L1. Introduction to Metabolism Flashcards
LO
- Appreciate how metabolism is made up of many interconnected biochemical reactions
- Revise how enzymes catalyse chemical reactions
- Understand some common ways in which enzymes (and metabolic pathways) are regulated
- Appreciate the role played by the hydrogen/electron carriers in catabolism
- Recall the basic chemistry of carbohydrates, lipids and proteins
- Understand the separate stages of fuel oxidation, electron transport and ATP synthesis
Catabolism Vs Anabolism
Catabolism:
- Breakdown larger molecules into smaller ones
- Release H+ and e- for the ETC
- Sometimes directly making ATP
Anabolism:
- Build larger molecules from smaller ones
- Usually requires energy (ATP) or reducing power (NADPH and NADH)
Enzymes
- Lower the required activation energy
- Does NOT force reaction and push it to the RHS.
ATP/ ADP/ AMP
- Used as energy
- Reactions that require free energy can couple to ATP hydrolysis to make them thermodynamically favourable
- Cells regulate their energy states in the relative catabolic and anabolic rates
- When ATP is used it is renewed quickly
- If AMP is used, energy levels are generally critically low
Kinase
Enzyme that catalyse a phosphorylation reaction
- Adds a phosphate group
Phosphatase
Enzyme that catalyse dephosphorylation reactions
- Take a phosphate group off
Phosphorylase
Enzyme that catalyses a phosphorolysis reaction
- Uses a phosphate group to break things apart
Synthase
catalyse condensation reactions in which no nucleotide triphosphate is required
- NO ATP required
Synthetase
Enzyme that catalyses condensation reactions that require a nucleotide triphosphate
- Requires ATP
Dehydrogenase
Enzyme that catalyses oxidation-reduction reactions
- Usually involve NAD+/ FAD as cofactors
NADH & FADH2
NAD+ / NADH:
- 1x H+ & e-
FAD / FADH2:
- 2x H+ & e-
Coenzyme A
- Carrier for acetyl groups
- Great for trapping metabolites within a cell
- Large and full of charges, cannot freely diffuse across plasma membrane
Strategy of Fuel Oxidation: Stage 1
- Rip H/e- out of fuels
- Fuels break up into 2-Carbon chunks (acetate)
[heft]
Strategy of Fuel Oxidation: Stage 2
- Rip H/e- out of acetate
- Complete oxidation of carbon atoms to CO2
- Created lots of CO2 and H/e-
[heft]
Strategy of Fuel Oxidation: Stage 3
- Carriers release H/e- to the ETC to pump protons out of the mitochondria towards the cytoplasm to create a H+ gradient.
H/e- carriers and strippers
NAD:
Loves to oxidise:
-CH2-CHOH-
- Reduces to NADH
FAD:
Loves to oxidise:
-CH2-CH2- into -CH=CH-
- Reduces into FADH2
Making ATP with H+ Gradient
- The protons flow under pressure through a channel in the inner membrane (High to low gradient)
- Each H+ ion flowing through the channel allows the conversion of ADP into ATP
- The ATP then entres the cytoplasm
- Coupling (as ATP is being used it is being created)
The 7 Big Concepts
- The H/e- carriers are in short supply
- ADP is in short supply
- ATP is very stable
- Inner membrane is impermiable to protons
- Protons only flow into matrix if ATP is being made
- Proton pumps do NOT work if proton gradient is very high
- No proton pump = no H/e- moving down ETC.
Fuels: Fatty Acids
- Nearly all the carbon atoms are fully reduces in the chain
- Stored as triglycerides in adipose tissue
- Totally hydrophobic
- Very energy dense
- Huge stores (many Kg)
- Brain CANNOT use
Beta Oxidation
- FA trapped in cytoplasm as Fatty Acyl-CoA
- Transported into mitochondria
- H/e- are ripped out by NAD+/ FAD
- FA part loses an acetyl chunk
Fuels: Glucose
- Stored as glycogen
- Hydrophilic
- Inefficient
- Low stores
- Used by all tissues
- Brain has obligatory requirement
Glucose Oxidation
- Glycolysis
- All tissues
- NO oxygen required
- Very fast and inefficient
- Pyruvate must be transported into mitochondria for full oxidation
Fuels: Proteins
- Many pathways of amino acid catabolism
- Does not burn as energy unless really needed to (last resort)
- Very inefficient
Integration of catabolism
[heft]
