Biomolecules

The 4 main components that define the chemical nature of the cell are;•Proteins•Carbohydrates•Lipids•Nucleic Acids

These substances are the building blocks of cells.

Proteins

• Are made of many single units called Amino acids,

• All proteins contains the elements Carbon, Hydrogen, Oxygen and Nitrogen (sometimes Sulfur).

• There are 20 different amino acids.

Protein structure• Amino acids are the monomers of a protein.• A chain of amino acids bonded together is called

a polypeptide (which is a polymer)

• A sequence of DNA bases in a gene will determine the amino acid composition, order and arrangement of a protein.

• This order of amino acids will determine the SHAPE of the protein, which in many cases determines it’s function.

How Proteins are made

Protein Synthesis

1) Transcription: DNA transcript is made, this is called mRNA (Carries the code for a gene), occurs in nucelus

2) mRNA moves to cytoplasm or RER, binds to Ribosome

3) Translation – Ribosome translates mRNA, uses code to build a polypeptide, assisted by tRNA which delivers amino acids

4) Polypeptide folds, twists and turns into it’s 3D shape – a Protein!!

Protein Function

• There are thousands of different types of proteins.

• Each one has a very specific function in your body.

Regulating MovementMembrane proteins (transport/channel proteins) control movement of substances into and out of organelles and into and out of a cell.

Structural proteins

• These proteins help to maintain the physical structure of an organism.

• Link membranes, cytoplasm and nucleus.• Keratin – found in hairs, feathers, nails,

hooves and horns• Collagen – most abundant protein in humans,

found in bones, cartilage, tendons, ligaments, skin, and connective tissue.

Controlling Metabolism

• Many Proteins are Enzymes (Catalysts)• A Catalyst is something that lowers the energy

needed for a reaction to occur (essentially, catalysts speed up the rate of a reaction).

Enzyme Properties

• Enzymes work very rapidly.• Each enzyme is specific to only one kind of

substrate.• Enzymes are not destroyed or altered by a

reaction, they can be used repeatedly.• Enzyme activity is affected by the

environment in which they are in.• Enzymes can be inhibited by other chemicals.

The Lock and Key Theory

An enzyme will act on a specific substrate to break it down or substrates to build them up

Enzyme (B) + Substrate (A)

Enzyme Substrate Complex (C)

Enzyme (D) + Products(E)

Catabolic Reaction

• Catabolic reactions involve the breaking down of a substance

Anabolic Reaction

• Anabolic reactions involve the building up of a substance

Enzymes Catalyze Chemical Reactions

• A chemical reaction occurs when 2 objects in motion collide with each other in the correct orientation and with the required amount of energy.

• They must collide with the required amount of energy and in a a specific orientation.

• They can occur without enzymes, but often very very slowly.

What effect do you think heat would have on the rate of reaction? Why?

Particles in motion.Particles in motion.

At high temperature

At high temperature

At low temperatureAt low temperature

Enzyme

Substrate

BUT, even when temp increases past a point, enzyme activity decreases. Why?

Effect of Heat on Enzyme ActivityAt optimum

temperaturesAt optimum

temperaturesAt low

temperaturesAt low

temperaturesAt above optimum

temperaturesAt above optimum

temperatures

The Effect of Heat on rate of reaction

•As temperature of the environment increases, the enzymes and substrates gain more kinetic energy. This increases movement, which in turn, increases the likelihood of a successful collision occurring, resulting in an increased rate of reaction. The active site becomes more complementary in shape to the substrate as temperature increases to an optimum point.•Conversely, as temperature of the environment decreases, the enzymes and substrates lose kinetic energy. This decreases movement, which in turn, decreases the likelihood of a successful collision occurring, resulting in a decreased rate of reaction. The active site becomes less complementary to the substrate.•At extreme temperatures, although the enzymes and substrates will have high levels of kinetic energy and will be colliding more frequently, denaturation of the enzyme can occur, preventing enzyme activity and therefore reducing the rate of reaction. Denaturation is where the bonds maintaining the 3D shape of the enzyme break, resulting in a return to the primary structure, therefore loss of the active site.

Denaturation

• Protein (and enzymes) are not living, therefore do not die.

• Environmental factors can affect their structure. Change in enzyme structure means inability to function.

• Extremes of pH and temperature can cause denaturation.

DenaturationExtreme temperature or pH

What does this graph tell us?

Optimal temperature for typical human

enzyme

Optimal temperature for typical human

enzyme

Optimal temperature for enzyme of thermophilic

bacteria

Optimal temperature for enzyme of thermophilic

bacteria

TemperatureTemperature

Rate of ReactionRate of

Reaction

Effect of pH on Enzyme Activity

At optimum pHAt optimum pHAt low pHAt low pH At above optimum pH

At above optimum pH

Rate

of

Reac

tion

pH

What effect do you think pH would have on rate of reaction?

•Enzymes have an optimum pH at which they operate. This can vary from one type of enzyme to another.•As the pH changes from the optimum, enzyme activity may decrease as the change in pH may effect the shape of the enzymes, making it less able/likely to bind to a substrate.•The greater the change in pH, the greater the change in the structure of the protein.

What does this graph tell us?

Optimal pH for Pepsin

Optimal pH for Pepsin Optimal pH for TrypsinOptimal pH for Trypsin

Rate of reactionRate of reaction

pHpH

What effect do you think enzyme concentration would have on the rate of reaction? Why?

At high enzyme concentrationsAt high enzyme concentrations

At low enzyme concentrationsAt low enzyme concentrations

Enzyme

Substrate

The Effect of Enzyme Concentration on rate of reaction.

•As enzyme concentration increases, there is a larger number of available enzymes that can catalyze a substrate. The ratio of enzyme to substrate increases.•An increased number of enzymes present results in a higher probability of a successful collision between enzyme and substrate, resulting in an increased rate of reaction.•Conversely, as enzyme concentration decreases, the ratio of enzyme to substrate decreases. There are less available enzymes to catalyze the reaction. This decreases the likelihood of a successful collision occurring, resulting in a decreased rate of reaction.

Enzyme Saturation

• The higher the substrate concentration, the higher the rate of reaction, until enzyme saturation occurs.

• At this point, increasing substrate concentration has no effect on rate of reaction.

What does this graph tell us?

What do you think is happening about here?

What do you think is happening about here?

Why?

• Enzyme saturation limits reaction rates.• Enzyme saturation occurs when the active

sites of all enzymes are occupied.• Essentially, all the enzymes are working at

their peak to metabolize the products.• Adding more substrate

InhibitionInhibition occurs when a chemical prevents an enzyme from catalyzing a reaction.

•Competitive InhibitionA substance that is similar in shape to the normal substrate binds to the active site, blocking the normal substrate from binding and preventing the reaction.

•Allosteric InhibitionA substance binds to a part of the enzyme (not the active site) which causes change to the normal shape of the enzyme and the shape of the active site, so a substrate cannot bind to the active site, preventing the reaction from occurring.

Competitive inhibition

EnzymeEnzyme

InhibitorInhibitor

Allosteric inhibition

EnzymeEnzyme

InhibitorInhibitor

EnzymeEnzyme

Enzyme Inhibition

Allosteric

Question 1) Explain the trend seen in the graph below.

pH

Rate of Reaction

Question 2) Explain the trends seen in the graph below.