Chapter 4 - Enzymes Flashcards
Define enzymes - short
Biological catalysts
Break down the phrase biological catalyst
Biological’ = they function in living systems
‘Catalysts’ = speed up the rate of chemical reactions without being used up or undergoing permanent change
Define catalyst
speed up the rate of chemical reactions without being used up or undergoing permanent change
Anabolic
Build up
Catabolic
Break down
What do globular proteins have
Complex tertiary structures
What is controlled by enzymes
Metabolic pathways
How are enzymes produced
via protein synthesis inside cells
Types of catalysts - 2
intracellular or extracellular
What are intracellular enzymes
produced and function inside the cell
What are extracellular enzymes
secreted by cells and catalyse reactions outside cells
Examples of extracellular protein
digestive enzymes in the gut
Names example of intracellular protein
Catalase
Function of catalase
- Hydrogen peroxide is produced as a byproduct of many metabolic reaction = harmful to cells.
• Catalase converts hydrogen peroxide into water and oxygen, preventing any damage to cells or tissues.
Named example of extracellular enzymes
Amylase and trypsin
Function of amylase
- Involved in the carb digestion
- hydrolyses starch into simple sugars
is digestions usually carried our by intracellular or extracellular proteins
Extracellular
Why is digestions usually carried our by extracellular proteins
Because macromolecules being digested are too large to enter cell
Where is amylase secreted from
Salivary glands + pancreas
If amylase is secreted from the salivary gland where is it digesting starch
Mouth
If amylase is secreted from the pancreas where is it digesting starch
Small Intestine
Where is trypsin secreted from
Pancreas
Where does trypsin go
Small intestine
Function of trypsin
• Breaks down proteins into peptides + amino acids
Which organisms only use extracellular digestion
Fungi / hyphae
How do some organisms only use extracellular digestion
secrete the necessary enzymes directly onto the food they are consuming (e.g. wood) so that the food is digested into smaller, simple molecules that the fungi can then absorb through the walls of the hyphae
Where do substrates bind on the enzyme
Active site
Main feature of the active site
Specific shape
What does the active site having a specific shape mean
Can only bind to a specific substrate
How can the active site be denatured
PH / temp
How does an enzyme substrate complex form
• substrates collide with enzyme active site
What must happen to form an enzyme substrate complex
must happen at correct orientation + speed for reaction to occur
What is metabolism
sum of all different reactions and reaction pathways happening in a cell or an organism
What is enzyme specificity a result of
complementary nature between shapes
How is the shape of active sister determined by DNA
• shape of active site = determined by complex tertiary structure
o proteins = formed from chains of amino acids
o order of amino acids = determined by DNA
o change DNA / amino acids = change 3D shape
What is an enzyme substrate complex
• forms when an enzyme and substrate join
Key point about enzyme substrate complex
• only formed temporarily before enzyme catalyses reaction + products released
What is an enzyme product complex
• Substrate(s) then react, and product(s) are formed = enzyme-product complex formed.
Define active site
an area within the tertiary structure of the enzyme that has shape which is complementary to shape of a specific substrate molecule.
Describe the lock and key hypothesis
• Like a key, only specific substrate will ‘fit’ the active site of an enzyme = lock and key hypothesis
• When substrate is bound to active site = enzyme-substrate complex formed.
• Substrate(s) then react, and product(s) are formed = enzyme-product complex formed.
• Products then released, enzyme is left unchanged, able to take part in subsequent reactions.
How are substrates held in enzymes
In a way that right atom-groups are close enough to react.
How do R groups interact with enzyme
• R-groups within active site of enzyme also interact with substrate → temporary bonds
• Put strain on bonds within substrate – helps reaction along
Describe the induced fit hypothesis
• Active site of enzyme changes shape slightly as substrate enters.
• Initial interaction between enzyme and substrate – relatively weak, but these weak interactions rapidly induce changes in enzymes tertiary structure that strengthen bonding = putting strain on substrate molecule
• This can weaken a particular bond(s) in substrate, lowering activation energy needed for reaction.
What are the changes in induced fit called
Conformational changes
Define activation energy
Minimum amount of energy required to start a reaction
How do enzymes speed up chemicals reactions
reduce the stability of bonds in the reactants
o The destabilisation of bonds in the substrate makes it more reactive
How to enzymes work
providing an alternative energy pathway with a lower activation energy
How do enzymes help organisms
• Without enzymes, extremely high temperatures or pressures would be needed to reach the activation energy for many biological reactions
o Enzymes avoid the need for these extreme conditions(that would otherwise kill cells)
How does changing the pH denature an enzyme
o Hydrogen and ionic bonds hold the tertiary structure of the protein (ie. the enzyme) together
o Below and above the optimum pH of an enzyme, solutions with an excess of H+ ions (acidic solutions) and OH- ions (alkaline solutions) can cause these bonds to break
o The breaking of bonds alters the shape of the active site, which means enzyme-substrate complexes form less easily
o Eventually, enzyme-substrate compl exes can no longer form at all
o At this point, complete denaturation of the enzyme has occurred
What holds the tertiary structure together in enzyme
o Hydrogen and ionic bonds
What does the location of an enzyme indicate
It’s optimum environment
Where is pepsin found
Stomach
What does pepsin being found in the stomach indicate
Suited to an acidic environment at pH 2
Why does the stomach have a pH of 2
due to the presence of hydrochloric acid in the stomach’s gastric juice
What are buffer solutions
Solution = Have a specific pH
Purpose of buffer solutions
maintain pH through reaction