Proteins and Enzymes Biozone

What makes each of the amino acids in proteins unique?

The R group

What is the primary structure of a protein?

The sequence of amino acids in the polypeptide chain

What determines the primary structure?

The order of nucleotides in DNA and mRNA

How do the swquence and composition of amino acids in a protein influence how a protein folds up?

The differences between amino acids are due to the different properties of the R group. These cause different kinds of intermolecular bonding between amino acids in the polypeptide chain, which influences the way the polypeptide will fold up.

What type of bond joins neighbouring amino acids together?

a peptide bond

How is this bond formed?

By condensation reaction

How are di- and polypeptides formed?

By condensation reactions

Explain the importance of the amino acid sequence in protein folding.

The sequence of amino acids (primary structure) determines how the protein will fold. The distribution of attractive and repulsive charges on the amino acids determines how the protein is organized and folded. (and therefore also determines its biological

Why do channel protein often fold with non-polar R groups to the channel's exterior and polar R groups to its interior?

The interior of a plasma membrane is hydrophobic. Channel proteins span the membrane, and fold in such way that the non-polar R groups allign to the outside and polar (hydrophilic) R-groups from a channel on the inside. This channel allows water soluble m

Why does denaturation often result in the loss of protein functionality?

Denaturation is the process of protein losing its shape. The loss of shape disrupts the protein's active site and thus its ability to carry out its biological functions.

How are proteins involved in the structural tissues of the body?

Proteins form and important component of connective tissues and epidermal structures, cell membranes (regulatory role) and in DNA packing

In catalysing metabolic reactions?

Enzymes are involved in almost all metabolic reactions. Examples include Rubisco (photosynthesis), lipase (fat digestion) pyruvate dehydrogenase (cellular respiration)

How does the shape of a fibrous protein relate to tis functional role?

Their tertiary structure produces long fivres or sheets, with many cross-linkages. This makes them very tough physically and ideal as structural molecules.

How does the shape of a catalytic protein relato to its functional role?

Their 3� structure produces a globular shape, which is critical to their interaction with other molecules, e.g. the active site in enzymes.

What is meant by 'active site' ?

THe active site is the region where substrate is drawn in and positioned such such a way as to promote the reaction. The properties of the active site are a function of the precise configuration of the amino acid side chains which interact with the substr

Why do enzymes usually only work on one substrate?

The active site is very specific because of how the protein folds up (its tertiary structure). It will normally accept only one type of molecule (the bustrate, which has the correct configuration to interact with the active site.

How do substrate molecules come into contact with an enzyme's active site?

Substrate molecules must collide with the active site.

Using examples, explain the role of enzymes in metabolic processes

Enzymes are involved in a wide variety of metabolic processes including production of ATP and NADPH in photosynhtesis, the fication of carbon from CO2 in the Calvin cycle, glucose catalysts, and ATP production.

Enzyme concentration graph.

Increased enzyme concentration increases reaction rate.
A cell may vary the amount of enzyme present by manufacturing more (increasin rate of synthesis)

Substrate concentration graph.

An increase in substrate concentration increases reaction rate initially, but the reaction rate plateaus as the amount of substrate continues to increase.
The rate changes (levels off) because after a certain concentration of substrate, the enzymes are sa

Temperature graph

An optimum temperature for an enzyme is the temperature where enzyme activity is maximal.
Most enzymes perform poorly at low temperatures because chemical reactions occur slowly or no at all at low temperatures (enzyme activity will reappear when the temp

Acidity or Alkanity graph

Pepsin - the stomach is an acidic environment which is the ideal pH for pepsin.

Explain why being able to continue to drink milk is beneficial?

Milk is a very good food source(it contains good levels of macronutrients, vitamins and minerals). Being able to drink milk throughout life means all people could benefit from its nutritional value.

How is lactase used to produce lactose-free milk?

The enzyme lactase is immobilised to remove lactose from milk. It does so by binding the lactose and enzymatically hydrolysing it into glucose and galactose.

Why does lactose-free milk often have a slightly sweeter taste than ordinary milk?

One of the products of lactose hydrolysis (glucose) is sweeter than lactose itself. Therefore, lactose free milk tastes sweeter than ordinary milk.

Define enzyme

Enzyme is a protein. It consists of chains of amino acids that have taken on a very specific 3D shape. The shape is complex and very specific. They are catalysts and influence the rates of reactions. They cannot force reactions to occur. It lowers the ene

Define active site

Area on an enzyme that is designed to match a specific molecule known as that enzyme's substrate.

Explain enzyme-substrate specificity

The active site matches the enzyme like a glove and hand or a lock and key. The 3D shape of the site is complex and specific, only one key will fit.

Explain the effects of temperature, pH and substrate concentration on enzyme activity.

1) Temperature - higher temperature makes molecules flow faster (higher kinetic energy) and they collide faster, so the reaction rates go up till they reach a specific point where its fastest (optimal temperature) and then quickly denaturation (permanent

Define denaturation

Denaturation is the change of the shape of the active site of an enzyme which makes it unable to match its substrate and thus disables it to carry out it's biological purpose. It is reversible or irreversible.

Explain the use of lactase in the production of lactose-free milk.

As some people are lactose-intolerant, lactase is immobilized and milk poured over it. That way it breaks down the lactose to glucose and galactose and allow these people to drink it. :P