Lesson 12 - Enzymes Flashcards
Why do biological reactions need enzymes?
The high pressures and temperatures needed to increase the speed of chemical reactions can not be attained in cells. This could damage organelles.
Anabolic reactions
Building up / growth
Catabolic
Breaking down releasing energy in metabolic reactions
Where are substrates attained for catabolic reactions?
- Large organic molecules attained from the digestion of food.
Metabolism definition
Sum of all chemical reactions
Enzyme definition
Biological catalyst made of protein
Enzymes can only increase the rate of reaction to a certain point. What is this?
V max
(maximum initial velocity or rate of the enzyme-catalysed reaction)
Phosphorylases
Catalyse the addition of phosphate groups to molecules
Lactate dehydrogenase
Catalyses the transfer of a H+ ion to and from a lactate.
Pepsins catalyse
The breakdown of proteins (peptides) in the stomach
ATPase
Uses ATP as its substrate
When does a chemical reaction occur?
- When molecules collide in the right orientation.
Effect of increasing the temperature and pressure in chemical reactions?
The speed of the molecules will increase, therefore so will the number of successful collisions and the overall rate of reaction.
Specificity of an enzyme
- Living organisms produce thousands of enzymes.
- There are thousands of chemical reactions.
- One enzyme catalyses each chemical reaction.
What is activation energy?
The energy supplied to start a chemical reaction.
How do enzymes reduce the activation energy?
They help the enzymes collide sucessfully
What are the two hypothesis for how enzymes work:
- Lock and Key hypothesis
- Induced fit hypothesis
Lock and key hypothesis:
- An area of the enzymes tertiary structure is complementary to the shape of a specific substrate (the active site).
- When the substrate is bound to the active site and enzyme-substrate complex is formed.
- Reaction occurs and leaves an enzyme-product complex.
- Products are released leaving the enzymes unchanged.
Lock and Key theory: how does the reaction take place?
Enzyme holds substrate in such a way that the right atom-groups are close enough to react.
R-groups within the active site of the enzyme interact with the substrate, forming temporary bonds. These put strain on the bonds in the substrate, helps reaction.
Induced-fit hypothesis:
the active site of the enzyme changes shape to fit the substrate.
- Initial reaction between enzyme and substrate is relatively weak.
- Weak interactions rapidly induce changes in the enzyme’s tertiary structure that strengthen binding, putting strain on the substrate molecule.
- This lowers activation energy for the reaction.
(Modified version of lock and key)
Name of enzymes that act within cells:
Intracellular enzymes
What is hydrogen peroxide?
A toxic product of many metabolic pathways
Which enzyme breaks down hydrogen peroxide? What into?
- Catalyse
- Oxygen and water
Completes the action quickly to prevent the accumulation of hydrogen peroxide.
Where is hydrogen peroxide and catalyse found?
- Plant cells
- Animal cells
What is the first step of all extracellular enzymes?
Released from cells
Purpose of extracellular enzymes?
Break down large nutrient molecules into smaller molecules in the process of digestion. This means that smaller molecules can enter cells directly through the cell surface membrane.
Where do extracellular enzymes work in fungi?
Outside the body.
Who uses extracellular enzymes?
Both single celled organisms and multicellular
Example of single celled organisms use of extracellular enzymes?
Bacteria and yeast
Eg.
- Extracellular enzymes break down proteins into amino acids and glucose. These can be absorbed by cells.
Two enzymes involved in the digestion of starch?
- Amylase and Maltase
- Starch
Role of amylase
Produced by the salivary glands and the pancreas. It is released in saliva into the mouth and pancreatic juice into the small intestine.
Breaks down starch polymers into maltose (disaccharide)
- Starch
Role of maltase
Maltase is in the small intestine.
It breaks down maltose into glucose molecules (monosaccharide)
Starch
- Role of glucose
Small enough to be absorbed by the cells lining in the digestive system and subsequently absorbed into the bloodstream.
What protease is used in the digestion of proteins?
Trypsin
Proteins
Role of trypsin
Produced by pancreas and secreted into the small intestine in the pancreatic juice.
Breaks down proteins into smaller peptides
how are other protease used in digestion of proteins
Other protease break down peptides into amino acids.
Amino acids in digestion?
Small enough to be absorbed into the cells lining in the digestive system and subsequently absorbed into the blood stream.
