4.1 - Enzyme Action Flashcards
Why are enzymes important
Processes necessary to life require chemical reactions that need to happen quickly. Having high temperatures and pressures would not be possible in living cells. Enzymes catalyse the reactions
What are enzymes
Biological catalysts. Globular proteins that interact with substrate molecules causing them to react at much faster rates without the need for harsh environmental conditions.
Anabolic reactions
Synthesis of large polymer based components. Components are synthesised and assembled into cells, which then form tissues, organs and the whole organism. Chemical reactions required for growth that are all catalysed by enzymes
Examples of large polymer based compounds
Cellulose forms the walls of plant cells
Long protein molecules form contractile filaments of muscles in animals
Where are the large organic molecules obtained from?
Digestion of food. From even larger organic molecules e.g. starch. Digestion is also catalysed by enzymes
Vmax
Maximum initial velocity / rate of the enzyme-catalysed reaction
Definition of specificity of an enzyme
Each enzyme catalysed one biochemical reaction, of which here are thousands in any given cell.
Role of enzymes in metabolism
Reactions rarely happen in isolation but as part of multi-step pathways. Metabolism is sum of all the different reactions and reaction pathways in a cell or organism, can only happen as result of control and order imposed by enzymes.
What is needed for a reaction to happen
Molecules need to collide in right orientation.
Factors affecting rate of temp (not enzymes)
Temperature and pressure. Speed of molecules will increase - number of successful collisions and overall rate of reaction
Activation energy
Energy that needs to be supplied for most reactions to start
How do enzymes affect activation energy
Help molecules collide successfully, reducing activation energy needed.
Active site
Area within tertiary structure of enzyme that has a shape that is complementary to shape of a specific substrate molecule
Why is it called lock and key hypothesis
Same way only the right key will fit into a lock, only a specific substrate will fit the active site of an enzyme
Enzyme substrate complex
When substrate is bound to the active site
Enzyme product complex
Products that are formed from substrates reacting in enzyme.
Step after enzyme product complex
Product/s are released, enzyme left unchanged and able to take part in subsequent reactions
How is substrate held in enzyme
Held to enzyme so atom groups can interact. R-groups within the active site of the enzyme will also interact with substrate forming temporary bonds. These put strain on bonds within the substrate which also helps reaction along.
Induced-fit hypothesis
- Active site of enzyme changes shape slightly as substrate enters
- Initial interaction between enzyme and substrate is relatively weak but weak interactions rapidly induce changes in enzymes tertiary structure that strengthen binding, putting strain in substrate molecule - lowers activation energy
Intracellular enzymes
Enzymes that act within cells
Example of an intracellular enzyme
Enzyme catalase ensure hydrogen peroxide (toxic waste product of many metabolic pathways) is broken down to oxygen and water quickly, preventing accumulation. Found in both plant and animal tissues.
Extracellular enzymes
Work outside the cell that made them.
Released from cells to break down large nutrient molecules into smaller molecules in the process of digestion.
Function of extracellular enzymes in single called organisms
Bacteria & yeast release enzymes into their immediate environment. Enzymes break down larger molecules (eg proteins) and the smaller molecules produced (eg amino acids and glucose) are then absorbed by the cells.
Example of extracellular enzymes involved in human digestion
Amylase and trypsin
How do multicellular organisms gain nutrient
Eating food
Why do large molecules of nutrients need to be broken down
So they can be absorbed into the bloodstream
Why are smaller molecules absorbed into the bloodstream
So they can be transported around the body to be used as substrates in cellular reactions
Where does digestion of starch occur
Mouth and small intestine
Why are different enzymes needed in digestion of starch
Each enzyme only catalyses one specific enzyme
Step 1 of starch digestion
Starch particles partially broken down into maltose (disaccharide)
Enzyme is amylase
Where is amylase produced and released
Produced by salivary glands and pancreas
Released into saliva in mouth, and in pancreatic juice in small intestine
2nd step of digestion of starch
Maltose broken down into glucose
(Monosaccharide)
Enzyme maltase
Where is maltase
Small intestine
Why is starch broken down to glucose
Glucose is small enough to be absorbed by cells lining digestive system and subsequently absorbed into bloodstream
What type of enzyme digests proteins
Protease
Type of protease
Trypsin
Function of trypsin
Catalyses digestion of proteins into smaller peptides which can then be broken down into amino acids by other proteases
Where is trypsin produced and released
Produced in pancreas and released into pancreatic juice in small intestine where it acts on proteins
Why are peptides broken down into amino acids
Amino acids that are produced by proteases can be absorbed by the cells lining the digestive system and are absorbed by the bloodstream
