chapter 8 notes
DESCRIPTION
Chapter 8 notes. An Introduction to Metabolism. Concept 8.1. Metabolism : the totality of an organism’s chemical reactions A metabolic pathway begins with a specific molecule and is altered into a product - each step is catalyzed by an enzyme. Concept 8.1. - PowerPoint PPT PresentationTRANSCRIPT
Chapter 8 notesAn Introduction to
Metabolism
Concept 8.1Metabolism: the totality of an
organism’s chemical reactionsA metabolic pathway begins with a
specific molecule and is altered into a product- each step is catalyzed by an enzyme
Concept 8.1Catabolic pathway: release energy
in the breaking down of complex molecules into simpler compounds- ex. glucose CO2 + H2O
Anabolic pathway: consume energy to build complicated molecules from simpler ones- ex. amino acids proteins
Concept 8.1Energy: the capacity to do work
Reactions are either exergonic (energy outward) or endergonic
(energy inward)
Concept 8.2Exergonic reactions proceed with a
net release of energy - occur spontaneously
Endergonic reactions absorb free energy from their surroundings- nonspontaneous
Concept 8.2
Concept 8.2Cells do three kinds of work:
- mechanical work (ex. contraction of a muscle cell)- transport work (ex. pumping of substances across a memebrance)- chemical work (ex. synthesis of polymers from monomers)
Concept 8.3Energy coupling: the use of an
exergonic process to drive an endergonic one.
ATP (adenosine triphosphate) is the energy source used in most reactions.- contains a ribose (sugar), adenine (base), and 3 phosphate molecules
Concept 8.3
Concept 8.3Energy is released from ATP when the
terminal phosphate bond is brokenATP ADP + Pi + Energy- work is accomplished by phosphorylation- the transferring of the Pi to another
molecule (ex. channel protein)
Concept 8.3ATP is regenerated in the cell by
phosphorylating ADP through an exergonic reaction in the cell
- in a muscle cell 10 million ATP
are consumed and regenerated per second per cell
Concept 8.3
Concept 8.4Spontaneous reactions may occur at
veryslow rates- sucrose glucose + fructose- if an enzyme is added, the same
reaction can be completed in seconds .
Catalyst : a chemical agent that speeds up reaction w/out being consumed
Concept 8.4Enzyme : a biological catalyst
Activation energy , the energy needed to begin a reaction, prevents many reactions from occurring quickly
Heat is used to speed up reactions because it increases the speed of reactant molecules (they collide more often).
Concept 8.4In biological systems heat alone would
not work- too much heat denatures proteins and kills cells
An enzyme (catalyst) lowers the amount of activation energy needed- enzymes are very selective
Concept 8.4
Concept 8.4The reactant an enzyme binds to is
called the substrate- binds to the active site of the enzyme- the enzyme converts the substrate to product- the product is released
Enzyme animation
Concept 8.4Up to a point, the rate of an
enzymatic reaction will increase with temperature- eventually it will drop because of thermal agitation and protein denaturing
Concept 8.4Most human enzymes function best at 35 - 40 oC.- some bacteria that live in hot springs
have proteins that work best at 70 oC.
Most human enzymes also work best at 6-8 pH .
- pepsin in the stomach work best at pH of 2.
Concept 8.4
Concept 8.4Certain chemicals can selectively
inhibit the activity of specific enzymes
Competitive inhibitors: reduce enzyme activity by blocking the substrate from binding to the active site- can be overcome by increasing the substrate
Concept 8.4Noncompetitive inhibitors: impede
the reaction by attaching to another part of the enzyme, thus changing its shape- ex. toxins and poisons