Flashcards
Enzymes: How They Work and What Affects Them
People with lactose intolerance get stomach cramps after drinking milk because their gut makes too little of one enzyme. Which enzyme is it?
lactose
maltase
lactase
lipase
Match each enzyme with the substance it breaks down.
lipase
fats and oils
Match each enzyme with the substance it breaks down.
sucrase
table sugar
Match each enzyme with the substance it breaks down.
protease
gluten in wheat flour
Match each enzyme with the substance it breaks down.
cellulase
cotton and paper fibers
Put the steps of one enzyme reaction in the order they happen.
The enzyme holds the substrate so that its bonds break more easily.
The products are released from the active site.
The substrate is turned into products.
The substrate bumps into the enzyme and slips into the active site.
Put the steps of one enzyme reaction in the order they happen.
1. The substrate bumps into the enzyme and slips into the active site.
2. The enzyme holds the substrate so that its bonds break more easily.
3. The substrate is turned into products.
4. The products are released from the active site.
Based on the graph, what is the optimal temperature for this enzyme?
30°C
25°C
40°C
15°C
True or false?
Food keeps longer in a fridge partly because cold slows down the enzymes that make it spoil.
True or false?
Freezing destroys enzymes, so thawed frozen vegetables have no working enzymes left.
True or false?
A lizard is sluggish on a cold morning partly because the enzymes in its muscles work slowly.
True or false?
Above the optimum temperature, the rate falls more steeply than it rises below the optimum.
Fill in the gaps.
Most human enzymes work best at about
. . . . . °C, while Taq polymerase, taken from bacteria that live in hot springs, works best at about
. . . . . °C .
Most human enzymes work best at about 37 °C, while Taq polymerase, taken from bacteria that live in hot springs, works best at about 72 °C .
Every enzyme has an optimum pH. Why does it stop working when the pH moves far from this value?
The pH changes the charges on its amino acids, so the active site loses its shape.
The cell rewrites the enzyme's amino acid sequence to suit the new pH.
Extra hydrogen ions react with the substrate and use it up before the enzyme can.
The enzyme stops moving, so it can no longer collide with the substrate.
The pH changes the charges on its amino acids, so the active site loses its shape.
A biological laundry detergent contains proteases. Which stains do these enzymes help remove?
red wine
olive oil
blood
egg white
True or false?
At low substrate levels, adding more substrate makes the reaction faster.
True or false?
Once every active site is busy, adding more substrate still makes the reaction faster.
True or false?
With plenty of substrate, doubling the amount of enzyme roughly doubles the reaction rate.
True or false?
As the substrate gets used up, the reaction gradually slows down.
An enzyme speeds up a reaction in a cell. Compared with the same reaction without the enzyme, what stays the same?
the total energy released by the reaction
the energy needed to get the reaction started
the time needed to make the same amount of product
which products are formed
the total energy released by the reaction
which products are formed
Many B vitamins, such as niacin and riboflavin, are needed only in tiny amounts. What does the body use them for?
To protect enzymes from losing their shape in heat.
As fuel that cells burn to release energy.
To make coenzymes, small molecules many enzymes need to work.
As building blocks for the amino acid chains of enzymes.
To make coenzymes, small molecules many enzymes need to work.
In many cells, the final product of a chain of enzyme reactions can bind to the first enzyme in the chain and slow it down. What does this achieve?
The first enzyme switches to making a different product.
The product is turned back into the starting substance for reuse.
The cell does not waste resources making more product than it needs.
The whole chain runs faster, so the product is ready sooner.
The cell does not waste resources making more product than it needs.
Diet sodas carry the warning “Phenylketonurics: contains phenylalanine.” Why must people with phenylketonuria (PKU) limit this amino acid?
They lack a working enzyme that breaks it down, so it builds up to harmful levels.
Their immune system treats it as an allergen and reacts to it.
Their body makes too much of it already, because one enzyme works too fast.
It blocks the active sites of their digestive enzymes, so they cannot digest food.
They lack a working enzyme that breaks it down, so it builds up to harmful levels.
Match each enzyme with its job when a cell copies its DNA.
helicase
pulls apart the two strands
Match each enzyme with its job when a cell copies its DNA.
DNA polymerase
adds nucleotides to build a new strand
Match each enzyme with its job when a cell copies its DNA.
DNA ligase
seals the gaps between pieces of new DNA
True or false?
RuBisCO, which captures carbon dioxide in photosynthesis, is thought to be the most abundant protein on Earth.
True or false?
One molecule of carbonic anhydrase can process about a million substrate molecules per second.
True or false?
Luciferase is the enzyme that makes fireflies glow.
True or false?
Every enzyme works only inside the cell that made it.
The picture shows an enzyme with its substrate bound in the active site. What is this temporary combination called?
coenzyme
polypeptide
enzyme-substrate complex
product