HARD vers. - biology - enzymes revision for exam
Vocabulary for Enzymes:
\ Enzymes:
Enzymes are protein molecules that control all metabolic reactions in living cells. Enzymes act as biological catalysts, controlling the rate of each step of the complex chemical reactions that take place in cells.
Enzymes are known as catalysts of chemical reactions as they allow reactions to speed up and take place with less energy.
\ Catalysts:
Catalysts are chemical substances that can accelerate/speed up chemical reactions and can be reused many times
\ Atoms and molecules:
Atoms and molecules are in constant motion and colliding and they are the substances that bind to enzymes
\ Reactants:
Reactants are the starting materials that bind with the enzymes to form a chemical reaction
\ Products:
Products are the ending materials that the enzyme releases after the chemical reaction occurs
\ Metabolism:
Metabolism is the sum of all chemical reactions occurring within a living organism
\ Activation energy:
Activation energy is the amount of energy required for the reaction to begin
\ Chemical reaction:
Chemical reaction is a chemical change that occurs when two or more substances combine to form a new substance
\ Bond-breaking:
Bond-breaking is when a chemical reaction takes place at the active site where the more complex molecule (substrate) is broken down into two simpler forms (products)
\ Bond-forming:
Bond-forming is when the two less complex molecules are metabolised into a more complex molecule
\ Amino acids:
Amino acids are molecules that combine to form proteins.
Enzymes are proteins comprised of amino acids linked together in one or more polypeptide chains. The sequence of amino acids in a polypeptide chain is called the primary structure. This structure determines the three-dimensional structure of the enzyme, including the active site. Enzymes are composed of protein molecules that create its particular ‘chemical’ shape.
\ Active site:
The active site is the surface of the enzyme with a specific shape. In a chemical reaction, the reactants, also known as substrates, temporarily bind to the active site of the enzyme.
\ Substrates:
Substrates are the molecules that enzymes react with to create a chemical reaction. Enzymes catalyse chemical reactions involving substrates. The substrate binds with the enzyme and is formed into one or more products which is then released from the active site.
\ Substrate-enzyme complex:
Substrate-enzyme complex is what is created once the substrate binds to the enzyme
\ Lock-and-key model:
Lock-and-key model is that the active site is rigid and the small substrate molecule is reciprocally shaped and fits exactly into the active site, like a key in a lock.
\ Induced-fit model:
Induced-fit model is the binding of a substrate to the active site of an enzyme, causing it to alter its shape slightly, to fit more tightly around the substrate.
\ Complex molecule (substrate):
Complex molecule could be two or more molecules together and is a bigger molecule that may need to be broken down into smaller molecules which end up being the products after the chemical reaction takes place in the active site of an enzyme.
\ Simpler forms of molecules (products):
Simpler forms of molecules may need to be bonded into one bigger molecule after the chemical reaction takes place, where the amino acids in the active site bind the two small molecules together.
\ Intracellular:
Intracellular is inside the cell
\ Extracellular:
Extracellular is outside the cell
\ Optimal temperature:
Optimal temperature is the temperature that is most suitable for an enzyme to function properly.
\ Temperature increase:
Temperatures can rise up and may exceed the optimal temperatures for enzymes.
\ Rate of reaction increase:
The rate of reaction can increase as the temperature increases but once it hits its optimal temperature and starts to go over, then the enzyme will begin to denature.
\ Denature:
Denature happens to an enzyme when the temperature reaches above the optimal temperature, and becomes too hot for it. The excessive heat causes the enzyme to change shape and size, destroying it until it is no longer functional anymore. Therefore it is not able to bind to substrates because of its denatured form.
\ Excessive heat - irreversible:
Excessive heat can make the enzyme structure bend and flex so much that it changes the shape of the active site. This in turn causes substrates to no longer be able to bind to the enzyme as the heat causes the enzyme to denature and the enzyme can’t function as it normally would.
\ Excessive cold - reversible
Excessive cold causes the enzyme to change shape and makes its function slow down or stop. However, it is often reversible, unlike excessive heat.
\ Optimal pH:
Optimal pH is the most suitable level of acidity or alkalinity an enzyme functions most effectively in.
\ Acidic solutions - low pH (below 7)
Alkaline solutions - high pH (above 7)
Neutral solutions - pH of 7
\ Levels of acidity or alkalinity:
Levels of acidity or alkalinity outside the optimum pH for an enzyme can affect it and alter the shape and slow down or stop it from functioning completely.
\ Substrate concentration:
Substrate concentration is the amount and rate of substrate molecules that collide with enzyme molecules.
\ Saturation point:
\ Saturation point is the highest point where enzymes can no longer bind with substrates as all available enzymes are used.
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