greater the difference in redox potential (E’0) between the redox pairs that serves as the electron donor and acceptor, the greater amount of energy available (G0) in the oxidation-reduction reaction

direction of reaction if ∆Gº is < 0 and Eº_cell > 0

spontaneous in forward direction

direction of reaction if ∆Gº is > 0 and Eº_cell < 0

spontaneous in reverse direction

direction of reaction if ∆Gº and Eº_cell are both 0

no net reaction: system at equilibrium

comparing 2 redox pairs

n = # of electrons

F = Faraday’s constant

Faraday’s constant

23 kcal/volt or 96.5 kJ/volt

substance being oxidized is…

the electron donor

the reducing agent/reductant

substance being reduced is…

the electron acceptor

the oxidizing agent/oxidant

a negative ∆G or change in free energy means…

the reaction is exergonic

the products have less energy than the reactants

the first electron carrier has…

the most negative E’_º

where is ETC found in eukaryotes

in the mitochondria (cristae) or chloroplast

where is ETC found in prokaryotes

cell membrane

do electrons lose or gain energy whilst moving through the molecule

lose

what is the ETC used in

oxidative phosphorylation

what are the main electron carriers?

• NADH and NADPH

• FAD and FMN

• CoQ/ubiquinone

• cytochromes

• nonheme iron-sulfur proteins

what do NADH and NADPH carry

2 electrons and 1 proton

what do FAD and FMN carry

2 electrons and 2 protons

what are flavoproteins?

Electron carriers that contain FAD or FMN

what is CoQ (ubiquinone) and what does it carry?

lipid-soluble electron carrier that carries 2 electrons and 2 protons

• quinone carries e-

• lipophilic: embedded in membrane

What do cytochromes carry and what group do they contain?

They carry 1 electron at a time and contain iron in a heme group.

What do nonheme iron-sulfur proteins carry and what group do they lack?

they carry 1 electron at a time and do not contain a heme group

• aka ferredoxin

what are the types of biochemical pathway structures

linear, cyclic, branching

what are the components of biochemical pathway structures

How do biochemical pathways interact with each other?

What are dynamic pathways in metabolism?