Unit 1.4 Proteins Flashcards
Structural proteins
Proteins with the amino acid chains arranged as long parallel fibres bonded together, which are used for building cell structures.
eg. collagen, keratin
Globular proteins
The chains of amino acids are coiled into 3D ball shapes.
The precise shape is essential for the correct functioning of the protein, as it allows them to bind with specific molecules.
Globular proteins include enzymes, receptors and antibodies.
Enzymes
Globular proteins that act as biological catalysts in living cells, speeding up chemical reactions and allowing them to happen at low temperatures.
Enzyme properties
They are made of protein.
They are specific to one substrate (due to the shape of the active site) and only catalyse one reaction.
They take part in reactions, but are unchanged at the end and can be re-used.
Active site
The site on an enzyme’s surface where the substrate binds.
It is complementary to the substrate (an exact match), which makes enzymes specific.
Substrate
The substance that an enzyme works on.
It turns into a product.
Lock and key
The substrate is an exact match for the active site, and fits into it like a key fitting into a lock.
When the substrate enters the active site an enzyme-substrate complex is formed.
Product
Produced from the substrate as a result of an enzyme catalysed reaction.
Degradation reaction
An enzyme catalysed breakdown reaction.
eg. starch is broken down to maltose by amylase, hydrogen peroxide to water and oxygen by catalase.
Synthesis reaction
Large molecules are made by joining smaller ones together.
The reaction is catalysed by an enzyme. eg. protein synthesis, glucose-1-phosphate to starch (using the enzyme phosphorylase).
Factors affecting enzyme action
Temperature and pH.
Extremes of temperature or pH cause the shape of the enzyme to change as the bonding is disrupted, and the enzyme becomes denatured, reducing reaction rate.
Optimum temperature/pH
Describes the conditions in which the fastest rate of enzyme action is observed, as the enzyme is most active.
Denature
The shape of the enzyme changes due to high temperatures or extremes of pH.
This alters the shape of the active site, the substrate cannot fit in and the enzyme is said to be denatured.
The rate of reaction decreases.
Collision theory
Explains why the rate of a reaction increases with increasing temperature.
Particles have more energy, move faster and are more likely to collide and react.
