Week 3 Introduction To Metabolism Flashcards
Metabolism
The chemical processes that occur in living organisms, resulting in growth, production of energy and elimination of waste
Catabolism
The breakdown of complex molecules, releasing energy or lost as heat
Into a simple molecule
Breaking bonds
Synthesis (anabolism)
Formation of complex molecules from simple starting materials
Metabolic pathways
A sequence of reactions
Reversible reactions
High concentration of A leads to high production of E and vice versa
Pathways
Many pathways can be reversed
Some steps are slower than others, or only occur in one direction (rate limiting steps)
Direction and speed of pathways controlled by enzymes
Gibbs free energy
A measure of available chemical energy
All chemical systems tend naturally towards states of minimum Gibbs free energy
G= H-TS
WHERE
G= Gibbs free energy
H= Enthalpy (heat content)
T= temperature in kelvins
S= entropy (mainly heat loss)
Exergonic and endogonic reactions
Exergonic reactions= spontaneous, energy is released
Endergonic reaction= not spontaneous
Energy is added
Action of enzymes
Exergonic reaction
Endergonic reaction
Action of enzymes
Normal (no enzyme reaction)
Proceeds at a slow rate (if at all) due to prohibitive activation energy threshold
Enzyme catalysed reaction
Reaction proceeds at a significantly faster rate as the activation energy threshold is reduced
Enzymes
Proteins
Catalyse (speed up) reactions in metabolism
Very specific
Act as control points in metabolism
Enzyme action
Action affected by
—substrate concentration
— enzyme activity and concentration
—inhibition
—co-enzymes/ co factors
Have binding sites for
—substrates
—coenzymes
—cofactors
—inhibitors
Enzyme inhibition
Competitive =
Prevents the substrate from binding
Competes for active site
Non-competitive=
does not prevent substrate binding
Alters shape of enzyme
Allosteric enzymes
Usually contain 2 or more subunits
Binding of the substrate alters shape of enzyme
Substrate binding, increases affinity for substrate, hence activity
The binding of the first improves the binding of the next ones
Naming of enzymes
Two parts
First part = substrate
Second part = reaction
Kinase
Add/remove phosphate group
Dehydrogenase
Remove H
Decarboxylase
Add/remove carboxyl group
Isomerase/ mutase
Rearranges (forms isomers)
Transferase
Transfers functional groups
Hydrolase/ lipase
Adds H2O (hydrolysis)
Enzymes in metabolism gatekeepers
Entry point into pathway
Enzymes in metabolism feedback regulation
Enzymes can inhibit other enzymes
Control points
Many pathways have irreversible steps
These are potential control points
Activity of enzyme B and enzyme C1, Help determine direction of the pathway
Enzyme control in metabolism
Substrate concentration
Eg glucose concentration
Feedback inhibition
-concentration of end product
Co-enzymes= eg vitamins
CoFactors= eg trace elements (eg iron)
Hormones= inhibit or increase enzyme activity
Energy
Is needed for
Synthesis of complex molecules
Active transport
—movemt of molecules and ions
Eg across a cell membrane
Mechanical work
- muscle contraction
- cellular movement
Energy why ?
ATP->ADP
2 high energy bonds in ATP one between the phosphates
95g of ATP in muscles
ATP maintained 1-2 mmol/kg
Each ATP molecules is recycled some 1000-1500 times per day
Recycling
Anabolism (synthesis)
Uses ATP
Catabolism
Production of ATP eg from fat, CHO and alcohol
Nutrition and metabolism
Carbohydrates, lipids, alcohol
-broken down or stored for energy
-synthesis of body molecules
Protein (amino acids)
-synthesised of a body molecule
-can be used for energy
Minerals
-act as co-factors
-nervous/muscle action
Vitamins
Act as co enzymes
Act as antioxidants
