T1 - Enzymes Flashcards
What are enzymes
Biological catalysts that increase the rate of a chemcial reaction
What is an advantage of enzymes in the body
Enables cellular reactions to take place at lower temperatures
What is the active site of an enzyme
The region of an enzyme to which a substrate molecule binds and the reaction takes place
How are enzymes ‘high specificity’
Only substrates with a specific, complementary shape can fit into an enzymes active site
Describe the ‘lock and key model’
- Substrate collides with the active site of an enzyme
- Substrate binds, enzyme-substrate complex forms
- Substrate converted to products
- Products released from the active site which is now free to bind to another substrate
What factors affect the rate of an enzyme-controlled reaction
Temperature
PH
Substrate concentration
Explain how increasing temperature initially affects the rate of an enzyme-controlled reaction
- as temperature increases molecules have more KE
- movement of molecules increases
- probability of a succesful collison increases
- more enzyme-substrate complexes form
- rate of reaction increases
Explain how increasing temperature above the optimum affects the rate of an enzyme controlled reaction
- temperature increases above optimum
- increased vibrations break bonds in enzyme’s structure
- active site changes shape, enzyme is denatured
- no more enzyme-substrate complexes can form
- rate of reaction decreases
Explain how PH affects the rate of an enzyme-controlled reaction
- enzymes have an optimum PH
- ph shifts from the optimum
- bonds in the enzyme’s structure are altered
- active site changes shape, enzyme is denatured
- rate of reaction decreases
Explain how the substrate concetration affects the rate of an enzyme-controlled reation
Probaility of succesful collisions increase
Rate of reaction increases
Once all active sites become full, the rate of reaction plateaus
How can the rate of an enzyme-controlled reaction be calculated when given a value for time
Rate = 1/time
What are the units for rate
S^-1
Why must large organic molecules be broken down into smaller, simpler molecules in the body
- large molecules are too big to be absorbed across the surface of the gut wall
- large molecules are broken down into smaller molecules for absorption into the bloodstream
What type of molecules are proteins and carbohydrates
Polymers
What are the monomers of carbohydrates
Simple sugars
Which group of enzymes catalyses the breakdown of carbohydrates
Carbohydrases
Whcih type of carbohydrase catalyses the breakdown of starch
Amylase
What are the monomers of proteins
Amino acids
What typ of enzyme catalyses the breakdown o proteins
Proteases
What is the function of lipases
Enzymes which catalyse the breakdown of lipids into fatty acids and glycerol
Why are small molecules synthesised into larger organic molecules in the body
Large molecules are used for storage (e.g. glycogen) or are used to build structures (e.g organelles)
Which enzyme catalyses the formation of glycogen from glucose
Glycogen synthase
How can the amount of energy contained in food be measured (calories)
Measured using calorimetry
What is calorimetry
A method of measuring the heat transfer during a chemical reaction
Describe the method used to measure the amount of energy in a sample of food
- Add a set volume of water to a boiling tube, record initial temperature
- Record the mass of a sample of food (e.g bean)
- Stick the sample into a mounted needle
- Using a bunsen burner light the food sample
- Hold the sample under the boiling tube until it burns up
- Record the maximum temperature reached by the water
- Record the final mass of a food sample
How can the amount of energy in the food sample be calculated
Energy in food (J)= mass of mater x temperature of water x 4.2
Energy (J/g) = energy in food (J)/mass of food burnt(g)
Compare peanuts to potatoes when meauring their energy
The higher the fat (e.g peanuts) the higher the temperature it will cause the water to go meaning it has more energy than a potato which is high in carbohydrate
