topics 1 2 3 4 unit 3

AP Bio

metabolism

metabolism

all of the chemical reactions in an organism

Metabolic pathways

series of chemical reactions that either build complex molecules or break down complex molecules

Catabolic Pathways

release energy by breaking down complex molecules into simpler compounds

Anabolic Pathways

consume energy to build complicated molecules from simpler compounds

Loss in energy flow

results in death

Kinetic energy

energy associated with motion

thermal energy

energy associated with the movement of atoms or molecules

potential energy

stored energy

chemical energy

potential energy available for release in a chemical reaction

Thermodynamics

The study of energy transformations in matter

1st law of thermodynamics

energy cannot be created or destroyed, only transformed

2nd law of thermodynamics

Every energy transfer or transformation increases the entropy of the universe.

Exergonic reactions

reactions that release energy

I.e. Cellular respiration

Endergonic reactions

reactions that absorb energy

I.e. Photosynthesis

Cells are

never at equilibrium

Mechanical work

movement (i.e. beating cilia, movement of chromosomes, contraction of muscle cells)

Transport work

pumping substances across membranes against spontaneous movement

Chemical work of ATP

synthesis of molecules (ie building polymers from monomers)

Adenosine triphosphate

molecule that organisms use as a source of energy to perform work

Phosphorylation

the released phosphate moves to another molecule to give energy

Enzymes

macromolecules that catalyze (speed up) reactions by lowering the activation energy

The enzyme acts on a

reactant called a substrate

Active site

area for substrate to bind

Active site

area for substrate to bind

Substrates are held in active site by

weak interactions

Induced fit

enzymes will change the shape of their active site to allow the substrate to bind better

Enzymes help

build and break down complex molecules

Optimal conditions

the conditions (temperature and pH) that allow enzymes to function optimally (at their best)

The rate of enzyme activity increases with

temperature (due to collision)

Cofactors

non protein molecules that assist enzyme function

Inorganic cofactors consist of

metals

Holoenzyme

an enzyme with the cofactor attached

Coenzymes

Organic cofactors

Enzyme inhibitors

reduce the activity of specific enzymes

Permanent inhibitors

binds with covalent bonds

Example: toxins and poisons

Reversible inhibitors

binds with weak interactions

Competitive inhibitors:

reduce enzyme activity by blocking substrates from binding to the active site

Noncompetitive inhibitors:

bind to an area other than the active site (allosteric site), which changes the shape of the active site, preventing substrates from binding

Cells regulate metabolic pathways by

controlling when & where enzymes are active, Switch genes that code for enzymes on or off

Allosteric regulation:

molecules bind (noncovalent interactions) to an allosteric site which changes the shape and function of the active site

Allosteric activator:

substrate binds to allosteric site and stabilizes the shape of the enzyme so that the active sites remain open

Allosteric inhibitor:

substrate binds to allosteric site and stabilizes the enzyme shape so that the active sites are closed (inactive form)

Cooperativity:

substrate binds to one active site (on an enzyme with more than one active site) which stabilizes the active form