1.6 Cell Metabolism Flashcards
Definition of cell metabolism
All the enzyme controlled reactionsthat occur in a cell at the same time
The two groups that reactions in a cell can be categorised into
- Catabolic
* Anabolic
Explain an anabolic pathway
- Requires energy
* Involves biosynthetic processes (large molecules synthesised from small molecules)
Explain a catabolic pathway
- Releases energy
* Involves the breakdown of large molecules into smaller molecules
An example of a catabolic reaction
Aerobic respiration
An example of an anabolic pathway
Protein synthesis
Definition of a metabolic pathway
A series of chemical reactions that follow on, one after the other
What each stage in a metabolic pathway is controlled by
Enzymes
Example of a reversible metabolic pathway
The conversion of pyruvate into lactic acid in animal cells
Example of an irreversible metabolic reaction
The conversion of pyruvate into ethanol and CO2 in plant cells
What alternative routes do in metabolic reactions
Bypass steps in a pathways
The two ways metabolic pathway can be controlled
- the presence or absence of particular enzymes in the pathway
- regulation of the rate of reaction of key enzymes within the pathway
The result of the genes for some enzymes being continuously expressed
- the enzymes are always present in the cell
* their control involves the regulation of their rate of reaction
The two molecules regulation of rate of reaction is controlled by
- intracellular
* extracellular
Describe the work of extracellular signal molecules
Secreted by a particular cell but work elsewhere in the body
Example of extracted signal molecules
Hormones which travel in the bloodstream to reach target tissues
eg. Insulin produced in the pancreas works on the liver
Describe the work of intracellular signal molecules
Work inside the cell that produces them
Where enzymes are found
Every living cell
What an enzyme is
Biological catalysts made of protein
What would happen if enzymes weren’t present in cells
Chemical reactions would occur in cells to slowly for life to exist
What activation energy is
The energy needed to start a reaction
Basic work of enzymes
Enzymes lower the activation energy needed to start a chemical reaction
Symbol for activation energy
Ea
Define what is ment by affinity
The active site having a chemical attraction to the substrate
Explain the meaning of induced fit
- structural changes occur so that the active site fits precisely around the substrate
- the substrate induces the active site to change shape
How enzymes reduce the activation energy required for the reaction to occur
Orientating and then holding the reactants close together
Why the end products are released from the enzyme
The end products have a lower affinity for the active site
What the direction and speed of an enzyme controlled reaction are controlled by
The concentrations of both the substrate and the end product
In what direction does the increase in the substrate concentration drive to the reaction in
In the direction of the end product
What drives a sequence of reactions in a particular direction
- presence of a substrate
* removal of a product
What happens when enzymes act in groups
The product of one reaction acts as a substrate for the next
What is ment by multi enzyme complexes
Where a number of enzymes work together at the same time on the same substrate molecule
An example of a multi enzyme complex
DNA polymerase and RNA polymerase both working on a strand of DNA
What an enzyme needs to function effectively
- suitable temperature
- appropriate pH
- adequate supply of substrate molecules
Effects of inhibitors on the rate of reactions
- slow the rate of reaction down
* bring the reaction to a halt
What happens when the genes responsible for the production of some enzymes are continuously expressed
The enzymes are always present in the cell
How enzyme activity can be controlled
Regulation of the rate of reaction that the enzymes catalyse
Explain the term enzyme inhibitor
- molecule that can affect the rate of reaction
- does this by blocking the active site of the enzyme
- or denaturing the enzyme
Role of a competitive inhibitor
- competes with the substrate for the active site
* resembles the shape of the substrate
How the effect of competitive inhibition can be reversed
By increasing the concentration of the substrate molecules so there is more of a chance that the substrate molecules occupy the active sites
Effect of non competitive inhibition
Changed the shape of the active site on an enzyme
How a non competitive inhibitor works
Binds to an area of the enzyme which is not the active site
