1.3.1: Enzyme-Substrate Complex

Enzymes

Proteins that act as catalysts, which make reaction happen faster by lowering activation energy (without being changed/used themselves);  special molecules that catalyze biochemical reactions

Lactase and lactose are examples of what?

Examples of Enzymes

Molecule that an enzyme interacts with

substrate

Location where enzymes interact with substrate

enzyme’s active site

Enzyme and substrate fit together like hand in glove forming an ___

Enzyme-substrate complex

2 examples of what enzymes do to substrates

1. break substrates into smaller pieces

2. join substrates together into one molecule

The enzyme's active site is ____ to bind its substrate, forming a temporary enzyme-substrate complex

specifically shaped

The amount of energy needed to make one molecule of glucose from six molecules of carbon dioxide

18 molecules of ATP & 12 molecules of NADPH

metabolic pathway

series of interconnected biochemical reactions that convert a substrate molecule or molecules, step-by-step, through a series of metabolic intermediates, eventually yielding a final product or products.

Anabolic

metabolic building

catabolic

metabolic breaking down

anabolic pathways

require an input of energy to synthesize complex molecules from simples ones

Catabolic pathways

degradation (or breakdown) of complex molecules into simpler ones; Molecular energy stored in the bonds of complex molecules is released in catabolic pathways and harvested in such a way that it can be used to produce ATP.

Types of energy

kinetic energy, potential energy, chemical energy

catalyst

substance that helps a chemical reaction occur

Almost all enzymes are ____

 proteins, made up of chains of amino acids,

How do enzymes lower activation energies of chemical reactions inside a cell?

They bind to reactant molecules, and hold them in such a way as to make the chemical bond-breaking and bond-forming processes take place more readily

denature

process that changes the natural properties of a substance

extreme pH values or temperature can cause enzymes to ___

denature

“lock and key” enzyme-substrate binding model

model that proposes that the enzyme and substrate fit together perfectly in one instantaneous step; not accurate

“induced fit” enzyme-substrate binding model

As the enzyme and substrate come together, their interaction causes a mild shift in the enzyme’s structure that confirms an ideal binding arrangement between the enzyme and the transition state of the substrate. This ideal binding maximizes the enzyme’s ability to catalyze its reaction.

Competitive inhibition

An inhibitor molecule is similar enough to a substrate that it can bind to the active site and simply block the substrate from binding. When this happens, the enzyme is inhibited through ____, ( inhibitor molecule competes with the substrate for active site binding)

non-competitive inhibition

an inhibitor molecule binds to the enzyme in a location other than an allosteric site and still manages to block substrate binding to the active site

Allosteric inhibition

inhibitor molecules bind to enzymes in a location where their binding induces a conformational change that reduces the affinity of the enzyme for its substrate.

Allosteric activation

allosteric activators modify the active site of the enzyme so that the affinity for the substrate increases.

Many enzymes don’t work optimally, or even at all, unless ____

bound to other specific non-protein helper molecules (such as cofactors and coenzymes), either temporarily through ionic or hydrogen bonds or permanently through stronger covalent bonds.

Cofactors

inorganic ions such as iron (Fe++) and magnesium (Mg++).

What is enzyme function regulated by?

in part, regulated by an abundance of various cofactors and coenzymes, which are supplied primarily by the diets of most organisms.

How does the cell respond to the abundance of specific products?

by slowing down production during anabolic or catabolic reactions.

How is the production of amino acids and nucleotides controlled?

controlled through feedback inhibition

ATP is an allosteric regulator of some of the enzymes involved in the catabolic breakdown of sugar, the process that produces ATP. What does this mean?

when ATP is abundant, the cell can prevent its further production. ATP is an unstable molecule that can spontaneously dissociate into ADP ; When relative levels of ADP are high compared to ATP, the cell is triggered to produce more ATP through the catabolism of sugar.