Plant Physiology: Enzymes

Proteins make up of total dry weight

30%

Major function of proteins

Serve as enzymes. (Some are RNA)

Enzymes

Biological catalysts that greatly increase the rate of biochemical reactions

How are enzymes usually named

Named after their substrate and adding a “-ase” to the end

Catalyst

A substance that speeds up a chemical reaction WITHOUT BEING A REACTENT

Activation rate

The amount of energy that must be put in for the reaction to begin

fill the blank spots

How many diff amino acid side chains are found in nature

20

Conformation

3D arrangement of the atoms in the molecule

A change in conformation involves a breaking of the covalent bonds

False, does not involve

Denaturation involves the loss of the uniqe 3D shape leading to a loss of catalytic activity

True

Protein structure

• Primary structure

• Secondary Structure

• Tertiary Structure

• Quaternary Structure

Primary protein structure

The sequence of amino acid (a.a) residues

Secondary protein structure

The regular, local structural units, held together by HYDROGEN bonds

Tertiary protein structure

Final 3D structure of polypeptide

Quaternary protein structure

The association of 2 or more separate 3D polypeptides (subunits) to form complexes

Domains

The several independently folding units of the proteins large single polypeptide chain.

What is the region where subunits bind to when aiding with the catalytic reaction?

Active site of enzymes

Where is the active site located ?

At the interface between 2 domain

Factors that can affect/control enzyme activity

• Temperature

• pH

• Regulatory molecules

• Cofactors

• Compartmentalization

• Feedback inhibition

High temp = Low reaction rates (T/F)

False

Increasing or decreasing the temp outside the tolerable range affects the chemical bonds in the active site

True

Active site amino acids (a.a)residue have acidic or basic properties that are important for catalysis

True.

How does a change in pH affect the residues?

Make it hard for the substrates to bind

Regulatory molecules

Other molecules that regulate the enzymes by either increasing or reducing their activity

Activators

Molecules at increase the activity of an enzyme

Inhibitor

Molecules that reduce the activity of and enzyme

An activator or inhibitor binding is reversible

True, it doesn’t attach permanently

Inhibitor groups and their way

1. Competitive

   • Bind to an enzyme and block the substrate from binding

     • decreasing the reaction rate but can still reach max reaction rate with enough substrate

2. Noncompetitive

   • Doesn’t block the activation site

     • It attaches to another site that prevents the enzyme from doing its job

     • Will never reach max reaction rate even with al of substrate

Allosteric regulation

Regulatory molecule that binds to an enzyme al the allosteric site.

Can be an activator or inhibitor

Allosteric enzymes typically have few active sites located on different protein subunits

False, they have multiple active sites on diff protein subunits

Allosteric inhibitor

when bound to the allosteric site, all active sites on the protein subunits are changed to work less well

Allosteric activator

when bound to an enzyme, they cause an increase of the active sites function

Cofactors

Helper non-protein molecules that HAVE TO attach to enzymes that don’t function properly.

Cofactors attach permanently through strong covalent bonds

False, they can also attach temporarily through ionic or hydrogen bonds

Coenzymes

Organic molecule subsets of cofactores

what is the most common source of coenzymes?

Vitamins such as C for several enzymes that build protein collagen.

Enzymes are often compartmentalized

True, they are found in specific parts of the cell

Why are enzymes compartmentalised?

1. Find their intended substrates readily

2. Don’t damage the cell

3. Have the perfect microenvironment to work well

Explain the picture