Transcript Metabolism
Metabolism
Cell Energetics
Cell do three main kinds of work
Mechanical – move themselves
Transport – move something else
Chemical – convert stuff to other stuff
Work requires energy
Where does the energy come from and how
do cells use it?
Cell Energetics
Energy is ______
Metabolism
2 types of metabolism
Two forms of energy
How do cells use the 2 forms
2 Laws of Thermodynamics
Entropy
2 types of reactions
Cell Energetics
Metabolism = total of all the chemical
reactions taking place in an organism
Metabolism
Anabolism = ‘build up’ processes;
‘consume’ (store) energy by assembling
macromolecules
Photosynthesis
Catabolism = ‘break down’ reactions;
release energy by breaking down (lyse)
molecules
Digestion
Energy
Energy – the ability to do work
Potential = capacity to do work
(move something); due to
position or stored (chemical
energy; glucose, glycogen)
Kinetic = motion
Equilibrium = energy runs out
Kinetic and potential energy
What does the types of energy have to do with biology?
Thermodynamics
1st Law – energy cannot be created nor
destroyed
Energy can be transformed
2nd Law – ‘Law of Entropy’ whenever energy is
transformed, some of it becomes ‘unusable’
Entropy - amount of usable energy decreases
each time it is used
‘Lost’ as heat
Energy is running down, universe is tending
towards disorder
Biological Order and Disorder
Organisms are open systems
Use energy to maintain order and organization
Trade organization for heat (increase entropy in
the environment)
Metabolism: Reactions
Two types of reactions:
Exergonic, endergonic
Exergonic reaction - release of free
energy
Less stable, more work
Fire, respiration
Metabolism: Reactions
Endergonic reaction - energy is
absorbed/stored
Photosynthesis
Chemical Reactions
Equilibrium is
eventually reached
in closed systems
Reduced free energy
No work is done
You’re dead!
What cells do..
Review
What are the 2 forms of energy?
_____ is the ability to do work
Energy is lost in chemical reactions as __
A reaction that stores/absorbs energy is
said to be _____
A reaction that releases energy is _____
The total of all chemical reactions in an
organism is called ____
Coupled Reactions
Living systems use coupled reactions
Endergonic reactions are linked
(coupled) with exergonic reactions
Energy from an exergonic reaction
(respiration) is stored in chemical bonds
Coupled Reactions
ATP – Adenosine triphosphate
Cyclical
Catabolic pathways drive the regeneration
of ATP from ADP and phosphate
Controlled by enzymes
Uses of Energy
Mechanical - moving of
cilia/flagella, muscle,
cytoplasm, chromosomes
(mitosis), mousetrap
Transport - H+ ‘pump’, receptors
Chemical – polymerization
Bioluminescence
• Enzymes control metabolism –
If enzymes are present, reactions
take place, if not, they don’t.
Enzymes speed up reactions by
lowering activation energy
Enzymes
Biological catalysts
Accelerate a reaction without being changed
Proteins (700)
Catabolic or anabolic reactions
Enzymes
All chemical reactions require
activation energy
Activation energy (EA) - the
initial amount of energy needed
to start a chemical reaction
Transition state = reactants have absorbed energy
Have become unstable
Reaction takes place
Enzymes
Some reactions occur
spontaneously due to heat
from the environment (rust)
Cellular T needs to remain
low
Metabolism is too slow at
low T
Starch to glucose
Enzymes used to reduce
activation energy
(metabolism at lower T)
Enzymes
Substrate = substance enzyme acts on
Active site = area on the enzyme where
substrate binds
Verryyy specific
Groove, pocket = 3d shape
Enzymes
Lock and key mechanism
Induced Fit = enzyme may change shape to
allow better reaction on substrate
Factors That Affect Enzyme Activity
Temperature
pH
Inorganic salts –
Disrupt H bonds, ionic bonds, hydrophobic
interactions
Cofactors
Inhibitors
Temperature
and pH affect
enzyme
activity
Cofactors
Cofactors - nonprotein enzyme helpers
Metals – Fe, Zn, Cu
Coenzymes - organic cofactors
Vitamins
Enzymes
Inhibitors = substances that inhibit the
actions of enzymes (2 kinds:)
Competitive inhibitors
Noncompetitive inhibitors
Competitive inhibitors resemble substrate,
block active site
Neurotoxin, Disulfiram
Enzymes
Noncompetitive
inhibitors - causes
enzyme to change
shape
Destroys conformation
(active site)
DDT, nerve gas (DSF)
May be allosteric
regulation
Allosteric Regulation of Enzymes
Allosteric regulation - a protein’s
function at one site is affected by
binding of a regulatory molecule at
another site
Receptor site located away from
the active site (quatenary
structure)
Allosteric site has to be activated,
(may be inhibited)
Allosteric activator
Allosteric inhibitor
Enzymes
Cooperativity - one
substrate molecule can
activate all other subunits
of an enzyme
Induced fit
Only requires a small
concentration of substrate
to activate enzyme
Enzyme Activity Helps Control
Metabolism
A cell’s metabolic pathways must be tightly
regulated
DNA codes for proteins (enzymes)
Amount of enzyme can determine rate of
reaction
Feedback Inhibition - end product of the
pathway inhibits the pathway
Regulation
Metabolic pathways – series of enzymes
creates small steps to a final product
Controlling the enzymes (activity or
production) controls the pathway and
product(s)
Feedback Inhibition
Final product of the
pathway shuts off the
pathway
Feedback inhibition
prevents cells from
wasting resources
“don’t need gas if you
don’t have a car.”
Isoleucine – allosteric
inhibitor